新(晚期)构造运动的物质、能量效应与油气成藏

受板块构造背景和深部过程的控制,不同盆地的新(晚期)构造运动具有不同的表现型式,包括伸展和转换-伸展背景下的快速沉降和断裂活化、挤压背景下的强烈隆升和构造掀斜等。新(晚期)构造运动对油气成藏具有强烈的物质效应(对油气成藏要素构成的改造)和能量效应(对成藏动力学环境和过程的影响)。新(晚期)构造运动对油气成藏和分布的影响取决于新(晚期)构造运动期源岩的生排烃状态、新(晚期)构造运动的动力学性质、沉降-抬升的速率、幅度和区域变化及断裂活动程度。建造期(盆地保持沉降、充填状态;源岩处于生、排烃阶段;超压的产生过程仍在进行,超压释放后可得到动态补给)的构造运动可以导致幕式快速成藏,所形成的油气藏属于阶段性充注的原生油气藏,改造期(盆地沉降、充填停止,处于抬升、剥蚀和构造变形状态;源岩生、排烃作用已终止;超压的产生过程已经终止,超压释放后不能得到补给)断裂活化型构造运动可导致已聚集油气的突发性穿层运移和跨层聚集,形成非连续充注的次生油气藏;改造期无断裂活化型构造运动特别是构造掀斜运动可以导致已聚集油气的层内调整,形成有成因联系的调整型油气藏系列。新(晚期)构造运动对油气成藏既可以具有建设性作用、也可以产生调整、改造作用甚至破坏作用。

The Material and Energy Effects of Neotectonics/Late-stage Tectonics and Petroleum Accumulation

Neotectonics is defined as tectonic motions since the Late Miocene (about 5.2 Ma) in Cenozoic basins, and late-stage tectonics is defined as tectonic motions since the beginning of the Tertiary in superimposed basins in this paper. Neotectonics/late-stage tectonics behaves differently in different basins due to different plate-tectonic settings and different deep-crustal processes. Neotectonics/late-stage tectonics may considerably affect the hydrocarbon-generation potentials of source rocks, reservoir-seal assemblages, fluid conduit frameworks and the nature of traps, producing important material effects. Neotectonics/late-stage tectonics may also considerably affect thermal fields, pressure and stress regimes, producing strong energy effects. The roles that neotectonics/late-stage tectonics may play in petroleum accumulation depend on the stages of hydrocarbon generation and expulsion of the source rocks, the dynamic nature of neotectonics/late-stage tectonics, the velocity and amount of sedimentation or erosion during the neotectonics/late-stage tectonics, and the activity of the faults. During the construction stage, neotectonics/late-stage tectonics, combined with overpressure, may result in non-steady, cross-formation petroleum migration and rapid petroleum accumulation, leading to the enrichment of petroleum in shallow (young) reservoirs and in tectonically active belts or stress-relief structural zones. During the reform stage, neotectonics/late-stage tectonics with strong fault activity may lead to abrupt cross-formation re-migration of accumulated petroleum, forming secondary petroleum reservoirs. Neotectonics/late-stage tectonics with no fault reactivation may lead to intra-reservoir re-migration (adjustment) of accumulated petroleum, forming a series of genetically-related petroleum layers with complicated oil/water or gas/water contacts, complicated relationship between oil/gas saturation and porosity and permeability of reservoir rocks. Neotectonics/late-stage tectonics may play constructive, adjusting or even destructive role in petroleum accumulation, depending on the stage of the basin evolution and the nature of the neotectonics/late-stage tectonics.