非洲S盆地双层断裂体系的重力场反映与识别

Mirroring and recognition of gravitational field of double-layered fault system in the African S basin

非洲S盆地是西非Iullemmeden盆地东南边缘的一部分,现有地质资料认为S盆地是一个向西南倾斜的单斜盆地。为初步查明该盆地的地质构造格架为评价盆地的含油气潜力提供依据,在S盆地展开了1∶5万重磁调查。本文依据盆地的实测重力数据及已有地质资料,进行了数据处理与解释推断,在研究盆地不同深度空间的重力异常时发现,S盆地具有上下两层断裂系统:下层为一套控制盆地形成与发育的近南北向的基底断裂系统,是西非裂谷系一系列近南北向的地堑式盆地的组成部分;上层为一套有北东向与北西向断裂共同组成的盖层断裂系统(部分运动强烈的切入基底),这套断裂决定了盆地的最终形态并控制着油气流的运移通道和储存空间。

The African S basin is a part of the southeast fringe of the lullemmeden basin in west Africa. Available geological data indicated that it is a monoclinic basin dipping southwest. In order to find out the geological structure outline and the potential of oil and gas in the basin, 1 ： 50000 gravitational and magnetic survey was conducted in the S basin. Based on measured and accessible geological data on the basin, this paper performed data processing, interpretation and inference, and found during studying gravitational anomalies in different depths of the basin that the S basin has two layers of fault system： the lower layer is a nearly south-north basement fault system that controls the formation and development of the basin, being a part of a series of the nearly south-north graben-like basins in the west African rift system; the upper layer is a cover fault system composed of NE- and NW-trending faults （partly violently cutting into basement）, which decided the final form of the basin and controlled the migration passage and storage space of oil and gas flow.