CO₂ Sequestration Beneath The Seafloor

Evaluating The In Situ Properties of Natural Hydrate-Bearing Sediments and Oceanic Basalt Crust

Abstract

The injection of CO₂ below the seafloor offers several advantages for seques tration, particularly that it may retard the return of CO₂ to the atmosphere for long periods of time and minimize any environmental impact on the benthic ecosystem. A number of marine geological environments contain natural aqui fers with impermeable seals that are potentially suited for CO₂ injection. Owing to 30 years of scientific drilling in the deep ocean, much is already known about such environments. Two possible locations which have been previously drilled and studied are compared in this paper-one in natural hydrate-bearing sediments and one in oceanic basalt crust. Although additional measurements and reservoir models are needed for a comprehensive and more conclusive evaluation, the existing information suggests that an oceanic crustal site is more likely to accommodate a substantial volume of injected CO₂. Long-term monitoring of such sites would also help to establish a quantitative understanding of the fate of CO₂ sequestered below the seafloor.