, Volume 32 Issue 4
    

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    中国国家天然气科技攻关20年学术
  • Distribution of large-middle sized gas fields in China: geological characteristics and key controlling factors
    WANG Tingbin
    , 2005, 32(4): 1135-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The research on the geological conditions and key factors controlling the formation of large-middle sized gas fields is of great significance to the development of natural gas industry. The industrial gas fields have been found all around China except the Tibet autonomous region, Fujian, Zhejiang and Hu'nan Province. As for strait graphic horizons, gas fields occur from pre-Sinian to Quaternary, except in Silurian and Devonian. Large-middle sized gas fields with over 10 billion cubic meters have only been discovered in 11 basins in west, central and east China, and offshore areas(southern South China Sea and Taiwan have not been included in the statistics). The major gas reservoirs are distributed with apparent regional ties, and closely related to the gas-rich depressions, ages of source rocks and evolutional history of the basins. The 10 key factors controlling the formation of large-middle sized gas fields summarized from the geological conditions in China must be integrated with the specific geological conditions to analyze the gas-bearing conditions in the basins. China is characterized by relatively active tectonic movements since Neogene, abundant gas generation, gas-rich sags with relatively high gas-generating capacity and good regional sealing and preservation conditions are essential for the formation of large-middle sized gas fields in all basins, and they are also the most important ones among various geological factors. Late and ultra-late accumulation study is important for evaluating the prospects of natural gas in China.
  • Foreland thrust-fold belt features and gas accumulation in Midwest China
    JIA Chengzao
    , 2005, 32(4): 1136-0.
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    The 15 foreland thrust-fold belts developed in Midwest China are important gas enriching areas in the country. The foreland thrust-fold belts are of united tectonic background: ①The Mesozoic ones belong to the Northern Thetys basin-group, and the depositional basins, which developed under uniform tectonic settings and climatic paleo-zones, formed regional gas enriching Mz to Cz source-reservoir-caprock association. They also belong to the east part of Middle Asia coal related gas accumulation domains. The geological conditions are favorable for the formation of giant gas pools. ②The Cenozoic ones fall into the giant peripheral Qinghai-Tibet Plateau basin-mountain system, which resulted from the uplift of the Qinghai-Tibet Plateau and its northward compression due to the Indian/Eurasian collision. The foreland thrust-fold belts developed in the transitional zone between the mountain and basin. The movement of Indian Plate and Qinghai-Tibet Plateau during the Himalayan era controlled the thrust activities, which controlled the structural traps forming and the gas accumulation.
  • Geochemical characters of the giant gas accumulations with over one hundred billion cubic meters reserves in China
    DAI Jinxing; LI Jian; DING Weiwei; HU Guoyi; LUO Xia; TAO Shizhen; ZHANG Wenzheng; ZHU Guangyou and MI Jingkui
    , 2005, 32(4): 1137-0.
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    By the end of 2003, 6 giant gas fields each with reserves of over 100 billion cubic meters (bcm) have been discovered in China, 5 of which, Sulige, Wushenqi, Yulin, Daniudi and Jingbian gas fields are located in Ordos Basin, and Kela 2 gas field, is located in Tarim Basin. According to the gas compositions of 150 gas samples, the alkane carbon isotope data of 143 gas samples, and helium isotopic data of 21 gas samples, the geochemical characters of the giant gas fields are as follows: ① The gases have a high alkane content of over 90% and the CO2 content lower than 3%, mainly lower than 1.5%; ② The generally high δ13C values of C1-C4 gaseous hydrocarbons in gases confirmed significant contribution from humic source rocks, mainly the Permian-Carboniferous and the Middle-Lower Jurassic coal measures. The dominant ranges for δ13C1, δ13C2, δ13C3 and δ13C4 values in the Upper Paleozoic trapped gases are -35‰ to -32‰, -28‰ to -24‰, -27‰ to -23‰, and -23.5‰ to -22‰, respectively. The δ13CiC4 value is higher than that of the δ13CnC4. ③ The 3He/4He value is from n×10－8 to n×10－7 suggesting crustal origin. The CH4/3He value is from n× 1010 to n×1011 showing that the CH4 is of organic origin.
  • Origin and identification of natural gases
    SONG Yan and XU Yongchang
    , 2005, 32(4): 1138-0.
