Sequence Stratigraphic Evaluation of Sediments Domicile in Day Field Located in the Onshore Central Swamp Depobelt of the Niger Delta, Nigeria

Abstract

This study employs the tool of sequence stratigraphy to evaluate Day Field, in the Onshore Niger Delta of Nigeria for hydrocarbon predictions using six (6) well logs displayed at standard scales to enhance log trends for lithologic and stratal package delineation. The identified key stratigraphic bounding surfaces were tied to well-defined palynological (P) zone and foraminiferal (F) zones with the aid of the biostratigraphic data and calibrated using the Niger Delta Chronostratigraphic chart. Five (5) MFSs (34.0, 33.0, 31.3, 28.1, and 26.2 Ma) and six (6) SBs (35.4, 33.3, 32.4, 29.3, 27.3, and 24.9 Ma) were delineated. The stratigraphic surfaces were matched with the palynological (P480– P580) and foraminiferal zones (P20/N1–P22/N3) encountered. The results indicate that the study area is of Late Eocene to Late Oligocene age (26.2–35.9 Ma). The key stratigraphic surfaces also reflect a series of relative sea-level falls (regressive episodes) and sea-level rises (transgressive episodes) that are regionally extensive and correlated across the wells. Five sequences (SEQ1–SEQ5) were recognized, SEQ1 and SEQ5 comprising three system tracts (LST, TST, and HST) revealing four third-order depositional sequences (classified as type 1 sequence), while SEQ2-SEQ4 comprises two system tracts (TST and HST). Two depositional environments were interpreted from the log trends; the Fluvial (shoreface) and Tidal environments. The hydrocarbon exploration prospects identified are the sand units of the LST and HST combining with the shale units of the TST offering good reservoir and seal/source rocks respectively.