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    24 October 2012, Volume 26 Issue 6
    Deep Earth and Ocean Exloration
    Subducting Characteristic of the Pacific Slab Beneath Northeast China
    JIANG Guo-Meng, ZHANG Gui-Bin, XU Yao
    2012, 26(6):  1125-1135. 
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     The volcanoes locating in northeast China are very active. Some researchers consider that the origin of volcanoes is closely related to the subducting western Pacific plate and the upwelling asthenosphere. The thickness and the existing range of the subducted plate are not clear as far although the seismic tomography results obviously show that the Pacific plate exists below the volcano region. Therefore, in this study, we adopted the method combining the teleseismic tomography with travel time forward modeling to further study the velocity structure beneath northeast China, especially the precise model of subducted Pacific plate. Our results show that (1) the average thickness and velocity perturbation of slab are 85 km and 1%, respectively, and the slab has not been thickened compared with the previous result of the Japan Sea; (2) the Pacific plate subducted into the mantle transition zone with a shallow dip angle, and changed horizontally when it touched the bottom of mantle transition zone, and extended westward to Longitude 127°E and then stops over there; (3) the horizontal slab locates right below the volcano region. These above features help people understand the origin of intraplate volcanoes and the geodynamical process better.

    Analysis of Characteristics of Receiver Functions in Oahu Island of Hawaii Area
    LI Shen-Fu, LI Gong-Yi, SUN San-Jian, ZHOU Ming, TAN Jing
    2012, 26(6):  1136-1145. 
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    Receiver function method, which is often used to obtain the information from the subsurface in the crust and mantle of the Earth, is a very useful geophysical prospecting tool. Data from one station KIP deployed in Hawaii area were processed by using the P-wave receiver function technique. We analyzed the characteristics of radial and tangential receiver functions, and committed the time-depth conversion for the radial receiver function to obtain the information from 410 km discontinuity. Results show that there is obvious laterally heterogeneity in southwest and northwest of station KIP, and the 410 km discontinuity becomes shallower with the depth of about 390 km which may be the response of a hot melt matter beneath the KIP station.

    Fracture Characterization Using Image Logging in Borehole 3 of Wenchuan Earthquake Fault Zone Scientific Drilling (WFSD-3)
    JU Chang-Chun, LIU Dong-Meng, NIE Cuan, XIANG Biao, NIU Yi-Xiong, KONG An-Qing
    2012, 26(6):  1146-1153. 
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    The borehole of WFSD-3 is a main hole of the Wenchuan Earthquake Fault Zone Scientific Drilling. The continuous coring(total length of 1,548.44 m) and logging data of borehole  WFSD-3 have been acquired. The image logging data of borehole WFSD-3 contain a mass of in-situ geological feature information, which plays an important role in the identification of fractures, fracture zones and in the analysis of tectonic stress field. Using the resistivity and acoustic image logging data in conjunction with core data, the identification and analysis of fracture characterization were carried out. The results show that in the strata of borehole WFSD-3, high-angle oblique crossing fractures develop dominantly, followed by low-angle oblique crossing fractures. Vertical and horizontal fractures are rare. The fractures particularly develop at intervals of 25 m to 200 m and 900 m to 1,000 m in borehole WFSD-3. The main dip directions of fractures at different depths are obviously different: (1) above 410 m the main dip directions of fractures are between 260° and 290°; (2) from 410 m to 730 m, the main dip directions are between 330° and 360°; (3) from 730 m to 960 m, the main dip directions are between 210° and 240°; (4) from 960 m to 1,185 m, the main dip directions are basically consistent with those above 410 m;(5) from 1,410 m to 1,450 m, the fractures are different from those of the depths above with the main dip directions between 180° and 200°. Fractures are closely related to fracture zones and beddings, and the macro distribution of fractures is controlled by tectonics.

