Located in Yinkeng Town, Yududu-Ganxian ore concentration area, east Nanling Mountains, Southeast China, the Yinkeng Demonstration Area has a good prospect of mineralization, where the granite is closely related to mineralization. Therefore, systematic exploration of granite distribution is one of the key problems in deep prospecting. In this paper, the spatial distribution characteristics of regional granite were comprehensively studied by using gravity and magnetic data, combined with physical, geological, electrical and seismic data. Firstly, the planar distribution of six granite masses in this area was studied and deduced, among which Jiangbei rock mass, Changtan rock mass and Gaoshanjiao rock mass are partially concealed, whereas Liumukeng rock mass and the shallow and deep rock masses of Ge’aowei are completely concealed. It is concluded that the rock mass mainly trends in NE and NNE direction. Then, four gravity (or gravity and magnetic) profiles in the study area were used to invert the spatial distribution of granite, which further revealed the spatial distribution characteristics of the above six rock masses. The inferences are consistent with those obtained by plane gravity and magnetic method as well as the results derived from electrical method and seismic profile interpretation.

It is difficult to accurately predict the dolomite tight oil reservoir which has the characteristics of low porosity and low permeability by using the post-stack inversion,due to the small difference in acoustic impedance between the reservoir and its surrounding rock.Therefore,more abundant elastic information is needed.AVO inversion is an effective means to extract elastic information from pre-stack data.However,due to the noise and other factors,the pre-stack inversion equation has a strong ill-posed problem.Bayesian theory allows the construction of a regularization term by introducing a priori information about the model parameters,thereby effectively reducing the ill-posed problem of the inversion.Therefore,the modified Trivariate Cauchy constraint and the modified low-frequency constraint factor is introduced into the objective function,which can improve the ill-posed problem of the inversion,thus upgrading the accuracy of the inversion results.The iterative idea is used to address the non-linear nature of the proposed inverse operator.The P and S-wave velocity is updated in the iterations,which leads to more reliable results when applied to real data.Both the model data tests and the field data applications prove the validity and stability of the proposed method.Statistics show that,by using the proposed inversion method,the prediction accuracy rate of the reservoir thickness is as high as 89.5%.Therefore,this method has important reference significance for the exploration of similar siliceous reservoirs.

Xiaoshan Mountain widely covered by the Quaternary sediments is located in the west of Henan Province. Its north part is ravines crossbar, and the surface vegetation grows fully and covers the surface heavily. In order to investigate the effectiveness of the earth electrochemical method in the search for gold deposits in the Xiaoshan loess-covered area in western Henan, the authors selected Shizhaigou gold deposit which is buried in loess to carry out the feasibility test of ore prospecting, and conduct geo-electrochemical prospecting in the south of the Shillongshan gold polymetallic mineral survey area and its adjacent area of Xiaoshan. The study revealed that the electrochemical composite anomaly in the development area of the Au deposit in Shizhaigou is obvious , the elements are well correlated and they have good nesting and zoning relationships. The authors analyzed the trace element content characteristics (fractal, coefficient of variation and extraction ratio of the geoelectric extraction) extracted from the geoelectricity of Shilongshan census area and found that it has similar geoelectricity anomaly patterns to the Shizhaigou gold deposit. In addition, the authors used Surfer software to draw the contour abnormal map and, in combination with previous research results, initially verified the surface of well-arranged 45-47 surveying points along No.02 line through surface engineering, thus determining an industrial gold orebody with good reserves. It is thus proved that the measured and inferred faults F1-1 and F20 do exist. The results provide a theoretical basis for electrochemical prospecting in the search for deep deposits in the Shilongshan area and the periphery of the Shizhaigou deposit, and also provide new ideas for the prospecting work in the loess-covered loess area.

