库车坳陷古隆起与盐构造特征及控油气作用

依据钻井和地震资料,在库车坳陷识别出却勒、大北—吐北、克拉苏、依奇克里克和吐格尔明等古隆起以及盐枕、盐推覆、盐墙等盐构造。这些古隆起和盐构造主要分布于克拉苏—依奇克里克构造带和秋里塔格构造带,并都经历了复杂的形成演化过程,两者关系也非常密切。古隆起决定了盐构造的发育位置和形成过程,盐体一般在古隆起顶部发生聚集增厚,形成盐枕和盐墙构造,并在古隆起两翼盐体减薄处形成盐焊接和鱼尾构造等。古隆起和盐构造对库车地区的油气聚集分布起着重要的控制作用,古隆起的发育不仅有利于改善储层质量,其本身也是油气运移的优势指向区,巨厚膏盐层的存在也为油气聚集提供了极好的封盖作用。另外,古隆起和盐构造的叠加构造变形为油气聚集提供了丰富的构造圈闭和隐蔽圈闭,形成的断裂和不整合也构成了有效的油气输导体系。

Paleo-Uplifts and Salt Structures and Their Influence on Hydrocarbon Accumulations in the Kuqa Depression

Based on well and seismic data, some paleo-uplifts and salt structures have been identified in the Kuqa depression. The Quele, Dabei-Tubei, Kelasu, Yiqikelike and Tugerming paleo-uplifts are located in the Kelasu-Yiqikelike and Qiulitage structural belt, as well as salt pillows, salt nappes and salt walls. The development of salt structures has very close relationships to the paleo-uplifts because the paleo-uplifts exerted important influences on the spatial distribution of salt thickness. Usually, salt bodies thickened on the middle top of basement paleo-uplifts and then formed salt pillows and salt walls, yet salt-weld and salt-fish structures commonly developed in the regions adjacent to the limbs of the paleo-uplifts where the salt thickness obviously declined, resulting from the viscous flowage of salt. In the Kuqa depression, the basement paleo-uplifts and salt structures have governed the hydrocarbon accumulations in that the paleo-uplifts can improve the reservoirs, can be the favorable areas for hydrocarbon migration and thick halite layers also afford very good seals for hydrocarbon preservation. In addition, the structural distortion of paleo-uplifts and salt structures formed many structural and subtle traps, and the faults and unconformities can form good hydrocarbon pathway systems.