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    In the past 20 years, many researchers were engaged in tackling the key problems about natural gases, and brought about the theory and methods on origins and identification marks of natural gases. The natural gases include organic gases, inorganic gases and hybrid gases according to their origins. Gases of organic origin can be subdivided into biogenic, biogenic-thermal catalyzed, pyrogenic, and cracked gases, and can also be subdivided into coal derived gases and petroliferous gases according to the types of parent material. Coal derived gases include coal derived pyrogenic gases and coal derived cracked gases, which play a dominant role in natural gas resources. Petroliferous gases mainly refer to the associated gas of crude oil, including petroliferous pyrogenic gases and petroliferous cracked gases. Inorganic gases give priority to CO2, including petrochemistry gases and mantle derived gases. Hybrid gases are the mixture of gases from two or more origins: mixture of gases generated during different thermal evolution stages from the same source rock; mixture of gases generated from different source rocks; and mixture of inorganic gas and organic gas. The identification marks in common use for genetic types of natural gases mainly refer to the composition of natural gas, carbon isotopic composition of alkane and CO2, and parameters of light hydrocarbon. The carbon isotopic compositions are the most efficient tool and widely applied in gas typing.
  • Bio-thermocatalytic transitional zone gases
    LIU Wenhui and XU Yongchang
    , 2005, 32(4): 1139-0.
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    The proposition, development and research situation of the theory of bio-thermocatalytic transitional zone gases (BTTZG) are comprehensively introduced, suggesting that the gases are mainly composed of methane formed under the external agents at the specific stage between the end of biochemical processes and the onset of thermocatalysis. The corresponding burial depths range from 1500m to 2500m or even 3000m, the δ13C1 values range from －60‰ to －45‰, and Ro values range from 0.3% to 0.6%. The evolution model and formation mechanism of bio-thermocatalytic transitional zone gases are summarized from several aspects such as tectonic setting of the basin, sedimentary and diagenetic characteristics, organic matter composition, early evolution, hydrocarbon generation process, de-grouping and condensation reaction under the control of mechanochemistry produced by extremely active structural stress and clay mineral catalysis. According to the relationship between δ13C1 and C1/(C1-C5), BTTZG can be divided into 4 types: low-evolution and migration type; typical BTTZG; remained type; and the bio-reformed or multiple origin type. The geological and geochemical indicators are identified and the potential BTTZG resources of different kinds of oil-bearing basins in China are prospected.
  • Reservoir formation and resource potential of biogenic-low maturity gases in China
    ZHANG Ying; LI Jian and HU Chaoyuan
    , 2005, 32(4): 1140-0.
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    According to the literature statistics, biogenic-low maturity gases account for 14.5% of the natural gas reserves in the world. The formation and distribution of biogenic-low maturity gas reservoirs are characterized by the following facts. The gas reservoirs are close to the source rocks. The organic matters are mainly humus, and conserved well. The sedimentary basins developed in the near era with large subsidence and reducing water conditions are favorable for the generation of biogenic gases. And the cold weather and subsaline aqueous medium condition is favorable for the conservation of organic matters. Biogenic-low maturity gas reservoirs prefer to develop in the areas with relatively quiet tectonic movement, stable cap rock and few unconformity surfaces. Paleo-uplifts and syndeposit structures are the best ones among multi-types of gas reservoir traps. The source-reservoir-cap combinations in delta-offshore and shallow lake areas are favorable for the formation of biogenic-low maturity gas reservoirs. Comparing the geologic conditions in China with those in other countries in the world, the paper predicts that the biogenic-low maturity gas resources are about 6 trillion cubic meters in China. The exploration of the 4 biogenic-low maturity gas fields in China suggests that the great resource potential of biogenic-low maturity gas exists in the Mesozoic and Cenozoic continental sedimentary basins.
  • Origin, migration and accumulation of CO2 in East China and offshore shelf basins
    HE Jiaxiong; XIA Bin; LIU Baoming and ZHANG Shulin
    , 2005, 32(4): 1141-0.