There are several Ordovician carbonate fractured-vuggy type oil and gas fields in the Tarim Basin.With the continuous development and production of the reservoirs,the small and medium sized fractured-vuggy systems have become the main targets of capacity development.In the process of exploration and development,due to the influence of complex formation velocity,there is a certain error in seismic migration data,which often leads to the failure of drilling.In this paper,an efficient drilling track optimization method based on VSP data for seismic data processing is proposed.First,the VSP velocity and the new triangular mesh model are used to effectively correct the original seismic migration velocity field,and then the modified anisotropic parameter field is used for quick migration.Secondly,the structural characteristics of the whole strata are analyzed in the new data,the positions of the reservoirs are predicted,and the targets are determined.Finally,according to the engineering and geological conditions,the most economical optimal design of the drilling trajectory is used to drill into the target.The application shows that the relatively good effect is obtained in Tazhong area of Tarim Oilfield,and the imaging quality of seismic data has been improved obviously.After well track adjustment,the rates of drilled reservoir and the directly put on production are increased by 16% and 13.2% respectively.The low cost and effective development plan of the oilfield is effectively promoted and implemented.

Because of the particular depositional mode,black organic matter-rich shales are generally characterized by strong velocity anisotropy;however,most researches on shale are on the basis of isotropic theory,which obviously ignores the geological characteristics of shale.In this paper,anisotropic parameters of shale are calculated by combining rock mechanical measurements in the laboratory with the empirical methods from the literature.On the one hand,the parameters are used to investigate their effects on the calculation of velocity versus bedding direction and rock mechanical parameters,and the result shows that the anisotropic characteristics of shale cannot be neglected when the dip angle of the strata is large.On the other hand,little difference between AVO responses of anisotropic and isotropic methods when the incidence angle is less than 40° indicates the feasibility of isotropic pre-stack seismic inversion in predicting shale "sweet spot".

Turquoise, a phosphate mineral assemblage of Cu, Al, is a valuable gem mineral. The western margin of Wudang Uplift in Hubei-Shaanxi border is an important producing area of high quality turquoise. Based on an analysis of geological characteristics and geological conditions of turquoise deposits, the authors hold that turquoise deposits mainly occur in lower Cambrian (carbon-bearing) siliceous rocks and are controlled by fault structures. Combined with the geophysical and geochemical characteristics of the deposits, the authors point out some ore-hunting indicators of turquoise deposits in this area as follows: Cambrian (carbon-bearing) siliceous strata, well-developed fault structures, areas with high Cu content, and areas with high radioactivity (high U content). According to geological, geophysical and geochemical data, the first and second order minerogenic prospective areas of turquoise were delineated.

To understand the deep structure characteristics and the distribution and lithology of the main Devonian-Permian shale gas strata on the southwestern side of Southeast Hunan Depression, the authors carried out the processing and qualitative-quantitative analysis of data from four magnetotelluric sounding profiles in Yuanjia syncline. Based on the apparent resistivity section, impedance phase analysis and two-dimensional continuous media inversion of magnetotelluric sounding data and combined with the geological characteristics and physical properties of the study area, the authors found out the location, nature and development characteristics of main fractures as well as the spatial distribution of the main geological formation (electrical layer). On such a basis, the favorable shale gas strata exploration was discussed. The results show that the majority of the faults trend in SN, NE and NW directions in the Yuanjia syncline, showing structures such as "listric style" and "flat and ramp style" in the section. The Upper Permian Longtan Formation has high quality gas-bearing coalbed and good exploration prospect of coalbed methane. The low resistance shale of the lower member of Middle Devonian Qiziqiao Formation is continuous and thick, and hence it can be regarded as a favorable exploration shale formation.

Based on an analysis of the conditions of geothermal formation in Haishiwan area, the geophysical prospecting methods of CSAMT(Controlled Source Audio Magnetotelluric), MT(Magnetotelluric)and gamma ray spectrometry were used to verify each other and, as a result, cover layer thickness, the buried depth of thermal reservoir and the fracture location were found, which avoids one-side trend and blindness of a single method and provides a basis for drilling and obtaining good results in exploration. Drilling verification shows that well hole strata and water-bearing horizon are basically consistent with the results of geophysical inference, the water temperature of well mouth is 60℃,the water gushing amount is 90 m ³/h, and the thermal reservoir is a fault type banded reservoir. The result provides valuable experience and example for geothermal exploration in similar areas in the future.

