Presentation Date: Feb 14, 2026
AGSA Abstract
Capillary trapping of supercritical CO₂ (scCO₂) is a critical mechanism that contributes to the long-term security of geologic carbon storage. The pore-scale processes that govern trapping efficiency particularly under repeated drainage–imbibition (D–I) cycles remain insufficiently understood. To address this gap, we conducted a series of core-scale experiments to quantify how capillary trapping evolves during multiple flow cycles in Bentheimer sandstone. Experiments involved three consecutive cycles of primary drainage and secondary imbibition using scCO₂ and deionized water under reservoir-relevant conditions of 40 °C and 1250 psi. The cylindrical Bentheimer core measured 6 inches in length, 1.5 inches in diameter, and had a porosity of 20%. Differential pressure across the core was recorded continuously to capture dynamic displacement behavior. Drainage produced sharp increases in differential pressure due to capillary resistance as scCO₂ invaded water-filled pores, whereas imbibition generated smaller pressure rises consistent with more favorable displacement under water-wet conditions. Calculated capillary numbers for drainage and imbibition were 6.27×10⁻⁷ and 1.14×10⁻⁵, respectively, indicating stronger capillary dominance during drainage and reduced resistance during imbibition. Both drainage and imbibition phases were performed under uninterrupted flow, and capillary trapping was inferred from the pressure response. Sharp pressure spikes reflected resistance from disconnected ganglia and pore-scale trapping events. Residual scCO₂ saturations after each cycle were quantified using volumetric pump balance calculations. Preliminary results show increasing trapped scCO₂ volumes with each successive D–I cycle, consistent with pore-scale hysteresis and progressive enhancement of capillary trapping. This experimental work forms part of a larger effort to link pore-scale processes to core- and reservoir-scale storage performance. Ongoing analyses include high-resolution micro-CT imaging of selected samples and pore-network modeling to simulate multiphase flow and validate experimental trends. By integrating core-scale experiments with imaging and modeling, this research aims to improve predictions of CO₂ retention and support the design of more secure strategies.
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