准噶尔盆地腹部断裂活动对油气聚集的控制作用

Control of fault activity on hydrocarbon accumulation in central Junggar Basin

准噶尔盆地腹部发育NE、NW向为主的基底断裂和盖层断裂,侏罗系主要发育NE、NW向三角洲沉积体系。基底断裂的早期“显性”活动控制了主要二级构造带的边界、古凸起(古梁)展布、主断裂分布及四大压扭构造带的展布方向。后期NE向基底断裂的“隐性”活动导致上部盖层破碎,使早期的二叠纪古凸起带成为浅表断裂破碎带。河道水系的冲刷下切极易取其走向,从而控制了三工河组和西山窑组的主河道及主砂体沿NE向主断裂构造线及早期凸起带的展布,进而也就控制了油气藏的分布。基底断裂活动控制了油气的早期原生成藏与晚期调整次生成藏和再分配,盖层断裂通过与基底断裂的(反)树丫型、阶梯型、交叉型3种耦合方式形成花状构造、正反转构造组合而控制成藏,两类断裂在活动期和静止期控藏作用各不相同。腹部凸起区及斜坡上部为“三位一体”断控砂体次生成藏模式,凹陷区和斜坡下部还可能存在低幅度背景相控砂体原生(—混生)成藏模式。油气沿古梁聚集的构造本质是基底断裂显性及隐性活动的上延穿层效应。基于这2种模式,提出了岩性油气藏的有利勘探领域和勘探方法。

Basement faults and overburden faults mainly stretched to north-east and north-west directions in the central Junggar Basin. The Jurassic mainly developed two delta systems of sedimentary facies stretched to north-east and north-west directions. Early dominant activity of basement faults controlled the boundaries of main secondary structural zones, the up growth of ancient lobes, distribution of main faults and stretching direction of four pressing-twisting structural zones. The minor activity of basement faults in the north-east direction led to crushing of the overburden, so that the Permian lobe zones turned into the surface faulting crushing zones which were easily eroded and run down by fluvial channel or drainage systems. The main sandstone bodies of Sangonghe Formation and Xishanyao Formation were distributed along the main faults, lobe zones and tectonic line in the north-east direction, which showed the sedimentary was in response to activity of the north east basement faults. The activity of basement faults controlled the early formation of protogenic petroleum pools, later adjustment and formation of deuterogenic petroleum reservoirs. The overburden faults controlled the formation of petroleum pools by coupling basement faults and forming the combination system of flower structure and orthogyral reversal structure. The coupling manners included anti tree bifurcation type, ladder type and chiasm type. The controlling activity of faults on petroleum reservoirs was different in the active stage and in the repose period. There was a reservoir-forming model for triune deuterogenic oil pools with fault-controlled sandstone bodies in lobe zones and upper slope. There was a forming model for protogenic （to mixed） oil pools with facies-controlled sandstone bodies in sag and lower slope. The structural essence of petroleum accumulation along the Permian ridge was the upward-stretching effect of basement faults with dominant and minor activities. The favorable exploration areas and relevant exploration suggestion were brought forward based on these two models.