Mineral resources are the lifeblood of national economic development. Electromagnetic method is one of the most effective methods to search for mineral resources.With the depletion of shallow resources, developing a both large-depth and high-precision electromagnetic method has become big challenge for all countries in the world, which is also the research hotspots. Aiming at the problems of shallow depth and low precision of the original artificial source frequency domain electromagnetic methods,from theory, method, technology to application, the author carried out systematic research and invented WIDE FIELD ELECTROMAGNETIC METHOD. It is a great leap forward for the development of frequency domain electromagnetic method from coarse to fine. As a result, the achievements of "large depth and high precision wide field electromagnetic exploration technology and equipment" have been formed, it won the First Prize of National Technological Invention in 2018.Wide field electromagnetic method provides a new technical means for oil and gas exploration, deep prospecting, coal mine water disaster detection, geological disaster prevention, fracturing monitoring and urban geophysical exploration. It has strongly supported the "deep ground" strategy oriented to the major needs of the country.The papers collected in this column are mainly distributed in the technical research fields of solid mineral, shale gas and geothermal exploration, fracturing monitoring and airborne geophysical application. This paper focuses on these papers and discusses the development of the theory and application of wide field electromagnetic method.

After the major breakthrough in oil and gas was obtained from the Well Anye 1, the Ministry of Natural Resources increased the residual shale gas and oil and gas exploration and development of 7,800 square kilometers in the Wuling Mountain. The Wulong Mountain area has complex geological structures, undulating terrain and large areas of carbonate rock, which has led to great challenges to traditional oil and gas exploration methods based on seismic exploration. Wide field electromagnetic method has the characteristics of green, high efficiency and low cost, and hence has become one of the powerful methods for oil and gas exploration and is now being widely used in shale gas exploration in southern China. It is a favorable method for shale gas exploration in southern China. The strata in Tongzi Guizhou are relatively stable, and the organic carbon content in the upper Ordovician Wufeng-Lower Silurian Longmaxi Formation is high. Through surface sample collection and well logging data analysis, the organic shale in this formation shows obvious low resistivity characteristics, which has the physical conditions of electromagnetic exploration. The wide field electromagnetic method was used to carry out shale gas exploration in Tongzi area of northern Guizhou, which overcame the complex influence of topography, carbonate rocks and structure. It is found that the structure pattern of Tongzi area is characterized by "depression and uplift" from northeast to southwest. The spatial distribution characteristics of the Wufeng-Longmaxi Formation in the target layer were detected, and four favorable areas for shale gas exploration were delineated. The prediction of shale gas exploration target area by wide area electromagnetic method is expected to help realize the breakthrough of shale gas exploration and development from point to surface in Wuling Mountain area and promote the development of clean energy industry along the river.

Linze County is located at the southwest edge of Zhangye-Minle basin and along northern central Qilian fold belt and has a good prospect for development and utilization of geothermal resources. The authors analyzed regional geological structure and hydrogeological characteristics of the study area and investigated existing geothermal well and preferred working area by the wide field electromagnetic method. Through comprehensive analysis and on the basis of regional hydrogeologic and geophysical exploration results, the distribution characteristics of geological structure and rock mass in the study area were interpreted and inferred, the prospect of geothermal exploration in the research area was analyzed and evaluated. Meanwhile,the "geology-geophysical-geothermal energy" model of geothermal exploration in the study area was preliminarily constructed. This model provides reference and guidance for geothermal exploration in the study area and adjacent areas.

This study area is not only covered by Quaternary strata,with unclear stratigraphic division and complex faults,but also strongly interfered by high-voltage transmission lines and corridors in deep geothermal exploration.Through collecting and analyzing the existing geological materials in the survey area,the geothermal metallogenic model of the area was constructed.The combination of high-density electrical method and wide field electromagnetic method was used to improve the resolution of the results,divide the geological information such as stratigraphic and fault,and infer the favorable position of geothermal mineralization.It has been proved by drilling that good geothermal exploration effect can be achieved.

