Sequence stratigraphic interpretation of Middle–Late Miocene successions of OMAH–1 well Offshore Niger Delta, Nigeria

Sequence stratigraphic analysis provides indications of depositional systems and specific cycles of sedimentation. Such studies are useful for the prediction of quality and geometry of reservoir systems. Ditch cuttings and Well log data recovered from the Middle-Late Miocene “OMAH-1 Well”, Offshore Niger Delta, Nigeria were analysed in order to have a proper understanding of rock units’ relationships with chronostratigraphy and depositional environment-significant forms. Results of paleobathymetry of the deposits using benthic foraminifera ranged from coastal deltaic to shallow marine (shallow inner neritic, inner neritic and middle neritic) settings. Two foraminiferal zones and four palynological zones indicative of Middle–Late Miocene age was identified. Four (4) sequence boundaries (SBs) were identified and dated: SB 1 at 7250 ft. dated 10.6 Ma, SB 2 at 6530 ft. dated 10.35 Ma, SB 3 at 4400 ft. dated 8.5 Ma and SB 4 at 2210 ft. dated 6.7 Ma. Three (3) maximum flooding surfaces (MFS) were also identified viz: MFS 1 dated 10.4 Ma at 6910 ft., MFS 2 dated 9.5 Ma at 5150 ft. and MFS 3 dated 7.4 Ma at 2930 ft. These surfaces were used to subdivide the stratigraphic column in the well section into five depositional sequences (Sequence I-V) characterized by Lowstand systems tract, Transgressive systems tract and Highstand systems Tract. The depositional sequences identified have quality reservoirs and source rocks with high potential for hydrocarbon generation.