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Differences and controlling factors of lithofacies assemblages of Cenozoic lacustrine microbial carbonate rocks in western Qaidam Basin
WANG Jiangong, LI Jiangtao, LI Xiang, GAO Yanfang, ZHANG Ping, SUN Xiujian, BAI Yadong, ZUO Mingtao
2023, Vol.35(3): 1–17
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Hydrocarbon accumulation characteristics of Mesozoic Lufeng 7-9 buried hill in Lufeng 13 subsag transition zone，Pearl River Mouth Basin
HE Yanbing, XIAO Zhangbo, ZHENG Yangdi, LIU Junyi, YI Hao, ZHAO Qing, ZHANG Yuexia, HE Yong
2023, Vol.35(3): 18–28
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Reservoir characteristics and main controlling factors of upper member of Paleogene Xiaganchaigou Formation in Nanyishan area， northwestern Qaidam Basin
ZHANG Zhenhua, ZHANG Xiaojun, ZHONG Dakang, GOU Yingchun, ZHANG Shiming
2023, Vol.35(3): 29–39
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1449 )
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Nonlinear seepage characteristics of shale oil reservoirs of the third member of Paleogene Shahejie Formation in Qikou Sag，Bohai Bay Basin
ZENG Xu, BIAN Congsheng, SHEN Rui, ZHOU Kejia, LIU Wei, ZHOU Suyan, WANG Xiaoluan
2023, Vol.35(3): 40–50
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1457 )
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Geochemical characteristics and formation environment of source rocks of Triassic Chang 7 member in northern Pingliang area，Ordos Basin
XUE Nan, SHAO Xiaozhou, ZHU Guangyou, ZHANG Wenxuan, QI Yalin, ZHANG Xiaolei, OUYANG Siqi, WANG Shumin
2023, Vol.35(3): 51–65
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1379 )
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309
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Characteristics and genesis of Upper Triassic Chang 8 reservoir with low oil saturation in northern Pingliang area， Ordos Basin
BAI Yang, ZHANG Xiaolei, GANG Wenzhe, ZHANG Zhongyi, YANG Shangru, PANG Jinlian, CAO Jingjing, HOU Yunchao
2023, Vol.35(3): 66–75
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1425 )
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Hydrocarbon accumulation models and exploration potential of MesoCenozoic heavy oil in northern Melut Basin，South Sudan
XUE Luo, SHI Zhongsheng, MA Lun, ZHAO Yanjun, YUE Shijun, HONG Liang, WANG Lei, LEI Ming
2023, Vol.35(3): 76–85
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1398 )
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Characteristics and accumulation model of typical dolomite reservoirs in China
DU Jiangmin, LIU Boyuan, ZHANG Yi, JIA Zhiwei, FU Jiyou, LONG Pengyu, LUO Jinyang, SHENG Jun
2023, Vol.35(3): 86–98
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1454 )
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Development characteristics of FⅠ16 fault in Fuman oilfield of Tarim Basin and its influence on oil and gas distribution
SONG Xingguo, CHEN Shi, YANG Minghui, XIE Zhou, KANG Pengfei, LI Ting, CHEN Jiuzhou, PENG Zijun
2023, Vol.35(3): 99–109
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1379 )
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Hydrocarbon accumulation characteristics and favorable zones prediction in and under source of Paleozoic in Huanghua Depression，Bohai Bay Basin
YANG Runze, ZHAO Xianzheng, LIU Haitao, LI Hongjun, ZHAO Changyi, PU Xiugang
2023, Vol.35(3): 110–125
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1366 )
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Shale oil accumulation conditions of Permian Lucaogou Formation in Fukang fault zone，Junggar Basin
LIU Zhongquan, ZHAO Leqiang, ZENG Zhiping, TIAN Jijun, LI Zhengqiang, LUO Jinchang, HU Meiling
2023, Vol.35(3): 126–137
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Characteristics and main controlling factors of natural gas of CarboniferousPermian in western well Pen-1 sag，Junggar Basin
JIANG Mengya, WANG Jiangtao, LIU Longsong, LI Hui, CHEN Hailong, JIANG Zhongfa, WANG Xueyong, LIU Hailei
2023, Vol.35(3): 138–151
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Characteristics and reservoir accumulation model of Ordovician fault-controlled fractured-vuggy reservoirs in Shunbei oil and gas field，Tarim Basin
BU Xuqiang, WANG Laiyuan, ZHU Lianhua, HUANG Cheng, ZHU Xiuxiang
2023, Vol.35(3): 152–160
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Response characteristics and correction of LWD laterolog in anisotropic formations and deviated boreholes
LI Fengfeng, NI Xiaowei, XU Sihui, WEI Xinlu, LIU Diren
2023, Vol.35(3): 161–168
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Differences and controlling factors of lithofacies assemblages of Cenozoic lacustrine microbial carbonate rocks in western Qaidam Basin
WANG Jiangong, LI Jiangtao, LI Xiang, GAO Yanfang, ZHANG Ping, SUN Xiujian, BAI Yadong, ZUO Mingtao
2023, Vol.35(3): 1–17
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doi: https://doi.org/10.12108/yxyqc.20230301