In order to extend the construction field of the wide field electromagnetic method and break through the restricted area of the wide field electromagnetic method application under extremely cold conditions, the authors studied the experimental technology of wide field electromagnetic method under extremely cold conditions. A comparative test was carried out between the exposed permafrost in spring and the extremely cold conditions and the exposed permafrost and the unexposed permafrost in the extremely cold conditions. The feasibility of construction under extremely cold conditions was explored. Various warm-keeping methods and measures to overcome the high resistance of frozen soil layers were applied in practice, and a set of exploration technological means under extremely cold conditions were summarized,which can be used to carry out the wide field electromagnetic method construction under extremely cold conditions so as to ensure the quality of data.

Based on an analysis and summary of the physical properties of the gas-bearing shale layer in Zhongmu area of Henan Province, the authors used the wide-area electromagnetic exploration technology to detect shale gas in the low-resistance coverage area of the Nanhua Basin, obtained the distribution regularity and characteristics of the stratigraphic resistivity within 5km under the work area, and ascertained the structural distribution of the work area. In addition, the development characteristics of gas-bearing shales were revealed, with the main target layers being the Permian Taiyuan Formation, Shanxi Formation, Upper Shihezi Formation and Lower Shihezi Formation. The results show that, in the low-resistance coverage area, the wide-field electromagnetic method is an effective detection method to obtain the buried depth and distribution range of deep gas-bearing shale in the Nanhua Basin, providing geophysical parameters for the evaluation of favorable zones in the later period and the optimization of shale gas layers in the block.

The wide field electromagnetic method establishes a harmonic electromagnetic field through an artificial ground field source,sends alternating currents of different frequencies to the ground,and surveys one or more electromagnetic field components to detect geological targets of different buried depths with wide field apparent resistivity.In this method,high power and strong artificial field is used to suppress the interference field to improve the signal-to-noise ratio.Under the environment of complex human noise interferences such as high voltage line,railway,factory building,mining area,substation and periphery of the city,the amplitude of interference field signal reaches hundreds or even thousands of microamplitude,and its intensity is greater than that of wide field electromagnetic artificial field signal,so it is difficult to achieve the suppression effect.In this paper,the large-scale exploration of geothermal resources around a city was taken as an example to study the application of wide field electromagnetic method in the complex electromagnetic interference environment,with good quality observation data obtained.This example provides a direction for the application of wide area electromagnetic method in the complex electromagnetic interference environment.

Jiaojia and Sanshandao fault zones are famous gold ore-forming zones in Jiaoxibei region. In recent years, the deep exploration results are remarkable. At present, the borehole has reached the depth of 4 006 m. The previous geophysical exploration methods have poor deep exploration effect, so effective deep exploration geophysical technology is urgently needed. The wide field electromagnetic method is applied to the known section of Jiaojia and Sanshandao fault zones. The section reveals that the characteristics of the low resistance zone formed by the two major fault zones are obvious, which truly reflects the distribution of underground electricity; the distribution of apparent resistivity high resistance and low resistance reflects the distribution of Linglong granite body and metamorphic rock mass; meanwhile, the section clearly shows the intersection of the two major faults at a depth of 4 km. The section provides the basis for the fault characteristics between Sanshandao and Jiaojia faults. The application test shows that the wide area electromagnetic method has a large detection depth and strong anti-interference capability, and hence it is a good non-seismic geophysical method for detecting the low resistance fault zone in the magmatic rock distribution area of Jiaoxibei region.

The resource exploration of Hewa area in Liaoning Province was carried out. On the basis of the understanding obtained, the wide field electromagnetic method was used to explore the favorable geological interface for mineralization in this area. The exploration depth and accuracy were greatly improved comparing with the previous work, which was of great significance to the exploration of deep mineral resources in this area. It is the theoretical study of polymetallic ore formation in Hewa area and the gold mineralization model in eastern Liaoning. The establishment of the metallogenic model provides a more accurate geophysical basis.

