Rapid fault leakage modeling for CO₂ storage in saline aquifers

Simulating the fluid flow along fault zones at different scales is essential for predicting the CO₂ leakage and containment during injection and storage. However, this can be challenging, especially in the early stages of a storage project when knowledge of the reservoir and caprock is limited and the cost of obtaining the relevant data is high. This study proposes a tool for fast screening of fault leakage at the site screening stage. The tool uses a vertically integrated reservoir model coupled with an upscaled fault leakage function based on source/sink relations. The fault is conceptualized as an increased vertical permeability through the caprock due to the presence of a fracture network in the damage zone and a reduced horizontal permeability in the reservoir due to fault throw and presence of a low-permeability fault core. Simulation results of various CO₂ injection scenarios in a reservoir with potential for fault leakage demonstrate that the tool can produce physically consistent leakage predictions. The computationally efficient model presented in this study is a valuable tool for quantifying uncertainties in key fault parameters, and other constitutive relations that affect the behavior of the storage reservoir and potential fault leakage. By incorporating this tool into the site screening stage, stakeholders can quickly screen the risk of CO₂ leakage along faults across a range of possible storage sites and subsequently design targeted data acquisition campaigns to better characterize and model the faults. Overall, the proposed tool is a cost-effective and efficient method for screening fault leakage risk during CO₂ injection and storage, helping to ensure safe and effective carbon storage.