Assessing Brine Leakage in Saline Sedimentary Basins for Geological Carbon Storage: Pressure Dynamics and the Influence of Faults and Abandoned Wells

Abstract We develop a mathematical model to quantify the pressure response due to brine and CO2 leakage in saline sedimentary basins used for geological carbon storage. The scope includes evaluating the impact of abandoned wells and faults, with a focus on pressure dynamics and hydrological mechanisms that influence leakage pathways. A semi-analytical approach is employed to model fluid migration and leakage in saline sedimentary basins through conductive abandoned wells to the overburden formation. The methodology incorporates the principle of superposition in space to account for the presence of faults and abandoned wells as leaky pathways. Pressure diffusivity equations are used to evaluate leakage rates under varying reservoir and boundary conditions. The model is validated using high-fidelity numerical simulations that models the leakage through abandoned wells in the presence of sealing faults, ensuring robustness and accuracy. The proposed model quantifies the pressure response due to leakage rates with high accuracy, highlighting the significant influence of well integrity and fault characteristics on fluid migration. Observations indicate that poorly sealed abandoned wells contribute significantly to leakage into overlying aquifers. Pressure dynamics reveal critical thresholds at which fluid migration occurs, providing insights for optimal injection site selection and risk mitigation. The results demonstrate the effectiveness of the semi-analytical model in capturing the geological storage mechanisms. The study concludes that addressing abandoned well integrity and fault permeability is essential to ensure the safety and efficacy of geological carbon storage. This study contributes by enhancing the infinite-acting model of injection and abandoned wells through the integration of no-flow boundaries using the method of images. The research presents a novel approach that incorporates sealing faults and abandoned wells as critical leakage pathways into existing semi-analytical models. By providing practical and efficient tools and actionable insights, it enables engineers to better predict and mitigate brine and CO2 leakage in saline sedimentary basins, thereby enhancing the safety and efficiency of geological carbon storage practices.