The Laiwu area in central Shandong Province, situated in the eastern North China Craton, is a significant production area of skarn iron-rich ores. Its ore deposits occur primarily in the contact zone between the mining rock mass and the Middle Ordovician carbonate formation. Based on the latest areal gravity and magnetic survey results, this study thoroughly investigated the characteristics of gravity and magnetic anomalies along the Shijiaquan-Liujiamiao area in the western periphery of the mine rock mass. Then, this study delineated the deep prospecting target combining the characteristics of gravity and magnetic fields of the known iron deposits in the Laiwu area. Large-scale gravity and magnetic profiles were arranged in the favorable mineralization area. With the known boreholes as constraints, the gravity and magnetic anomalies were qualitatively and quantitatively interpreted using the 2.5D gravity-magnetic joint inversion technique. The interpretation results provide a basis for the location and depth of the borehole to be placed, which revealed a 15.8 m-thick iron-rich ore deposit, suggesting remarkable prospecting effects. This study holds critical indicative significance for further exploration of skarn iron ore deposits in this area.

The shear wave velocity of subsurface can be estimated by analyzing the passive surface waves typically generated by cultural and natural sources. This article first introduces the passive surface waves and the processing procedure, and then utilizes the simulated passive waves to compare the FK and SPAC methods in deriving dispersion curves. It also discusses the general requirements of data acquisition and demonstrates some field examples.

The eastern Kunlun metallogenic belt, as a significant metal metallogenic belt in China, hosts extensive orogenic gold deposits and large-scale Kunlunhe, Gouli, and Wulonggou gold concentration areas. The Dachaigou gold deposit is a large-scale gold deposit newly discovered in the Wulonggou gold field in recent years. Despite its high metallogenic potential, the western extension of its ore belt has not been defined. Hence, this study conducted induced polarization (IP) sounding and wide-field electromagnetic sounding in the deposit. The results show that the known ore belt is situated in the regional gravity anomaly gradient zone, the transition zone of positive and negative weak magnetic anomalies, the edge of IP anomalies, or the electrical gradient zone. The development zone of the regional tectonic belt resides in the large-scale IP anomaly section. The regional tectonic belt is characterized by a wide range of low-resistivity anomaly zones. The IV and III alteration zones of the known ore belt are located in the opening position of the low-resistivity anomaly zone and the shallow electrical anomaly gradient zone, respectively. Based on the above understanding and the electromagnetic anomaly change patterns of several parallel profiles in the western extension segment, it was inferred that the regional ore-controlling structure extends steadily in the W-NWW direction, forming a favorable prospecting space in the western extension segment of the deposit. The results of deep geophysical exploration in the Dachaigou deposit indicate that geophysical methods manifest significant advantages in deep geological prospecting research, providing successful experience for deep prospecting in the eastern Kunlun gold deposit area.

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.

Geothermal resources are significant clean energy and tourism mineral resources. The Rucheng Basin, a carbonate basin in the southeastern mountainous area of Hunan Province, possesses favorable conditions for the formation of convective geothermal energy. However, the basin is enclosed on three sides by the giant Zhuguangshan rock mass, and its basement is subjected to the intrusion and destruction by the rock mass, resulting in severely deformed formations, crisscrossing faults, and significantly different eastern and western structures. The understanding of the basin's water- and heat-conducting pathways and deep reservoir structures remains elusive, thus restricting the investigation of the basin's geothermal potential. Hence, this study probed the basin's deep structures through gravity survey and audio magnetotellurics (AMT), obtaining the following insights: (1) The Rucheng Basin has developed into a bidirectional ramp structure due to east-west differentiation. The synclinorium in the east experienced compression and clockwise rotation due to the emplacement of the Yanshanian rock mass, rocks were fragmented in the core zone, and strike-slip fracture zones were found at the boundary. The faults have vertical cutting depths exceeding 4 km, widths ranging from 300~600 m, and dip angles between 80°~90°. (2) The basin's basement anticlinal axis hosts several NWW-directed concealed rock masses, with diameters from 3~4 km and buried depths from 0.5~1.5 km. Hot springs reside in the fracture zones crossing the boundaries of the concealed rock masses. (3) The basin boasts favorable conditions for the formation of convective geothermal energy. Folds, fault zones, and concealed rock masses match each other to form a unified spatial combination of heat-controlling elements, manifesting heat accumulation characterized by east-west recharge and intermediate discharge. With more thriving deep geothermal reservoirs in the east, the basin has high potential for geothermal resources.

