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  20 December 2024, Volume 48 Issue 6 Previous Issue   
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2D/3D electrical exploration based on borrowing-line telecontrol electrode arrays
GE Wei-Zhong, LIANG Bing-He, GAO Jian-Dong, Lv Yu-Zeng, CHEN Long
Geophysical and Geochemical Exploration. 2024, 48 (6): 1437-1447.   DOI: 10.11720/wtyht.2024.0170
Abstract   HTML ( 4 )   PDF (3061KB)

The telecontrol electrode array is a new type of electrode array for power supply and observations that utilizes the carrier waves of the power-supply and measurement wires used in conventional electrical prospecting to transmit signals. By remotely controlling a series of coded electrode switches between various wires and their connections, this array allows for orderly power supply and measurements. This array enables flexible spacings between electrodes and the gradual expansion of the distances between power supply electrodes via remote control, thus achieving a gradient-based sounding array. The borrowing-line remote controller can be used combined with single-channel, multi-channel, and high-density resistivity instruments, and the combined arrays can perform 2D/3D electrical prospecting more effectively. Followed by the brief introduction of the principle of the borrowed-line telecontrol electrode array, this study discusses the applications and examples of this array and several combined arrays in the resistivity method and induced polarization (IP).

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Marine controlled-source electromagnetics-based technology for generating arbitrary-frequency waveforms
WANG Jie, WANG Meng, REN Zhi-Bin, WANG Chen-Tao, WANG Hui-Min
Geophysical and Geochemical Exploration. 2024, 48 (6): 1448-1454.   DOI: 10.11720/wtyht.2024.0165
Abstract   HTML ( 1 )   PDF (2713KB)

Marine controlled-source electromagnetics (MCSEM) is used to explore resources such as oil and gas hydrates, as well as deep geological structures, by revealing resistivity differences below the seabed. Different excitation frequencies correspond to varying detection depths. To enhance the resistivity imaging of targets beneath the seabed, this study investigated the MCSEM-based technology for generating arbitrary-frequency waveforms to flexibly alter the excitation frequency and improve the exploration effectiveness and efficiency. Using the direct digital frequency synthesis (DDS) chip AD9833 and the joint control of a microcontroller and a complex programmable logic device (CPLD), this study achieved the generation of arbitrary-frequency waveforms with limited precision. The test results indicate that this technology can effectively enhance the spectral adaptability and flexibility of MCSEM.

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Development and sea trials of a marine towed geomagnetic vector measurement system
LUO Jian-Gang, LI Hai-Hu, LIU Jing-Xiao, LI Hai-Bing, GUO Zi-Wei, SUN Ning, FU Bi-Bo, ZHANG Feng, LI Xue-Yan
Geophysical and Geochemical Exploration. 2024, 48 (6): 1455-1462.   DOI: 10.11720/wtyht.2024.0155
Abstract   HTML ( 2 )   PDF (3254KB)

The geomagnetic field is a vector field in space. However, traditional marine magnetic surveys focus on geomagnetic field intensity, failing to fully acquire and utilize rich information about the geomagnetic vector field. Given this, this study developed a towed marine geomagnetic vector measurement system. This system was designed to operate in dynamic marine conditions and ultimately acquire geomagnetic vector field data within the geographical coordinate system. Through sea trials of the system, grid line and repeat line measurements were obtained. After preprocessing the collected data, the measurement accuracy of repeat lines and crosspoints was better than 6.7 nT and 6 nT, respectively. The results of the sea test indicate that the measurement system has the preliminary ability to measure the geomagnetic vector field at sea, and it can be applied to geomagnetic field measurement tasks near or far sea, obtaining richer geomagnetic field information.

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R&D and tests of a graphene-based electric field sensor
KANG Li-Li, YANG Yong-You, WANG Zhong-Xing, CHEN Kai, HE Peng, WANG Xu-Zhe, DING Gu-Qiao, LI Zi-Hang
Geophysical and Geochemical Exploration. 2024, 48 (6): 1463-1470.   DOI: 10.11720/wtyht.2024.0152
Abstract   HTML ( 1 )   PDF (5234KB)

This study aims to enhance the measurement accuracy of the electric field by reducing the range shifting and background noise of electric field sensors in the electromagnetic detection system. First, it ascertained the design requirements of electric field sensors by investigating the mechanisms of the range drift and background noise. Second, it established the Ag-AgCl-based preparation process for graphene-based stable electrolyte gel. Third, it optimized the multi-cell multi-contactor electrode structure based on polymeric microporous membranes. Finally, it developed a graphene-based electric field sensor characterized by low range drift and background noise. This sensor can retard internal ion diffusion by leveraging the ion retention ability of graphene and the multi-cell structure composed of reaction, transition, and buffer zones. Consequently, the range drift caused by changes in the ion concentration is reduced. The internal and contact resistance of this sensor can be reduced through the conductive ability of graphene and the enhanced contact with the ground via multiple contactors, respectively, thereby reducing the sensor's background noise. The graphene-based electric field sensor developed in this study shows range drift not exceeding 20 μV/24 h, and background noise not above 25 nV/√Hz. This sensor was applied to a 24 h field magnetotelluric sounding test conducted in the Duobaoshan area, Heilongjiang Province, yielding high-quality electric field data in the frequency band of 0.000 125~320 Hz, with the apparent resistivity phase curve aligning with the result of commercial electrodes. Therefore, the graphene-based electric field sensor proves effective in fieldwork.

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Development of a nodal rotational seismometer with a micro-electro-mechanical system sensor and testing of H/V spectral ratios
JIA Song, HE Zhan-Xiang, YANG Hui, YAO Yong-Chao, WANG Cai-Xia
Geophysical and Geochemical Exploration. 2024, 48 (6): 1471-1478.   DOI: 10.11720/wtyht.2024.0140
Abstract   HTML ( 2 )   PDF (3283KB)

In response to the increasing demand for large-scale field seismic acquisition, this study developed a low-cost multifunctional nodal rotational seismometer (RBWL) with a micro-electro-mechanical system (MEMS) sensor, considering the functionality, economic feasibility, and the ease of arrangement. The RBWL employs a low-cost and low-power MEMS sensor to acquire seismic signals, involving three-component translational motions (Tx,Ty,Tz) and three-component rotational motions (Rx,Ry,Rz). To reduce the impacts of environmental factors on measurements, the system of the RBWL automatically records real-time information including temperature and attitude while performing compensation correction on the measurement results. For real-time monitoring and data transmission at acquisition nodes, the system establishes a data transmission link integrating 4G, cloud, and client, with the measured maximum data transmission rate up to 100 Mbps. The testing of H/V spectral ratios verifies the system functions and principal performance parameters of the RBWL and its effectiveness in engineering physical exploration.

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Portable opposing-coils transient electromagnetic system and its application tests
ZHOU Sheng, CHEN Xing-Peng, WANG Jun, QI Qing-Xin, ZHANG Zhi-Qing, PAN Ji-Min, XI Zhen-Zhu, YANG Chun-Hua
Geophysical and Geochemical Exploration. 2024, 48 (6): 1479-1485.   DOI: 10.11720/wtyht.2024.0169
Abstract   HTML ( 1 )   PDF (4415KB)

In shallow engineering investigations, the small-loop transient electromagnetic (TEM) system is challenged by limitations such as overweight equipment, significant transmitter-receiver mutual inductance, and high manpower requirements. Hence, this study introduced an improved system. Based on the opposing-coils transient electromagnetic (OCTEM) theory, this study calculated the magnetic field distribution of the generalized opposing-coils antenna device. Furthermore, it designed and developed efficient portable antennas and the supporting system (collectively referred to as the portable OCTEM system). Subsequent field experiments demonstrate that while ensuring exploration accuracy, the portable OCTEM system can enhance the investigation efficiency by effectively mitigating the transmitter-receiver mutual inductance and significantly reducing manpower requirements. This study preliminarily verifies the feasibility of the portable OCTEM system, providing a novel technology route for developing downsized shallow exploration equipment.

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Active/passive source-based observation experiments and applications of fiber-optic rotational seismometers
CAO Yu-Jia, CHEN Yan-Jun, LI Zheng-Bin, TENG Yun-Tian, ZHANG Ding-Fan
Geophysical and Geochemical Exploration. 2024, 48 (6): 1486-1497.   DOI: 10.11720/wtyht.2024.0142
Abstract   HTML ( 1 )   PDF (9597KB)

In the past two decades, high-sensitivity ring laser gyroscopes have demonstrated the potential of rotational observation data in global seismology. Commercial fiber-optic three-component rotational seismometers have heralded a new development phase of rotational seismography. Field experiments for high-sensitivity portable fiber-optic rotational seismometers in China remain in the initial stage, whereas their relevant data analysis results have been obtained internationally. This study elucidated the co-located observation experiments on six components (6C, including three components of translational motions and three components of rotational motions) of an active source and a natural earthquake, involving experimental schemes, implementation steps, and subsequent data analysis. Moreover, this study revealed the primary factors influencing the experiment results by comparatively analyzing the similarities and differences of experiments. Fiber-optic rotational and conventional seismometers need to be fixed on the same rigid panel to ensure the consistency of received signals. Besides, proper ground coupling and burial processing contribute to high-quality experimental data. The experimental results indicate that water bodies will affect surface wave manifestation and P-wave clarity. These findings, enriching the practical experience in seismic rotational observation experiments, serve as a reference for the design of subsequent rotational observation experiments, thereby assisting in completing the experiments and obtaining higher-quality data. In terms of data application, this study optimized and substantiated the feasibility of the preprocessing scheme, with the backazimuth calculation accuracy improved by 58.8° and 50° at the two active-source measuring points, and by 24.1° and 29.4° at the two passive-source measuring points. The application of six-component seismic data from a single seismic station suggests that additional observation of rotational components can acquire more seismic wavefield information, thus the observation of rotational components can be employed to enhance the utilization of China's massive seismic observation data. Overall, fiber-optic rotational seismometers broaden the boundary of seismic monitoring technology, boost seismology research, and create new possibilities for future earthquake research.

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Development of a submarine optically pumped magnetometer
GONG Yi-Xuan, JIANG Kai, GAO Jing-Yu, ZHU Wan-Hua, CHEN Kai
Geophysical and Geochemical Exploration. 2024, 48 (6): 1498-1506.   DOI: 10.11720/wtyht.2024.0144
Abstract   HTML ( 2 )   PDF (4010KB)

The Autonomous Underwater Vehicle (AUV) equipped with a magnetometer conducts underwater magnetic anomaly detection, enabling long-duration and large-scale continuous sampling. It offers advantages such as concealment, high efficiency, high practicality, wide application range, strong maneuverability, and robust endurance. To improve measurement accuracy, synchronous seabed magnetic field data is needed as a reference to counteract environmental magnetic noise. To address this, a submarine optically pumped magnetometer was developed to provide a reference for processing AUV magnetic anomaly detection data.The submarine optically pumped magnetometer consists of a magnetic field measurement unit and an acoustic release unit, capable of high-precision autonomous acquisition of the total magnetic field on the seabed, as well as underwater acoustic release and recovery. The magnetic field measurement unit includes an optical pumping probe, electronic unit, counter, battery pack, and nylon pressure chamber. The acoustic release unit includes an acoustic transducer, acoustic communication board, electro-corrosion decoupler, cement block, buoyancy block, and frame. This design addresses key technical challenges such as miniaturization, autonomous acquisition, and underwater acoustic communication.In 2022, a magnetic anomaly detection test was conducted in the offshore waters of Qingdao. The test results verified the autonomous seabed magnetic field acquisition and the release and recovery functions of the submarine optically pumped magnetometer, providing effective reference data for underwater target detection.

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Definition, classification, and functions of underground research laboratories for the geological disposal of high-level radioactive waste and the scientific research plan of Beishan underground research laboratory
WANG Ju, LUN Long
Geophysical and Geochemical Exploration. 2024, 48 (6): 1507-1518.   DOI: 10.11720/wtyht.2024.1556
Abstract   HTML ( 1 )   PDF (8255KB)

Underground research laboratories (URLs) for the geological disposal of high-level radioactive waste serve as critical facilities for verifying the safety and suitability of the sites of potential disposal repositories and for developing disposal technologies. URLs are irreplaceable in many aspects such as the siting and system design of potential disposal repositories, the development of the theories and technologies for disposal engineering, the safety and characteristic assessments, full-scale field tests, and on-site demonstration. This study highlights the definition, classification, and functions of URLs and categorizes existing primary URLs both in China and abroad. URLs are generally categorized into general URLs (first generation) and site-specific URLs (second generation). The construction of disposal repositories in China has progressed from national, regional, and site screening to site evaluation and to URL construction. The authors of this study proposed the concepts of "site-specific URLs" and "third-generation URLs" in 2010 and 2014, respectively. Furthermore, the Beishan URL-the world's first site-specific URL for the geological disposal of high-level radioactive waste-has been built. This study introduces the siting process, planning, positioning, and functions of the Beishan URL, as well as the functions of primary scientific experiments and main field experiments conducted during its construction. The results of this study serve as a guide for future siting and R&D of disposal repositories.

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Seismic response characteristics of the cavern group of the Beishan underground research laboratory for the geological disposal of high-level radioactive waste
YUN Long, CHEN Su, FU Lei, ZHUANG Hai-Yang, WANG Ju
Geophysical and Geochemical Exploration. 2024, 48 (6): 1519-1529.   DOI: 10.11720/wtyht.2024.1555
Abstract   HTML ( 1 )   PDF (10124KB)

The Hexi Corridor and northern Qilian region, adjacent to the Beishan underground research laboratory (URL) for the geological disposal of high-level radioactive waste, exhibit complex seismic environments characterized by frequent strong earthquakes. The Beishan URL, featuring a complex underground structure consisting of three vertical shafts and a spiral ramp, displays significant large-scale spatial distribution characteristics. Investigating the seismic response characteristics of the underground structure group holds great engineering significance for the subsequent assessment of crustal stability at the site. Based on the design of the URL, along with existing physical and mechanical parameters of surrounding rocks, this study established a fine-scale three-dimensional finite element model of the rock mass-underground structure system. Using this model, this study investigated the impacts of key faults on the near-field seismic safety of the URL. The results indicate that traditional seismic attenuation relationships are difficult to consider near-source effects, such as finite fault effects, fracturing directivity effects, and hanging wall effects. In contrast, the stochastic finite-fault method can effectively consider these near-field ground shaking characteristics. The target site exhibits hard granite bedrock, and the response spectra of the earthquakes induced by near-field seismogenic faults, received at the site, display pronounced high-frequency components. Furthermore, the ground shaking of the underground cavern group, caused by the irregular structure of the URL, presents significant spatial variability, with the rock mass softening zone exhibiting a notable accumulation of peak ground acceleration. This zone should be avoided in engineering applications. This study offers a basis for seismic safety analysis for the future site selection and evaluation of the disposal repositories of high-level radioactive waste.

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A method for identifying anomalous values of groundwater levels at candidate sites for the geological disposal of high-level radioactive waste
JI Zi-Jian, Zhou Zhi-Chao, Zhao Jing-Bo, JI Rui-Li, ZHANG Ming
Geophysical and Geochemical Exploration. 2024, 48 (6): 1530-1538.   DOI: 10.11720/wtyht.2024.1554
Abstract   HTML ( 1 )   PDF (4833KB)

Dynamic groundwater monitoring provides critical foundational data for the safety assessment of candidate sites for the geological disposal of high-level radioactive waste. However, research has revealed that actual monitoring data frequently contain numerous anomalous values, severely interfering with the accurate assessment of the dynamic monitoring process. Therefore, there is an urgent need to develop an efficient method to accurately identify these anomalous values. This study built a combined model for anomalous value detection of the groundwater level using local weighted regression-based time series decomposition and the minimum covariance determinant (MCD) method. This combined model allowed the MCD method to achieve anomaly detection in more independent residuals. Results indicate that the combined model exhibited higher sensitivity and detection accuracy for anomalous data than the single MCD model. Furthermore, this study established that the threshold of the combined model should be close to the actual proportion of anomalous values to achieve optimal detection results. Besides, this study validated the applicability of the combined model using groundwater level data from boreholes BSQ01, BSQ25, BS35, and BS26 at the new site. The validation results demonstrate that the combined model can accurately identify anomalous values amidst a large volume of data on the normal groundwater level and is applicable to the detection of different types of anomalous events.

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Creep characteristics of fractured Beishan granite under the condition of multi-field coupling
ZHANG Hai-Yang, LIU Fei-Yang, LIU Jian
Geophysical and Geochemical Exploration. 2024, 48 (6): 1539-1544.   DOI: 10.11720/wtyht.2024.1557
Abstract   HTML ( 1 )   PDF (2483KB)

After a disposal repository for high-level radioactive waste operates, the near-field surrounding rocks will be long in a thermal-hydrological-mechanical coupling environment. Therefore, their mechanical and permeability characteristics are crucial to the performance evaluation of the disposal repository. The surrounding rocks of the Beishan preselected area for the disposal of high-level radioactive waste in China are typical sparsely fractured granites, whose creep characteristics are directly related to the long-term safety of the disposal repository. Using water jet and wire cutting techniques, along with fracture surface blocking and combined sealing at rock sample ends, this study addressed the challenges of the sample preparation and sealing of fractured granite in thermal-hydrological-mechanical coupling triaxial tests. Based on this, multi-loading triaxial creep tests were conducted. The test results indicate that under the condition of multi-field coupling, the triaxial creep strength of the fractured granite was approximately 80% of its triaxial strength. Creep deformation increased with the axial load level, with lateral creeps more pronounced than axial creeps. For the compacted and crack propagation sections of the rock samples, both the axial strain rate and permeability decreased initially and then increased. In the case of consistent osmotic pressure difference, a higher osmotic water pressure within fractures would lead to decreased peak strength of the rock samples and result in greater lateral creep deformation.The results provide scientific support for the site selection, surrounding rock evaluation, engineering design and construction of the repository.

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Tunnel-scale evaluation of rock mass suitability for the disposal of high-level radioactive waste
YE Yong, CHEN Liang, LIU Jian
Geophysical and Geochemical Exploration. 2024, 48 (6): 1545-1552.   DOI: 10.11720/wtyht.2024.1553
Abstract   HTML ( 1 )   PDF (2325KB)

Rock mass suitability evaluation is a core part of the siting and design of a disposal repository for high-level radioactive waste, aiming to determine whether the rock masses at the site meet the functional requirements for long-term containment and radionuclides isolation. Based on the previously proposed site-scale evaluation method (QHLW) of rock mass suitability, this study further developed criteria for the tunnel-scale evaluation of rock mass suitability and established a two-phase evaluation system consisting of pre-evaluation and final evaluation. Additionally, in combination with geological and hydrological data revealed by demonstration tunnel 1 (DT1) at the site of the ONKALO underground research laboratory in Finland, this study tested and verified the criteria of the two-phase evaluation system on the disposal tunnel scale. The comparison between the suitability evaluation results obtained using the optimized QHLW and the qualitative evaluation results determined using the rock suitability classification (RSC) rock mass grading method indicates that both methods yielded roughly consistent results. This confirms the feasibility of the tunnel-scale evaluation method of rock mass suitability.

