Investigation into gas production from natural gas hydrate: A review

We present experimental structure-I clathrate hydrate (methane, carbon dioxide, and methane−carbon dioxide) equilibrium and ice-melting data for mesoporous silica glass. In both cases, high capillary pressures result in depressed solid decomposition temperatures (clathrate dissociation and ice melting), as a function of pore diameter. Clathrate dissociation data show a significant improvement over existing literature data, which is attributed to the improved experimental techniques and interpretative methods used. Through application of a melting (or clathrate dissociation) modified Gibbs−Thomson relationship to experimental data, we determine similar values of 32 ± 2, 32 ± 3, and 30 ± 3 mJ/m2 for ice−water, methane clathrate−water, and carbon dioxide clathrate−water interfacial tensions, respectively. The data are important for the accurate thermodynamic modeling of clathrate systems, particularly with respect to subsea sedimentary environments, and should prove useful in the simulation of potential meth...

Experimental measurement of methane and carbon dioxide clathrate hydrate equilibria in mesoporous silica

Equilibrium conditions of CH4, CO2, and C3H8 hydrates confined in small pores of porous glass were determined. The dissociation temperature of each hydrate at a given pressure shifted lower than that for bulk hydrate; the largest shift for CH4 hydrate was −12.3 K ± 0.2 K for 4-nm-diameter pores and the shift decreased to only −0.5 K for 100-nm pores. CH4 hydrate experiments at temperatures lower than the quadruple point of 270.6 K in 30-nm porous glass showed no shift of the equilibrium line. All temperature shifts were fitted by the Gibbs-Thomson equation; the best fits for CH4, CO2, and C3H8 hydrates predicted hydrate−water interfacial energies of 1.7(3) × 10-2 J/m2, 1.4(3) × 10-2 J/m2, and 2.5(1) × 10-2 J/m2, respectively. Both type-I hydrates of CH4 and CO2 had interfacial energies within 20% of each other but significantly smaller than the type-II hydrate of C3H8. Ice formation in the same porous glass fit the Gibbs−Thomson relation with an interfacial energy of 2.9(6) × 10-2 J/m2, which is in good a...

Effects of Pore Sizes on Dissociation Temperatures and Pressures of Methane, Carbon Dioxide, and Propane Hydrates in Porous Media

In situ methane hydrate dissociation with carbon dioxide sequestration: Current knowledge and issues

The Potential of U.S. Cropland to Sequester Carbon and Mitigate the Greenhouse Effect . R. Lal, J.M. Kimble, R.F. Follett, and C.V. Cole. 1999. CRC Press LLC, Boca Raton, FL. xv + 128 p. $58.90, ISBN 1-57504-112-X, hardcover.

Equilibrium pressures for the dissociation of methane hydrates confined in silica gel pores of nominal radii 7.5, 5.0 and 3.0 nm were measured over a wide temperature range, and were observed to be higher than those for bulk methane hydrate. A model is presented that allows the pore radius involved in each equilibrium to be determined from these data, so that the model exactly reproduces the experimental equilibrium pressure. Based on this model, pore volume distributions were reconstructed and found to be in good agreement with those obtained from nitrogen desorption isotherms, indicating that hydrate formed nearly uniformly in the available pores.

Methane hydrate equilibria in silica gels with broad pore-size distributions

Equilibrium pressures for the dissociation of propane hydrate confined in silica gel pores of nominal radii 7.5, 5.0, 3.0, and, 2.0 nm were measured across a wide temperature range, and were higher...

Measurements of Equilibrium Pressures and Temperatures for Propane Hydrate in Silica Gels with Different Pore-Size Distributions

Equilibrium pressures for the dissociation of carbon dioxide hydrates confined in silica gel pores of nominal radii 7.5, 5.0, and 3.0 nm were measured over a wide temperature range and were observed to be higher than those for bulk carbon dioxide hydrate. Models that have been previously reported in the literature are used to determine the pore radius involved in each equilibrium associated with these data, exactly reproducing the experimental equilibrium pressure. Based on these models, pore volume distributions are reconstructed and compared to those obtained from nitrogen desorption isotherms. This comparison indicates that in the nominal 7.5 nm pores the hydrate formed nearly uniformly in the available pores, while in the nominal 5.0 and 3.0 nm pores it did not.

Thermodynamics of carbon dioxide hydrate formation in media with broad pore-size distributions.

Concerns about the potential effects of rising carbon dioxide levels in the atmosphere have stimulated interest in a number of carbon dioxide sequestration studies. One suggestion is the sequestration of carbon dioxide as clathrate hydrates by injection of carbon dioxide into methane hydrate. Energy-supply research estimates indicate that natural gas hydrates in arctic and sub-seafloor formations contain more energy than all other fossil fuel deposits combined. The simultaneous sequestration of carbon dioxide and the production of methane by injection of carbon dioxide into deposits of natural gas hydrates, if possible, represents a potentially efficient and cost effective option for the sequestration of carbon dioxide. Data in the literature show that the conversion of bulk methane hydrate into carbon dioxide hydrate is thermodynamically favored. These results are not directly applicable to naturally occurring hydrates, because the hydrates in these locations are embedded in sediments. The thermodynamics of any potential conversion of CH4 hydrate to CO2 hydrate will therefore be affected by the size of the pores in which the conversion of CH4 hydrate to CO2 hydrate would take place. We have developed a model that is able to explain and predict equilibria in porous media for any pore size distribution. Thismore » model can be used to calculate the heats of dissociation for these hydrates in porous media as a function of pore size and temperature. These results allow for an assessment of the thermodynamic feasibility of converting CH4 hydrate to CO2 hydrate in porous media involving various size pores. We have used this model to derive a simple, explicit relation for the hydrate formation conditions in porous media, as well as the enthalpy of dissociation for these hydrates.« less

Assessing the Thermodynamic Feasibility of the Conversion of Methane Hydrate into Carbon Dioxide Hydrate in Porous Media

Equilibrium pressure for the dissociation of methane, propane, or carbon dioxide hydrates confined in porous glass pores of nominal 15 nm radii were measured over a wide temperature range. A previously presented model is used to determine the pore radius involved at each temperature. Based on these results, pore volume distributions were reconstructed and compared with distributions obtained from nitrogen desorption isotherms. The analysis of the reported data indicate that for all three hydrates, nearly all of the sorbed water vas converted to hydrate, but the amount of water taken up by the porous glass was less than that expected from nitrogen desorption studies. When propane was used to form hydrate, the pores not occupied by hydrate were involved in propane vapor-liquid equilibria.

Kal Seshadri

Papers

Methane hydrate equilibria in silica gels with broad pore-size distributions

Measurements of Equilibrium Pressures and Temperatures for Propane Hydrate in Silica Gels with Different Pore-Size Distributions

Thermodynamics of carbon dioxide hydrate formation in media with broad pore-size distributions.

Assessing the Thermodynamic Feasibility of the Conversion of Methane Hydrate into Carbon Dioxide Hydrate in Porous Media

Thermodynamics of Methane, Propane, and Carbon Dioxide Hydrates in Porous Glass