MULTIPHASE FLOW AND REACTIVE TRANSPORT OF IRON AND TRACE METALS DURING UPWELLING OF SALTY, CO2-RICH WATER IN THE VIRGIN RIVER BASIN; A NATURAL ANALOGUE FOR LEAKAGE FROM DEEP GEOLOGIC SEQUESTRATION SITES

Geologic carbon sequestration can help reduce greenhouse gas emissions, but it poses a risk for groundwater resource contamination from leakage of CO₂ and brine out of deep storage formations into shallow aquifers. Our ability to predict and mitigate these risks depends upon improved understanding of complex interrelated multiphase flow and reactive transport processes. Unlike laboratory or field experiments, natural analogues allow for observation of these processes over long periods of time. For this study, upward migration of CO₂ and brine was investigated at a natural analogue site in the Virgin River Basin of Southwestern Utah. Multiphase flow of CO₂ and brine, as well as associated metal mobilization and immobilization reactions, were modeled using the TOUGHREACT software from Lawrence Berkeley National Laboratory. Model results were used to improve estimates of the rate and distribution of the upwelling source below the aquifers, and to explain the transport of iron throughout the system. The model also assessed the extent and severity of groundwater contamination that would occur if a source of arsenopyrite existed near the upwelling area. These results offer insight into long-term effects that leakage of CO₂ and brine may have on shallow sandstone aquifers, as well as surface water systems via discharge from springs.