[HSC07-17] Numerical simulation of ground deformation during CO2 underground storage using gas hydrate
Keywords:carbon strage, gas hydrate, groun deformation, numericfal analysis
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, a chemo-thermo-mechanically 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 elastic and elasto-viscoplastic constitutive models are used for soil phase and ground deformation due to the phase change and the change of effective stress during CO2 injection will be reproduced. 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, laboratory tests by Tohidi et al. (2010) is simulated using one-dimensional finite element model. Tohidi et al. (2010) conducted CO2 injection tests into water saturated glass beads specimen under pressure of 6.3 MPa and observed hydrate formation due to convection of liquid CO2. Simulation results will be discussed regarding to the change of water pressure, CO2 liquid pressure, saturation, effective stress, and the soil deformation during hydrate formation.
Tohidi, B. et al., CO2 Hydrates Could Provide Secondary Safety Factor in Subsurface Sequestration of CO2, Environ. Sci. Technol., 44, 1509–1514, 2010.
In the present study, a chemo-thermo-mechanically 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 elastic and elasto-viscoplastic constitutive models are used for soil phase and ground deformation due to the phase change and the change of effective stress during CO2 injection will be reproduced. 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, laboratory tests by Tohidi et al. (2010) is simulated using one-dimensional finite element model. Tohidi et al. (2010) conducted CO2 injection tests into water saturated glass beads specimen under pressure of 6.3 MPa and observed hydrate formation due to convection of liquid CO2. Simulation results will be discussed regarding to the change of water pressure, CO2 liquid pressure, saturation, effective stress, and the soil deformation during hydrate formation.
Tohidi, B. et al., CO2 Hydrates Could Provide Secondary Safety Factor in Subsurface Sequestration of CO2, Environ. Sci. Technol., 44, 1509–1514, 2010.