Strike-Slip Transfer Zone and Its Control on Formation of Medium and Large-Sized Oilfields in Bohai Sea Area

Tan-Lu strike-slip fault in Bohai sea area is an important hydrocarbon enrichment zone. But it is not clear whether strike-slip transfer zone controls on the formation of medium and large-sized oilfields. This paper systematically analyzes the Tan-Lu strike-slip transfer zone and its control on the development of medium and large-sized oilfields on the basis of detailed interpretation of 400 wells and 3-D seismic data over the fault zone. Three types of transfer zones developed in the Tan-Lu strike-slip fault zone are recognized according to the position of the transition zone in the strike-slip fault zone, which are named as fault-edge transfer zones, fault-overlap transfer zones and fault terminal transfer zones respectively. These transitions can be further divided into seven types, which are sigmoid, overlapping, duplex, broom-like, shingled, conjugated and compound types of transfer zones. According to the local stress state, each type of transfer zone is further subdivided into contractional and extensional types of transfer zones. Contractional transfer zones control the formation of large-scale traps, whereas extensional transfer zones control the formation of small-scale traps. Geological oil reserves related to contractional transfer zones account for up to 81% of total geological oil reserve of the Tan-Lu strike-slip fault zones. Therefore, contractional transfer zones developed in the strike-slip fault zones should serve as excellent exploration targets for the large-scale oilfield with great potential.