准噶尔盆地西北缘大侏罗沟走滑断层油气成藏效应

走滑断层判识及其油气成藏效应是当前构造地质学与石油地质学研究的热点。为进一步认识准噶尔盆地西北缘地区的控藏断层大侏罗沟走滑断层,对其进行了野外露头观察和地震剖面解释,以进一步明确其构造属性与边界,在此基础上,结合油层分布与原油性质及地球化学特征分析,讨论了其成藏效应。结果表明,大侏罗沟断层走滑特征明显,西端野外露头上断线平直、断面陡立、发育水平擦痕,东端地震剖面平面上发育"马尾状构造"、剖面上发育"花状构造"。据此重新限定了断层的边界,西以达尔布特断层为界,东以达探1井为界,全长约80km。大侏罗沟走滑断层对油气兼具横向和纵向输导效应,使得油气藏在平面上沿断层被动盘富集,纵向上呈"串珠状"分布,这可能是这类走滑断层所具有的普遍特征。据此,研究区一系列走滑断层的被动盘在下步勘探中值得重点关注。

Re-characterization of the Dazhuluogou strike-slip fault in northwestern Junggar Basin and the implications for hydrocarbon accumulation

Characterization of strike-slip faults and their implications for hydrocarbon accumulation are highlights of structural and petroleum geology. In this paper, we conducted a combination study of outcrop survey with seismic profile interpretation of the Dashuluogou strip-slip fault to further understanding such a fault in northwestern Junggar Basin, aiming at re-characterizing the structural property and boundary of the fault. We then addressed the implications for hydrocarbon accumulation through additional analyses of oil layer occurrence and oil property and geochemistry. The results show that the Dazhuluogou fault has clear strike-slip characteristics. At its western termination, the fault line is straight and fault plane is steep with well developed lateral scratches according to outcrop survey. At the eastern end, according to seismic profile interpretation, horse tail and flower structures are developed in lateral and vertical directions, respectively. These new insights allow us to re-characterize the fault boundaries: the Daerbute fault and Well Datan 1 are the western and eastern boundaries, respectively, and the total fault length is approximately 80 km. The Dazhuluogou fault has influence on hydrocarbon migration both laterally and vertically that oil and gas pools accumulate in passive walls laterally and in “beaded” form vertically-possibly a general feature for such faults. Thus the passive walls of a series of strike-slip faults in the study area should be further explored.