In order to establish a geological-geophysical prospecting model suitable for the deep gold deposits in Jiaoxibei region of Shandong,the authors performed a variety of electromagnetic exploration technologies on known geological sections,and selected a deep geophysical exploration method suitable for the concentrated gold deposits in the strong interference zone of Jiaoxibei region.The contrasting and analyzing of the exploration results of wide field electromagnetic method,magnetotelluric method (MT),controlled source audio-frequency magnetotelluric method (CSAMT) and spectrum IP method (SIP) show that,compared with MT,the wide area electromagnetic method has the advantages of high resolution,high data accuracy,strong anti-interference capability and high construction efficiency,and compared with CSAMT and SIP,the wide area electromagnetic method has large exploration depth and strong anti-interference capability,high data accuracy and other technical advantages.Various methods can reveal the spatial distribution characteristics of strata,rock masses and fault alteration zones within 2km of the profile line,but fail to provide deep physical parameters.In contrast,the results of the wide field electromagnetic method not only show the changing rules and characteristics of the shallow central resistivity,but also effectively reflect the changing characteristics of the deep fault alteration zone.The results show that the wide-area electromagnetic method is an effective exploration method in this comprehensive geophysical research,and it also provides accurate geophysical parameters for deep mineralization prediction and model establishment.

Based on the basic theory of wide-field electromagnetic method (WFEM) and combined with the current problems of resource exploration and the development status of aviation geophysical prospecting, the authors mainly deal with the aviation wide-area electromagnetic method in three main aspects as a preliminary exploration: basic theory, equipment research and application testing. It is held that the quality of aviation wide-area electromagnetic data collection is susceptible to aircraft flight attitude and aircraft body noise, and high frequency bands greater than 100 Hz have better data quality and practical engineering application feasibility.

Based on the Maxwell equations,the authors introduced the vector potential and scalar potential coupling equations,and used the finite element method to study the three-dimensional numerical simulation of WFEM.In a synthetic test,the correctness of this algorithm was verified by a uniform half-space model with analytical solutions.Then the detection depth of the WFEM was simulated using the anomalous bodies at two different depths.The numerical simulation results show that the WFEM don't affected by the near region of the field source and has the characteristics of large depth,it can provide theoretical and methodological support for deep earth resource exploration.

In the exploration of metal mineral resources,physical exploration is usually difficult but of low cost.Along with the increasing depth of the exploration and serious influence of human disturbance factors in the mining area,the difficulties and cost of physical exploration have been increasing.What's more,due to the limitations of the technical conditions such as the precision and power of the instruments and equipment,the geological effectiveness is getting worse and worse by adopting the general geophysical prospecting method.However,the wide field electromagnetic method has such advantages as great detective depth,high speed,low cost,high resolution and precision,and strong anti-interference capability,and hence can be effectively applied to metal mineral exploration,and this has been proved many times.Therefore,it is advisable to develop new methods,new technologies and new instruments represented by the wide field electromagnetic method in the investigation of deep orebodies as well as crisis mine resources.This paper introduces the basic principles,working methods,application principles and conditions of wide field electromagnetic method,analyzes and studies the case of a gold mine in Henan Province,and expounds the effectiveness of the wide field electromagnetic method in deep exploration of metal deposits.

By using the wide field electromagnetic method to measure and study many metal mines in the southeast of Liaoning Province,researchers can have a fairly clear understanding of the formation of deep strata contact surface and structural development in the southeast of Liaoning Province.Through the deep understanding of the formation time of the ancient rift and metamorphic core complex,the process of rock circle uplifting and dynamic mechanism in the east of Liaoning Province,the authors applied wide field electromagnetic method and provided more accurate geophysical basis for mineralization,ore control and metallogenic mechanism in this area,which is of great significance to the establishment of metallogenic model of metal deposits in southeast Liaoning Province and the exploration of deep mineral resources.

The Shanggong gold ore concentration area is located in Xiong'ershan area of western Henan Province, and lies on the south margin of North China block. Combined with regional geological and geophysical data, the authors used the wide-field electromagnetic method to measure the Shanggong ore concentration area, and systematically processed and quantitatively retrieved the wide-field electromagnetic data. According to the inversion profile, the electrical characteristics of middle and low apparent resistivity in this area were inferred to be gneisses of Shibangou Formation of Neo-Archean Taihua Group, the high apparent resistivity shows andesites of Xushan Formation of middle Proterozoic Xiong’er Group, and middle and high apparent resistivity shows intrusions of Proterozoic diorite. According to the apparent resistivity pseudoplane map, resultant inversion profile and related geological data, eight fault tectonic belts and two tectonic alteration belts were delineated, among which F1 and F5 tectonic fracture belts, with large extension length, had good deep ore-prospecting space and potential, and two favorable ore-forming areas were delineated in the depth.

