塔北隆起轮南低凸起断裂构造特征与形成演化

轮南低凸起是塔里木台盆区油气勘探的重点地区,发育一系列受控于断裂的缝洞型油气藏。目前对该区断裂研究多是针对某一区块的研究,亟需进行全区系统梳理。基于轮南低凸起大量三维地震资料,采用断裂构造解析方法,开展研究区断裂类型、构造特征与形成演化分析。结果表明:轮南低凸起发育逆冲断裂、走滑断裂、张扭断裂3类断裂。逆冲断裂分布在研究区西北部、中部轮南地区,既有沿层滑脱型,也有基底卷入型逆冲断裂。走滑断裂是研究区主要的断裂类型,剖面上表现为高陡直立、正花状、半花状3种构造样式,平面上发育线性延伸、棋盘格式、辫状构造、马尾状构造4种构造样式,沿走向具有明显的分段性。张扭断裂主要分布在上古生界、中-新生界,断裂规模较小,剖面上呈阶梯状、堑垒式或负花状,平面上大多沿深层走滑断裂、逆断裂呈雁列式、斜列式展布。利用断层上下构造样式差异、卷入断裂构造变形地层时代、生长指数3种方法分别判定走滑断裂、逆冲断裂、张扭断裂活动期次,揭示研究区断裂演化主要经历中加里东期、早海西期、晚海西-印支期、燕山-早喜马拉雅期4期演化,断裂演化具有一定的继承性。

Structural characteristics and evolution process of faults in the Lunnan low uplift,Tabei Uplift in the Tarim Basin,NW China

The Lunnan low uplift of the Tabei Uplift is a hotspot for oil and gas exploration in the Tarim Basin,in which a series of fractured-vuggy oil and gas reservoirs controlled by faults are found.At present,the faults in the study area are mostly studied in a certain block,which needs to be systematically hackled in the whole study area.Based on a large number of three-dimensional seismic data,the method of fault structure analysis is adopt⁃ed to analyze the types,structural features,and formation and evolution processes of faults in the study area.The results show that:There are three types of faults,such as reverse faults,strike-slip faults,and transten⁃sional faults.The reverse faults are distributed in the northwest of the study area and central Lunnan areas.There are both detachment thrust faults and basement-involved thrust faults.Strike-slip fault is the main fault type in the study area.Three kinds of structural styles are developed on the profile,which are high-steep style,positive flower,and semi-flower.Four kinds of structural styles are developed on the plane,which are linear ex⁃tension,chess board format,braided structure,and horsetail structure.The strike-slip fault has obvious seg⁃mentation along the strike.The transtensional faults are mainly small,which are distributed in the Mesozoic and Cenozoic.The transtensional faults are stepped,grabbed or negative flower on the profile.On the surface,most of them are arranged in the form of en echelon along the strike-slip faults or the reverse faults.Three methods are used to reveal the evolutionary history of strike-slip faults,reverse faults,and transtensional faults respec⁃tively,which are the differences of upper and lower fault structure styles,the age of strata deformed by faults and growth index.The faults have undergone 4 stages,which are the middle Caledonian,the early Hercynian,the late Hercynian-Indochina,and the Yanshan-early Himalayan.The fault evolution has certain inheritance.