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  • Table of Content
      10 August 2015, Volume 39 Issue 4 Previous Issue    Next Issue
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    Article
    Near-surface oil and gas geochemical characteristics and exploration prospect of the western depression of Taiwan Strait Basin
    ZHAO Jing, LIANG Qian-Yong, ZHANG Li, ZHONG Guang-Jian
    Geophysical and Geochemical Exploration. 2015, 39 (4): 657-664.   DOI: 10.11720/wtyht.2015.4.01
    Abstract   HTML   PDF (6135KB) ( 513 )

    Taiwan Strait Basin is commonly considered to be a good petroleum-bearing area. However, the former studies were all focused on the data from sedimentology and geophysical exploration, and no direct evidence from drilling or petroleum geochemistry can prove the existence of any economic oil or gas reservoirs in areas supposed to have good petroleum prospects. In this study, submarine near-surface geochemical exploration for oil and gas was conducted to reveal whether the hydrocarbon seepage is existent in these areas in the hope that it could further provide direct evidence for the existence of petroleum reservoirs at subsurface. The result indicates that the hydrocarbon seepage system do exist in this area, and the near-surface response of hydrocarbons in the sediments further indicate that the study area has a good petroleum prospect.

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    The application of multifractal theory to the decomposition of geochemical fields and the study of element association: A case study of Tongshanling-Xianglinpu area
    GONG Jing-Jing, LI Fang-Lin, ZHANG Shuang, CUI Fang
    Geophysical and Geochemical Exploration. 2015, 39 (4): 665-672.   DOI: 10.11720/wtyht.2015.4.02
    Abstract   HTML   PDF (14457KB) ( 490 )

    Located in southwest Hunan Province and at the center of Nanling metallogenic belt, the Tongshanling-Xianglinpu area, in which several W-Sn and Cu-polymetallic deposits have been found, has great potential for the prospecting. In this paper, the multifractal theory, i.e., the model of singularity, was applied to the decomposition of geochemical fields, on the basis of the data of 1:50 000 geochemical survey obtained in the study area. The representative elements Sn and Ag were analyzed in detail, with good results achieved: the singularity reduced the influence of the high background value of rock mass and the variety background levels and intensified the anomalies in low-value background zone; the fractal density reduced the influence of the data noise effectively, and the anomalies became more clear. This paper discussed the characteristics of element association preliminarily, and pointed out that it's better to make a comprehensive analysis in combination with the respective advantages of original data and singularity.

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    The application of continuous electromagnetic profiling method to the exploration of oil and gas: A case study of Ruoqiang sag in Altun forelands
    ZHAO Liang
    Geophysical and Geochemical Exploration. 2015, 39 (4): 673-677.   DOI: 10.11720/wtyht.2015.4.03
    Abstract   HTML   PDF (6182KB) ( 523 )

    The application of continuous electromagnetic profiling (CEMP) to Ruoqiang sag of the southern Altun Mountains is described in this paper. Because of the undulating landform, static electromagnetic effect is serious, and underground resistivity varies considerably. Robust processing applications, static correction and CEMP handling with terrain two-dimensional continuum inversion imaging can yield high inversion precision in line with the actual situation. Making full use of the complementary advantages of seismic and non-seismic survey, the author established the structural interpretation model so as to deepen the understanding of the geological structure. It is detected that the left twisting slip of the Altun fault system caused the formation of piedmont 3 groups of NEE-striking faults parallel to the Altun Mountains, and that the strike slip movement caused the piedmont depression to exhibit the concave and convex tectonic pattern of the Altun Mountains in Ruoqiang sag. It is inferred that the long distance overthrust nappe towards Ruoqiang Sag made the Proterozoic Paleozoic strata thrust onto the Mesozoic strata, and therefore Altun forelands possibly have covered Jurassic strata characterized by large thickness, great burial depth and relatively high maturity.

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    The method for shallow seismic exploration in Qiangtang basin
    LIU Jian-Xun, ZHANG Bao-Wei, WANG Xiao-Jiang, XU Ming-Cai
    Geophysical and Geochemical Exploration. 2015, 39 (4): 678-685.   DOI: 10.11720/wtyht.2015.4.04
    Abstract   HTML   PDF (5026KB) ( 630 )

    Due to complex seismic-geological conditions,it is very difficult to acquire high quality results of shallow seismic exploration in Qiangtang basin of Tibet. In this paper,through the experiment of shallow seismic exploration technology in this area,the authors discussed the interference of the permafrost layer to the seismic data.In seismic data acquisition,a smaller channel spacing should be adopted,with a number of long arrangements of multi-channel receiving mode.In addition,the number of CDP stacking is increased,and a large tonnage high frequency vibrator is utilized for high-frequency excitation.In this way,a higher quality of raw seismic data can be obtained.In seismic data processing stage,we can use the corresponding de-noising technology before CDP stacking,which can effectively suppress various interference waves,such as random noise and coherent noise.The acquisition method and processing technology of 2-D shallow seismic survey is tentatively summarized,and the experimental study has achieved good results.The results achieved by the authors have certain reference value for application and study of shallow seismic exploration technology in plateau permafrost area in the future.

