Modeling Studies on the Transport of Benzene and H2S in CO2-Water Systems

摘要

CO2 sequestration into deep reservoirs must ensure the safety of overlying groundwater aquifers. Questions exist whether groundwater could become contaminated by leakage and upward migration of CO2, possibly comprising co-injected H2S and/or organic compounds mobilized by supercritical CO2 (SCC) at depth. In the first part of an EPA-funded project on potential effects of carbon capture and geologic storage (CCS) on groundwater resources, we evaluated the potential for mobilization of trace elements in response to CO2 intrusion via systematic reactive-transport simulations involving hypothetical release scenarios. Other researchers have investigated this issue by laboratory experiments as well as modeling work integrated with controlled field experiments of CO2 release in freshwater aquifers. Less work has been conducted with respect to the potential impact on groundwater from organic constituents and co-injectants such as H2S. This report presents research related to these issues, and completes the second chapter of the aforementioned EPA-funded project. The objective of this study was primarily the development of modeling capabilities to assess the mobilization and transport of organics with supercritical CO2, and the co-injection and transport of H2S with SCC. Focus was given to mobilization/transport aspects more than to actual effects on shallow groundwater quality, since these effects would vary depending on aquifer characteristics such as water composition, mineralogy, sorption behavior, and pH buffering capacity.