The New England Orogen(NEO)is located in East Australia. Due to the numerous copper polymetallic deposits or ore spots and the complicated evolution history of tectonic activity, NEO shows the high exploration potential for copper polymetallic minerals, even large-sized deposits. The airborne electronic anomalies were delineated by airborne time-domain electromagnetic method. Based on the aerial electronic anomalies and using a method called "Seeking Common" with the known copper polymetallic ore spots, the authors performed the optimization and evaluation of copper polymetallic minerals in an exploration license within quite difficult topographic conditions for ground exploration in NEO. Using the airborne time-domain electromagnetic method, the authors rapidly and effectively determined and optimized nine copper polymetallic exploration targets. Those targets were classified into three levels: Level Ⅰ, Ⅱ, Ⅲ. Finally, and there were three, five and one targets for Level Ⅰ, Ⅱ, Ⅲ respectively. In a word, the work completed in this paper is expected to provide a referable case for rapidly and effectively conducting optimization and evaluation of copper polymetallic minerals in some special areas within difficult topographies for ground exploration both in China and abroad.

The ratio methods are one sort of edge recognition methods by using potential field, which contains the Normalized Standard Deviation method (NSTD), Tilt Angle method (Ta) and Theta Map (cosθ). If the denominator of ratio method closes or even equals to zero in the process of calculation, the result obtaining from ratio methods is unstable and may even bear little resemblance to the true geology. In order to relief this problem, a regularization factor, which is greater than zero, is added in the denominator of the ratio methods’ formula, which not only enhances the numerical stability of the ratio methods but also improves the accuracy of some ratio edge recognition methods. The stability, accuracy and effectiveness of the new method is verified by testing synthetic models and calculating real data. Also, the introduction of the regularization factor also can improve the effect of recognizing edge by the second-derivative edge recognition methods, which is based on the ratio methods, such as the Total Horizontal Derivative of the Tilt Angle (Ta-THDR). The idea of regularization can not only solve the numerical calculation problem of the ratio methods of edge recognition for potential field, but also solve the numerical calculation problem of all ratio methods.

Potential field continuation is one of the important methods of gravity and magnetic potential field data processing, and obtaining high-precision continuation results is particularly important for subsequent data processing and interpretation. Starting with the basic formula of plane potential field continuation, the authors analyzed the factors and the stability that affect the accuracy of continuation results in space and frequency domains. Using the theory model, the authors investigated the buried depth of the top surface of the field source, the length of the section, the method of edge enlargement, the size of the window, the dot pitch and the continuation height, and compared the different influences of these factors in space domain and frequency domain. The theory model test shows that the dot pitch and continuation height have the greatest influence on the continuation results, followed by the section length, the method of edge enlargement and the size of window, with the top surface of the field source exhibiting minimal influence. With the increase of the top surface’s depth, the continuation results accuracy is reduced. Increasing and expanding the length of the section will improve the accuracy of the field continuation results. Selecting the appropriate sliding window can improve the calculation efficiency, with the increasing window radius, the accuracy of the field continuation results is improved, and it can generally be chosen as 20 times of the continuation distance. The accuracy of the field continuation results have similarity in space domain and frequency domain; nevertheless, in space domain, the continuation error is very large when the continuation distance is less than 1 time of the dot pitch, so it needs to encrypt the dot pitch by using the interpolation method in this situation.

