Environmental isotopes in CO2 geological sequestration

Carbon dioxide capture and sequestration (CCS) in deep geological formations has recently emerged as an important option for reducing greenhouse gas (GHG) emissions, and due to the complexity of the issue, CCS has turned into a multiple-discipline research area. Environmental isotopes have been used in various CCS projects worldwide for evaluating trapping mechanisms, selecting storage sites, and monitoring for storage safety. Environmental isotopes are found useful in the investigation of many CCS issues and are particularly effective in identifying phase states (free, dissolved, and mineral state), and in quantifying structural, solubility, and mineral trapping forms of CO2. We used published laboratory results to successfully verify different methods for quantifying structural trapping mechanisms. Our results show that, in short time scales, saturation of the formation with free CO2-phase can be obtained from oxygen isotope measurements on CO2 and/or reservoir brine, and carbon isotope of dissolved inorganic carbon can be used to trace dissolution in brine. Carbon isotopes and other parameters, such as CO2/(3) He ratio, can also be used to confirm the mineral trapping mechanism in natural gas fields. Environmental isotopes can also be used to distinguish mineralogical composition of formations, and to identify hydrodynamic conditions for site selection in addition to monitor potential CO2 leakage. (C)2015 Society of Chemical Industry and John Wiley & Sons, Ltd