库车褶皱冲断带东秋里塔格位移转换构造及其演化--兼论侧断坡相关背斜构造圈闭的形成

库车褶皱冲断带东秋里塔格构造带发育与侧断坡有关的位移转换构造.东秋里塔格冲断层是一条北倾盲冲断层,其错移地层自西向东逐渐降低,从东秋5井以西的新近系膏盐岩转换至迪那201井的古近系膏盐岩再到迪那11井的侏罗系煤系,地震剖面上侧断坡形态清晰.侧断坡东、西断坪分别是新近系吉迪克组膏盐岩和侏罗系煤系,侧断坡发育在煤上-盐下构造地层组合中.通过DQ99-196、DQ00-226、DQ00-263等构造演化剖面恢复计算,东秋里塔格构造盐上地层位移梯度向西约为103.72m/km,而盐下东秋-迪那段的位移梯度为61.65m/km.在上述地震剖面上,盐上背斜和盐下隐伏背斜的轴线位置发生了相对变化,后者自东向西逐渐向南发生偏移;野外露头观察,盐上背斜的褶皱作用也随之向西增强.在走向上,东秋里塔格构造具有构造分段性,表明侧断坡的位移量变化具有突发性.西段为库车塔吾构造,东段为东秋-迪那构造.库车塔吾构造的盐下隐伏背斜是受东秋里塔格冲断层控制的断层相关褶皱,前、后断坪分别位于吉迪克组膏盐岩和侏罗系煤系,其隐伏的构造楔与南秋里塔格背冲断层组成库车塔吾三角带.东秋-迪那构造的隐伏背斜样式与库车塔吾段相似;但南翼缺乏背冲断层,不具备三角带形态.磷灰石裂变径迹测年表明,侧断坡的发育过程最早可以追索到康村期.东秋里塔格侧断坡相关背斜的形成与自北向南的盲冲断层和区域左行扭压复合作用有关.侧断坡相关背斜的主要构造特征是由侧断坡调节上、下滑脱层之间的应变差异,同时作为油气运移通道沟通气源岩和储层;其油气勘探意义是使得煤系烃源岩生成的天然气向上运移到侧断坡相关背斜构造圈闭如迪那2之中聚集成藏.

Eastern Qiulitag Displacement Transfer Structure and Its Evolution in the Kuqa Fold-Thrust Belt, Tarim Basin: Discuss Concurrently the Trap-Forming of Lateral Ramp-Related Anticline

In the Kuqa fold-thrust zone, a lateral ramp-related displacement transfer structure is developed in the eastern Qiulitag structural belt. The strata broken by the eastern Qiulitag thrust, a north-dipping blind thrust fault, gradually decline from east to west, that is, Neogene salt and gypsum rocks west of Well Dongqiu 5 are transformed into Paleogene salt and gypsum rocks in Well Dina 201, and then into Jurassic coal measures in Well Dina 11, which is very distinctly delineated in the seismic cross section. The eastern and western fault flat is respectively in the Neogene salt and gypsum rocks of the Jidike Formation and in the Jurassic coal measures, and a lateral ramp is developed in a combined structure with coal in the upper and salt in the layer position. The recovery of structural evolution sections such as DQ99-196, DQ00-226, DQ00-263, indicates that the displacement gradient of the salt-in-the-upper-part stratum is around 103.72 m/km in the eastern Qiulitag structural belt, while that of the salt-in-the-lower-part stratum is about 61.65 m/km in the eastern Qiulitag-Dina subsection. On the above seismic sections, the positions of the axial lines of the salt-in-the-upper-part anticline and those of the salt-in-the-lower-part hidden anticline are relatively changed: they deviate southwards from east to west in the latter case. Besides, the outcrops show that folding is enhanced westwards in the salt-in-the-upper-part anticline. The structural subsection of the eastern Qiulitag structure in the strike direction suggest that sudden displacement of the lateral ramp divides it into two sections: the western section is named the Kuqatawu structure and the eastern section is called the eastern Qiulitag-Dina structure. The salt-in-the-lower-part anticline in the Kuqatawu structure is a kind of fault-related fold, which is controlled by the eastern Qiulitagh thrust, and the anterior and posterior fault flat is in salt and gypsum rocks of the Jidike Formation and Jurassic coal measures. The hidden structural wedge and the southern Qiulitag back-thrust constitute the Kuqatawu triangle zone. The hidden anticline in the eastern Qiulitag-Dina sector has a similar style as that of the Kuqatawu section, but there fewer back-thrust faults on its southern with no triangle zone. The dating age of the apatite fission track of the eastern Qiulitag structural zone shows that the lateral ramp can be traced back to the Kangcun Period. The formation of the lateral ramp-related anticlines in the eastern Qiulitag belt are related with a combination of two associated parts: a blind thrust from north to south and regional sinistral shear-compression. The main characteristics of the lateral ramp-related anticline are that the lateral ramp can adjust the strain differences between the upper and lower slip layers and serves as a channel of hydrocarbon between source rocks and reservoirs. In this way, gas can move from coal source rocks up to lateral ramp-related anticline traps. That is the case of the Dina 2 gas pool.