    Characteristics of Gravity Anomalies in the South China Sea and Their Tectonic Implications
    LI Chu-Ling, MENG Xiao-Gong, GUO Liang-Hui, TAO Chang-Li
    2012, 26(6):  1154-1161. 
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    Gravity anomalies can be used to infer the deep crustal structure in the South China Sea (SCS) where seismic data are limited to some specific points or profiles. This paper presents a comprehensive study of crustal structure by using gravity inversion for interface with seismic data constraints to invert depth of the Moho and to calculate crustal thickness, and by performing gravity anomalies correlative imaging method without constraints to construct the 3D subsurface distribution of equivalent density in the South China Sea. We also focus on the regional linear features of gravity anomalies and jointly use the continuation, horizontal gradient and linear feature enhancement filter to highlight the linear tectonics which always involve the density changes in horizontal, such as major deep faults, boundary of continental oceanic crust, spreading axes of oceanic basin. The integrated geophysical analysis along the Guangzhou-Palawan geosciences transect demonstrates that the characteristics of the gravity anomalies and their inversion results allow us to reveal crustal structure and regional tectonics features in the large scale of the South China Sea.

    Multi-scale Analysis of Gravity Anomaly and Discussion of Deep Structure in the North Margin of South China Sea
    WU Yue, MENG Xiao-Gong, LIU Guo-Feng
    2012, 26(6):  1162-1167. 
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    The gravity field contains the superimposition effect of heterogeneous bodies with different densities. In order to better analysis the information of the underground source reflected by gravity abnormity and the structure of the north marginal basins in South China Sea, this paper adopted the method of the two dimensional wavelet decomposition technique. Through resolving the gravity abnormity in the north marginal basins in South China Sea, and combining the topography and geomorphology of the study area, this paper discussed the basin structure and the geological characteristics of rock mass distribution. The results show that the fourth order transform approximation is mainly composed of the information of Moho undulations, and the wavelet transform details is mainly composed of the information of sedimentary base undulations. It is a better way to use wavelet multi-scale method to analysis the gravity anomaly.

    Upper Limit Variation of the Earth's Oblateness in Geological Epoch andImpact Analysis on the Dai Wensai's Nebular Hypothesis
    WANG Jun-Heng, ZHANG Yu-Ying, XIN Zhi-Xiang, LI Xin-Jun
    2012, 26(6):  1168-1174. 
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    In this paper, we present the variation of the Earth's oblateness in geological epoch and study the factors which affect this variation. The variation of the Earths oblateness can be used to understand the variation of the Earth's shape. A relationship among the oblateness, the average radius, the mass and the angular velocity of the Earth can be established or studied from Earth's oblateness formula which is derived from the special function of gravity potential theory. The oblateness and the maximum limitation of the oblateness in a geological epoch can be estimated from the average radius, the mass and the angular velocity of the Earth in the geological epoch. The variation of the oblateness in the geological epoch can be also estimated from the variation of the average radius, the mass and the angular velocity. The real Earth's oblateness in various geological epochs should be less than the calculated maximum limitation of the Earth's oblateness. Our study shows that the Earth's oblateness has had a trend of decrease as a form of pulsatile line since the formation of the Earth. The factors affecting on the variation of the Earth's oblateness include the average radius, the mass and the rotation angular velocity of the Earth. After carefully studying and calculating, we find that since 500 million years after the formation of the Earth, the average radius has caused almost 3% of the decrease of Earth's oblateness; the change of the mass has caused less than 3 millionth of decrease of Earth's oblateness; the angular velocity, the main factor affecting on the oblateness, has contributed more than 97% of the total decrease to the decrease about 74% of the Earth's oblateness.

    Soild Minerals Exploration
    Research on Iterative Method Used in Reduction to the Pole of Magnetic Anomalies at Low Latitude
    TAO Chang-Li, LI Hong-Wei, ZHENG Yuan-Man, MENG Xiao-Gong, ZHANG Yu-Wen
    2012, 26(6):  1175-1184. 
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    This paper analyses the iterative method used in the RTP at the magnetic equator, focusing on the key factor in the iteration: the choice of mapping function of the raw data to the target data. This method is extended to other low latitude regions by changing the mapping function, and the condition of convergence at different magnetic latitudes is given. Applications to synthetic and field magnetic data sets show that the improved method is effective for both the other low latitude regions and the magnetic equator, and the efficiency of the iterative calculation is improved.

