Sequence stratigraphic and reservoir modeling of KOC Field onshore Niger Delta Basin: implication for mature oilfield revitalization

Recently, the exploration focus in the onshore areas of the Niger Delta Basin has been targeted towards extending the economic viability of “shallow hanging” producing reservoir units whilst searching wider and deeper for new oil and gas pools beyond known depths. The need therefore arises to deploy improved technologies for accurate mapping of prospect opportunities located at intermediate and deeper intervals within the basin. In this study, integrated sequence stratigraphic and reservoir modeling of the KOC Field onshore Niger Delta Basin was carried out using well logs, 3D seismic, and biostratigraphic data to assess the hydrocarbon potentials and also uncover the reservoir geometry, stratigraphic configuration, and structural framework of the study area. Logging and biofacies information from seven (7) wells, as well as key stratal surfaces including three (3) sequence boundaries (SB) and three (3) maximum flooding surfaces (MFS) provided in Well 001 and Well 039, formed the basis for chronostratigraphic correlation across the field. Two genetic sequences bounded at the top and base by maximum flooding surfaces were mapped and designated as Genetic Sequence 1 (G_SEQ1) and Genetic Sequence 2 (G_SEQ2). Three main stacking patterns (progradational, retrogradational and aggradational) interpreted as Lowstand Systems Tract (LST), Highstand Systems Tract (HST) and Transgressive Systems Tract (TST) were delineated from each of the identified genetic sequences. Lithological correlation of the wells revealed two hydrocarbon-bearing sand units with good reservoir quality characteristics. These reservoirs designated as R12 Sand and R15 Sand belonged to the LST and TST of G_SEQ2, and were interpreted to be basin floor fans and channel fill complexes, deposited within the neritic to bathyal environments. 3D geological modelling of the reservoirs showed good structural closures with thick sedimentary packages, suggesting that they are good locations for hydrocarbon accumulation. The major faults constitute good reservoir seals due to stratigraphic juxtapositions that may have prevailed in the cause of the dip slip movement.