大巴山前陆冲断带古水动力演化阶段及其对油气藏形成和保存的影响

The Evolution of Paleohydrodynamics of Dabashan Foreland Thrust Belt and Its Influence on Formation and Preservation of Oil and Gas Reservoirs

针对传统古水动力阶段划分存在的问题,结合大巴山前陆冲断带特殊构造特征,以油气成藏组合为单元,将大巴山前陆冲断带古水动力演化阶段划分为沉积水动力阶段、渗入水动力阶段、构造作用水动力阶段和埋藏水动力阶段。其中下部油气成藏组合主要经历了1个沉积水动力阶段、4个渗入水动力阶段、4个埋藏水动力阶段和3个构造作用水动力阶段,中部油气成藏组合主要经历了1个沉积水动力阶段、3个渗入水动力阶段、2个埋藏水动力阶段和3个构造作用水动力阶段,而上部油气成藏组合主要经历了渗入水动力阶段。二叠纪至早白垩世的埋藏水动力阶段有利于下部油气成藏组合油气的生成和运聚成藏,但是构造作用水动力阶段,对油气藏的调整和改造作用影响很大,晚白垩世之后的渗入水动力阶段,导致下部成藏组合的油气藏进一步遭到调整和破坏。在晚三叠世末至晚白垩世的埋藏水动力和构造作用水动力阶段,中部成藏组合的原油发生大量裂解,同时形成了许多调整-改造型油气藏,晚白垩世之后的渗入水动力和构造作用水动力阶段,大巴山前陆坳陷带中部成藏组合的油气藏发生了大量的调整和改造作用,而大巴山前陆基底拆离构造带和前陆盖层滑脱构造带中部成藏组合的油气藏则主要表现为改造和破坏作用。

Concerning the problems in the traditional division of paleohydrodynamic stage,this paper takes account of the specific tectonic characteristics of Dabashan foreland thrust belt,and divides its evolution into sedimentary hydrodynamic stage,infiltrating hydrodynamic stage,tectonic hydrodynamic stage and burial hydrodynamic stage in the unit of hydrocarbon accumulation play.The lower play had gone through one sedimentary hydrodynamic stage,four infiltration hydrodynamic stages,four bury hydrodynamic stages and three tectonic hydrodynamic stages;The middle play,one sedimentary hydrodynamic stage,three infiltration hydrodynamic stages,two bury hydrodynamic stages and three tectonic hydrodynamic stages,and the upper one,mainly infiltration hydrodynamic stage.The burial hydrodynamic stage from Permian to Early Cretaceous was favorable for hydrocarbon generation,migration and accumulation,but the reservoirs were adjusted and reformed a lot during the tectonic hydrodynamic stage.They were further adjusted and destroyed during the infiltrating hydrodynamic stage after Late Cretaceous.Oil crack were common in the middle hydrocarbon play in burial/connate hydrodynamic stage and tectonic hydrodynamic stage from the end of Late Triassic to Late Cretaceous,in the meantime,lots of adjusted-and-reformed oil and gas reservoirs were formed;after Late Cretaceous,many adjustments and reforms of oil and gas reservoirs took place in the middle hydrocarbon play in Dabashan foreland depression belt during burial/connate hydrodynamic stage and tectonic hydrodynamic stage,while the plays in Dabashan foreland basement detachment tectonic belt and Dabashan foreland decollement tectonic belt in cover strata were mainly destroyed and reformed.