Carbon Capture and Storage CCS CO₂ sequestration Depleted oil reservoirs Niger Delta Basin Reservoir simulation Compositional modeling Computer Modelling Group CMG Geological storage CO₂ injection Storage capacity estimation

Worldwide efforts to reduce carbon emissions require technologies that can substantially decrease human-caused CO₂ releases while preserving energy reliability. Carbon Capture and Storage (CCS) presents an interim solution by capturing carbon dioxide from industrial facilities and storing it permanently underground in geological structures. This study examines the viability of storing CO₂ in a typical depleted oil field in Nigeria's Niger Delta Basin using sophisticated compositional modeling through Computer Modelling Group (CMG) software. A detailed three-dimensional reservoir model was constructed using geological, rock property, and production data to simulate extended-term CO₂ injection, plume movement, and entrapment patterns. The research assesses actual storage volumes, injection limitations, pressure changes, and the roles of various trapping methods—including structural containment, residual entrapment, dissolution, and mineralization—across a century-long timeframe. Findings show storage capacity ranging from 5.5 to 11.2 million tonnes of CO₂ with pressure remaining safely under fracture thresholds, confirming reliable containment with negligible escape potential. Parameter studies demonstrate that variations in rock permeability, remaining oil content, and injection speeds significantly affect storage performance and CO₂ distribution patterns. The results validate that Nigeria's depleted petroleum reservoirs offer suitable geological and technical conditions for secure, effective carbon sequestration. This research provides a simulation-driven methodology for nationwide CCS implementation, advancing Nigeria's progression toward reduced-carbon energy systems and adherence to global climate commitments.