Neutralizing Carbonic Acid in Deep Carbonate Strata below the North Atlantic

• Main Author: Daniel P. Schrag
• Language: unknown
• Published: 2008
• Subjects: 54 ENVIRONMENTAL SCIENCES; CALCIUM CARBONATES; CARBON DIOXIDE; CARBONIC ACID; DISSOLUTION; GAS INJECTION; KINETICS; ATLANTIC OCEAN; SEDIMENTS; SITE SELECTION; CARBON SEQUESTRATION; FLOW MODELS; GEOCHEMISTRY; Carbonic acid; North Atlantic
• Online Access: http://www.osti.gov/servlets/purl/876075; https://www.osti.gov/biblio/876075; https://doi.org/10.2172/876075

Our research is aimed at investigating several technical issues associated with carbon dioxide sequestration in calcium carbonate sediments below the sea floor through laboratory experiments and chemical transport modeling. Our goal is to evaluate the basic feasibility of this approach, including an assessment of optimal depths, sediment types, and other issues related to site selection. Through laboratory and modeling efforts, we are studying the flow of liquid carbon dioxide and carbon dioxide-water mixtures through calcium carbonate sediments to better understand the geomechanical and structural stability of the sediments during and after injection. Our modeling efforts in the first year show that the idea is feasible, but requires more sophisticated analysis of fluid flow at high pressure in deep sea sediments. In addition, we are investigating the kinetics of calcium carbonate dissolution in the presence of CO{sub 2}-water fluids, which is a critical feature of the system as it allows for increased permeability during injection. Our experimental results from the first year of work have shown that the kinetics are likely to be fast enough to create dissolution which will affect permeability. However, additional experiments are needed at high pressures, which will be a focus for years 2 and 3. We are also investigating the possibility of carbon dioxide hydrate formation in the pore fluid, which might complicate the injection procedure by reducing sediment permeability but might also provide an upper seal in the sediment-pore fluid system, preventing release of CO{sub 2} into the deep ocean, particularly if depth and temperature at the injection point rule out immediate hydrate formation. Finally, we are in the beginning stages of an economic analysis to estimate costs of drilling and gas injection, site monitoring as well as the availability of potential disposal sites with particular emphasis on those sites that are within the 200-mile economic zone of the United States.