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    Based on the geological and geochemical data of the CO2 reservoirs and high CO2 content oil/gas reservoirs discovered in east China and offshore shelf basins, CO2 is classified into 3 types as crust origin, crust-mantle origin and volcano-mantle origin. The CO2 gases from the CO2 reservoirs and high CO2 content oil/gas reservoirs in onshere fault basins in east China, East China Sea Basin, East Qiongdongnan Basin and Pearl River Mouth Basin are all of typical volcano-mantle origin, the gas sources are the CO2 produced by mantle volcano activities, and the gas migration and accumulation were controlled by mantle volcano activities and the gas channeling of the large faults connecting deep gas sources. The CO2 gases from the CO2 reservoirs and high CO2 content oil/gas reservoirs in the Yinggehai Basin are of crust origin and crust-mantle origin which were controlled by the local up invasion of the mud diapir hot fluid in multi blocks and zones, and by the physical-chemical mechanism of thick marine calcareous sandstone and mudstone. According to the regularities of the migration and distribution of gases from different origins, the gas sources may be traced, the migration and distribution of natural gas, especial CO2, be analyzed and predicted,and the CO2 resources potential be evaluated, and these provide foundation for decision making in natural gas exploration.
  • Natural gas exploration and development situation in Ordos Basin, NW China
    MA Xinhua
    , 2005, 32(4): 1142-0.
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    The perspective reserves in Ordos Basin are more than 10×1012m3. Since 1989, 5 gas fields, Jingbian, Yunlin, Wushenqi,Sulige and Daniudi Gas Fields, have been discovered successively. The proven natural gas reserves reach 1.2×1012m3. At present, the natural gas exploration in the Ordos basin has come into a rapidly expanding period, and the average annual increase of the proven gas reserves has been more than 2000×108m3 for the latest 4 years. Jingbian Gas Field can keep an annual output of 54×108m3 until 2008, with a decline rate of 12% in the late stable production period. South Yunlin Gas Field, with a better capability of stable production, can keep an annual output of 20×108m3 until 2014. The undeveloped Sulige Gas Field, with a low well production and a high decline rate, can establish an annual output capability of 10×108m3 in the near future. The east Jingbian Buried Platform, the circumference of Yunlin Gas Field, and the Zizhou-Qingjian zone are the reserves upgrading areas. Fugu-Jiaxian, Yichuan-Huanglong, the southwest side of Jingbian Gas Field and the bruchfalten zone on the west edge of the basin are the main new areas for reserves and production increase. The new gain of proven reserves in the reserves upgrading areas and the 4 new areas can reach 5000×108-6000×108m3, which lays the foundations for the 135×108-150×108m3 annual output in 2010
  • Natural gas accumulation in the Upper Paleozoic of Ordos Basin, China
    LI Jian; LUO Xia; SHAN Xiuqin; MA Chenghua; HU Guoyi; YAN Qituan; LIU Ruie and CHEN Honghan
    , 2005, 32(4): 1143-0.
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    The natural gas pools developed within the Upper Paleozoic of Ordos Basin are of low porosity, low permeability and low pressure. The gas accumulation characters and processes were analyzed through the study of fluid inclusion homogeneous temperature, fluid inclusion laser-Raman spectrum, bitumen distribution and genesis, and rock slices, together with the experimental data of the composition of the natural gases, light hydrocarbons from C5 to C8 and individual carbon isotope. Three gas plays were identified as inside source play, P1s2-C3t; top source play, P1s1-P1x8; and outside source play, P2s. Four gas pool-forming stages developed in Upper Paleozoic, including CO2 injection, light liquid hydrocarbon injection, extensive gases injection and the dynastic stage between the gain from coal-absorbed gas and the loss from cumulative natural gas. The accumulation processes and key factors of different types of gas pools were also studied.
  • Reservoir prediction of Feixianguan Formation in Puguang Gas Field, Northeast Sichuan Province
    MA Yongsheng; GUO Xusheng and FAN Rui
    , 2005, 32(4): 1144-0.
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    The Puguang Gas Field with reserves of over 100 billion cubic meters is the first giant one ever found in the carbonate rocks in China. The reservoir seismic response features were determined based on the analysis of the geological characters, accurate reservoir calibration, geological reservoir modeling and forward technology. A series of technologies for predicting oolite reservoir of Feixianguan Formation in the Puguang Gas Field were developed according to the analysis of favorable facies belts, seismic attributes and seismic constrained inversion. Based on these, seven wells were deployed.Among them,the finished Well Puguang 4 yields a high gas production and confirms the above prediction.
