The role of wellbore remediation on the evolution of groundwater quality from CO2 and brine leakage

Abstract

Long-term storage of CO2 in underground reservoirs requires a careful assessment to evaluate risk to groundwater sources. The focus of this study is to assess timeframes required to restore water quality to pre-injection levels based on output from complex reactive transport simulations that exhibit plume retraction within a 200-year simulation period. We examined the relationship between plume volume, cumulative injected CO2 mass, and permeability. The role of mitigation was assessed by projecting falloffs in plume volumes from their maximum peak levels with a Gaussian function to estimate plume recovery times to reach post-injection groundwater compositions. The results show a strong correlation between cumulative injected CO2 mass and maximum plume pH volumes and a positive correlation between CO2 flux, cumulative injected CO2, and plume recovery times, with secondary dependence on permeability. Our analysis suggests that natural recharge has the potential to remediate changes to groundwater chemistry, but it may take several decades.