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Study on avoidance distance between deposition hole and water conducting fracture
LING Hui, LI Ya-Wei, CHEN Wei-Ming
Geophysical and Geochemical Exploration. 2024, 48 (6): 1553-1558.   DOI: 10.11720/wtyht.2024.0040
Abstract   HTML ( 1 )   PDF (1811KB)

The definition of avoidance distance between deposition hole and water conducting fracture is an important basis for evaluating the site suitability of the high-level waste disposal repository,and it is also one of the key contents of the design of high-level waste disposal repository. In this paper, the site of the Beishan underground research laboratory is taken as the reference site for geological disposal of high-level radioactive waste. This paper established a computational model for the release and migration of radionuclides after closure of repository by GoldSim. Then, the avoidance distance between deposition hole and water conducting fracture in intact rock was analyzed by the method of Monte Carlo stochastic simulation. The results show that a 80% hydraulic conductivity value of the granite in the study area is less than 1.0×10-9 m/s under the existing conditions, and when the hydraulic conductivity value of water conduction fracture is set to 1.0×10-6 m/s, the corresponding avoidance distance is less than 0.5 m. The smaller the permeability coefficient is, the smaller the corresponding safety avoidance distance is. The analysis of the results shows that the avoidance distance between the deposition hole and water conducting fracture can provide a feedback guidance for the site selection and design of the disposal repository.

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Design and application of the dynamic management system for scientific data of the Beishan underground research laboratory
MA Ming-Qing, CHEN Liang, WANG Ju, LI Xiao-Jun, ZHANG Zhi-Wei, LING Hui
Geophysical and Geochemical Exploration. 2024, 48 (6): 1559-1567.   DOI: 10.11720/wtyht.2024.0017
Abstract   HTML ( 1 )   PDF (4462KB)

The construction of the Beishan underground research laboratory (URL) is a key initiative under China's 13th Five-Year Plan. During the construction and operation of the URL, extensive scientific data will be generated in field experiments. To ensure the integrity, reliability, authenticity, and traceability of these data and to ensure that researchers can manage and utilize various types of data in an efficient and convenient manner, it is necessary to develop a dynamic management system tailored for the scientific data of the URL. The purpose is to provide data support and a decision-making basis for the R&D of disposal engineering technologies and safety assessments. This study introduces the background and overall requirements for the development of the scientific data dynamic management system for the Beishan URL, proposes a general design scheme, and provides a comprehensive overview of the system's functional architecture and content. The system is primarily composed of modules for system management, system status management, basic data management, metadata management, experimental information management, experimental data management, data quality management, and data visualization. This system has been preliminarily applied to the management of field experimental processes and data for the Beishan URL, yielding encouraging results.

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Study on deep geological environmental characteristics of the Shazaoyuan area
LUO Hui, CHEN Wei-Ming, LI Ya-Wei, TIAN Xiao, ZHANG Jing-Jia
Geophysical and Geochemical Exploration. 2024, 48 (6): 1568-1576.   DOI: 10.11720/wtyht.2024.0416
Abstract   HTML ( 1 )   PDF (4820KB)

Through surface geological surveys, geophysical measurements, borehole investigations, and 3D geological modeling, the deep geological environment of the Shazaoyuan area has been studied. The lithology, structural spatial distribution, rock integrity at depth, and engineering geological characteristics of the Shazaoyuan area have been preliminarily identified. The main findings are as follows: The granite rock mass in the Shazaoyuan area has a large exposed surface, with relatively uniform lithology, primarily composed of biotite granodiorite of the Shazaoyuan superunit, covering an area of about 330 km2. The granite body dips outward and extends to a depth greater than 2 km. There are 12 faults developed in three main orientations: North-northwest, near north-south, and northeast, all with steep dips and intersecting the rock mass. Fractures are well developed in the deep part of the granite, mostly with steep dips and filled with minerals such as calcite and clay. Preliminary delineation has identified more than two favorable rock masses in the pre-selected Shazaoyuan area, which may serve as potential candidate sites for high-level radioactive waste disposal facilities.Though the research,it is proved that the Shazaoyan area has favorable geological conditions for screening the high-level waste disposal bank.

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Geochemical characteristics and sedimentary environment of coal seams in the Yimin Formation in the Yimin Basin
Li Bin, Zhang Yue-Heng, Hong Lian-Han, Yuan Jing-Yi, Gao Ting, Dong Zhen-Guo
Geophysical and Geochemical Exploration. 2024, 48 (6): 1577-1587.   DOI: 10.11720/wtyht.2024.1360
Abstract   HTML ( 1 )   PDF (2600KB)

The Yimin Formation hosts shallow and stable coal seams, which are rich in coal resources and suitable for open-pit mining. To ascertain the distributions of coal seams in the Yimin Formation and reveal the coal accumulation patterns, it holds critical geological significance to identify the provenance setting and coal-forming environment using geochemical methods. This study systematically collected coal samples from drilling cores in the study area for testing and analysis of coal quality.Furthermore, this study reconstructed the paleogeographic information and sedimentary environment during the formation of coal seams for comprehensive research. The results show that:(1) The coal seams of the Yimin Formation are primarily composed of lignite, with durain being the dominant component, followed by fusain. Their coal samples exhibited average vitrinite reflectance (R0) of 0.37%, average oil content of 7.66% in raw coal, and average total sulfur content of 1.32%; (2) The average CIA value of 58.45 suggests that the source area experienced primary to moderate weathering. The average w(Si)/w(Al) ratio of 2.72 indicates that minerals in the coal originated from terrestrial argillaceous sediments. The ash index (K) of 0.34 implies that the coal seams formed in a low-level peat swamp environment. The w(Sr)/w(Cu), w(Sr)/w(Ba), w(Mg)/w(Al) (m), and w(Ca)/w(Fe) (n) ratios signify warm and humid paleoclimate, significant evaporation, and high salinity of ancient water bodies during the coal seam sedimentation stage. The Sr, Ba, and w(Ba)/w(Ga) values denote that the coal seams resulted from continental sedimentation. The w(V)/[w(V)+w(Ni)], w(V)/w(Cr), w(Ni)/w(Co), and w(V)/w(Sc) ratios demonstrate that the coal seams formed under anoxic reducing conditions. This study posited that the early sedimentary stage of the Yimin Formation saw the reduced continental faulted basin, humid climate, and lake siltation, forming a peat swamp environment in the deltaic plain, thus creating favorable conditions for coal generation and accumulation.

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Strike-slip fault system in the Erbatai area, Tarim Basin
ZHANG Jia-Chang, LI Tao, LIANG Hong-Gang, FEI E, SUN Zhi-Yuan, YUE Tong
Geophysical and Geochemical Exploration. 2024, 48 (6): 1588-1598.   DOI: 10.11720/wtyht.2024.0015
Abstract   HTML ( 1 )   PDF (11103KB)

In structural confirmation for oil and gas exploration, ascertaining the distributions of faults remains a challenge and priority in seismic data interpretation. The most complex fault combinations can be observed in strike-slip fault systems. This study investigated the Erbatai area that hosts a complex Luntai strike-slip fault system in the Tarim Basin. First, the background noise was reduced using the dip angle plus azimuth scanning and the structure-oriented filtering. Then, a multi-level nesting technology was developed by integrating attributes like coherence cube, ant-tracking attribute, and maximum likelihood. Using the technology, this study identified and statistically analyzed 41 faults in the Erbatai area for their geometric development characteristics, including strike, dip, dip angle, and fault throw. Furthermore, this study determined the complex fault combinations within the strike-slip fault system. The findings indicate that the Erbatai area develops a dominant nearly EW-trending strike-slip fault zone and a NE-trending secondary fault zone. These faults are extensional fractures caused by left-lateral torsion, manifested as right-stepping en echelon normal faults. Overall, this study can be referenced for assessing structural hydrocarbon reservoirs in the Erbatai area.

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Advances and performance of seismic exploration experiments in the western Yin'e Basin
WANG Xing-Yu, LIU Yan-Li, WANG Tong, RONG Li-Xin
Geophysical and Geochemical Exploration. 2024, 48 (6): 1599-1608.   DOI: 10.11720/wtyht.2024.1507
Abstract   HTML ( 2 )   PDF (15587KB)

This study aims to improve the seismic exploration effects in the Upper Paleozoic strata of the Yin'e Basin.With the Juyanhai depression in the western Yin'e Basin as an experimental area,it investigated the previous seismic acquisition characteristics and current data processing techniques of the area.Through field seismic acquisition experiments and data processing research in the laboratory,it explored and summarized the seismic exploration techniques for the Upper Paleozoic strata in the Yin'e Basin.Key findings are as follows:(1)The combination of shot holes and seismic vibrators is recommended for seismic excitation in the area according to local conditions;(2)The receiving array length takes precedence over the receiving density;(3)Targeted processing techniques including anisotropy processing,spectral-constrained deconvolution,and wedge transform adaptive denoising can effectively improve the quality of deep seismic imaging.This study provides a reference for relevant research in similar areas.

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Application of wide-field electromagnetic sounding method to deep prospecting in the Mangling ore concentration area in North Qinling: A case study of the Yaozhuang ore district
ZHANG Xiao-Tuan, LI Xin-Lin, ZHOU Bin, GAO Wei-Qiang
Geophysical and Geochemical Exploration. 2024, 48 (6): 1609-1617.   DOI: 10.11720/wtyht.2024.0056
Abstract   HTML ( 3 )   PDF (6000KB)

The Mangling ore concentration area with intense magmatic activity has become a focal area for deep prospecting in the North Qinling tectonic belt in recent years. The formation of molybdenum deposits in this area is closely related to small Late Jurassic acidic intrusions. To achieve breakthroughs in deep ore prospection within this area, this study conducted the wide-field electromagnetic sounding over the concealed Yaozhuang intrusion delineated based on gravity anomalies. The results indicate the presence of pronounced high-resistivity anomalies at depth, and it is inferred that the protruding part of the anomalies corresponds to the concealed Yaozhuang intrusion. The resistivity inversion results roughly delineated the variations in the top surface of the intrusion, with the elevations and N-S width of the top surface estimated at -300~620 m and 1300~1600 m, respectively. Drilling in the most favorable deep mineralized part confirmed the presence of the concealed intrusion and concealed molybdenum ore bodies. The results of this study demonstrate that the wide-field electromagnetic sounding method exhibits great sounding depths and high resolutions, serving as an effective method for deep ore prospecting in the Mangling ore concentration area.

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Cepstrum decomposition of seismic signals and its application in hydrocarbon detection of ultradeep carbonate reservoirs
ZHANG Yong-Sheng, HUANG Chao, LIU Jun, ZHANG Yong-Heng, WANG Xing-Jian, XUE Ya-Juan
Geophysical and Geochemical Exploration. 2024, 48 (6): 1618-1625.   DOI: 10.11720/wtyht.2024.1481
Abstract   HTML ( 1 )   PDF (5594KB)

The cepstrum decomposition technology for seismic signals,recently developed for hydrocarbon detection,can highlight weak fluid information in some specific frequency bands of broadband seismic signals.This study explored the cepstrum decomposition technology for seismic signals using Fourier transform(FT)- and wavelet packet transform (WPT)-based cepstrum.Moreover,the technology was applied to the ultradeep carbonate reservoirs in the Shunbei area for hydrocarbon detection.A comparative analysis was conducted on the characteristics of common cepstrum profiles and conventional common frequency profiles.Furthermore,a detailed comparative analysis was conducted on the characteristics of the first- and second-order common cepstrum profiles of FT- and WPT-based cepstra.On this basis,the hydrocarbon detection effects were compared between FT- and WPT-based cepstra.The processing results of actual seismic data show that compared to the conventional spectral decomposition technology based on wavelet transform,the cepstrum decomposition technology manifested higher spatio-temporal resolution,providing more detailed information. Contrasting with FT-based cepstrum decomposition,WPT-based cepstrum decomposition provided a more accurate interpretation of gas-bearing properties through the seismic amplitude anomaly profiles.

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Application of three-dimensional magnetic anomaly inversion in magnetite exploration
ZHAO Bai-Ru, LI Hou-Pu, ZHANG Heng-Lei
Geophysical and Geochemical Exploration. 2024, 48 (6): 1626-1632.   DOI: 10.11720/wtyht.2024.0167
Abstract   HTML ( 2 )   PDF (3579KB)

The Galinge iron deposit in Qinghai is overlain by deposits measuring greater than 150 m in thickness. The great burial depths of ore bodies lead to gentle magnetic anomaly morphology, making it difficult to characterize the spatial distribution of ore bodies. Therefore, this study employed three-dimensional magnetic anomaly inversion to determine the three-dimensional distribution characteristics of subsurface magnetic intensity in the study area. Given the prior information of non-magnetic surrounding rocks, the three-dimensional magnetic intensity model clearly presented the spatial distribution of the ore bodies and reflected the presence of intense magnetic bodies at depths of less than 500 m in existing boreholes. Accordingly, it can be inferred that there exist concealed ore bodies at depths exceeding 500 m in the study area. The results of this study suggest that three-dimensional magnetic anomaly inversion can effectively improve target identification, providing clear information on the horizontal positions, depths, and scales of magnetic ore bodies. The proposed inversion method can offer strong support for drilling design and reserve estimation, warranting promotion in detailed exploration of solid minerals.

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Impacts of drone noise on semi-airborne transient electromagnetic data
WANG Zhi-Hong, ZHANG Nuo-Ya, HU Shan-Shan, ZHENG Zi-Qiang, LIU Yu-Chao, ZHOU Zheng, SUN Huai-Feng
Geophysical and Geochemical Exploration. 2024, 48 (6): 1633-1642.   DOI: 10.11720/wtyht.2024.1544
Abstract   HTML ( 1 )   PDF (4475KB)

As a semi-airbone transient electromagnetic (TEM) platform, drones inherently generate electromagnetic signals that may interfere with the collected transient electromagnetic data. This study investigated the impacts of drone noise on the collected data. Through outdoor experiments and systematic performance testing, this study analyzed the impacts of drone noise under varying rotor speeds, suspension lengths, flight height, and flight speeds. Accordingly, this study proposed methods for suppressing drone noise, such as determining the optimal suspension length and incorporating shielding layers. The study was conducted using the KWT-X8L-25 octocopter drones, but the research methodology and philosophy are also applicable to other drone models, thus serving as a reference for the selection of semi-airborne TEM platforms.

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Application of the stepwise amplitude consistency processing technique in splicing the large-scale profile of the Ordos Basin
XU Lei-Ming, LI Fei, WANG Jian-Hua, LI Mei, CAO Yong-Liang, WANG Hao-Kun
Geophysical and Geochemical Exploration. 2024, 48 (6): 1643-1652.   DOI: 10.11720/wtyht.2024.1498
Abstract   HTML ( 1 )   PDF (11758KB)

The Ordos Basin boasts abundant deep oil and gas resources.Hence,establishing the tectonic framework of the entire basin based on high-precision seismic imaging processing and structural interpretation holds critical significance.This study investigated the amplitude consistency problem in processing the large-scale 2D spliced profile of the basin. It employed a six-step amplitude consistency processing flow for amplitude preservation,involving energy adjustment between shots,spherical diffusion compensation,surface-consistent amplitude compensation,frequency-division amplitude compensation,and amplitude normalization based on the fold number/offset distribution.The processing flow effectively eliminated the amplitude inconsistency caused by the differences of survey lines in surface excitation and receiving conditions,acquisition methods,observation systems,and instruments in different years.The obtained basin-scale 2D spliced profile provided a reliable data basis for establishing the tectonic framework of the basin,clarifying the tectonic patterns,fault characteristics,and stratigraphic distributions of the fourth and third members of the Ordovician Majiagou Formation and the underlying strata,and predicting the distribution of paleo-uplifts.Moreover,the technique used in this study serves as a reference for processing seismic data of other complex areas.

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Wavefield decomposition based on sparse-constrained parabolic Radon transform in the frequency domain
ZHANG Yong-Sheng, ZHANG Rong, FAN Yi, ZHANG An-Jia, LI Ying-Cai
Geophysical and Geochemical Exploration. 2024, 48 (6): 1653-1663.   DOI: 10.11720/wtyht.2024.0059
Abstract   HTML ( 1 )   PDF (9451KB)

Multiple types of non-layered and irregular hydrocarbon reservoirs have been found in the deep carbonate strata within the Tarim Basin. These carbonate reservoirs, different from layered reservoirs, are geological bodies with limited lateral bodies in at least one direction. The observed seismic reflected wavefield is a composite field composed of reflected and diffracted (scattered) waves formed by layered strata and non-layered and irregular geological bodies. The three types of wavefields exhibit different morphological characteristics in different datasets. Based on the differences in wavefield morphology, this study, using a technique for separating layered and random wavefields based on an image-guided, sparse-constrained parabolic Radon transform in the frequency domain, decomposed high signal-to-noise-ratio data of complex reflected wavefields, which had undergone migration processing or not, into a reflected wavefield with infinite lateral extent and a diffracted (scattered) wavefield of irregular geological bodies with limited lateral extent. This technique provides a foundation for the direct prediction and investigation of irregular reservoirs and has been successfully applied in both the Tarim and Ordos basins.

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Impacts of anisotropy on the dynamic and static elastic characteristics of shales under stress effects
BIAN Hui-Yuan, ZANG Xin, ZHANG Di, ZHANG Cheng-En, NIE Xiao-Min, WU Yin-Ting
Geophysical and Geochemical Exploration. 2024, 48 (6): 1664-1673.   DOI: 10.11720/wtyht.2024.0014
Abstract   HTML ( 2 )   PDF (6062KB)

The static elastic parameters are crucial for shale oil and gas production and fracturing through water injection. Under stress effects, anisotropy exerts significant impacts on the dynamic and static elastic characteristics of shales. Investigating the dominant factors and mechanisms controlling reservoirs' dynamic and static elastic characteristics is a burning key scientific problem in shale oil and gas production and fracturing through water injection. Based on triaxial compression tests combining mechanics and acoustics for shales under different pressurization methods, this study delved into the impacts of anisotropy on the compressional/shear wave (P-and S-wave) velocities and macromechanical properties of shales, and the response patterns of dynamic and static elastic characteristics of shales. The results are as follows: (1) With an increase in the pressure, the dynamic and static Young's moduli of shales increase at a gradually decelerating rate, finally tending to be stable; (2) At certain bedding angles, the dynamic and static Young's moduli are positively correlated, with the former higher than the latter, whereas the dynamic and static Poisson's ratios manifest a subtle correlation; (3) The dynamic and static stiffness coefficients of shales increase with the confining pressure. The P-wave-related dynamic stiffness coefficients C11 and C33 display more significant changes than the S-wave-related dynamic stiffness coefficients C44 and C66; (4) The dynamic and static anisotropies of shales also increase with the confining pressure. The results of this study reveal the response mechanisms of the dynamic and static elastic characteristics of shales while providing crucial mechanical parameters for the exploitation and hydraulic fracturing of shale oil and gas reservoirs, thus demonstrating significant scientific research value.

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Multi-scale fault characterization using synchrosqueezing generalized S-transform
CHEN Ke-Lin, WEN Ran, YANG Yang, WU Li-Hui, YANG Gao-Jian, YAN Hai-Tao, ZHANG Kui
Geophysical and Geochemical Exploration. 2024, 48 (6): 1674-1683.   DOI: 10.11720/wtyht.2024.1453
Abstract   HTML ( 1 )   PDF (9329KB)

Post-stack fault recognition is typically performed based on structural attributes, which, however, frequently exhibit unclear characterization of fault contacts and poor fault continuity. Deep learning can characterize middle- to large-scale faults accurately but has a limited capacity to characterize small-scale ones. This study developed a multi-scale fault characterization algorithm using amplitude gradient clutter based on synchrosqueezing generalized S-transform (SSGST). First, seismic data were decomposed into single-frequency data volumes across different frequency bands in the time-frequency domain. Then, the clutter of the amplitude gradient vectors was computed based on the seismic data volumes of different frequency bands. Finally, multi-scale faults were characterized using seismic data volumes of different frequency bands. The results from both model simulations and practical data demonstrate that the amplitude gradient clutter property derived using SSGST provides can effectively characterize small-scale faults besides large-and medium-scale faults.