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    The new technology and development trend of geochemical survey
    WANG Lei, HAN Run-Sheng, WANG Jia-Sheng
    Geophysical and Geochemical Exploration. 2015, 39 (4): 686-690.   DOI: 10.11720/wtyht.2015.4.05
    Abstract   HTML   PDF (617KB) ( 714 )

    In recent years, geochemical survey has seen a high-speed development not only at the technical level but also at the ideological level. The disturbances of organic material and eolian sands on anomalies over some special landscape areas have been solved. Deep-penetrating geochemical survey techniques such as electrogeochemical survey techniques, aerosol geochemical survey techniques, active metallic element geochemical survey techniques in search for concealed ore deposits have gradually matured in theory and application. Exploration technique of tectono-geochemistry has been one of key technology in the locating, predicting and evaluating of buried ore deposits, and has formed a complete technical process. Artificial neural network and other new methods for analysis of geochemical data have been steadily improved. The system of muti-purpose regional geochemical survey has been established, which helps concurrent development of resource survey and environmental survey. In the future, geochemical survey will get more and more applications in such fields as agriculture, land use and plan, environmental early warning and protection.

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    The preliminary application of the heat released halogen method to the prospecting for deep orebody in the Hucun copper-molybdenum deposit, Anhui Province
    ZHI Chao, XIANG Wu, ZENG Jian-Nian, ZHANG Yu-Cheng, BAI Liang
    Geophysical and Geochemical Exploration. 2015, 39 (4): 691-697.   DOI: 10.11720/wtyht.2015.4.06
    Abstract   HTML   PDF (12262KB) ( 339 )

    The heat released halogen method, a deep-penetrating geochemical method for ore exploration, has not been used extensively yet. The authors carried out the research on the feasibility this method in the Hucun copper deposit of Anhui Province characterized by moist hills and low mountain eluvial-slope wash covered geochemical landscape area. Based on a comparison of soil heat released halogen with the conventional soil survey, the authors have reached some conclusions: The heat released halogen method has more advantages than the conventional soil survey in that it can effectively eliminate the interference of rock body. The indicating significance of conventional soil halogen anomalies is limited and has no universality. The element anomalies of conventional soil survey are impacted by rock body or its contact zone and superficial mineralization, and hence their indicating significance has limitation; nevertheless, the barium negative anomaly area has a fairly good indicating significance for hydrothermal alteration zone. The heat released halogen anomalies correspond well with deep orebody space, the element content has similar change tendencies, and the heat released halogen anomalies appear on the surface of the vertical projection part of the orebody, which is consistent with previous conclusions. It is tentatively held that we can try to use the heat released halogen method at the deep orebody positioning stage in the Yangtze River hill and low mountain eluvial-slope wash covered geochemical landscape area.

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    Characteristics of geophysical and geochemical anomalies and prospecting criteria of the Beiling ore district,Guangdong Province
    SUN Ning, LUO Wei, WEI Long-Ming, KONG Fan-Qian, MIAO Yuan-Xing, TANG Pan-Ke
    Geophysical and Geochemical Exploration. 2015, 39 (4): 698-703.   DOI: 10.11720/wtyht.2015.4.07
    Abstract   HTML   PDF (5022KB) ( 664 )

    The preliminary study of the geophysical and geochemical characteristics of the Beiling ore district was based on the working results of 1:10 000 geophysical and geochemical anomaly survey. Factor analysis shows that the ore district is dominated by metallogenic elements Pb, Zn, with the ore-forming element combination of Ag, Pb, Zn, Bi and the superimposition of W, Mo, Cu and other elements. An analysis of the 1:10 000 IP data of ore-bearing rocks shows low resistivity and high polarization rate. Through the geophysical and geochemical anomaly analysis in combination with the geological characteristics, the authors hold that II, III anomalies are the most favorable metallogenic physicochemical positions. 6 IP sounding profiles were deployed to carry out the anomaly verification work, and then two drill holes were arranged in the favorable ore-forming places chosen from the Ⅲ anomaly area, which led to the discovery of lead-zinc mineralized body. According to the geophysical and geochemical anomaly characteristics and metallogenic geological conditions, combined with the validation results of drilling engineering, this paper summarizes the prospecting criteria, and points out that the II anomaly belt should be the next place for engineering validation.

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    Geochemical feature of head-space gas components of drill well and its application to petroleum reservoir identification
    LIANG Qian-Yong, XIONG Yong-Qiang, FANG Chen-Chen, LI Yun
    Geophysical and Geochemical Exploration. 2015, 39 (4): 704-714.   DOI: 10.11720/wtyht.2015.4.08
    Abstract   HTML   PDF (4866KB) ( 359 )

    Head-space gas of well logging is a fast and cheap technique to identify the depth of oil and gas reservoir, and the hydrocarbon indexes are usually used to distinguish the characteristics of oil or gas in the reservoir. Due to the unavoidable weight loss of gas during the sampling process of head-space gas, the problem as to whether the property of the hydrocarbons in the can is the same as the reservoir gas is an argumentative issue. Therefore, it is questionable to use the indexes of hydrocarbon of head-space gas to distinguish the characteristics of reservoir petroleum. In this study, a model for identifying characteristics of the reservoir gas or oil by head-space gas of drill core was established by a comparative study between the drill core head-space gas and the reservoir gas from the same depth. The result shows that the drill core head-space hydrocarbons are different from the reservoir hydrocarbons in concentrations, which further results in the difference of hydrocarbon indexes of the two gases in identifying the characteristics of petroleum reservoir. However, the isotopic composition (δ13C, δD) of the hydrocarbons of the head-space gas and that of the reservoir gas are identical, suggesting that the δ13C and δD values could be used to identify the characteristics of petroleum reservoir.

