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Table of Content

    25 April 2004, Volume 25 Issue 2
    Episodes and geodynamic setting of Himalayan movement in China
    Jia Chengzao, He Dengfa, Lu Jiemin
    2004, 25(2):  121-125,169.  doi:10.11743/ogg20040201
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    In 1945, Mr. Huang Jiqing suggested using the term Himalayan movement to describe the Cenozoic orogenic movement in China. This concept has widely been accepted by the geoscientists. However, disagreements still exist regarding the episodes and geodynamic setting of tectonic movements. Based on analysis of basic concepts suggested previously, and in combination with various data, including geology, geomorphology, magmatic activities and structural deformation, it is proposed that Himalayan movement can be divided into early, middle and late episodes, which are corresponding respectively to tectonic activities in late Eocene, between Paleogene and Neogene, and between Noegene and Quaternary. Collision of Indian and Eurasia plates and continuous compression led to strong compression, shortening and uplifting of Qinghai Tibet Plateau including its southeastern and northern margins. East ward compression of East Asia continent, uplifting of deep lithosphere and back arc spreading resulted in extensional rifting in eastern China and its peri Pacific zone.

    Gas pools in China have mainly been formed and finalized during tectonic movements since Neogene
    Wang Tingbin
    2004, 25(2):  126-132.  doi:10.11743/ogg20040202
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    Most of the gas fields in China have been formed and finalized in Neogene Quaternary,which distribute widely in various petroliferous basins.The gas pools in China are generally characterized by late or super late hydrocarbon generation and accumulation,and by restriction of tectonic evolution since Neogene.The close relationship between the gas pools in China and tectonic evolution since Neogene can be summarized as follows:(1)In west China,the foreland basins,formed during this period,constitute one of the main gas accumulation provinces in China,and provide favorable conditions for the formation of numerous gas fields.The gas fields in these basins have mainly been formed and finalized in this period.(2)In central China,all the gas fields in Sichuan basin have been formed and finalized in this period,while gas accumulations in Jingbian Wushenqi area in Erdos basin have further been enriched in this period.(3)In east China, these tectonic movements create favorable geological conditions for late reservoiring of gas in Baohai sea area,and promoting the formation of some gas fields in other basins(or depressions).(4)In offshore area,they promote not only the rapid formation of organic origin gas fields,but also the formation of inorganic origin non hydrocarbon gas fields,as well as the formation of a unique reservoiring pattern with mixed source of organic and inorganic origin genetic gases.

    Neotectonic movement and hydrocarbon accumulation in petroliferous basins,offshore China
    Gong Zaisheng
    2004, 25(2):  133-138.  doi:10.11743/ogg20040203
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    Neotectonic movements in offshore China are mainly represented by unconformities that occurred by the end of Miocene and between Pliocene and Quaternary, subsidence and migration of depocenter during Miocene and Quaternary, well development of late faulting,active earthquake,and various structural traps resulting from Neotectonism.Neotectonism is contributed to changes of regional stress field caused by various factors,such as recent plate movement,replacement and migration of crust and mantle in deep earth,slumping and depressing of sedimentary bodies in transitional zone between shelf and continental slope,and rapid subsidence of basins.Terrain deformation or faulting occurred in some areas where stress concentration resulted in losing equilibrium. Neotectonism in offshore China adjusted and controlled hydrocarbon accumulation and field distribution in each petroliferous basin.Neotectonism in Bohai Bay basin controlled late hydrocarbon accumulation in Bozhong depression and surrounding areas;diapirism in Yingehai basin controlled late gas accumulation;neotectonism in Zhujiangkou basin controlled gas accumulation in the northern slope zone of Zhu Ⅱ depression;while that in Xihu depression partially disrupted oil and gas reservoirs.

    Discovery of paleo-oil-reservoir in Qiangtang basin in Tibet and its geological significance
    Wang Chengshan, Yi Haisheng, Liu Chiyang, Li Yalin, Zou Yanrong, Wu Xinhe, Deng Bin, Yang Xingke
    2004, 25(2):  139-143.  doi:10.11743/ogg20040204
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    Palaeo oil reservoirs are distributed in a narrow belt, 100 km long in E W direction and 20 km wide in S N direction, in Bilongco Angdarco area of Qiangnan depression in the southern part of the central uplift zone of Qiangtang basin.They are exactly a group of oil seepages.The outcropped rocks are the Middle Jurassic Buqu Fm.,dark brown and brownish gray dolomite.They are deposited mainly as biohermal complex.Correlation shows that hydrocarbons in the palaeo oil reservoirs have been sourced mainly from Lower Jurassic.Modelling of hydrocarbon generation process indicates that there have been two hydrocarbon generation and expulsion processes,one in 140-150 Ma and another since 20 Ma. The discovery of the palaeo oil reservoir belt further verifies that Qiangtang basin has good petroleum prospect.

