[H-SC06] CCUS (Carbon Dioxide Capture, Utilization, and Storage) for Climate Mitigation

[HSC06-17] Reservoir-Scale Simulation of CO2 Hydrate Formation in Sediments under Saline Conditions

Shen Chen¹, *Toru Sato¹, Yosuke Sawano², Kazuhiro Tada², Takaomi Tobase³ (1.University of Tokyo, 2.Geosphere Environmental Technology, 3.J Power)

Keywords:Carbon Dioxide Capture and Storage (CCS), CO2 Hydrate, Reservoir Scale Simulation, Saline Condition

Carbon dioxide capture and storage (CCS) has been proposed as an effective means of mitigating global warming. In Japan, in addition to storing CO2 in depleted oil fields under the seabed or in saline aquifers under caprock, a CO2 storage method is also being considered in which liquid CO2 is injected into the hydrate stable zone of a low-temperature, high-pressure aquifer. The formation of gas hydrate is expected to have a shielding effect against leakage. Therefore, it is necessary to accurately evaluate the shielding effect of CO2 hydrate, which depends on the natural environment and storage conditions. The injected CO2 rises and becomes gas hydrate near the Bottom Simulating Reflector (BSR), and the shielding effect of CO2 hydrate formation can be confirmed. The natural environment and injection conditions ensure that the injected CO2 is safely stored under the formed hydrate layer. Previous studies have only discussed conditions under freshwater, and no study has been conducted on CO2 storage purposes under saltwater conditions. Salinity has a significant effect on the formation conditions of CO2 hydrate, especially its phase equilibrium based on pressure and temperature. In this study, we aim to develop a CO2 hydrate phase equilibrium model for salinity that has an inhibitor effect on hydrate formation, and to examine a method to stably store CO2 using hydrate within a finite time that can be monitored by private companies. The developed mathematical model of CO2 hydrate phase equilibrium was implemented in a reservoir-scale simulator, and case study simulations were performed, suggesting the possibility of storing CO2 under the seafloor even under saline conditions, and demonstrating the difficulty of storing CO2 hydrate under saline conditions in particular, and the necessity of comprehensively adjusting various factors to maintain stable hydrate formation.