川东涪陵地区15号走滑断裂带几何学、运动学特征及演化过程研究

Geometry,kinematic characteristics and evolution of No.15 strike-slip fault zone in Fuling area,eastern Sichuan

四川盆地中部及北部发育多条北西向隐伏走滑断裂带,近年的油气勘探实践逐渐揭示出走滑断裂带对海相碳酸盐岩储层有一定的控制作用。为进一步深化对此类断层几何学、运动学特征及演化过程的研究,本文以川东涪陵地区15号走滑断裂带为例,基于最新处理的三维地震资料,分析不同构造层的变形特征及断裂-构造样式。基于断裂带两侧地层厚度变化规律及时间切片技术分析走滑作用方向、厘定走滑位移量,最终联系构造变形事件阐述隐伏走滑断裂带演化过程。研究表明:15号走滑断裂带在基底-寒武系盐下构造层主要为近于直立的单条断裂,平面上呈线状展布;在中下寒武统—奥陶系构造层表现为弱压扭性质,分支断裂在顶部发育,压隆段宽度较窄;志留系—下三叠统盐下构造层分支断裂最为发育,表现出正、负花状构造样式,平面上为雁列式展布。根据运动学分析结果,走滑断裂带经历了加里东中晚期右行走滑、海西晚期同沉积活动及晚燕山—早喜山期左行走滑3个主要的演化阶段。研究成果对深化川东涪陵地区走滑断裂带研究具有重要指导意义,同时可为四川盆地范围内走滑断裂带发育区储层影响因素及油气成藏条件等相关研究提供借鉴。

There are many NW-trending hidden strike-slip faults in the central and northern Sichuan Basin,and their control on the carbonate reservoirs is revealed by the recent oil and gas explorations.In order to better understand the geometry,kinematic characteristics and evolution of such faults,the No.15 strike-slip fault in Fuling area,eastern Sichuan is investigated to determine the deformation characteristics and fault structure styles of different structural layers using the latest processed 3D seismic data.Based on the temporospatial variation patterns of stratum thicknesses on both sides of the strike-slip fault,the mechanism of strike slip faulting is analyzed,and the strike slip displacement is determined.Finally,the evolution of the hidden strike-slip fault zone is described in combination with the tectonic deformation events.The structural layer of No.15 strike-slip fault below the Cambrian salt is mainly a single vertical fault with linear distribution on the plane,showing weak compressive torsional strength in the middle-Lower Cambrian to Ordovician with the development of branch faults at the top and a narrow pressure uplift section.The branch faults are most developed in the structural layer below the Silurian to Lower Triassic salt,with positive and negative flower-like structural styles with echelon distribution on the plane.According to kinematic analysis,the strike-slip fault experienced three main evolutionary stages:right strike slip in the middle-late Caledonian,synsedimentary activity in the late Hercynian,and left strike slip in the late Yanshanearly Himalayan periods.The research results provide a basis for in-depth studies of the strike-slip faults in Fuling area,and a reference for the study of reservoir control models and oil and gas accumulation in strike-slip faults in general.