四川盆地震旦系—下古生界天然气成藏条件与勘探前景
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摘要
迄今为止,四川盆地震旦系—下古生界勘探程度仍然很低,对天然气成藏规律与主控因素的认识不够深入。为此,应用层序地层学理论和方法,编制了层序地层格架内沉积相图,开展成藏综合研究。结论认为,震旦系—下古生界发育有下寒武统筇竹寺组及下志留统龙马溪组2套优质泥质烃源岩,以及震旦系—奥陶系岩溶白云岩、灯影组台缘高能白云岩以及志留系小河坝组致密砂岩3大类储层,存在震旦系—奥陶系和志留系2套成藏系统,共发生4期烃类充注:第1期早成熟液态烃类充注发生在加里东期;第2期大规模液态烃充注发生在印支期;第3期充注主要发生在燕山期,以原油裂解为主;第4期发生在喜山期,主要为古气藏调整定型。乐山—龙女寺古隆起核部的岩溶风化壳、古隆起翼部的构造圈闭和川东志留系致密砂岩及震旦系台缘高能带是盆地内3大有利勘探领域。上述成果和认识将对该领域天然气的勘探提供指导作用。
Although the exploration of Sinian-Lower Paleozoic gas reservoirs started over 50 years ago in the Sichuan Basin,the exploration maturity is so low that we still hold poor understanding of the pattern and main controlling factors of gas accumulation.Therefore,we drew up a lithofacies map within the sequence stratigraphic framework by using the theories and methodologies of sequence stragtigraphy and performed a comprehensive study on the hydrocarbon pooling,from which the following conclusions are achieved.Two high quality source rocks(the Lower Cambrian Qiongzhusi Formation and the Lower Silurian Longmaxi Formation) occur in the Sinian-Lower Paleozoic.Three types of reservoirs are also identified,including the Sinian-Ordovician dolomite karst,platform-margin high-energy dolomite of the Dengying Formation,and tight sand of the Silurian Xiaoheba Formation.Two hydrocarbon accumulation systems,the Sinian-Ordovician and the Silurian respectively,are identified as well.In addition,hydrocarbon charging is found to occur in 4 phases.In the first phase,early mature liquid hydrocarbons were charged in the Caledonian epoch.In the second phase,large scale charging of liquid hydrocarbons occurred in the Indo-Chinese epoch.In the third phase,oil-cracked gas charging predominated in the Yanshan epoch.In the fourth phase,the fossil gas pools were levelled and finalized in the Himalayan epoch.The weathering crust in the core of Leshan-Longnǖsi palaeohigh,structural traps on the flanks of the palaeohigh,as well as the Silurian tight sand and the Sinian platform-margin high-energy facies zones in the eastern Sichuan Basin are favorable exploration targets.These understandings can guide future gas exploration in the study area.
Although the exploration of Sinian-Lower Paleozoic gas reservoirs started over 50 years ago in the Sichuan Basin,the exploration maturity is so low that we still hold poor understanding of the pattern and main controlling factors of gas accumulation.Therefore,we drew up a lithofacies map within the sequence stratigraphic framework by using the theories and methodologies of sequence stragtigraphy and performed a comprehensive study on the hydrocarbon pooling,from which the following conclusions are achieved.Two high quality source rocks(the Lower Cambrian Qiongzhusi Formation and the Lower Silurian Longmaxi Formation) occur in the Sinian-Lower Paleozoic.Three types of reservoirs are also identified,including the Sinian-Ordovician dolomite karst,platform-margin high-energy dolomite of the Dengying Formation,and tight sand of the Silurian Xiaoheba Formation.Two hydrocarbon accumulation systems,the Sinian-Ordovician and the Silurian respectively,are identified as well.In addition,hydrocarbon charging is found to occur in 4 phases.In the first phase,early mature liquid hydrocarbons were charged in the Caledonian epoch.In the second phase,large scale charging of liquid hydrocarbons occurred in the Indo-Chinese epoch.In the third phase,oil-cracked gas charging predominated in the Yanshan epoch.In the fourth phase,the fossil gas pools were levelled and finalized in the Himalayan epoch.The weathering crust in the core of Leshan-Longnǖsi palaeohigh,structural traps on the flanks of the palaeohigh,as well as the Silurian tight sand and the Sinian platform-margin high-energy facies zones in the eastern Sichuan Basin are favorable exploration targets.These understandings can guide future gas exploration in the study area.
引文
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[9]孙玮,刘树根,韩克猷,等.四川盆地震旦系油气地质条件及勘探前景分析[J].石油实验地质,2009,31(4):350-355.
[10]姚建军,陈孟晋,华爱刚,等.川中乐山—龙女寺古隆起震旦系天然气成藏条件分析[J].石油勘探与开发,2003,30(4):7-9.
[11]吕延防,付广,于丹.中国大中型气田盖层封盖能力综合评价及其对成藏的贡献[J].石油与天然气地质,2005,26(6):742-745.
[12]汪泽成.四川盆地天然气勘探接替层系深化研究与勘探目标评选[R].北京:中国石油勘探开发研究院,2000.
[2]张健,张奇.四川盆地油气勘探—历史回顾及展望[J].天然气工业,2002,22(增刊1):3-7.
[3]王兴志,方少仙,侯方浩,等.四川盆地灯影组储层原生孔隙内胶结物研究[J].西南石油学院学报,1998,20(3):1-3.
[4]宋文海.乐山—龙女寺古隆起大中型气田成藏条件研究[J].天然气工业,1996,16(增刊):13-26.
[5]代寒松,刘树根,孙玮,等.米仓山前缘震旦系灯影组天然气勘探前景探讨[J].西南石油大学学报:自然科学版,2010,32(5):16-26.
[6]徐世琦,洪海涛,师晓蓉.乐山—龙女寺古隆起与下古生界含油气性的关系探讨[J].天然气勘探与开发,2002,25(3):9-15.
[7]王兴志,黄继祥,侯方浩,等.四川资阳及邻区震旦系灯影组储层段沉积及层序地层学特征[J].西南石油学院学报,1996,18(3):1-9.
[8]梁狄刚,郭彤楼,陈建平,等.南方四套区域性海相烃源岩的分布[J].海相油气地质,2008,13(2):1-16.
[9]孙玮,刘树根,韩克猷,等.四川盆地震旦系油气地质条件及勘探前景分析[J].石油实验地质,2009,31(4):350-355.
[10]姚建军,陈孟晋,华爱刚,等.川中乐山—龙女寺古隆起震旦系天然气成藏条件分析[J].石油勘探与开发,2003,30(4):7-9.
[11]吕延防,付广,于丹.中国大中型气田盖层封盖能力综合评价及其对成藏的贡献[J].石油与天然气地质,2005,26(6):742-745.
[12]汪泽成.四川盆地天然气勘探接替层系深化研究与勘探目标评选[R].北京:中国石油勘探开发研究院,2000.
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