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Development of a MEMS-based seismograph for in-seam wave seismic exploration
ZHAO Peng-Peng
Geophysical and Geochemical Exploration. 2024, 48 (6): 1684-1692.   DOI: 10.11720/wtyht.2024.0208
Abstract   HTML ( 1 )   PDF (4410KB)

Currently,seismic data acquisition of in-seam waves is typically performed using mine-orientated digital seismographs combined with moving coil geophones.However,such conventional data acquisition system suffers from narrow frequency bandwidths and bulky equipment.To improve data quality and construction efficiency,this study designed a single-channel seismograph for in-seam wave exploration by incorporating a microelectromechanical system(MEMS) accelerometer,with the advantages of wide frequency bandwidth and miniaturization,into the acquisition card.The developed seismograph allows for independent excitation and distributed acquisition,with frequency bandwidths ranging from 1 to 800 Hz,resulting in improved data quality.A single seismograph weighs only 0.52 kg,and the integrated design completely eliminates the constraints of cables.The total weight of the 100 channel observation system is only 52 kg,representing only 10% of the weight of a distributed seismograph and 25% of that of a nodal seismograph system.The reduction in the overall weight contributes to both reduced transportation costs and enhanced construction efficiency.

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A method for estimating electromagnetic wave velocities in subsurface media based on common-offset GPR signal envelope and 3D velocity spectrum analysis
ZHOU Xin, WANG Hong-Hua, WANG Yu-Cheng, WU Qi-Ming, WANG Hao-Lin, LIU Hong-Rui
Geophysical and Geochemical Exploration. 2024, 48 (6): 1693-1701.   DOI: 10.11720/wtyht.2024.1526
Abstract   HTML ( 1 )   PDF (4846KB)

Currently,velocity spectrum analysis methods widely used for ground-penetrating radar(GPR) signals mostly construct velocity spectra by superposing the amplitude energy of coherent signals to estimate electromagnetic wave velocities in subsurface media.In the case of multiple peaks and troughs in signal wavelets,velocity spectra constructed using these amplitude-based methods display multiple energy clusters,adversely affecting the identification,picking,and velocity estimation of subsequent energy peaks.Hence,this study proposed a method for estimating electromagnetic wave velocities in subsurface media based on common-offset GPR signal envelope and 3D velocity spectrum analysis.By scanning the signal envelope of hyperbolic diffracted waves in the GPR profile,the proposed method constructed the 3D velocity spectra of superimposed energy varying with zero-offset two-way travel time,test velocity,and measuring point position.Moreover,it extracted the slices of 2D velocity spectra according to the positions of hyperbolic vertices in the 3D velocity spectra.On this basis,the test velocities corresponding to the energy peaks in the slices of 2D velocity spectra were picked as the electromagnetic wave velocities in subsurface media.The numerical test results show that compared to the amplitude-based methods,the signal envelope-based 3D velocity spectrum analysis method obtained velocity spectra characterized by fewer continuous energy clusters,more concentrated energy,and minor velocity estimation errors,thus more effectively constructing the velocity model with inverse-time migration.

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A multi-channel deconvolution method for self-adaptive signal recognition
ZHANG Jian-Lei, WANG Peng-Fei, SUN Yun-Song, LI Guo-Fa
Geophysical and Geochemical Exploration. 2024, 48 (6): 1702-1708.   DOI: 10.11720/wtyht.2024.1497
Abstract   HTML ( 1 )   PDF (7987KB)

Deconvolution plays a critical role in enhancing the resolution of seismic data.However,conventional deconvolution methods, though boosting the high-frequency components of seismic signals,amplify the energy of high-frequency noise,thereby reducing the signal-to-noise ratios(SNRs) of seismic records after deconvolution.The contradiction between resolution and SNRs restricts the ability of existing deconvolution methods to characterize thin-layer structures.Hence,this study proposed a multi-channel deconvolution method for self-adaptive signal recognition.The method extracted seismic signal recognition operators from raw seismic data.It introduced them as spatial regularization constraints into the objective function of multi-channel deconvolution,somewhat achieving high-resolution processing with self-adaptive signal recognition capabilities.Based on the spatial predictability of seismic signals,their recognition operators were estimated and extracted directly from seismic data,demonstrating high adaptability to seismic records.As indicated by the test analysis of the model and actual data,the proposed method can effectively suppress the amplification effect of high-frequency noise during deconvolution,thus improving resolution and maintaining the SNRs of seismic records.

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Effective information extraction from high-order pseudo-random electromagnetic signals in urban environments:A case study of a rail transit engineering area in Jinan City, China
MA Zhen-Bo, ZHOU Chang-Yu, RUAN Jin-Ping, ZHANG Wen-Yan
Geophysical and Geochemical Exploration. 2024, 48 (6): 1709-1719.   DOI: 10.11720/wtyht.2024.1535
Abstract   HTML ( 3 )   PDF (7825KB)

The spectra of high-order pseudo-random electromagnetic signals encompass all the frequencies required for exploration engineering, it has the characteristics of enhancing work efficiency and strong anti-interference capability, and has been applied in electromagnetic exploration in urban environments. This study extracted effective information from high-order pseudo-random signals in the electromagnetic survey conducted in areas with strong powerline interference within the special exploration area of the Phase I engineering of the Jinan Urban Rail Transit Line 8. To efficiently extract high-quality effective information, an envelope assessment algorithm was combined with high-order pseudo-random signals. Specifically, the actual signal interference was accurately estimated by analyzing the spectral envelope values. This allows for screening received signals, thus further mitigating the impacts of powerline interference and its harmonics. As a result, more effective frequency and geoelectric information were obtained, providing abundant effective electromagnetic data for subsequent inversion and interpretation. The novel method serves as a technique for effective information extraction for future electromagnetic sounding in a complex urban environment.

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Landslide survey based on three-dimensional resistivity inversion: A case study of the Xuelang Mountain scenic spot, Wuxi, China
JIANG Guo-Qing, HAO She-Feng, YU Yong-Xiang, Du Jian-Guo, LI Ming, SHANG Tong-Xiao, SONG Jing-Lei
Geophysical and Geochemical Exploration. 2024, 48 (6): 1720-1729.   DOI: 10.11720/wtyht.2024.0121
Abstract   HTML ( 4 )   PDF (5261KB)

Effectively identifying the stratigraphic and landslide structures in landslide-prone areas is significant for disaster prevention and mitigation. By investigating the landslides in the Xuelang Mountain scenic spot in Wuxi, this study analyzed the differences between two-and three-dimensional inversion using the high-density resistivity method. Accordingly, this study explored methods for eliminating the banded effect in the three-dimensional inversion, performed three-dimensional resistivity inversion under the constraints of high-precision surface elevation data and borehole-derived prior information, and constructed a three-dimensional geological model for the study area. The results indicate that three-dimensional resistivity inversion enjoys distinct advantages in complex landslide surveys. The banded effect can be effectively suppressed by optimizing the grid spacing, damping coefficient, and filter parameters for inversion. Furthermore, the terrain-induced impacts and the multiplicity of solutions of the inversion can be significantly reduced using constraints of refined terrain data and prior information, thus improving the resolutions of stratigraphic boundaries and landslide structures. Through three-dimensional resistivity inversion and geological modeling, this study determined the three-dimensional stratigraphic structure, along with the spatial distributions of the landslide bodies and sliding surfaces, and investigated landslide mechanisms, providing important data for the survey and control of landslides in the study area.

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A comprehensive crosshole tomography method for karst identification based on color fusion technology
MOU Xiao-Dong
Geophysical and Geochemical Exploration. 2024, 48 (6): 1730-1740.   DOI: 10.11720/wtyht.2024.0247
Abstract   HTML ( 1 )   PDF (5669KB)

Single crosshole tomography features a multiplicity of solutions, rendering it challenging to accurately identify karst anomalies. Given this, this study introduced color fusion technology and tested its effectiveness in the inversion of three types of crosshole seismic CT data using numerical simulations: elastic wave travel time CT, elastic wave attenuation CT, and electromagnetic wave attenuation CT. A field experiment on karst identification using comprehensive crosshole CT data reveals that the color fusion technology can effectively enhance the accuracy of karst identification. The results of this study provide an effective method for comprehensive crosshole detection and interpretation for karst exploration in foundational projects such as oil and gas pipelines, bridges, and tunnels, holding great significance for improving the exploration accuracy of karst.

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Application of ground-penetrating radar in detecting the internal structures of the ancient Great Wall in Linhai City
YANG Hao, ZOU Jie, CHENG Dan-Dan, YU Jing-Lan
Geophysical and Geochemical Exploration. 2024, 48 (6): 1741-1746.   DOI: 10.11720/wtyht.2024.0091
Abstract   HTML ( 1 )   PDF (3789KB)

Non-destructive testing of the internal structural characteristics of ancient buildings is the key to preserving cultural relics.To determine the structures and internal defects of the ancient Great Wall in Linhai City,this study performed non-destructive testing of the wall structures in different orientations using a ground-penetrating radar (GPR) combining 100 MHz and 270 MHz antennas.The testing results show significant structural stratification in the ancient Great Wall.The GPR signal-reflected images reveal clear internal wall defects like pores,cracks,voids,and other hidden dangers.This study demonstrates the reliability of the GPR in detecting structures and defects of ancient walls,there by providing technical support for the structural protection of the ancient Great Wall.

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AN ANALYSIS OF THE SPECIAL WAVE IMPACT ON THE INTERPRETATIONOF THE COALFIELD COLLAPSE COLUMN
YANG Xiao-Dong, YANG De-Xi
Geophysical and Geochemical Exploration    2010, 34 (5): 627-631.  
Abstract2675)      PDF (4180KB)(4946)      


In the light of typical coneshaped columns in the Lu'an mine of Shanxi Province, the authors

established a mathematical model for the collapse column, and used the wave equation model for

seismic ray tracing and wavefield simulation of collapse columns. The simulation results show that,

due to the special nature of the collapse columns, such waves as the normal reflected wave, the fault

point diffraction wave, the delay diffraction wave, the delay reflected wave and  the "diffraction

wave" consisting of Pwave field are formed around the collapse columns. On such a basis, the field

shot was simulated, and then a single shot record for routine processing  was generated to produce

stacking sections and migrated sections. The forward section and the actual data analysis reveal that

the fallen columns of the special wave constitute an important feature for recognizing collapse

columns; nevertheless, the resultant scale of the actual seismic data interpretation is often smaller

than the scale of actual collapse column. Some suggestions are also put forward for reference.

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The application of integrated geological, geochemical and geophysical techniques to the exploration of the Bogutu gold deposit
YAO Tie, ZHOU Yong, DU Zhan-Jun, ZHAO Zhen-Ming
Geophysical and Geochemical Exploration    2015, 39 (5): 877-884.   DOI: 10.11720/wtyht.2015.5.01
Abstract1416)   HTML151)    PDF (12833KB)(4359)      

Low density geochemical survey in Yishenjilike mountain area led to the discovery of a huge gold geochemical block, and the verification and evaluation of gold anomalies led to the discovery of the Bogutu gold deposit. In combination with the geological characteristics of the prospecting area, the authors carried out a series of geological-geophysical-geochemical exploration work, delineated quite a few geochemical and IP anomalies, and detected the characteristics of ore-bearing structural belt. Through trenching and drilling verification, the authors found more than 40 gold orebodies, thus achieving good ore-prospecting results.

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The application of integrated geophysical prospecting methods to the exploration of urban buried fault
LIU Wei, HUANG Tao, WANG Ting-Yong, LIU Yi, ZHANG Ji, LIU Wen-Tao, ZHANG Qi-Bin, LI Qiang
Geophysical and Geochemical Exploration    2021, 45 (4): 1077-1087.   DOI: 10.11720/wtyht.2021.1525
Abstract867)   HTML408)    PDF (4078KB)(3969)      

The existing geological data show that there are several buried faults in the main urban area of Chengdu. However, the specific location and distribution of these faults are still unclear, which poses great security risks to the comprehensive and scientific exploitation and utilization of underground space resources and the optimization of urban construction planning and layout in Chengdu. In view of such a situation, four geophysical methods, namely, micromotion survey, high-density electrical method, transient electromagnetic method and soil radon measurement, were used in this paper to comprehensively explore the buried Baojiangqiao fault in the work area. The integrated geophysical prospecting methods not only identified the stratigraphic structure along the survey line, but also obtained the location, property, attitude and scale of the buried Baojiangqiao fault. This work indicates that the integrated geophysical prospecting methods can achieve better results in the exploration of urban buried fault.

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A NEW DEVELOPMENT PERIOD OF THE GRAVITY AND MAGNETIC EXPLORATION
ZHANG Chang-Da, DONG Hao-Bin
Geophysical and Geochemical Exploration    2010, 34 (1): 1-7.  
Abstract3409)      PDF (431KB)(3608)      

A review on the airborne gravity survey and airborne magnetic survey are given in this paper. The

authors hold that these techniques have entered into a new development period, as evidenced by the

emergence of such technologic indicators as airborne vector magnetometry, magnetic fulltensor LTSSQUID

and HTSSQUID gradiometry, airborne gravimetry, gravity gradiometry and geophysical survey by UAV.

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THE ADVANCES IN THE STUDY OF THE AIRBORNE GRAVIMETRY SYSTEM
WANG Jing-Bo, XIONG Sheng-Qing, ZHOU Xi-Hua, GUO Zhi-Hong
Geophysical and Geochemical Exploration    2009, 33 (4): 368-373.  
Abstract2986)      PDF (1014KB)(3501)      

This paper gives a brief review of the history of the airborne gravimetry. Based on the principle of the airborne gravimetry, the paper deals emphatically with the history, the present  research situation and the developments of the airborne scalar gravity survey system. Further development trends are also indicated.

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3D DISPLAY FOR GROUND PENETRATING RADAR BASED ON Matlab
WU Bao-Jie, JI Mei-Xiu, YANG Hua
Geophysical and Geochemical Exploration    2009, 33 (3): 342-344.  
Abstract6842)      PDF (532KB)(3164)      

 With powerful Matlab image processing functions, this paper has realized the 3D display of ground penetrating radar data, whose procedures are simple to prepare and easy to learn. A detailed description of the code is given, and the three-dimensional test data show that, by setting transparency, the target can be displayed in an intuitive and visual way.

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THE UTILIZATION OF EXCEL TO THE PERFORMANCE OF R-MODE CLUSTER ANALYSIS
CHUN Nei-ya
Geophysical and Geochemical Exploration    2007, 31 (4): 374-376.  
Abstract4689)      PDF (659KB)(2840)      

The R-mode cluster analysis is a mathematic statistical method for obtaining the quantitative similarity of several elements. Its procedure includes: the conversion of the original data; the solution of the relevant coefficient ; the clustering of the result. The above operation can be realized by using the data analysis tool of Excel. This method is quite suitable for field utilization.

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CALCULATION OF THE ANOMALY AREA
Zhao Rongjun
Geophysical and Geochemical Exploration    2000, 24 (2): 154-156.  
Abstract1614)      PDF (346KB)(2738)      

This paper puts forward a new method for calculating anomaly area—the polygonous approximation method,and gives corresponding algorithm and precision controlling technique.With this method,one can calculate anomaly area rapidly and precisely,thus yielding relatively satisfactory results.

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THE CHOICE OF GRIDDING METHODS FOR GEOPHYSICAL DATA
LIU Zhao-Ping, YANG Jin, WU Wei
Geophysical and Geochemical Exploration    2010, 34 (1): 93-97.  
Abstract3202)      PDF (1939KB)(2729)      

In drawing the contour map of geophysical data, suitable gridding methods should be chosen according to objective

environment characteristics and characteristics of data themselves. With practical examples, this paper deals with some common

gridding methods such as inverse distance to a power, Kriging, Minimum Curvatrue, Nearest Neighbor, Polynomial Regression, Radial

Basis Function, and Triangulation/Liner Interpolation, probing into their choosing means, applicable fields and parameter

installment.

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THE APPLICATION OF ATOM INTERFEROMETER TO THE MEASUREMENT OF GRAVITATIONAL ACCELERATION
ZHANG Chang-da
Geophysical and Geochemical Exploration    2000, 24 (5): 321-326.  
Abstract1770)      PDF (673KB)(2699)      

This paper has described and reviewed the pinciples,expermental set up and observational results of applying atom interferometer to measuring the earth's gravitational acceleration.This method was developed by Nobelist Steven Chu,M.Kaservich,A.Peters et al.,who demonstrated a resolution of 10-10.The application of this technique to geophysics and the related problems are also discussed.

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THE APPLICATION OF THE GRADIENT SOUNDING PROFILE METHOD TO THE GOLD PROSPECTING IN THE YINAN GOLD MINE
DU Li-ming, WU Jun-jie, YANG Jin-duo, WANG Peng, YU Bao-xian
Geophysical and Geochemical Exploration    2013, 37 (2): 225-228.   DOI: 10.11720/j.issn.1000-8918.2013.2.07
Abstract2397)      PDF (964KB)(2576)      
IP is an important method for mineral resources exploration, but it can only be applied in a few pivotal places because its difficult performance, and hence the information obtained from the survey area is very limited. The aim of this study is to find a simple and effective IP method with which we can get much valuable information form the survey area so as to improve the exploration effect. In the Yinan gold ore district, the authors applied the gradient sounding profile method, calculated 2D resistivity and obtained the IP model. The results show that the gradient sounding profile method is simple and effective.
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RECENT ADVANCES IN THE RESEARCH AND DEVELOPMENT OF QUANTUM MAGNETOMETERS
ZHANG Chang-da
Geophysical and Geochemical Exploration    2005, 29 (4): 283-287.  
Abstract1791)      PDF (376KB)(2536)      

In this paper, recent advances in the research and development of quantum magnetometers have been described together with some suggestions on further research work.

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THE EXTRACTION METHOD AND PROGRAM DESIGN FOR DISPERSION CURVE IN F-K DOMAIN
LI Jie, CHEN Xuan-hua, ZHANG Jiao-dong, ZHOU Qi, LIU Gang, LIU Zhi-qiang, XU Yan, LI Bing, YANG Jing
Geophysical and Geochemical Exploration    2011, 35 (5): 684-688.  
Abstract3791)      PDF (534KB)(2491)      

Based on two-dimensional Fourier transform and half-wave theory, this paper has studied the seismic Rayleigh wave dispersion curve extraction in f-k domain and made this theory fit in with a program by means of Delphi7.0. It is concluded that the f-k method overcomes the shortcomings of the one-dimensional digital processing technology and makes full use of multi-channel Rayleigh wave data record.

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CHEMICAL COMPOSITIONS OF CONTINENTAL CRUST AND ROCKS IN EASTERN CHINA
Yan Mingcai, Chi Qinghua, Gu Tiexin, Wang Chunshu
Geophysical and Geochemical Exploration    1997, 21 (6): 451-459.  
Abstract3098)      PDF (2969KB)(2486)      

Element abundances of the continental crust and rocks cited in the past and recent literature have been based on compilations of data from various studies. This leads to uncertainties in sample representativeness and data quality. The present study is based on systematic collection of 28 253 individual rock samples over an area of 3.3 million km2 in eastern China, east of eastern longitude of 105°.The sampling involves more than 800 igneous intrusive bodies and metamorphic complexes as well as more than 500 type stratigraphic sections. From the individual rock samples, 2 718 composite samples were made and analyzed for 77 elements by 15 specific methods, dominantly XRF and INAA. Analytical quality was controlled by international and national preliminary geochemical reference materials of GSR, GAu and GPt series. Synthetic results from geological, geochemical and geophysical studies were used to construct crustal constitution model, from which element abundances of the continental crust in the North China platform, the upper crust and exposed crust in eastern China, chemical composition of igneous rock in China and of sedimentary rock and metamorphic rock in eastern China were derived.

