Numerical analysis of gas production from large-scale methane hydrate sediments with fractures

This paper shows the results of a field appliance study of the hydraulic well method to prevent embankment piping, which is proposed by the Japanese Matsuyama River National Highway Office. The large-scale embankment experiment and seepage analysis were conducted to examine the hydraulic well. The experimental procedure is focused on the pore water pressure. The water levels of the hydraulic well were compared with pore water pressure data, which were used to look over the seepage variations. Two different types of large-scale experiments were conducted according to the installation points of hydraulic wells. The seepage velocity results by the experiment were almost similar to those of the analyses. Further, the pore water pressure oriented from the water level variations in the hydraulic well showed similar patterns between the experiment and numerical analysis; however, deeper from the surface, the larger pore water pressure of the numerical analysis was calculated compared to the experimental values. In addition, the piping effect according to the water level and location of the hydraulic well was quantitatively examined for an embankment having a piping guide part. As a result of applying the hydraulic well to the point where piping occurred, the hydraulic well with a 1.0 m water level reduced the seepage velocity by up to 86%. This is because the difference in the water level between the riverside and the protected side is reduced, and it resulted in reducing the seepage pressure. As a result of the theoretical and numerical hydraulic gradient analysis according to the change in the water level of the hydraulic well, the hydraulic gradient decreased linearly according to the water level of the hydraulic well. From the results according to the location of the hydraulic well, installation of it at the point where piping occurred was found to be the most effective. A hydraulic well is a good device for preventing the piping of an embankment if it is installed at the piping point and the proper water level of the hydraulic well is applied.

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Numerical Study of Gas Production from a Methane Hydrate Reservoir by Depressurization with Multi‐wells

Acta Geologica Sinica - English Edition ◽

10.1111/1755-6724.14658 ◽

2021 ◽

Author(s):

Shilong SHANG ◽

Lijuan GU ◽

Hailong LU

Keyword(s):

Methane Hydrate ◽

Numerical Study ◽

Gas Production ◽

Hydrate Reservoir

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Geomechanical Responses During Gas Hydrate Production Induced by Depressurization

Volume 8: Polar and Arctic Sciences and Technology; Petroleum Technology ◽

10.1115/omae2016-54217 ◽

2016 ◽

Author(s):

Ah-Ram Kim ◽

Gye-Chun Cho ◽

Joo-Yong Lee ◽

Se-Joon Kim

Keyword(s):

Methane Hydrate ◽

Fossil Fuel ◽

Gas Production ◽

Field Scale ◽

Production Well ◽

Physical Processes ◽

Hydrate Dissociation ◽

Thermal Changes ◽

New Energy ◽

Hydrate Bearing Sediments

Methane hydrate has been received large attention as a new energy source instead of oil and fossil fuel. However, there is high potential for geomechanical stability problems such as marine landslides, seafloor subsidence, and large volume contraction in the hydrate-bearing sediment during gas production induced by depressurization. In this study, a thermal-hydraulic-mechanical coupled numerical analysis is conducted to simulate methane gas production from the hydrate deposits in the Ulleung basin, East Sea, Korea. The field-scale axisymmetric model incorporates the physical processes of hydrate dissociation, pore fluid flow, thermal changes (i.e., latent heat, conduction and advection), and geomechanical behaviors of the hydrate-bearing sediment. During depressurization, deformation of sediments around the production well is generated by the effective stress transformed from the pore pressure difference in the depressurized region. This tendency becomes more pronounced due to the stiffness decrease of hydrate-bearing sediments which is caused by hydrate dissociation.

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