  • Relationship between palaeoenvironment and the distribution of H2S in Feixianguan Formation, NE Sichuan Province
    ZHU Guangyou; ZHANG Shuichang and LIANG Yingbo
    , 2005, 32(4): 1145-0.
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    The H2S gases produced from Feixianguan Formation (T1f), NE Sichuan Province, are generated from TSR origin. The research of the paleoenvironment such as distribution of gypsiferous rocks, gas sources and reservoir temperature, and reservoir formation conditions demonstates that ample gas sources and high reservoir temperature are the basic conditions for TSR, and the distribution of the gypsiferous rocks is the key controlling factor of the H2S formation and distribution. The differences of sedimentary palaeoenvironments in the eastern and western sides of the Kaijiang-Liangping trough result in the development of thin gypsiferous rocks within oolitic reservoirs to the east of the trough, and thus cause the formation of giant gas fields with a high H2S content. Gypsiferous rocks don't develop in the reservoirs to the west of the trough, thus the natural gases contain little or no H2S because of the lack of sulfur sources. The period from mid-Jurassic to Late Cretaceous is a period with the highest paleotemperature （120-180℃） for T1f in NE Sichuan Province, and also the most important period for TSR reaction. The Himalayan orogeny caused the uplift and erosion of NE Sichuan area, the reservoir temperature fell to less than 120℃ and the TSR ended. Thus, the H2S gases in T1f are conserved from mid-Jurassic to Cretaceous, their formation and distribution are closely related to the distribution of gypsiferous rocks, while irrelevant to the gas sources.
  • Geochemistry, origin and distribution of natural gases in Tarim Basin, NW China
    QIN Shengfei; LI Xianqi; XIAO Zhongyao; LI Mei and ZHANG Qiucha
    , 2005, 32(4): 1146-0.
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    The natural gases in Tarim Basin are mainly distributed in the foreland and platform areas. They are coal-formed and oil type and the proved natural gases are mainly coal-formed. Over 83% of the proved gases in Tarim Basin lies in the Central-Asia coal-formed gas accumulation domain. All the gas pools are distributed along the fractured belts. The fractures are generated by tectonic movements, and they serve as pathways for the gas migration. The tectonic-generated fault interrelated drapes provide excellent traps for the gas accumulation. The gas reservoirs experienced multi-period gas accumulation, but the late gas accumulation was much important for the gas pool formation. The latest gas accumulation happened during the late Weixishan period. Compared with the Jurassic coal measures in the east Tarim Basin, the coal measures in Kuche Depression has a higher gas generation rate, which is favorable for the large-middle-sized gas reservoir formation.
  • Terrestrial heat flow distribution in Kuqa foreland basin, Tarim, NW China
    ANG Liangshu; LI Cheng; LIU Shaowen; LI Hua; XU Mingjie; YU Dayong; JIA Chengzao and WEI Guoqi
    , 2005, 32(4): 1147-0.
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    Forty-five samples taken from 53 wells in the Kuqa foreland basin, north Tarim Basin, were selected for thermal conductivity measurement in laboratory, and the original thermal conductivity and formation thermal conductivity column were obtained based on the correction of temperature and porosity. Fifty-two heat flow values and their distribution were calculated based on the heat conduction theory and thermal resistance method.The Kuqa foreland basin is a low-heat-flow cold basin, the heat flow values of the tectonic units in the basin are 40-50 mW/m2, which are lower than that in other Chinese middle and large sized basins. The mountain front belt, including Yiqikelike, Dawanqi and Kela areas, has relatively high heat flow values and is the high heat flow belt in the cold basin and also a high gas production zone. In the south area, the heat flow decreases gradually from east to west. The heat flow distribution is determined by the lithosphere flexuring and fast subsiding during the Cenozoic tectonic evolution when intensive basin-mountain coupling occurred between Tarim Basin and Tianshan because of the far distance collision of the India and Eurasian Plates.
  • Formation mechanism, distribution feature and exploration prospect of the Quaternary biogenic gas in Qaidam Basin, NW China
    WEI Guoqi; LIU Delai; ZHANG Ying; LI Benliang; HU Guoyi and LI Jian
    , 2005, 32(4): 1149-0.