The electromagnetic and human interference in the Tailong geothermal test area of Qianbei (northern Guizhou) platform uplift on the Yangtze metaplatform has restricted the exploration effect of the traditional electromagnetic method. Based on a comprehensive evaluation of interference sources and rock physical parameters obtained from the experimental zone, the authors carried out high precision deep wide-area electromagnetic detection experiments, conducted two-dimensional continuum source inversion, and obtained underground stratigraphic resistivity distribution regularity and characteristics at the depth of 5 km, with lower Ordovician Meitan Formation, lower Cambrian Jindingshan Formation,, Mingxinsi Formation and Niutitang Formation as the low resistance cover layers of the experimental zone, the lower Ordovician Huayuan Formation, Tongzi Formation, Cambrian Loushanguan Formation, Shilengshui Formation, Gaotai Formation and Qingxudong Formation, and Sinian Dengying Formation as the high resistance layers for heat storage. The influence of the deep fracture structure on the heat storage layer was also revealed. The electrical layer revealed by the wide-area electromagnetic method is consistent with the information revealed by the drilling SZK1, and the results show that the wide-area electromagnetic method is an effective detection method in the strong geothermal interference zone of Qianbei platform uplift on the Yangtze paraplatform. The results obtained by the authors enrich the geothermal energy research results in northern Guizhou and provide geophysical parameters for further promotion of geothermal exploration in northern Guizhou.

However, the prospect of oil resources exploration and development in Xinjiang is far beyond these achievements, and there are still large-scale reserves lying underground. The piedmont area at the south edge of Junggar Basin is one of the key areas. However, the exploration in this area is very difficult; especially in the piedmont area on the southern margin of Junggar Basin, the gravel layer is widely distributed and deeply buried, and the buried depth of some sections is even more than 1km, which brings great challenges to seismic exploration and other exploration methods. This paper analyzes the application effect of the wide field electromagnetic method in the piedmont area on the south margin of Junggar Basin, expounds the application effect of the electromagnetic method in the exploration of shallow gravel layer and deep concealed structure, and indicates that the electromagnetic method has great potential in oil exploration.

Petrographic and geochemical study and U-Pb dating of uranium-rich granite bodies in Lincang area were carried out for Shuangjiang 701 and Fengqing 901 uranium mines, with the purpose of exploring the relationship between petrogenesis type, diagenetic tectonic background and uranium mineralization. The results show that Lincang uranium-rich granite body has high Si (up to 90.11%, averaging 71.6%), rich alkali, high potassium and high Ca, thus belonging to high Al and high potassium calcium alkaline series rocks. U-Pb zircon dating yielded 214±12 Ma, and thus Lincang uranium-rich granite body was formed in Late Indochina. Rare earth elements show a slightly rightward "V" shape, with obvious fractionation of light and heavy rare earth elements (w(LREE)/w(HREE) 7.26 on average), obvious negative Eu anomaly (δEu=0.28 ~ 0.49), relative enrichment of Rb, U and Th, and relative loss of Ba, Nb, Sr, Ti and Eu. Comprehensive analysis shows that Lincang uranium-rich granite belongs to S-type granite with obvious differentiation, which must have originated from melting of upper crust material and was formed in a mountain-building and rift environment in late collision, belonging to the simultaneous collision of granite related to the Lancang River collision zone. Its high content of uranium provided part of the uranium source for the uranium mineralization process. Uranium elements were transported to the vicinity of the fault fracture zone and was enriched to form granite-type uranium deposits by leaching.