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THE APPLICATION OF NEW GEOCHEMICAL EXPLORATION METHODSTO MINERAL EXPLORATION AND ITS GEOLOGICAL EFFECT
JIANG Yong-Jian, WEI Jun-Hao, ZHOU Jing-Ren, WANG Zhong-Ming, JI Zhao-Jia, WANG Fa-Yan
Geophysical and Geochemical Exploration    2010, 34 (2): 134-138.  
Abstract4334)      PDF (403KB)(2476)      

As an important prospecting technique and an effective means for obtaining mineralization data,

geochemical exploration has been proved to be very successful in mineral exploration. This paper focuses on

commenting the present research situation and application effect of some new methods such as structural

superimposed halos method, heat released mercury method, separatory electrogeochemistry method, enzyme leach, and

geogas and selective leaching of mobile metals method. It is emphasized that any one of these methods has its

unique applicability and that, in the practical application, we should pay attention to the cooperation of

geochemical exploration, geologicalgeophysical exploration and remote sensing and depend on the study of

geological background so as to demonstrate the usefulness and effectiveness of geochemical exploration.

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THE PRESENT SITUATION AND RESEARCH ADVANCES OF EXPLORATION GEOCHEMISTRY FOR PORPHYRY COPPER DEPOSITS
HU Shu-qi, MA Sheng-ming, LIU Chong-min
Geophysical and Geochemical Exploration    2011, 35 (4): 431-437.  
Abstract3780)      PDF (643KB)(2414)      

Porphyry copper deposit is the most important copper deposit type in China. With the deepening of mineral exploitation, exploration geochemistry in mineral exploration has become increasingly important. Based on related literature, this paper sums up the exploration geochemical research results of porphyry copper deposits, which include such aspects as geochemical characteristics, exploration methods, anomaly evaluation and prospecting indicators. Exemplified by the Fujiawu copper deposit, this paper reports the latest advances in the study of porphyry copper deposits.

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THE PROGRESS AND PROSPECT OF THE ELECTRICAL RESISTIVITY IMAGING SURVEY
YAN Jia-yong, MENG Gui-xiang, LV Qing-tian, ZHANG Kun, CHEN Xiang-bin
Geophysical and Geochemical Exploration    2012, 36 (4): 576-584.   DOI: 10.11720/wtyht.2012.4.13
Abstract5089)      PDF (1427KB)(2395)      
This paper has summed up the progress of the ERI method over the past decade of years as well as its future development trend in the following aspects: ① A comparison of the performances of the main ERI instruments used at present shows that the ERI instruments tend to develop in the multi-channel, multi-parameter, multi-functional, high-power direction; ② ERI measurement environment has changed from surface measurement to water surface, underwater and cross-hole measurements, with the last three kinds of measurements analyzed in this paper; ③ On the basis of analyzing ERI data processing method and inverse development status, this paper describes three-dimensional and four-dimensional inversion theory of ERI with practical examples; ④ ERT applications are summed up, and several new applications are introduced. It is concluded that, with the improvement of the probing depth and observation precision as well as the diversification of the observation models, the application field of ERI will become broader and broader, and this technique will surely have wide development prospect.
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Characteristics of gravity and magnetic fields in Ordos Basin and their geological significance
Bing LI, Yan-Bing SONG, Lei SHI, Qi WANG, Jiu-Ming JIANG, Jiu-Qiang JIN, De-Wen ZHOU, Ming XU, Gang-Yi XIAO, Min-Ying XIE
Geophysical and Geochemical Exploration    2019, 43 (4): 767-777.   DOI: 10.11720/wtyht.2019.1391
Abstract701)   HTML3)    PDF (3147KB)(2290)      

According to aeromagnetic and gravitational data, the boundary and range of Ordos basin were determined based on an analysis of the characteristics of gravity and magnetic fields. And on the basis of compiling depth map of the metamorphic basement and structuring zoning map, research was conducted on the basin’s basement structure, characteristics and features of depth change, structure framework, and caprock thickness. The research indicates that the metamorphic basement is composed of Proterozoic metamorphic series, and the buried depth of crystalline basement can reach 5 000 to 20 000 meters. The caprock is the layers of Ediacaran, Paleozoic, and Mesozoic. The occurrence and development of the basin are restricted by nearly NE-and NWW-trending structures, forming a pattern of four depressions and three uplifts. All the new understanding and conclusions provide a reference for further oil and gas exploration in the basin.

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ABUNDANCE OF CHEMICAL ELEMENTS OF SOILS IN CHINA AND SUPERGENESIS GEOCHEMISTRY CHARACTERISTICS
Yan Mingcai, Gu Tiexin, Chi Qinghua, Wang Chunshu
Geophysical and Geochemical Exploration    1997, 21 (3): 161-167.  
Abstract2666)      PDF (2180KB)(2286)      

On the basis of accurate analysis of 154 composite soil samples collected from various landscape in China and other reference information, abundance of 79 elements and composition of soils in China have been given, chemical composition of soils under the influence of matrix rock and supergenesis geochemistry condition have been studied preliminarily.

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RESEARCH AND APPLICATION ON NUMERICAL INTEGRATIONOF HANKEL TRANSFORMS BY DIGITAL FILTERING
ZHANG Wei, WANG Xu-Ben, QIN Qing-Yan
Geophysical and Geochemical Exploration    2010, 34 (6): 753-755.  
Abstract3764)      PDF (363KB)(2282)      

 Numerical integration of Hankel transforms is effective tools for EM Sounding 's forward numerical simulation, this paper made out formula derivation of numerical integration of Hankel transforms by digital filtering, and use digital coefficients to do numerical compute which was put forward by Guptasama and Singh,finally contrasted to theoretical resolve expression and analyzed this algorithm's error distribution. The results show that the calculation of this algorithm continuously approximate its theoretical solution, it has no oscillation, high precision and great practical value in the numerical simulation study.

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PARAMETER SELECTION IN VIBROSEIS SEISMIC EXPLORATION
XUE Hai-Fei, DONG Shou-Hua, TAO Wen-Peng
Geophysical and Geochemical Exploration    2010, 34 (2): 185-190.  
Abstract3525)      PDF (3477KB)(2272)      

 Vibroseis exploration, as an important method of seismic exploration, has become increasingly valued by geologists. During the field work, different geological conditions need different parameters, and the choice of suitable excitation parameters has become a very important problem. This paper mainly introduces six kinds of parameters, namely numbers of controlled seismic source, scanning bandwidth, vibration period, scanning length, scanning slopes, and vibration rate. The influence of these parameters on the quality of seismic records was studied in detail, and the simulation of the proper parameters was performed in Jiulishan area to enhance the resolution of vibroseis exploration and improve the signaltonoise ratio of seismic records.

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FEATURES OF GEOPHYSICAL COMPOSITE ANOMALIES AND ORE RESOURCES IN YIHUANG AREA, JIANGXI PROVINCE
WANG Wei-Beng, FANG Ying-Yao, TUN Cheng-Beng
Geophysical and Geochemical Exploration    2010, 34 (5): 573-578.  
Abstract3107)      PDF (2717KB)(2242)      

According to the data obtained from air-borne electromagnetic and magnetic survey and

ground two-frequency IP and magnetic survey, this paper discusses the relationship between the

features of air-borne and ground geophysical composite anomalies and the ore resource distribution.

On the basis of an integrated analysis, geophysical composite anomaly criteria in search for iron, zinc

and lead deposits were established, and 12 important ore-prospecting targets were delineated, which

provides very important clues for finding iron, zinc, lead and some other ore resources.

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THE UTILIZATION OF SURFER TO CONDUCT THE DRAWING OF PROFILE-PLAN
SUN Zhong-ren, ZHAO Dong-liang
Geophysical and Geochemical Exploration    2006, 30 (2): 172-174.  
Abstract3607)      PDF (572KB)(2233)      

This paper has put forward the idea of utilizing Surfer to draw the initial data profile-plan. The programme compiled can realize the construction of Bln file. The profile-plans for regular net and irregular net have been constructed, and the results are satisfactory.

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THE AUTOMATIC FORMATION OF THE SUFFER SOFTWARECONTOUR LEVEL FILE BASED ON AREA STATISTICS
REN Lei, CHEN Hua-Gen
Geophysical and Geochemical Exploration    2009, 33 (5): 595-598.  
Abstract3676)      PDF (830KB)(2218)      

The implied contour level and color scheme in Surfer software fail to express the subtle difference of DEM and the effect

of color solid. In addition, the artificial setting of the levels and color values are timeconsuming and laborious, and the

results are sometimes not perfect. With the consideration of contour level and color scheme and on the basis of Surfer platform

automation technology, this paper presents a program that can automatically generate a level file with different intervals and

different colors, thus resulting in satisfactory effect and efficiency.

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Geophysical and Geochemical Exploration    1982, 6 (3): 154-156.  
Abstract1204)      PDF (190KB)(2192)      
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MIGRATION VELOCITY ANALYSIS AND MIGRATION IMAGING RESEARCH
YE Jing-Yan, YAO YA-Lin, WANG Yan-Qun, LI Qing
Geophysical and Geochemical Exploration    2009, 33 (6): 674-677.  
Abstract2860)      PDF (1927KB)(2173)      

Migration velocity analysis and migration imaging constitute two important parts in seismic data processing. At

present, time migration has become mature, and depth migration is getting more and more perfect. The common method for time

domain migration imaging is pre-stack time migration. By adopting stacking velocity analysis along the layer, exact layer

stacking velocity can be obtained. Through dip correction, pre-stack time migration and CRP de-migration velocity analysis, the

velocity is optimized step by step, and then a desired RMS velocity field that is up to the geological rule is acquired. In

addition, the method for building the accurate migration velocity field is summed up through the study of the depth migration

method. A new seismic data processing flow in combination of Kirchhoff arithmetic based on ray tracing and wave equation

arithmetic based on wave field extrapolation is presented. As a result, migration velocity analysis and migration imaging are

considerably improved.

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WAVE FIELD SEPARATION NUMERICAL MODELING OF SECOND ORDER ELASTIC WAVE EQUATION BY HIGH-PRECISIONSTAGGEREDGRID FINITE DIFFERENCE SCHEME
CHEN Ke-Yang, YANG Wei, LIU Hong-Lin, WU Qing-Ling
Geophysical and Geochemical Exploration    2009, 33 (6): 700-703.  
Abstract3202)      PDF (1060KB)(2165)      

This paper proposes an equivalent second order elastic wave equation to solve the problem of being unable to completely

separate the coupled P and S wave by full elastic wave equation. Through solving this equivalent wave equation by high-order

staggeredgrid finite difference scheme together with Flux Correction Technology (FCT) and separating wave fields of the

isotropic model and layered model, the authors accurately obtained the hybrid wave field and completely separated fields of pure

P wave and pure S wave fields. An analysis of the numerical results shows that the method is effective and reliable in isotropic

media, and there exists abundant energy transform information in separated pure P and pure S wave field. The result of the study

is of significance in understanding the propagating law and the elastic wave theory in the complex wave field.

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THE INVERSED PROBLEM IN GRAVITY AND MAGNETICEXPLORATION: A REVIEW
Zeng Hualin
Geophysical and Geochemical Exploration    1990, 14 (3): 182-190.  
Abstract2079)      PDF (737KB)(2134)      

On the basis of mote than230 English and Russian papers or monographsissued in the last 30 years as well as nearly 50 Chinese articles published overthe past 10 years on the inversed problem in g avity and magnetic explora-tion, combined with his practice in the study of the inversed problem, the all-thor expounds the inversed methods in gravity and magnetic exploration cur-rently used both at home and abroad, briefs the readers about the researchsituation in China and foreign countries, and makes a detailed review on achi-evements gained in China in comparison with the research levels abroad.Final-ly, suggestions are put forward concerning some subjects which are worthnoticing in future research work.

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PRESENT RESEARCH SITUTATION AND DEVELOPMENT TREND OF AIRBORNE GRAVITY GRADIOMETER
SHU Qing, ZHOU Jian-xin, YIN Hang
Geophysical and Geochemical Exploration    2007, 31 (6): 485-488.  
Abstract2229)      PDF (690KB)(2110)      

The development of the gravity gradiometer is described simply in this paper, and the measuring principle and development experience of the rotating accelerometer gravity gradiometer are emphatically discussed. On the basis of researches on the existing airborne gravity gradiometer, the prospects of the airborne gravity gradiometer are also presented.

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A TENTATIVE DISCUSSION ON THE RESOLUTION OF THE GROUND-PENETRATING RADAR
YUAN Ming-de
Geophysical and Geochemical Exploration    2003, 27 (1): 28-32.  
Abstract2547)      PDF (512KB)(2103)      

In the light of the pulse width of the radar wave, this paper deals with the difference and the relationship between the vertical resolution and the transverse resolution of the ground-penetrating radar, indicates the influence of the noise upon the resolution and, with practical examples, points out that the digital handling of the signal can greatly improve the resolution of the radar.

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PRESENT STATE AND REVIVAL OF GRAVITY GRADIOMETRY
Zeng Hualin
Geophysical and Geochemical Exploration    1999, 23 (1): 1-6.  
Abstract2276)      PDF (474KB)(2083)      

In this paper,a historical review of the gravity gradiometry is given, the application of this technique to oil exploration and some other fields is described,and its development in future is predicted.

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THE APPLICATION OF SEISMIC REFRACTION WAVE METHOD ANDHIGHDENSITY RESISTIVITY METHOD TO TUNNEL INVESTIGATION
ZENG Guo, CUI De-Hai, LIU Jie, LI Kai
Geophysical and Geochemical Exploration    2009, 33 (5): 608-612.  
Abstract3244)      PDF (1351KB)(2048)      

 Basic principles and techniques for the shallow seismic refraction wave method and the highdensity resistivity method

are described in this paper in combination with engineering practice to explain the results of the refraction wave method and the

high-density resistivity method in railroad and highway tunnel exploration. The application effects of the combination of these two

methods in detecting positions, sizes, natures and characteristics of such harmful geological bodies as concealed faults and shatter

zones are also discussed. Some measures for improving the investigation accuracy of these two methods are put forward.

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SOME PROBLEMS CONCERNING THE CONVERSIONOF MAPS BETWEEN SURFER AND MAPGIS
QIN Lin-Jiang
Geophysical and Geochemical Exploration    2010, 34 (5): 677-680.  
Abstract5531)      PDF (865KB)(2041)      

With the extensive adoption of computer technology in geology and geophysics, computer graphics becomes more and more important. For the purpose of improving quality and efficiency, several software should be combined in practical work. In this paper, some basic characteristics of Surfer and MapGIS are discussed, and their application in geological field is described from the angle of geological mapping, thus drawing forth the necessity of the conversion between Surfer and MapGIS. The general method and steps for the conversion of maps between Surfer and MapGIS are presented in detail, and several problems concerning the conversion and corresponding solutions are emphatically discussed.

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PML ABSORBING BOUNDARY CONDITION FORNUMERICAL MODELING OF RAYLEIGH WAVE
XIONG Zhang-Qiang, TANG Sheng-Song, ZHANG Da-Zhou
Geophysical and Geochemical Exploration    2009, 33 (4): 453-457.  
Abstract3463)      PDF (2025KB)(2025)      

The algorithm of the finite difference oforder velocitystress staggered grids has been built, which is

suitable for the perfectly matched layer (PML) absorbing boundary for elastic media. Meanwhile, the construction of the

PML absorbing boundary condition and the realization of the finitedifference algorithm are discussed in detail. Wave

field modeling calculations show that, compared with the conventional decaying exponential absorbing boundary and non

absorbing boundary, the PML absorbing boundary can perform absorption much more clearly and absorb the boundary

reflection from various angles, whose absorptivity (the ratio of absorption energy to unabsorbable energy) can reach

99.99%. The PML absorbing boundary can well eliminate the periodic folding effects, which makes the calculation of the

wave field characteristics very distinct, and the Rayleigh wave can be clearly shown in the waveform record.

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THE COMPARATIVE STUDY AND APPLICATION OF SEVERALTIMEFREQUENCY ANALYSIS METHODS IN THE COAL FIELD
HU Ming-Shun, PAN Dong-Ming, XU Hong-Li, ZHAO Li-Gui
Geophysical and Geochemical Exploration    2009, 33 (6): 691-695.  
Abstract2516)      PDF (2110KB)(2021)      

In the light of the characteristic time-frequency properties of different time-frequency analysis methods, it is

important to select an optimal time-frequency analysis method for high precision seismic exploration in the coal field on the

basis of comparing and studying these methods. Aimed at probing into STFT, Wavelet Transform, S-Transform, Choi-Williams

Distribution, Wigner-Ville Distribution and its improved methods, this paper studied advantages and disadvantages of every method

through numerical simulation in time resolution, frequency resolution and interference. The First Break Picking and Separate

Frequency Display for Collapse Column interpretation were realized by SPWVD and S-Transform, with a good result obtained.

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THE DISTRIBUTION AND LEVEL OF RADON GAS IN SOIL IN A HIGH RADIATION BACKGROUND CITY OF CHINA
WANG Nan-ping, XIAO Lei, LI Can-ping
Geophysical and Geochemical Exploration    2012, 36 (4): 646-650.   DOI: 10.11720/wtyht.2012.4.27
Abstract3861)      PDF (726KB)(2017)      
A soil gas radon survey was performed on a large scale to determine the distribution of radon in soil of Zhuhai City in Guangdong Province by means of a portable radon monitor of a semiconductor alpha spectroscopy. The survey sampled 469 sites covering an area of more than 100 km2. The average of soil radon concentration in the soil depth of 0.6 m is 55.94 ± 58.54 kBq/m3 in Zhuhai urban area, whereas the concentration is 7.14±8.75, 37.64±25.92, and 151.25±196.23 kBq/m3 in the Quaternary sediments, the mixtures of sediments and weathered grain of granite, and the weathered granite in Doumen District, respectively. The high radon potential areas are located within biotitic granites and new industrial districts, as indicated by the strong correlation between the radioactivity level and geological lithology. The mean value of soil gas radon concentration in Zhuhai urban area (ZUA) is about ten times as high as that in Guangzhou, Quanzhou and Jinjing City. The results show that Zhuhai area has higher radon potential, and hence protective measures against radon should be taken into account.
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YANG Li-De
Geophysical and Geochemical Exploration    2009, 33 (6): 741-742.  
Abstract2226)      PDF (240KB)(2013)      
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CHAMP, GRACE AND GOCE: THREE SATELLITES FOR SENSING AND/OR MEASURING THE EARTH'S GRAVITY FIELD
ZHANG Chang-da
Geophysical and Geochemical Exploration    2005, 29 (5): 377-382.  
Abstract2146)      PDF (749KB)(1982)      

In this paper, the working principle of three satellites (CHAMP, GRACE and GOCE) has been described, and the important geopotential models and the newest geopotential models (EIGEN-CG01C, GGM02) have been introduced.

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The application of the integrated geophysical-geochemical method to the Yiliu polymetallic ore district in northern Guangdong Province
WU Wei-Guo
Geophysical and Geochemical Exploration    2015, 39 (6): 1097-1103.   DOI: 10.11720/wtyht.2015.6.01
Abstract1159)   HTML152)    PDF (11771KB)(1958)      

The main minerals in the Yiliu polymetallic ore district are mainly As, Sb, Pb, Zn, Ag, W, Sn, Nb and Ta, the deposit types and the ore-controlling factors are complex and diverse. Recently, by using 1:50000 geochemical stream sediment survey, geochemical soil survey and CSAMT method in this ore district, supergene distribution of elements were found, and many integrated anomalies were delineated. A comprehensive evaluation of all kinds of anomalies shows that the F3 fault has features of ore-passage structure and ore-storage structure, and the area sandwiched between F2 and F3 fault are favorable ore-forming place, whereas the depression parts of biotite granite which have high resistance and multiple sets of fracture intersections are most favorable places for mineralization.

