Sequence stratigraphy, structural framework and hydrocarbon migration of Ariki Field, Nigeria

Abstract: The structural framework and stratigraphy of the Ariki Field in the Western Shallow Offshore Depobelt, Niger Delta Basin, Nigeria are interpreted using well logs and 3-D seismic data, and the control of rift on hydrocarbon accumulation is analyzed. Five maximum flooding surfaces and five sequence boundaries are identified in the major reservoir succession of Agbada Formation in the field; and the structural framework of the field is controlled by the major growth faults, minor faults and rollover anticlines formed by synsedimentary tectonic movements. There are a total of seven faults identified across the field, including three major faults and four minor faults. On the western flank of the field, graben and horst-like structures were bounded by minor faults. Fault throw analysis shows that below 1800 ms, the major faults with large fault throws act as hydrocarbon migration pathways, while above 1 800 ms, faults with small throws act as seals of hydrocarbon traps. There are four-way dip rollover anticlines and three-way downdip traps created by the minor faults. Six other prospective traps (drilling targets) were identified, which have promising oil accumulation potential. Key words: Niger Delta, Ariki Field, sequence stratigraphy, structural framework, hydrocarbon migration and accumulation, rollover anticline, fault sea