The research on fracture and structural trap of the Weixinan Sag, Beibuwan Basin, South China Sea

Abstract The Weixinan Sag in Beibuwan Basin is a pilot area of the offshore exploration and development integrated technology. The main oil bearing layers, one member of Liushagang formation and third member of Weizhou formation, develop many fracture systems and structural traps. The key factors of the offshore exploration and development integrated technology are"the fracture research"and "the effectiveness of structural trap". Fracture research includes the study of the geometry, dynamics, kinematics characteristics of fracture, and the division of fracture system. The effectiveness of structural trap include analogical studies on the structural characteristics of traps, quantitative studies on fault lateral sealability, fault vertical sealability, and prediction technology of oil column height. Comprehensive the relationship of the law of oil and gas distribution,the differential fracture system in the internal of the No. 2 fracture zone, and the effectiveness research of traps, fault-controlled reservoir laws and the dominant fault-controlled reservoir mode are obtained. The research on fracture and trap of offshore integrated exploration and development has been successfully applied in the Weixinan Sag. The 37 of 45 development evaluation wells have been drilled successfully and the drilling success rate is 82%. It has promoted the ODP implementation of 5 oilfields, the adjustment implementation of 8 oilfields and made important contribution to the increase of reserves and production in the Weixinan Sag.