龙门山造山带与川西前陆盆地耦合关系及其对油气成藏的控制

Basin-range coupling system and its control on oil and gas accumulation in the Longmen orogenic belt and the West Sichuan foreland basin

以盆地构造-沉积分析为手段,研究了印支期以来川西前陆盆地与龙门山造山带的耦合关系,探讨了川西前陆盆地的构造演化及其对油气藏的控制作用。认为龙门山造山带是经历了印支期、燕山期和喜马拉雅期多期、多类型推覆叠加而形成的复杂地质体,因而造成川西前陆盆地经历了前陆、坳陷、再生前陆的沉积充填过程;该区盆山耦合模式主要为剖面上的前展式逆冲双重构造,平面上表现为NE构造带和近EW向的横断层;造山带和盆地的共同演化不仅形成了多套烃源岩,而且控制了油气保存与有效成藏区带。逆掩推覆带和前陆坳陷带是油气勘探的有利区带。

By means of analysing the basin structure-deposition and taking basin-range coupling as the train of thought,this paper studies the coupling system between the West Sichuan foreland basin and the Longmen orogenic belt since Indon-Chinese epoch and discusses the structural evolution of the West Sichuan foreland basin and the systems control on oil and gas accumulation.The authors consider that the Longmen orogenic belt is a complicated geologic body which has undergone multiphase and all kinds of nappings and superposings in the Indonsinian,Yanshanian and Himalayan movements,and therefore the West Sichuan foreland basin has undergone the filling course of foreland,depression and re-generated foreland.This makes the Longmen orogenic belt continuously promote to SE and the West Sichuan foreland basin fall back to SE.The model of the basin-range coupling in this area is dominated by the double structure of forward expanding obduction in cross section and the NE structural belt and nearly EW cross fault in plane.The joint evolution of the orogenic belt and basin not only forms multiple sets of hydrocarbon source rocks,but controls the distribution of oil and gas.The covered structural belt and the depression of foreland basin are favorable belts for oil and gas exploration.