A Brief Overview of Isotope Measurements Carried Out at Various CCS Pilot Sites Worldwide

Abstract

About 1800 geochemical measurements including more than 1000 isotope analyses have been published as a result of geochemical monitoring programs established at several CO2 storage and enhanced oil and gas recovery projects worldwide. These projects are briefly discussed here in order to compare sampling techniques to obtain fluid and gas samples for chemical and isotopic analyses. In all the projects, changes of stable isotope ratios of CO2 and dissolved inorganic carbon in samples obtained pre- and post-injection were used to quantify solubility and ionic trapping of CO2 via stable isotope mass balances. Further applications include, monitoring of underground CO2 migration and early detection of potential CO2 leaks into overlying formations. Other benefits of these stable isotope tracers include a better understanding of water-rock-gas interactions with CO2 under supercritical conditions and often highly saline reservoir fluids that are present in the storage formations. While the results of these projects need further laboratory and experimental confirmation, further increase in field applications of stable isotope tracer techniques are anticipated with the introduction of new portable laser stable isotope mass spectrometers.