Migration and Leakage of CO2 From Deep Geological Storage Sites

Assessing the probability and risk of migration of CO2 from a storage reservoir and its leakage at the surface forms a critical part of the evaluation of any geological storage site. Insights from small‐ and large‐scale demonstration projects, experimentation, numerical simulation, and natural analogues provide insights into the mechanism and processes controlling the flows of CO2; however, there are gaps and uncertainties in our understanding. Uncertainty surrounds the probability and significance of leakage by caprock failure, and significant gaps exist in our understanding and ability to model the processes of flow and dissolution that will retard leakage as CO2 migrates through faults and fracture networks.

This study provides an overview of the physiochemical processes involved in fluid leakage from deep storage sites with a major focus on carbon storage. Our aim is to highlight the physical flow, geochemical, geomechanical, and hydrodynamic processes that govern the rates of CO2 flow and to address the microscale, macroscale, and basin‐scale geological features that influence these flows. We review published CO2 fluxes from natural analogues relevant to deep storage sites and provide a summary of the learnings from a well‐studied analogue for carbon storage in the area of Green River, Utah.