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[HSC05-16] Experimental Study on Formation Behavior of CO2 Hydrate in a Flow Field Assuming Carbon Dioxide Storage in Subseabed
Keywords:Storage in subseabed, CO2 Hydrate, Sealing ability
In order to realize CO2 underground storage in Japan, we propose CO2 storage in subseabed using CO2 hydrate in addition to storage in aquifers. In this method, it is expected that injected CO2 will form hydrate during its rising process and become a seal layer by clogging pores. Therefore, caprock is unnecessary in this method, and it is expected that the storage site will be expanded and the storage cost will be reduced. However, there is a concern about CO2 leakage due to the lack of the sealing ability of CO2 hydrate.
In this study, liquid CO2 was injected into the Toyoura sand core under pressure and temperature conditions simulating the water depth of 600 m and the seabed depth of 150 m below the seafloor. We investigate whether the CO2 hydrate could yield a sealing function as a caprock.
In our previous experiment, liquid CO2 was injected into a short core (200 mm in height and 50 mm in diameter) at the same rate as the rising rate due to buoyancy. Due to the limitation of core volume, liquid CO2 could not be injected continuously; thus, it was injected intermittently. CO2 hydrate formation was confirmed about 36 hours after the start of injection. After confirming the CO2 hydrate formation, liquid CO2 was injected again. The pressure near the core inlet suddenly increased, and blockage by CO2 hydrate was confirmed. However, the method of intermittent injection of liquid CO2 is different from the actual field operation, which assumes continuous injection.
In this study, we investigate hydrate formation behaviors and sealing function in the flow field by injecting liquid CO2 continuously using a long core (734 mm in height and 50 mm in diameter). CO2 hydrate formation was confirmed around the upstream side of the core about 17.5 hours after the start of injection. After the first hydrate formation around the upstream side of the core, hydrate formation was also confirmed downstream of the core. However, blockage due to hydrate formation was not confirmed. The result indicates that hydrate was formed heterogeneously. In addition, a phenomenon that seemed to be a redistribution of hydrate with time was observed.
In this study, liquid CO2 was injected into the Toyoura sand core under pressure and temperature conditions simulating the water depth of 600 m and the seabed depth of 150 m below the seafloor. We investigate whether the CO2 hydrate could yield a sealing function as a caprock.
In our previous experiment, liquid CO2 was injected into a short core (200 mm in height and 50 mm in diameter) at the same rate as the rising rate due to buoyancy. Due to the limitation of core volume, liquid CO2 could not be injected continuously; thus, it was injected intermittently. CO2 hydrate formation was confirmed about 36 hours after the start of injection. After confirming the CO2 hydrate formation, liquid CO2 was injected again. The pressure near the core inlet suddenly increased, and blockage by CO2 hydrate was confirmed. However, the method of intermittent injection of liquid CO2 is different from the actual field operation, which assumes continuous injection.
In this study, we investigate hydrate formation behaviors and sealing function in the flow field by injecting liquid CO2 continuously using a long core (734 mm in height and 50 mm in diameter). CO2 hydrate formation was confirmed around the upstream side of the core about 17.5 hours after the start of injection. After the first hydrate formation around the upstream side of the core, hydrate formation was also confirmed downstream of the core. However, blockage due to hydrate formation was not confirmed. The result indicates that hydrate was formed heterogeneously. In addition, a phenomenon that seemed to be a redistribution of hydrate with time was observed.