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  • Threshold capillary pressur...
    Vespo, Vincenzo Sergio; Messori, Alessandro; Musso, Guido

    International journal of greenhouse gas control, June 2024, 2024-06-00, Volume: 135
    Journal Article

    •Insight on the physical processes related to the dynamic and the residual method.•The correct effective discharge is difficult to assess experimentally using the dynamic method.•Dynamic overestimation < 15 % if the ratio between the estimate and the pressure drop is > 0.70.•The residual capillary pressure is not a property of the material.•Using bigger vessels and imposing higher overpressures the residual estimate is more accurate. The dynamic threshold pressure method and the residual capillary pressure method provide an estimate of the threshold capillary pressure for CO2 storage. In the dynamic method, the threshold capillary pressure is determined by comparing the discharge measured when the CO2 starts flowing into the sample with the one measured when only water is flowing. In the residual method, a high CO2 pressure is applied on the vessel at the inlet of a water-saturated sample while water cannot flow from the vessel at its end. The threshold capillary pressure is estimated as the difference between the CO2 and the water pressures at the sample boundaries at equilibrium conditions. Sensitive analyses showed the impact of material properties and experimental conditions on results. Both methods allow estimating the threshold capillary pressure within a few days and the estimates are influenced by the applied pressures. The dynamic method estimate is not precautionary, and it tends to the exact value as the applied CO2 overpressure decreases. The residual method estimate is influenced by the drainage conditions and the volume of the vessels: it is generally precautionary and tends to increase with the volume of the vessels and the applied pressure. Suggestions for test interpretation and planning are also provided.