Reservoir Modeling of Geochemical Effects in Caprock and Near-Wellbore Dynamics during CO2 Subsurface Storage in Depleted Gas Reservoirs

The global effort to mitigate carbon emissions has led to significant interest in Carbon Capture and Storage (CCS) technologies. Depleted oil and gas reservoirs are one of the prominent options for CO2 storage, given their proven ability to contain fluids over geological timescales. This thesis focuses on the simulation and modeling of CO2 injection into depleted gas reservoirs, emphasizing geochemical interactions and near-wellbore effects. The study investigates key factors such as CO2-brine-rock interactions and caprock integrity in ensuring long-term CO2 sequestration stability. Using the CMG-GEM compositional simulator, various models are developed to explore multiphase flow, phase transitions, and geochemical reactions under different reservoir conditions. Sensitivity analyses are conducted to evaluate the influence of reservoir depth, gas initially in place (GOIP), and aquifer strength on CO2 storage efficiency and the long-term behavior of the caprock. The findings are compared and discussed to provide insights into the storage capacity of CO2 across different geological formations characterized by varying parameters. Results highlight the importance of precise modeling of geochemical effects and reservoir characteristics to ensure the safe storage of CO2 over extended periods. The findings contribute to the understanding of CO2 injection dynamics and offer insights into optimizing CCS strategies, particularly for depleted gas reservoirs.