SALT-RELATED STRUCTURES AND FAVORABLE HYDROCARBON TRAPS IN THE KUQA DEPRESSION
YU Yixin1,2, TANG Liangjie1,2, YANG Wenjing3, CHEN Shuping1,4, PENG Gengxin3 and LEI Ganglin3(1. Key Laboratory for Hydrocarbon Accumulation Mechanism of Education Ministry, China University of Petroleum, Beijing 102249, China; 2. Basin and Reservoir Research Center, China University of Petroleum, Beijing 102249,China; 3. Research Institute of Petroleum Exploration and Development of Tarim Oilfield, Korla, Xinjiang 841000,China; 4. Department of Earth Science, China University of Petroleum, Beijing 102249, China)
Comprehensive data from field observations, drilling wells and seismic profiles have demonstrated that the Paleogene Kumugeliemu Fm. and Neogene Jidike Fm. attain thick halite layers in the Kuqa depression of the northern Tarim basin, NW China. Driven by the buoyancy, gravity spreading, differential loading and compressional stresses, the salt bodies experienced viscous flowage, resulting in spatial distribution features for the circum-Baicheng sag and thickening in the Kelasu and Qiulitage structural belts with the maximum thickness of 4000m. The viscous flow of salt sequences influenced the structural distortion of the halite layers and overburden. Consequently, many salt-related structures, such as salt pillows, salt walls, salt nappes, fish-tails, salt welds (fault welds), salt stacks, pop-ups and salt-withdrawal sags, have developed well in the Kuqa depression. The salt-related structures had exerted important influence on the hydrocarbon migration and accumulations. The structural and subtle traps induced by the salt structures offered abundant favorable space for hydrocarbon accumulation, the faults acted as the favorable pathways for hydrocarbon migration and the thick halite layers served as good regional seals for hydrocarbon preservation. The forming models of hydrocarbon accumulation are different in the sub-salt, salt and supra-salt in the Kuqa depression. The integrated analysis shows that the favorable exploration objectives include the sub-salt anticlinal traps, footwall fault traps sealed by reverse faults, stratigraphic-lithologic traps, mid-salt structural-stratigraphic traps and supra-salt anticlinal traps.