塔里木盆地西南坳陷油气成藏模式

Hydrocarbon accumulation modes of the southwest depression in Tarim Basin

塔西南坳陷构造复杂,具有东西分带、南北分段以及分期差异变形的特点,可划分为山前逆冲推覆构造带、和田—喀什凹陷带、麦盖提斜坡带、于田凸起4个二级构造单元。系统分析了寒武—奥陶系、石炭系、二叠系、侏罗系4套烃源岩及其分布特征,在储层、盖层分析基础上,初步指出该区发育7套有利储盖组合,认为断层、不整合面和渗透性地层为该区良好的输导体系。在以上成藏条件综合分析基础上,综合考虑油气来源、运移方式、储层特征等条件,对成藏模式进行分析和归类,将油气成藏模式划分2大类5种模式,分别是近源垂向运移山前逆冲推覆构造带成藏模式:外来推覆体型、楔状体型、原生体型,远源侧向运移斜坡带成藏模式:断展褶皱型和古岩溶型,并进一步预测了研究区有利油气勘探方向。

The southwest depression of Tarim Basin has good prospect of oil and gas resources,and it is currently the focus of the new exploration areas.The depression structure is complicated,which has zonality from east to west,sectional division from north to south,and characteristics of deformation in different stages.Hence it can be divided into four secondary tectonic units：thrust belt in the foreland of the Kunlun Mountains,Hetian-Kashi sag zone,Mageti slope,and Yutian uplift.Four sets of hydrocarbon source rocks of Cambrian-Ordovician,Carboniferous,Permian and Jurassic and their distribution characteristics were systematically analyzed,and the oil and gas source and characteristics in the area were summarized and analyzed on the basis of an analysis of reservoir and cap rock.Seven sets of favorable reservoir-cap combinations were tentatively put forward,the faults,and unconformities and permeable formations were considered to be good conducting systems.On the basis of comprehensive analysis of above accumulation conditions,in combination with the comprehensive consideration of such factors as oil and gas source,migration way and reservoir characteristics,the authors analyzed the accumulation mode,which is divided into two major types and five sorts of modes：one type is piedmont thrust belt near the source vertical migration accumulation mode,which includes exotic thrust body,wedge shaped body and primary body,whereas the other type is slope belt distant source lateral migration accumulation mode,which includes fault-propagation folds and ancient karst.On such a basis,favorable oil and gas exploration targets are further forecasted.