Offshore Carbon Dioxide Storage within Oceanic Crust: Geological and Economic Implication
Abstract
The rise of carbon dioxide (CO2) in the atmosphere, due to decades of fossil fuels burning, is a key driver of anthropogenic climate change. Carbon Capture and Storage (CCS) is a potential mitigation strategy for long-term sequestration of CO2 that will allow the continued use of hydrocarbons during the transition to low carbon energy. This study focuses on the CO2 storage potential of the uppermost oceanic crust - the largest igneous province on Earth - motivated by the strong evidence that basaltic seafloor has acted, in the past, as a major sink for CO2. Two CO2 trapping mechanisms are investigated for the whole oceanic crust: gravitational, meaning that CO2 is denser than seawater, and physical, where the presence of ≥200 m of overlying low permeability sediments isolate the CO2 injected into the basalts from the oceans. Global databases are used to estimate temperature, pressure, and hence density of CO2 and seawater at the sediment-basement interface. Water depth, sediment thickness, and oceanic crustal age all influence the relative gravitational stability of CO2 versus seawater. Approximately 8% of the entire oceanic crust is identified as naturally suitable for combined gravitational and physical trapping of CO2-only injected into the basement. Five potential targets are proposed, of which even the smallest provides sufficient CO2 sequestration capacity ( 13,800 Gt CO2) for multiple centuries of emissions. The proportion of suitable offshore areas increases when the buoyancy of CO2 is overcome by the co-injection of CO2 and seawater, as suggested by the CarbFix project in Iceland. Such an approach, although requiring large volumes of seawater, has the advantage of including portions of oceanic crust characterised by shallower water depth and located nearby the coast, where most of the anthropogenic CO2 sources are. To contextualise the potential of the CCS offshore options within the energy market, a first order estimate is made of the costs related to the transport and storage of 20 Mt/yr of CO2 in deep-sea basalts for 25 years, as a function of distance from the shore, injection rate, and water depth. The results show that offshore CO2 injection into seafloor basalts for CCS is feasible, with costs of transport and injection of CO2 between 21 to 38 $/t CO2, for water depths up to 5000 m and offshore distances up to 1500 km.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMGC23G1281M
- Keywords:
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- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGEDE: 1635 Oceans;
- GLOBAL CHANGEDE: 4805 Biogeochemical cycles;
- processes;
- and modeling;
- OCEANOGRAPHY: BIOLOGICAL AND CHEMICALDE: 4806 Carbon cycling;
- OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL