Petrophysical and seismo-stratigraphic analysis of the tertiary formations of the South onshore of the Rio Del Rey Basin (Cameroon margin, Gulf of Guinea) from well logs and seismic data

Abstract

The present study used well log and seismic data to determine the main lithology types, characterize and evaluate the reservoirs properties and discuss about the hydrocarbon quality and productivity in the onshore south of the Rio Del Rey Basin (RDRB). The main results show seven lithologies inside the Isongo, Diongo and Nguti including clays, sandstones and clayey sandstones, the most dominant, and limestones, dolomites, sandstone limestones and clayey limestones, the less dominant. Seventeen reservoir zones with fifteen gas-bearing and two oil-bearing were identified in the Miocene sands of the Isongo, Diongo and Nguti Formations and very few in the Upper Oligocene sands of Akata Formation. The average values of petrophysical parameters obtained are V_shale (13.26–31.3%), NTG (64.48–87.07%), ∅_eff (18.54–26.60%), ∅_avg (23.27–33.59%), S_w (4.84–11.10%), S_hc (88.90–95.16%), and K (1258.96–2187.26 mD). It shows that the identified reservoirs are of the good quality and can be commercially viable for the gas. Knowing that the RDRB and the neighbouring ones (Niger Delta, Rio Muni and Gabon basins which are OPEC members) have good petrophysical parameters, findings from this investigation show that the key difference between RDRB and others lay on the low continuity and vertical extension of these reservoirs, as well as the lower sedimentary thickness (6–7 km), the tectono-stratigraphic architecture and the production essentially focused on the Miocene horizons.