Based on a large number of outcrops and core thin sections and analytical data，the petrological characteristics，microstructure，lithofacies assemblage，sedimentary environment and its controlling factors of Cenozoic saline lacustrine microbial carbonate rocks in western Qaidam Basin were studied. The results show that：（1）The lithofacies assemblage of microbial carbonate rocks in western Qaidam Basin can be divided into fan-controlled type and lake-controlled type due to the comprehensive influence of paleogeomorphology，sedimentary environment and terrigenous clastic supply. The fan-controlled lithofacies assemblage is mainly developed in the coastal environment at the edge of the lake，with large thickness and wide distribution，while the lake-controlled lithofacies assemblage is mainly developed in the basin margin slope area，fault terrace zone and shallow lakes in the basin， with small thickness and small distribution. The upper member of Paleogene Xiaganchaigou Formation is dominated by fan-controlled lithofacies assemblage，with relatively limited lake-controlled lithofacies assem-blage. Two types of lithofacies assemblages are developed in Neogene Xiayoushashan Formation.（2）The types and structural characteristics of microbial carbonate rocks in different lithofacies assemblages in the study area are quite different. Fan-controlled microbial carbonate rocks were formed in the lake transgression period. They were mainly deposited in a positive cycle，mainly consisting of thrombolites，and often stacked on thick massive glutenite. The microstructure is mainly composed of agglomerates（clots），spherules and aggregates，and the mineral composition is mainly sparry calcite. Lake-controlled microbial carbonate rocks can be developed during lake transgression and lake regression. Both positive and reverse cycle sediments are developed，and thrombolites，stromatolites and their symbiotic layers are developed，with relatively small scale，and most of them are inter-bedded with argillaceous carbonate rocks. The microstructure is more complex，and agglomerates（clots），pellets，aggregates and laminated structures are developed. The mineral composition is mainly calcite and dolomite，rich in terrigenous detritus and clay minerals，with obvious mixed sedimentation characteristics.（3）The formation of fan-controlled microbial carbonate rocks in the study area is mainly controlled by organic mineralization and chemical precipitation， while the formation of lake-controlled microbial carbonate rocks is affected by organic mineralization，chemical precipitation and physical sedimentation.
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Hydrocarbon accumulation characteristics of Mesozoic Lufeng 7-9 buried hill in Lufeng 13 subsag transition zone，Pearl River Mouth Basin
HE Yanbing, XIAO Zhangbo, ZHENG Yangdi, LIU Junyi, YI Hao, ZHAO Qing, ZHANG Yuexia, HE Yong
2023, Vol.35(3): 18–28
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doi: https://doi.org/10.12108/yxyqc.20230302
The oil and gas shows of Lufeng 7-9 buried hill in Lufeng 13 subsag transition zone of the Pearl River Mouth Basin show its great exploration potential. Based on the data of drilling，logging，borehole cores，thin sections and geochemistry，the hydrocarbon accumulation characteristics of Mesozoic Lufeng 7-9 buried hill in Lufeng 13 subsag transition zone of Pearl River Mouth Basin were studied. The results show that：（1）Two sets of high-quality source rocks are developed in Lufeng 13 subsag，namely，the upper Wenchang Formation and the fourth member of the lower Wenchang Formation，with the average TOC of 1.54% and 2.55%，respectively，and the organic matter is mainly typeⅡ1. Lufeng 7-9 buried hill is adjacent to high-quality source rocks，with the advantage of double source and wide window hydrocarbon supply.（2）Lufeng 7-9 buried hill trap was initially developed in the Mesozoic Cretaceous，finalized in the Paleogene，and the high point position was stable for a long time，which is conducive to the migration，accumulation and preservation of oil and gas.（3）Weathering zone and inner zone are vertically developed in Lufeng 7-9 buried hill. The brittle felsic minerals are conducive to the development of buried hill reservoirs. The paleogeomorphology controls the distribution of high-quality reservoirs in the weathering zone. The continuous activation of pre-existing faults is conducive to the development of reservoirs in inner zone.（4）The faults，unconformities and internal network fracture system constitute the main oil and gas migration channels of Lufeng 7-9 buried hill，and two hydrocarbon supply models of lateral sourcefault-unconformity and lateral source-fault-network fracture are developed.（5）Lufeng 7-9 buried hill is a late accumulation model with crude oil filling period of 0～13 Ma. The space-time coupling relationship between different accumulation elements is good. It is a late accumulation model of double-sag near-source and wide window hydrocarbon supply， fault-unconformity-network fracture combined transport.
