Lawrence Berkeley National Laboratory

Because of unknown faults and fractures in the overlying rock, CO2 stored deep underground may move upward, and the intrusion may impact shallow groundwater quality. After leakage of CO2 has ceased, the affected aquifer may show remediation capacity under natural conditions and injections and extractions. In this study, the reactive transport modeling software TOUGHREACT was used to simulate the remediation capacity of a study aquifer. The simulation results show that the intrusion of leaked CO2 would decrease the pH of the target aquifer and trigger the dissolution of calcite minerals. After CO2 leakage has ceased, the pH would increase as would the concentration of Ca because of the dissolution of calcite along the flow path. Scenario simulation results of amelioration of groundwater quality by water injection and extraction show that single injection is the best option and a combination approach of injection and extraction could control the range of the affected area. The pH value should not be regarded as the single indicator for remediation capacity assessment. Parameter sensitive analysis results show that the rates of injection and extraction affect the repair results significantly.