A novel CO2 storage concept that reduces the leakage risk

Abstract

<p>Geologic carbon storage is needed to reach carbon neutrality and eventually achieve negative emissions. In the classical concept of storing CO<sub>2</sub> in deep sedimentary aquifers, supercritical CO<sub>2</sub> has a lower density than the resident brine. CO<sub>2</sub> is therefore buoyant and the safety and effectiveness of the storage concept rely on the caprock sealing capacity to prevent CO<sub>2</sub> leakage. To reduce the risk of CO<sub>2</sub> leakage and widen the CO<sub>2</sub> storage options, we propose an innovative concept that consists in injecting CO<sub>2</sub> in reservoirs where the temperature and pressure of the resident brine are above the critical point ( 373.95 ºC and 22.064 MPa for pure water). At such conditions, which can be found at depths between 3 to 5 km in volcanic areas, CO<sub>2</sub> is denser than the resident water and thus, sinks. The sinking tendency reduces the risk of CO<sub>2</sub> leakage to the surface even in case of damaged or absent caprock. CO<sub>2</sub> storage in supercritical reservoirs can potentially become an additional option to the existing storage concepts aimed at significantly reduce CO<sub>2</sub> emissions. We estimate that every 100 wells drilled into supercritical reservoirs could store between 50 to 500 Mt/yr of CO<sub>2</sub>.</p><p> </p><p>REFERENCES</p><p>Parisio, F. and Vilarrasa, V. (2020). Sinking CO<sub>2</sub> in supercritical reservoirs. Geophysical Research Letters, e2020GL090456.</p>