    Transfer zone and its relation with distribution of sand bodies
    Chen Fajing, Jia Qingsu, Zhang Hongnian
    2004, 25(2):  144-148.  doi:10.11743/ogg20040205
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    Three topics are discussed in this paper.(1)Concept and general characteristics of transfer zones in fold thrust zones.A transfer zone can be defined as an accommodation structure resulting from conservation of regional shortening strain during compressional deformation.It can be divided into two types:vertical and lateral transfer zones.Segmentation of fold thrust is realized by lateral transfer zone with the pattern of strike slip fault.(2)Concept and general characteristics of transfer zones in extensional tectonics.A transfer zone in a rift system can be defined as an accommodation structure resulting from conservation of regional extensional strain.It can also be divided into vertical and lateral transfer zones.Segmentation of rift system is realized by lateral transfer zone with the pattern of lateral uplift.(3)Function of transfer zones in development of sand bodies in sedimentary basins.Distribution of sand bodies is closely related with transfer zones.Sand bodies of alluvial fan,fan delta and turbidite fan can successively develop in the steep slope and in the center of lake basins that are corresponding to topographic lows and associated drainages controlled by lateral transfer zones.

    An informal discussion on experiences and lessons of petroleum exploration in foreland over-thrust zone
    Gan Kewen
    2004, 25(2):  149-155.  doi:10.11743/ogg20040206
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    Foreland basin is an orogenic foredeep filled with terrigenous clastics,that has been developed on a craton and has been converted from a passive margin and platform-type sedimentary area.Complex structural deformation,from thick skinned to thin-skinned structures,has occurred in the orogenic belt and its frontal region along with compressional deformation;and structural styles are varied,due to the control of tectonic settings,sedimentary sequences and movement characteristics.Although foreland basin is the most prolific basin type,hydrocarbon accumulations can only be preserved in regions where there are synorogenic sedimentary covers.Since thrust-fold structures are clear,and there are oil and gas seepages in the area neighboring the orogenic zone,thus the mountain front became the main objective area in the early stage of exploration.The exploration campaign in foreland overthrust zone since 1975 has been the result of advances in 3-D seismic survey and drilling technologies which make it possible to recognize structural features and trap conditions beneath the thrusts.Failures often occur in exploration when the thrust zones are taken as the main targets for exploration of hydrocarbon accumulations.Practices have shown that only the basins that have preserved both the synorogenic sediments and underlying pre orogenic sediments would have exploration potentials.

    Petroleum geologic conditions in foreland thrust fold belts in west-central China and proposals for exploration
    Zheng Herong, Li Tiejun, Cai Liguo, Long Shengxiang
    2004, 25(2):  156-161.  doi:10.11743/ogg20040207
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    The foreland thrust-fold belts in west-central China are located in the hinterland of Eurasia.They have experienced multiple tectonic cycles and multiple episodes of tectonic movements since Protozoic along with the accretion of Eurasia. The Himalayan intracontinental orogeny finalized the foreland thrust fold belts on both sides of Tian Shan and on northern side of Kunlun mountain.Continental source rocks,composed mainly of Triassic and Jurassic coal measures and argillaceous rocks,are developed in these foreland thrust-fold belts due to the unique tectonic setting and evolution history.The oil and gas pools in this area are characterized by multistage and mainly late stage hydrocarbon accumulations,as a result of long hydrocarbon generation and migration history and structural traps finalized in the late stage.Areas with good preservation conditions and well developed cap rocks are favorable for hydrocarbon accumulation.Efforts should be focused on theoretical study of the unique hydrocarbon accumulation conditions and features in the foreland thrust-fold belts in west-central China and on the relevant technological research,in addition to drawing on foreign exploration experiences in similar regions.

