断裂转换带作为油气侧向、垂向运移通道的研究进展

断陷盆地大量油气勘探证实油气并非围绕整条断裂分布，而往往集中分布于断裂转换斜坡、弯曲转折端、交汇区及末端等断裂转换带位置，表现出明显的运移通道特征。为了查明断裂转换带输导油气的优势条件及模式，在对其形成演化过程分析的基础上，进行了油气运移特征的系统分析。结果表明，断裂转换带在不同的演化阶段既可以作为油气侧向运移通道，又可以作为油气垂向运移通道。当作为侧向运移通道时，具有以下三方面的优势条件：①具备油气侧向运移的流体势梯度；②砂体发育，储层对接概率大且侧向连通性好；③具有相对低的垂向与侧向渗透率比。侧向运移主要有两种模式，即未破坏型-侧向连通油气运聚模式和破坏型-垂向、侧向封闭油气运聚模式，油气富集层位一般与运移层位一致。当作为垂向运移通道时，具有以下三方面的优势条件：①“硬连接”型转换带活动强度一般较大，容易幕式开启作为通道；②“硬连接”型转换带处断层面常为脊状低势区，有利于油气发生汇聚；③应力集中、裂缝发育，容易破坏盖层发生油气垂向渗漏。垂向运移也主要有两种模式，即未完全破坏型-油气垂向穿斜坡渗漏模式和破坏型-油气沿断层面垂向运移模式，油气一般被调整至浅层富集。通过矿物沉淀速率、成岩作用、地下水渗漏及矿床突水现象等，均可证实断裂转换带部位曾是流体运移的通道。

Research progress in fault transformation zones as lateral or vertical hydrocarbon migration pathways

Plenty of oil and gas exploration practices in faulted basins have shown that hydrocarbons are mainly distributed in fault transformation zones instead of the whole fault zone,including relay ramp,flexural turning point,intersection area and terminal,which show remarkable characteristics of migration pathways.In order to find out the advantageous conditions and mode of hydrocarbon migration in fault transformation zones,we made a systematic analysis of the characteristics of hydrocarbon migration based on the study of the formation and evolution of fault transformation zones.The results show that the fault transformation zones may serve as both lateral and vertical pathways for hydrocarbon migration at different evolution stages.When acting as lateral migration pathways,they are advantageous in terms of (1) the gradient of fluid potential,(2) well-developed sand bodies characterized by a higher probability of reservoir juxtaposition and better lateral connectivity,and (3) a relatively lower ratio of vertical to lateral permeability.There are two main modes of lateral migration:undamaged-laterally connected hydrocarbon migration and accumulation mode,and destroyed-vertically and laterally sealed hydrocarbon migration and accumulation mode,and hydrocarbon enrichment horizons are generally consistent with migration horizons.When acting as vertical migration pathways,they are advantageous in terms of (1) a higher activity intensity for the hard-linkage transformation zone,prone to be a migration pathway with episodic opening; (2) the fault plane of the hard-linkage transformation zone,usually a ridge-shaped low-potential area,favorable for hydrocarbon accumulation; (3) the stress concentration and fracture development,tending to destroy the caprock and resulting in vertical seepage.Similarly,there are also two main modes of vertical migration:incompletely destroyed-vertical hydrocarbon seepage through relay ramps,and destroyed-vertical hydrocarbon migration along fault planes,in which oil and gas tend to accumulate in shallower horizons.In addition,it can be proven that the fault transformation zone has once been the pathway of fluid migration in terms of mineral precipitation rate,diagenesis,groundwater seepage and water inrush in mine,etc.