利用东营凹陷典型剖面分析地层压力演化与油气成藏关系

运用盆地模拟方法对东营凹陷新生界地层异常压力演化特征进行分析,并结合油气成藏期次分析对异常压力演化与油气藏分布进行了研究。模拟结果显示:东营凹陷古近系沙四上亚段(Es4上)和沙三下亚段(Es3下)烃源岩地层中普遍发育异常压力,并以超压为主;异常压力演化具有波动性,总体上经历了早期形成、中期下降调整、晚期再次增大3个阶段,分别对应沙河街组—东营组沉积期、沉积间断构造抬升期和馆陶组—第四纪沉积期。通过超压演化与油气成藏期次分析发现,现今处于超压环境中的油藏,在成藏过程中未必处于超压环境。早期形成的异常压力为Es4上和Es3下部分烃源岩中油气向邻近的圈闭运移聚集提供了充足的成藏动力,并有利于油气藏的保存。

Application of typical profile to analysis of reservoir pressure evolution and hydrocarbon accumulation in Dongying Sag

Basin modeling technology is applied to analyze distribution and evolution characteristics of abnormal pressure system of Cenozoic in Dongying Sag.Based on the analysis of hydrocarbon accumulation stages,the influence of reservoir pressure evolution on the hydrocarbon accumulation is studied.Numerical modeling result shows that abnormally high pressures occur in the third and fourth members（Es3 and Es4） of Eocene Shahejie Formation,and the pressures are mainly overpressure.The overpressure evolution in the sag is fluctuating and divided into three stages：original-forming,medium-declining adjustment and latest-raising stages,respectively corresponding to the stage of Shahejie to the final stage of Dongying Formation,the stage of uplifting and denudation,and the stage of Guantao Formation to Quaternary depositional stage.The study of overpressure evolution and hydrocarbon accumulation stages shows that the reservoir which is in the overpressure environment now may not be in overpressure environment when the hydrocarbon accu-mulation occurred.In the early time,the overpressure is favorable power for hydrocarbon migration and accumulation in the lithologic reservoir,and conducive to the preservation of lithologic reservoir.