    Late Cenozoic squeezing out tectonism in Qinghai-Tibet Plateau and its impacts on late hydrocarbon accumulation in rift basins in eastern China
    Zhang Yueqiao
    2004, 25(2):  162-169.  doi:10.11743/ogg20040208
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    Based on kinematic and geochronologic analyses of the strike slip thrust deformation system in eastern Qinghai Tibet plateau, and in combination with the study of neotectonic deformation characteristics in North China,this paper proposes a 3-stage kinematic model of east-ward squeezing-out tectonism in eastern Qinghai-Tibet Plateau during the late Cenozoic,describes the presentation of tectonic deformation and pattern of block movement occurring in each squeezing-out stage,and discusses the control of squeezing out tectonism on late hydrocarbon accumulation in rift basins in eastern China.The first squeezing-out stage that occurred during the middle and late Miocene(12~5 Ma)was remarkably characterized by tectonic deformations of strong left-lateral strike-slip movement of Xianshuihe fault zone,right lateral strike slip movement of Honghe fault,and east-ward squeezing-out of Chuan Dian(Sichuan-Yunnan)block.This tectonic squeezing-out stage resulted in counterclockwise rotation of South China Block,and led to the development of right-lateral extensional-shear stress field in the northern shelf of South China Sea and reactivation of the near E W trending extensional fault system in Pearl River basin.The second squeezing out stage that occurred during the Qinghai-Tibet movement in Pliocene and Early Pleistocene(about 4~0.8 Ma),was characterized by prominent tectonic deformations,such as strong left-lateral strike-slip movements of Kunlun-Qinling fault system and Haiyuan fault,counterclockwise rotation of the sub-blocks in North China,extensional deformation of the graben system in periphyery of Ordos block,right-lateral shear movement of the NNE faults in Bohai Bay basin, and right-lateral strike slip movement of Tanlu fault.This tectonic squeezing-out stage led to the clockwise rotation of South China block.The third squeezing-out stage that occurred since middle and late Pleistocene resulted in the clockwise and turbine like rotation of Chuan-Dian block around the late Himalayan east tectonic belt,strike-slip movement of Minshan-Longmenshan tectonic belt with weak crust shortening,and weakening of eastward squeezing-out of South China Block.These three Cenozoic tectonic squeezing out stages have heavily influenced the development of fault basins and late hydrocarbon accumulation in the offshore shelf in eastern China.

    Neotectonism and Neogene oil and gas pools in the Bohai Bay basin
    Li Dawei
    2004, 25(2):  170-174,184.  doi:10.11743/ogg20040209
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    Studies of regional gravitational field,tectonic evolution, volcanic activities,earthquake and seismic data show that neotectonic movements are active in Bohai Bay basin.The existing Neogene oil and gas pools are mainly distributed in depressions,such as Bozhong,Jiyang and Huanghua,where neotectonic movements are relatively active.The neotectonic movements since Pliocene play a key role in the formation of large Neogene fields,though many other geologic factors make also their contributions.The neotectonic movements would not only improve hydrocarbon accumulation,but would also modify the Paleogene palaeo-pools,leading to the formation of Neogene secondary oil and gas pools through remigration and re accumulation.Comprehensive analysis of seismic and drilling data indicates that the Neogene oil and gas pools in this region are mainly distributed in the reverse drag structures on the footwalls of large inherited active faults.The Bozhong depression and the surrounding fault zones with relatively active neotectonic movements are expected to be favorable areas for exploration of Neogene oil and gas pools.

    Characteristics and petroleum geological significance of Himalayan orogeny in Kuqa foreland basin
    Zeng Lianbo
    2004, 25(2):  175-179.  doi:10.11743/ogg20040210
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    Himalayan orogeny is the main period of tectonic deformation and finalization of structures,as well as occurrence of abnormal high pressure and hydrocarbon accumulation in Kuqa foreland basin.Based on analysis of tectonic deformation and rock memory information,Himalayan movement in Kuqa foreland basin can be divided into three stages,corresponding to the end of Oligocene,the end of Pliocene and the end of early Pleistocene,with compressional intensity progressively strengthening and reaching peaks in late Himalayan.The neotectonics since middle Pleistocene mainly result in two or three uplifts,relatively weak folding and thrusting,and destruction of hydrocarbon accumulations in the area.Structural deformation in Kuqa foreland basin have been developed since early Himalayan,and the structural zones have successively been developed later and later southwards,which control the zonal distribution patterns of thrust folds,structural traps and oil and gas pools.The strong lateral compression in late Himalayan orogeny is the main factor leading to the abnormal high pressure,and the main controlling and driving forces for hydrocarbon migration and accumulation.Himalayan orogeny destroys and adjusts,to some extent, oil and gas reservoirs in the area.

