2:30 PM - 2:45 PM
[HSC06-04] Earthquake response analysis of CO2 storage site using hydraulic-mechanical coupled analysis by numerical manifold method - Compare flat model and anticline model-
Keywords:earthquake response analysis, hydraulic-mechanical coupled analysis, numerical manifold method, CO2 storage site
A big earthquake causes strong seismic wave with long duration. In the case of the 2011 off the Pacific Coast of Tohoku Earthquake, duration of strong motion is more than six minutes and long-period seismic wave causes large displacement in wide area of the Japan island. We have little knowledge about the effects of such long period strong motion on fluid saturated layers at depth. Consequently, evaluating the integrity of CO2 containment during earthquakes is one of the important issues in Japan.
We developed a method to evaluate the pore pressure build up due to deformation and fluid migration caused by an earthquake, and the integrity of the containment of the storage sites1).
This method evaluates the integrity by the safety factor response from the effective stress solved by the hydraulic-mechanical coupling analysis using NMM(Numerical Manifold Method). In this paper, we applied the method on the flat and anticline models to study and the safety factor response is investigated.
Figure 1. shows the flat and anticlinal models, and the boundary conditions used in NMM. The horizontal length of the model is 2000 meters and the vertical length is 1700 meters. The drained boundary is defined at the upper boundary. The viscose boundary is attached at both the left and right sides as a Lysmer damper (Kuhlemeyer, R.L. and Lysmer, 1973). The fixed boundary is given at the bottom boundary. The monitor elements are set up in the Layer 8 (CO2 Storage reservoir) and Layer 4 (Cap rock), as shown in Figure 1. We apply an acceleration record of Chuetu Earthquake (2004) (up to 200 gal) as input to the model (Figure 2.). Table 1. shows the material properties used for the analysis. Figure 3. shows the pore-pressure response of the flat model and the anticline model in the monitor elements of cap rock and CO2 storage reservoir. The maximum amplitudes of pore-pressure response between the flat model and anticline model are equal or slightly greater for the anticline model. In the anticline model, the pore-pressure response value does not decrease with time. Figure 4. is the local safety factors variation in the monitor elements of cap rock and CO2 storage reservoir. It shows that the local safety factor response of the flat model is smaller than that of the anticline model, especially after 19 seconds.
1) Sasaki, T., Horikawa, S., Kusunose, K., Hashimoto, R.:Seismic Response in the Hydraulic-Mechanical Coupling Analysis of a CCS Site Model by NMM, ARMA20-1530,American Rock Mechanics Association, 2020.
We developed a method to evaluate the pore pressure build up due to deformation and fluid migration caused by an earthquake, and the integrity of the containment of the storage sites1).
This method evaluates the integrity by the safety factor response from the effective stress solved by the hydraulic-mechanical coupling analysis using NMM(Numerical Manifold Method). In this paper, we applied the method on the flat and anticline models to study and the safety factor response is investigated.
Figure 1. shows the flat and anticlinal models, and the boundary conditions used in NMM. The horizontal length of the model is 2000 meters and the vertical length is 1700 meters. The drained boundary is defined at the upper boundary. The viscose boundary is attached at both the left and right sides as a Lysmer damper (Kuhlemeyer, R.L. and Lysmer, 1973). The fixed boundary is given at the bottom boundary. The monitor elements are set up in the Layer 8 (CO2 Storage reservoir) and Layer 4 (Cap rock), as shown in Figure 1. We apply an acceleration record of Chuetu Earthquake (2004) (up to 200 gal) as input to the model (Figure 2.). Table 1. shows the material properties used for the analysis. Figure 3. shows the pore-pressure response of the flat model and the anticline model in the monitor elements of cap rock and CO2 storage reservoir. The maximum amplitudes of pore-pressure response between the flat model and anticline model are equal or slightly greater for the anticline model. In the anticline model, the pore-pressure response value does not decrease with time. Figure 4. is the local safety factors variation in the monitor elements of cap rock and CO2 storage reservoir. It shows that the local safety factor response of the flat model is smaller than that of the anticline model, especially after 19 seconds.
1) Sasaki, T., Horikawa, S., Kusunose, K., Hashimoto, R.:Seismic Response in the Hydraulic-Mechanical Coupling Analysis of a CCS Site Model by NMM, ARMA20-1530,American Rock Mechanics Association, 2020.