前陆盆地冲断推覆作用与烃源岩演化

前陆盆地是世界上油气资源最为丰富的盆地类型之一，而前陆盆地冲断带又是前陆盆地中最主要的油气富集区带之一。冲断带冲断推覆作用对烃源岩演化，储层性能，圈闭形成，烃类再分配等油气聚集的各个因素均具有重要的控制作用。为此，通过分析中国西部前陆盆地冲断推覆作用和烃源岩演化的关系，探讨了冲断推覆作用下烃源岩的演化模式，研究了冲断带烃源岩的演化方式和过程。将冲断推覆作用与烃源岩的演化关系分为三种简单模式：冲断推覆作用发生在烃源岩大量生烃之后，上下盘烃源岩成熟度受冲断推覆作用影响不大；冲断推覆作用与烃源岩大量生烃作用同时发生，上盘烃源岩热演化延迟，下盘烃源岩迅速熟化；冲断推覆作用发生在烃源岩大量生烃之前，上下盘烃源岩均可大量生烃，下盘烃源岩演化程度高于上盘烃源岩。该项研究对冲断带烃源岩的演化过程分析和烃类相态分布的控制因素分析具有实际指导意义。

RELATIONSHIP BETWEEN OVERTHRUSTING AND SOURCE ROCK EVOLUTION IN FORELAND BASIN

Foreland basin is one type of the most prolific petroliferous basins in the world, where thrust belt is one of its most abundant plays. Overthrusting of thrust belt controls all elements of hydrocarbon accumulation, including source rock evolution, reservoir properties, trap formation and hydrocarbon redistribution. Based on an analysis of the relationship between overthrusting and source rock evolution of the foreland basins in West China, the evolutionary modes of source rocks during overthrusting are discussed and the evolutionary pattern and process of source rocks in thrust belts are studied. The relationships between overthrusting and evolution of source rocks are simplified into 3 patterns. ①Overthrusting occurs after peak hydrocarbon generation of the source rocks and the influences of overthrusting on the maturities of the source rocks in the hanging wall and foot wall are not significant. ②Overthrusting occurs simultaneously with peak hydrocarbon generation, and thermal evolution of the source rocks in the hanging wall defers, while source rocks in the foot wall get mature rapidly. ③Overthrusting occurs before peak hydrocarbon generation, and the source rocks in both the hanging and foot walls may get mature, but the maturity of source rocks in the foot wall is higher than that in the hanging wall. The study is of practical significance for analyzing the evolutionary process of source rocks in thrust belts and the control factors of phase distribution of hydrocarbons.