Discovery and Hydrocarbon Accumulation Mechanism of Quasi-Continuous High-Efficiency Reservoirs of Baikouquan Formation in Mahu Sag, Junggar Basin

摘要/Abstract

摘要： In recent five years, great breakthroughs have been made successively in the Lower Triassic Baikouquan formation in hydrocarbon-rich Mahu sag in the northwestern margin of Junggar basin, and the above-source quasi-continuous reservoirs with the reserves over hundreds of millions of tons are firstly discovered, which should be attributed to the changes of thoughtway from structural reservoir exploration to lithologic-stratigraphic reservoir and continuous reservoir exploration. Composite analysis on hydrocarbon accumulation mechanism shows that high-quality Carboniferous-Permian source rocks are developed in hydrocarbon-rich Mahu sag, which is favorable for oil generation; high-quality reservoirs and structural-lithololgic traps of fan-delta front facies are developed in Baikouquan formation, in which faults connect the source rock and the reservoir, which helps hydrocarbon accumulation; gentle structures with good top and bottom conditions in Baikouquan formation are in favor of hydrocarbon enrichment; abnormally high pressure and fractures occur in Baikouquan formation, and the oil here is of good quality and reservoir sweet spots are developed, which is good for high oil production. Therefore, quasi-continuous reservoirs with the reserves of hundreds of millions of tons in Baikouquan formation in Mahu sag are characterized by extensive oil distribution, local oil enrichment, jointly controlled by nose-like structural belts and favorable belts in delta front as well as faults, high-efficiency accumulation and great prospecting potential, which can be an important supplement to continuous reservoir exploration and research in the world. It is suggested that Huangyangquan fan, Mahu E fan and Xiayan fan with relatively low exploration degree should be focused on for further petroleum exploration at present.

关键词: Junggar basin, Mahu sag, Baikouquan formation, quasi-continuous reservoir, lithologic-stratigraphic reservoir, outside-source accumulation, fan-delta

Abstract: In recent five years, great breakthroughs have been made successively in the Lower Triassic Baikouquan formation in hydrocarbon-rich Mahu sag in the northwestern margin of Junggar basin, and the above-source quasi-continuous reservoirs with the reserves over hundreds of millions of tons are firstly discovered, which should be attributed to the changes of thoughtway from structural reservoir exploration to lithologic-stratigraphic reservoir and continuous reservoir exploration. Composite analysis on hydrocarbon accumulation mechanism shows that high-quality Carboniferous-Permian source rocks are developed in hydrocarbon-rich Mahu sag, which is favorable for oil generation; high-quality reservoirs and structural-lithololgic traps of fan-delta front facies are developed in Baikouquan formation, in which faults connect the source rock and the reservoir, which helps hydrocarbon accumulation; gentle structures with good top and bottom conditions in Baikouquan formation are in favor of hydrocarbon enrichment; abnormally high pressure and fractures occur in Baikouquan formation, and the oil here is of good quality and reservoir sweet spots are developed, which is good for high oil production. Therefore, quasi-continuous reservoirs with the reserves of hundreds of millions of tons in Baikouquan formation in Mahu sag are characterized by extensive oil distribution, local oil enrichment, jointly controlled by nose-like structural belts and favorable belts in delta front as well as faults, high-efficiency accumulation and great prospecting potential, which can be an important supplement to continuous reservoir exploration and research in the world. It is suggested that Huangyangquan fan, Mahu E fan and Xiayan fan with relatively low exploration degree should be focused on for further petroleum exploration at present.

Key words: Junggar basin, Mahu sag, Baikouquan formation, quasi-continuous reservoir, lithologic-stratigraphic reservoir, outside-source accumulation, fan-delta

ZHI Dongming. Discovery and Hydrocarbon Accumulation Mechanism of Quasi-Continuous High-Efficiency Reservoirs of Baikouquan Formation in Mahu Sag, Junggar Basin[J]. 新疆石油地质, 2016, 37(zk(English) ): 29-39.

ZHI Dongming. Discovery and Hydrocarbon Accumulation Mechanism of Quasi-Continuous High-Efficiency Reservoirs of Baikouquan Formation in Mahu Sag, Junggar Basin[J]. Xinjiang Petroleum Geology, 2016, 37(zk(English) ): 29-39.