A comparison for the marine gravimeters on the same vessel was carried out between SAG-2M marine gravimeter developed by China and KSS31M marine gravimeter designed by Germany in order to test the technical performance and data reliability of SAG-2M marine gravimeter. The raw gravity data acquired from these two marine gravimeters were preprocessed according to the standards of marine geologic survey to obtain the free air gravity anomalies, and the comparison and relativity for those two types of gravity data were studied by analyzing the cross-point differences, survey lines and grid data. The result shows that the SAG-2M marine gravimeters have the same level of measurement accuracy with the KSS31M marine gravimeter because there is a highly linear relationship between the data from two marine gravimeters with an approximately similar variation trend. Based on the results of comparison, it is concluded that the self-developed SAG-2M marine gravimeter shares the similar standard of measurement accuracy with the KSS31M marine gravimeter with a stabilized technical performance, which provides an important reference for the future application of SAG-2M marine gravimeter.

The static effect is a commonly-existent technical problem in MT method, and its influence could lead to an unacceptable result of the observation data. According to the distinguishing method, correction method and the data collection system, the authors put forward a spatial-domain topological processing method based on the original data. Through the analysis of the cause and representation of the static effect and the superposition characteristics of electric field components, the authors began with the essence of space sampling and completed the formula for obtaining the topological curve, finally got the observation result with different pole distances at the same site and found out the implicit observation information in the observation system of continuous arrays. According to the analytical result of theoretical model, the authors established the model of all the possible static migrations of the record site with the change of pole distance in different parts of local inhomogeneous body and, in addition, established the basic topological result graphic display and interpretation method including using sites to do pseudo-section processing and using the fixed frequency result of all sites in a profile painting pseudo-planar graph. The authors also compiled the software of topological processing and finished this new method of using topological processing method to analyze the static effect of MT both in theory and in application. The test result proves that the topological processing could improve the quality of data. With this technique, the discrimination of static effect could begin with many aspects, could find out the spatial distribution of the distorted electrical field caused by local inhomogeneous body, and could find out the location and spatial distribution of the local inhomogeneous body, thus providing researchers with real information on the surface electric structure. The topological processing could also get the result of changing arrays, and this means the emerging of a new method for inhibiting interference.

The geological conditions in the karst-developed area are complicated.The geological conditions directly affect the bridge design plan.On the basis of comprehensive research on the topographic and geomorphological characteristics and geological conditions of the bridge area of the Xiangjiang River Bridge in Zhuzhou and with the purpose of ascertaining the type and scale of karst development in the bridge site area and the location of each bridge pier,the authors used such means as high-density electrical method,magnetotelluric survey,shallow water earthquake and CT between holes in the survey.Verification results in the anomalous area show that the detection results are accurate and reliable,indicating that the integrated geophysical method is accurate and effective for bridge site survey.The bridge span layout scheme and pile foundation laying height were adjusted to make the layout span and pile length more reasonable,thus successfully avoiding karst,realizing the geological priority and forming the bridge design scheme for site selection.

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.

The regularization term for semi-airborne transient electromagnetic regularization of long-line source usually adopts L2 norm, and the fitting result is relatively smooth, which cannot effectively describe the layer interface information. Aiming at the stratified medium steep change model to realize the inversion algorithm whose regular term is the L1 norm, the authors transform the original problem into the L2 regularization sub-problem by the iterative re-weighted least squares method to solve the problem of non-differentiation in the L1 norm; OpenMP technology is used to solve the problem. The parallel calculation of the Jacobian matrix improves the inversion speed; the adjustment strategy of the adaptive regularization factor segmentation iteration method is analyzed and improved. The improved adaptive regularization factor adjustment strategy is more suitable for semi-airborne transient electromagnetic inversion algorithm of L1-norm regularization. Finally, the resistivity is inverted and compared with the Occam inversion results. The results show that the inversion of L1-norm regularization can highlight the electrical interface conforming to the real model after sufficient iterations, and the inversion resistivity is closer to the true value of the model.

Ji'nan possesses highly abundant geothermal resources, which are hosted by Ordovician-Cambrian karst-fissured geothermal reservoirs and Neogene-Paleogene clastic pore-fissure geothermal reservoirs. The geothermal exploration in this study focuses on the Ordovician-Cambrian karst fissured geothermal reservoirs in Daqiao Town in northern Ji'nan. Through geophysical profile measurements, this study aims to identify the distributions of strata and fault structures and the burial depths of geothermal reservoirs, infer the attitudes and spatial morphologies of fault structures associated with heat control and conduction, delineate the target area for geothermal well construction, and conduct drilling verification in the favorable underground water-rich position. Building on the collected data, this study interpreted and inferred the fault structures in the study area and comparatively analyzed the water-bearing properties by employing direct-current sounding, controlled source audio magnetotellurics, and magnetotelluric survey. A geothermal exploration and production combined well was constructed in a favorable position of the geothermal target area, manifesting a completion depth of 1 532.06 m, a static-water burial depth of 13.03 m, a wellhead water temperature of 50.1 ℃, a water yield of 132.998 m³/h, and a dropdown depth of 18.27 m.