    Interpretation of Magnetotelluric Sparse Survey Lines Data and Dense 3D Grid Data
    LIN Chang-Hong, TAN Gan-Dong, TONG Ta
    2012, 26(6):  1185-1192. 
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    We inverted the synthetic sparse survey lines data and dense 3D grid data generated from the test models and the field single line data. From the comparison between the 3D inversion results of synthetic sparse survey lines data and the 3D inversion results of dense 3D grid data, it is found that the 3D inversion results of synthetic sparse survey lines data can recover the 3D target although the effect is not as good as the 3D inversion results of dense 3D grid data. The 3D inversion results of the field single line data well reflect the 3D information of the bedrock interface underground near the survey line. The 3D inversion results show that it is possible to interpret MT sparse survey lines data using 3D inversion method. From the analysis of 3D inversion results from the synthetic data, all the tensor elements are suggested to be used in 3D inversion to interpret the sparse survey lines data and two offdiagonal elements can be used in 3D inversion to interpret the dense 3D grid data, while the results are better when all the tensor elements are used.

    Study on the Differences Between Finite Difference Time Domain Method and Pseudo-spectral Time Domain Algorithm in Numerical Calculation of Electromagnetic Wave Fields
    LIN Shu-Hai, WANG Wei-Li
    2012, 26(6):  1193-1198. 
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    In order to improve the resolution of numerical calculation of electromagnetic wave fields, the differences between finite difference time domain (FDTD) method and psedo-spactral time domain (PSTD) algorithm were studied. The FDTD method is a common numerical calculation method of electromagnetic wave fields, and it is widely applied to the solution of the partial derivative equations related to time.More memory is needed using FDTD method in large-scale numerical calculation. The PSTD algorithm is based on FDTD method and employs fast Fourier transform (FFT) to calculate the spatial derivatives in Maxwell's equations. Due to accuracy by FFT, the calculation precision is improved and grid numbers needed is decreased greatly by using PSTD algorithm. The PSTD algorithm has the advantage of saving computational memory space and is suitable for large-scale numerical calculation of forward modeling and inversion.

    Research on Finite-difference Numerical Simulation for 3D Borehole-to-ground Resistivity Survey
    GU Zheng-Yuan, ZHANG Gang
    2012, 26(6):  1199-1205. 
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    Borehole-to-ground resistivity survey is a geophysical method by which an electric current is injected from the borehole, and is received on the ground with different kinds of power supplied. Usually, in the field through the boreholetoground resistivity, the current source is divided into point current source injected from the bare hole and the linear current source injected from the cased borehole. Based on the practical work in the field, this paper studies the following aspects and obtains the corresponding conclusions: (1) when the current source is point current, the results of  three forward models (the current source above, inside and under the anomalous body), show that the apparent resistivity response on the surface varies greatly; (2) when the current source is a vertical line source, the results of three forward models (current source in the upper part of the anomalous body, extending to the middle of the anomalous body, as well as throughout the anomalous body), show that the apparent resistivity response amplitude changes gradually on the surface; (3) when the current source is inclined line source, the tilt angle of the line source has great effect on the apparent resistivity response on the surface, and the larger of the angle of inclination of the line source is, the smaller magnitude of the surface response is. These conclusions provide a guidance for field work by setting parameters of the apparatus in order to improve the accuracy of their observations, and make a qualitative analysis for the preliminary judging the depth of the anomalous body, and lay a solid foundation for the three dimensional inversion of the borehole-to-ground resistivity as well.