The development of geochemical exploration technologies unaffected by marsh microorganisms is necessary for improving the prediction of wells and exploring natural gas hydrates in mid-latitude permafrost areas. The potential of thermal-release mercury as a new tool for the investigation of gas hydrates in permafrost areas was studied in this paper. The study area, covering 150 km ², is located in the alpine-arctic swamp landscape of the Qilian Mountain. The sampling density and depth were 1 or 2 points/km ² and 60 cm, respectively. In total, 300 soil samples were collected and the mercury vapor analyzer was used to measure soil thermal-release mercury. The results indicate that thermal-release mercury anomalies were identified in the gas hydrate deposits. There is maximum thermal-release mercury over the gas hydrate boundary and minimum thermal-release mercury with pinch-and-swell from over the gas hydrate reservoir. The maximum thermal-release mercury is 127.37×10 ^-9, with the average being 32.59×10 ^-9, and the threshold of anomaly is 39.24×10 ^-9. A comprehensive interpretation was conducted based on geological and geochemical survey results. The relationship between the hydrocarbon of gas hydrates anomalies and thermal-release mercury anomalies was further explored. The authors propose a geogas migration mechanism of soil thermal-release mercury in the soil above the natural gas hydrate deposit. The anomalies near the ground surface of the Muli coalfield in the Qilian Mountain were derived from the deep hydrate deposits and fault structures, which were not affected by marsh microorganisms, and they have important reference value for natural gas hydrate exploration in permafrost areas.

In order to identify the reasonable sampling density for land parcel scale geochemical assessment on land quality in Northeast China Plain, the authors studied spatial variability of elements in soils as well as reasonable sampling size based on classic statistics and conducted a thorough comparison of interpolation accuracies at four sampling densities in a typical area in Gongzhuling City of Jilin Province. As the area is dominated by flat land and the soils parent materials are mainly homogeneous sediments, most of elements in soils in this area display a minor to moderate variability, Cd and Hg which are sensitive to human activities have a significant higher coefficient of variation of 35.3% and 136.6%, respectively. Classic statistics show that sampling size of 80 is sufficient for providing a reliable estimation of mean and variance for the elements concentration in soils in this area ( under a P value of 95% and E_r tolerance level of 30%); however, classical statistics could not make out the spatial allocation of soil properties at the unsampled locations. By comparing the relative error of spatial interpolation, the predicted value for land parcel and the predicted classes at four sampling densities, the authors suggest that the reasonable sampling density is 8 samples per square kilometer for land parcel scale geochemical assessment on land quality in the study area and similar areas in the Northeast China Plain, considering the tolerance level of E_r (relative error) for the geochemical assessment on land quality. The results obtained by the authors may help optimize soil sampling density in land parcel scale geochemical assessment.

The detection accuracy of the array and the study of data processing methods about the three-potential observation system always constitute a hot spot for geophysicists, and there are also many controversies. In this paper, forward modeling results are used to discuss the detecting accuracy of three devices under several possible geological conditions in karst area. It is found that β array and γ array are significantly more precise than wenner α array; then, the ratio parameter (T) is composed of forward’s result. With least-squares inversion on the data of T, the authors found that the result of T’s least-squares inversion is consistent with the inverse result of apparent resistivity, and the result of inversion result is better than the T contour map in an area where the noise is large. For the result of the T’s least-squares inversion, it can be used as a basis for judging the anomalous body characteristics and the inverse result of apparent resistivity, and it can also be used to make up the effect of noise on a single device. Taking the hydrogeological survey of a certain place in Yima as an example, the authors found that the result of the T’ least-squares inversion in the low-water-resistance region is small, the abnormal bodies’ boundaries are accurate, and the structural features are obvious. It is shown that the result of the T least-squares inversion is very useful for data processing and interpretation, and therefore researchers should pay attention to it in future.

The LSQR method has the advantages of high computing efficiency and low memory requirement, and is thus suitable for solving large-scale ill-posed problems. In order to discuss its application in the stability and reliability of potential field inversion, the authors, on the basis of two synthetic models data with different noises as the object of the experiment, studied Tikhonov regularization and LSQR method, and the results show that the LSQR method can satisfy the requirement for solving potential field inversion with the regularization solution. In comparison with Tikhonov regularization, the maximum relative error of the LSQR method is only 0.36%, indicating that the use of LSQR method to solve potential field inverse problems is feasible. It was applied to 3D inversion of gravity in Ya’an area of Sichuan basin, which greatly reduced computation cost and obtained the distribution of sedimentary basins and main faults in the area, thus providing strong support for shale gas target area optimization.