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    The formation mechanism and distribution of the Quaternary biogenic gas fields in Qaidam Basin is studied based on the biogenic gas generation, migration mode and cap-rock sealing mechanism.The biogenic gas simulation experiments suggest that the conversion rate of some kinds of original organic matters may reach over 85%. Although the residual TOC (total organic carbon) values of the Quaternary source rocks in Qaidam Basin are only about 0.3%, but giant biogenic gas fields could still be formed. The biogenic gases in the Sanhu area, central to eastern Qaidam Basin, migrated laterally by water-dissolving phase. The biogenic gases generated in the southern side and deep section of the basin were dissolved in formation brine and migrated from south to north. Biogenic gases were separated from the formation brine and then trapped in free phase through the vertical migration because of the shallower buried depth and higher formation brine salinity. Three kinds of sealing mechanism coexist in the north slope of Qaidam Basin: physical property sealing, saturated brine sealing and dynamic sealing. The Quaternary biogenic gas reservoir in Qaidam Basin is provided with favorable conditions. The north slope of the Sanhu area is still a key play target for biogenic gases in future, and the eastern Chaerhan area and deep zone of the north slope in Sanhu area are potential play targets.
  • Advances in biogenic gas studies and play strategies
    ZHANG Shuichang; ZHAO Wenzhi; LI Xianqi; HUANG Haiping; SU Aiguo and SHUAI Yanhua
    , 2005, 32(4): 1150-0.
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    Biogenic gas is an important end-product of methanogenesis in an anoxic environment. Methanogenesis mainly occurs through acetate fermentation and CO2 reduction. Because those methanogens obtain carbon and energy sources mainly from organic and inorganic carbons dissolved in native water, the type and abundance of organic matters in the sediments are not important for the formation of biogenic gases, thus the evaluation system for biogenic gas source rocks should be re-built. Exploration strategies for biogenic gases are analyzed based on the conclusion of the favorable geologic conditions for the biogenic gas formation. The keys of the play strategy are to recognize the process of biogenic gas accumulation and to build an appropriate evaluation method. Through synthesizing the geochemical, geological, and hydrological information, the targets could be efficiently predicted.
  • Natural gas accumulation and geochemical characteristics in Yinggehai-Qiongdongnan Basin, South China Sea
    DING Weiwei; PANG Yanming and HU Anping
    , 2005, 32(4): 1151-0.
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    The accumulating conditions and geochemical characteristics of the natural gas in Yinggehai-Qiongdongnan Basin were studied, which disclosed that the natural gas accumulation was favorable in the basin. The high-temperature environment accelerates the thermal evolution of the organic matters and shortens the maturation period of the source rocks. The reservoir-cap combination is desirable in that the porous reservoir benefits the gases reserving and the overpressured cap provides excellent sealing ability. Multi-types of traps develop in the basin. Tectonic activities open new faults as pathways for the natural gas migration. And the source rocks expel gas in late period, which prevents the gas field from depletion due to long-term diffusion. Isotopic compositions show that the gases in Yinggehai-Qiongdongnan Basin are generally coal gases with heavy alkane carbon isotopic compositions. Some biogenetic gases exist in the natural gases of Yinggehai Basin due to the episodic injection of hydrocarbon fluids. The CO2 gas in Yinggehai Basin is from organic crust origin, inorganic crust origin, and crust-mantle origin. The CO2 gas in Qiongdongnan Basin is of inorganic origin as crust origin and mantle origin.
  • Accumulation and distribution of natural gases in Xihu Sag, East China Sea Basin
    TAO Shizhen and ZOU Caineng
    , 2005, 32(4): 1152-0.