The northeastern margin of the Linyi uplift is located at the eastern end of the Luxi Block and immediately adjacent to the Yishu fault in the east. The main structural framework of the study area is controlled by the NE-trending Tangwu-Gegou fault and the NW-trending Mengshan fault. Covered by the Cenozoic sediments, the boundaries of main tectonic units in the study area are almost all concealed, and it is necessary to further investigate the change in the strike of the eastern end of the Mengshan fault as well as the distribution of the angular unconformity along the northern boundary of the Linyi uplift. Using the latest 1:50,000 high-precision gravity data, this study mainly investigated the positions and intersection relationships of the boundaries of tectonic units based on the qualitative analysis of gravity field, the interpretation of multiple gravity potential field conversion, and the division scheme of geotectonic units in Shandong Province. The analysis results are as follows. The Mengshan fault at the junction of the Mengshan uplift and the Pingyi sag transitions from the NW trending to nearly-EW trending in the east of Bancheng Town, significantly cuts the NE-trending Tangwu-Gegou fault, and shows a NW-trending turn to the east again. The angular unconformity at the junction of the Linyi uplift and the Pingyi sag neither ends in the Mengshan fault in the north nor turns southward but extends to the Tangwu-Gegou fault in the east. This unconformity also controls the southern boundary of the Pingyi sag, making the NW-trending banded gravity anomalies of the sag turn eastward. Consequently, the boot-shaped low-value gravity anomalies were formed in the study area. Based on the high-precision gravity boundary identification, this study determined the fault system and tectonic division of the northeastern margin of the Linyi uplift, providing high-precision gravity data for the basic geological study in the study area and laying a good foundation for further mineral geological survey.

The understanding of the Paleogene Dongying formation and the Jixianian Wumishan formation have been gradually deepened with the exploration and development of deep thermal reservoirs in the Binhai New Area.This paper analyzes the hydrochemical characteristics, reservoir temperature, and hydrogeochemical effects of the geothermal fluid of the Dongying and Wumishan formations, thus providing bases for the further development and utilization of deep geothermal resources. The Wumishan formation in the Ninghe salient is adequately recharged. In contrast,the Dongying formation occursin a relatively closed environment, and the geothermal fluid in it is at a state of chemical equilibrium. The average temperature of the geothermal reservoirs in the Wumishan and Dongying formation scalculated using geothermometers is about 126 ℃ and 100 ℃, respectively. The geothermal fluid in both formations originates from atmospheric precipitation. Compared to the Wumishan formation, the geothermal fluidin the Dongying formation exchanges heat with rocks for a longer time and has a weaker cycling capacity. The runoff direction of the geothermal fluid in the formations is from northeast to southwest, with leaching, cation exchange, precipitation,and mixing mainly occurring during the fluid runoff.

An application test of the broadband magnetotelluric method (BMT) was carried out in the Mandulatu area based on the construction needs of a large-scale sandstone-type uranium deposit base in the Erlian Basin. The purpose is to study the detection ability and effect of this method at a depth of 2,000 m and above, provide effective technical support for the evaluation of uranium resources in the area, and improve the effects and benefits of uranium prospecting. In this study, the data acquisition time and the lowest frequency were tested by the test area method. Given the work efficiency and benefit, it is determined that the lowest detection frequency is 0.10 Hz and the observation time is 60 min so that the prospecting depth of Erlian Basin can reach the requirement of 1,500~2,000 m. The comparative analysis of the test results with borehole and shallow seismic data shows that BMT is feasible in solving geological problems such as caprock structure, basement structure, sand body development characteristics of the target layer, and fault structure in the basin.

The development of Se-rich land has been carried out in many regions of China, achieving remarkable results. However, no Se-rich land or crop has been reported in Tibet. This study analyzed the characteristics and influencing factors of the Se content in the soils and crops of the key arable land areas in Bailang County, Tibet, aiming to lend support to the development and utilization of Se-rich land in the Qinghai-Tibet Plateau. The results are as follows: The soils in the study area have a Se content of (0.05~0.76)×10^-6, which is higher than the background value of soils in Tibet (0.15 ×10^-6); 76.83% of the land in the study area has sufficient Se, and land in the study area with a Se content of greater than 0.3 ×10^-6 covers an area of 45.43 km², as determined according to the standard threshold of Se content in alkaline soils (w(Se)≥0.3 ×10^-6). Further investigation shows that highland barley seeds have a Se content of (0.017~0.17)×10^-6 (average: 0.063 ×10^-6) and rapeseeds have a Se content of (0.043~0.14)×10^-6 (average: 0.078 ×10^-6) in the distribution area of Se-rich soils. As indicated by the root soil results of the zones with Se-rich soils, the Nieru Group controls the source of Se in soils, and Se and effective Se content in the soils are significantly positively correlated with N, P, alkali-hydrolyzable nitrogen, and rapid available phosphorus but is significantly negatively correlated with pH. These results indicate that the behavior of Se is significantly affected by a large number of nutrient elements in the soils and pH. Overall, the distribution areas of Se-rich soils in Bailang County have high soil environmental quality, crops with a high Se content, and great potential for the development of Se-rich plateau characteristic agricultural products.

