Numerical Assessment of CO2 Movement in Abandoned Well using Gas-Water Model

Abstract

Abandoned wells pose a significant risk for CO₂ leakage in geological storage, particularly in depleted gas reservoirs where old well infrastructure may lack adequate sealing. This study employs a gas-water numerical simulator to assess CO₂ migration in a worst-case abandoned well scenario, focusing on the impact of wellbore configuration and cement permeability. The methodology involves constructing a 2D Cartesian grid model using CMG IMEX, with input data sourced from literature study to represent fluid properties, cement characteristics, and well configurations. Results indicates that gas saturation migration are influenced by permeability, with high cement permeability (10 mD) leading to rapid CO₂ breakthrough, occurred within 35 years into permeable formations and under 130 years to the surface. In contrast, low-permeability cement (≤0.1 mD) effectively inhibits migration. Sensitivity analysis confirms that incomplete cement coverage above TOC significantly accelerates leakage. The findings emphasize the importance of maintaining low cement permeability and full zonal isolation to ensure long-term well integrity in CO₂ storage applications. This study provides insights for designing safer well abandonment strategies and highlights the utility of numerical models in evaluating long-term CO₂ storage.