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    Soil geochemical characteristics and prospecting prediction of the Hujiadian area in Lishui, Jiangsu Province
    CHEN Dong, LIANG Shu-Neng
    Geophysical and Geochemical Exploration. 2015, 39 (4): 715-721.   DOI: 10.11720/wtyht.2015.4.09
    Abstract   HTML   PDF (4970KB) ( 497 )

    This paper summarized geological features, geochemical characteristics and element composition of soil survey data on the scale of 1:10 000 in Hujiadian area. It is shown that there exist high intensity, good zonation and obvious concentration centers of such anomalous elements as Au, Ag, Cu, Mo associated with gold deposits. The range of anomalies is spatially coincident well with tensile structural fracture zone and diorite-porphyrite vein rock in the study area. 8 combined anomalies (H-1~H-8) were delineated, of which H-1~H-4 have good metallogenic geological conditions and anomalous features and hence show favorable prospecting potential for gold. Trenches were constructed for H-1 combined anomaly, and two gold veins were found with grade (2.03~2.37) ×10-6 Prospecting criteria for gold were summarized according to metallogenic geological conditions and geochemical anomalous features in Hujiadian area. A prospecting target area for gold deposit was delineated along Zhaishan-Longgongshan zone in the northwest of the study area. Thus, Hujiadian provides a case for the exploration of gold in Jiangsu Province.

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    The prospecting method for tectonic rock type gold deposits in the greenstone belt, Tanzania
    CUI Xiao-Jun, PENG Jun, LI Shui-Ping, MENG You-Jie, MAO Jin-Biao, SI Jian-Tao
    Geophysical and Geochemical Exploration. 2015, 39 (4): 722-727.   DOI: 10.11720/wtyht.2015.4.10
    Abstract   HTML   PDF (3345KB) ( 782 )

    The tectonic rock type gold deposit is the most important deposit in the greenstone belt, Tanzania. In the light of geological, geochemical and geophysical characteristics of the typical gold deposit, the authors summed up some geochemical and geophysical techniques proved to be effective in exploration, and preliminarily proposed geophysical and geochemical prospecting method in search for tectonic rock type gold deposits:on the basis of geological survey, geochemical survey was conducted, and geophysical survey was carried out over the geochemical anomalies to delineate the prospecting area; subsequent anomaly inspection, geological evaluation and drilling verification led to the discovery of gold orebodies. The prospecting method will provide scientific basis for the exploration of tectonic rock type gold deposits in the greenstone belt, Tanzania.

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    Soil geochemical characteristics of the Pingbian vanadium-polymetallic deposit in Yunnan Province
    LI Qiang, WANG Dong, ZOU Guan-Yu
    Geophysical and Geochemical Exploration. 2015, 39 (4): 728-732.   DOI: 10.11720/wtyht.2015.4.11
    Abstract   HTML   PDF (3752KB) ( 407 )

    The Pingbian sedimentary vanadium polymetallic deposit is located in Wantang-Baiheqiao area, Pingbian County, Yunnan Province. It is a new type of vanadium ore deposit found in recent years in Yunnan. Through field investigation, rock mineral identification and geochemical soil survey, the authors consider that it is a deposit mainly controlled by stratigraphic lithology characterized by relatively stable ore-bearing strata and lithology. The orebody mainly occurs in carbonaceous silty argillaceous slate and black carbon-bearing silty calcareous argillaceous slate of lower 2nd member of Paleozoic Lanmuqiao Formation. Orebodies are stratiform or stratoid in form and are characterized by low-medium grade and large size, associated with Ag and other useful components. V, Ag, Mo, U and other metallogenic elements are fairly rich in the ore-bearing strata, in which V anomalies with high intensity and large scale form several concentration centers and have huge prospecting potential. R type cluster analysis shows that V, U, Mo are concentrated in a class and Cu, Ag in another class. V, U, Mo are the element combinations of deposition and Cu, Ag are the lower-medium temperature hydrothermal elements. This deposit might have experienced superimposition of Ag mineralization due to the influence of later hydrothermal activity. V-U-Mo combined anomalies are distributed in beaded cluster in NW-SE direction, consistent on the whole with the distribution and the exposed range of the Lanmuqiao Formation. V-U-Mo combined anomaly can be regarded as the geochemical prospecting indicator of the ore deposit.

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    The method effective experiment of transient electromagnetic in xiarihamu nickle copper
    WANG Xing-Chun, DOU Zhi, ZHENG Xue-Ping, DENG Xiao-Hong, LI Lei, WU Jun-Jie, ZHANG Jie, Yang Yi
    Geophysical and Geochemical Exploration. 2015, 39 (4): 733-737.   DOI: 10.11720/wtyht.2015.4.12
    Abstract   HTML   PDF (3807KB) ( 533 )

    In order to make the new technology of geophysical to better service for prospecting in Qimantage area. Based on integrated consideration about the deposit type, method and technology advantages and disadvantages and so on, we select Xiarihamu copper nickel mine as experiment area.the methods including physical measurement, downhole TEM and ground TEM, The results show that the rock (ore) with "low resistivity, high polarization, high density, strong magnetic", it's also indicate that this area has the prerequisites for gravity, magnetic and electrical exploration. The downhole and ground TEM method experiments results are in good agreement with the actual drilling data and geological profile. Transient electromagnetic method validity test achieved the desired effect. It supplies an effective and practical geophysical method for copper nickel mine prospecting in Qimantage in future.

