Pressure Interpretation for Leaky Well Characterization during CO2 Storage

Depleted oil and gas reservoirs provide significant storage capacity for geological CO₂ storage. Leakage of the injected CO₂ from the target formation can adversely impact the groundwater resources and ultimately the surface environment. Well integrity is a key for secure underground storage. In this study, we provide a pressure interpretation method for leakage identification during CO₂ storage in a depleted reservoir in presence of multiple leaking wells. We investigate the multiphase flow of the injected and native fluids to interpret the pressure perturbation of the storage layer as well as the above zone. We provide an analytical pressure interpretation method to identify the existing wells that are acting as leakage pathways. The characterization method is capable to estimate the location of the leaking wells. This location identification is based on the traveling time of the pressure signals that are directly dependent on the traveling distance. Therefore, we can identify which wells are leaking among the numerous wells. In addition, the leakage rate and conductivity of the leaking wells are estimated. This step is based on the dependency of the pressure variations on the conductivity of the media. Results show that some leaking wells dominate the leakage pressure signals. This dominance is due to the less distance to the observation point and the greater leakage conductivity than the other leaking wells. We find an analytical approach to evaluate this leakage dominancy. The leakage dominancy approach is useful to estimate the optimum location of the observation points to enhance the value of the observed pressure variation and reduce the number of observation wells.