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Reservoir characteristics and main controlling factors of upper member of Paleogene Xiaganchaigou Formation in Nanyishan area， northwestern Qaidam Basin
ZHANG Zhenhua, ZHANG Xiaojun, ZHONG Dakang, GOU Yingchun, ZHANG Shiming
2023, Vol.35(3): 29–39
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doi: https://doi.org/10.12108/yxyqc.20230303
By means of core observation，thin section identification and electron probe analysis，the reservoir characteristics and main controlling factors of the upper member of Paleogene Xiaganchaigou Formation（E32）in Nanyishan area of northwestern Qaidam Basin were studied. The results show that：（1）The reservoirs of E32 in Nanyishan area are characterized mixed sedimentation，dominated by carbonate rocks，with an average mass fraction of 42.6%，containing terrigenous clast，anhydrite and clay minerals，with the average mass fraction of 24.9%， 9.0% and 12.8%，respectively. The lithologies of the reservoirs are mainly limestone，dolomite and algal limestone，with an average volume fraction of 49.0%，12.0% and 6.0% respectively.（2）The reservoir porosity in the study ranges from 1.0% to 13.3%，with an average of 4.9%，and 92% of the samples have permeability less than 0.02 mD，indicating low porosity and ultra-low permeability. The pores are mainly dissolved pores and intercrystalline pores，and microfractures are developed，but they are often filled with cements，and the connectivity is poor. According to the pore throat radius，the throat can be divided into three types： medium throat，fine-medium throat and fine-micro throat，and the average pore throat radii are 0.350 μm，0.110 μm and 0.030 μm respectively，accounting for 15%，40% and 45% respectively.（3）The sedimentary subfacies in the study area is mainly shallow lacustrine to semi-deep lacustrine，which can be subdivided into four microfacies，namely，calcareous-dolomitic flat，algal mat，sand flat and mud flat. The development of reservoirs is closely related to sedimentary microfacies，of which the calcareous-dolomitic flat reservoir accounts for the largest proportion，accounting for 67% of the total thickness of the reservoir. High-quality reservoirs are developed in algal mat，and the thicker the algal limestone is，the better the physical properties of the reservoir are，while reservoir is hardly developed in mud flat.（4）The reservoirs in the study area are controlled by diagenesis and tectonism. Quasi-syngenetic dolomitization，dissolution and tectonism increased reservoir space and improved reservoir permeability，while cementation in the late sedimentary period has a destructive effect on the development of reservoir.
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Nonlinear seepage characteristics of shale oil reservoirs of the third member of Paleogene Shahejie Formation in Qikou Sag，Bohai Bay Basin
ZENG Xu, BIAN Congsheng, SHEN Rui, ZHOU Kejia, LIU Wei, ZHOU Suyan, WANG Xiaoluan
2023, Vol.35(3): 40–50
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doi: https://doi.org/10.12108/yxyqc.20230304
Through high-pressure mercury injection and low-temperature gas adsorption experiments， combined with nuclear magnetic resonance online detection system and displacement experiment，the seepage characteristics of shale oil reservoirs of the third member of Paleogene Shahejie Formation（Es3）in Qikou Sag， Bohai Bay Basin were studied. The results show that： （1）The micropores of the three lithofacies shales of the third member of Paleogene Shehejie Formation in Qikou Sag account for the largest proportion. Compared with massive mudstone，the medium and large pore throats with pore diameter greater than 100 nm in laminated and layered shale reservoirs are more developed，and the reservoir properties and seepage capacity are better.（2）The flowable oil that occurs in the large pore throats of shale reservoirs can be output effectively， but the oil in the small pore throats（less than 100 nm）is difficult to output even under a large pressure difference due to the large seepage resistance.（3）The seepage of shale oil in shale reservoir has the characteristics of start-up pressure gradient and nonlinear seepage，but there are great differences among different lithofacies. The laminated shale reservoir has the lowest pseudo start-up pressure gradient and the strongest seepage capacity，the layered shale reservoir has a certain seepage capacity，while the massive shale reservoir has the poorest seepage capacity. Under the same pressure gradient，the flow rate in the massive shale is only about 10% of that in laminated shale，and there is no natural productivity.