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    The application of integrated methods to the coal exploration in Pingshanhu area
    LIU Yong-Liang, SUN Hai-Chuan, LU Guo-Fang
    Geophysical and Geochemical Exploration. 2015, 39 (4): 738-742.   DOI: 10.11720/wtyht.2015.4.13
    Abstract   HTML   PDF (8561KB) ( 423 )

    The exploration area is located on the southern margin of the piedmont pluvial slope of the North Mountain on the gobi desert and is covered largely by Quaternary sediments. Its geomorphology is characterized by broad and flat gobi desert. In order to find the coal resources in this area, firstly, the authors adopted the combination of electrical method and seismic comprehensive geophysical prospecting method, and collected relevant geological and geophysical logging data as the constraint conditions for comprehensive geological inferences to conduct quantitative interpretation of geophysical prospecting. Integrated geophysical inference shows that the geological structure is striking NWW, the basement in the northern part has been lifted and the middle Jurassic strata are missing, the southern part is a concave structure, the middle lower Jurassic strata in this area are complete and the coal potential is promising. According to the geophysical inference, drill holes for verification were deployed in this area, and the result shows that the verification drilling matches well with geophysical prospecting, thus providing a better basis for coal exploration in this area in the future.

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    The iterative Tikhonov regularization method for downward continuation of potential fields and its application to the Galinge iron deposit
    ZHAO Ya-Bo, LIU Tian-You
    Geophysical and Geochemical Exploration. 2015, 39 (4): 743-748.   DOI: 10.11720/wtyht.2015.4.14
    Abstract   HTML   PDF (1613KB) ( 419 )

    Analytic continuation for potential field is a widely used method for processing and interpretation, because downward continuation can suppress the influence of deep geological bodies and protrude the shallow layer anomaly. However, the downward continuation filter factor is a high-pass filter, leading to unstableness of the result, and therefore it can not be used to process the real data. The authors systematically studied and implemented the iterative Tikhonov regularization method for downward continuation of potential fields. In contrast to the continuation of potential field on the theoretical model, the iterative Tikhonov regularization method indicates better effectiveness than frequency domain. The authors also applied this method to Galingeiron deposit's magnetic data processing, and the results indicate that the iteration Tikhonov regularization method for downward continuation of potential fields is worthy to use in heavy overburden exploration areas.

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    The application of integrated geophysical and geochemical exploration application to metallic ore exploration in a mining area of northwest Zhejiang
    ZHOU Chang-Wei, HUANG Li-Yong, SUN Chang-Yi
    Geophysical and Geochemical Exploration. 2015, 39 (4): 749-755.   DOI: 10.11720/wtyht.2015.4.15
    Abstract   HTML   PDF (1579KB) ( 678 )

    The studied mining area of Zhejiang province is located in Tongcun of Kaihua-Zitong of Chun'an key exploration area in northwest Zhejiang. It is a favorable block of polymetallic resources, but its previous geophysical and geochemical prospecting work degree is low, with no breakthrough achieved. With the large copper pit mine as an example, the authors used ground high precision magnetic method, soil geochemical survey, CSAMT method and other geophysical and geochemical methods in combination with geological conditions to conduct comprehensive geophysical and geochemical anomaly interpretation and comprehensive evaluation. Drilling verification shows that geophysical and geochemical anomaly can indicate the direction for prospecting and achieve ideal geological effects, and can also play a guiding role in the further geological prospecting work of the neighboring ore blocks.

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    The application of GIS evidence weight method to the gold metallogenic prognosis in the northern part of the Xiao Hinggan Mountains
    ZHANG En, LI Ming-Song, WANG Bing, NIU Hai-Wei, LU Hui-Xiong, LI Cun-Jin
    Geophysical and Geochemical Exploration. 2015, 39 (4): 756-761.   DOI: 10.11720/wtyht.2015.4.16
    Abstract   HTML   PDF (1021KB) ( 372 )

    The condition of gold geological mineralization in the Xunke-Jiayin-Luobei area of northern Xiao Hinggan Mountains is very favorable.Because of the heavy surface coverage,geological work in the area has made no breakthrough in recent years.To accelerate the process of gold ore prospecting, the authors,based on probing into the relationship of geological,geophysical and geochemical information to lead-gold mineralization in northern Xiao Hinggan Mountains,extracted and constructed 14 evidence layers,such as fracture buffer,Early Yanshanian intrusive rocks buffer,Late Yanshanian intrusive rocks buffer,alteration remote sensing anomaly,geochemical anomaly and magnetic anomaly through a spatial analysis of the GIS system.Gold potential was calculated by the evidence weight model.According to the prediction,nine classⅠprospective areas,nine classⅡprospective areas and fourteen class Ⅲ prospective areas were delineated finally.The prospective areas have almost covered all known gold deposits.The results achieved by the authors have some indication significance for further ore-prospecting work in this area.

