[H-SC05] CCUS (Carbon Dioxide Capture, Utilization, and Storage) for Climate Mitigation

[HSC05-P01] Measurement of Relative Permeability using CT image processing

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

Keywords:Relative permeability, X-ray CT imaging, steady-state, CO2 saturation

Relative permeability is the basic information necessary for CO₂ storage studies. However, in most cases, a considerable amount of time is required to measure the relative permeability using CO₂. We have been studying steady-state confirmation in specimens using X-ray CT imaging over the years. In this study, we introduce an example of obtaining a conventional steady-state relative permeability using a small size specimen by CT image processing. We used homogeneous sandstone (diameter: 37.60mm, length: 33.05mm, Japan) in this study. The porosity of the specimen determined by X-ray CT imaging is 16.06%. The permeability is about 6mDarcy. 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 18MPa. In consideration of the water permeability of the specimen, the total flow rate was set to 0.2 mL/min. Water and CO₂ were simultaneously injected into the specimen at each ratio. Totally 4 different co-injection rates (water:CO₂, 9:1, 5:5, 1:9, 0:10) were used. We independently made the criteria for determining steady-state using CT image processing. Co-injected CO₂ preferentially flowed through the upper part of the specimen in step1.In step2, CO₂ preferentially flowed through the outer portion of the sample, and from then on, it flowed through the entire specimen. Initially, there was little difference in the CO₂ saturation gradient of the specimen, but later, the CO₂ saturation in the injection portion was greater than that of the discharge portion. In this study, we focused on the determination of the steady-state in the specimen required to measure the relative permeability using X-ray CT imaging. By using CT imaging, it was possible to confirm the distribution of CO₂ and water inside the specimen at each relative permeability test step. Even when the steady-state was determined at each step, the axial CO₂ saturation of the specimen was gradually tilted. This cannot be confirmed without observation using CT imaging. If the temperature and pressure are well controlled during the experiment, it is considered that the relative permeability measurement method using CT imaging can be an alternative to the conventional relative permeability measurement method.