参考文献

[1] SCHMOKER J W.U.S.geological survey assessment concepts for continuous petroleum accumulations[C]//SGS Southwestern Wy-oming Province Assessment Team.Petroleum systems and geolo-gic assessment of oil and gas in the southwestern Wyoming Pro-vince,Wyoming,Colorado,and Utah.U.S.Geological Survey Digital Data Series DDS-69-D,2005.
[2] BROWN A.Evaluation of possible gas micro-seepage mechanisms[J].AAPG Bulletin,2000,84(11):1,775-1,789.
[3] LAW B E.Basin-centered gas systems[J].AAPG Bulletin,2002,86 (11):1,891-1,919.
[4] SONNENBERG S A,PRAMUDITO A.Petroleum geology of the giant Elm Coulee field,Williston basin[J].AAPG Bulletin,2009,93(9):1,127-1,153.
[5] MCGLADE C E.A review of the uncertainties in estimates of global oil resources[J].Energy,2012,47(1):262-270.
[6] ZOU Caineng,TAO Shizhen,YUAN Xuanjun,et al.Global importance of “continuous”petroleum reservoirs:accumulation,distribution and evaluation[J].Petroleum Exploration and Development,2009,36(6):669-682.
[7] ZOU Caineng,ZHANG Guangya,TAO Shizhen,et al.Geological features,major discoveries and unconventional petroleum geology in the global petroleum exploration[J].Petroleum Exploration and Development,2010,37(2):129-145.
[8] DU Jinhu,HE Haiqing,YANG Tao,et al.Progress in China’s tight oil exploration and challenges[J].China Petroleum Exploration,2014,19(1):1-9.
[9] JIA Chengzao,ZHAO Zhengzhang,DU Jinhu,et al.PetroChina key exploration domains:geological cognition,core technology,exploration effect and exploration direction[J].Petroleum Exploration and Development,2008,35(4):385-396.
[10] HU Wenrui,BAO Jingwei,HU Bin.Trend and progress in global oil and gas exploration[J].Petroleum Exploration and Development,2013,40(4):409-413.
[11] TONG Xiaoguang,GUO Jianyu,WANG Zhaoming.The progress of geological theory and technology for unconventional oil and gas[J].Earth Science Frontiers,2014,21(1):9-20.
[12] LEI Dewen,ABULIMITI,TANG Yong,et al.Controlling factors and occurrence prediction of high oil-gas production zones in Lower Triassic Baikouquan formation of Mahu sag in Junggar basin[J].Xinjiang Petroleum Geology,2014,35(5):495-499.
[13] KUANG Lichun,TANG Yong,LEI Dewen,et al.Exploration of fan controlled large-area lithological oil reservoirs of Triassic Baikouquan formation in slope zone of Mahu depression in Junggar basin[J].China Petroleum Exploration,2014,19(6):14-23.
[14] TANG Yong,XU Yang,QU Jianhua,et al.Fan delta group characteristics and its distribution of the Triassic Baikouquan reservoirs in Mahu sag of Junggar basin[J].Xinjiang Petroleum Geology,2014,35(6):628-635.
[15] KUANG Lichun,TANG Yong,LEI Dewen,et al.formation conditions and exploration potential of tight oil in the Permian saline lacustrine dolomitic rock,Junggar basin,NW China[J].Petroleum Exploration and Development,2012,39(6):657-667.
[16] YANG Weiwei,LIU Guangdi,LIU Xianyang,et al.The accumulation mechanism and accumulation models of oil in low permeability reservoir of Yanchang formation in Longdong area,Ordos basin[J].Earth Science Frontiers,2013,20(2):132-139.
[17] FALL A,EICHHUBL P,STEPHEN P C,et al.Testing the basin centered gas accumulation model using fluid inclusion observations:southern Piceance basin.Testing the basin centered gas accumulation model using fluid inclusion observations:southern Piceance basin,Colorado[J].AAPG Bulletin,2012,96(12):2,297-2,318.
[18] ZHAO Wenzhi,HU Suyun,WANG Hongjun,et al.Large-scale accumulation and distribution of medium-low abundance hydrocarbon resources in China[J].Petroleum Exploration and Development,2013,40(1):1-13.
[19] CAO J,ZHANG Y J,HU W X,et al.The Permian hybrid petroleum system in the northwestern margin of Junggar basin North-west China[J].Marine &Petroleum Geology,2005,22(3):331-349.
[20] ZHAO Jinzhou,BAI Yubin,CAO Qing,et al.Quasi-continuous hydrocarbon accumulation:a new pattern for large tight sand oilfields in the Ordos basin[J].Oil &Gas Geology,2012,33(6):811-827.
[21] LEI Dewen,QU Jianhua,AN Zhiyuan,et al.Hydrocarbon accumulation conditions and enrichment regularity of low-permeability sandy conglomerate reservoirs of Baikouquan formation in Mahu sag,Junggar basin[J].Xinjiang Petroleum Geology,2015,36(6):642-647.
[22] LIU Chiyang,ZHAO Junfeng,MA Yanping,et al.The advances and problems in the study of the characteristics and formation of hydrocarbon-rich sag[J].Earth Science Frontiers,2014,21(1):75-88.