    Research on the Method of Improving Accuracy for Calculating Manual Potential in Direct Current Prospecting
    ZHANG Gang, Gu-Zheng-Yuan
    2012, 26(6):  1206-1211. 
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    Direct current prospecting is a main method of electrical exploration in which the electric current is injected from the ground or in the borehole, and potential is received on the ground. Distribution of the underground physical properties are analyzed by processing the abnormal potential measured on the ground, and the spatial location of the underground ore body is deduced. This paper mainly study the method for calculating the manual potential from the observation electric potential measured by the square wave power supply. The results show that, when the collecting potential data are high quality data, there is little change in artificial potential calculated by using different lengths of window widths; while the collecting potential data is low level quality data, there is great change in artificial potential calculated by using different lengths of window widths; assuming that there is a group of theory potential data adding different proportions of random noise, using the different window widths for theoretical calculations of artificial potential, we can get accurately artificial potential by taking a short window width. These conclusions lay the groundwork for the next step of the data processing and interpretation.

    GST Time frequency Filter Application in MT Data Processing
    CHEN Hai-Yan, JING Jian-En, WEI Wen-Bo
    2012, 26(6):  1212-1217. 
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    Short-time Fourier transform is founded on the base of stationary signal analysis and can provide information in frequency domain with a bad ability of signal analysis in time domain. S transform is one of methods of signal analysis in time frequency domain, which is better than short-time Fourier transform, and can provide information of signal in time frequency domain. By using S transform to analyze Magnetotelluric(MT) sounding data in time frequency domain, it is helpful to filter noise in MT data and to improve the quality of MT data spectrum. This paper studied the method of time frequency domain filtering for suppressing noise in magnetotelluric sounding data by the generalized S transformation. Time frequency characteristics of noises of all kinds of wave and theirs influence are analyzed. According to the MT data processing characteristics and GST spectrum, time frequency filter and filter method are studied, which is suitable for suppressing the MT noises. Through actual MT data processing, the quality of impedance tensor estimate is improved and validity of the proposed method is verified.

    Application of Seismic First Arrival Tomographic Inversion on the Exploration of Polymetallic Mine
    LI Jian-Guo, DIAO Bin, SUN Shao-Wei, ZHOU Xin-Feng, SUN Yuan, SONG Li-Fang, HUANG Qin, XIANG Biao, XIAO Hun
    2012, 26(6):  1218-1224. 
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     Since the particularity of the ore rock structure and lithology in multi-metal mining area, it's difficult for seismic reflection to form a continuous and stable and gentle reflecting interface, and the application of seismic reflection method are generally not effective.This paper established a initial velocity model by using the first break information which was received by means of the ground long arrangement, then utilized the first arrival ray tracing forward modelling and SIRT velocity tomographic inversion technique in the complex surface and medium conditions, which did not rely on the existence of the bed interface, to obtain the velocity field information about the structure and lithology changes of ore bodies or rock bodies, and then the distribution range and exhibition characteristics of the detection target were acquired.The testing results show that the method is feasible, and anomalous changes of the velocity inversion coincide with the results of geological survey. Since the detecting depth of this method can reach hundreds of meters, it could provide a reliable basis for the detection of shallow insidious ore bodies and structures.

    Design a Software for 3D Automatic Gravity and Magnetic Inversion
    ZHENG Yuan-Man, TAO Chang-Li, ZHANG Chen
    2012, 26(6):  1225-1230. 
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    The current software system of 3D automatic gravity and magnetic inversion has an inefficient work mode because of extremely time-consuming inversion calculation. This paper presents a new work mode in order to improve the work efficiency and the inversion result. A software system of 3D automatic gravity and magnetic inversion with real-time visualization was designed and developed. This system can real-timely visualize intermediate inversion result during the inversion process so that intermediate inversion results can be evaluated and then inversion parameters can be adjusted promptly based on evaluation of the intermediate inversion results. With this new work mode, the inversion process can be intervened and be led to a good inversion result in an efficient way. This paper presents the analysis and design work of this software system. Also, some key development techniques and design solution are presented.