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Geochemical characteristics and formation environment of source rocks of Triassic Chang 7 member in northern Pingliang area，Ordos Basin
XUE Nan, SHAO Xiaozhou, ZHU Guangyou, ZHANG Wenxuan, QI Yalin, ZHANG Xiaolei, OUYANG Siqi, WANG Shumin
2023, Vol.35(3): 51–65
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doi: https://doi.org/10.12108/yxyqc.20230305
Through geochemical analysis of dark mudstone samples of Triassic Chang 7 member from 15 wells in northern Pingliang area，southwest margin of Ordos Basin，combined with logging interpretation results，the paleosedimentary environment was inferred，and the main controlling factors and development model of hydrocarbon source rocks were summarized. The results show that： （1）The organic matter abundance of Triassic Chang 7 source rocks in northern Pingliang area gradually decreased from bottom to top， with the highest organic matter abundance in Chang 73 sub-member，followed by Chang 72 sub-member， and the lowest in Chang 71 submember. The organic carbon mass fraction of the hydrocarbon source rock of Chang 73 sub-member is up to 12.4%， with great hydrocarbon generation potential. The organic matters are mainly typeⅠand type Ⅱ1. It is a set of good to high-quality lacustrine source rocks in mature stage.（2）The climate was moist and warm during the sedimentary period of Chang 73 sub-member in northern Pingliang area， and it was a terrestrial freshwater environment. High paleo-productivity and anoxic reduction water created favorable conditions for the growth， reproduction and preservation of organic matters.（3）Volcanic-hydrothermal source rocks are developed in Chang 73 submember in northern Pingliang area. Volcanic activity and hydrothermal deposition jointly affect the water environment of Chang 73 sub-member. The high paleo-productivity is the basis for the formation of large amounts of organic matters， and the anoxic reduction environment is the key factor for the complete preservation of organic matters.
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Characteristics and genesis of Upper Triassic Chang 8 reservoir with low oil saturation in northern Pingliang area， Ordos Basin
BAI Yang, ZHANG Xiaolei, GANG Wenzhe, ZHANG Zhongyi, YANG Shangru, PANG Jinlian, CAO Jingjing, HOU Yunchao
2023, Vol.35(3): 66–75
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doi: https://doi.org/10.12108/yxyqc.20230306
Through core physical property analysis， constant pressure mercury injection and nuclear magnetic resonance testing，combined with oil source and structure，the characteristics and genesis of Upper Triassic Chang 8 reservoir with low oil saturation in northern Pingliang area of Ordos Basin were analyzed. The results show that： （1）The oil saturation of Upper Triassic Chang 8 reservoir is generally less than 20%， while the water saturation is generally greater than 50%. It is a typical low oil saturation reservoir with low single well production and poor oil-water difference. The reservoir is sporadically distributed at the top of Chang 8 member.（2）Insufficient hydrocarbon supply is the fundamental reason for the low oil saturation of the reservoirs in the study area. It is an allochthonous oil reservoir in well M53 well，and the long distance of hydrocarbon supply leads to insufficient hydrocarbon supply. It is in-situ hydrocarbon accumulation in well Y80， and the small amount of hydrocarbon expulsion from in-situ source rocks results in insufficient oil and gas filling.（3） Affected by low-amplitude structures，vertical and lateral migration power is insufficient in well M53 well. The strong physical heterogeneity of the reservoirs in the whole area， the relatively developed micro pore throats in the pore structure， and the high percentage of bound water，resulted in low saturation after oil and gas displacement of movable water，which indirectly led to scattered distribution and low oil saturation of the reservoirs in northern Pingliang area.（4）The reservoirs with good physical property at the structural high point in the southwestern Shangxinzhuang area in M53 well area are important targets for the next step of increasing reserves and production.
