库车前陆冲断带构造分层变形特征

Layered Structural Deformation Characteristics of Kuqa Foreland Thrust Belt

库车前陆冲断带地震资料信噪比低,具有多解性。利用高分辨率三维地震、钻井、油气分析化验等资料,对库车前陆冲断带地层组合进行系统描述,精细解释构造模型,深入剖析油气成藏体系,认为库车前陆冲断带发育古近系和新近系膏盐岩层及三叠系和侏罗系煤层2套滑脱层,具有分层滑脱、垂向叠置、多期变形的特征,浅层构造发育盖层滑脱褶皱,深层发育基底卷入式叠瓦状逆冲构造,膏盐岩层和煤层发生滑脱塑性变形,发育加里东运动期、海西运动晚期—印支运动期和燕山运动期—喜马拉雅运动期3期断裂,海西运动晚期—印支运动期构造控制中生界沉积,由北向南具有超覆减薄的特征。库车前陆冲断带分层构造变形控制油气分层运聚,煤层以上的油气主要来自侏罗系烃源岩,煤层之下的油气主要来自三叠系,三叠系烃源岩生烃量占60%,大量油气仍保存在煤层之下。

The seismic data acquired from Kuqa foreland thrust belt is characterized by low signal-to-noise ratio and high interpretive ambiguity.By using high-resolution 3D seismic data,drilling and lab hydrocarbon analysis data,the stratigraphic assemblages of Kuqa foreland thrust belt were systematically described,the structural model was detailedly interpreted,and the hydrocarbon accumulation system was deeply analyzed.It is found that the Kuqa foreland thrust belt develops two sets of detachment layers:Paleogene and Neogene gypsumsalt rocks,and Triassic and Jurassic coal measures,all of which feature stratified detachment,vertical stacking,and multiphase deformation.Detachment folds in caprocks are found in the shallow structures,while basement-involved imbricate thrust structures are developed in deep strata.Detachment plastic deformation occured in the gypsum-salt and coal layers.Faulting occured in three phases including Caledonian,late Hercynian-Indosinian,and Yanshanian-Himalayan.The late Hercynian-Indosinian tectonics controlled the Mesozoic sedimentation,showing a north-to-south onlap thinning feature.Layered structural deformation in the Kuqa foreland thrust belt governs the stratified accumulation and migration of hydrocarbons.Hydrocarbons in the strata above the coal seam predominantly originated from the Jurassic source rocks,whereas oil and gas in the strata below the coal seam mainly came from the Triassic source rocks which contributs 60%of the hydrocarbons.A substantial quantity of hydrocarbon remains trapped in the formation below the coal layer.