Previous studies have shown that CNN-GRU hybrid deep learning inversion EI has the advantages of strong applicability and strong generalization capability.However,there are many pre-stack inversion parameters based on deep learning,such as internal deep learning network learnable parameters and external hyperparameters.At present,there is still no systematic research on the impact of hyperparameter selection on network performance and computing speed,which will directly affect the further promotion and application of the method.Therefore,based on the hybrid deep learning inversion elastic impedance,this paper discusses the impact of five hyperparameters,i.e.,learning rate,Epoch,batch_size,regularization parameter,and the number of wells participating in network training on network performance and calculation speed,thus providing a basis for studying the selection of seismic inversion hyperparameters.The research results can provide a feasible quality control method for three-dimensional large-area deep learning inversion,which is of certain significance for promoting the wide application of deep learning methods in petroleum geophysical prospecting.

In this study, the moving average method was used to reprocess the 1∶200,000 stream sediments data from seven sheets in Wutaishan-Hengshan area. In combination with the 1∶200,000 gravity data and 1∶50,000 aeromagnetic data obtained in this area, the authors found that the comprehensive anomalies are in good agreement with the deposits related to the Yanshanian rock mass. Choosing elements such as Au, Ag, Cu, Pb, Zn anomalies and high-magnetic and low-gravity anomalies as the prediction criteria, the authors predicted a total of 13 polymetallic ore prospective areas related to the mineralization of rock masses in the study area. According to available data, there are 9 NW-trending fault structural zones in this area. The intrusive position of the rock mass is controlled by the intersection of the NW-trending fault and the NE-trending fault. Most of the known rock masses and the 11 prospective areas predicted by this paper are distributed in the fault structural belt, forming multiple tectonic magmatic zones. The polymetallic ore deposit is inextricably linked with Yanshanian rock mass.

Spectral induced polarization (SIP) response testers for rock and ore specimens determine the SIP response differences between ore bodies and host rocks by measuring the SIP characteristics of rock and ore specimens, thus providing a basis for ore prospecting. They are widely used in geophysical exploration. However, the existing SIP response testers have shortcomings in terms of bandwidth, intelligence, portability, and power consumption. Given this, this study developed a piece of measurement and control software for SIP response testers based on the Internet of Things (IoT) techniques including NB-IoT, Bluetooth, and Wifi, realizing the functions such as near-field communication, cloud communication, data visualization, and data processing. The test results verify that the software can achieve the desired effect owing to its easy operation, stable running, and friendly man-machine interaction.

Transient electromagnetic method (TEM) is the main tool for detecting mined-out area. However, when the goaf is buried deep or there are many buildings in the survey area, it is often difficult for the traditional loop source device to meet the detection needs. SOTEM has such advantages as high signal amplitude, strong signal-to-noise ratio, large detection depth, and convenient and efficient construction. The buried depth of the goaf in the Fangzi coal mine in Weifang City is about 500 meters, and most of the area is in villages where houses are densely distributed. In order to effectively detect the distribution and influence range of the goaf under Jiangjia Village, the authors adopted SOTEM method to carry out the detection work. The problem of building obstacle was overcome by placing transmitting source outside the village and using portable receiving device to receive signal in the village. Wavelet denoising and five-point smoothing technology were used to filter the strong interference data, and then OCCAM method was used to carry out one-dimensional inversion of the data. The results show that the depth of SOTEM detection reached 800 meters, and the distribution range of low-resistance goaf was successfully delineated, which was later verified by drilling.

Following China's planning for ore prospecting in overburden areas, China's geochemical exploration researchers have conducted extensive research on the fundamental theories, methods, and technologies of geochemical exploration for overburden areas in the past decade. They achieved significant advances mainly in two aspects: (1) the research on the migration mechanism, occurrence state, and anomaly formation mechanism of elements in overburden areas; (2) advances in methods and technologies, including geoelectrochemistry, active state of elements, geogas, separation of micro-fine-sized soil particles, soil thermomagnetic composition, and integrated gas survey, as well as numerous experimental demonstrations. These advances represent continuous progress in the research on the fundamental theories, methods, and technologies of geochemical exploration for overburden areas, providing new geochemical methods and technologies for ore prospecting breakthroughs in overburden areas.

