[H-SC04] CCUS (Carbon Dioxide Capture, Utilization, and Storage) for Climate Mitigation

[HSC04-P01] Pressure transfer and CO₂ migration detection in highly permeable specimen by fiber optic sensor

*Hyuck Park¹, Ziqiu Xue¹ (1.Research Institute of Innovative Technology for the Earth)

Keywords:fiber optic sensor, X-ray CT imaging, CO2 migration, pressure transfer

When CO₂ is injected into a water-saturated underground, it is predictable that a pressure gradient due to the CO₂ injection will occur in the underground, which was in a pressure equilibrium state, and then mass transfer of CO₂ will occur. Based on this point, we performed CO₂ injection & optical fiber measurement experiments using core-scale sandstone. In this study, a single optical fiber was used as a distributed fiber optic sensor. Migration of CO₂ in the specimen was confirmed by X-ray CT images. The goal of this experiment is to measure and detect the transfer of pressure and the movement of CO₂ that occur when CO₂ is injected into the storage using optical fibers. The results of the indoor experiment will be the basic data for the field experiment. Highly permeable sandstone (120mDarcy, diameter: 37.4mm, length: 139.6mm) was used for this study. It has a relatively homogeneous structure, with dense grains irregularly distributed. It has bedding in the direction perpendicular to the axis. Microbubble filter (diameter: 34.4mm, 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 29.9%. 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%). We continuously checked the reaction of the optical fiber from when the specimen was saturated with KI aqueous solution to during the permeability measurement. Next, supercritical CO₂ was injected into the specimen saturated with KI aqueous solution, and CO₂ migration was measured using both X-ray CT and optical fiber. The CO₂ injection rate was maintained at 0.5 mL/min.
・According to pressure gauge data (recorded at 1-minute intervals), the downstream pressure gauge responded within 2 minutes after the syringe pump started CO₂ injection. That is, it can be seen that the pressure transmission within the specimen was transmitted within 2 minutes.
・According to the optical fiber data (recorded at 5-minute intervals), swelling was confirmed throughout the specimen at 2 minutes after starting the syringe pump.
・According to the CT data, the movement of CO₂ in the specimen was confirmed from the recording of 3 minutes after the syringe pump was started.
So, to conclude, in the case of a specimen with high permeability like this specimen, it can be seen that the pressure transmission by CO₂ injection precedes the movement of CO₂, and this can be measured by the optical fiber. It was concluded that by using a fiber optic sensor, it is possible to predict CO₂ transport.