鄂尔多斯盆地西缘逆冲断裂带构造特征及油气勘探方向

对鄂尔多斯盆地西缘物探资料解释研究认为:秦祁贺三叉裂谷的形成和演化,是鄂尔多斯盆地西缘形成南北两大不同逆冲断裂带的主要原因。两个区域不整合面、两个滑脱面、两组断裂是油气长距离、大规模运移的主要通道。以南部逆冲断裂体系为主的四个区块,石油地质条件优越,油气资源丰富,圈闭类型多样,具有油气并举、深浅层并举、地层岩性圈闭与构造圈闭并举的有利条件,是鄂尔多斯盆地油气勘探的新领域和可能的大场面。主要勘探领域有三个:一是主滑脱面以上,各逆冲大断裂之间成排成带的中生界、上古生界构造群;二是主滑脱面以下在下古生界中形成的大型背斜构造;三是逆冲断裂带前缘带及前缘外带。

Structural Features and Oil-gas Prospecting Targets of Thrusting Fault Belt in Western Edge of Ordos Basin

Based on the interpretation of geophysical data in the western margin of Ordos Basin, it is suggested that the formation and evolution of tri-shaped rift formed by Qinling -Qilian -Helan mountains would be the main factor to form south and north large thrusting fault belts in the western edge of Ovdos Basin. The main pathway of oil-gas long-distance and large-scale migration consists of two regional unconformity interfaces, two detachment surfaces and two groups of faults. Four blocks mainly constituted by south thrusting fault system have relatively favorable petroleum geological condition, abundant oil-gas resources, diversified trap type, which are favorable to form both oil and gas reservoirs, distributed in both shallow and deep layers, as well as stratigraphic-lithologic trap and structural traps existence together. These blocks will become possibly new areas and main spectacle for petroleum exploration in Ordos Basin. The main exploration areas have been determined as followings: (1) Mesozoic and Upper Paleozoic tectonic clusters distributed above the major detachment surface, being in a row and strip between various big thrusting faults; (2) large anticline structure formed in Lower Paleozoic under the major detachment surface; (3) the front and its outer zones of thrusting fault belts.