The Xihuang vanadium deposit is located in the black rock series of the lower Cambrian Shuigoukou Formation in southern Qinling Mountain. The orebody is large, and the ore-bearing horizon and grade are relatively stable. The ore types are mainly carbonaceous mudstone and siliceous mudstone. The analysis of petro-geochemical elements and REE indicates that the vanadium deposit was formed in the hypoxic reductive environment from the continental margin to the deep sea, and the rock material source came from sea water, hydrothermal jet and terrigenous debris, with the biological activity playing an important role in the aggregation and precipitation of the vanadium deposit. Based on the comprehensive geological and geochemical characteristics, it is concluded that the vanadium deposit belongs to the biogenesis of hot water deposition, and that the vanadium deposit should be of biological and hydrothermal sedimentary origin.

Yanyuan basin is a Cenozoic sedimentary basin in southwest Sichuan basin, where Baishan Formation strata and Yantang Formation strata have rich rock salt. There are four drill holes and a producing well in the salt range of Yanjinggou area, and although the drilling depth of Pu-3 well is 1 001 meters, it does not intersect the salt deposit. The latest 1:50 000 gravimetric data were employed and processed in this paper to build geological-geophysical model of rock-salt minerals by integrating the physical characteristics with gravity anomaly features of rock salt deposit, and a gravimetric profile was simulated by performing the 2.5D forward modelling calculation to infer the geometric and physical parameters of the geological bodies that result in local anomalies. Based on the interpretation of gravity anomalies and the geological understanding of Yanyuan basin, the authors predicted two prospective zones for rock salt exploration in the study area, which has great prospecting significance in Yanyuan basin.

The Tudiling large-sized Ta-Nb deposit was recently discovered in the South Qinling orogenic belt by the Hubei Geological Survey Institute. This paper introduces the methods used during the exploration process, and proposes a comprehensive prospecting method suitable for volcanic type "rare" deposits, that is, to find the target area by 1:50,000 stream sediment survey, to delineate the mineralized zone by large-scale rock profiling, to identify the ore-bearing geological bodies by mapping of volcanic lithofacies and rock combination characteristics, to constrain the surface orebodies by trenching engineering, and to verify the deep orebodies by drilling. Practice has proved that the combination of prospecting methods is economical, fast, and effective. Based on the analysis of various prospecting methods, a prospecting model is established, which is of great significance for prospecting of volcanic Ta-Nb deposits in China.

Based on the 2D seismic interpretation in the Hanggin Banner area of northern Ordos Basin,the authors found a rift sequence under Paleozoic strata.On the basis of previous studies and combined analysis of well,seismic data,outcrop and geochemical data in Hanggin Banner area,the stratigraphic framework,possible geological epochs,sedimentary features and petroleum geological conditions of the rift were analyzed.This paper provides new ideas for the exploration of oil and gas in Hanggin Banner area.The Proterozoic strata in the study area is controlled by the SN-trending normal faults of Tamuhan and Dalao,where two half graben fault depressions were formed in western and central part of the study area respectively.The fault depression layers overlie Archean strata and underlie Paleozoic strata in angular unconformities.According to the unmetamorphic terrigenous clastic rocks and tectonic sequence features,it is inferred that fault depression layers should be the middle Proterozonic Changcheng Formation.Drilling and seismic data reveal that the fault depression layer contains fan-delta coarse sandstone and fine conglomerate intercalated locally with neritic mudstones.Depression layer is widely distributed and contains fan-delta sandstone,fine conglomerate and tidal flat brown mudstone.The sandstone within fault depression layers contains coal genetic gas originating from Upper Paleozoic strata.

State information acquisition is an indispensable part for MCSEM(marine controllable source electromagnetic) transmitter system which is important for MCSEM exploration. Especially under the conditions of high voltage, high temperature and strong interference, it plays an inestimable role in the reliable and stable operation of the instrument. Based on the principles of simplicity, ease of use, reliability and high safety factor, the state acquisition technology for the new generation of MCSEM transmitter system is designed and implemented by using the technology of CAN bus, serial port, optical fiber and wireless network. Test shows that the technical scheme of state acquisition is simple, stable and reliable.It has meet the harsh requirements of MCSEM transmitter system and has been applied to the exploration of nature gas hydrate in South China Sea.