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    The geological conditions, geochemical characteristics, enrichment factors, distributing and accumulative belt of the natural gases in Xihu Sag, East China Sea Basin, are systematically studied based on plenty of exploration achievements in recent years. The key controlling factors of gas pool accumulation in the source rock(i.e.Pinghu Formation) are reservoir stratum, trap and accumulative condition. The controlling factors of natural gas pools formed above the source rock of Pinghu Formation(i.e. in Huagang Formation) are gas source faulting, reservoir stratum and trap condition. The enrichment and high yield of the natural gases is due to the following 4 factors: ① Four sets of favorable hydrocarbon source rocks provide enough hydrocarbons, and the hydrocarbon generation and expelling match well with the trap formation in time and space; ②Three favorable reservoirs exist in advantageous source-reservoir assemblage;③ The interlayer of sandstones and mudstones provides with a favorable preservative condition; ④ Fault activation and seal match hydrocarbon-expelling and reservoir formation. Vertically,the condensate oil reservoir is distributed in the upper stratum, and the gas-condensate is distributed in the lower stratum. Condensate oil-gas is luxuriant in the west sag, and is meager in the east sag; luxuriant in the south, and meager in the north.According to the systematic analysis of the oil-gas forming conditions,3 play zones are divided in Xihu Sag. Condensate oil-gas in hydrocarbon source stratum is rich in the west slope of the hydrocarbon-generating sag, and the play project for condensate oil should be performed in the slope of the sag. Condensate gas above hydrocarbon source stratum is rich in the bulge of the sag and the play project for condensate gas should be performed in the center bulge of the sag.
  • Composition and origin of natural gases in central Bohai Sea area, China
    WEN Zhigang; TANG Youjun; SONG Huanxin; XU Yaohui and LI Fuping
    , 2005, 32(4): 1153-0.
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    The natural gases discovered in the central Bohai Sea area are mainly composed of hydrocarbon gases, of which the gases in the Paleogene and older reservoirs are wet gases, while those in the Neogene are dry gases. The carbon isotopic compositions of the methane and ethane in the gases are greatly different.The methane carbon isotopic composition of the gases in the BZ28-1 structure and the ethane carbon isotopic composition of the gases in the QHD30-1 structure have the heaviest values, respectively. The hydrocarbon gases are of organic origin and are divided as oil type gas, coal derived gas and mixed gas with the third type being the major part.
  • Genesis and accumulation of non-oil-type natural gases in Huanghua Depression, Dagang Oilfield
    YANG Chiyin
    , 2005, 32(4): 1154-0.
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    Besides the conventional oil-type gases, many other types of gases have been found in Huanghua Depression. The rich condensate oils and gases found in Banqiao Sag are generated from terrigenous organic matters that have been strongly reformed and changed by microorganism. The natural gases in Qianmiqiao buried hill are heavy hydrocarbons with abnormal heavy carbon isotopic composition, which were generated from trimellitic-humic organic matters during the highly-matured stage in the 3rd Member of Paleogene Shahejie Formation. The humic organic matters in Carboniferous-Permian coal-bearing strata in the Kongnan area are rich in effective hydrocarbon generating macerals, and coal derived gas reservoirs have been found in the Ordovician Wumaying structure. The collective character of the gases accumulation is that their entrapment is all related to extrusion stress. Both the gas genesis and local compression structure should be studied.
  • Gas genesis and accumulation history of Wenliu gas pool in Dongpu Sag, Center China
    XU Huazheng and ZHOU Xinke
    , 2005, 32(4): 1155-0.
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    Wenliu structure is an anticline caused by salt-accumulation in the background of center mole track in Dongpu Sag with the trap extent enlarged by salt-slumping in the wings. The reservoir is thick with gentle occurrence and high gas abundance. The geochemical characteristics of the gases reveal that it is a typical coal-derived gas reservoir formed from pre-Mesozoic source rocks and accumulated in Cenozoic pool. The first hydrocarbon generating process occurred after Early-Middle Triassic sedimentation. According to the Ro values and apatite fission track, the paleo-burial depth of the coal formation was about 3500m at that time, the palaeo-temperature was 118℃, and the Ro reached 0.85%. Then after 180 million years of interruption caused by uplift and erosion, the coal formation began secondary hydrocarbon generating in the Eogene rifting period because of the increase of burial depth. The generation peak appeared after Dongying Formation was deposited. The later uplift and erosion during Dongying Movement accelerated the diffusing, migration and accumulation of the coal derived gases. The high concentration and pressure formed the main power for the secondary migration, and the fracture-fault system acted as the major channels.
  • Accumulation dynamics and distribution of litho-stratigraphic reservoirs in South Songliao Basin
    ZOU Caineng; JIA Chengzao; ZHAO Wenzhi; TAO Shizhen; GU Zhidong; HOU Qijun; ZHAO Zhanyin and SONG Lizhong
    , 2005, 32(4): 1156-0.
