17:15 〜 18:45
[HSC07-P01] CO2注入流量が岩石のCO2飽和度に与える影響
キーワード：CO2注入流量、X線CT画像処理、CO2飽和度
RITE (Research Institute of Innovative Technology for the Earth, Japan) has been conducting research on injecting microbubble CO2 into storage for over a decade. In general, the CO2 saturation of specimens used in indoor experiments is mainly affected by the porosity, permeability and structure of the specimen. CO2 migration within the specimen was confirmed using X-ray CT images. The goal of this experiment is to determine the effect of CO2 injection rate on CO2 saturation when injecting CO2 into storage. The results of the indoor experiment will serve as basic data for the field experiment. Highly permeable sandstone (95mDarcy, diameter: 37.4mm, length: 62.9mm) was used for this study. It has bedding inclined approximately 10 degrees to the specimen axis direction. Microbubble filter (diameter: 34.5mm, length: 5.0mm) was located in between distributor and core specimen in the upstream side. Porosity of the specimen determined by X-ray CT imaging is 30.1%. The experiment was conducted under the pressure and temperature conditions that simulate underground environments; pore pressure: 10MPa, temperature: 40 degrees Celsius. The confining pressure selected in this study was 15MPa. The specimen was first saturated with KI aqueous solution (11.5 wt%). The CO2 injection test was performed in a total of three cases. The first was 0.5mL/min, the second was 0.1 → 0.5 → 1 → 2 → 5 → 10mL/min, and finally the third was 5mL/min.
According to the CT image observation results, in Case-1 (0.5 mL/min), CO2 mainly passed near the outer surface of the core specimen rather than the center. In Case-2 (0.1 → 0.5 → 1 → 2 → 5 → 10mL/min), as the injection rate increased, CO2 overcame the bedding structure and ultimately resulted in an increase in CO2 saturation of the entire specimen. In Case-3 (5 mL/min), by referring to the results of Case-2 and initially setting a moderately high injection rate, high CO2 saturation in the specimen was created from the beginning of injection. In conclusion, as in this experiment, in the case of highly permeable core samples with permeability around 100 mD, rather than applying the CO2 injection rate of the existing frequently used value (decimal mL/min, e.g. 0.05 to 0.5 mL/min), it was confirmed that applying a sufficiently large value (e.g. 5 mL/min) is efficient. Since candidate rocks for storage layer (geological storage) will vary in type, determining the appropriate CO2 injection rate for each rock must be done first. Determining the CO2 injection rate appropriate for the candidate rock is a time-saving method that can achieve higher CO2 saturation.
According to the CT image observation results, in Case-1 (0.5 mL/min), CO2 mainly passed near the outer surface of the core specimen rather than the center. In Case-2 (0.1 → 0.5 → 1 → 2 → 5 → 10mL/min), as the injection rate increased, CO2 overcame the bedding structure and ultimately resulted in an increase in CO2 saturation of the entire specimen. In Case-3 (5 mL/min), by referring to the results of Case-2 and initially setting a moderately high injection rate, high CO2 saturation in the specimen was created from the beginning of injection. In conclusion, as in this experiment, in the case of highly permeable core samples with permeability around 100 mD, rather than applying the CO2 injection rate of the existing frequently used value (decimal mL/min, e.g. 0.05 to 0.5 mL/min), it was confirmed that applying a sufficiently large value (e.g. 5 mL/min) is efficient. Since candidate rocks for storage layer (geological storage) will vary in type, determining the appropriate CO2 injection rate for each rock must be done first. Determining the CO2 injection rate appropriate for the candidate rock is a time-saving method that can achieve higher CO2 saturation.