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    The comprehensive evaluation of oil and gas exploration combining hierarchy analysis and eigenvalue analysis
    WANG Jun-Lu, HE Yong-Hong, WANG Meng, FENG Bing, LIN Pin-Rong, CAO Jin-Zhou, YAN Xin-Zhi
    Geophysical and Geochemical Exploration. 2015, 39 (4): 762-767.   DOI: 10.11720/wtyht.2015.4.17
    Abstract   HTML   PDF (3509KB) ( 322 )

    Generally,one single non-seismic geophysical and geochemical method can not meet the requirements of oil exploration,and hence we need to use a variety of methods to carry out the comprehensive analysis and determine the favorable areas of oil and gas.In this paper,the authors studied the comprehensive evaluation of oil and gas exploration that combined the hierarchy analysis and the eigenvalue analysis.The application in the Erdos Basin oil and gas zone shows that the oil and gas anomaly areas delineated by this method has a good corresponding relationship with the known oil and gas enrichment areas controlled by drilling.

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    A tentative discussion on the detecting depth of controlled source audio magneto telluric method
    ZHONG You-Sheng, HAN Zi-Qiang, LUO Jiao, FENG Bing
    Geophysical and Geochemical Exploration. 2015, 39 (4): 768-774.   DOI: 10.11720/wtyht.2015.4.18
    Abstract   HTML   PDF (945KB) ( 746 )

    In this paper, the authors analyzed the characteristics of the horizontal electric dipole source electromagnetic expression of homogeneous half space, and then extended this expression to the bipolar source electromagnetic field. The relationships between CSAMT detecting depth and frequency, electric dipole moment, transceiver distance and the resistivity of the coating layer were studied based on bipole 1D simulation. The results show that, under the premise of guaranteed noise ratio, the factors that decide the maximum detecting depth of CSAMT method are corresponding frequencies when the detection enters the near region and transitional zone under the integrated action of transceiver distance and resistivity of the coating layer. The argument "the smaller the frequency, the larger the detecting depth' does not always hold water. When the detection enters the near region, the CSAMT method no longer has the detection capability. Statistics show that, when the electromagnetic field enters the transitional zone from the distant zone, the |kr| value is about 4.789; when the electromagnetic field enters the near zone from the transitional zone, the |kr| value is about 0.106. Then conclusions are drawn that the maximum detection depth of Cagniard apparent resistivity is about 0.3 times the transmitter receiver distance, and the maximum detection depth of full wave apparent resistivity is about 3.7 times the transmitter receiver distance. A case study has proved the above understanding.

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    Detection capability of grounded electric source TEM for thin layer
    CHEN Wei-Ying, XUE Guo-Qiang
    Geophysical and Geochemical Exploration. 2015, 39 (4): 775-779.   DOI: 10.11720/wtyht.2015.4.19
    Abstract   HTML   PDF (882KB) ( 592 )

    Nowadays, the short-offset grounded electric source transient electromagnetic method (SOTEM) is a hot research topic. In this paper, based on the 1-D forward calculation algorithm and using relative anomalies between vertical magnetic field responses generated by a thin layer and homogeneous half space, the authors investigated the detection capability of SOTEM for thin layered models with different resistivities, different thicknesses and different buried depths as well as the impact of different offsets. In addition, the difference between electric source TEM and loop source TEM as well as CSAMT was comparatively studied. It is concluded by analysis that low resistance, greater thickness, smaller buried depth and smaller transmitter-receiver offset will be favorable for increasing the sensitivity to the earth. On the other hand, the time domain electromagnetic method is more sensitive to low resistance layer than the frequency domain electromagnetic method, and the SOTEM and the loop source TEM almost have an equal detection capability when the offset is small. What we have done in this paper has important reference value for the field production.

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    A new magnetotelluric receiver
    CHEN Kai, WEI Wen-Bo, DENG Ming, JING Jian-En, WANG Meng
    Geophysical and Geochemical Exploration. 2015, 39 (4): 780-785.   DOI: 10.11720/wtyht.2015.4.20
    Abstract   HTML   PDF (4886KB) ( 454 )

    The magnetotelluric method (MT) is an effective means to detect the interior of the Earth. It is one of the research hotspots among geophysicists. The field observation system is the foundation of MT exploration. This method requires an observation system with some good characteristics, such as high reliability, high precision, multi-receiver synchronization and lightweight. The receiver integrates embedded computer, DTCXO, 24 Bits ADC, lithium batteries and other components. The typical dynamic range is 119 dB@ (fs=2 400 Hz), and the power consumption is about 1 600 mW. The receiver is equipped with low-noise, lightweight inductive magnetic sensors, electric field sensors, and self-test box, thus ensuring the reliability of the instrument. It has improved the quality of field data acquisition, and the equipment is more portable. Several indoor and field tests have verified the reliability of the receiver. The performance and portability could meet the requirements of land MT exploration.

