吐哈盆地地质结构和油气聚集规律的新认识

通过地质露头、地震 剖面、钻井等资料结合逆冲构造理论分析,发现吐哈盆地台北凹陷具有独特的构造样式和地质结构,从而提出自北向南依次分为山体楔形带、山前断阶带、冲断褶皱带,凹陷斜坡带、中央隆起带的新认识,以区别于原有的北部山前带、鄯善弧形带的划分方案。其中冲断褶皱带与中央隆起带进一步分为东西两个分支,各分支在南北向的重叠.上非常一致,反映了吐哈盆地新生代以来受造山带逆冲挤压和盆地基底断块抬升的应力格局。台北凹陷的埋藏史、生烃史研究表明,有两次快速沉降期(中-晚侏罗世、中新世-第四纪)。第二期烃源岩埋深加大,经历地质时间长,有利于油气大规模生成并聚集成藏,并与冲断褶皱带的大部分地区的构造形成互相配置。分析表明:山前两排褶皱带在靠近生油凹陷和走滑断层的构造低部位的砂岩体更有利于晚期油气藏的聚集;断阶带和中央隆起带的下盘也是有利的勘探目标。

New Understandings About Geological Structures and Hydrocarbon Accumulation Mode in Turpan-Hami Basin

Taibei sag in Turpan-Hami basin is characterized by distinctive structural style and geologic structure based on data from geologic outcrop,seismic profile and drilling-log integrated with thrust plate theoretical analysis.It is suggested that from north to south Taibei sag is divided into wedge-shaped mountain belt,piedmont fault-bench belt,thrust fold belt,sag slope belt and central uplift belt which are distinguished from originally classified north piedmont belt and Shanshan arcuate belt.According to this new understanding,the thrust fold belt and central uplift belt can be subdivided into two branches in east and west trends,with well overlapping in north and south trends,showing stress framework squeezed by thrust orogenic zone and affected by tilting basinal basement fault block since Cenozoic era in Turpan-Hami basin.The burial history and hydrocarbon-generating history of Taibei sag show that two rapid subsiding periods take place,i.e.,Middle-Late Jurassic and Miocene-Quaternary.In such a long period of Miocene-Quaternary period lasted long and added the burial depth of source rocks,hence,it was favorable to enormous generation and accumulation of hydrocarbon,and forming configuration with structures in most areas of thrust fold belt.The analysis indicates that sand bodies in lower locations near source sag and shove fault of two rows of piedmont fold belts are more favorable to accumulations of late hydrocarbon reservoirs;while the footwalls of fault-bench belt and central uplift belt are also as targets for exploration.