Hydrocarbon Potential Assessment of OLUS Field through Integrated Petrophysical and Seismic characterization of Cretaceous-Tertiary Reservoirs, Calabar Flank, Lower Benue Trough, Nigeria

Abstract

As frontier exploration expands, the Calabar Flank remains underexplored due to the lack of detailed quantitative reservoir evaluation in the south-eastern part of Nigeria, despite the promising geological conditions of the region for hydrocarbon accumulations. This study assesses the hydrocarbon potential of the OLUS Field in Calabar Flank by integrating petrophysical analysis, seismic interpretation, volumetric estimation and depositional environment. Petrophysical evaluation reveals high-quality reservoirs with net-to-gross ratios of 0.81-0.95, porosity up to 0.37, favourable hydrocarbon saturations, and low bulk volume water, indicating laterally continuous pay zones. Seismic evaluation identifies fault-bounded closures and rollover anticline structures. The assessment of direct hydrocarbon indication and the amplitude conformity with structures further gives credibility to the presence of hydrocarbon within the exploration areas. Volumetric estimates show substantial un-risked STOIIP with deep-level leads of OLUS South and OLUS East dominating due to large GRVs despite lower reservoir quality. At the same time, mid-level prospects of OLUS North and OLUS East offer lower-risk targets. Depositional analysis indicates a Cretaceous transgressive sequence from fluvial-deltaic to shallow marine carbonates and open marine shales, controlled by sea-level fluctuations and tectonics. The integrated results highlight multiple play types with varying risk and scale, providing a framework for prioritizing exploration targets and guiding field development.