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THE APPLICATION OF THE RAYLEIGH SURFACE WAVE TECHNIQUE TO RAILWAYS
LI Hai
Geophysical and Geochemical Exploration    2002, 26 (2): 160-162.  
Abstract1920)      PDF (480KB)(1957)      

With practical examples, this paper deals with the basic principle and technique of the Rayleigh surface wave exploration, the technology for its application to railways, the data acquisition, processing and interpretation, and the calculation method for converting the velocity of the Rayleigh surface wave to the bearing capacity. The reliability of applying this technique to railways is also pointed out.

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Advances in research on the distributed optical fiber acoustic sensing system in the field of geophysical exploration
ZHOU Shao-Yu, BAO Qian-Zong, SHI Wei
Geophysical and Geochemical Exploration    2024, 48 (2): 411-427.   DOI: 10.11720/wtyht.2024.1304
Abstract288)   HTML5)    PDF (7793KB)(313)      

Distributed acoustic sensing (DAS) technology, one of the most advanced sound field detection technologies, can achieve distributed, long-distance, and high-precision real-time detection of the ambient vibration and sound field information interacting with optical fiber. The optical fiber exploration system of the DAS technology solves the problems of high cost and deployment difficulty of conventional geophones in complex geological environments. In recent years, the DAS technology has experienced rapid development, especially in monitoring application scenarios that require long-term and large-scale deployment. However, its systematic understanding is insufficient due to divergent research results. To further understand the research advances of the DAS technology in geophysical exploration for more effective subsequent research, this study systematically classified and summarized the development history of the DAS technology and its recent research results in geophysical exploration based on the oil and gas, marine, and environmental engineering application scenarios through literature research. This study focused on the development process of the DAS technology in different directions, the research advances in data processing, and relevant literature with specific results. Finally, this study generalized the development trend and urgent problems of the DAS acquisition system, analyzing the DAS development prospect.

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A review of thirty years of airborne geophysical surveys in the Qiangtang Basin and future prospect
ZHOU Dao-Qing, XIONG Sheng-Qing, WANG Bao-Di, CAO Bao-Bao, GUO Zhi-Hong, HU Yue, ZHENG Yu-Zhou, ZHAO Rui, WEI Yan-Yan, XIAO Meng-Chu, HU Xia-Wei, YAN Qiao-Juan
Geophysical and Geochemical Exploration    2024, 48 (2): 287-295.   DOI: 10.11720/wtyht.2024.1413
Abstract240)   HTML15)    PDF (7354KB)(311)      

Airborne geophysical surveys, characteristic of being green, economical, efficient, and subjected to less influence by surface factors, serve as the one of most effective means of basic surveys and scientific research on the Qinghai-Tibet Plateau. This study reviewed the progress in the airborne geophysical surveys in the Qiangtang Basin of the Qinghai-Tibet Plateau in the past thirty years, systematically summarizing the progress and geological interpretation results of comprehensive airborne geophysical surveys in the basin. Furthermore, this study presented research progress and understanding of major basic geological issues of the basin, such as the basin's boundaries, central uplift zone, basement properties, deep structures, and cover characteristics, as well as the identification of favorable structural areas for oil and gas exploration. Finally, based on an analysis of the developmental trends of airborne geophysical surveys in the Qiangtang Basin, this study proposed opinions and suggestions for key research directions in the future.

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Comparison and summary of different azimuthal anisotropy-based inversion techniques
LIANG Zhi-Qiang, LI Hong
Geophysical and Geochemical Exploration    2024, 48 (2): 443-450.   DOI: 10.11720/wtyht.2024.1251
Abstract235)   HTML3)    PDF (3440KB)(208)      

The progress in seismic acquisition techniques characterized by wide azimuths,wide frequency bands,and high densities has greatly promoted the application of the prestack P-wave fracture inversion technique based on the azimuthal anisotropy theory.Azimuthal anisotropy-based inversion can yield the azimuths and intensities of fractures.However,different inversion techniques yield different parameters for fracture intensity characterization,resulting in inconsistent inversion results.Consequently,the azimuthal anisotropy-based inversion results of fractures are non-unique,leading to confusion about accurate results.Based on the Thomsen anisotropy theory,as well as the interrelationships between fracture models(the Hudson coin model and the Schoenberg linear sliding model),this study established the connections of anisotropic parameters between different fracture inversion techniques(VVAZ,Ruger's approximation,and Fourier series),presenting the real meanings and mathematical expressions of results from different azimuthal anisotropy-based fracture inversion techniques.Additionally,this study summarized the relationships of parameters between different inversion techniques and fracture models,further deepening the research on azimuthal anisotropy-based fracture inversion.This study lays solid theoretical and technical foundations for large-scale fracture detection based on the seismic data obtained using the seismic acquisition techniques featuring wide azimuths,wide frequency bands, and high densities.

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Application of comprehensive geophysical prospecting in exploration of the Duhu copper deposit in Xinxing County
HE Jun-Fei
Geophysical and Geochemical Exploration    2024, 48 (2): 375-381.   DOI: 10.11720/wtyht.2024.1101
Abstract222)   HTML11)    PDF (5778KB)(287)      

Since individual geophysical exploration methods suffer the multiplicity of solutions, comprehensive geophysical prospecting has been extensively applied in deep ore prospecting presently. This study conducted the geological exploration of the Duhu porphyry copper deposit in Xinxing County using multiple geophysical methods such as high-precision magnetic survey and controlled source audio-frequency magnetotellurics (CSAMT). It was inferred that the CSAMT-derived medium-low resistivity anomalies and the low-gentle anomalies derived from the high-precision magnetic survey serve as significant prospecting indicators. Satisfactory results were achieved in follow-up verification of the anomalies. Specifically, copper, molybdenum, silver, and gold mineralized bodies with a cumulative thickness of 178.2 m were identified in a 1 000 m deep borehole, with the highest copper grade of 1.45%. The application of comprehensive geophysical prospecting holds great significance in guiding the exploration of porphyry copper deposits in western Guangdong.

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New progress in the technology and applications of SOTEM
XUE Guo-Qiang
Geophysical and Geochemical Exploration    2024, 48 (5): 1165-1168.   DOI: 10.11720/wtyht.2024.0325
Abstract208)   HTML8)    PDF (380KB)(257)      

The artificial source electromagnetic method is an important technique for deep resource exploration. The key challenge is to improve the depth and precision of detection through innovative technology. The detection mode of electromagnetic methods is evolving from far-field to near-field, and the study of near-source electromagnetic methods has become an international research frontier in recent years. Building on the recent advancements in wide-field electromagnetic methods and multi-channel transient electromagnetic methods, the short-offset transient electromagnetic method (SOTEM) has been further developed and proposed. The distinguishing features of SOTEM are its stronger signals and wider bandwidth, which are advantageous for achieving the detection requirements of greater depth and higher precision. This special issue presents eight articles covering the methods, techniques, software, and applications of SOTEM, providing strong support for the growing need for high-resolution subsurface detection.

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Critical factors in microtremor-based exploration at a depth of thousands of meters
QI Juan-Juan
Geophysical and Geochemical Exploration    2024, 48 (3): 777-785.   DOI: 10.11720/wtyht.2024.1358
Abstract198)   HTML3)    PDF (6323KB)(285)      

To explore the critical factors influencing the results of microtremor-based exploration at a depth of thousands of meters,this study conducted experiments using triangular arrays based on spatial autocorrelation(SPAC) and extended SPAC(ESPAC).Focusing on factors such as array size,acquisition unit frequency,and acquisition duration,this study explored the frequency band ranges corresponding to different array sizes,the arrangement of arrays in kilometer-depth exploration for obtaining both deep and shallow data,and the improvement in deep resolution.Based on the analysis and discussion results,this study established a parameter-setting system to improve the accuracy of exploration at a depth of thousands of meters.

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Application of high-density electrical resistivity tomography and audio magnetotellurics for groundwater exploration in the karst area in southwestern China
XIA Shi-Bin, LIAO Guo-Zhong, DENG Guo-Shi, YANG Jian, LI Fu
Geophysical and Geochemical Exploration    2024, 48 (3): 651-659.   DOI: 10.11720/wtyht.2024.1237
Abstract187)   HTML7)    PDF (5894KB)(288)      

Huize County of Yunnan Province is situated in the karst area in southwestern China, where karst groundwater is its primary water source. To conquer local difficulties in drinking water, this study constructed a conceptual model of groundwater occurrence by fully investigating the hydrogeological conditions of the Huize area. Moreover, this study evaluated the applicability and optimal combination of geophysical methods based on the measurement results of petrophysical properties. According to the actual local needs, this study deployed a comprehensive profile combining high-density electrical resistivity tomography (HDERT) and audio magnetotellurics (AMT) in Tuogu Village, Huize County. The groundwater enrichment site was delineated relying on resistivity anomalies, effectively guiding the layout of boreholes. The boreholes achieved the maximum single-borehole water yield of 20.76 m3/d, thus effectively alleviating the local drinking water problem. The HDERT-AMT combined exploration method proves to be optimal for prospecting for groundwater in carbonate rock areas. HDERT can accurately characterize weathered layer thicknesses, bedrock boundaries, fissure evolutionary degrees, and water-bearing properties of strata, constraining groundwater recharge channels, thus counteracting AMT's defects for identification of near-surface stratigraphic structures. AMT can accurately reflect the spatial structures of fracture zones and the macrostructures of strata, limiting the boundary conditions (aquicludes) of water-bearing structures, thus making up for the defects of insufficient detection depths of HDERT in high-resistivity stratigraphic regions. HDERT and AMT, which are complementary to each other in terms of accuracy and depth, can be applied to identify and constrain the spatial occurrence conditions of groundwater migration, storage, and enrichment.

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Research and application of the log-based comprehensive identification method for low-contrast oil layers:A case study of the Lufeng oilfield in the Pearl River Mouth Basin
LIU Wei-Nan, GUAN Yao, LIU Dao-Li, SHI Lei, SONG Wei
Geophysical and Geochemical Exploration    2024, 48 (3): 573-583.   DOI: 10.11720/wtyht.2024.1164
Abstract181)   HTML14)    PDF (7267KB)(174)      

The accurate identification of fluid properties is critical for reservoir evaluation.However,for the Paleogene low-porosity and low-permeability reservoirs in the Lufeng area,Pearl River Mouth Basin,the low contrast between oil and water layers in conventional logs due to the presence of high-resistivity water layers complicates the identification of oil and water layers.This study first ascertained the reservoir characteristics and genetic analysis of low-contrast oil layers.Then,it developed the Flair gas logging response equation and the Flair logging response correction method,aiming to overcome the challenge that gas logging response values of low-porosity and low-permeability reservoirs are significantly influenced by factors such as drilling rate and porosity.Given the differences in the properties and components of various fluids,this study constructed new oil-bearing and water-content indices using Flair gas logging curves.Moreover,this study characterized the geochemical chromatogram using a gamma probability distribution function and extracted the shape and scale factors to describe the chromatogram characteristics.Based on sensitivity parameters,this study plotted the characteristic parameter-based fluid property identification chart.The practical application shows that the log-based comprehensive fluid property identification method can yield satisfactory effects,achieving a compliance rate of 91.3%.Therefore,this method can be popularized.

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Research on the detection of underground pedestrian passage by high precision gravity exploration
YANG Min, XU Xin-Qiang, CHEN Ming, Ji Xiao-Lin, WANG Wan-Yin, ZHAO Dong-Ming, ZHOU Wei, ZHANG Yi-Mi
Geophysical and Geochemical Exploration    2024, 48 (3): 876-883.   DOI: 10.11720/wtyht.2024.0047
Abstract179)   HTML10)    PDF (3819KB)(229)      

Underground cavities with shallow burial and small scale are difficult to detect. With the development of gravity sensing technology, the accurate and rapid acquisition of micro-gravity variations brings new opportunities for detecting underground cavities, and it has wide research and practical value for the detection of small-scale underground cavities. This paper systematically analyzes and studies underground cavities from three aspects: gravity basic theory, gravity detection technology, and gravity data processing and inversion. Under given body size and gravity data accuracy, the maximum burial depth of gravity detection is calculated using the bisection method. High-density acquisition and high-precision gravity detection methods are applied to the actual detection of an underground pedestrian tunnel in a certain area of a passenger station. A set of high-precision gravity grid data is obtained. The theoretical research and measurement results indicate that existing gravity instruments have the ability to detect underground cavities. By using the minimum curvature potential field separation method, 2.5D interactive inversion and the target area recognition three-dimensional physical property fast inversion method, the approximate SN distribution and burial depth of the underground pedestrian tunnel are obtained, which is approximately 2.5~5 m, consistent with the actual situation. This study has developed a complete gravity exploration process for detecting underground cavities, and it has certain reference value.

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Multi-source frequency-domain seismic exploration technique and its application
SUN Hong-Lin, LIU Tie-Hua, LIU Tie, ZHANG Zhan-Rong, CHEN Zhi-Xing
Geophysical and Geochemical Exploration    2024, 48 (3): 618-628.   DOI: 10.11720/wtyht.2024.1317
Abstract171)   HTML3)    PDF (5836KB)(238)      

Due to various strong electromagnetic mechanical interference and traffic barriers, many geophysical exploration techniques are ineffective in urban geophysical exploration.Based on transient surface waves,microtremor arrays,and microtremor spectral ratios,this study synthetically extracted two kinds of characteristic curves for joint inversion from the multi-source frequency-domain seismic data obtained by multi-point three-component low-frequency sensors.Consequently,this study achieved multi-source frequency-domain seismic exploration that integrated three techniques and developed the two-source synthetic dispersive spectrum extraction technique,the two-source characteristic curve joint inversion technique,and the equivalent homogeneous medium forward modeling technique based on inhomogeneous media.Engineering practice results demonstrate the improvements in the exploration accuracy and efficiency.

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Sulfur isotopic composition and related issues of typical gold ore districts in China
LAN Rui-Xuan, ZHAO Hong-Kun, TANG Shi-Xin, DUAN Zhuang, MA Sheng-Ming
Geophysical and Geochemical Exploration    2024, 48 (2): 296-313.   DOI: 10.11720/wtyht.2024.1177
Abstract162)   HTML9)    PDF (5941KB)(217)      

In the Prospecting Breakthrough Strategy (2011~2020), China has made significant progress in the exploration of gold deposits, demonstrating considerable prospecting potential. Element sulfur, a mineralizer, is closely associated with the formation of gold deposits, proved to be the most significant element in gold deposit formation by scholars at home and abroad. Sulfur isotopes have been extensively used to trace the sources of minerals in gold deposits. Different gold deposits reside in distinct geological settings. Since sulfur isotopic compositions are governed by various sulfur sources, sulfur isotopes in gold deposits can reflect the geological settings of mineralization. The ore-district-scale spatio-temporal distribution of sulfur isotopes has theoretical implications, playing a significant role in guiding ore prospecting. The gold resources in China are distributed in 42 gold ore districts, typified by Jiaodong, Xiaoqinling, and Yunnan-Guizhou-Guangxi. This study comparatively analyzed and summarized the characteristics of sulfur isotopes in the three typical gold ore districts, providing theoretical and methodological support for future gold prospecting.

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Fine-scale prospecting targets of skarn iron deposits in the Pandian gravity-magnetic anomaly zone of northwestern Shandong Province: Insights from deep prospecting using the wide-field electromagnetic method
GUO Guo-Qiang, LI Ya-Dong, WANG Yang, YU Jia-Bin, WANG Run-Sheng, GAO Xiao-Feng, ZHANG Da-Ming, HU Dong-Ning, FANG Lei, GUO Wei-Fang
Geophysical and Geochemical Exploration    2024, 48 (2): 327-333.   DOI: 10.11720/wtyht.2024.1157
Abstract160)   HTML5)    PDF (4258KB)(286)      

Significant aeromagnetic and gravity anomalies were found in the ultra-deep coverage zone of the Pandian area in the northwestern Shandong Province. Through systematic verification of gravity and magnetic anomalies, a breakthrough in prospecting for deep skarn iron deposits has been achieved through several boreholes around the Pandian gravity-magnetic anomaly zone. However, the gravity-magnetic anomaly zone spreads extensively and its characteristics cannot directly indicate the prospecting target, thus some boreholes failed to find ores or revealed poor ore-finding conditions. Hence, to accurately delineate the ore-forming location in the gravity-magnetic anomaly zone and achieve a further breakthrough in ore prospecting, this study conducted the wide-field electromagnetic (WFEM) sounding in the verified Pandian gravity-magnetic anomaly zone. Combining the drilling verification, this study delineated the deep ore-forming interval of skarn iron deposits in the deep coverage zone and the favorable structural plane for ore-forming, suggesting the deep fine-scale prospecting targets.

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Stream sediment geochemistry and prospecting targets in Harper, Liberia
BAI Yang, CHEN Kai-Xu, CHEN Chong, LI Fu-Lin, ZHANG Ji-Chun, WEI Ling-Xiao, SI Ke-Fu, ZHENG Xiong-Wei, HU Yun-Fei, WU Ying, ZHANG Yuan-Pei
Geophysical and Geochemical Exploration    2024, 48 (2): 382-392.   DOI: 10.11720/wtyht.2024.1128
Abstract153)   HTML2)    PDF (8370KB)(183)      

Birimian rocks, the most significant Au ore-forming rocks in western Africa, are widespread in Harper, southeastern Liberia. As indicated by the geochemical parameters from the 1∶250 000 stream sediment survey of this region, elements Au and Hg exhibit high enrichment and high differentiation while element As manifests enrichment and high differentiation. These findings suggest considerable potential for Au prospecting. Based on the correlation analysis of elements, this study selected factors F1 (for the Au-Hg-Pb-Sn association) and F2 (for the As-Sb-W association) to effectively guide the exploration of gold deposits. Thirteen composite anomalies were delineated by extracting the anomaly information of Au, Hg, As, and Sb from the two principal factors, effectively reflecting the anomaly distributions of different gold deposits or ore occurrences. The geological and mineral surveys in anomaly areas reveal that areas HS1-HS3 and HS12-HS13 with composite anomalies characterized by directional distribution and high intensities show distinct Au mineralization information. Based on this, two major Au prospects, i.e., Seethum New and Behwan, have been identified for further detailed exploration.

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Distribution patterns of the electromagnetic fields of orthogonal horizontal magnetic dipoles as sources in CSRMT
CHEN Xing-Peng, WANG Liang, LONG Xia, XI Zhen-Zhu, QI Qing-Xin, XUE Jun-Ping, DAI Yun-Feng, HU Zi-Jun
Geophysical and Geochemical Exploration    2024, 48 (3): 721-735.   DOI: 10.11720/wtyht.2024.1395
Abstract152)   HTML2)    PDF (7800KB)(159)      

Controlled source radio-magnetotellurics (CSRMT) measurements typically use artificial field sources transmitting at frequencies ranging from 1 to 1 000 kHz. Among the many transmitting sources of the artificial source electromagnetic method, the orthogonal horizontal electric dipole source and the orthogonal horizontal magnetic dipole source are preferred field sources for tensor resistivity measurements. Hence, using the analytical formulas for electromagnetic fields based on the horizontal electric dipole source and the horizontal magnetic dipole source, this study calculated the electromagnetic fields based on the orthogonal horizontal electric dipole source and the orthogonal horizontal magnetic dipole source in the homogeneous half-space model. The results show that: (1) The displacement current needs to be considered at transmitting frequencies above 100 kHz; (2) The effects of displacement current on the tensor apparent resistivity and the impedance phase can be ignored in the far zone; (3) With a constant model resistivity and varying distances between transmitter and receiver, model calculations indicate a larger measurement range in the far zone of the high-frequency electromagnetic field; (4) With a constant distance between transmitter and receiver and varying model resistivities, model calculations suggest that the far-zone range of the electromagnetic field is significantly influenced by resistivity, and that the high-resistivity model requires higher frequencies for achieving far-zone observation conditions.Compared with the electric dipole source, the magnetic dipole source exhibits smaller deviations on the tensor apparent resistivity and impedance phase with the actual value, which is more suitable for geological analysis.

