CCS and Power Systems
Carbon Storage - Geologic Storage Technologies and Simulation and Risk Assessment
Radiocarbon as a Reactive Tracer for Tracking Permanent CO2 Storage in Basaltic Rocks
Performer: Trustees of Columbia University
Project No: FE0004847
Columbia University researchers are performing field studies at the CarbFix CO2 geologic storage site in Iceland (Figure 1). This site is home to a pilot study where CO2 is being injected into a storage formation of basaltic rock. A field study is being used to test and evaluate the efficacy of using carbon-14 (14C) as a reactive tracer (a substance that is used to monitor chemical reactions) to monitor the CO2 transport and characterize CO2 geochemical reactions in the basalt formation. Furthermore, subsurface CO2 transport is being monitored with trifluormethylsulphur pentafluoride (SF5CF3) and sulfurhexafluoride (SF6) tracers. To date, water injection tests verified the injectivity of the formation, and small quantities of CO2 dissolved in water (on the order of several hundred tons) and tracers have been injected. The overall goal is to inject between 1500 and 2000 tons of CO2 dissolved in water.
Researchers are obtaining fluid and rock samples from the CarbFix site where the injected CO2 has been labeled with the 14C tracer. These samples will be analyzed to determine the extent of mineral carbonation (the process by which CO2 reacts with minerals in the reservoir to form solid carbonates) that occurs when CO2 is injected into a basaltic storage reservoir. To monitor the CO2 movement in the target injection reservoir, Columbia University is monitoring SF5CF3 and SF6 tracer concentrations in the storage reservoir by collecting fluid samples in the injection and monitoring wells. Fluid samples are being analyzed and the results are being used to characterize the CO2 dispersion in the basalt. Results are being integrated to assess the use of the tracers for determining reservoir flow and geochemical reactivity, and to assess in situ mineral carbonation in basalt storage formations.
Mineral carbonation is the most permanent storage mechanism as it locks CO2 into the solid structure of a mineral. Basalts are a promising reservoir rock because they have the potential for permanent storage through carbonation. However, mineral carbonation can affect the permeability of reservoir rock, reducing the amount of CO2 that can be injected and stored. It is therefore vital to characterize the relevant geochemical reactions that occur in a reservoir after the injection of CO2 and to improve our understanding of the rate at which these reactions occur. Little is known about geochemical reactions caused by CO2 injection and in situ mineral carbonation rates in basaltic storage reservoirs. The results of this research should increase our understanding of migration and carbonation processes in these potential reservoirs.