临南洼陷沙三段异常地层压力及其演化特征

异常地层压力的演化历史对深入理解油气的生、运、聚动力学过程至关重要.为揭示临南洼陷内异常地层压力的演化特征, 在流体包裹体组合概念的限定下, 利用热动力学模拟的方法, 对沙三段进行了地层古压力重建.地层压力系数随时间的演化表明, 沙三中、下亚段在30 Ma左右即发育有异常高压, 而现今洼陷内局部发育的异常低压为异常高压经过一定时期的演化后在晚期形成, 自30 Ma以来的整个演化过程表现出降压-增压-降压的旋回性特征.沙三上亚段在该地质历史时期均未发育异常高压, 但晚期也表现出明显的降压特征.结合生烃史、充注史及断裂活动性综合分析表明, 临南洼陷沙三段异常高压主要起源并受控于油气的生成与充注, 而异常低压主要起源并受控于断裂的多次、长期活动. 

Abnormal Formation Pressure and Its Evolution Features of the Third Member,Shahejie Formation,Linnan Sag

Evolution history of abnormal formation pressure is vital to further understanding of the dynamic processes of hydrocarbon generation, migration and accumulation. In order to reveal the evolution features of the abnormal formation pressure in Linnan Sag, thermodynamic modeling in accordance with concepts of fluid inclusion assemblage was employed to reconstruct the palaeopressures of the third member, Shahejie Formation. The evolution of formation pressure coefficients with time suggest that there had already developed overpressures at about 30 Ma in the middle and the lower sections of the third member of Shahejie Formation, and the whole evolution since 30 Ma shows a cyclic feature of pressure decreasing, increasing and decreasing. Underpressure was the result of overpressure evolution to the later period of that time. There was no overpressure developed in the upper section of the third member of Shahejie Formation during that time, but there was an obvious pressure decreasing trend during the later period of the whole evolution. Considering the hydrocarbon generation and charge histories, and the fault activities, integrated analysis indicate that overpressure was mainly caused and controlled by hydrocarbon generating and charging in the earlier time, while underpressure was mainly caused and controlled by multiple times and long-term activities of the faults, especially in the later time.