孤南洼陷异常流体压力与油气运移聚集

Abnormal Fluid Pressure and Petroleum Migration and Accumulation in Gunan Sag

本文分析了孤南洼陷异常流体压力产生的原因，分布特征及其与油气运移聚集的关系。认为压实作用是形成孤南洼陷异常流体压力的重要原因。孔隙流体压力垂向上可以划分为静水压力带、过渡带和异常压力带。剖面上，高压层顺层分布，将洼陷分割成多套相对独立的压力系统。沙三段和沙一段是洼陷内的两套生油岩，同时又是异常高压层，起到了良好的封闭作用，其生成的油气主要排向上下流体压力较低的储集岩，并在其中侧向运移，只有在边界断层附近，油气才大规模运移到浅层聚集。平面上，孔隙流体压力具有绕洼陷中心呈环带状分布的特点。油气运移的方向主要为北部的陡坡带，其次为南部的缓坡带。

This paper analyzes the generation and distribution of abnormal pressure in the Gunan sag,Bohai Bay Basin, as well as its influence on petroleum migration and accumulation.Undercompaction is regarded as the most important factor in abnormal pressure generation. In vertical, pore fluid pressure can be divided into 3sections, i. e, hydrostatic pressure section, transitional pressure section and abnormal overpressure section. In profile, overpressure distribute along strata, and divide the sag into several independent pressure systems. Es3 and Es1 members act as source rocks, as well as overpressure strata. Petroleum occurred in source rocks first migrated vertically to the overlying and underlying reservoir rocks, then migrated laterally in the reservoir rocks. Orily near the boundary faults can petroleum migrate to the shallow strata and accumulate.In horizon, pore fluid pressure circularly distribute, i. e., from the center to the margin of the sag, fluid pressure decreases gradually. Petroleum mostly migrated to the northern steep slope.