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

[HSC06-P04] Optical fiber sensing CT imaging coupling for observing CO₂ movement in rock cores

*Hyuck Park^1,2, Ziqiu Xue^1,2 (1.RITE(Research Institute of Innovative Technology for the Earth), 2.Geological Carbon dioxide Storage Technology Research Association)

Keywords:CO2 migration, Optical fiber sensing, X-ray CT imaging

A laboratory experiment was conducted to simulate CO₂ migration in the rocks surrounding an injection well. This involved CO₂ injection into a core-scale sandstone sample. A single optical fiber was utilized as a distributed sensor in this study. We compared the CO₂ migration distance confirmed by the X-ray CT imaging with the distance confirmed by the response of the optical fiber sensing. The purpose of this study is to verify whether the migration of CO₂ confirmed in CT is also significantly confirmed in optical fibers. Sarukawa sandstone (diameter: 34.83mm, length: 179.50mm, Japan) was used in this study. It has a relatively homogeneous structure and has partially irregularly shaped grains and voids. The porosity of the specimen determined by X-ray CT imaging is approximately 25.1%. The permeability is about 5 mDarcy. 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 12MPa. The optical fiber was spirally bonded around the specimen. Dry condition specimen was first saturated with KI aqueous solution (11.5 wt%) then a permeability measurement was performed. For the CO₂ injection, the upstream pump was prepared at 10.5 MPa for differential pressure of 0.5MPa. And the syringe pump on the downstream side was controlled to maintain 10MPa during the experiment. For the optical fiber measurement, we recorded the Rayleigh frequency of light passing through the optical fiber with a special device. The optical fiber measurement and X-ray CT imaging were performed in all experimental steps.

Comparison of differential images obtained from X-ray CT imaging at the start of entry, 1/4, 2/4, 3/4, and 4/4 (breakthrough) with strains obtained from fiber optic sensing corresponding to each time point shows that both represent CO₂ migration well. In detail, the results of the fiber measurement are slightly ahead of those of the CT imaging. This means that the strain is progressing ahead of the CO₂ migration. This suggests that optical fiber sensing information can serve as a sensor indicating CO₂ migration within rocks. We expect that the optical fiber sensor will be a good tool for monitoring the stability of CO₂ storage.