    Effects of neotectonism on late hydrocarbon accumulation in Carboniferous in Tazhong 45-Manxi 1 block
    Liu Yinhe
    2004, 25(2):  180-184.  doi:10.11743/ogg20040211
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    Detailed analysis of palaeostructural evolution of the marker on top of Carboniferous limestone shows that the Tazhong 45-Manxi 1block was a large palaeo anticlinal structure before the deposition of Paleogene. The structure was basically stable despite the facts that there were displacement of structural high and modification of structural features during its long succeeding development. The neotectonic movements in Paleogene,especially in Neogene, changed completely the structural appearance into one limb of a north-dippping large nose-like structure, resulting in different hydrocarbon migration direction and reservoiring conditions. In the area along the direction of hydrocarbon migration and accumulation from limb to crest of the structure, the updip pinchout zones of Donghe sandstone in the lower part of Carboniferous and groups of low to very low amplitude structural traps would be favourable to ate reservioring. They would,therefore, be the potential hydrocarbon accumulation zones.

    Impacts of Himalayan movement on petroleum system in Songliao basin
    Ren Yanguang, Chen Junliang, Feng Zhiqiang, Lin Chunhua, Leng Penghua
    2004, 25(2):  185-190.  doi:10.11743/ogg20040212
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    Based on analyses of data including neotectonics earthquake,drilling,seismic,stratigraphy,structural features and satellite remote sensing,it is believed that Himalayan movement can be divided into three episodes in Songliao basin.The first and third episodes have mainly been affected by the Indian plate and result in NE SW regional principal compressive stress;while the second episode has mainly been affected by the Pacific plate and has given rise to NW-SE or nearly W-E regional principal compressive stress;the NW tectonism in the third episode has important effects on the early formed structural traps and the remigration and accumulation of hydrocarbons in those traps.The Tertiary in Songliao basin was deposited in a compresso depressed basin,characterized by limited distribution of formations,coarse grained clastics,and the uplifted area to be the provenance.Analysis of the Tertiary tectonic deformation ellipsoid in Songliao basin reveals that the direction of compressional stress turned from N-S to nearly W-E in the middle and late Paleogene(since 43 Ma).Under compression at the end of Cretaceous,the moderate depth and shallow structures grew progressively and provided good traps for hydrocarbon accumulation.The moderate depth and shallow faults are the result of superposition of multistage fracturing,and faults formed in different stages have different extending characteristics.NE and NNE faults were mainly developed under nearly E-W extensional stress during the deposition of Qingshankou Formation;only the nearly E-W faults were developed under nearly S-N extensional stress at the end of deposition of Yaojia Formation;and the NNW and NW faults were mainly developed under left lateral compresso shear stress after the deposition of Mingshui Formation.Structural inversion at the end of deposition of Mingshui Formation has resulted in the Songliao basin entering the peak of hydrocarbon generation;and changes of direction of compressional force has resulted in the opening of shallow and moderate depth old faults with different directions,which would consist of multi directional migration pathways.The compressional setting would not only provide pathways and reservoirs for hydrocarbon migration and accumulation,but would also be favorable for generation and preservation of hydrocarbons,thus realizing good matching of hydrocarbon generation,migration,accumulation and preservation.
    Overthrust tectonic in northern Qinling-Dabie orogenic belt and basin-controlling faults in Zhoukou depression and Hefei basin
    Sun Xiaomeng, Zhang Meisheng, Long Shengxiang, Hao Fujiang, Liu Pengju, Liu Changyin
    2004, 25(2):  191-198.  doi:10.11743/ogg20040213
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    Meso-Cenozoic overthrusting in northern Qinling-Dabie orogenic belt can be divided into five episodes,namely Indonisian(T2-T3),Early Yanshanian(end of J2-J2),Late Yanshanian(end of K1),End of Yanshanian(end of K2)and Early Himalayan (end of E).The basin controlling faults in Zhoukou depression and Hefei basin are the extension of the overthrust tectonic in Qinling-Dabie orogenic belt.The overthrust tectonics in the orogenic belt in the basin are characterized by their temporal synchrony and close spatial correlation.They would not only control the distribution pattern,structural framework,stratigraphic development and sedimentary formation of the basin,but would also control the formation and evolution of the basin and define the nature and type of the basin.The coupling of Mesozoic basin and range structures has been formed in the geodynamic setting of collision of Yangtze and North China plates,intracontinental subduction,and mountain uplift,extension and collapse.The overthrust tectonics at the end of Paleogene are related to the remote effect of subduction of Indian plate beneath Eurasian plate.