    Energy Exploration
    Extrapolating the OBS Data Using the Kirchhoff Integral Method
    WANG Xiang-Chun, WANG Yan-Feng, JIA Chang-Liang, LIU Hua-Wei
    2012, 26(6):  1231-1236. 
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     When the OBS (ocean bottom seismograph) technique is used to explore the Earth, the shots are on the sea surface and the receivers are on the sea floor, so the OBS data can't be processed in the conventional seismic data processing method. In order to solve this problem, the shots and OBS need  correcting into the same surface. Here the Kirchhoff integration method is carried out to extrapolate the shots onto the sea bottom surface where the OBS lies on and ideal results are achieved. The Kirchhoff extrapolation processing used here causes little negative influence on the resolution and wave field's signal/noise ratio. In addition, more accurate velocity field is achieved by velocity analysis to the extrapolated data than to the static shift corrected data, and this is very important to the consecutive data processing such as NMO (normal moveout), stack and so on.

    Multiple Suppression Strategies on Land Seismic Data
    YU Yi-Jun, ZHANG Dui-Feng
    2012, 26(6):  1237-1243. 
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    In land seismic survey, multiple reflections, like other interference waves, interfere with primary reflections and reduce the signal to noise ratio of seismic data. According to the property of multiples in the land based seismic data, a processing strategy which combines stacking and the f-k filtering for multiple attenuation was proposed. Firstly, stacking with velocity functions from the primaries partially to attenuate the energy of multiples in the original seismic data, and determining the CMP ranges with residual multiples by stacked sections, and then the f-k filtering was applied to the CMP gathers with residual multiples along the profile for suppressing multiples. The results of synthetic and field seismic data processing show that the strategy is not only effective for multiple attenuation in this land seismic data, but also reduces the injury for the primary reflections during data processing.

    Amplitude Preserving Method in τ-p Domain for Offshore Seismic Data
    SUN Lu-Beng, SHOU Hao, ZHANG Yu-Hua, CAO Zi-Jiang
    2012, 26(6):  1244-1249. 
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    AVO analysis and the inversion need to preserve amplitude relative relations when processing seismic data. In conventional processing methods,spreading compensation,stretch distortion and multiple ware can change the relation of amplitude. All above questions are serious, especially for offshore seismic data. This article proposed a new method based on processing data in τ-p domain, with do not need spherical spreading compensation, and can improve can correlation of multiple ware, reduce spherical spreading compensation and multiple wave to distort amplitude relative relations, and easily to carry on amplitude stretch correction with robust stretch correction factor, reduce distortion of the frequency and energy which caused by NMO, proposed seismic amplitude preserving processing method for offshore seismic data. Finally actual material processing has confirmed the method rationality and the feasibility through Norwegian offshore seismic data.

    Seismic Response Characteristic Analysis of Oil-rich Reservoirs
    TU Zhen, WANG Pan-Chun, HE Jing, ZHANG Feng-Qi, WANG Da-Quan
    2012, 26(6):  1250-1257. 
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     The seismic response characteristics of oil layer and water layer are close, and conventional fluid prediction methods cannot get satisfactory result for oil layer prediction.Through integrated study of well logging, geology and geophysics, and statistical analysis of theoretical model and field data, the seismic response characteristic of oil-rich reservoir was analyzed from the point of the relative variations of amplitude and sweetness, and its regularity was summarized quantitatively.The results show that when the thickness of oil layer is small, the relative variations of amplitude and sweetness are small too, and they have no obvious relationship with the thickness of oil layer.With the thickness of oil layer increasing, the relative variation of amplitude increases linearly, and that of sweetness increases exponentially with higher rate.Sweetness can amplify the difference between oil layer and water layer

    Fractures and Solution Pore Prediction in Carbonate Reservoirs Based on Geostatistics Inversion
    SUN Wei, WANG Pan-Chun, LI Yu-Feng, WANG Da-Quan, XU Wei, HAN Lei
    2012, 26(6):  1258-1264. 
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    Fractures and solution pores can greatly improve the physical properties of carbonate reservoirs, therefore, the key factor of reservoir prediction is how to predict the distribution of the fractures and solution pores with geophysical methods. This article proposed a method of fracture and solution pore prediction in carbonate reservoirs based on geostatistics inversion. Firstly, according to the mineral composition of carbonate rocks, the fracture porosity and secondary porosity were calculated with resistivity curves and three porosity curves. With the calculated result, geostatistics inversion was carried out to predict the distribution of the fracture and solution pore. According to the comprehensive analysis of inversion result, the developed area of fractures and solution pores was  obtained. This method was applied to the fracture and solution pore prediction in the study area. The predicted distribution characteristics of fractures and solution pores agreed well with the distribution of dolomite, and the veracity of this method was verified.

