柴达木盆地断裂系统特征与油气勘探战略方向

基底断裂格局决定了盆地构造演化和沉积发育,导致了北缘、中部和昆北3个各具特色的断裂构造系统。北缘断裂构造系统平面上以反S展布、剖面上以一系列北倾南冲的逆冲断层带及其所控制的同沉积构造呈阶梯向南下掉为特点,受北部祁连山构造应力系统的作用;南部昆北断裂构造系统发育压陷断槽和断阶带,受南部昆仑山构造应力系统的作用;中部断裂构造系统以两断夹一隆的冲起构造为特色,同时受祁连山和昆仑山构造应力的共同作用。断裂对油气藏的形成和分布有重要的控制作用,表现在对烃源岩、储集条件、圈闭形成及油气运聚等方面。依据断裂控烃特征并针对柴达木盆地的具体情况,柴达木盆地油气勘探应迅速转移到盆地腹地即中部断裂构造系统区,尤其是鄂博梁Ⅱ号一伊克雅乌汝、鸭湖—台吉乃尔构造带和中南隆起区,有望取得重大突破。 

THE FAULT SYSTEM CHARACTERISTICS AND HYDROCARBON EXPLORATION STRATEGY IN QAIDAM BASIN

The base fault pattern of the Qaidam Basin determined the basin's tectonic evolution and its sedimentary development, and resulted in 3 distinguishing fault structure systems of the north edge, the middle and the Kunbai. The north-edge fault system shows a anti-S shape in plane, and in section the fault system displays a series of reverse fault belts having a south-dip direction and lining many syndepositional structures like steps controlled by the fault system. They are effected by Qilan mountain tectonic stress field on the north. The Kunbei fault system are composed of some press fault-depressions and fault-step belts in the south of the basin. Its formation is controlled by Kunlun mountain tectonic stress field on the south. The middle fault system has a common structure of a swelling press form both side faults as its important feature. It is effected by two stress fields of Qilan mountain and Kunlun mountain in the same period. The faults play very important roles in hydrocarbon accumulation and distribution. It was pointed out that future hydrocarbon exploration in the basin is the middle part-middle fault structure system according to the fault controlling law on hydrocarbon accumulation in the basin and its petroleum geologic conditions, especially the Ebonang-Yikeyawuru, Yahu-Taijnail tectonic belts and middle-south swelling region. Petroleum exploration of the Qaidam Basin may make a huge breaktrough in these areas.