塔北哈拉哈塘地区剪切断裂系统构造特征及其对油气分布的控制

塔北哈拉哈塘地区发育多组北东、北西向主干断裂组成的剪切断裂系统, 本文在剪切断裂地球物理识别的基础上, 分析了研究区内剪切断裂系统构造特征及其对油气分布的控制.研究区内剪切断裂发育9种典型构造样式.平面上, 整体为共轭剪切断裂, 分支断裂延伸较短, 与主干断裂呈小角度相交; 单条剪切断裂带具有一定的分段性, 不同部位具有不同的构造样式和平面组合.纵向上, 哈拉哈塘地区剪切断裂系统具有分层变形的特征, 可以划分为下、中、上3个构造层.下构造层为寒武系-奥陶系, 为纯剪作用下形成的共轭剪切断裂系统; 中构造层为志留系-二叠系, 为受下构造层控制的张剪作用下形成的断裂; 上构造层为三叠系及其以上地层, 为受中下构造层控制的张剪作用下形成的雁列式分布的正断层.这种分层变形特征主要受控于区域古构造应力场的变化.哈拉哈塘地区剪切断裂系统的构造特征决定了该区油气分布具有"多层系含油、沿断裂富集"的特征.

Structural features of shear fault system and its control on hydrocarbon distribution in Halahatang area,North Tarim Basin

There are several groups of shear fault systems consisting of NE and NW main faults in Halahatang area, North Tarim Basin. The shear fault systems control the distribution of oil reservoirs. Based on the geophysical identification of shear fault, this paper analyzes the structural features of the shear fault system and its control on hydrocarbon distribution in the study area. Nine kinds of typical structural styles of shear fault are founded. On the plane, the shear fault system is conjugate shear fracture like chessboard, and branch faults which extend short show a small angle to the main faults. Single shear fault has segmentation, so different parts have different structural styles and plane combination. Vertically, shear fault system has a hierarchical deformation characteristic in study area, which can be divided into three tectonic layers: Lower structural layer, middle structural layer and upper structural layer. The lower structural layer consists of Cambrian-Ordovician stratas, which are conjugate shear fault systems formed by pure shear. The middle structural layer consists of Silurian-Permian, which are normal fault systems by tensional simple shear force controlled by lower structural layer. The upper structural layer consists of Triassic strata and above, which are normal faults of en echelon distribution by tensional simple shear force controlled by lower and middle structural layers. The characteristic of stratified deformation in the study area is controlled by change of paleotectonic stress field. The structural features of the shear fault systems in Halahatang area determine the oil and gas distributes among multiple layers and concentrates along faults.