Aimed at tackling the problems of low efficiency and the need of high data quality of IP observation methods in borehole, the authors developed a new device of borehole IP prospecting in this paper. The device can be used to measure the polarization field potential (V), potential difference (ΔV), secondary field potential (V₂), potential difference (ΔV₂) and time information (T) simultaneously by full waveform electrical method, and then obtain various IP parameters. In order to test the validity of the method, the authors studied the application of full waveform array IP to a copper-gold deposit in Anhui Province, obtained the connectivity of the drilled orebody, and determined the direction and distribution range of the orebody. The application results show that this bolehole IP observation of full waveform array method has high efficiency and strong anti-interference capability.

The MTU series magnetotelluric sounders produced by Phoenix Geophysics Ltd. in Canada have been widely used in various fields of earth exploration because of their advantages, such as small weight and stable and reliable data acquisition. However, their special data formats make the data processing troublesome. At present, most of the data processing depends on the SSMT-2000 software developed by Phoenix Geophysics, which is not conducive to the improvement and application of data processing methods. By studying the formats of data files of MTU series magnetotelluric sounders, this study used the UltraEdit software to analyze the structure and rules of the data files and analyzed and studied TBL, CLB, CLC, and TS files based on the C# programming language. As a result, this study transcoded the data files from indigestible binary files into plain files that are easy to understand and provided the modification and editing module of TBL parameter files, the data analysis module of CLC and CLB files, and the transformation module of TS files. The data measured in the field were edited using the program developed in this study. The test results verify that the program can modify TBL file parameters, analyze CLB and CLC files, and convert TS files. Therefore, this study provides a new idea and method for studying such binary files.

In order to development the Aero Geophysical Survey and technology application in the key metallogenic zone ,China Aero Geophysical Survey and Remote Sensing Center for Land and Resourc conducted 1:50 000 aeromagnetic surveys in Dunhuang-Akesai from 2015~2016. They organized ground verification and collected magnetic parameters . In the process, they collected a series of Nb-Ta deposits information and date such as YuShishan ore. According to the classification of different types of deposits, the researcher compared this geological datas with aeromagnetic ΔT characteristics. The result shows these Nb-Ta deposits has typical magnetic field zonation indication on the aeromagnetic ΔT anomaly map. And this research has important guiding significance in expanding the known scale of Nb-Ta ore and in finding new rare metal deposits.

Through investigation and sampling Carya cathayensis kernels and soil of plantations, the heavy metals, Se, organic matter and other indicators in soil were analyzed, and the pollution degrees of heavy metals in soil were evaluated with risk screening values as the criteria. The content of heavy metals, Se, Ge and other trace components in kernels was analyzed, and the relationship between soil and kernels was discussed. The results show that the average values of Cu, Pb, Zn, Ni, Cr, Cd, As, Hg and Se in the soil of Carya cathayensis plantations are higher than those of the average soil of China, especially Cd is 5.6 times that of the average soil of China. Local soil Cd and As in the study area have reached the pollution level while the ecological risk of other heavy metals is slight. Carya cathayensis kernels have low Cd, Hg, Pb, As and other heavy metals content, no excessive heavy metal elements, low ecological risk, and high zinc content, with the potential to develop zinc-rich health food. Carya cathayensis has a significant difference in the absorption capacity of different heavy metals. The absorption capacity of zinc and copper is much greater than that of Cd, Cr and Hg.

The Jiaxie Guyots, located in the western Pacific and belongs to China's contract areas of cobalt-rich ferromanganese crusts, contains strategic metal mineral resources, especially cobalt. Local structures of the guyots play an important controlling role in the macroscopic distribution of these resources, which leads to the research on the tectonic division of the guyots to understand their formation processes and explore mineral resources. In this paper, the gravity and magnetic data as well as topographic data were used to delineate fracture features of Jiaxie Guyots by using the normalized vertical derivative of the total horizontal derivative (NVDR-THDR) edge recognition method and curvature attribute depth inversion method. The minimum curvature potential field separation method was used to delineate the distribution features of flank rift zones and gravity slide areas. The results show that faults of Jiaxie Guyots are mainly NW- and NE-trending, followed by NNW- and NEE-trending. The range of apparent depths of faults is between 3000 and 7000 m, and usually the depth of NW-trending faults are shallower than that of NE-trending faults. The faults of these two different directions intersect to form a conjugate shear fault zone, showing a geese-like arrangement, which provides magma volcanic conduits for seamount formation and rock wall intrusion. The flank rift zones are generally located in irregular terrain extensions of guyots, because they were shaped with magma intrusion and reshaped the seamount as irregularly appearances. During the development of flank rift zones, the gravity slide areas were also formed due to the influence of tectonic activities like earthquakes, and commonly they were located on sharp sides of margins and two sides of flank rift zones. The authors hold that this study of geological structures could give strong support to the study of the formation of Jiaxie Guyots and the comprehensive evaluation of cobalt-rich crust ferromanganese.

