Structural features of shear fault system and its control on hydrocarbon distribution in Halahatang area, North Tarim Basin
Ma Debo1,2, He Dengfa2, Tao Xiaowan1, Zheng Duoming3, Xing Xiang1, Xia Weijie3, Qiu Zhen1
1. PetroChina Research Institute of Petroleum Exploration and Development, Beijing 100083;
2. School of Energy Resources, China University of Geosciences, Beijing 100083;
3. Exploration & Development Institute, Tarim Oil Field Company, PetroChina, Korla, Xinjiang 841000
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.