Accurate first-arrival picking plays a significant role in microseismic data processing.The dominate methods,i.e.,short-term average to long-term average ratio (STA/LTA) and the autoregressive (AR) model using Akaike Information Criterion (AIC) algorithm,are not optimal for picking up high-noise data.In order to optimize the first-arrival point estimation of high-noise data,the authors propose an improved picking method based on wavelet multi-scale analysis (WMA) and AIC algorithm.In this algorithm,WMA is used to decompose the high-noise three-component (3C) microseismic data,and the actual calculation data are reconstructed based on the approximation data.Then the maximum value of the absolute value is calculated to constrain the AIC calculation data segment;on such a basis,the global minimum value of the AIC sequence is selected as its first arrival point.The improved algorithm is verified by both synthetic data and field data in this paper.The results show that the improved first-arrival picking algorithm can be effectively applied to high-noise three component microseismic data processing and greatly enhance its accuracy(the error range is 0.25~0.5 ms).

The topographic relief of seabed and the velocity of sub-seabed layers have great influence on imaging quality of OBC data.Estimating sub-seabed velocity models in shallow sea areas can be used not only for static correction of OBC data but also for calculation of such objects as seabed reflection coefficients,merging of OBC dual-geophone seismic data,and multiple suppression.However,there are few velocity model building methods using OBC seismic data in shallow sea areas.In this paper,the authors propose a 3-D sub-seabed velocity model building method using the first arrival times of OBC data in shallow sea areas.The new method includes shot positions correction and fast 3-D velocity inversion method using first arrival times.For the convenience of velocity model inversion,shot points are moved from their original positions to the seabed according to the diving wave ray equation.The fast 3-D velocity inversion method using the diving-wave first arrival times and offset information doesn't need ray tracing.So the new method is faster than the traditional ray tracing inversion methods.The authors applied this method to the field OBC seismic data acquired in shallow sea of the Shengli Oilfield.The static correction of OBC seismic data was performed using the inverted velocity method and the results show that the method is correct and effective.

By comparing the phase difference between OBN hydrophone data (P) and geophone data (Z),the similarity coefficient criterion is improved and introduced into the phase matching of OBN data,so as to eliminate the phase difference between the two geophones data.On the basis of frequency matching,the amplitude matching of geophone data is carried out by matching filtering method,and then the dual-sensor data PZ are merged to suppress the reverberation.The theoretical model test and actual data processing show that the improved similarity coefficient method can correct the phase difference of land geophone data quickly and accurately,and the PZ combination has achieved good results in suppressing the reverberation.

This paper introduces the development and integration of the aeromagnetic measurement system for unmanned helicopters. Through integrated assembly testing for unmanned helicopter flight platform and aeromagnetic survey instrument and its magnetic interference testing and magnetic compensation testing, successfully integrate the aeromagnetic instrument with the unmanned helicopter flight platform to develop an aeromagnetic measurement system for unmanned helicopters. The system has completed flight test and flight application work. Compared with the contour map of previous geomagnetic anomalies in measuring area, the reflected geomagnetic field characteristics in aeromagnetic anomaly contour map obtained in flight application are basically the same which proves the effectiveness of the system. The unmanned helicopter aeromagnetic measurement system provides an efficient, convenient and scientific means of work for small exploration blocks with complex topography and harsh environment which need to be carried out aeromagnetic measurements survey.

The ZTEM (Z-Axis Tipper Electromagnetics) is a frequency-domain airborne electromagnetic method that results from natural sources. It has the feature that the vertical component of magnetic field is measured from a moving helicopter platform and the horizontal component of magnetic field is measured at a reference station on the ground. In addition, it has the advantages of deep exploration, fast speed, low cost and large coverage area. This paper realizes the 2D finite difference forward modeling and NLCG inversion of ZTEM. The object of the study is the tipper data. The direct calculation of Jacobian matrix is avoided by solving the "quasi-forward" problem in the inversion process. The stability and reliability of the 2D NLCG inversion of ZTEM tipper data are verified by the trial calculation of synthetic data inversion of theoretical model. A comparison with the inversion result of impedance data of magnetotelluric (MT) TE mode shows that the ZTEM tipper inversion is superior to the MT impedance inversion in the constraint of the lateral boundary of the anomalous body.

