克拉苏构造带克深段构造特征及其石油地质意义

Structural Characteristics of Keshen Segmentation in Kelasu Structural Belt and Its Petroleum Geological Significance

克拉苏构造带克深构造段已发现了KL2、KS2、KS1等多个含油气构造,由于该段位于前陆冲断带,构造变形复杂,构造模型争论较大。在前人认识的基础上,结合地表露头、钻井资料,对克深构造段三维地震资料进行T—Q全层位解释,重新建立了该构造段构造解释模型并对该段石油地质特征进行研究。研究结果表明:克深构造段具有垂向分层、南北分带的变形特征,垂向上可分为盐上构造层、盐岩层、盐下构造层与基底构造层4层结构。该区域主要发育逆冲断层及相关褶皱、盐收缩构造及走滑构造3种构造样式,其中盐下构造层构造样式自北向南逐渐由高角度基底卷入构造样式转变为盖层滑脱构造样式。克深构造段现今构造主要形成于新生代中晚期,经历了二叠纪晚期—三叠纪前陆盆地、侏罗纪—白垩纪坳陷盆地、古近纪—中新世弱收缩挠曲盆地及上新世—第四纪陆内前陆盆地4个演化阶段。勘探实践表明,该区带具有好盖层、厚储层、大构造、强冲注、晚成藏等有利条件,是库车山前天然气勘探的重要目标。

A number of oil and gas structures were found in Keshen structural segmentation of Kelasu structural belt, such as KL2, KS2 and KS1. The structural model is under argument because this segmentation is located in the foreland thrust belt with complicated structural deformations. Based on the previous understanding and with the help of surface outcrop and drilling data, a T-Q full level interpretation was made on 3D data of Keshen segmentation. The structural interpretation model of this structural segmentation was re-established to study the petroleum geological characteristics of this segmentation. The research results indicated that deformation characteristic of Keshen structural segmentation is vertically layered and south-north division of belts. It is vertically divided into four structural layers - suprasalt layer, salt layer, subsalt layer and basement layer. There are three main structural patterns developed in this area, such as thrust fault with the related folds, salt contractive structure and strike-slip structure. Of those, the structural pattern of subsalt layer is gradually turned into cap decollement structural pattern from high-angle basement curled structural pattern from the north to the south. The present-day structure of Keshen segmentation was shaped mainly in the middle and late periods of Cenozoic era and experienced four development stages, such as Late Permian-Triassic foreland basin, Jurassic-Cretaceous sag basin, Paleocene-Miocene weak contractive flexure basin and Pliocene-Quaternary intra-continental foreland basin. The practice of exploration showed that this area, with favorable conditions of good cap-rock, thick reservoir, large structure, strong injection and late accumulations, was the important target for foothill natural gas exploration in Kuqa Depression.