Speaker
Description
Quantifying pore-scale fluid displacement mechanisms in CO2/brine system is critical for predicting multiphase flow behavior and trapping efficiency during geological CO2 storage. In this study, we image steady-state two-phase flow of brine and CO2 in a water-wet Bentheimer sandstone under reservoir conditions. An experimental approach utilizing differential X-ray imaging was developed to investigate pore-scale CO2 behavior during drainage conditions. This methodology enabled direct measurement of relative permeability and capillary pressure, as well as characterization of gas ganglia evolution within the pore space across a range of fractional flows under capillary-dominated conditions.
The measured CO2 relative permeability remains low during early stages of drainage over a wide saturation range, increasing to 0.24 only at 100% CO2 injection, corresponding to a gas saturation of 0.57. Image analysis reveals that CO2 initially occupies the largest pores and throats as small, disconnected ganglia, with fragmentation promoted by Roof snap-off. With increasing CO2 fractional flow, invasion extends into smaller pores and throats, allowing individual ganglia to coalesce and form a connected flow pathway. Gaussian curvature distribution exhibits a slightly positive mean curvature, consistent with positive capillary pressure and confirming a water-wet system. Capillary pressure estimated from interfacial curvature are in agreement with independent porous-plate measurements reported in the literature, demonstrating that curvature-based analysis provides reliable pore-scale capillary pressure estimates despite inherent uncertainties.
Overall, the results indicate that the low gas relative permeability observed in CO2/brine systems is an inherent feature governed by capillary-dominated displacement processes and frequent snap-off events. These mechanisms result in a poorly connected CO2 phase, yielding flow behavior that deviates from predictions based on invasion percolation models.
| Country | United Kingdom |
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| Student Awards | I would like to submit this presentation into the Earth Energy Science (EES) and Capillarity Student Poster Awards. |
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