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    The application of the fixed loop TEM method to Shihongtan area, Xinjiang
    LEI Yang, XI Zhao, NIU Li-Qun, LYU Jie
    Geophysical and Geochemical Exploration. 2015, 39 (4): 786-790.   DOI: 10.11720/wtyht.2015.4.21
    Abstract   HTML   PDF (2886KB) ( 382 )

    Shihongtan area is located at the southwest edge of Toksun, Turpan, Xinjiang. In order to clearly divide strata and identify structures, the authors conducted 3-component fixed loop survey in this area. Fixed loop configuration can obviously raise work efficiency compared with moving loop configuration. The authors managed to measure 3 km survey line by settling a 500 by 500 meter transmitter loop. By modeling such 3-component data, the result could achieve better solution in both dividing strata and identifying structures than apparent-resistivity profile. The results achieved by the authors are also meaningful to the explanation and geological modeling.

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    The least-squares reverse time migration for visco-acoustic medium based on a stable reverse-time propagator
    DENG Wen-Zhi, LI Zhen-Chun, WANG Yan-Guang, SUN Xiao-Dong
    Geophysical and Geochemical Exploration. 2015, 39 (4): 791-796.   DOI: 10.11720/wtyht.2015.4.22
    Abstract   HTML   PDF (1075KB) ( 492 )

    Based on a single SLS isotropic medium second-order pseudo-differential equation,the authors used the pseudo-spectral method to calculate numerical simulation.The authors propose introduction of regularization operator method to eliminate high-frequency instability caused by the backward propagation inverse process so as to build a stable reverse-time propagator and to achieve the amplitude compensating visco-acoustic medium least-squares reverse time migration.Marmousi model shows that,compared with least-squares reverse-time migration visco-acoustic least-squares reverse-time migration can correct the effect of viscosity and produce more accurate and better reliable amplitude preservation imaging section.

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    Wide-azimuth 3D angle gathers based on wave equation migration
    CHEN Fei-Xu, LI Zhen-Chun, ZHANG Kai, SUN Qi, SHANG Jiang-Wei
    Geophysical and Geochemical Exploration. 2015, 39 (4): 797-804.   DOI: 10.11720/wtyht.2015.4.23
    Abstract   HTML   PDF (2511KB) ( 537 )

    Wide-azimuth angle gathers based on 3D wave equation migration contain not only the information of local reflection angle but also that of subsurface azimuth angle.It fully reflects the illumination of the target from different azimuths under the wide-azimuth acquisition,which makes itself important in 3D migration velocity analysis in complex structure.Starting with the viewpoint of angle decomposition,this paper discussed the relationship of ray parameter,reflection angle and local azimuth angle,implemented the mapping of the local offset-domain common image gather to the angle-domain common image gather,and gave the work flow of the method.Synthetic model tests and field data application demonstrate that the angle gathers extracted with the proposed method can truly reflect the reflection information from different azimuths in the subsurface,provide gather basis for 3D seismic pre-stack depth migration, and thus can be used to analyze amplitude versus angle in 3D.

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    High-precision tomography velocity inversion based on well data constraint
    BAI Xue, LI Zhen-Chun, ZHANG Kai, SONG Xiang-Yu, YANG Guo-Quan, SHANG Jiang-Wei
    Geophysical and Geochemical Exploration. 2015, 39 (4): 805-811.   DOI: 10.11720/wtyht.2015.4.24
    Abstract   HTML   PDF (1754KB) ( 689 )

    Logging data is considered to be prior information which is fairly accurate and reliable.The utilization of the logging velocity information in the tomographic inverse function system can enhance the precision and efficiency;Nevertheless,it fails to describe the small-scale targets exactly.In view of such a situation,the authors propose a high-precision tomography velocity inversion method based on the well data constraint in this paper.First,the traditional well data constraint tomography velocity inversion is performed.Under the presumption that he velocity of grids in the well position remains the same,the inversion function is establishd based on the well data constraint,the velocity field is updated,and the primary migration image is updated.Second,the logging velocity is used to restrain the migration depth,process velocity analysis and perform precise modeling,thus improving the modeling accuracy greatly.At the same time,the number of the inversion iteration is reduced and the precision is improved.Examples from the synthetic dataset and field data processing demonstrate the feasibility and validity of this method compared with traditional tomography velocity inversion and waveform inversion.

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    Application of HS-LPME technique in geochemical exploration of oil and gas: A case study of BTEX indicators
    GAO Jun-Yang, CHEN Zhe-Chun, NING Li-Rong, LU Li, YANG Fan, HUANG Xin, YANG Jun
    Geophysical and Geochemical Exploration. 2015, 39 (4): 812-816.   DOI: 10.11720/wtyht.2015.4.25
    Abstract   HTML   PDF (2810KB) ( 329 )

    BTEXs are effective reservoir molecule tracing indicators. But low levels of BTEXs in complex matrix samples increase the difficulty of detecting. In this study, a qualitative and quantitative detection method of BTEXs in soil as a geochemical exploration indicator was established using HS-LPME combined with GC/MS. Higher accuracy and precision were obtained. With the advantages of less sample, simple operation, low cost and environmental friendly, this method lays a foundation for its application in surface geochemical prospecting for oil and gas. Results in known oil area showed that there was certain relationship between the toluene concentration in surface soil samples and the underlying oil reservoir. This method was suitable for detection of BTEXs in soil samples in surface geochemical prospecting for oil and gas.