    Well-logging Evaluation Methods on Carbonate Reservoirs
    XU Jing-Ling, WANG E-Jing, CAO Guang-Wei, QIN Yu-Xing
    2012, 26(6):  1265-1274. 
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    The logging evaluation methods and techniques on domestic and foreign carbonate reservoir were researched from the four aspects of reservoir type classification, parameter characterization, fluid property discrimination and mathematical method. After the analysis and comparison of various evaluation methods, it is considered that according to certain mathematical algorithms, not only the reservoir types were identified very well, but also the reservoir parameters were evaluated semi-quantitatively and quantitatively by the use of the conventional logging and imaging logging. The physical parameters of fracture cave reservoir were calculated using the data of conventional logging and new logging technologies (electrical logging and sonic logging), and on this basis, the fluid property can be discriminated by the conventional logging, nuclear magnetic resonance and dipole shear sonic logging. By comparison with the results of core analysis, this method for calculating reservoir parameters is not only effectiveness, but also simple and feasible. The mathematical method and the new logging technique data are very important for the complex carbonate reservoir evaluation, and can solve the calculation and evaluation problems of complex carbonate reservoir. Using reservoir characteristics of carbonate rocks and fluid properties as the starting point, with combination of geological, seismic and logging data, and mathematical algorithms, the reservoir types and fluid properties were accurately identified and determined, thus the physical parameters of fracture cave reservoirs (carbonate reservoirs) were accurately calculated, which were the focus and direction of logging evaluation on carbonate reservoirs.

    Coalbed Methane Reservoir Evaluation from Wireline Logs in TS District, Southern Qinshui Basin
    HUANG Zhao-Hui, JU Chang-Chun, YANG Yu-Qing, ZHANG Guo-Hua, WANG Wen-Wen
    2012, 26(6):  1275-1282. 
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    Coalbed methane (CBM) is an unconventional natural gas which is generated and stored in coalbeds.Unlike conventional natural gas, the parameters of proximate analysis components, matrix porosity, fractural permeability and gas content and so on, should be paid more attention in the evaluation of coalbed methane reservoir. In this paper, geophysical logging data are used to evaluate the parameters of coalbed methane reservoir in the TS District of Southern Qinshui Basin. First the responses were analyzed from the geophysical logging data, and then the proximate analysis components of coal were calculated by regression analytical method and its application condition was studied.Considering the variety and complexity of the factors of CBM content, the Langmuir rank equation method, which is based on the isotherm adsorption equation, was introduced to estimate the CBM gas content through combining the analysis results of the correlation region coal samples.By analyzing the dual porosity characters of coalbeds, the total porosity can be calculated by density porosity formula of variable matrix density, while using the dual lateral logging data, the fracture porosity can be calculated by iteration approximation method.At last, according to the well developed face cleat but the little developed butt cleat in the coalbeds, the fractural permeability of CBM reservoir can be calculated by a simplified single group plate crack model. The calculation result of well TSA show that the proximate analysis components and CBM gas content are with high precision, meanwhile, the total porosity is about 55%, the fracture porosity is mostly less than 05%, and the fracture permeability is about 0.001×10-3 μm2 to 10×10-3 μm2.These poroperm characteristics matched well with the data of adjacent area.These means the certain parameters of CBM reservoir can be estimated accurately by geophysical logging data.

