5:15 PM - 6:30 PM
[HSC05-P10] Estimation of sub-seafloor temperature for underground CO2 storage using self-sealing of CO2 hydrate
Keywords:underground storage of CO2, CO2 hydrate, seafloor temperature
Carbon dioxide (CO2) capture and storage (Carbon Capture and Storage, CCS), which is an option for global warming countermeasures, is expected as a medium- to long-term technology by adding to the conventional reliable supply chain to achieve both stable power supply and decarbonization. In the 1990s, there were multiple storage options, such as marine storages, but there is aquifer storage ( deep saline storage, DSA) in Japan at this moment. On the other hand, since there are multiple options for CO2 capture, there should be multiple storage options to carry out CO2 storage at needed time. Therefore, we are studying CO2 storage options focusing on the properties of CO2 hydrate.
CO2 hydrate is a solid that made from both water(H2O) and CO2, and there is a phase diagram of CO2 hydrated between temperature and pressure.
The representative temperature and pressure in the phase diagram, that is the quadruple point, is less than or equal to 10 C and more than or equal to 4.5 MPa. At the quadruple point, four phases of water, liquid CO2, CO2 gas and CO2 hydrate exist at the same temperature and pressure.
There are oceanic offshore regions around Japan where CO2 hydrate can exist based on the phase diagram.
We assumes ocean basins as storage sites where sediments transported from land rivers are accumulated.
Vertical temperature distribution of the layers is estimated by both the temperature of sea floor and geothermal gradients, because CO2 hydrate storage is mainly controlled by temperature and pressure.
In particular, the temperature of the seafloor can be evaluated from the vertical temperature distribution of seawater. Therefore, the vertical distribution was arranged using about 1.75 million points of public data (Argo project) shallower than 2,000 m in the sea around Japan. The data was divided into 6 oceanic regions such as the Pacific Ocean and the Sea of Japan, and the vertical temperature distribution of the seawater temperature in each oceanic region was draw in a graph, since the higher latitudes, the higher the temperature at the same water depth. The results will be reported.
CO2 hydrate is a solid that made from both water(H2O) and CO2, and there is a phase diagram of CO2 hydrated between temperature and pressure.
The representative temperature and pressure in the phase diagram, that is the quadruple point, is less than or equal to 10 C and more than or equal to 4.5 MPa. At the quadruple point, four phases of water, liquid CO2, CO2 gas and CO2 hydrate exist at the same temperature and pressure.
There are oceanic offshore regions around Japan where CO2 hydrate can exist based on the phase diagram.
We assumes ocean basins as storage sites where sediments transported from land rivers are accumulated.
Vertical temperature distribution of the layers is estimated by both the temperature of sea floor and geothermal gradients, because CO2 hydrate storage is mainly controlled by temperature and pressure.
In particular, the temperature of the seafloor can be evaluated from the vertical temperature distribution of seawater. Therefore, the vertical distribution was arranged using about 1.75 million points of public data (Argo project) shallower than 2,000 m in the sea around Japan. The data was divided into 6 oceanic regions such as the Pacific Ocean and the Sea of Japan, and the vertical temperature distribution of the seawater temperature in each oceanic region was draw in a graph, since the higher latitudes, the higher the temperature at the same water depth. The results will be reported.