济阳坳陷沾化凹陷异常高压与油气成藏模式

Abnormal pressure and hydrocarbon reservoiring pattern of the Zhanhua sag in Jiyang Depression

徐东锋，赵红佳，刘见宝

摘要：渤海湾盆地济阳坳陷沾化凹陷沙河街组二段及其以上层段，圈闭类型以构造为主；沙河街组三段及其以下地层，主要发育岩性、构造-岩性等隐蔽圈闭。地层压力的分布与油气分布特征存在一定的对应关系，即正常压力带发育构造油气藏，而异常高压带多发育岩性等油气藏。异常高压为深层岩性油气藏油气的运移提供了动力。凡压力系数曲线呈现“3”字形，则相对低压油层含油性较好。根据压力与油气成藏的关系，建立了“源外断裂输导成藏”和“源内高压充注成藏”两种成藏模式。油源断层是浅部源外常压油气成藏的主控因素，沙河街组三段中、下亚段及沙河街组一段生成的油气，主要沿断层经垂向输导进入沙河街组二段及其以上地层，直接在断块、滚动背斜等构造圈闭中充注成藏，或经横向运移在构造圈闭中充注成藏。油气成藏动力是深部源内高压成藏的主控因素，沙河街组三段中、下亚段生成的油气，在异常高压的驱动下直接向其紧邻的砂岩体及构造-岩性圈闭中充注成藏。

Abstract: In Zhanhua sag of Jiyang Depression in Bohai Bay Basin, structural traps are predominant in the second member of the Shahejie Formation and the strata above it, while subtle traps such as lithologic and structurallithologic traps dominate the third member of the Shahejie Formation and the strata below it. There is a certain correlation between formation pressure distribution and hydrocarbon distribution in the area, i.e., structural reservoirs occurring in areas with normal pressure while lithologic reservoirs being developed in areas with abnormal high pressure. Abnormal high pressure provides impetus for the migration of hydrocarbons in deep lithologic reservoirs. When the pressure coefficient curve presents a “3”shape, reservoirs with relatively lowpressure have higher oil potentials. Based on the relationship between formation pressure and hydrocarbon accumulation, we set up two accumulation models: “externalsourced hydrocarbons accumulating via carrier faults” and “internalsourced hydrocarbon accumulating via highpressure injection”. Shallow externalsourced hydrocarbon accumulations with normal pressure are mainly controlled by source rockrooted faults. For example, the hydrocarbon generated from the lower and mid parts of the third member of the Shahejie Formation migrates vertically along the faults and accumulates in the structural traps such as fault block and rolling anticlines in the second member of the Shahejie Formaiton and strata above it, or migrates laterally to and accumulates in structural traps. The controlling factor for the second pooling model is abnormal high pressure. Hydrocarbons generated from the lower and mid parts of the third member of the Shahejie Formation may be charged into adjacent sandbodies and structurallithologic traps under the drive of the abnormal high pressure.

10.11743/ogg20110414