塔里木盆地东秋里塔格构造带构造特征及其油气地质意义

Structural features of the eastern Qiulitage Tectonic Belt and petroleum geological significance

位于库车坳陷中部的东秋里塔格构造带是库车前陆冲断带的前缘,该构造带东段的迪那2凝析气田是我国目前发现的规模最大的整装凝析气田,含气层位为渐新统苏维依组与库姆格列木群,但构造带中西段的东秋5井、东秋6井、东秋8井在古近系目的层都勘探失利。对该地区构造样式认识上的分歧,地质认识不统一制约了该地区的油气勘探进程。研究以最新处理的三维地震资料为基础,结合二维地震资料,以前陆盆地构造冲断带和断层相关褶皱理论为指导,建立合理的构造模式。通过三维地震精细解释,发现在东秋里塔格构造带西段膏盐岩下发育双重逆冲构造,它的顶板逆冲断层和浅层发育的相同倾向的逆冲断层在吉迪克膏盐岩地层中可能重合,从而引起侏罗系—三叠系的油气向上逸散直至地表。同时,膏盐岩层下构造层中发育多排北倾逆冲断层以及相关构造样式,在2套膏盐岩层叠置并发育叠瓦扇构造和断层相关褶皱的区域,具有重要的勘探潜力。

The eastern Qiulitage tectonic belt is the front of the Kuqa foreland thrust belt in the middle of the Kuqa Depression.Dina 2 gas field,the largest unitization condensate gas field in China so far,was discovered in the east of the tectonic belt.The gas-bearing layers are the Oligocene Suweiyi Formation and Kumugeliemu Group.However,three wells,Dongqiu 5,Dongqiu 6 and Dongqiu 8,in the middle and west of the structural belt failed to explore in the Paleogene target formations.The differences in the understanding of the tectonic pattern and geology restrict the oil and gas exploration process in this area.Based on the newly-processed 3 Dseismic data and 2 Dseismic data,we establish reasonable structure models in this study with the guidance of the tectonic thrust belt and fault-related fold theory of the foreland basin.Through fine seismic interpretation,we find that the presalt develop duplex thrust structure in the west section of the eastern Qiulitage tectonic belt.The roof thrust may coincide with the shallow thrust fault of the same dip in gypsum-salt layer of Jidike Formation,which may cause the oil and gas of Jurassic-Triassic to escape to the surface.Meanwhile,we find a series of north-tilting thrust faults and related structures under gypsum-salt formation of Neogene.These zones where two sets of gypsum salt rocks overlap,the imbricate fan and fault-related fold develop have a significance exploration potential.