carbonate precipitates, fixing the CO2 at depth. Studies on the global availability and capacity of such formations overlain with competent, impermeable formations will be required. Modeling and experiments on CO2 interactions with basalt should point to the level of benefit that could be derived from exploiting these formations for storage.
CO2 could potentially be injected into deep (greater than roughly 3 km) ocean sediments at depths where the pressure/temperature regime will result in a stabilized CO2 with a density greater than that of water. This would essentially isolate the CO2 from seawater to inhibit chemical interactions. Studies of the global availability of such environments and of their porosity, permeability, and capacity would be of specific interest.
CO2 could also potentially be injected into subsea tectonic spreading regions, which are highly active geothermally, creating unique geohydrologic activity. Seawater flows downward into the sediment at distances of many meters to kilometers away from the spreading area, then turns toward the region at depth and is eventually heated to high temperatures and expelled back to the sea. The conditions surrounding these regions have many advantages for fixing CO2 in that the reaction kinetics are fast because of increasing heat and pressure in the direction of flow. It is theorized that CO2 could be injected into the geohydrologic flow field away from the spreading region and entrained in that flow. This would result in the development of several carbonate species (magnesite, magnesium carbonate, dolomite, and calcite) as the combined flow of seawater and CO2 is heated, pressurized, and released back to the sea.
Another possibility is Arctic hydrate storage of CO2 below the permafrost layers in regions where methane and other gas hydrates form. The injected CO2 would form CO2 hydrates that would reside in the pore space of the host rock, with the permafrost layer above it serving, in effect, as the cap rock of a newly created CO2 reservoir.
Opportunities may exist in unconventional storage formations for utilizing the chemistry, temperature, and pressure (depth) to improve the long-term stability of sequestered CO2 through mineralization, precipitation, and other stabilizing reactions.
Possible research concepts include the following:
Characterization of promising, previously unstudied porous rock mass formations from a storage media perspective. This investigation would include examining porosity, permeability, capacity, and chemical composition.
Identification of regional and global locations of favorable formations.
Investigation, through modeling and experimental work, of the nature of rock/CO2 fluid interactions in various rock types over short and long periods. The goal would be to determine beneficial interactions that may occur in basalt or sandstones derived from basalt.
Assessment of containment issues such as interactions that may occur in surrounding and overlying rock types and performance of typical rock mass characterization.
Accumulation and analysis of existing data on CO2 storage. This activity should include examination of natural storage areas as well as engineered storage areas.