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Petrogenesis and rubidium enrichment indication of the Fuling rock mass in southern Anhui Province
ZHANG Jun, TAO Nai, QI Shang-Xing, WANG Zhi-Qiang, DA Hao-Xiang
Geophysical and Geochemical Exploration    2024, 48 (3): 584-596.   DOI: 10.11720/wtyht.2024.1268
Abstract143)   HTML8)    PDF (7620KB)(153)      

The Fuling rock mass in southern Anhui Province, located in the eastern section of the Jiangnan uplift zone, is a complex granitic rock mass that has experienced multi-stage evolution. It primarily comprises two lithologies: Monzogranite and K-feldspar granite. By investigating the geological, petrographic, and petrogeochemical characteristics of the Fuling rock mass, this study delved into its evolutionary characteristics, genetic types, and tectonic environment, aiming to clarify its indication significance for rubidium enrichment. The results of this study are as follows: ① The geochemical characteristics of the Fuling rock mass demonstrate high SiO2, Na2O, K2O, and Al2O3 contents, high w(K2O)/w(Na2O) ratios, and aluminum saturation indices (A/CNK) ranging from 0.95~1.08 (average: 0.99), suggesting high-K calc-alkaline quasi-aluminous to peraluminous granites; ② In terms of trace elements, the Fuling rock mass possesses high Li, Rb, Nd, and Ta contents and significantly low Sr and Ba contents, which may be associated with the fractional crystallization of feldspar; ③ The w(Nb)/w(Ta) ratios ranging from 5.71~10.94 (average: 8.41) and Mg# values ranging from 0.02~0.31 (average: 0.13) indicate that the Fuling rock mass was primarily derived from the partial melting of lower crust rocks, suggesting A-type granites in a non-orogenic extensional environment; ④ The Rb content in the Fuling rock mass increases with the magmatic evolution degree. Compared to monzogranites, K-feldspar granites with a higher evolution degree display higher Rb content, implying that the Rb content in the Fuling rock mass is generally controlled by magmatic evolution. Overall, this study holds some reference significance for understanding the Yanshanian diagenesis and mineralization of southern Anhui Province.

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A method for identifying lithology based on a feature-weighted KNN model
GUO Yu-Shan, WANG Wan-Yin
Geophysical and Geochemical Exploration    2024, 48 (2): 428-436.   DOI: 10.11720/wtyht.2024.1260
Abstract142)   HTML1)    PDF (4553KB)(136)      

Lithology identification, as a major geological task, strongly underpins the exploration of solid minerals, oil, and gas. Since the physical properties of rocks bridge lithologies and geophysical fields, their differences can be used for lithology identification. However, the physical property data of different rocks frequently overlap to some extent, posing challenges to accurate lithology identification using cross plots alone. The K-nearest neighbor (KNN) model is suitable for multi-class classification since it is a simple and direct machine learning method with high accuracy and sensitivity. This study introduced a feature-weighted KNN model for lithology identification. In this model, different weights were assigned to different features by combining the conventional KNN model with the information gain of attribute features. This allowed for intuitive reflection of the importance of attribute features to classification. Experiments show that compared to the conventional KNN model, the feature-weighted KNN model can more significantly identify lithologic boundaries, thus improving the overall accuracy and stability of lithology identification.

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Application of the cross-borehole resistivity method in the monitoring of leakage for urban water supply pipelines
ZHANG Wei, ZHOU Yu-Kun, LIU Li-Yan, CHEN Jun-Liang
Geophysical and Geochemical Exploration    2024, 48 (3): 884-890.   DOI: 10.11720/wtyht.2024.1368
Abstract132)   HTML4)    PDF (3195KB)(163)      

Urban main water supply pipelines are mostly buried along roads. Large pipe diameters and deep burial depths make it hard to detect their leakage in the early stage. Their leakage will severely influence urban traffic and residents' daily life. Hence, the leakage monitoring of water supply pipelines is particularly important. However, factors such as dense traffic lines, hardened road surfaces, and electromagnetic interference limit the application of the ground resistivity method and geological radars in pipeline monitoring. To make up for the shortcomings of existing monitoring methods, this study explored the cross-hole resistivity method for pipeline leakage monitoring. First of all, pipelines with and without leakage were simulated using forward modeling and inversion methods, analyzing the detection characteristics of the cross-borehole resistivity method. Then, electrode materials and burial methods were examined through experiments, solving the problems of electrode corrosion and weak electric field signals. Finally, an experimental site was set up near a water supply pipeline in Beijing, obtaining multi-phase monitoring data using the cross-borehole resistivity method. Through comparative analysis of multi-phase resistivity sections, this study analyzed the changes in pipeline leakage, delineating the leakage influence scope, which was verified by the leakage data from the waterworks. The satisfactory monitoring results suggest that the method proposed in this study can be referenced for similar pipeline leakage monitoring in cities.

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Data integration based on MapGIS and ASCII code files
ZHAO Hong-Yan, LI Cong, CHANG Qiu-Ling, GUAN Xiao-Rong, DU Cheng-Yuan, CHEN Xin, WANG Jing
Geophysical and Geochemical Exploration    2024, 48 (3): 804-811.   DOI: 10.11720/wtyht.2024.1367
Abstract130)   HTML4)    PDF (3914KB)(150)      

Data integration based on MapGIS includes data conversion, data normalization, data fusion, and related research. A synthesis of existing research suggests that data conversion has been intensively studied, while there is a lack in studies of data normalization and data fusion. This study improved the data normalization method based on the complex and extensively applied geological maps, achieving the normalized annotation and color filling for thousands of geobodies at one time. A technical process for data fusion was established by analyzing the applicable conditions of various commonly used methods for data fusion and making some supplementation. Besides, ASCII code files were prepared for mapping small coal pillars in batches. The results of this study show that improving the data normalization method, establishing the technical process for data fusion, and making full use of ASCII code files can significantly enhance the efficiency of data integration and broaden the mind for problem solving.

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Practices and future research directions of geophysical exploration for normal-pressure shale gas in complex structural areas,southeastern Chongqing
HE Xi-Peng, LIU Ming, XUE Ye, LI Yan-Jing, HE Gui-Song, MENG Qing-Li, ZHANG Yong, LIU Hao-Juan, LAN Jia-Da, YANG Fan
Geophysical and Geochemical Exploration    2024, 48 (2): 314-326.   DOI: 10.11720/wtyht.2024.1202
Abstract129)   HTML7)    PDF (7986KB)(297)      

Southern China boasts great potential for normal-pressure shale gas resources,with distribution areas primarily including the peripheral complex structural areas and the extrabasinal fold belts of the Sichuan Basin.These areas exhibit intricate surface and subsurface geological conditions,leading to poor seismic acquisition quality,low imaging accuracy,and unclear varying patterns of sweet spot parameters.This study systematically summarized the research achievements and technical advances in the seismic acquisition,image processing,and reservoir prediction for normal-pressure shale gas in southeastern Chongqing,including:①The development of variable-density 3D observation system design technique and the seismic excitation and reception technique for complex mountains with limestone surfaces,ensuring sufficient sampling of the reflected wave field in complex subsurface structures and improving data quality and construction efficiency;②The optimization of prestack seismic preprocessing technique for complex mountains,imaging techniques for complex structures in basin-margin transition zones, and imaging techniques for synclinal structures in extrabasinal fold belts,achieving resulting profiles with high signal-to-noise ratios,wide effective frequency bands,and high structural imaging accuracy;③The quantitative prediction of the thickness,formation pressure coefficient,and brittleness of high-quality shales based on research on petrophysical characteristics;the quantitative prediction of the organic carbon content,gas content,and porosity of shales based on statistical petrophysics;the quantitative prediction of fractures formed due to the superimposed effect of multi-stage structural modifications based on the paleo-stress field evolution revealed using the finite element simulation technique;and the ascertainment of the distribution patterns of the current in-situ stress field using the current stress field prediction technique developed using the combined spring model.The above breakthroughs have effectively guided the sweet spot prediction,exploration,and production of normal-pressure shale gas,providing a basis for the discovery of the Nanchuan normal-pressure shale gas field.Subsequent research should focus on more scientific and reasonable seismic acquisition techniques based on seismic reception using 5G wireless nodes,high-precision automatic image processing technologies for high-steep structures in complex mountains,and integrated geology-engineering-economy seismic evaluation methods for sweet spots.

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An experimental study on the influence of step topographies in strip mines on the exploration performed using the high-density resistivity method
ZHAO Zi-Hao, LI Peng-Hui, LYU Hai-Jian, KANG Sen
Geophysical and Geochemical Exploration    2024, 48 (2): 565-572.   DOI: 10.11720/wtyht.2024.3503
Abstract127)   HTML2)    PDF (4709KB)(205)      

The stability assessment of strip mine slopes is a fundamental means to prevent slope accidents. To investigate the influence of step topographies on the exploration using the high-density resistivity method on strip mine steps, this study conducted flume experiments for simulation using similar materials to explore the current field distribution in the profile to be surveyed. The experimental results show that: (1) The shallow positions near the upper and lower slope lines and the breadth line of the cleaning berm exhibited high current densities and even current distributions; (2) The middle positions manifested sharply changed current densities, with their contours akin to the step topography; (3) The deep positions displayed low current densities and tardy current changes; (4) A significant current gathering effect was observed near the slope bottom line on the profile; (5) Compared to flat topographies, step topographies exhibited high current densities and uneven current distributions. This suggests that in the exploration using the high-density resistivity method, step topographies in strip mines can cause abnormal inversion results for the middle positions and positions near the slope bottom line.

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Application of comprehensive geophysical prospecting in the exploration of geothermal resources in the Linjiadi area, Aohan Banner, Inner Mongolia
HAN Shu-He, PEI Qiu-Ming, XU Jian, SONG Zhi-Yong, MO Hai-Bin
Geophysical and Geochemical Exploration    2024, 48 (4): 962-970.   DOI: 10.11720/wtyht.2024.1315
Abstract125)   HTML2)    PDF (4495KB)(157)      

In the context of the goals of both peak carbon dioxide emissions and carbon neutrality, scientific and efficient exploration and exploitation of geothermal resources are criticalfor the geothermal industry. To address the commonly concernedtechnical challenges in the exploration of moderately deep geothermal resources, this study investigated the effectiveness of comprehensive geophysical prospecting in the exploration of geothermal resources inthe Linjiadi area, Aohan Banner, Inner Mongolia. Based on the analysis ofthe geological and hydrogeological conditions, this studypreliminarilyascertainedthe geothermal field characteristicsand the hydrochemicalcharacteristics of groundwater in the Linjiadi area. By comprehensively employingcontrolled source audio-frequency magnetotellurics (CSAMT), CSAMT; microtremor survey; radioactive radon survey; this study roughly determined the distribution of strata, magmatic rocks, and fault structures in the study area, inferring the factors controllinggeothermal anomaly areas and hot-water migration.Accordingly, exploration boreholes were arranged, allowing for drilling verificationwith a total length of 960 m. The results show that the comprehensiveapplication of CSAMT and microtremor survey, combined with radioactive radon survey for auxiliary verification, is effective in exploringmoderately deep geothermal resources. This study will provide a methodological reference for geothermal resource exploration in other areas.

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Metalleogenic geochemistry:Science problems and research ideas
XI Xiao-Huan
Geophysical and Geochemical Exploration    2024, 48 (4): 891-917.   DOI: 10.11720/wtyht.2024.0282
Abstract124)   HTML5)    PDF (791KB)(168)      

In geoscientific field, the essential object of all the research problems is the physical world which is derived from the crust-mantle interaction and has deeply influenced globally the environment and resources. The metallogenic geochemical theory believes that the metallogenic materials are the internal factors for the metallogenic system to influence the metallogenic process, and taking metallogenic materials as the main body to study the problems of metallogenic materials and metallogenic processes is the basic meaning of the metallogenic geochemical theory, and the core subject of the studies of metallogenic rules and theories. During the mineralization process of metallogenic system, metallogenic materials formed into metallogenic series of corresponding scale. This paper outlines several scientific topics of the metallogenic geochemical studies, among which, the topic of global metallogenic system mainly studies the metallogenic processes and relations of the series of metallogenic regions, provinces and belts formed by metallogenic materials in the context of global metallogenic process; the topic of regional metallogenic system mainly studies the metallogenic processes and relations of ore field series in the context of regional metallogenic process; the topic of ore field metallogenic system mainly studies the metallogenic processes and relations of mineral deposit series in the context of ore field metallogenic process; the topic of mineral deposit metallogenic system mainly studies the metallogenic processes and relations of ore-body series in the context of mineral deposit metallogenic process. The basic research ideas concerning above mentioned studies are discussed in this paper, including the metallogenic materials' geneses and sources, migration and evolution, differentiation and concentration, as well as the zoning relations of each level's metallogenic system and series of the world during the metallogenic processes. The purpose is to summary the metallogenic rules, explore the metallogenic mechanism and guide the mineral resources exploration. Supported by modern technologies and methods of IT(information technology), modeling and AI(artificial intelligence), the metallogenic geochemical theory uses the earth system scientific ideas to study the problems of metallogenic system and metallogenic series, construct the theoretical framework for metallogenic geochemical research, and provide a theoretical basis for the mineral resources exploration, evaluation and development technics and methods.

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Determining double-layer goafs in coal mines using CSAMT-derived apparent resistivity and impedance phase
QIN Chang-Chun, NIU Zheng, LI Jing
Geophysical and Geochemical Exploration    2024, 48 (3): 690-697.   DOI: 10.11720/wtyht.2024.1338
Abstract120)   HTML5)    PDF (4081KB)(212)      

The goaf and subsidence areas formed ue to the mining of subsurface coal seams can cause damage to surrounding ecological environments.At present, the detection effects of double-layer goafs in coal mines, especially the second-layer goafs, are unsatisfactory. In response to this challenge, this study delineated goafs using apparent resistivity and impedance phase derived from the data acquired by an efficient controllable source audio-frequency magnetotelluric instrument. In the case of a shallow water-bearing goaf with low resistivity, the apparent resistivity displays shadow effects, leading to an extended abnormal range of the upper target, which is unfavorable to the identification of the lower high-resistivity goaf. In contrast, the impedance phase, exhibiting minor shadow and static effects, shows a significant response to the lower goaf. As indicated by the theoretical model testing results, the combination of apparent resistivity and impedance phase can effectively determine shallow water-bearing goafs and deep unfilled high-resistivity goafs. This combination method was employed to interpret the double-layer goaf in the Shenfu mining area of the Jurassic coal field in northern Shaanxi, achieving satisfactory results through the mutual verification of the two parameters. Engineering verification results indicate that this method demonstrates reliable inference and expected exploration effects. Overall, this method provides a new approach for CSAMT-based inference and interpretation in the exploration of double-layer goafs in coal mines, thus holding critical technical promotion and reference significance.

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REE geochemical anomalies in soils of the Ximeng-Lancang area in southwestern Yunnan and their discovery and their implications for ore prospecting
XIE Kui-Rui, SONG Xu-Feng, ZHOU Kun, ZHOU Yu-Guo, SHE Zhong-Ming, TANG Jian
Geophysical and Geochemical Exploration    2024, 48 (3): 660-667.   DOI: 10.11720/wtyht.2024.2014
Abstract120)   HTML3)    PDF (2521KB)(152)      

The Ximeng-Lancang area in southwestern Yunnan resides in the southern section of the Nujiang-Lancangjiang-Jinshajiang orogenic belt in Southwest China. The 1∶50,000 geochemical soil survey revealed 24 rare-earth-element (REE) geochemical anomalies, which are primarily distributed in the Carboniferous Pingzhang Formation mafic volcanic rocks and the Carboniferous-Permian Yutangzhai Formation sedimentary carbonate rocks within and near the Changning-Menglian deep fault zone. Furthermore, the AP00 REE geochemical anomalies ranking high in the evaluation were analyzed in detail through a 1∶10,000 geochemical soil survey, a 1∶10,000 special geological survey, and light-duty prospecting engineering in mountainous areas. A new type of REE ores in weathering crusts has been first discovered in sedimentary carbonate strata, with preliminarily estimated REE resources reaching a medium scale, suggesting a prospecting breakthrough. This finding shows a new prospecting approach, which can be referenced for similar research. As revealed by a comprehensive analysis of the regional geological and geochemical settings and the data of AP00 REE anomalies, the AP00 REE ores in weathering crusts have undergone a gradual enrichment and mineralization process involving four different geological processes, suggesting polygenetic compound REE ores. Considering the low leaching efficiency of AP00 REE ores and significant structural (magmatic) superimposed mineralization of the heavy REE yttrium, it is inferred that yttrium-dominated primary REE ores might exist in the deep part, implying high potential for heavy-REE ores.

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Analysis of critical parameters in the field acquisition of short-offset transient electromagnetic data
CHEN Wei-Ying, XUE Guo-Qiang, LI Hai
Geophysical and Geochemical Exploration    2024, 48 (5): 1169-1175.   DOI: 10.11720/wtyht.2024.1197
Abstract119)   HTML3)    PDF (2409KB)(147)      

The grounded-source short-offset transient electromagnetic (SOTEM) method involves many parameters in field data acquisition. The selection of these parameters is closely associated with the signal quality and detection sensitivity of measured data. Based on the relevant provisions in the organization standard, Technical specification for grounded-source short-offset transient electromagnetic method (T/CGS 002—2021), issued by the Chinese Geophysical Society, numerical emulations, and practical cases, this study analyzed and expounded the selection criteria of critical parameters like transmitting source length, transmitting fundamental frequency, offset, device type, and observation component. The insights obtained in this study are significant for guiding the field construction of the SOTEM device and leveraging its detection performance.

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Geophysical identification of Cretaceous reservoirs in the Shinan area, Junggar Basin
LI Lu-Lu, JIANG Guo-Yu, LIU Tao, HE Yan, ZHANG Yong-Bo
Geophysical and Geochemical Exploration    2024, 48 (2): 334-341.   DOI: 10.11720/wtyht.2024.1077
Abstract115)   HTML4)    PDF (7477KB)(192)      

Industrial oil flows have been successively obtained from the basal conglomerates of the Cretaceous Qingshuihe Formation in the Shinan area, Junggar Basin. However, this set of reservoirs exhibits multi-layer three-dimensional oil-bearing properties and significant vertical and horizontal variations. Therefore, there is an urgent need to overcome the challenge of the identification and fine-scale characterization of reservoirs. Based on the accurate calibration of seismic and geological horizons, this study reconstructed the paleogeomorphology of the first member of the Cretaceous Qingshuihe Formation using based on the seismic flattening and residual thickness methods in three steps. By combining the reservoir prediction through natural gamma-ray pseudo-acoustic wave inversion, this study roughly identified the predominant factors controlling sedimentation and the spatial distributions of sand bodies. The results of this study provide an effective method combination for predicting Cretaceous reservoirs in the Shinan area. Furthermore, these results offer a sufficient scientific basis for oil and gas exploration in the glutenite reservoirs of the Cretaceous Qingshuihe Formation, thus effectively reducing the exploration risk.