    6Using the BICGSTAB Algorithm with the Incomplete LU Factorization Precondictioning to Implement 2D FDFD Induction Logging Fast Forward Modeling
    XIONG Jie, JU Chang-Chun, MENG Xiao-Gong
    2012, 26(6):  1283-1288. 
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    The difference scheme of the 2D induction logging in cylindrical coordinates was derived, and the finite deference frequency domain method was employed to solve the induction logging forward modeling problem. Based on the fact that the coefficient matrix was a large sparse, complex and ill posed matrix and the linear system was difficult to solve, the bi-conjugate gradient stabilized (BICGSTAB) algorithm with incomplete LU factorization precondictioning was employed to solve this ill posed linear system. The results show that this algorithm has advantages of high performance, high precision and stability and can improve the performance and the precision of induction logging forward modeling.

    Strategies of Accelerating Reverse Time Migration Using Graphic Processing Unit
    LIU Ya-Ning, LIU Guo-Feng, ZHANG Zhi-Fu
    2012, 26(6):  1289-1293. 
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    Reverse-time migration is the most accurate seismic data prestack depth migration method, but the computing needs of its highintensity limit its largescale computing applications. The development of programmable Graphics Processing Unit(GPU) provides an alternative method for rapid calculation of the reverse-time migration. In this paper, we focus on the main steps using GPU to calculate the reverse time migration. We summarize the key points in GPU code optimization, and highlight two optimized components: one is the application of random boundary conditions. The data transmission between the host and GPU is reduced. The second is the application of shared memory to store the forward wave field. Compared to the global memory, data reading band widths increase greatly. Finally, we use the Marmousi data to test our code, and the results show that the reverse-time migration program running on GPU has been well optimized to improve the computational efficiency.

    Environmental Exploration
    Soil Radon Intercomparison Measurements and Some Important Issues
    WANG Na-Ping, XIAO Lei
    2012, 26(6):  1294-1299. 
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    In order to ensure the accuracy and reliability of the key parameters of soil radon measurement results of radon mapping methods, our laboratory has the first time as China's organization to participate Radon Intercomparison Measurements, held at three radon reference sites of Cetyně, Bohostice and Buk in the Czech Republic in 2010. For the level of significance α=1%, testing results (orientation tests based on the comparison with the group) show that our measurements of cA (radon activity concentration) are in good agreement with that of the group of organizations participating in the comparison measurement. The decisive test based on the comparison with the databases of radon reference sites reveals that our resultant means of radon data are in accord with those of all successful organizations (N=180) which measured at radon reference sites since the year 2000. The results indicate that our soil radon measurement techniques have reached the international first-class level. After the radon international comparison, we found some important problems in soil radon measurement in China, such as instrument calibration, soil gas sampling technology. We proposed that the method for soil radon investigation should be improved and its technical specification should be carried out.

    Mapping of Soil Radon Concentration in Zhongshan, Guangdong Province
    XIAO Lei, WANG Na-Ping, ZHOU Zhi-An, CHU Xing-Ming, CENG Li-Hui
    2012, 26(6):  1300-1305. 
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    In order to study the regional mapping method of radon concentration in soils, the survey work was performed in a total survey area of 1,800 km2 in Zhongshan, Guangdong Province. The electronic radon monitor RAD7 and the permeameter RADON JOK were used to measure radon222 concentration and gas permeability of soils, acquiring 67 valid data. The radon 222 concentrations of soils in Zhongshan vary between 0.74 kBq/m3 and 1,199.24 kBq/m3, and the average concentration is (100.41±154.64) kBq/m3. The gas permeability of the weathered granite soil is dominantly high and medium, and that of most Quaternary sediments is low. Based on these data, the radon risk of soils in the study area is accurately classified, and the result shows that the classification method of radon risk of soil based on the radon concentration and gas permeability is proved to be feasible.