The density interface inversion method has been playing an important role in the oil and gas exploration, regional structure inference studies as well as crustal crystal basement surface and Moho undulations researches. Most of the density interface inversion methods are generally based on the Cartesian coordinate system. When large regional or even global scale data are dealt with, the influence of earth curvature cannot be ignored, and the density interface inversion method based on Tesseroid model of spherical coordinate system needs to be considered. However, due to the limitations of calculation accuracy and efficiency, the existing density interface inversion method based on Tesseroid cannot be well applicable to the surface gravity observation data. In this paper, on the basis of previous studies, a density interface inversion method of spherical coordinate system suitable for surface observation data is proposed. Firstly, the gravity Gauss-Legendre integral formula in the spherical coordinate system is simplified to improve the forward calculation efficiency. Then, an optimized adaptive subdivision algorithm is introduced to enhance the calculation accuracy. According to the previous forward calculation and by using Cordell iterative optimization algorithm, the authors propose a density interface inversion method for the surface observation data in the spherical coordinate system. The proposed inversion method in this paper can be verified through the synthetic data test. The inversion results show that the proposed method can overcome the limitation of calculating precision and efficiency of the surface observation data. In addition, the inversion results based on spherical coordinate system are better than those based on cartesian coordinate system. Finally, tests on real data from South China mainland verify the feasibility of the presented methods. The results show that Moho depth rises gradually from the west to the east, with the western part uplifting dramatically and the eastern part uplifting gently. Between Wuling Mountain and Guizhou-Guangxi border, there is an obvious NNE-Moho step.

The fixed-wing frequency-domain airborne electromagnetic method has the characteristics of a high efficiency and a high spatial resolution. In the past, The three-frequency airborne electromagnetic data have gained many good results in China. Nevertheless, they are mainly plane qualitative interpretation results, with few quantitative inversion calculations performed, which limits the improvement of interpretation level. In this paper, fast approximate inversion, one-dimensional inversion and two-dimensional inversion are introduced into the interpretation of the field data of the key AFEM anomalies in Erenhot-East Ujimqin Banner area, and the application effects of the three methods are compared with each other. Fast approximate inversion is based on the calculation of apparent resistivity. Brent method is used for the one-dimensional inversion. Occam inversion is used for the two-dimensional inversion, and Rodi method is used to solve Jacobian matrix. The results show that fast approximate inversion can quickly and effectively provide a large quantity of underground electrical distribution information, one-dimensional inversion can provide the stable inversion results with a certain depth, and two-dimensional inversion has an advantage of obvious horizontal and vertical resolution.

When the tunnel passes through the complex strata with bad geological development, it often encounters geological disasters such as water inrush, mud inrush, collapse and roof fall. During the construction of the tunnel, the advanced geological prediction for the adverse geological disasters such as water and mud inrush has become an important issue to ensure the construction safety. Transient electromagnetic method has been widely used in the prediction of tunnel and underground cavern construction period. However, with the increasingly complex construction environment, the application of traditional TEM is restricted by various factors. For example, in TBM construction tunnel, the traditional transient electromagnetic device form is limited by TBM machinery, and the metal components of TBM produce strong electromagnetic interference to the collection of secondary field attenuation voltage, which makes this kind of method difficult to apply to TBM construction tunnel at present. In order to overcome the difficulties encountered by TEM in TBM tunnel construction, the authors, based on previous work, attempted to put forward a type of TEM advanced detection device based on electrical source excitation and electric field component acquisition. According to the different working conditions of drilling and blasting method and TBM construction tunnel, the three-dimensional finite-difference time-domain method is used to simulate the distribution and response characteristics of transient electromagnetic field in front of the tunnel excited by a single electrical source. Based on the analysis of the distribution and response characteristics of transient electromagnetic field, the authors hold that the single electrical source launching device not only can be used in the tunnel construction by drilling and blasting but also has the capability of advanced prediction in the tunnel construction by TBM.

