Neutralizing Carbonic Acid in Deep Carbonate Strata below the North Atlantic

• Main Authors: Lackner, Klaus, Harvey, Charles, Watson, Bruce
• Other Authors: United States. Department of Energy.
• Format: Report
• Language: English
• Published: Harvard College 2008
• Subjects: 02 Petroleum; Trapping; Capacity; Sediments; Seas; 15 Geothermal Energy; Porosity; Salinity; Floors; Chemical Reactions; Carbonic Acid; Carbon Dioxide Injection; Carbonates; Water; Permeability; Geothermal Gradients; Storage; Carbonic acid; North Atlantic
• Online Access: https://doi.org/10.2172/932953; https://digital.library.unt.edu/ark:/67531/metadc902559/

Carbon dioxide injection into deep sea sediments below 2700 m water depth and a few hundred meters to fifteen hundred meters deep in the sediment column may provide permanent geologic storage by gravitational trapping. At high pressures and low temperatures common in deep sea sediments a few hundred meters below sea floor, CO{sub 2} will be in its liquid phase and will be denser than the overlying pore fluid. The lower density of the pore fluid provides a cap to the denser CO{sub 2} and ensures gravitational trapping in the short term. The overall storage capacity for CO{sub 2} in such deep sea formations below the ocean floor is primarily determined by the permeability, and will vary with seafloor depth, geothermal gradient, porosity, and pore water salinity. Furthermore, the dissemination of the injected CO{sub 2} in the sediments and potential chemical reactions between CO{sub 2}, pore fluid and sediments will define its fate in the storage reservoir. The main objectives of our research was to evaluate the potential for sub-seabed CO{sub 2} storage in deep sea sediments using a range of approaches including experiments, permeability analysis, and modeling. Over the course of the three-year award, our results support an important role for sub-seabed storage in a diverse portfolio of carbons sequestration options. Our analysis has shown the feasibility of this type of storage, and also emphasizes that escape or leakage from such sites would be negligible. The most difficult challenge is to overcome the low permeability of typical deep-sea sediments, and a variety of approaches are suggested for future research.