    Appilance and Signal Processing
    Application of SoPC on Highprecision Geoelectric Data Acquisition System
    ZHANG Qi-Sheng, DENG Meng, YANG Kun-Feng, CHEN Kai, WANG Meng, SUN Zhi-Cheng
    2012, 26(6):  1306-1311. 
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    To get better and faster development, modern geophysics needs to draw upon the latest technologies to promote the acquisition precision of geophysical data.System on Programmable Chip (SoPC) is a flexible and efficient SoC solution based on FPGA, which provides a new way to develop novel high precision geoelectric data acquisition device.This paper introduces the application of SoPC technology to the research and design of an A/D conversion controller which complies with the time sequence of CS5372, a module conversing the serial data to parallel one, a resampling FIR digital filter using Matlab and DSP Builder, a NIOS II Soft IP Core integrated by Quartus Ⅱ and a PC software designed with LabVIEW.Under the application of equipments mentioned above, Cyclone chips which replace expensive CS5376 can be used to realize the acquisition of the high precision geoelectric data. As the result shown, the use of the technology of SoPC can greatly improve the cost performance of high precision geoelectric data acquisition devices and also can integrate the digital parts of geo-electric data acquisition devices into a chip, which also provide an effective way to solve problems under the complex geoelectric condition.

    Low Time Drift Technology for Marine CSEM Recorder
    CHEN Kai, DENG Meng, WU Zhong-Liang, JING Jian-En, LUO Xian-Hu, WANG Meng
    2012, 26(6):  1312-1316. 
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    According to the marine CSEM(controlled source electromagnetic method), many controlled source electromagnetic acquisition stations in the bottom of the sea need to observe weak electromagnetic signal synchronously and continuously for long term. To solve the problem that it can‘t receive GPS RF signal in submarine, the high stability OCXO combines with precision GPS clock as the hardware foundation. The low time drift technology is put forward through locking GPS before and after launched deployment, as well as time drift compensation. Many controlled source electromagnetic acquisition stations are realized synchronous observation. Indoor and sea trials indicated that the technology could reduce data synchronization error significantly.

    Design of Digital Multichannel Analyzer Based on FPGA
    CENG Wei-Hua, WEI Qiu-Ju
    2012, 26(6):  1317-1321. 
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    Digital multi-channel pulse height analysis becomes the mainstream of multi-channel analysis technology. A digital multi-channel analyzer (DMCA) based on a single FPGA chip is introduced. The nuclear signals are processed by EP3C40Q240. It uses digital signals acquired by ADC to do calculus, seek the peaks, discriminate the threshold, and then form the energy spectrum. DMCA communicates with the RS485 bus interface. The software on PC can control DMCA and display energy spectrum. And the energy spectrum of 137Cs is given, which is obtained from NaI( Tl) detector and processed by DMCA.

    Application of Embedded Linux Technology On the Power Supply of Telemetric Digital Seismic Instrument
    ZHANG Qi-Sheng, ZHANG Qi-Mao, GUO Jian, LUO Wei-Bing, SUN Zhi-Cheng
    2012, 26(6):  1322-1326. 
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    As the next generation of seismic prospecting instruments, the high precision telemetric digital seismic instrument plays an extremely important role in China's seismic prospecting and development of oil and gas resources. Embedded Linux technology is a high performance and low-power consumption embedded system solution based on embedded microprocessor, which provides a new way to develop novel telemetric digital seismic power supply. The paper presented the hardware system of a double layer stack based power supply constructed with PPC405 high performance embedded microprocessor and FPGA chips, transplanted U-Boot, embedded Linux kernel and JFFS2 file system core, and developed drivers and application programs related to power supply on the hardware framework, and achieved data transmission and network interactive function of telemetric digital seismic power supply.

    Research on Intelligent Power Management System for Engineering Seismic Instrument
    HAO Bin-Bin, DENG Meng, ZHANG Qi-Sheng, HUANG Jian-Yu, LE Heng
    2012, 26(6):  1327-1330. 
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    The paper presents a kind of intelligent power management system used in engineering seismograph, which has features such as wide input range, stable output, self protection, simple user interface and low power consumption etc. The design of hardware in the system consists of power supply circuit based on power module, circuit based on high speed SCM C8051F320 and 24-digits high precision ANALOG-TO-DIGITAL CONVERTER LTC2449,the LCD screen backlight power supply circuit. The design of software in the system consists of the C language program for SCM and VC user interface program based on Embed Windows XP. It eventually accomplishes a kind of intelligent power management system for engineering seismograph with stable power supplyment, real-time current detection and adjustment of screen back light.