Compositional Modeling and Sensitivity Analysis of CO2 Sequestration in Depleted Gas Reservoirs Using ECLIPSE 300

This manuscript explores the technical feasibility of using depleted gas reservoirs for large-scale carbon dioxide (CO2) sequestration, presenting them as a robust and reliable pathway for climate change mitigation. By focusing on the Norne E-segment, the researchers utilized the ECLIPSE 300 simulator to perform a detailed compositional reservoir simulation, which offers a much higher degree of accuracy than traditional "black-oil" models. This sophisticated approach specifically tracks the lifecycle of injected CO2, including its phase behavior, pressure stabilization, and various trapping mechanisms, such as structural, residual, and solubility trapping, that ensure the gas remains safely contained over geological timescales. A central part of the study involves a sensitivity analysis that examines how different geological and operational factors influence storage efficiency. The researchers identified vertical permeability and injection velocity as the most critical determinants of how effectively the CO2 is contained. Interestingly, the findings suggest that geological heterogeneities, such as low permeability shale layers, actually enhance storage security by slowing the upward movement of buoyant gas and encouraging it to dissolve into formation brine. Ultimately, the research provides a refined framework for designing industrial scale sequestration projects, emphasizing that depleted fields are premier candidates for carbon storage due to their proven historical integrity.