柴达木盆地西部第三系异常高压与油气成藏

柴达木盆地在一定深度及区域上普遍存在异常高压.一方面,异常高压是油气运聚的一种重要动力来源;另一方面,异常高压在一定地质背景下是控制油气分布的重要因素.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;异常高压形成的流体势能驱动流体从凹陷中心向凹陷边缘流动,最终形成油气藏围绕生油凹陷分布的格局.该区与异常压力有关的油气成藏模式可以概括为3种类型,即:位于异常高压体系内部裂缝型高压油气藏,异常高压体系下部孔隙型高压油气藏,位于封隔层之上的孔隙型常压油气藏.这些模式对油气勘探与开发具有重要的意义.

Relationship between abnormal overpressure and reservoir formation in the Tertiary of the Western Qaidam Basin

Abnormal overpressure exists widely in certain area and depth in the Tertiary of Qaidam Basin.Abnormal overpressure is an im-portant factor for hydrocarbon migration and accumulation.Abundant micro-cracks can be produced in the overlying sealing beds under the abnormal overpressure.Oil and gas can migrate through the micro-cracks upwards and enter into the low-pressure porous reservoirs.The sealed faults may be open,so as to realize the lateral migration of oil and gas through the faults.The fluid potential resulted from the abnormal overpressure drives oil and gas flowing from the center of depression to the margin,which leads to the formation of marginal oil and gas reservoirs around hydrocarbon-generation depression.In the meantime,the abnormal overpressure is an important factor for controlling the distribution of oil and gas under certain geologic background.Three oil and gas accumulation models closed with the abnormal overpressure in western Qaidam Basin include fractured overpressure reservoir within abnormal overpressure system,porous overpressure reservoir underneath abnormal overpressure system,and atmospheric porous reservoir above sealing layers.These models have the important and directive effects for oil and gas exploration and development.