Numerical Simulation of Steam Assisted Gravity Drainage Recovery Utilizing CO2 Alternating N2 in a Niger Delta Reservoir

Abstract The recovery of hydrocarbons from highly heterogeneous reservoirs remains a formidable challenge in the oil and gas industry, particularly in mature and complex formations such as those found in the Niger Delta. This study investigates an advanced enhanced oil recovery (EOR) technique, Steam-Assisted Gravity Drainage using CO2 alternating with N2 (SAGD-CAN), as a novel strategy for improving oil displacement efficiency in such reservoirs. Leveraging the capabilities of Schlumberger's Petrel for static modeling and CMG STARS for dynamic thermal simulation, a robust numerical model was developed to capture the reservoir's heterogeneity and reproduce historical production behavior with high fidelity. The SAGD-CAN process involves alternating injection of CO2 and N2 with steam to synergistically reduce oil viscosity, enhance gravity-driven drainage, and improve sweep efficiency through compositional and thermal effects. Simulation results indicate that the SAGD-CAN approach significantly outperforms conventional SAGD, achieving an eightfold increase in cumulative oil recovery relative to primary recovery. Over a 20-year operational window, the hybrid process yields an incremental recovery of over 628,000 barrels compared to traditional SAGD scenarios. These findings suggest that SAGD-CAN can serve as a transformative EOR technique for maximizing recovery in complex Niger Delta reservoirs while potentially enabling CO2 sequestration benefits. The study underscores the importance of integrated simulation frameworks in optimizing recovery processes and supports broader field-scale adoption of hybrid EOR strategies in the global energy transition era.