THE CHARACTERISTICS OF STRUCTURAL STYLES AND THEIR INFLUENCES ON OIL AND GAS ACCUMULATION OF THE WAN'AN BASIN IN THE SOUTHWESTERN SOUTH CHINA SEA

The paper described the characteristics of main tectonic movements and structural styles in each structural layer in the Wan'an basin in detail.Three tectonic movements including the Cretaceous Lile movement,the Middle Late Eocene Xiwei movement and the Late Miocene Wan'an movement occurred in the basin.The earlier Lile movement resulted in the basin's embryonic tectonics,the later Xiwei movement caused expansion of the continental margin fault depression,and the latest Wan'an movement lead to the former strata folded,block faulting,denuding and structural inversion.Most structural traps were formed in the latest movement.With occurring of main tectonic movement,there are three suites of tectonic layer in the basin,i.e.basement layer(under T₅ or Tg),principal layer(between T₃ and T₅)and superficial layer in which various characteristics structural styles have been developed.In terms of hydrocarbon accumulation,the principal layer is the habitat due to its wide development of structural traps.