阿姆河盆地别什肯特坳陷及其邻区构造成因与勘探意义

Genetic mechanism and exploration significance of tectonic action in the Bieshikent Depression and its adjacent area in the Amu-Darya Basin

构造运动对中亚地区阿姆河盆地别什肯特坳陷及其邻区油气的分布具有重要的控制作用,但过去对该区构造的成因机制研究较少,制约了该区的油气勘探进程。为此,通过地震资料构造解释与区域平衡剖面分析,结合钻井与油气藏特征,研究了该区构造演化及其对油气分布的影响。结果表明:该区构造变形具有东强西弱的分带性和盐膏岩层上下构造的分层性特征,二叠纪—三叠纪的伸展构造运动发育了基底断块和古隆起,古近纪以来的挤压构造运动形成了基萨尔褶皱隆起区和别什肯特前陆坳陷,挤压应力场自基萨尔山向前陆坳陷方向逐渐减弱,并具有右旋压扭特征。挤压构造运动使别什肯特坳陷和基萨尔褶皱隆起区发育了以挤压背斜、逆冲断裂背斜和断鼻为主的构造圈闭,形成的大量构造裂缝改造了碳酸盐岩储层,使基萨尔褶皱隆起区北部盖层遭到破坏。在此基础上,明确了该区的油气勘探方向,认为在别什肯特坳陷与基萨尔褶皱隆起区应以寻找断背斜构造圈闭为主,被改造的古隆起区及两期断裂相交部位则是最为有利的油气勘探区。

Tectonic movement plays a key role in controlling hydrocarbon distribution of the Bieshikent Depression and its adjacent ar eas in the Amu-Darya Basin. However, a poor understanding of the genetic mechanism of structures impedes petroleum exploration there. Through structural interpretation with seismic data and regional balanced section analysis and in combination with drilling data and reservoir characteristics, this paper studied the tectonic evolution and its impacts on hydrocarbon distribution in the study area. The following conclusions were obtained. The tectonic deformation there are featured by the zonation of being strong in the east and weak in the west and layering above and below evaporate beds. The Permo-Triassic extensional tectonic movement led to the develop- ment of basement fault blocks and paleohighs, while the post-Paleogene, compressional tectonic movement led to the formation of Ji- saer folded uplift and Bieshikent foreland depression. The compressive stress field became weakened gradually from the Jisaer Moun- tain to the foreland depression, and had dextral compresso-shear characteristics. The compressive tectonic movement resulted in the formation of structural traps dominated by compressive anticlines, overthrust anticlines and fault noses in the Bieshikent Depression and Jisaer folded uplift zone. A large amount of tectoclases modified the carbonate reservoirs and destructed the seals in the northern part of the Jisaer folded uplift zone. On this basis, it is believed that exploration should focus on the faulted anticlinal traps in the Bieshikent Depression and Jisaer folded uplift zone, and that the modified paleohighs and the intersection areas of two-stage faults be most favorable for oil and gas exploration.