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Hydrocarbon accumulation models and exploration potential of MesoCenozoic heavy oil in northern Melut Basin，South Sudan
XUE Luo, SHI Zhongsheng, MA Lun, ZHAO Yanjun, YUE Shijun, HONG Liang, WANG Lei, LEI Ming
2023, Vol.35(3): 76–85
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doi: https://doi.org/10.12108/yxyqc.20230307
There are various types of heavy oil reservoirs developed in northern Melut Basin， with broad prospects for exploration and development. Through oil-source correlation and hydrocarbon migration and accumulation simulation，the Meso-Cenozoic heavy oil reservoirs in northern Melut Basin were classified，and the accumulation models and main controlling factors of different formations of heavy oil reservoirs were analyzed. The results show that： （1）There are five types of heavy oil reservoirs developed in northern Melut Basin，including structurallithologic heavy oil reservoirs of Neogene Jimidi Formation， fault-block heavy oil reservoirs and stratigraphic unconformity heavy oil reservoirs of Paleogene Yabus Formation， up-dip pinch-out lithologic heavy oil reservoirs of Cretaceous Galhak Formation and fracture heavy oil reservoirs in buried hill.（2）The heavy oil reservoirs of Neogene Jimidi Formation are of secondary origin，with the reservoir accumulation characteristics of far-source faultunconformity migration， which is a structural-lithologic reservoir. Gandool，Dabass and Jammam areas are favorable for heavy oil accumulation.（3）The heavy oil reservoirs of Paleogene Yabus Formation are of secondary origin，of which the stratigraphic unconformity heavy oil reservoirs have limited exploration potential， and the faultblock heavy oil reservoir have the accumulation characteristics of far source fault and sand body step migration. The Jammam fault-step belt in the basin margin is a favorable area for heavy oil exploration. （4）The stratigraphiclithologic heavy oil reservoirs of Cretaceous Galhak Formation are of primary origin， which are mainly controlled by near-source immature to low-mature hydrocarbon source rocks. Braided river delta front at the high part of the sag slope is the main facies belt for the development of stratigraphic-lithologic heavy oil reservoir.
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Characteristics and accumulation model of typical dolomite reservoirs in China
DU Jiangmin, LIU Boyuan, ZHANG Yi, JIA Zhiwei, FU Jiyou, LONG Pengyu, LUO Jinyang, SHENG Jun
2023, Vol.35(3): 86–98
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doi: https://doi.org/10.12108/yxyqc.20230308
Through the review of the development characteristics of typical marine dolomite reservoirs and continental dolomite reservoirs in China， the characteristics and accumulation model of dolomite reservoirs were systematically summarized. The results show that： （1）Facies-controlled dolomite reservoirs are generally developed on the platform margin or marginal zone of intra-platform rift，and on the carbonate ramp. For example，several intraplatform rifts are developed in Sinian Dengying Formation in Tarim Basin，mound shoal dolomite reservoirs are developed around the rift，and argillaceous source rocks are filled in the rift，forming a good source-reservoir configuration.（2）The lithologies of Wumishan Formation of Mesoproterozoic Jixian System in North China Basin are mainly thick massive micritic dolostones，which are mainly of microbial origin. The reservoir quality is controlled by microbial sedimentation， structural fracturing since Indosinian and dissolution.（3）The fourth member of Sinian Dengying Formation in Gaoshiti-Moxi area of Sichuan Basin is developed with relatively high-quality dolomite reservoir with low porosity and ultra-low permeability，with an average porosity of 4.8% and an average permeability of 0.5 mD，mainly including micritic algal dolomite，crystalline dolomite and saddle dolomite. The main controlling factors for reservoir development include favorable facies belt， dolomitization and tectonism. （4）The continental dolomite reservoirs of Permian Lucaogou Formation in Junggar Basin，Cretaceous in Yin’ e Basin and Oligocene in Qaidam Basin，are generally relatively tight，with nano-micron dolomite intercrystalline pores as the main reservoir space，with porosity up to 10%， but most of the permeability less than 0.1 mD.（5）Most continental dolomites are self-generation and self-reservoir oil and gas reservoirs. They are reservoir rocks and have oil-generating capacity. The abundance and maturity of organic matters are low，but the dispersed soluble organic matters in the source rocks can generate hydrocarbons in the low maturity stage， and have high liquid hydrocarbon yield in the saline environment.（6）The continental dolomite reservoirs are mostly large continuous unconventional oil and gas reservoirs，which are widely distributed in depressions or sedimentary centers in a large scale，and together with the structural reservoirs，lithologic reservoirs and stratigraphic reservoirs formed in the high part of the structure and slope area outside the source， form a widely distributed oil and gas field group.