The content of coalbed methane is an important parameter in evaluating coalbed reservoir. In this paper, the gray system was applied to the coalbed logging curve, the improved slope correlation method was used to analyze the logging curve series which are sensitive to the coalbed gas content. The gray multivariate static model GM (0,N) was used to predict the coalbed methane content in the sequence of positive correlation logging curves. Taking Qinshui Coal Field as an example, the authors compared the gray multivariate static model prediction results with the results of the multiple regression model analysis, and studied and analyzed the practicability of the gray multivariate static model. The results show that the improved association analysis of gray incidence can fully develop the relationship between logging curve and coalbed methane content, and that the GM(0,N) prediction model is more accurate and more robust than the multiple regression model in that it can effectively predict the coalbed methane content curve when the sample data is relatively small. The result is reliable and has practical application value.

Based on the curvature attribute,this paper proposes for the first time a set of processes for predicting "fracture zones-fracture development direction-fracture initiation".Firstly,the curvature calculation of the seismic data is carried out to predict the developing area of the fractured reservoir;then,the rose diagrams of the curvature data are calculated and compared with the rose diagrams from the log data to determine the direction of fracture;two dominant directions of fracture development are selected according to the directions of fracture development,and then the intensity properties of the two dominant directions of the curvature volume are calculated according to the main directions of fracture development;finally,the two azimuth intensity attributes are intersected with productivity respectively,and the one with the better correlation is the opening azimuth of the fractures.The above method was applied to K oilfield in Kazakh.The authors made the prediction that the fracture-vug reservoir is mainly developed in the eastern part of K oilfield,while the fracture reservoir is mainly developed in the western part,and that there are mainly two groups of fractures developed in the NW and the NW direction,of which the opening property of the NE trend fractures is good in the north part,while the opening property of the NW trend fractures is good in the south part.According to the prediction results,commercial oil flow was detected in the two proposed wells.

The Ordovician carbonate reservoirs in Yangshuiwu buried hill are widely distributed,and fractured porous reservoirs are well developed. But due to its deep reservoir,low resolution of seismic data, and unclear acoustic logging characteristics of reservoirs,it is difficult to achieve effective reservoir distribution prediction by conventional acoustic inversion.Based on the analysis of logging response characteristics of drilled reservoirs,the resistivity curves sensitive to effective reservoir response are selected and reconstructed with acoustic curves.The resistivity pseudo-acoustic curves with acoustic background are obtained.Then,the distribution prediction of effective reservoirs is realized based on post-stack logging constrained model inversion technology.Finally,the inversion of reservoir parameters based on neural network simulation technology is carried out by using the porosity curve and the pseudo-acoustic impedance curve drilled to realize the prediction of the planar distribution of porosity in this study area.Practice has proved that the forecasting method is effective and practical,and has a good application effect in the buried hill area of Yangshuiwu.

The Minghuazhen Formation of the Y structure in Bohai Bay Basin is well developed,but the drilled wells confirm that the oil-bearing characteristics of reservoirs have big differences in this area.The high reliability of reservoir fluid detection results are of great significance in improving the success rate of lithologic traps in the lower Minghuazhen Formation of the structure and activating the whole structure.In order to study the oil-gas bearing feature of the target area,the authors used a series of post-stack oil-gas detection methods based on amplitude and frequency,but still failed to identify the reservoir fluid effectively and reliably.By changing the research idea and using pre-stack hydrocarbon detection technology and method comparison,it is found that,when the incident angle is less than 30 degrees,the fluid factor directly extracted from pre-stack angle gathers is more sensitive to shallow oil and gas in this area,which corresponds well to the well logging interpretation results.The application of this sensitive parameter to the prediction of reservoir oil-gas bearing feature has achieved good results.It has certain reference significance for pre-stack reservoir fluid prediction in similar areas.

The TFEM method has been widely applied to oil and gas exploration since it was introduced. Through comprehensive interpretation, the geological structure and hydrocarbon condition of subsurface can be well predicted using multi attribute information acquired from TFEM data. For the purpose of improving the accuracy and the reliability of prediction, the TFEM multi-attribute image fusion prediction technique has been developed, which uses "bright spot" from multi-attributes image fusion display based on RGB and HSL color model to indicate most potential oil and gas bearing area. This technique has been proved effective by application in several regions.

