Study on the Imaging Ability of Seismic Exploration to Subsurface Structures and Closed Pores of Hydrocarbon Accumulation

Abstract

This study demonstrates the ability of seismic exploration to image subsurface structures and closed pores where oil and gas accumulates through a three-dimensional tectonic interpretation of the Ohaji oilfield. In the study area, the Abada Formation is composed of vertically stacked reservoirs, with the thickness of the contrast interval ranging from 25 ft to 250 ft. Base configuration and tectonic movement were deduced from gravity measurements and the development of overlying Tertiary. The various stages of delta development were reconstructed with the help of well data. The petroleum geology characteristic of the delta is the occurrence of multiple reservoirs in the imbricated overlay cycle of offshore strata. The exploration direction in this area is an anticlinal dip closure (annealing trap) with high structural zones on the east and west wings. The northern area is composed of simple overturning structures which are widely distributed, while the growth faults are explained as the deep, overpressure and ductile Marine shale movement, and formed with the assistance of slope instability. The middle zone is dominated by fault tumbling anticline and the southern region is characterized by collapsed roof structure. Because of this complex tectonic model, the growth faults associated with anticlinal traps are segmented by normal faults, which become the potential problems of fault-sealing rupture and insufficient lateral and amplitude support of some reservoirs.