川东地区高陡构造带寒武系洗象池群天然气成藏条件

Accumulation conditions of natural gas of Cambrian Xixiangchi Group in high-steep structural zones,eastern Sichuan Basin

利用岩心、测井与地震资料,采用地震解释、平衡剖面以及包裹体检测等技术,恢复了川东地区高陡构造带的构造演化史,并对平桥、建南、梓里场构造的天然气来源、运聚与保存条件进行了分析。研究结果表明:(1)川东地区平桥断背斜圈闭东翼的单条逆断层使得下盘的龙马溪组烃源岩与上盘的洗象池群储层发生了侧向对接,天然气可穿过断裂带向上盘储层运移,具备较好的输导条件,且圈闭盖层未受到断裂作用破坏,保存条件良好,有利于天然气的聚集成藏。(2)建南断背斜圈闭翼部的多条平行的逆断层虽然实现了部分源-储对接,但是多条断层组合降低了其侧向输导能力,天然气未能大规模聚集。(3)梓里场断背斜圈闭的源-储配置与输导条件优良,但盖层的封盖能力较差,大多被断层破坏,钻探显示储层为水层。(4)川东地区高陡构造带寒武系洗象池群天然气聚集成藏的主控因素包括:断层或断层组合控制下的源-储配置、侧向输导条件以及盖层的封盖能力。

Baased on cores,well-log and seismic data,combined with seismic interpretation,balanced crosssection and inclusion detection techniques,the structural evolution history of the high-steep structural zones in eastern Sichuan Basin was restored,and the natural gas sources,migration,accumulation and preservation con-ditions in Pingqiao,Jiannan and Zilichang structures were analyzed.The results show that:(1)Single reverse fault on the eastern flank of Pingqiao faulted anticlinal trap in eastern Sichuan Basin caused a lateral conjunction between Longmaxi source rocks on the footwall and Xixiangchi reservoir on the hanging wall,which enables the migration of gas through the fault zone to the reservoir on the hanging wall and,with good transport conditions.The cap rocks of the trap are not damaged by faulting,and the preservation conditions are good,which is condu cive to gas accumulation.(2)Although multiple parallel reverse faults in the flank of Jiannan faulted anticlinal trap result in source-reservoir conjunction,the combination of multiple faults reduces the gas lateral migration ability,causing natural gas to fail to accumulate on a large scale.(3)The Zilichang faulted anticlinal trap has good source-reservoir assemblages and transport conditions,but the sealing ability of the cap rocks is poor,mostly reduced by faults.Drilling indicates that the reservoir is water-bearing.(4)The main controlling factors for the natural gas accumulation of Cambrian Xixiangchi Group in the high-steep structural zones of eastern Sichuan Basin are source-reservoir assemblages controlled by fault or fault combination,lateral transport conditions,and the sealing ability of of cap rocks.