大民屯凹陷压力场演化及其成藏意义

利用Basin-2盆地模拟软件模拟了辽河坳陷大民屯凹陷5条横向地质剖面的压力演化史,并探讨了其超压形成机制及油气成藏意义。模拟结果显示:①大民屯凹陷超压较明显,超压主要出现在沙三段及沙四段,超压演化总体上遵循“无超压-陡增-平缓上升-最高值-下降-最低值”这一规律;②大民屯凹陷超压的演化分为两个阶段:沙三段和沙一、二段沉积期(距今43.0～36.9Ma)为超压积累阶段,东营沉积期及其以后(36.9Ma至现今)为超压释放阶段。综合研究结果表明:①不均衡压实和生烃作用是大民屯凹陷超压发育的主要机制,断层对超压的积累与释放起着重要的控制作用;②大民屯凹陷的超压对油气成藏起着积极的作用,提供了油气运移的动力和通道,提高了高分子量组分特别是“蜡”的排出效率,同时也是泥岩刺穿构造的诱发因素,并可成为下伏油气藏的优质盖层条件。

Evolution of geopressure field in Damintun Sag and its significance on hydrocarbon accumulation

The overpressure evolution of five profiles in Damintun Sag was simulated using Basin-2 modeling software.The mechanism and significance of the overpressure for reservoir formation were discussed.The simulation shows that the overpressure in Damintun Sag is widespread and mainly occurs in Es 3 and Es 4 formations. The overpressure evolution generally obeys the rule of none-rapidly rise-slowly rise-the highest-decrease-the lowest. It can be divided into two stages. The overpressure was accumulated during Es 3 and Es 1+2 periods (from 43 to 36.9 million years before present), while it was released after Ed period (from 36.9 million years to the present).The integrated study shows that the undercompaction and hydrocarbon generation are the main mechanism for developing overpressure in Damintun Sag. Faults are the important factor for the accumulation and release of overpressure. The overpressure in Damintun Sag is the force of hydrocarbon migration and can offer the pathway of oil and gas migration and improve the expel efficiency of high-waxy oil. The overpressure causes the formation of mud diapir and is the pressure confining beds for the underlying oil and gas accumulation.