塔木察格盆地反向断层与反转断层控藏机理

塔木察格盆地是大庆油田海外重要的油气资源生产基地。基于盆地构造运动的动力学性质及构造演化特征,自下而上将盆地划分为断陷层、断-坳转换层和坳陷层3个构造层,断陷阶段的被动裂陷作用使地层发生掀斜隆起,从而形成大量与地层倾向相反的反向断层;伊敏组沉积末期,在区域压扭应力场作用下,盆地发生强烈反转,形成了大量早期伸展中期压扭晚期反转的断层。分析已钻探的油气藏类型及其分布规律,认为反向断层和反转断层对油气藏的形成具有控制作用。根据生储盖组合的配置关系,盆地纵向上划分为上、中、下3套含油气系统,不同含油气系统间油气呈互补分布,其中以南一段为主的下部含油气系统是最重要的产油层系,油藏类型以反向断层遮挡的油气藏为主;平面上受控于控藏断层,下部油气主要沿反向断层呈条带状分布,上部油气大多靠近反转断层聚集。分析反向断层和反转断层的控藏机理,认为研究区发育反向断层背靠低隆起油气成藏和反转断层控制次生油气成藏2种成藏模式。

Controlling mechanism of antithetic fault and reverse fault on hydrocarbon accumulations in Tamtsag Basin

Tamtsag Basin is an important overseas hydrocarbon production base of Daqing Oilfield.Based on the dynamic properties and the tectonic evolution characteristics of the tectonic movement in the basin,the basin is divided into three structural strata from the bottom to the top,including fault-depression,fault-depression transformation,and depression.During the fault-depression,the passive rifting titled and uplifted the strata,to form a large number of antithetic faults which were opposite to the stratigraphic tendency.At the end of the deposition of Yimin Formation,the basin was strongly reversed under the action of regional compressive and torsional stress field,and many faults were formed with extension,compression,and torsion step by step.By analyzing the types and distribution of drilled hydrocarbon reservoir in the basin,it is believed that antithetic faults and reverse faults control the hydrocarbon accumulation.According to the configuration relationship of source-reservoir-caprock association,the basin is divided vertically into upper,middle,and lower three sets of hydrocarbon systems.The distribution of hydrocarbon in different systems is complementary,the lower hydrocarbon sys tem dominated by the first member of Nantun Group is the most important producing layer,and the reservoir type is mainly blocked by reverse fault.In the plane,hydrocarbon distributions are controlled by faults.Hydrocarbon is mainly arranged as a“strip”along the antithetic fault in the lower system and gathered near the reverse fault in the upper system.By analyz ing the controlling mechanism of antithetic faults and reverse faults,two kinds of hydrocarbon accumulation mode are sum marized,including the lower uplift hydrocarbon accumulation backed by antithetic fault and the secondary hydrocarbon accumulation controlled by the reverse fault in research area.