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Analysis of soil heavy metal influencing factors and sources in typical small watersheds in shallow mountainous area
SHI Jing-Tao, LIU Jun-Jian, ZHANG Jun-Chao, WANG Jiang-Yu-Long, JIANG Yu-Ge, WANG Mo, LI Heng-Fei, YANG Wen-Hao, YAN Xiang-Jin
Geophysical and Geochemical Exploration    2024, 48 (3): 834-846.   DOI: 10.11720/wtyht.2024.1270
Abstract115)   HTML0)    PDF (6471KB)(135)      

This study investigated the contents of eight heavy metals and related oxides in rocks with different lithologies and the soils formed in the Puhe river basin of Pingquan City. Based on the above investigation, this study analyzed the influencing factors and sources of soil heavy metals in the typical small watershed of the shallow mountainous area, aiming to provide theoretical support for water conservation and ecological restoration in the Beijing-Tianjin-Hebei region. Based on the contents and spatial distributions of soil heavy metals and combined with regional geological setting, this study delved into the influencing factors and sources of heavy metal elements in topsoil, deep soil, and soil parent materials using multiple statistical methods. The results show that heavy metals in topsoil and deep soil exhibited relatively similar contents and coupled spatial distributions. In terms of vertical distributions, the correlation coefficients of heavy metals were negative between topsoil and soil parent materials but positive between deep soil and soil parent materials. As indicated by the results, in the topsoil, elements Cr, Ni, Cu, Zn, and Pb are primarily derived from soil parent materials, while elements Cd, Hg, and As are subjected to the influence of mining. In contrast, the eight heavy metals in the deep soil predominantly stem from soil parent materials, with anthropogenic factors contributing to Cd and As.

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Prospecting potential of medium-fine-grained rock-type lithium resources in the Xianghualing orefield, Hunan Province, China
SONG Zhi-Fang, YANG Qi-Zhi, ZHU Zhen-Zhen, CAO Neng-Wen
Geophysical and Geochemical Exploration    2024, 48 (2): 366-374.   DOI: 10.11720/wtyht.2024.1040
Abstract113)   HTML1)    PDF (6844KB)(168)      

This study aims to explore the distribution characteristics and occurrence patterns of lithium in medium-fine-grained rocks and its paragenetic or associated relationship with minerals such as tungsten, tin, niobium, tantalum, beryllium, and rubidium. Hence, it analyzed the distribution characteristics and diagenetic and metallogenic processes of nonferrous-rare metals in the Xianghualing orefield. With the exposed granitic rock masses as the center, this study divided three ore-forming sections of rare metal lithium, i.e., the Laiziling-Nanjichong, Jianfengling-Xianghuapu, and Tongtianmiao-Yaoshanli ore-forming sections. Moreover, lithium-rich mineralized bodies were discovered in the medium-fine-grained rocks of the former two ore-forming sections. Lithium converges and accumulates in the interior and top of medium-fine-grained granitic rock masses, at the automorphism and alteration positions of high-emplacement apophyses and vein fronts and edges, or in the areas enclosed by silicon-rich quartz veins at the contact zone with silicon-rich surrounding rocks. Dividing these mineralization and alteration sections serves as a crucial approach for exploring medium-fine-grained rock type lithium ore bodies in the Xianghualing orefield.

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Sources of soil heavy metals and health risk assessment of crops in arable land at the periphery of a typical mercury mining area
YU Fei, WANG Rui, ZHOU Jiao, ZHANG Feng-Lei, JIANG Yu-Lian, ZHANG Yun-Yi, ZHU Shi-Lin
Geophysical and Geochemical Exploration    2024, 48 (3): 847-857.   DOI: 10.11720/wtyht.2024.1313
Abstract113)   HTML2)    PDF (3441KB)(133)      

This study aims to systematically assess the pollution risk of heavy metals in the soil-crop-human body system along the periphery of mining areas, thus providing a scientific basis for the classified management of ecological risks and safe crop production in mining areas. Hence, this study examined the soil and crops (rice, corn, and sweet potato) in arable land along the periphery of a typical mercury mining area in Chongqing City. The single-factor pollution index (Pi), Nemero composite index (P), and positive matrix factorization (PMF) model were employed to assess the pollution degree and ecological risk of soil heavy metals for source analysis. Moreover, the human health risk assessment model recommended by the United States Environmental Protection Agency (USEPA) was applied to assess the health risks of local staple crops for residents. The results are as follows: (1) The average contents of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in the soil of the study area were all higher than the topsoil background values of Chongqing and China, suggesting that heavy metals are relatively enriched in topsoil; (2) The single-factor pollution index indicates that the over-limit ratios of Hg and Cd in the soil reached 96.29% and 92.59%, respectively, whereas rice, corn, and sweet potato samples with Cd content exceeding the value specified in the national food safety standard (GB 2762—2022) accounted for 16.67%, 18.75%, and 14.28%, respectively; (3) The Nemero composite index (P) was between 1.17 and 46.05, suggesting mild to heavy pollution in the study area, with heavy pollution primarily located around the mercury mining area and artisanal mercury smelters, as well as the lower reaches of the Rongxi River; (4) The PMF model analysis demonstrates that the heavy metals in the soil of the study area originate from three sources: natural source (47.21%), mining activities (16.00%), and a mixed source of mining and agricultural activities (36.79%). Specifically, Cd, Cr, and Ni are principally affected by the natural source, Hg by mining activities, As and Pb by the mixed source of mining and agricultural activities, and Cu and Zn are associated with the natural source and the mixed source of mining and agricultural activities; (5) The human health risk model reveals that the consumption of rice, corn, and sweet potato poses composite health risks for both adults and children. Rice consumption exhibits the highest risk index, especially in children, with the main risk factors being As and Cd.

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Geophysical forecasting of deep reservoirs in the Z gas field
HE Xian-Ke, LOU Min, LI Bing-Ying, LIU Jiang, HU Wei, CAI Hua
Geophysical and Geochemical Exploration    2024, 48 (3): 609-617.   DOI: 10.11720/wtyht.2024.1352
Abstract113)   HTML2)    PDF (12226KB)(153)      

Fine-scale characterization of reservoirs is critical for oil and gas exploration and production. Reservoirs in the Z gas field exhibit considerable burial depths and superposed sandstone and mudstone impedance characterized by dark spots, complicating their identification using conventional seismic methods. This study achieved the characterization of deep reservoirs in the Z gas field based on the dominant-channel stacking technique. First of all, this study analyzed the seismic response characteristics of deep reservoirs through forward modeling, positing that poor physical properties are the primary factor contributing to the formation of dark spots. Then, starting with the investigation of the near-well prestack gathers of the target layer, this study examined their amplitude variation with offset (AVO) characteristics and seismic phase stability at different angles, determining the dominant-angle seismic channels that can accurately reflect the phase stability of reservoirs. Finally, this study derived a lithology-sensitive 3D data volume through partial stacking of dominant-angle seismic channels, achieving the characterization of deep reservoirs. The near-trace superimposition (3°~15°) of phase-shift seismic data (-90°) allowed for effectively characterized the H3a reservoir in the Z gas field, providing a geophysical basis for subsequent well deployment. Therefore, the dominant-channel stacking technique can effectively characterize the spatial distribution of deep river-channel reservoirs, guiding the reservoir characterization of similar oil and gas fields.

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Deep structural characteristics of the Yagan fault zone in northeastern Ejina Banner, Inner Mongolia: Evidence from magnetotelluric sounding
WANG Wen-Jie, CHEN Lei, LEI Cong-Cong, SHI Xiao-Feng, YANG Biao, WANG Wen-Bao, SUN Da-Peng, XU Hao-Qing
Geophysical and Geochemical Exploration    2024, 48 (3): 640-650.   DOI: 10.11720/wtyht.2024.1478
Abstract107)   HTML5)    PDF (14674KB)(211)      

There exists a continued debate concerning the spatial distribution and deep structural characteristics of the Yagan fault zone in northeastern Ejina Banner, Inner Mongolia. Adhering to the known-to-unknown research approach, this study completed five magnetotelluric sounding (MT) profiles. First, it delved into the relationship between the electrical structure characteristics of a MT profile (MT01) on the west side of the study area and the geological structure information of the Yagan fault zone within the profile. In terms of electrical characteristics, the Yagan fault zone was determined as a resistivity gradient zone characterized by northward dip, high dip angles, and deep depths. Based on these characteristics, and combined with the inversion interpretation results of four MT profiles (MT02~MT05) on the east side, this study identified the deep positions and structural characteristics of the Yagan fault zone within all the MT profiles. Moreover, it determined the major electrical directions of all the MT profiles using the impedance tensor decomposition technique, and the spatial trend of the Yagan fault zone based on the two-dimensional inversion interpretation results. As revealed by the results, the Yagan fault zone within the study area exhibits an overall nearly EW strike at the shallow surface and a strike of NE45° in the deep part, with an average width of approximately 6.8 km. It is a reverse fault with a gradual arc deflection to the north from west to east, manifesting a generally northward dip direction, dip angles ranging from 60° to 67°, and a fault depth of about 20 km. The obtained deep electrical structure model effectively reveals the deep structural characteristics of the study area. providing certain reference significance for the study of regional tectonic evolution

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An observation device based on asymmetric design for high-density resistivity imaging
PANG Yong-Hao, SHEN Zhao-Ang, CHANG Zhi-Xi, LI Guang-Chang, CHEN Mei, XIE Zhi-Wei, WANG Wei
Geophysical and Geochemical Exploration    2024, 48 (3): 786-793.   DOI: 10.11720/wtyht.2024.1454
Abstract106)   HTML0)    PDF (5600KB)(157)      

For the high-density resistivity method, favorable grounding conditions are required to ensure the establishment and measurement of the geoelectric field. Otherwise, unfavorable grounding conditions, like rigid pavement, will prevent some electrodes from being inserted into the ground, leading to the loss of valid data from standard observation devices and reducing the imaging quality. Therefore, this study proposed a method for the fast observation device design. This method supplemented data using an asymmetric quadrupole electrode array according to the spatial positions of missing data's recording points. Numerical simulations show that the method proposed in this study significantly improved the imaging effects of Wenner, Schlumberger, and dipole-dipole arrays, with a second-scale design time. In this study, an observation device based on asymmetric design for high-density resistivity imaging was successfully applied to the embankment detection in Ningbo, reducing the influence of motor lanes on data quality and accurately locating the embankment position.

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Geochemical characteristics and formation mechanism of thermal spring water in the Chuhe fault zone in Anhui Province
WANG Guo-Jian, HU Wen-Hui, LI Guang-Zhi, ZHU Huai-Ping, HU Bin, XIAO Peng-Fei, ZHANG Ying
Geophysical and Geochemical Exploration    2024, 48 (5): 1223-1231.   DOI: 10.11720/wtyht.2024.1145
Abstract106)   HTML4)    PDF (3297KB)(83)      

Several thermal springs associated with tectonic activity occur along the Chuhe fault zone. Except for the Bantang thermal spring at the southern end, other springs along the fault zone exhibit unideal utilization of thermal energy. This affects the development of local industries. Therefore, it is necessary to delve into the geochemical characteristics and formation mechanism of typical thermal springs along the Chuhe fault zone. The purpose is to provide scientific evidence for the rational utilization and exploration methods of geothermal resources in the thermal spring groups in the future. Therefore, this study investigated thermal springs in the Bantang, Zhaoguan, and Xiangquan areas along the Chuhe fault zone, where nine samples of thermal spring water, cold well water, and surface water were collected individually. For these samples, the composition tests of 25 indices, including anions, cations, and major and trace elements, were tested, and the hydrogen and oxygen isotope values were determined. The analyses of the 25 measured indices, along with the investigation of the geothermal water source and controlling factors through hydrogen and oxygen isotope tracing, indicate that the thermal spring water in the three areas tends to be of the CaSO4 type and is all closely related to the interactions between groundwater and surrounding rocks. The thermal spring water, cold well water, and surface water in Bantang and Zhaoguan show consanguinity, with geothermal water being directly recharged with local precipitation and surface water. In contrast, the thermal spring water, surface water, and cold well water in the Xiangquan area show weaker consanguinity, indicating different sources for the underground cold water runoff and geothermal water. This should be noted when determining the primary factors controlling the thermal spring in this area. The temperatures calculated using a chalcedony geothermometer were close to the temperatures of the hot water recovered on the surface. In contrast, the temperatures calculated using a quartz geothermometer approached the temperatures of deep geothermal reservoirs. The results of this study preliminarily reveal the geochemical characteristics, recharge relationships, and water-rock interactions of thermal spring water in the Chuhe fault zone and propose effective geochemical geothermometers for the study area. These contribute to deeper insights into the mechanisms and controlling factors of the thermal springs along the fault zone, as well as providing practical value and a methodological model for enhancing thermal spring functionality and geothermal resource exploitation and utilization in the future.

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Application of airborne time-domain electromagnetic method in investigation of permafrost
YU Xue-Zhong, XIE Ru-Kuan, SHAN Xi-Peng, HE Yi-Yuan, SUN Si-Yuan, LI Shi-Jun
Geophysical and Geochemical Exploration    2024, 48 (2): 342-347.   DOI: 10.11720/wtyht.2024.1246
Abstract104)   HTML4)    PDF (2651KB)(238)      

Investigating the spatial distribution of permafrost is critical for cryosphere research. At present, China's investigation concerning the spatial distribution of permafrost generally employs the detection method of ground geophysical exploration combined with logs to obtain local point or line data. Alternatively, different remote sensing models can be used to simulate and estimate the thickness of regional permafrost. This study inferred the spatial distribution of permafrost based on airborne time-domain electromagnetic (TDAEM) data and resistivity calculation results. The comparative analysis of the inference results and the known drilling data reveals an average error of 18.5% between the permafrost thickness inferred from the inversion results of TDAEM data and the result determined by borehole temperature measurements. This suggests that the TDAEM method exhibits high effectiveness and accuracy in permafrost thickness investigation. With technical advantages like high efficiency and minor topographic influence, the TDAEM method can be applied to the large-scale, rapid, and quantitative permafrost investigation in the Qinghai-Tibet Plateau and the Greater Khingan Range in northeast China. Therefore, this study provides a new and effective technical solution for a comprehensive investigation of the spatial distribution of permafrost and its influence on ecological environment changes.

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Comparative study on lithology classification of oil logging data based on different machine learning models
JIANG Li, ZHANG Zhi-Mo, WANG Qi-Wei, FENG Zhi-Bing, ZHANG Bo-Cheng, REN Teng-Fei
Geophysical and Geochemical Exploration    2024, 48 (2): 489-497.   DOI: 10.11720/wtyht.2024.1492
Abstract102)   HTML0)    PDF (2671KB)(159)      

Specific computational tools assist geologists in identifying and classifying the lithology of rocks in oil well exploration,reducing costs,and enhancing operational efficiency. Machine learning methods integrate a vast amount of information,enabling efficient pattern recognition and accurate decision-making. This article categorizes the lithology of five oil wells in the Norwegian Sea,randomly dividing the data into a training set (70%) and a test set (30%). Using multivariate well log parameter data for training and validation,the application effectiveness of models such as Multilayer Perceptron (MLP),Decision Tree,Random Forest,and XGBoost is compared. The research results indicate that the XGBoost model outperforms others in terms of data generalization,achieving an accuracy of 95%. The Random Forest model follows with an accuracy of 94%. Meanwhile,Multilayer Perceptron (MLP) and Decision Tree models exhibit good robustness,with accuracies of 92% and 90%,respectively.

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Application of PNN logging in residual oil evaluation: A case study of the Gaotaizi oil layer in mature oilfields
SU Ke-Jia, QIN Zhen, FENG Min, AI Han-Bing, WANG Gang, GUAN Hua-Ling, FU Yu
Geophysical and Geochemical Exploration    2024, 48 (2): 393-402.   DOI: 10.11720/wtyht.2024.1075
Abstract101)   HTML1)    PDF (7513KB)(159)      

As mature oilfields are in their middle to late exploitation stage, the Gaotaizi oil layer exhibits significantly increased water saturation, elusive longitudinal stratification, and unknown distribution patterns of regional residual oil. These complicate the potential exploitation, energy conservation, and emission reduction. To ascertain the distribution of residual oil in the Gaotaizi oil layer in order to guide production operations and clarify potential targets, this study identified the longitudinal distribution of residual oil in the study area using the pulsed neutron-neutron (PNN) logging technique. The comparison between the monitoring results and production data of 10 wells revealed a coincidence rate of measures of 80%. The results of this study show that the PNN logging technique can be used to effectively identify the longitudinal distribution of residual oil in reservoirs and yields encouraging application performance in guiding the hole filling and water plugging for single wells in high-water-cut layers, thus increasing oil production. This technique has increased the evaluation accuracy of residual oil saturation in the Gaotaizi oil layer in the mature oilfield. It can provide technical support for formulating and adjusting subsequent oilfield exploitation schemes and offer a scientific basis for further guiding efficient reservoir exploitation, energy conservation, and emission reduction.

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Element geochemical characteristics of weathering crust profiles of the Wenchuan section in the upper arid valley of the Minjiang River
ZHOU Xue-Ni, CAO Ya-Ting, JI Yang
Geophysical and Geochemical Exploration    2024, 48 (3): 597-608.   DOI: 10.11720/wtyht.2024.1255
Abstract101)   HTML6)    PDF (6076KB)(134)      

This study conducted geochemical tests and analyses for vertical rock-soil profiles with different bedrock types in the Wenchuan section in the upper arid valley of the Minjiang River. Based on the above, this study explored the vertical distributions of elements in these weathering crust profiles to investigate the influence of bedrocks on the contents of chemical elements in soils. From a geological perspective, this study provided proposals for planting in agricultural production and eco-environmental restoration for the study area. The results of this study are as follows: (1) From top to bottom, weathering crust profiles can be divided into four layers: the humus layer (A), the illuvial layer (B), the soil parent material layer (C), and the bedrock layer (R). The humus layers exhibit higher average values of Al, Ca, K, Mg, Fe, Se, Zn, Cu, Cd, and Pb and lower average values of Si, Na, Mn, Cr, As, Cd, and Hg, compared to corresponding national average values in soils; (2) In weathering crust profiles with different bedrock types, except for elements with higher contents in both bedrocks and corresponding soil layers, the same elements manifest similar contents in other soil layers; (3) The chemical weathering intensity increased from the bedrock to the humus layers, with soil weathering degrees generally higher than bedrock weathering degrees; (4) In addition to characteristics inherited from soil parent materials, elements in weathering crust profiles show content differentiation, characterized by enriched Al, K, and Se in humus layers, enriched Na, Fe, Si, Pb, Cu, Zn, Mn, As, Cd, Cr, and Hg in illuvial layers, and enriched Mg and Ca in soil parent material layers.

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Intelligent inversion of magnetotelluric data based on improved DenseNet
YAO Yu, ZHANG Zhi-Hou
Geophysical and Geochemical Exploration    2024, 48 (3): 759-767.   DOI: 10.11720/wtyht.2024.1275
Abstract100)   HTML1)    PDF (4789KB)(163)      

Magnetotelluric (MT) sounding is a vital exploration method in tunnel engineering. Inversion methods can assist geologists in interpreting geological data by converting MT data into geoelectric parameters. However, conventional inversion methods exhibit inferior timeliness and reliance on initial model settings. In this study, deep learning was applied to the one-dimensional inversion of magnetotelluric data. First, an improved DenseNet model was constructed and trained to invert geological models of various resistivity-variable strata, yielding a fast computational speed and high accuracy. Then, the robustness of the improved DenseNet model was tested, suggesting that its network structure can achieve satisfactory inversion results for noisy data. Finally, this artificial intelligence technique was applied to the MT data inversion of the Hongjiaqian tunnel in the Huangshan area, obtaining geophysical exploration results that match the geological research results. Additionally, relevant construction recommendations were given based on the inversion results.

