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[HSC06-10] Numerical simulation of mechanical stability during CO2 underground storage using gas hydrate
Keywords:CO2 underground storage, gas hydrate, ground deformation
A carbon dioxide sequestration method (CCS) using gas hydrate has recently been proposed, in which CO2 is stored underground in the form of CO2-hydrate. In this method, CO2 and seawater will react under the gas hydrate equilibrium conditions, namely, high pressure and low temperature conditions so that CO2 is stored as a solid in a chemically stable condition. It is possible that CO2 is stably stored compared with a conventional method using supercritical CO2 injection. In addition, the suitable geological area for the storage would be large since the caprock is not necessary.
In the present study, two-phase fluid–solid coupled analysis has been conducted to reproduce the ground deformation during CO2 underground storage a hydrate. Solid phase (soil, hydrate) and two liquid phases (CO2, water) are dealt with in the numerical analysis. An elasto-viscoplastic constitutive models are used for CO2 hydrate-bearing sediment. As a capillary pressure- saturation relation, van Genuchten model is used. Finite element method and Newmark’s β method is used as a discretization in space and time, respectively.
As a simulation example, the mechanical stability of the ground by CO2 liquid injection is examined, assuming a hydrate seal layer with a thickness of 2 m is formed in the seafloor ground at a water depth of 1000 m. Simulation results will be discussed regarding to the change of water pressure, CO2 liquid pressure, saturation, effective stress, and the soil deformation during CO2 liquid injection.
Akaki, T., Kimoto, S. and Oka, F., Chemo-thermo-mechanically coupled seismic analysis of methane hydrate-bearing sediments during a predicted Nankai Trough Earthquake, Int. J. for Numerical and Analytical Methods in Geomechanics, Vol. 40, pp. 2207–2237, DOI: 10.1002/nag.2527, 2016
Yoshimoto, M., Kimoto, S., Undrained creep behavior of CO2 hydrate-bearing sand and its constitutive modeling considering the cementing effect of hydrates, Soils and Foundations, Vol. 62, 2022. https://doi.org/10.1016/j.sandf.2021.101095
In the present study, two-phase fluid–solid coupled analysis has been conducted to reproduce the ground deformation during CO2 underground storage a hydrate. Solid phase (soil, hydrate) and two liquid phases (CO2, water) are dealt with in the numerical analysis. An elasto-viscoplastic constitutive models are used for CO2 hydrate-bearing sediment. As a capillary pressure- saturation relation, van Genuchten model is used. Finite element method and Newmark’s β method is used as a discretization in space and time, respectively.
As a simulation example, the mechanical stability of the ground by CO2 liquid injection is examined, assuming a hydrate seal layer with a thickness of 2 m is formed in the seafloor ground at a water depth of 1000 m. Simulation results will be discussed regarding to the change of water pressure, CO2 liquid pressure, saturation, effective stress, and the soil deformation during CO2 liquid injection.
Akaki, T., Kimoto, S. and Oka, F., Chemo-thermo-mechanically coupled seismic analysis of methane hydrate-bearing sediments during a predicted Nankai Trough Earthquake, Int. J. for Numerical and Analytical Methods in Geomechanics, Vol. 40, pp. 2207–2237, DOI: 10.1002/nag.2527, 2016
Yoshimoto, M., Kimoto, S., Undrained creep behavior of CO2 hydrate-bearing sand and its constitutive modeling considering the cementing effect of hydrates, Soils and Foundations, Vol. 62, 2022. https://doi.org/10.1016/j.sandf.2021.101095