Fundamental study of the effect of using carbon dioxide in methane hydrate development Kentaro Fukuda Yujing Jiang Yoshihiko Tanahashi Nagasaki University Geoenvironmental Lab

Methane Hydrate (MH) Petroleum and Natural gas are main energy resources. The development of new energy resources Now Future Limit of the quantity of resources Methane Hydrate (MH) Background of Research

MH A material that Methanes molecule is surrounded in the crystallization of the caged Waters molecule forms Equilibrium conditions: Low temperature and High pressure Sediment of sea beds Eternal frozen ground area Distribution area Triangle Methanes molecule Ball Waters molecule Crystal structure of MH Background of Research

The confirmation of existence of MH in sea area around Japan The amount of the resource : About 7.4 trillions cubic meters Equivalent to about 100 years of the amount of annual natural gas consumption in Japan(1999) Possibility of supplying energy for long term in Japan Distribution area 1. The Nankai Trough 2. Kuril Islands 3. Sea of Okhotsk 4. Tataru Trough 5. Okushiri submarine ridge 6. West Tsugaru basin Gathered MH(White ice) The gathered MH in Niigata offing

However Background of Research MH has the possibility to become the next generation energy The influence on sea beds in the production of MH (Buckling of winze, Landslide etc.) The necessity of developing MH considering the environment problems Problem

More stable than MH Disposal of greenhouse gases Low cost Background of Research The suggestion of developing MH with Carbon Dioxide The formation of Carbon Dioxide Hydrate (CO 2 -Hyd) Advantage Global environment problem Energy problem Solution at the same time

Background of Research Ocean Lower layer MH layer Upper layer CO 2 -Hyd layer Production of MH CO 2 -Hyd layer CO 2 injection Construction of artificial roof Stabilization of soft stratum CO 2 -Hyd layer CO 2 injection Construction of artificial prop Maintenance of artificial roof Immobilization of CO 2

Purpose of Research Evaluate the property by doing triaxial compression test on the specimen with CO 2 gas and mixture gas (emphasizing the latter one) Comparison of the strength on the simulated specimen with each of CO 2 -Hyd and MH Evaluation of utilization possibility of CO 2 Organization of Collaboration Methane Hydrate lab, National Institute of Advanced industrial Science and Technology

Close-packed Sample Manufacture Mold of pillar shape (Caliber:50mm, Height:100mm) Water + Toyoura sand Freeze with refrigerator Drain Adjustment of the saturation

Set of Frozen sample Sample Set Triaxial Compression Test Apparatus Set of Frozen sample Installation of Rubber sleeve Installation of lid of pressure container Injection of antifreeze solution Pressure Container

Formation of CO 2 -Hyd Establishment of formation conditions Pore pressure (Formation pressure) : 8MPa Lateral pressure : 9, 10, 12MPa Temperature in the cell : 6, 2.5 Penetration of mixture gas in the void of the specimen Formation of CO 2 -Hyd Adjustment of formation time Control with outside computers

Triaxial Compression Test In situ conditions Test conditions Water depth 700m The layer with the thickness of 100m under see beds Undrain conditions Back pressure : 0MPa Pore pressure : 8MPa Lateral pressure : 9, 10, 12MPa Temperature in cell : 6, 2.5 Establishment of the conditions close to in-situ Enforcement of loading test

Decomposition of CO 2 -Hyd The sample after decomposition Decomposition of CO 2 -Hyd by decompression Measurement of the amount of CO 2 gases with the gas meter Calculation of CO 2 -Hyd saturation degree

Constitution of Sample Core manufacture CO 2 -Hyd formation V VgVg VwVw Vs VvVv V VgVg VhVh VwVw Vs VvVv Sand Water Gas Hydrate Pore volume Gas Hydrate CO 2 -Hyd saturation degree

Stress-Strain relation (mixture gas) The strength at the same level as N2 The influence of formation of Hydrate: small Increase of the saturation degree of Sh than that in 6 Increase of the strength 9MPa

σ σ max σ max /2 ε 50 ε Deformation modulus E 50 Secant elastic modulus in axis difference stress 50 percent σ max Maximum axis difference stress ε 50 Strain in axis difference stress 50 percent

Deformation modulus May depend on the saturation degree of Sh Lateral pressure 9MPa Linear increase of deformation modulus

Formation conditions Concentration degree CO 2 gas, Methane 100 Mixture gas The ratio of 50 of CO 2 and N 2

Loading conditions

Maximum axis difference stress Linear strength increase Mixture gas: The strength is high. The strength at the same level with MH is shown although their conditions are different.

Maximum axis difference stress The strength at the same level with MH despite at low saturation degrees The possibility that N2 was mixed in the hydrate

Conclusion Evaluation of the mechanical property of CO 2 -Hyd CO 2 gas Mixture gas Low High Formation pressure Strength Low High MH Mixture gas Drain Undrain Strength at the same level The utilization possibility of CO 2 is confirmed Drain conditions Strength

Future problem Applying the triaxial compression test under the conditions more close to in-situ Realization of MH development by using CO 2 Elucidation of the change of hydrate saturation degree by the influence of Nitrogen when using the mixture gas

END