Overpressure in shale is the main force for hydrocarbon expulsion and primary migration, and its changes are always recorded by the evolution of shale's porosity. Firstly, the evolution module of shale's porosity in undercompacted shale was set up through compaction section reflecting the characteristic of compaction at present. And then the method of "regressive extrapolation" modeling was used to restore evolution porosity increment of paleo-porosity shale in hydrocarbon accumulation period. Based on this restoration, the total porosity of undercompacted shale could be figured out by the evolution module of shale's porosity. Finally, modified Phillippone formula could be used to calculate paleo-formation pressure of source rocks and to recover evolution of paleo-formation pressure. The result showed that overpressure of source rock of the 3rd Member of Shahejie Formation enhanced gradually from south to north in eastern slope of Jinxian 1-1 low uplift, and the change regular of paleoformation pressure was important for hydrocarbon migration and profitable target selection.%烃源岩生烃过程中欠压实作用形成的异常高压是油气成藏的主要动力,而泥岩孔隙度演化记录了其地层压力的变化过程.根据现今泥岩压实剖面特征建立欠压实泥岩孔隙度计算模型,利用“回归反推”方法恢复成藏期沙三段欠压实泥岩古孔隙度增量,然后根据泥岩孔隙度压实模型恢复欠压实泥岩在成藏期的总古孔隙度,最后通过改进的Phillippone公式计算成藏期古地层压力并恢复其演化过程.研究表明,金县1-1低凸起东斜坡成藏期沙三段烃源岩普遍发育异常高压,古流体动力由南向北逐渐增强,压力系数分布呈现东南部低西北部高的特点,古流体压力的强弱变化规律对油气运移及有利目标的优选具有重要的意义.
展开▼
