Assessment of Wellbore Cement Integrity Using a Two-Phase Numerical Simulator for CO2 Migration

Abstract

Understanding the behavior of CO2 within wellbore systems is critical to ensuring long-term storage performance, particularly in cemented sections that act as primary barriers. This study employs a two-phase gas–water numerical simulator to examine CO2 migration through the cement sheath under varying permeability conditions. By modeling cement as a porous medium and applying simplified flow assumptions, the simulation tracks CO2 movement, saturation buildup, and overall reservoir gas volume reduction. Results indicate that permeability has a substantial influence on both the extent and timing of CO2 migration, with high-permeability cases showing faster upward transport and earlier surface breakthrough. Simulated pressure data were also used to assess mechanical loads on the casing, revealing that internal pressure buildup may lead to burst conditions in some sections, challenging initial expectations of collapse failure. While the model omits geochemical reactions and assumes static permeability and hydrostatic pressure gradients, it provides a practical framework for pre-injection evaluation of well integrity. These insights may contribute to future screening and design efforts, particularly when considering the feasibility of converting legacy wells for CO2 storage applications