There are some proposals for carbon dioxide (CO2) storage in underground structures, such as oil/gas reservoirs, aquifers and sediments. One of the attractive methods of CO2 sequestration is that the exhaust gas containing CO2 is directly isolated in marine geological structure as a solid phase of gas hydrates. We present an experimental study on the formation behavior of CO2 hydrate in sand layer simulated as marine sediments. The formation rate of CO2 hydrate in sand layer was measured by Raman spectrometer and a bulk-scale experiment. The behavior of formation and permeability change in the growth process was observed in the experiment.
Large amounts of gas hydrates, clathrate compounds of water and gases formed under high pressure and low temperature, are found in marine sediments and permafrost. To extract methane gas from its reservoir in a practical method, it is necessary to obtain fundamental information on the mechanism underlying the formation and dissociation of gas hydrates and their properties, including kinetics and crystal growth. We have proposed an advanced method of gas hydrate production, by which methane gas is extracted from the reservoir by replacing methane with CO2 at the molecular level. This method would be feasible to achieve the sequestration of CO2 into the sediments, as well as the promotion of recovery of methane hydrate. The enhanced recovery process of oil, natural gas and coalbed methane by using CO2 is expected to be one of the CO2 underground storage methods. In addition, the process of CO2 injection into aquifers has also been studied as a CO2 storage technique. Recently, based on the perspective of gas hydrate exploitation under the seabed with CO2 displacement reaction or stability and environmental conservation of marine sediments, there has been some basic researches for CO2 hydrate sequestration in marine sediments.