Land is an important basic resource for human survival and stable social and economic development, and cultivated land is an integral part of land resources. Ascertaining the quality of cultivated land is of great significance for the scientific and rational utilization of cultivated land and the sustainable development of green ecological agriculture. Using the methods for 1:50,000 geochemical survey and evaluation, this study conducted the quality evaluation and the classification of land in the study area based on the contents of beneficial nutrient elements and toxic and harmful elements in soils and analyzed the distribution and controlling factors of elements in soils. The results of this study are as follows. The soils in the study area consist mainly of alluvial-proluvial deposits from the Yellow River and are primarily used for agriculture and animal husbandry. The soils are not contaminated by heavy metals and are rich in nutrients, with the first- and second-grade excellent soils collectively accounting for 88.85%. Moreover, most soils in the study area have moderate selenium content. Therefore, it is recommended that selenium-rich land resources should be incorporated into the government land planning to develop agriculture with distinctive local features.

Tight sandstone reservoirs have the characteristics of strong heterogeneity,poor physical properties,and difficulty in exploration and development.In order to find the high-brittleness section of tight sandstone reservoirs in the Weibei oilfield and fracture this kind of reservoirs,this paper proposes a method based on ANN (artificial neural network) model for shear wave prediction under the condition of lacking suitable brittleness prediction methods for tight sandstone reservoirs in the Weibei oilfield at present.The predicted value is highly consistent with the measured value,and the brittleness index of each well in the study area is calculated by the elastic parameter method further.For the purpose of improving the accuracy of the brittleness index predicted by this method,X-ray diffraction full-rock analysis of fewer wells in the study area is utilized,and it is concluded that quartz and carbonate rocks are the main brittle minerals of the Yanchang formation in the study area."(quartz+carbonate) content/ total minerals " are adopted to calculate the rock brittleness index and then improve the brittleness index predicted by the elastic parameter method.This technique which takes advantage of the balance between the mineral composition method and the elastic parameter method not only improves the prediction accuracy but also makes up for the lack of array acoustic logging and whole rock analysis data.This method was used to predict the brittleness of tight sandstone reservoirs in the WB2 well area of the Yanchang formation in the Weibei oilfield, and high-brittleness sections of WB52 and WB49 were further chosen to be fractured.It is shown that the production stimulation effect was obvious after fracturing,which is of great significance for guiding hydraulic fracturing.The method and process proposed in this paper have strong application and promotion value.

The complex lithology and pore system in volcanic reservoir result in the complex conductive features of the strata.The authors applied the electric conduction model proposed by Herrick and Kennedy to the volcanic reservoir in Wangfu area based on the theory of pore geometry.The parameters of the model were determined with core litho-electric experimental data in the volcanic rocks of Wangfu area,and a new electrical efficiency model suitable for the volcanic reservoir of complex pore structures was established.Using the new model to deal with the actual well data has achieved very good results.

In recent years,offshore OBC and OBN technology has achieved rapid development.Whether it is OBC acquisition or OBN acquisition,many new equipment and methods were developed.Based on the latest research results and published papers,this paper summarizes the development history and research status of offshore OBC and OBN technology,and summarizes the technology and equipment for offshore four-component seismic exploration and acquisition,as well as processing and interpretation techniques.It is considered that the seabed multi-component seismic is the development trend of marine seismic,because it has the advantages of multi-component data, wide azimuth and wide frequency compared with the marine tow streamer.But the processing of data and conversion wave need to be researched.Now offshore oil and gas exploration is in the stage of complex structures and lithologic reservoirs,as the cost of submarine seismic decreases and the processing technology advances, it will be get more applications.

Based on the heavy metal content data of 1 308 deep soil samples taken from the 1∶250 000 geochemical survey of land qualityin the Bijie area, Guizhou Province, the content distribution and geochemical background characteristics of heavy metals in soil in the area were studied. The geochemical background values of heavy metals in soil in northwestern Guizhou Provinceare significantly higher than those in soil nationwide but are close to those in soil in southwestern China. The heavy metal content in soil in northwestern Guizhou is closely related to the geological background and is significantly different between different geological units. The soil developing in Carboniferous strata has high geochemical background values of Pb and Zn, while the Middle Permian soil formed due to weathering hashigh geochemical background values of Cd and Hg. All these mean that besides heavy metal pollution in soil caused by zinc melting using indigenous methods,another important factor causing the heavy metal enrichment is the high geochemical background values of heavy metals in soil.The statistics show that the management target value of Cd in the Middle Permian weathered soil in northwestern Guizhou is higher than thecontrol value (2.0×10^-6) of Cd stipulated in the Risk Management Standard for Agricultural Land for Soil Pollution in China. It is considered that the differences in geochemical background values of heavy metals in soil between different geological units and their impacts on the ecological environment should be fully considered when determining the management target values of heavy metals in soil in northwestern Guizhou Province.