In this paper, the authors processed the navigation data obtained from Alxa Left Banner in Inner Mongolia to summarize the process and main reasons for the formation of the negative value. The results are as follows: ①The nature of radioactive decay has statistical fluctuation, and this property plays an important role in the processing of revised data, especially in areas with low radionuclide; ②A slight negative value of uranium counting rate will occur after background correction and cosmic ray correction, and will increase negatively after atmospheric radon correction; both ends are prone to form high value false anomalies and continuous negative anomalies. After the peel correction, the number of negative values increases greatly, while the height correction and content conversion no longer produce new negative values, but only change the negative values. The authors found that zeroing the negative values generated by the correction process can eliminate high value false anomalies produced by atmospheric radon correction, and that continuous zero value data appear, which is inconsistent with the objective laws. Therefore, normalization method is proposed to eliminate negative values. This method can eliminate the negative value quickly and reasonably, and can control the changed value within a smaller value. In addition, it makes up for the lack and the deficiency of the negative value processing method.

In order to meet the needs of development of high-precision airborne gravimeter , the sub-index design and analysis of high-precision airborne gravimeter were carried out, which provided the basis for the design of high-precision airborne gravimeter system. Based on the mathematical model of airborne gravimetry, this paper summarizes the main errors affecting airborne gravimetry, uses the theoretical model formula, deduces the error models of various influencing factors, and carries out the analysis and study of various errors, and sets reasonable sub-index by combining the relevant theoretical formula of airborne gravimetry. Accuracy can effectively control the sub item errors and ensure the accuracy of airborne gravity measurement is better than 0.6×10 ^-5 m/s ².

The authors adopted TSP, ground penetrating radar and infrared acquisition technology to tunnel advance prediction of Thousand-island Lake water distribution project. Several conclusions have been drawn as follows: Firstly, TSP has a low resolution for detecting karst caves but has a good effect for detecting fractured rock mass, its anomaly features show that the Young’s modulus, density and P-wave velocity are low. Secondly, ground penetrating radar is very suitable for tunnel prediction in limestone area, radar reflection profile exhibiting strong amplitude and hyperbolic event usually indicates the development of karst caves. Thirdly, infrared acquisition is greatly influenced by hydration heat of shotcrete in tunnel so that it cannot be used alone in tunnel geological prediction; the defect is especially obvious when the quality of surrounding rock is poor.

Ground penetrating radar (GPR) is an important shallow geophysical detection method for detecting underground structures and their distribution regularity.It has the advantages of high resolution,non-destructiion,strong anti-interference capability and intuitive results,and is widely used in the field of engineering geophysical exploration.In order to improve the understanding of the characteristics of the underground pipeline radar image,determine the location of the abnormal body of pipeline,and improve the interpretation precision of GPR,the authors used FDTD method to detect the underground pipeline,which includes the numerical simulation of the factors affecting the depth of pipeline,material,filling material and pipeline disease.On such a basis,a forward modeling synthetic library of underground pipelines was established to guide the interpretation of the ground-penetrating radar images.The field pipeline detection results show that the ground penetrating radar can accurately detect the buried position and operation status of underground pipelines,and provide a basis for future maintenance.

In the detection of a subsidence area, for the purpose of accurately determining whether there are holes in the backfill area, the CSAMT and the transient electromagnetic method shall be selected for integrated detection based on the geological and field conditions, and the analytical results show that the detecting results of the two methods are basically identical, as shown by analyzing the abnormal characteristics of the typical sectional profile, but each has its own characteristics: The depth of CSAMT method is deeper than that of TEM, and the judgment of the abnormal area is relatively accurate, the resolution of TEM is better than that of CSAMT, but the detection depth is shallow, the depth of exploration is easily affected by the physical properties of the medium within the target depth and the shallow has a blind area. The drilling through the abnormal areas of the judgement shows that the detection results are accurate, and that the integrated geophysical method is accurate and effective in the survey of collapse of backfill area.