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.

The erosion of magmatic rock has a great destructive effect on coal seam and seriously affects the safety of coal mining.High-density three-dimensional seismic data have the advantages of wide band,wide azimuth and high-density sampling,and contains abundant structural and lithological information,which lays a foundation for the identification and prediction of magmatic rocks.A comprehensive comparison of logging curves shows that conventional logging curves has many shortcomings,for example,acoustic wave and density are less sensitive to magmatic rocks,and it is impossible for them to identify and accurately classify magmatic rocks.Logs such as resistivity and natural gamma are sensitive to magmatic rocks,and can be used to classify magmatic strata.The acoustic wave and density curves are reconstructed based on the horizon division results of the sensitive curve,and then curves sensitive to magmatic rocks are obtained.Based on the seismic impedance inversion,the seismic information is transformed into lithological information,so the existing of magmatic rocks is clear and the erosion range and thickness can be predicted.

The bioavailability of cadmium (Cd) in soil is affected by many factors, while the morphological distribution characteristic is one of the important factors. In order to find out the bioavailability of Cd in paddy soil in western Zhejiang Province and analyze the relationship between the forms of Cd in soil and Cd content in rice grains, the authors collected and analyzed 32 samples of paddy soil and 15 samples of paddy rice. First, the morphological distribution characteristics and biological characteristics of Cd in soil under different pH and parent materials conditions were discussed. And then, by linear correlation analysis, the correlation between the Cd content in rice and different forms of Cd in soil was studied.The results show that Cd in paddy soil is mainly in the form of ion exchange (about 35% of the total amount), and the content of water soluble Cd is the least (about 1% of the total amount), with other forms of Cd in between. Under acidic condition (pH 5.0~6.5), both of the ion-exchange Cd and the bioavailability of Cd are the highest.The morphological distribution characteristics of Cd in soil between the weathered limestone and the other parent materials are quite different.Varying measures should be taken to control the Cd pollution in different parent material areas. The correlation analysis shows that there is a significant correlation between the Cd content of rice and the ion-exchange Cd content (P<0.01), but the correlation with other forms of Cd is not obvious.

Polycyclic aromatic hydrocarbons (PAHs) in a sediment core collected from eastern Beidagang Wetland were determined by GC/MS. The ∑PAHs concentration ranges from 18.1×10 ^-9 to 821×10^-9 in the whole sediment core. In the upper core, PAHs are mainly composed of 5~6 rings which are high molecular weight components, while in the middle and lower core PAHs are mainly composed of 2~3 rings of components. Since the 1950s, PAHs content in Beidagang Wetland has increased significantly. The peak appeared from mid 1950s to mid 1960s,earlier than that in most parts of China. PAHs content has been increasing again since the 1980s. According to composition and industrial development, the sources of PAHs in different periods were analyzed. Before the 1950s, PAHs mainly came from long-distance transportation and low-temperature combustion of wood. After 1950s, PAHs mainly came from incomplete combustion of fossil fuels around the wetland. PAHs pollution in Beidagang Wetland has been obviously affected by production activities since the 1950s, the main source of PAHs was incomplete combustion of fossil fuels, while the impact of exploitation leakage in Dagang Oilfield was not significant.

Selenium is a trace element that has an important impact on human health and hence has received increasing attention in recent years. There are many factors affecting the level of selenium in the soil, and the differences in different regions are obvious. In this paper, the content, distribution and main influencing factors of selenium in the soil of this area were studied in Gumi Town, Leibo County. The results show that the selenium content in the soil of the study area is not high, mainly concentrated around 0.226×10^-6. Selenium content in soil is positively correlated with organic matter, thiophilic heavy elements cadmium, mercury, lead, arsenic and zinc, but is not simply linearly correlated with pH value. In soils with different acidities and alkalinities as well as different land use patterns and parent materials, the two are significantly different. The selenium content in the soil in the survey area is mainly controlled by the parent material of the soil. The Silurian and Ordovician black shale and carbonate area in the old strata are more likely to be enriched with selenium, while the selenium content in the Triassic sandstone area in the newer strata is lower.