Many karst fracture-vug reservoirs have been found in the Ordovician carbonate paleo-buried hills in the Lungu area,Tarim Basin.Hydrocarbons are mainly enriched in these fracture-vug reservoirs,which are mainly related to the paleo-underground river system in carbonate paleo-buried hills.The paleo-underground river system is well developed,especially in the western Lungu area.The fracture-vug reservoirs related to the paleo-underground river system have strong longitudinal and lateral heterogeneity,and ascertaining the seismic and geological characteristics of the paleo-underground river system in this area is the key to the efficient development of fracture-vug reservoirs in this area.Based on the characteristics of modern karst underground rivers and the log and drilling data of this area,this study established a geological model of underground rivers for forward modeling.The study results are as follows.The underground river system developing under the tight limestone setting showed continuously linear strong reflections on the seismic profile.The seismic amplitude decreased as the height and width of underground rivers decreased,and higher seismic amplitude corresponded to larger underground river caves and lower filling velocity.The amplitude can accurately characterize the horizontal range of the underground river on the seismic profile.Meanwhile,the frequency and phase can describe the outline of the underground river on the seismic profile,but the outline described was larger than that of the real underground river.The main channels of the underground river system were prone to be filled with mud.By contrast,the branch channels had a low filling probability and thus serve as the main areas for both the occurrence of underground river reservoirs and the hydrocarbon accumulation.

Drilling has revealed that the Archean buried hill of BZ-A has great potential for natural gas exploration.In the target area,the metamorphic rock fracture reservoir in Archean buried hill has many problems such as great buried depth,strong heterogeneity of the reservoir and rapid lateral changes,which pose challenges to the exploration.Based on the study of the genetic mechanism of fractured reservoirs in buried hill,the authors comprehensively analyzed the features of the weathered fractured zone and the inner fractured zone,and established a targeted technical system for the description of fractured reservoirs in buried hill.For the weathered zone fractured reservoir,the pre-stack fracture reservoir porosity prediction technology based on the double-parameter was innovatively used,and the fracture reservoir porosity was predicted by the 3D elastic parameter analysis,and the distribution of the fractured reservoir in the weathered zone was finely described.For the inner fractured zone,the F-K domain coherence enhancement technique was used to improve the imaging of the buried hill.The method of edge enhanced crack detection based on clustering analysis was used to comprehensively characterize the distribution of reservoir in the inner fracture zone.Through the comprehensive application of targeted geophysical techniques, the exploration evaluation of BZ-A has been strongly promoted,thus providing a strong basis for the further exploration evaluation of the target area.

The Neihuang-Xunxian area in Henan Province is located in the Archaean basement uplift area, and has good gravity and magnetic anomalies. It has favorable conditions in the search for sedimentary metamorphic magnetite deposits. However, since the 1970s, due to the limitations of shallow prospecting knowledge, no breakthrough has been made in prospecting. Aimed at the target area of deep magnetite prospecting, the authors detected the plane position (center and boundary) of the concealed magnets in the study area by central recognition technology (analytical signal amplitude ASM) and edge recognition technology (NVDR-THDR), obtained the burial information of the concealed magnets in the study area by Euler deconvolution, and analyzed the homologous characteristics of gravity and magnetic anomalies in the study area by correlation coefficient. Combined with known boreholes, 2.5D fitting inversion of key magnetic anomalies in the study area was carried out, and the scale and spatial distribution characteristics of the concealed magnets were determined. The results show that the buried depth of the concealed magnets corresponding to the main magnetic anomalies is 500~1 200 m, and the ore-bearing property in the deep part is better than that in the shallow part, so the prospecting potential in the deep part is great. On the basis of comprehensive geological and mineral conditions, two deep prospecting target areas of Wagang-Yujian and Nanzhangbao magnetite ores were delineated. It is suggested that they should be the key directions in further deep prospecting with the purpose of achieving a breakthrough in deep prospecting in this area as soon as possible.

The 0~20 cm surface soil, the horizontal profile soil and the 0~200 cm vertical profile soil samples were collected systematically to determine the content of soil fluoride and related indicators, and the distribution characteristics and influencing factors of soil fluorine content in surface soil and profile soil were studied. The results show that the fluorine content in the surface soil of the study area ranges from 448×10 ^-6 to 1 009×10 ^-6, with the average content being 685×10 ^-6. The distribution characteristics of fluorine content in surface soil are obviously restricted by geological and geomorphological conditions. The soil with high fluoride background (>730×10 ^-6) is concentrated in the sub-clay of Qhb group, and the landform is flood plain.The surface soil fluorine is positively correlated with TFe₂O₃ (r=0.76), Mn (r=0.79), CaO (r=0.66) and Al₂O₃ (r=0.59), and negatively correlated with w(SiO₂)/w(Al₂O₃).In the vertical section, soil fluorine is mainly concentrated in 0~155 cm. Iron and manganese oxides are important factors that restrict the vertical distribution of soil fluorine.

