超压泥岩盖层封闭性演化规律及其研究意义

为了研究超压泥岩盖层封闭性演化规律,在超压形成与演化分析的基础上,通过超压演化规律的定量研究,对超压泥岩盖层封闭性演化规律进行了定量研究,结果表明超压泥岩盖层封闭性演化是按阶段进行的,每一次超压释放表明上一次封闭性演化阶段的结束,下一次封闭性演化阶段的开始,每一次演化过程中封闭性逐渐增强,在超压释放期封闭性降至最低点。研究超压泥岩盖层封闭性演化规律不仅可以准确评价目前封闭能力和预测封闭能力演化,而且还可以研究封闭油气的有效性。实例应用结果表明,古龙凹陷嫩一、二段超压泥岩盖层目前已刚刚结束第3阶段演化,开始第4阶段演化,具6.0 MPa的超压。随着演化进行,超压值将继续增大,封闭性继续增强。嫩一、二段超压盖层封闭性演化史与青山口组源岩生烃史匹配关系较好,可封闭住青山口组源岩生成的大量油气,有利于青山口组源岩生成的油气在萨、葡、高油层中聚集和保存。

EVOLUATION LAW FOR SEALING OF OVERPRESSURED MUDSTONE CAPROCK AND ITS RESEARCH SIGNIFICANCE

Based on the analysis of formation and evolution of overpressure,the evolution law for sealing of overpressured mudstone caprock was quantitatively studied by the quantitative study of evolution law of overpressure.The result showed that sealing of overpressured mudstone caprock evolved in stages.Each release of overpressure indicated the end of an old evolution stage and the beginning of a new evolution stage.Sealing of overpressured mudstone caprock increased gradually in each evolution process,sealing of overpressured mudstone caprock was the worst at the release period of overpressure.The study of evolution for sealing of overpressured mudstone caprock can not only determine exactly seal ability now and forecast seal evolution,but also study seal efficiency for oil-gas.Application of actual example iudicated overpressured mudstone caprock of K_(1)n_(1 2) in the Gulong sag just ends at the third evolution stage and begins at the fourth evolution stage,with 6.0 MPa overpressure.Overpressure increased with increasing evolution,sealing of overpressured mudstone caprock increased with increasing overpressure.The matching relation between evolution for sealing of overpressured mudstone caprock of K_(1)n_(1 2) and generation history of K_(1)q_(n)sourcerock,is good,can seal a great deal of oil-gas from K_(1)q_(n)source rock.It is favorable for oil-gas from K_(1)q_(n) source rock in S,P,G oil layers to accumulate and preservate.