Rapid Field-Scale CO2 Storage Simulation Tool with Geomechanically Constrained Fault Leakage

Abstract

Geological carbon dioxide (CO2) storage is vital for climate change mitigation, but CO2 leakage, particularly through faults, poses significant risks. Accurately simulating the impact of fault properties across scales is crucial for predicting field-scale CO2 injection and storage outcomes. However, this task is challenging due to limited knowledge, data scarcity, and computational constraints. This study introduces a fast tool for CO2 leakage risk assessment that addresses these challenges. The tool combines a vertically integrated reservoir model with an upscaled fault leakage function based on source/sink relations. It conceptualizes faults as zones of increased vertical permeability in the caprock and reduced horizontal permeability in the reservoir. A steady-state flow approximation estimates CO2 leakage along faults. Geomechanical effects on fluid flow are modeled by coupling fault porosity and permeability, amongst several other parameters with effective stress using constitutive relations. A decoupled method based on Geertsma's uniaxial expansion coefficient, assuming zero lateral strain and constant total vertical stress is used here. Example simulations are shown to illustrate the impact of geomechanically constrained fault parameters such as capillary entry pressure and permeability on fault leakage. The fast model presented in this study is a valuable tool for identifying uncertainties in key fault parameters and other constitutive relations that affect the behavior of the storage reservoir and potential fault leakage outcomes.