Simulation of the two-direction permeability of oilwell cement in CO2-saturated water

In the process of geological carbon sequestration, the CO2 injected into the formation will react with the hollow cement ring or wellbore cement plug, and reduce the sealing performance of the cement body to further destroy the integrity of the wellbore, causing CO2 leakage and seriously affecting the efficiency of CO2 storage. This study aimed to investigate the effect of CO2 on the sealing performance of cement stone in the wellbore under the condition of CO2 geological storage. For this purpose, a reaction transport model of CO2-corroded cement stone was created and calibrated based on laboratory tests. The results show that the corrosion area of cement stone is a layered structure, resulting in anisotropy of sealing performance of cement stone. The permeability of cement stone perpendicular to the corrosion direction increases with the increase of corrosion depth, while the permeability along the parallel corrosion direction first decreases and then increases. After 2000 hours of corrosion, the permeability increase of cement stone perpendicular to the corrosion direction is greater than that parallel to the corrosion direction by 12 %.