    Structural features of fold-thrust zone in Kashi depression,western Tarim basin
    Luo Jinhai, Zhou Xinyuan, Qiu Bin, Yang Zhilin, Yin Hong, Shang Xinlu
    2004, 25(2):  199-203.  doi:10.11743/ogg20040214
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    Fold thrust zones in northern edge of Western Kunlun and in southern edge of Southern Tianshan,with different structural features,are developed in southern and northern Kashi depression,respectively.The fold thrust zone in southern edge of Southern Tianshan is characterized by its S-N zonation and E-W segmentation;deformation in the eastern segment is generally stronger than that in the western segment,and it is also affected by the Talas Ferghana fracture.The fold-thrust zone in northern edge of Western Kunlun is relatively heavily influenced by the Pamir Arc.The ophiolitic melange in the orogenic zone have been involved in the thrust zone where many formations are inverted.Besides,a large Wupoer-Piaoertuokuoyi piggyback basin is developed.Difference between the pre-Mesozoic in the two fold thrust zones is significant,while it decreases progressively upward,indicating that Kashi depression has evolved into a unique sedimentary unit since Mesozoic.The unconformities do not strictly correspond to each other in the two fold thrust zones.The number of unconformities in the fold thrust zone in northern edge of Western Kunlun is larger,and the horizon is lower than that in the southern edge of Southern Tianshan,revealing that the development of the former is a little bit earlier and the thrusting is stronger than that of the latter.

    Major hydrocarbon migration pathway system in western slope zone of Songliao basin
    Xiang Caifu, Xia Bin, Xie Xinong, Feng Zhiqiang
    2004, 25(2):  204-208,215.  doi:10.11743/ogg20040215
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    Analyses of data acquired in over 400 wells have reproduced the structures on the bottom boundary of regional caprock (Nenjiang Formation) in the critical period of hydrocarbon migration. Four kinds of ridge like structures, saddle structural lithological ridge, fault-lithological ridge, anticlinal-lithological ridge and lithological ridge, can be identified from the structural map. The spacial array of these ridge-like structures acted as the major hydrocarbon migration pathway system to the western slope zone of Songliao basin. Hydrocarbons from Qijia-Gulong depression would be gathered through this major brancing pathway system, and then migrated northeastward to Fulaerji and westward to Pingyang oilfield,respectively.

    A study on periods of hydrocarbon accumulation and distribution pattern of oil and gas pools in Dongying depression
    Zhu Guangyou, Jin Qiang, Dai Jinxing, Zhang Shuichang, Guo Changchun, Zhang Linye, Li Jian
    2004, 25(2):  209-215.  doi:10.11743/ogg20040216
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    Two sets of active source rocks, the saline lake facies in the upper part of the 4th member of Shahejie Formation and the brackish deep lake facies in the lower part of the 3rd member of Shahejie Formation, have been developed in Dongying depression.Based on analysis of crude geochemical features and reservoir fluid inclusion,hydrocarbon accumulations have been formed in two different periods.In the first period,at the end of Dongying epoch in Paleogene,the source rocks in the upper part of the 4th member of Shahejie Formation in the depression center entered the oil threshold and began discharging hydrocarbons.Hydrocarbon generation was then disrupted due to the uplifting and erosion caused by Himalayan movement.The biomarker components in the crude indicate that oil maturity was low and the amount of hydrocarbons generated was limited in this period.In the second period,Neogene to Quaternary, along with successive and overall subsidence,the deeply buried source rocks both in the lower part of the 3rd member and in the upper part of the 4th member of Shahejie Formation would further be matured with intensifying hydrocarbon generation and relatively high oil maturity.Distribution patterns of crude oil generated in these two periods are obvious different.Oil reservoirs with low maturity on the edge of depression were mainly generated from the upper part of the 4th member of Shahejie Formation and accumulated in the first period; while that with high maturity in the center of depression were generated from the lower part of the 3rd member of Shahejie Formation and accumulated in the second period.Hydrocarbons in reservoirs in the transitional zone(slope zone)came from multi sources and accumulated in multi periods.