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    CSAMT data interpretation by fine processing and constraint inversion in the porphyry copper deposit
    HUANG Li-Shan, HOU Yi-Jun, YANG Hong, WANG Jian-Chao, ZHAO Yi, ZHANG Li
    Geophysical and Geochemical Exploration. 2015, 39 (4): 817-822.   DOI: 10.11720/wtyht.2015.4.26
    Abstract   HTML   PDF (4971KB) ( 467 )

    In geophysical data inversion of metallic ore deposits, the automatic inversion of data retrieval models often appears to be inconsistent with the objective of geological phenomena. However, the depth, shape, size, range and other changes in the physical properties of the inversion model with known constraints can restrict the inversion model, so that the inversion of geoelectric model can become more realistic. In this paper, with the application of the controlled source audio magnetotelluric survey (CSAMT) in a porphyry copper deposit of Guangxi as an example, the authors, taking into account the validity of the CSAMT method, the resolution and physical properties of rocks and minerals and the deposit characteristics and other factors, utilized the shallow known orebodies and wall rocks to perform inversion of profiling geoelectric model and made positioning and forecasting of deep orebodies. Drilling verification shows that remarkable ore-prospecting results have been achieved.

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    Noise processing methods and application study of MT in the ore concentration area
    WANG Da-Yong, ZHU Wei, FAN Cui-Song, YAO Da-Wei
    Geophysical and Geochemical Exploration. 2015, 39 (4): 823-829.   DOI: 10.11720/wtyht.2015.4.27
    Abstract   HTML   PDF (7264KB) ( 369 )

    In this paper, the authors studied the de-noising method theories based on manual translation, linear interpolation fitting and EMD decomposition, compiled corresponding interactive and EMD decomposition de-noising programs, and then processed the measured MT data. Examples given in this paper show that the capacity of traditional remote reference method for removing the strong energy interference is limited, and simple application of interactive de-noising also has certain insufficiency. In contrast, EMD based on interactive de-noising can remove noise effectually and thus improve signal-noise ratio in the ore concentration area. Based on comparing the measured profile inversion results before and after de-noising processing, the authors point out that the false anomaly after de-noising processing can be effectively removed, and hence more accurate geological interpretation basis can be provided.

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    The addition-subtraction method for removing linear noise: A case study of the seismic data in Ordos loess plateau
    YANG Cheng-Zeng, FENG Yong-Qiang, TONG Qing-Jia, WANG Xiang-Chun
    Geophysical and Geochemical Exploration. 2015, 39 (4): 830-836.   DOI: 10.11720/wtyht.2015.4.28
    Abstract   HTML   PDF (7075KB) ( 655 )

    Because of the topography characteristics and the complicated surface seismic geological conditions of the exploration area in Ordos Loess Plateau,the seismic data acquired have strong multiple sets of linear noise.The elimination of the linear noise and the improvement of SNR of seismic signal is one of the key problems in seismic data processing.In this paper,the authors conducted a comprehensive analysis and study of all types of linear noise as well as the multiple sets of surface waves.Based on the linear noise's linear characteristics,dip features and coherence properties, the authors used the addition-subtraction method to remove the linear noise.A comparative analysis shows that this means is a high-fidelity method that has a strong capability for suppressing linear noise and improving the quality of data processing,thus showing a significant effect.

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    The 1D TDEM forward modeling for induced polarization media
    ZHOU Lei, YAN Liang-Jun, XIE Xing-Bing, WANG Zhi-Gang, SUI Jun-Jie
    Geophysical and Geochemical Exploration. 2015, 39 (4): 837-841.   DOI: 10.11720/wtyht.2015.4.29
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    To study the IP effect ("induced polarization effect") generated by IP media according to the rule of TEM response, the authors firstly solve the electromagnetic responses which have the same K-factor, introduce the Dias model describing IP effect in the frequency domain, and then use the sinusoidal transform to get TEM response with the IP information. As the chargeability increases, the amplitude of the electric filed is changed in the homogeneous half-space. With the increase of the relaxation time, the IP anomaly appears in the late time. And the IP anomaly appears in the early time when the polarization resistance coefficient is increased. Among different resistivity models with the same chargeability in the middle layer, it can be summarized that the H-type model can easily show the polarization layer, while the K-type is the worst model to manifest the induced polarization effect, with the performance of the A and Q-type lying between H and K type.

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    Linear interference suppressed by Cadzow filter method
    CAO Zhong-Lin, LI Zhen, CHEN Ai-Ping, YANG Hai-Tao, CHEN Bo
    Geophysical and Geochemical Exploration. 2015, 39 (4): 842-847.   DOI: 10.11720/wtyht.2015.4.30
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    In the low signal-to-noise ratio seismic data,linear interference suppression is one of the key processing chains.The traditional method of linear interference suppression in frequency domain tends to generate the phenomena of aliasing and earthworms.Therefore,the authors propose a filtering method based on Cadzow to suppress linear interference.Firstly,the seismic data will be transformed by linear function in the time-space domain.Secondly,according to the Cadzow filtering method,a two-dimensional Hankel matrix is created,and then singular value decomposition is run.Finally,by means of reducing the rank of matrix, linear interference is suppressed.The theoretical model and field data experiments show that the method can effectively remove linear noise and protect the effective wave,thus significantly improving the signal-to-noise ratio of pre-stack seismic data.

