Assessing the Feasibility of Above Injection Zone Pressure Monitoring of CO₂ Geologic Storage in the Williston Basin, North Dakota, USA

This study evaluates the feasibility of above injection zone pressure monitoring (AIZ pressure monitoring) in one of the Williston Basin CO₂ storage projects. This approach relies on reservoir flow-geomechanics coupled simulations to predict the pressure response in the AIZ in the case of perfect seal and hypothetical scenarios where CO₂ leakage occurs along the injector or nearby legacy wells. In this study the advantages and limitations of the pressure monitoring at AIZ were evaluated and we found that while this approach is capable of accurate and early detection of CO₂ leakage, it is recommended to be implemented with other direct monitoring methods as it has its limitations as was seen in two simulation cases with low permeability leakage pathways that allowed CO₂ to slowly migrate to the monitoring formation without causing significant pressure changes in this later which would make such leaks undetectable if pressure monitoring is the only monitoring technique implemented in the storage complex.