试论库车前陆冲断带构造顶蓬效应

Discussion of Ceiling Effect in Foreland Thrust Belt of Kuqa Depression

塔里木盆地库车坳陷位于南天山山前,受新生代晚期强烈挤压作用控制,坳陷内广泛发育冲断构造。受冲断作用及盐岩变形的共同影响,库车坳陷内部形成一系列复杂构造样式。其中盐上构造层在挤压变形过程中形成了独具特色的"顶蓬构造",顶蓬构造的存在对于盐层、盐下层构造变形具有重要影响。综合运用地震资料、钻井资料,对于该类变形特征进行综合研究,研究表明:①库车前陆冲断带盐上构造层普遍发育顶蓬构造,在地表表现为克拉苏构造带及秋里塔格构造带2排线性褶皱带;②根据顶蓬构造要素可划分为错断型、褶皱型两大类,错断型具体可细化为对称错断型、单向错断型及叠置错断型,褶皱型则可划分为拱形及球形;③顶蓬构造具有顶蓬效应,具体表现为应力调整效应、减压效应及封盖作用,3种效应影响了库车前陆冲断带盐下构造层构造变形、储层演化及油气成藏,形成了库车前陆冲断带盐下油气富集区带。

Kuqa Depression of Tarim Basin is located in piedmont of the southern Tianshan Mountains. Ex-tensive thrust structures developed in the depression because of the intense extrusion in Late Cenozoic. Al-so, under the combined effects of thrust salt rocks deformation and rock salt deformation, the interior of Kuqa Depression formed a series of complex tectonic styles, among which, special ceiling structure formed in squeezing deforming process of structural bed on the salt bed. And the ceiling structure had great influ- ence on the tectonic deformation of both the salt bed and underlying bed. This kind of deformation struc-ture was studied in this paper through comprehensive seismic and drilling data. The results showed that： （1）The ceiling structures were common in the structural layer above the salt bed in the foreland thrust belt of Kuqa Depression, and correspond to two rows of linear folded belts in Kelasu and Qiulitager tectonic belts on the earth surface. （2）The ceiling structure could be classified into faulted type and folded type on the basis of structural elements, and the former could be subdivided into symmetrical faulted type, one-way faulted type and overlap faulted type, while the latter could be subdivided into arched type and spherical type. （3）The ceiling structure had ceiling effects, including stress adjustment, decompression effect and seal-capping, which had influenced the tectonic deformation, reservoir evolution and petroleum entrapment of the structure under the salt layer. Also,the ceiling structure was good for the accumulation of oil and gas in the foreland thrust belt of Kuqa Depression.