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    According to the relationship of the vertical positions between source rocks and reservoirs,the lithostratigraphic reservoirs were divided into 3 types as below-source, in-source and above-source. From the viewpoint of fluid dynamics, the relationship of the pressure energy and potential energy between source and reservoir in different lithostratigraphic reservoirs was studied based on the analysis of fluid potential composition characteristics. The pressure and potential differences, which constitute the fluid potential, were analyzed,and 3 driving mechanisms were proposed as below-source pressure difference driving, in-source fluid pressure difference driving and above-source potential difference driving. Also presented are petroleum accumulation dynamics and oil-gas migration-accumulation mechanisms of below-source, in-source and above-source lithostratigraphic reservoirs in the South Songliao Basin, and the controlling factors of the petroleum accumulation and distribution for the 3 types of reservoirs.
  • Contribution of various coal measures source rocks to oil and gas reservoir formation
    QIN Jianzhong; LI Zhiming and ZHANG Zhirong
    , 2005, 32(4): 1157-0.
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    New geochemical technologies and methods are used to study the main coal measures source rocks of Carboniferous-Permian Formations in NE Jizhong Depression and Jurassic Formations in the north margin of Qaidam Basin. The oil and gas source correlation, comprehensive evaluation and hydrocarbon generation quantitity calculation of various source rocks are studied by systemically summarizing the analysis data of source rocks and oil and gas samples (total 6629). The results show that the condensate oils or light oils of Suqiao Oil/Gas Fields in Jizhong Depression were mainly derived from the secondary hydrocarbon generation and expelling of the liptinite-bearing coals and carbonaceous mudstones of C2b-P1s Formations, while the oils of Lenghu Oilfield in the north margin of Qaidam Basin are mainly derived from the Lower Jurassic shallow-deep lake facies mudstones, and the generated and expelled oil and gas were also mainly from lake facies mudstones. The hydrocarbon generation abilities of dark mudstones, carbonaceous mudstones and coal in coal-bearing environments are quite different, and their organic matter types and macerals vary with the changing of sedimentary facies or sub-facies. The hydrocarbon generation abilities of coals and carbonaceous mudstones are better than those of dark mudstones when the coal measures source rocks deposited in littoral (lake) paludal facies, whereas the hydrocarbon generation abilities of dark mudstones are better than those of coals when the coal measures source rocks deposited in deep-shallow lake (or marine) paludal facies.
  • Origin and appraisal of coal derived gas and oil
    LIU Dehan; FU Jiamo; XIAO Xianming; CHEN Deyu; GENG Ansong; SUN Yongge and WANG Yunpeng
    , 2005, 32(4): 1158-0.
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    The exinites and microexinites in coals were quantitatively analyzed under fluorescent and con-focal laser microscopes,the 13C NMR was performed on the compositions of the coals and the coal-bearing formations, and simulating experiments of maceral thermal evolution were carried out. According to the results, the control of the contents of methyl,α methylene and methine in hydrogen-rich ingredients and macromolecular structures of the coals on both the liquid and gaseous coal derived hydrocarbons were discussed, and the evaluation criteria for the gas and oil derived from bituminous coals at low thermal evolution stage were proposed. The majority of the coal-bearing basins in China are predominated by humolites rich in vitrinites and inertinites, which indicates that coal derived gas should be the exploration target in coal-bearing basins. Only a few coal-bearing basins with widely distributed coal layers rich in exinites and micrioexinites, such as the Turpan-Hami Basin, may be prospects for coal derived oil.
  • Relationship between coal depositional modes and hydrocarbon generation of the Early Permian Taiyuan and Shanxi Formation in Huabei Platform
    CHENG Keming; XIONG Ying; MA Liyuan and LI Xinjing
    , 2005, 32(4): 1159-0.
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    In the eastern and central parts of North China Platform and Ordos Basin, the coal series in Taiyuan Formation are formed in a coal depositional environment of a transgressive system tract while those in Shanxi Formation is deposited mainly in a terrestrial delta coal-forming environment of a highstand system tract. Coals formed in the two depositional environments are quite different in organic-geochemical features, such as sulfur content, sulfur molecular configurations and macerals. Sulfur is more abundant in Taiyuan Formation than in Shanxi Formation. In Taiyuan Formation, sulfur is mainly in the form of pyrite sulfur, while in Shanxi Formation sulfur is chiefly in the form of sulfate. The coal macerals in the Taiyuan Formation are of high average vitrinite content, mainly desmocollinite, and low average inertinite content, while that in the Shanxi Foramtion are of lower average vitrinite content and much lower desmocollinite content, but of higher inertinite content. The Taiyuan Formation coal is high in GI (Gelification Index) but low in TPI (Texture Preservation Index), while the Shanxi Formation coal is lower in GI but higher in TPI. The transgressive Taiyuan Formation coal series should be the best hydrocarbon-generating deposit in the studied area.