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An improved butterfly optimization algorithm in the inversion of Rayleigh wave dispersion curve
PENG Liu-Ya, FENG Wei-Dong, XIE Hui-Ting, LI Fei, YANG Yuan-Yuan, CAO Jun-Feng, REN Chuan
Geophysical and Geochemical Exploration    2024, 48 (3): 705-720.   DOI: 10.11720/wtyht.2024.1116
Abstract99)   HTML3)    PDF (6312KB)(163)      

Due to the multiplicity of solutions and the multiple extrema of the inversion objection functions,conventional nonlinear optimization algorithms are susceptible to unstable convergence and local optimum in the inversion of Rayleigh wave dispersion curves.This study improved the standard butterfly optimization algorithm by incorporating dynamic switch probability and nonlinear self-adaptive weight factors,yielding an elevated global exploration capacity in the early stage and a high local research ability in the latter stage.Furthermore,the dimension-by-dimension Cauchy mutation,along with a greedy algorithm,was employed to update the current best position during each iteration,ultimately directing the whole swarm population toward the global optimum.Tests of four commonly used benchmark functions demonstrate that the improved butterfly optimization algorithm(IBOA) outperformed other nonlinear algorithms,including the genetic algorithm and particle swarm optimization algorithm,in terms of the global research capacity of both unimodal and multimodal functions.Different algorithms were adopted for the inversion of the dispersion curves of three theoretical geological models.The results show that IBOA yielded inversion results that were closer to the models even when the dispersion curves contained 10% random noise.Finally,the IBOA was applied to actual Rayleigh wave data,and the inversion results were highly consistent with the strata revealed by drilling.Compared with the genetic algorithm and the particle swarm optimization algorithm,the IBOA significantly improved the convergence speed,as well as solution accuracy and stability.Therefore,the IBOA has a certain practical value and application prospects.

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Comparative analysis of stereo and planar sources for slope breaks
CHEN Feng-Ying, WANG Xiang-Chun, SUN Jian, LI Can-Ping, REN Xiao-Qing
Geophysical and Geochemical Exploration    2024, 48 (2): 461-469.   DOI: 10.11720/wtyht.2024.1160
Abstract99)   HTML0)    PDF (6069KB)(148)      

Deep-water areas have gradually become the exploration targets of offshore oil and gas resources.Due to the intricate geological conditions of these areas,seismic imaging of moderately deep reservoirs suffers low signal-to-noise ratios and resolution,inevitably affecting the exploration and exploitation of oil and gas resources.To improve the quality of seismic data of moderately deep reservoirs in deep-water areas,this study first acquired seismic data at the same location in a slope break using stereo and planar sources under the same acquisition parameters.Then,after being processed using the same workflow,the seismic data were subjected to comparative analysis from the perspective of wavelets,shot gather spectra,near-trace spectra,superimposed profile spectra,and final imaging.The results indicate that the wavelets of a stereo source outperformed those of a planar source in terms of energy intensity and ghost reflection interference.Moreover,for moderately deep reservoirs of the deep-water area,a stereo source exhibited broader frequency bands and especially rich frequencies within 30~80 Hz.These features enhanced the resolution of seismic profiles and the imaging quality of seismic data.Thus,compared to planar sources,stereo sources enjoy more advantages in improving seismic imaging of moderately deep reservoirs in deep-water areas.Therefore,stereo sources can be employed to acquire seismic data of moderately deep reservoirs with complex geological conditions in deep-water areas,and the purpose is to improve the imaging quality of seismic data.

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Organic carbon content-baesd prediction and influencing factors of black soil layer thicknesses
LIU Kai, DAI Hui-Min, LIU Guo-Dong, LIANG Shuai, WEI Ming-Hui, YANG Ze, SONG Yun-Hong
Geophysical and Geochemical Exploration    2024, 48 (5): 1368-1376.   DOI: 10.11720/wtyht.2024.1436
Abstract98)   HTML3)    PDF (4274KB)(115)      

Black soil layer thicknesses, anessential attribute of black soil,serves as a significant indicator for measuring the fertility and erosion degree of black soil. Their spatial prediction holds critical significance for supporting China's black land conservation and ensuring food security.Considering the diagnostic characteristics of black soil layers in soil system classification, this study regarded soil layers with organic carbon content higher than 6×10-3 of soil parent materials as black soil layers.Moreover, it derived the calculation formula for the thicknesses of black soil layers relying on the exponential distribution pattern of organic carbon in the vertical soil profile. Based on the 62 896 topsoil and 15 687 deepsoil organic carbon data obtained from the multi-purpose regional geochemical survey, this study conducted detailed spatial prediction of the thicknesses of black soil layers in the Songliao Plain and analyzed their relationship with soil types and climate factors. Key findings are as follows:(1) The thicknesses of black soil layers in the Songliao Plain range from 0 to 165 cm, with a median of 23.33 cm;(2) The spatial distribution of black soil layers exhibits significant heterogeneity, characterized by thin southwestern and thick northeastern portions;(3) The black soil layers of swampy soil and peat soil manifest the largest average thicknesses between 60 and 80 cm, followed by those of typical black soil (average thickness: 56 cm) and those of albic soil and meadow soil (average thickness: 40~50 cm);(4) The spatial distributions of the thicknesses of black soil layers are closely associated with climatic conditions, primarily showing a significant negative correlation with temperature and a positive correlation with rainfall;(5) The mean annual temperature of 0 ℃ is a significant temperature threshold for the development of thick black soil layers.Above this temperature, the average thickness of black soil layers exceeds 80 cm and no longer changes with temperature. With global warming, the southward shift of this 0 ℃ is otherm may significantly influence the thicknesses of black soil layers.

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Geochemical characteristics of soils and prospecting potential of the northern Laojunmiao gold deposit in the Beishan area, Gansu Province
ZHANG Wen-Bin, ZHOU Xian-Jun, HOU Cui-Xia, WANG Ning-Zu, SUN Ping-Yuan, ZHAO Zhen-Guan, HE Bi
Geophysical and Geochemical Exploration    2024, 48 (4): 945-953.   DOI: 10.11720/wtyht.2024.1342
Abstract97)   HTML3)    PDF (5615KB)(145)      

Thenorthern Laojunmiao gold deposit is located in the southern zone of the Beishan area, Gansu Province, and on the northeastern margin of the Tarim block. It resides in a tectonic environment of the Yaodongliang-Xiaoxigong Paleoproterozoic rift basin. This study delineated five comprehensive anomaly zones in the area through a 1∶10,000 geochemical soil survey. As verified by trenching exploration, three gold ore bodies, one gold-silver ore body, and two low-grade gold ore bodies were identified in the comprehensive anomaly zones, suggesting satisfactory prospecting results. Based on the comprehensive geological and geochemical anomaly characteristics of the deposit, this study established an integrated geological-geochemical prospecting model centering on the HT1 comprehensive anomaly zone. Moreover, it proposed the subsequent prospecting direction, providing a significant reference for the deep and peripheral prospecting in the area.

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Exploring the shear-wave prediction method for complex lithologic assemblages of the Fengcheng Formation in the Mahu sag
ZHONG Hou-Cai, LIU Zhen-Yu, ZHU Zhe, QU Lin, ZHANG Shan, YAO Yan-Fei, FAN Rong-Rong
Geophysical and Geochemical Exploration    2024, 48 (3): 736-746.   DOI: 10.11720/wtyht.2024.1179
Abstract97)   HTML1)    PDF (9611KB)(135)      

Research on shear-wave prediction for complex lithologic assemblages of the Permian Fengcheng Formation in the Mahu sag is critical but challenging for accurately identifying hydrocarbon accumulation zones in the sag.The key to the prediction is to make breakthroughs in petrophysical modeling based on different lithologies.Given various lithologic types and intricate mineral compositions,this study delved into petrophysical modeling based on different lithologies.Consequently,this study developed an interval-,lithology-,and model-specific shear-wave prediction technique for complex lithologies.Furthermore,it established a technique for building a dry rock matrix for alkali lake-type dolomitized tight reservoirs by highlighting the major rock mineral compositions and merging the same types of rock mineral compositions.Additionally,the self-consistent model was selected for shear-wave calculation in the petrophysical modeling of dolomitized sandstone reservoirs.These techniques have been applied in the Fengcheng Formation of the Mahu Sag,achieving encouraging application results in both the shear-wave prediction of complex lithologic assemblages and the prediction of sweet spots.This study will provide a basis for well deployment and reserves determination in the area and offer valuable experience for oil and gas exploration in similar areas.

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Prediction of oil column heights in fault-controlled tabular reservoirs through time-frequency analysis based on improved generalized S-transform
YUAN Xiao-Man, LI Xiang-Wen, ZHANG Jie, DAN Guang-Jian, LU Zhong-Yuan, HAN Chong-Yang, ZHANG Lei, XU Jian-Yang
Geophysical and Geochemical Exploration    2024, 48 (3): 768-776.   DOI: 10.11720/wtyht.2024.1321
Abstract96)   HTML4)    PDF (6903KB)(121)      

The fault-controlled carbonate area in the northern depression of the Tarim Basin possesses abundant oil and gas resources.Identifying the oil-water contact (OWC) of fault-controlled tabular reservoirs is critical for their effective exploitation.However,OWC identification through drilling is costly and challenging.In contrast,it is efficient to identify the OWC using geophysical methods.This study proposed a time-frequency analysis method based on generalized S-transform.As revealed by the joint analysis of extensive time-frequency analysis results of through-well seismic channels and production performance analysis data,the depth/time-varying main frequency of seismic data is positively correlated with the oil layer thickness.Hence,this study proposed to identify the OWC using the abnormal inflection point of the energy envelope of seismic channel time-frequency gather.Experimental results demonstrate that oil layer thickness results obtained are uncertain,generally reliable,and reliable in the case of oil column height (OCH)<120 m,120 m≤OCH≤250 m,and OCH≥250 m,respectively.The method proposed in this study was applied to a fault fracture zone of an area of the Fuman oilfield,obtaining the main predicted oil layer thicknesses between 200 m and 520 m,aligning with the actual exploitation results.Therefore,the method of this study can be employed to guide exploitation.

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Application of comprehensive geophysical prospecting to groundwater exploration in Ritu County of the Ali area
CHEN Yong-Ling, JIANG Shou-Jin, XIE Dan, WANG Jia, HE Zhi-Xiong, LIU Cheng
Geophysical and Geochemical Exploration    2024, 48 (3): 668-674.   DOI: 10.11720/wtyht.2024.2485
Abstract96)   HTML2)    PDF (3140KB)(162)      

Surface water resources are scarce in Ritu County of the Ali area due to the absence of large rivers. The strata in the area are primarily composed of Jurassic and Cretaceous sedimentary rocks, exhibiting significantly varying spatial water abundance, thus posing challenges in water exploration through drilling. Based on hydrogeological survey data, this study summarized the occurrence patterns of pore water in Quaternary unconsolidated rocks and fissure water in fault structures and the electrical characteristics of aquifers in the area. It explored the structural fissure water with high water abundance in the area using the high-density resistivity method and the audio magnetotelluric method. Based on the geophysical exploration results, it delineated favorable aquifers. Furthermore, it verified the exploration accuracy through drilling, obtaining high-yield water wells, and ensuring the supply of drinking water. Therefore, the combination of multiple geophysical exploration methods is effective in groundwater resource surveys, improving the exploration accuracy of groundwater resources and providing effective technical support for well deployment.

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Research on magnetotelluric time series classification based on artificial neural network
YANG Kai, LIU Cheng, HE Jing-Long, Li Han, YAO Chuan
Geophysical and Geochemical Exploration    2024, 48 (2): 498-507.   DOI: 10.11720/wtyht.2024.1144
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With the development of society,high-quality magnetotelluric signal acquisition is becoming more and more difficult because of various types of human interference are increasingly intensified. Scholars have proposed many corresponding denoising methods for different types of noise to improve data quality. It is impossible to manually interpret each data before denoising due to the huge amount of data. So an efficient noise recognition and classification method is urgently needed. Based on this, artificial neural network is applied in the classification of magnetotelluric time series in this paper. Four types of time series,namely,simulated square wave, power frequency, impulse noise, and measured noiseless data, were used to conduct noise classification training and measured data classification on LSTM、FCN、ResNet、LSTM-FCN and LSTM-ResNet models. The results show that FCN and LSTM-FCN has a relatively good effect on the classification of magnetotelluric time series. Among them, the highest classification accuracy of FCN measured data can reach 99.84%, and the average time for each epoch is 9.6 s. LSTM-FCN has higher classification accuracy than FCN,the highest classification accuracy of measured data sets is nearly 100%, but the average time for each epoch is 24.6 s, and it is easier to overfit than FCN. Overall, LSTM-FCN can achieve higher classification accuracy when the amount of data is relatively small, if the amount of data is large, it is necessary to consider the time cost,using FCN is more appropriate. Finally,the magnetotelluric data containing different types of noise was successfully processed using the magnetotelluric noise processing system which constructed by the LSTM-FCN classification model and the LSTM denoising model.

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Log-based identification of the types of the Maokou Formation carbonate reservoirs in the central Sichuan Basin
LIU Yu, WANG Liang, LUO Yang, SU Shu-Te, YAO Lin-Fang, LIU Yu-Chao, ZHOU Chun-Run, HU Meng-Die
Geophysical and Geochemical Exploration    2024, 48 (3): 629-639.   DOI: 10.11720/wtyht.2024.1289
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The Maokou Formationcarbonate reservoirs in the central Sichuan Basinexhibit well-developed dissolutionpores, vugs, and fractures, pronounced heterogeneity, and diverse types. This study aims to identify their types and establish the log-based identification criteria for various reservoir types. First, this study classified the reservoir types based on the analysis of casting thin sections, core photos, and micro-resistivity imaging logs.Moreover, it determined the conventional log response characteristics of different reservoir types. Finally, it conducted log-based identification of reservoir types using the fracture porosity (φf) -secondary porosity index (RP) cross-plotting method. The results are as follows: (1)The Maokou Formation carbonate reservoirs in the central Sichuan Basin can beclassified into four types, i.e., fractured-vuggy, fractured-porous, porous-vuggy, and matrix porous reservoirs;(2) Fracture porosities calculated from different models are more similar in the case of more developed fractures, and dissolution pores and vugscan affect the fracture porositycalculation results to some extent;(3) The φf-RP cross-plotting method can effectively identify reservoir types. These research results provide technical support for the log-based identification of carbonate reservoir types.

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A data augmentation method for semi-airborne transient electromagnetic noise based on a generative adversarial network
FENG Wei, FENG Hao, XIAO Li-Jiang, CHEN Pin-Ming, LIU Dong, WANG Yong-Xin, ZHOU Xiao-Sheng, SUN Huai-Feng, WANG Zhen
Geophysical and Geochemical Exploration    2024, 48 (3): 812-819.   DOI: 10.11720/wtyht.2024.1211
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The semi-airborne transient electromagnetic (SATEM) noise data, exhibiting intricate forms, high acquisition costs, and small volumes, cannot be augmented using conventional augmentation methods, thus significantly hindering the subsequent denoising work. Hence, this study proposed a data augmentation method for SATEM signals based on the generative adversarial network (GAN). By designing the generator as a long short-term memory (LSTM) network and training the generator and discriminator models based on the dataset of real-measured SATEM noise, this study obtained a generator model that can generate simulated noise data. Then, this study analyzed the distributions of the simulated noise generated by the generator and the real-measured noise. Moreover, this study compared the performance of the denoising network before and after augmentation, demonstrating the effectiveness of this method for augmenting real-measured SATEM noise data.

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Predicting the spatial distribution of soil organic matter using the model consisting of the Boruta algorithm and the optimized GA combined with the geostatistical method
GAO Peng-Li, REN Da-Lu, LI Chao-Hui, FENG Zhi-Qiang, MIAO Hong-Yun, QIAO Lin, WANG Jian-Wu, YANG Yong-Liang, ZHANG Li-Ming, LI Guang-Hui
Geophysical and Geochemical Exploration    2024, 48 (3): 747-758.   DOI: 10.11720/wtyht.2024.1114
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Establishing a spatial prediction model for soil organic matter (SOM) can accurately predict the spatial distribution of SOM content, playing a significant role in scientific soil management and ecosystem service enhancement. Focusing on the soils in Yonghe County, Linfen City, Shanxi Province, this study extracted topographic factors and vegetation indices from the digital elevation model (DEM) and vegetation remote sensing data. With soil attributes as variable factors, this study, using the Boruta algorithm, selected the characteristic variablescorrelating strongly with SOM from variable factors as auxiliary variables. These auxiliary variables were used as model inputand the measured SOM values as model output.The SOM content in samples in the training set was predicted usingthe ordinary Kriging (OK)method, the back propagation neural network (BPNN), the genetic algorithm-optimized BPNN (GA-BPNN), and the improved BPNN combined with the geostatistical method (the GA-BPNN-OK method) separately. The prediction accuracy was comparatively analyzed based on samples in the validation set. The results show that: (1)The Boruta algorithm ranked the selected characteristic variables in order of importance, obtaining the sequence of total nitrogen >topographic wetness index (TWI) > elevation > slope > normalized difference vegetation index (NDVI) > enhanced vegetation index (EVI); (2)Despite local differences,the SOM prediction results obtained using the four methods exhibited roughly the same overall spatial distribution: low in the western and southwestern portions of the study areabut high in the eastern and southeastern portions;(3)Compared to the other three models, the GA-BPNN-OK model demonstrated more distinct low- and high-value areas in the predicted SOM distribution. (4) As revealed by the comparison of prediction accuracy indices, the GA-BPNN-OK method yielded a minimum root mean square error (RMSE) of 0.059, a minimum mean absolute error (MAE) of 0.240,a minimum mean relative error (MRE) of 0.165, and a maximum fitting coefficient (R2) of 0.78. To verify the effects of the Boruta algorithm in improving model accuracy, global variables, as well as the variables determined through characteristic selection, were used as the model inputof the GA-BPNN method. The comparison of the prediction results indicates that the Boruta algorithm reduced the model error. Therefore, the Boruta algorithm and the GA-BPNN-OK method constitute the optimal prediction model for the spatial distribution of SOM content.

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Log-based in situ stress prediction of deep coalbed methane reservoirs in the Daji block
XIE Zheng-Long, LIU Zhi-Di, HAN Hong-Lai, WANG Duo, WANG Cheng-Wang, WANG Wei, JI Liang
Geophysical and Geochemical Exploration    2024, 48 (2): 356-365.   DOI: 10.11720/wtyht.2024.2600
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For deep coalbed methane (CBM) exploration and production, accurate in situ stress prediction holds critical significance for safe and efficient drilling and completion of wells. Deep CBM reservoirs, once considered restricted areas for exploration and exploitation, have been highly anticipated owing to their high yields in recent years. However, their in situ stress prediction model has not been investigated effectively. Hence, this study systematically analyzed six in situ stress prediction models commonly used for conventional oil and gas reservoirs and unconventional gas (like CBM) reservoirs. Based on these prediction models, this study calculated the in situ stress, and found that the combined spring model and the Newberry model yielded relatively high accuracy through comparative analysis of closure pressures. To improve the accuracy of in-situ stress prediction models, the effective stress coefficient of coal rocks was employed to optimize the two models. The optimized in-situ stress models yielded prediction accuracy errors reduced by 4%, roughly meeting the requirements of in-situ stress prediction accuracy for deep CBM exploration and production in the Daji block.

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