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Development characteristics of FⅠ16 fault in Fuman oilfield of Tarim Basin and its influence on oil and gas distribution
SONG Xingguo, CHEN Shi, YANG Minghui, XIE Zhou, KANG Pengfei, LI Ting, CHEN Jiuzhou, PENG Zijun
2023, Vol.35(3): 99–109
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doi: https://doi.org/10.12108/yxyqc.20230309
The data of 3D seismic，multi-layer coherence analysis，amplitude change rate，reservoir core analysis and oil and gas distribution were used to analyze the spatial distribution characteristics， activity intensity and stages of FⅠ16 fault in Fuman oilfield of Tarim Basin， and the control effects of fault on reservoir and accumulation were discussed. The results show that： （1）The FⅠ16 fault in Fuman oilfield has the characteristics of plane segmentation and vertical stratification. On plane， it can be divided into three segments from north to south，the northern segment spreads along NE 10° and develops horsetail-like structure，the middle segment spreads along NE 20° and is in the transition position of fault strike，mainly develops left-order oblique row，and the southern segment spreads along NE 30° with strong linear extension characteristics， mainly right-order oblique sequence. Vertically， it can be divided into deep structural deformation layer below the bottom of Upper Cambrian（TЄ3）and the shallow structural deformation layer of the bottom of Upper Cambrian to the top of Ordovician Yijianfang Formation （TO3t）. The deep fault activity is weak， the branch is less developed， only the local flower structure is developed. While the shallow fault activity is strong，the flower structure is generally developed，and there exists the phenomenon of “multi-flower superposition” and stratigraphic co-deposition in the fracture zone vertically.（2）The activities of FⅠ16 fault in Fuman oilfield can be divided into two stages： early Caledonian and middle Caledonian. The middle Caledonian is the main active stage，with stronger intensity and multi-episode activation characteristics，and the activity intensity is strong in the north and weak in the south on plane， showing the characteristics of shallow upper arch and deep decline in the vertical direction，and the shallow fault activity is stronger.（3）The reservoirs in the study area are mainly fault-controlled fracture-cave reservoirs，controlled by fault fragmentation， distributed in a strip along the FⅠ16 fault zone on plane，and superimposed deep and shallow layers vertically. Affected by the distribution characteristics of Middle Cambrian gypsum salt rocks，the FⅠ16 fault zone has the oil and gas distribution characteristics of “south oil and north gas”.
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Hydrocarbon accumulation characteristics and favorable zones prediction in and under source of Paleozoic in Huanghua Depression，Bohai Bay Basin
YANG Runze, ZHAO Xianzheng, LIU Haitao, LI Hongjun, ZHAO Changyi, PU Xiugang
2023, Vol.35(3): 110–125
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doi: https://doi.org/10.12108/yxyqc.20230310
Coal measure source rocks are the main source rocks of Paleozoic petroleum system in Huanghua Depression，Bohai Bay Basin. Hydrocarbon accumulation mechanism and accumulation process of the in-source and under-source reservoirs are not clear. Based on logging，well log and seismic data，combined with geochemical tests of source rocks，reservoir analysis and testing，inclusion tests，physical simulation experiment，the hydrocarbon accumulation mechanism and accumulation process in and under source of Paleozoic in Huanghua Depression were discussed. The results show that： （1）There is hydrocarbon accumulation in the in-source reservoirs of Paleozoic in Huanghua Depression，the in-source reservoirs are close to the source rocks，and the coal measure oil and gas can be charged preferentially. The stable structural background can make the in-source reservoirs well preserved.（2）Two necessary conditions are met for hydrocarbon accumulation in the Lower Ordovician，the fracture with upper end ending in coal measure and lower end connecting with Ordovician reservoirs， and the low angle fractures have higher transport efficiency. The source-reservoir pressure difference over 10 MPa is a good driving force for hydrocarbon accumulation.（3）The in-source and under-source reservoirs are characterized by accumulation in early and late stage and destroyed in middle stage. In Middle Cretaceous，low-mature crude oil was charged in large quantities. Strong tectonic uplift in Late Cretaceous caused the destruction or adjustment of the ancient oil reservoirs. In Cenozoic，with the further maturity of hydrocarbon source rocks，generation and expulsion of hydrocarbons，a large amount of coal gas and light oil accumulated and formed reservoirs.（4）The relatively stable areas with high-quality reservoirs developed within the range of hydrocarbon generation in the study area are favorable areas for in-source oil and gas exploration，while the areas where the Indosinian thrust faults developed and were weakly modified by later extension are favorable exploration areas for under-source oil and gas exploration.