  • Some issues about evaluation on high-over matured gas source rocks
    LIAO Yongsheng
    , 2005, 32(4): 1160-0.
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    The lower total organic carbon (TOC) limit for primary successive hydrocarbon generating source rocks, carbonate rocks or mudstones, gas source rocks or oil source rocks, is 0.5%. However,the value is not suitable for the secondary hydrocarbon generation in poly-cycle residual basins. The calculating method of the lower TOC for secondary hydrocarbon generation source rocks of different maturity is established according to the thermal simulation experiments.The method for identifying gas source rocks is studied using the natural gas generation-accumulatiom-dissipation dynamic balance theory. In the gas source rocks with Ro values over 2.5%, the asphaltines and oils have become gas sources due to cracking. The distribution of secondary gas reservoirs is determined by the distribution of paleo-reservoirs. The formation and destruction of water-dissolved gas reservoirs happened at the same time as that of gas reservoirs. The early preservation of water-dissolved gas is very important for its accumulation.
  • Kinetic method for determining the main gas-generation period of marine organic matters and its application
    WANG Yunpeng; ZHAO Changyi; WANG Zhaoyun; WANG Hongjun; ZOU Yanrong; LIU Jinzhong; ZHAO Wenzhi; GENG Ansong; LIU Dehan and LU Jialan
    , 2005, 32(4): 1162-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The natural gas fields and generation rates in the geological history are calculated by use of kinetic methods and the acquired kinetic parameters of typical marine organic matters (oil and kerogen) of China and other areas in the world, and the maturity is calculated by Easy Ro method. The coupling of the two results shows that Ro is 1.4%-2.4% during the main gas-generation period of typeⅠkerogen, Ro is 1.5%-3.0% during the main gas-generation period of type Ⅱ kerogen, and Ro is 1.6%-3.2% during the main gas-generation period of oil cracking gas. Taking the southwestern area of Tarim Basin as an example,the influences of the openness of simulation system on the main gas-generation period, and the "dead line" of natural gas generation are also discussed. The results indicate that the openness of simulation system has a definite influence on the kenetic parameters calculation of the main gas-generation period. Ro is 1.4%-3.1% during the main gas-generation period of type Ⅱ kerogen in the open system, which is earlier than that in the closed system. The “dead line” of natural gas generation is determined as Ro is 3.5% for type I kerogen, Ro is 4.4%-4.5% for type Ⅱ kerogen and Ro is 4.6% for marine oil.
  • Organic matter evolution and oil-gas resource in deep earth
    WANG Xianbin; TUO Jincai; ZHOU Shixin; LI Zhenxi and YAN Hong
    , 2005, 32(4): 1163-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Based on the unconventional theory of oil-gas and abiogenic gas genesis, two basic processes are involved in the organic matter evolution in the deep earth: the conversion from the primary complicated organic matter to the simple organic matter through thermal decomposition, and the formation of organic matter with higher molecular weight from primary low-molecular carbon-bearing substances (CO, CO2, etc) through polymerization. The investigations show that the oil and gas in the deep earth still possess a high thermal stability and the pressure that retards the maturation and decomposition of organic matter provides the deep source rock with a good hydrocarbon generating potential. The hydrocarbon formation of organic matter is closely affiliated with the exotic hydrogen which enhances the conversion rate of hydrocarbon and retards the graphitization of organic matter. Water is an essential source of hydrogen in the hydrocarbon formation and evolution of organic matter, and trace transitional metal elements play an important catalytic role in the hydrocarbon formation of organic matter. The differences of the two hydrocarbon-forming mechanisms bring about different dynamic fractionation effects of carbon and hydrogen isotopes and are characterised by a wide divergence in the specific isotopic compositions. The deep oil-gas and abiogenic gas are of a broad prospect of resources.
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