Simulation Study of Sealing Integrity in Abandoned Wells Within CO2 Sequestration Block

Abstract

As the main leakage pathway in CO2 sequestration, the sealing integrity of the abandoned wellbore is directly related to the sequestration effect. To this end, for the abandoned wellbore leakage problem, a three-dimensional finite element model of cement plug-formation is developed based on the cohesive zone method coupled pore pressure. In this paper, we simulated the CO2 transport process along the abandoned wellbore and analyzed the influence of cement slurry system and bonding quality on the risk of leakage. The simulation results show that: CO2 accumulation induces micro-annulus at the plug-formation interface, forming a leakage channel, and the micro-annulus tends to develop axially; the risk of wellbore leakage is lower when choosing higher modulus, higher Poisson's ratio, and micro-expansion cement to seal the wellbore; the micro-annulus is extremely sensitive to the poor bonding zone, and the control of bonding quality should be focused when sealing the wellbore. The results of this study have important implications for guiding wellbore abandonment within the CO2 sequestration block.