Study on the features of fault controlling pool in Nanpu Depression, Bohai Bay Basin

There are large amount of faults in Nanpu depression which is a Cenozoic hydrocarbon rich depression in Bohai Bay Basin, and a large number of pools accumulated around faults. Assemblage styles of fault both in plane and section were analyzed in this paper. Faults of Nanpu depression can be classified into four styles in plane: parallel, interlaced, pectinate, and fastigiated style; three fault assemblages in section including complex "y", flower structure and ladder pattern. According to the analysis of distribution of faults, sand bodies and hydrocarbon reservoirs, it has been found that concave of second to third order growth faults are the principal orientation of oil migration, where thick and high porosity and high permeability reservoirs were obtained. Down-dip block of contrarotation faults and upfaulted block of homodromous faults are the favorable oil accumulation locations. Fault zone can be divided into three parts: up-induction-fracture, middle crush, and down-induction-fracture zone. The up-induction-fracture zone owns higher permeability than down-induction-fracture, so the former is favorable place of oil migration and the latter inclines to be plugged zone.