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Shale oil accumulation conditions of Permian Lucaogou Formation in Fukang fault zone，Junggar Basin
LIU Zhongquan, ZHAO Leqiang, ZENG Zhiping, TIAN Jijun, LI Zhengqiang, LUO Jinchang, HU Meiling
2023, Vol.35(3): 126–137
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doi: https://doi.org/10.12108/yxyqc.20230311
Fukang fault zone is located in the foreland thrust belt of Junggar Basin，with complex structure and great exploration and development potential. The shale oil accumulation conditions of Permian Lucaogou Formation in Fukang fault zone were analyzed through organic geochemical testing of source rocks， cast thin section identification and scanning electron microscope analysis. The results show that： （1）The source rocks of Permian Lucaogou Formation in Fukang fault zone have high organic matter abundance，with an average TOC mass fraction of 3.65%， and the organic matters are mainly type Ⅱ1 with Ro values of 0.76-1.41，mostly in the mature to high mature stage，which is a set of good to high-quality hydrocarbon source rocks.（2）The average porosity of the reservoirs of Lucaogou Formation in the study area is 5.12%， and the permeability ranges from 0.02 mD to 2.69 mD，which is a set of reservoirs with low to extra-low porosity and extra-low permeability. The reservoir rock type is complex，and it is a set of hybrid sedimentary rocks dominated by mud shale， siltstone and carbonate rocks， with an average brittle mineral mass fraction of 82.96%. The reservoir space includes intergranular pores， intercrystalline pores，dissolved pores，organic matter pores and microfractures.（3）The widely overlying hydrocarbon source rocks，the dominant lithofacies distributed continuously in a large area and the favorable sourcereservoir configuration control the shale oil enrichment and accumulation of Lucaogou Formation in the study area， forming a shale oil accumulation model of “source-reservoir adjacent interval type” and “source-reservoir integrated matrix type” coexistence. Dalongkou area and Xiaolongkou to Qi 1 well area are the key areas for the next exploration and development.
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Characteristics and main controlling factors of natural gas of CarboniferousPermian in western well Pen-1 sag，Junggar Basin
JIANG Mengya, WANG Jiangtao, LIU Longsong, LI Hui, CHEN Hailong, JIANG Zhongfa, WANG Xueyong, LIU Hailei
2023, Vol.35(3): 138–151
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doi: https://doi.org/10.12108/yxyqc.20230312
Based on the seismic， drilling， logging， core， thin section and organic geochemical data， the geochemical characteristics，genesis，sources，main controlling factors of gas reservoir accumulation and exploration potential of natural gas of Carboniferous-Permian in western well Pen-1 sag of Junggar Basin were studied. The result shows that： （1）The volume fraction of methane in deep Carboniferous-Permian natural gas in western well Pen- 1 sag is 70.93%-96.55%，with an average of 81.78%，which is generally wet gas. The carbon isotope distribution is relatively wide. The carbon isotope value of methane ranges from -41.62‰ to -30.42‰，with an average value of -34.75‰，and most of them are in mature to high mature stage. The carbon isotope value of ethane ranges from -31.69‰ to -24.16‰，with an average value of -27.50‰，which means that coal type gas is the main origin of natural gas，followed by mixed origin gas. The relative contents of methylcyclohexane and n-heptane in C7 light hydrocarbon compounds are large，the relative mass fraction of methylcyclohexane is 32.14%-58.37%， with an average of 38.84%，and the relative mass fraction of n-heptane is 25.37%-56.56%，with an average of 47.79%.（2）The natural gas in the study area has complex origin and sources，the coal-type gas from the source rocks of lower Urho Formation and its mixture with oil-type gas of Fengcheng Formation are absolutely dominant，while the oil-type gas from the source rocks of Fengcheng Formation is less.（3）The source rocks of Permian Fengcheng Formation and lower Urho Formation in the study area have great gas generation potential，and multiple lithologic reservoirs are developed. Faults and unconformity permeable sand bodies constitute a transport system for deep gas migration and accumulation. Carboniferous paleo convex and Permian lithologic trap are complementary，which plays a good role of lateral shielding for the accumulation of natural gas in the slope area.（4）Carboniferous volcanic rocks in nose-bulge and clastic rocks of Permian Fengcheng Formation in sags in the study area are potential favorable areas for deep natural gas exploration in western well Pen-1 sag.
