High-Resolution Geomechanics Modelling of Thermal and Hydraulic Effects on Wellbore Integrity and Caprock Stability During CO2 Injection

ABSTRACT: The process of injecting CO2 into geological storage would normally lead to cooling and increase of pore pressure, particularly for the injector well and its immediate vicinity. Mechanical deformation as the result of extra hydraulic and thermal load could lead to damage to wellbore completion and surrounding caprock, potentially creating channels for leakage. The mechanical degradation of the rock and well completion after reacting with CO2 may also lead to further damage. In this paper, high-resolution geomechanics and reservoir dynamic sector models were created to capture mechanical, hydraulic, and thermal response for an area around the injector well. The results showed that, to evaluate the thermal impact on the caprock integrity, a high-resolution near-wellbore model would be necessary to capture the finer details of temperature gradient change around the wellbore. Thermal impact could extend approximately 100 m laterally and up to 20 m into caprock, increasing the risk of creating microcracks in the affected zones. Further away from the reservoir, the impact of temperature change was insignificant. Well completion near the top of reservoir showed greater deformation and risk to compromise integrity. Using casing and cement with higher resistance to CO2 attack would help mitigate the risk. The results showed that while the full-field fluid-flow geomechanics resulted in stable caprock, the high-resolution simulations increased the risk of caprock yielding/failure in the vicinity of the well. Hence, high-resolution near-wellbore modelling is important to assess the near-wellbore effects due to CO2 injection.