Numerical and Analytical Modelling of Wellbore Integrity During CO₂ Injection

This thesis presents a comprehensive literature review on the numerical and analytical modeling of wellbore integrity during CO₂ injection, with the goal of ensuring long-term containment safety in geological carbon storage (GCS) projects. The wellbore–cement–formation system is a critical component in CO₂ sequestration operations, and its mechanical and chemical stability under dynamic subsurface conditions is vital to preventing leakage pathways. The review begins with analytical stress models, including classic elastic solutions and thermally induced stress fields, to evaluate the failure risk under CO₂ injection pressures and temperatures. Numerical simulations—primarily using Finite Element Method (FEM) frameworks—are then discussed to assess stress evolution, damage zones, and fracture propagation, with particular focus on cement sheath degradation due to carbonation, pressure cycling, and thermal mismatch. To bridge the gap between modeling and real-world validation, the thesis analyzes findings from laboratory-scale experiments and long-term field studies, including high-resolution SEM imaging, mechanical testing, and observations from mature CO₂ injection sites such as the SACROC Unit. These provide empirical evidence to support model assumptions and help define boundary conditions for simulation accuracy. Recent developments in data-driven modeling, including machine learning and SHAP (SHapley Additive exPlanations) analysis, are also reviewed as emerging tools for predicting failure risk and identifying key influencing parameters. These are critically compared to conventional physics-based models to highlight their speed, adaptability, and interpretability. Monitoring techniques such as fiber-optic sensing, cement bond logging, and acoustic-based diagnostics are evaluated for their effectiveness in detecting early-stage degradation. The integration of geochemical and geomechanical models with AI-driven workflows is discussed as a promising direction for predictive integrity management. Overall, this literature review synthesizes current research and technologies across multiple disciplines to provide a foundation for designing more resilient CO₂ storage wells and enhancing the reliability of future sequestration efforts.