【摘要】 如同世界上其它新生代沉积盆地那样,柴达木盆地在一定深度,区域上普遍存在异常高压。异常高压出现在快速沉积的厚层泥质岩中,水热增压效应明显,而且在上新世末至今发生了强烈的以水平挤压为主的构造运动,因此异常高压的形成是由于不均衡压实作用和构造挤压作用所引起的压应力增大以及热液压力引起流体体积的变化。异常高压是油气运聚的一种重要动力来源:在油气运移中,可以使上覆封隔层产生大量微裂缝,油气向上运移到在较低压储集层中,也可以使封闭性断层开启,通过断层进行侧向运移。更多还原

【Abstract】 Similar with other Cenozoic basins in the world, overpressure was found in relatively depressed areas in the western Qaidam Basin, which could be detected from observed pressure, logging information and well drilling information. Vertically, the formation pressure might be divided into three zones: the normal pressure, the transitional and the overpressure zones. The main causes for overpressure might be: 1)disequilibrium compaction caused by lack of permeable bed and rapid sedimentation, 2)the effect of aquathermal pressuring, for the porepressure growth gradient being significantly higher than the average overburden-pressure gradient, and 3)the tectonic movements characterized by horizontal compression occurring during Late Cenozoic. The montmorillonite-illite conversion and dehydration were not the prerequisites for the cause of overpressure. Overpressure must be an important factor for oil-gas migration and accumulation. Abundant microfractures, through which oil-gas migrated upwards into the low-pressure porous reservoir and accumulates, in the overlying sealing beds might be produced by the overpressure; and the sealed fault might be opened by pressure, so as to realize the lateral migration through the fault.更多还原