    Structural features and favorable exploration areas in southern margin of Junggar basin
    Sun Ziming, He Zhiliang, Mou Zehui
    2004, 25(2):  216-221.  doi:10.11743/ogg20040217
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    Three structural styles, including compression, strike-slip and inversion, are identified in the southern margin of Junggar basin based on analysis of structural evolution and seismic interpretation in this area and adjacent area. According to the spatial distribution of these structural styles, the E-W segmentation and S-N zonation of structural deformations, vertical differences of deformations, as well as deformational features of strike-slip wrench movement and their extending patterns have been studied. This area has favorable hydrocarbon accumulation conditions, and the control of structures on hydrocarbons is remarkable. The favorable exploration areas include fault related folds in piedmont thrust zones, anticlinal structures in the footwalls of piedmont thrusts and the anticlinal structures in the outer zone of piedmont thrust belt.

    Relationship between Himalayan movement and hydrocarbon accumulation in northern Songliao basin
    Lin Jingye, Lin Tiefeng, Zhu Defeng, Liu Li
    2004, 25(2):  222-225.  doi:10.11743/ogg20040218
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    Songliao basin has experienced Yanshan movement and Himalayan movement.Yanshan movement resulted in strong folding,and the large structures and oil/gas reservoirs in Daqing placanticline in northern Songliao basin have mainly been formed during this period.Himalayan movement,though being weak in Songliao basin,has adjusted and modified the early formed oil and gas pools and become a number of secondary oil and gas pools in the northern part of the basin.Homogenization temperature measurement of organic inclusion in minerals shows that there have been two periods of hydrocarbon expulsion from source rocks in the first member of Qingshankou Formation,and three periods of hydrocarbon infilling into Fuyu and Yangdachengzi reservoirs.According to authigenic illite K/Ar dating,secondary oil/gas reservoirs have been accumulated in 51-35 Ma in the above mentioned two reservoirs in the surrounding area of Qijia-Gulong and Sanzhao sags on both sides of Daqing placanticline.This indicates that during the Himalayan movement,the early formed oil and gas reservoirs in northern Songliao basin have sustained a certain alteration and then reaccumulated and become secondary oil and gas reservoirs.

    Tectonic characteristics and evolution of Mesozoic and Paleozoic in Lower Yangtze region,Jiangsu
    She Xiaoyu, Xu Hongjie, He Zhiliang
    2004, 25(2):  226-230,236.  doi:10.11743/ogg20040219
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    During late Indo-Sinian epoch and middle Yanshan epoch, the Mesozoic and Paleozoic in Lower Yangtze region in Jiangsu changed from a stable oceanic-continental plate tectonic system into an intraplate deformation system,resulting in a ramp thrust tectonic framework with NW to SE thrusting in northern Jiangsu and SE to NW thrusting in southern Jiangsu.In northern Jiangsu, the Sinian and Lower Paleozoic overthrusted along the Doushantuo Formation and a subsidiary detachment;while in southern Jiangsu,the Upper Paleozoic overthrusted along the Gaojiabian Formation detachment,and the Lower Paleozoic became duplex thrust structure under the control of the two detachments.In middle Yanshan epoch,NNE left lateral compresso shear and NW right-lateral compresso-shear strike-slip movements modified the former thrust structures.In late Yanshan epoch,the regional stress setting turned into NE-SE extensional environment,in which the overthrust nappe slipped back along fault ramps under gravitational force,resulting in a half graben like fault depression.While in southern Jiangsu,the Lower Paleozoic duplex thrust structure and the Upper Paleozoic thrusting over Silurian made it difficult to slip back, due to limited potential energy of vertical displacement.The uplifting in late Himalayan epoch finally led to the tectonic framework of Mesozoic Paleozoic being high in southern Jiangsu and low in northern Jiangsu.

    K-Ar isotopic chronological study of authigenic illite in reservoirs
    Zhang Youyu, Luo Xiuquan
    2004, 25(2):  231-236.  doi:10.11743/ogg20040220
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    As a new component in the research of reservoiring history,K-Ar isotopic chronological study of authigenic illite in hydrocarbon reservoirs has made remarkable improvement.Diagenesis of well-developed illite and its genetic relation with hydrocarbon infilling events are the prerequisites of application of this technology.Sandstone reservoirs that may not be suitable for using this technology include the shallowly buried or unconsolidated reservoirs,deeply buried reservoirs with smectite and/or random layer illite/smectite,reservoirs with relatively high content of kaolinite and chlorite,and reservoirs with well-developed authigenic illite but having no genetic relation with hydrocarbon infilling events.Comprehensive analysis of age data should be performed in combination with sample features and various geologic data.The measured age data should be reasonably used and certain bias should be allowed.For improving the technique,the following researches and tests should be strengthened:repetitive freezing and thawing experiment to model natural weathering process;XRD and TEM illite genetic type identifications and quantitative analysis technique.