印度河盆地A区块构造特征及其对油气的控制

摘要

Indus Basin is the biggest sedimentary basin in Pakistan, hydrocarbon enrichment zones are mainly in structural traps controlled by faults in Cretaceous.It has a great significance for the hydrocarbon exploration to clarify its tectonic characteristics and evolution. Based on regional tectonic background and abundant seismic data,we analyze structural characteristics and tectonic evaluation,and summarize its control of hydrocarbon accumulations in the Block A of the basin.Based on the tectonic evolution analysis,the study area has undergone three major stages:Gondwanaland continental rift period,Indian plate drift period,and plate collision period.The strike-slip phase of the Indian plate drift period was the main period for trap forming.The tectonic activity after the hydrocarbon accumulation were whole uplift and subsidence,upthrow synthetic fault terrace reservoirs had partially destroyed,while the tectonic activity had very little influence on upthrow antithetic fault terrace reservoirs.As a result, the former hydrocarbon reservoirs are characterized by large closure with small height of hydrocarbon,while the latter hydrocarbon reservoirs are characterized by high filling degree of hydrocarbon.The above observations might provide a guidance of favorable target evaluation in the Block A.%印度河盆地是巴基斯坦境内最大的沉积盆地,油气主要富集在白垩系受断裂控制的构造圈闭内,确定构造及演化特征对下一步油气勘探具有重要的意义.为此,依据地震资料,通过研究印度河盆地A区块白垩系的断裂及构造演化特征,分析圈闭成藏后的构造运动对油气藏保存的控制作用.研究认为:A区块经历了冈瓦纳大陆解体裂谷期、印度板块漂移期和板块碰撞期等3个主要演化时期,其中板块漂移期的拉张—走滑阶段是圈闭形成的主要时期;圈闭成藏后构造活动主要表现为整体抬升和沉降,上升盘同向断阶油气藏部分受到破坏,而上升盘反向断阶圈闭油气藏受构造活动影响不大,因此呈现出前者闭合度大、油气藏高度小,而后者油气充注度高的特点.新的地质认识为评价有利勘探目标指供了指导.