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Characteristics and reservoir accumulation model of Ordovician fault-controlled fractured-vuggy reservoirs in Shunbei oil and gas field，Tarim Basin
BU Xuqiang, WANG Laiyuan, ZHU Lianhua, HUANG Cheng, ZHU Xiuxiang
2023, Vol.35(3): 152–160
Abstract
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1364 )
PDF (4709 KB) (
370
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doi: https://doi.org/10.12108/yxyqc.20230313
Shunbei oil and gas field is an important oil and gas producing area in Tarim Basin. Based on drilling performance，core analysis，logging and seismic data，combined with acid fracturing curve and well test data， the characteristics and reservoir accumulation model of Ordovician fault-controlled fractured-vuggy reservoirs in Shunbei oil and gas field of Tarim Basin were studied. The results show that：（1）Fault-controlled fractured-vuggy reservoir of Ordovician in Shunbei oil and gas field is a special type of reservoir formed with the development of strike-slip faults. Vertical to the fault zone，multiple groups of fractured-vuggy aggregates composed of bedrockfracture zone-cave zone are developed，and cave zone and fracture zone are the main reservoir spaces. The seismic identification feature of large-scale reservoirs is fault-bead-disorder strong reflection.（2）The reconstruction curve of large-scale fault-controlled fractured-vuggy reservoirs in the study area has the characteristics of low initial pump pressure，large maximum pressure drop and low pump stop pressure. The drilling pressure recovery curves of fault zones ①，④ and ⑧ of the NE fault system are in a W-box shape.（3）According to the characteristics of seismic response and the shape of well test pressure recovery curve，the fault-controlled fractured-vuggy reservoirs in the study area can be divided into two types： cave type and fracture type，and they can be subdivided into four categories according to the shapes of pressure recovery curves： fractured-multi-cave type，fracturedcave type，cave-fracture type and fracture type.（4）The fault-controlled fractured-vuggy reservoirs in the study area have oil source from Yuertusi Formation，and migrate along strike-slip faults. The pores and fractures are the reser-voir spaces， and tight carbonate rocks and thick mudstones are the caprocks.
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Response characteristics and correction of LWD laterolog in anisotropic formations and deviated boreholes
LI Fengfeng, NI Xiaowei, XU Sihui, WEI Xinlu, LIU Diren
2023, Vol.35(3): 161–168
Abstract
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1393 )
PDF (3311 KB) (
295
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doi: https://doi.org/10.12108/yxyqc.20230314
The finite element numerical simulation method and parameter sensitivity function were used to simulate the response characteristics of toroidal coil excitation LWD laterolog instrument in anisotropic formation and deviated boreholes，the sensitivity of the instrument to the formation thickness/surrounding rock，anisotropy and well deviation angle were analyzed，and based on forward modeling results segment fitting，a calculation method for rapid correction of well deviation/anisotropy was proposed for different well deviation angles. The results show that：（1）When the thickness of the target layer is less than 0.5 m，the instrument response is seriously affected by the surrounding rocks. When the thickness is 0.5-5.0 m，the instrument response is affected by both the surrounding rock and anisotropy. When the thickness is greater than 5.0 m，the influence of anisotropy on the instrument response is dominant.（2）When the well deviation angle is less than 30 °，the logging response is less affected by the anisotropy coefficient，and the maximum difference of apparent resistivity is 2.5 Ω·m. When the well deviation angle is greater than 30 °，the instrument response is seriously affected by anisotropy and cannot reflect the horizontal resistivity of the formation.（3）This method has better correction effects in conductive formation and resistive formation with larger thickness.