东濮凹陷濮卫地区地层压力演化及其与油气运聚的关系

Evolution of formation pressure and its relationship with hydrocarbon migration and accumulation in Puwei area,Dongpu depression

根据实测资料,对东濮凹陷濮卫地区地层压力的纵向分布特征进行分析,并运用盆地模拟方法对古近系沙三、沙四段古地层压力进行恢复;在油气分布与主成藏期地层压力平面和剖面分布关系研究的基础上,探讨异常地层压力演化与油气运聚的关系。结果表明:研究区纵向上发育常压、过渡和超压3种类型的压力带,异常高压的分布受构造背景和盐岩控制,其发育和演化经历了超压原始积累、超压释放和超压重新形成3个阶段;异常高压为油气初次和二次运移的主要动力,垂向上泥、砂压力差促进油气的初次运移,在剩余压力差的作用下,油气近距离运移并围绕洼陷中心区呈环状分布;与油气的充注过程相对应,濮卫地区常压带油气藏是沿活动断层长期运移和沿后期开启断层幕式运移的结果,以早期成藏为主,压力过渡带的油气藏在断层封闭条件下形成,以晚期成藏为主。

The distributions of formation pressure in the longitudinal direction were analyzed using measured data and the paleopressure was recovered in Es3 and Es4 of Palaeogene through basin modeling method in Puwei area,Dongpu depression. The relationship between evolution of formation pressure and hydrocarbon migration and accumulation was discussed. The results show that there are three zones in vertical direction about formation pressure in the Puwei area： the normal hydrostatic pressure zone,the transitional pressure zone and overpressure zone. Abnormal high formation pressure distribution was controlled by tectonic setting and distribution of saline rock. The paleopressure evolution was divided into three stages： initial overpressure accumulation stage,overpressure expulsion stage and overpressure reformation stage. Abnormal high pressure controlled primary migration and secondary migration of oil and gas. The differential pressure between mud and sand in vertical direction was beneficial to hydrocarbon primary migration,and the residual pore fluid pressure in the plane made hydrocarbon migrate at a short distance,and the hydrocarbon had a zonary distribution around Puwei sag. Corresponding to hydrocarbon charging histories,reservoirs in normal pressure zone were resulted from hydrocarbons long-term migration along active faults or episodic migration along late-opening faults,mainly to the early accumulation,and reservoirs in transitional pressure zone were resulted from the sealing of faults,mainly to the late accumulation.