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    Curved-grid kriging gridding method and its application to near-station terrain correction in gravity measurement
    TANG Xiao-Ping, LIU Kuan-Hou, GENG Tao, FENG Zhi-Han
    Geophysical and Geochemical Exploration. 2015, 39 (4): 848-854.   DOI: 10.11720/wtyht.2015.4.31
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    In this paper,a high-accuracy and strong stability near-zone terrain correction method is discussed.Firstly,combining Kriging gridding method with curved-grid computation technology,a Curved-Grid Kriging Gridding Method(short for CGKG-M)and its extending edge techniques are implemented to realize data-gridding in circle area;Next,this method is used to compute near-zone terrain correction value and realize the gravity measurement near-zone terrain correction value's computation which contains any angles and circles.Finally,some modeling tests,real data computation and error analysis of this method are carried out.The research result has shown that CGKG-M near-zone terrain correction value computation method has some characteristics,such as high computation accuracy,strong stability and flexibility.It is a simple,efficient and fast method for near-zone terrain correction value computation which matches the measurement data form of GTCS-1 gravity measurement near-station correction instrument.

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    The tunnel lining detection numerical simulation based on GPRMax and its application
    XIAO Du, LI Wen-Jie, GUO Peng
    Geophysical and Geochemical Exploration. 2015, 39 (4): 855-859.   DOI: 10.11720/wtyht.2015.4.32
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    Using GPRMax basd on the theory of finite difference time domain (FDTD), and taking into account three different frequency antennae of 400 MHz, 900 MHz, and 1500 MHz, the author simulated the image characteristics of the ground penetrating radar reflection and interference signal obtained from the objects inside tunnel lining, including different steel mesh densities, different rebar diameters, steel arches and air layers. An experiment of ground penetrating radar survey was carried out on concrete specimen, the Kirchhoff migration was used to process the numerical simulations and experimental data, so as to suppress the diffracted wave and multiple wave coming from rebar mesh and improve range resolution of weak reflection signal under steel mesh. Based on the comparative analysis of the numerical simulation data and the experimental data on concrete specimen and tunnel lining detection results, the authors reached some conclusions which can be used as a reference for obtaining better detection results of ground penetrating radar survey in tunnel lining.

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    The performance characteristic of spherical boulder in the georadar detection
    LIU Cheng-Yu, LIN Yi-Peng, LIN Chao-Qun, LIU Han-Qing
    Geophysical and Geochemical Exploration. 2015, 39 (4): 860-866.   DOI: 10.11720/wtyht.2015.4.33
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    The boulder distributed in granite weathering crust has great harm on the engineering construction. Accurately determine the size and distribution of boulder has important practical significance. In this paper, by adopting the combination of field measurement and numerical simulation method to study the performance characteristic of spherical boulder in the georadar detection. The following conclusions are drawn: There is an obvious of radar wave in the boulder reflection. The open width of reflex is increase with the boulder diameter and the buried depth. In radar wave,the radius of curvature of vertices has approximate linear relationship with the boulder diameter. And has Quadratic polynomial relationship with the buried depth. The conclusions obtained in this paper have a certain guiding role on analyzing georadar detection results about boulder.

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    The application of integrated geophysical exploration to the hydrogeology discrimination of the large fracture tunnel construction period
    HU Bo-Wen, CHEN Li, YAO Hong-Chao, ZHANG Fa-Wang, ZHANG Jin, ZHAO Miao
    Geophysical and Geochemical Exploration. 2015, 39 (4): 867-871.   DOI: 10.11720/wtyht.2015.4.34
    Abstract   HTML   PDF (3590KB) ( 539 )

    When the coal roadway crosses fracture construction, efficient integrated geophysical prospecting technology is often used to determine its water content. However, with the popularization of the integrated geophysical exploration technique, researchers have gradually found that its exploration precision is not high. In combination with the coal mine roadway construction in an ancient city of Shanxi, the authors selected the integrated geophysical prospecting method in combination with water chemical isotope verification and clearly revealed the hydrogeological condition of the coal roadway construction period, thus making up the defect of the integrated geophysical exploration whose accuracy is not high. It is shown that integrated geophysical exploration technique in combination with water chemical isotope can greatly reduce the hidden dangers in the coal roadway construction. The results achieved by the authors provide a demonstration for the same or similar coal roadway engineering construction.

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    The application of the multi-electrode resistivity method and reflection seismic method to the landslide detection in the Jiuhua Mountain
    ZHOU Guan-Qun, ZHAI Fu-Qin, HAO Zhi-Chao, CAO Yu, CHEN Xing-Hai, CHEN Guang-Ming, WANG Zong-Tao, Miao Yuan-Yuan
    Geophysical and Geochemical Exploration. 2015, 39 (4): 872-876.   DOI: 10.11720/wtyht.2015.4.35
    Abstract   HTML   PDF (2979KB) ( 926 )

    With the charaCTeristics of simplicity and quickness, multi-electrode resistivity method can find out the important landslide geological information such as the thickness, the range and the developmental characteristics of the landslide body in landslide geological hazards exploration; and then, through drill hole deployment, the physical-mechanical parameters which are indispensable to work out the stability calculation can be obtained. The testing results indicate that multi-electrode resistivity technology performs well in the exploration of landslide body, the result is the same as the reflection seismic total deviation detection technology, and the relevant geological parameters acquired can provide a basis for the evaluation and control of landslide.

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