The forward modeling is an effective way to study the characteristics of transient electromagnetic (TEM) responses. The high precision and fast 3D forward modeling technology is a hot spot in the study of TEM forward modeling. The multiphysics module in ANSYS software is suitable for the forward modeling of TEM. In this paper, the application method of ANSYS software in TEM 3D forward modeling is introduced by some model examples, including the preprocessing, loading, solution setting and post-processing. The numerical results show that the simulation of TEM forward modeling by using ANSYS software has high accuracy. The TEM forward modeling using ANSYS can improve the efficiency of forward simulation calculation and provide a strong support for analyzing and understanding the characteristics of TEM response.

In the process of hydraulic fracturing for shale gas extraction, the injection, flowback, retention, and absorption of fracturing fluids will cause changes in electric fields in the case of the excitation by the electromagnetic field from an artificial source in a far area or the excitation by the geoelectric field. The time-dependent change in the information on fracturing can be reflected by monitoring the change in weak electric fields above the hydraulic fracturing area. To meet the needs of the real-time monitoring of the fracturing field, this study focuses on the preliminary study of the monitoring technology based on the nodal acquisition devices of distributed weak electric fields. The monitoring system only collects two horizontally orthogonal electric field signals, monitors the real-time information on the electric field within a certain range, and transmits the preliminarily processed data back to the data center in a wireless way. Test results show that the monitoring system has stable performance, a standby time of more than 10 days, and high sealing performance, and is applicable to complex field environments. Therefore, this monitoring system can provide important technical support for obtaining images of fracturing fluid migration in the future.

The phase-shift method is commonly used to extract the Rayleigh wave dispersion curves.However,in the case of a complex wave field,the dispersion spectra calculated using the phase-shift method have a low resolution of Rayleigh wave dispersion energy,reducing the accuracy of the dispersion curves.This study improved the phase-shift method by obtaining the power exponent of the amplitude of each point on the dispersion spectra to improve the convergence and focusing properties of the dispersion energy.The improved phase-shift method was used to process the simulated data of the theoretical stratigraphic model and the actual seismic data of a coalfield in a certain study area.The processing results were compared with the dispersion spectra generated using the conventional phase-shift method.Moreover,the inversion based on dispersion curves of the actual data was conducted to generate a two-dimensional (2D) S-wave velocity section of the study area.As revealed by the study results,the improved phase-shift method can enhance the signal-to-noise ratio of the Rayleigh wave signals in the frequency-velocity domain and improve the resolution of the dispersion energy spectra and the accuracy of the dispersion curves.

This study investigated the speciation of selenium in 51 surface soil samples from the selenium-rich cultivated land in Linhe District, Bayannur City, Inner Mongolia and explored the content and speciation of selenium and their influencing factors. The results showed that the surface soil in the study area had total selenium content of (0.19~0.48)×10^-6, averaging 0.33×10^-6, indicating a soil environment with moderate-high selenium content. Among the seven forms of selenium speciation, major forms include the residue, humic acid bound, and strong organic bound forms. The remaining forms, namely water-soluble, ion exchange, iron-manganese oxide bound, and carbonate bound forms accounted for only 13.67%. Water-soluble selenium consisted mainly of moderate-high water-soluble selenium (92.16%), with the absence of water-soluble selenium deficiency. The selenium content in each form was highly correlated with the total selenium content in the soil. The organic matter content, pH, Eh, and CEC had different effects on the distribution characteristics of selenium speciation.

Kriging interpolation algorithm is the basis of 3D modeling of coal seam occurrence form in fully mechanized mining face based on traditional geostatistics. However, the variation function model selected and fitted by Kriging interpolation algorithm cannot reflect the actual geological characteristics and the variation trend of spatial data. In this paper, UPSO-Kriging interpolation method is thus proposed: PSO algorithm is optimized to solve the problems of slow convergence and easily falling into local solution, and the optimized algorithm UPSO is then introduced into Kriging interpolation to solve the variation parameters and fit the variation function model, thus realizing the height prediction of each layer in the coal seam structure of working face. In addition, with DEM model established on regular grid method, the three-dimensional visualization of the occurrence form of coal seam in fully mechanized mining face is realized by using Three.js, which provides scientific basis for transparent mining, intelligent mining and quality mining of coal enterprises.

The present paper makes a brief description of the progress of several main electric methods which havebeen developed quite rspidly since 1980's.They include induced polarization method,frequency spectrum IPmethod,trandient electromagnetic method, controlled-source audio-frequency magnetotelluric method and GPR.