A PARAMETRIC ANALYSIS OF CAPILLARY PRESSURE EFFECTS DURING THE CARBON SEQUESTRATION INJECTION PROCESS IN A SANDSTONE RESERVOIR

Geological Carbon Sequestration (GCS) is considered a key method to mitigate the climate change problem caused by excessive CO₂ emission. During the past decades, numerical simulation has been treated as one technique for better understanding the injection, migration and leakage of supercritical CO₂ (scCO₂) during GCS process. Capillary pressure (P_cap) is an important factor affects the subsurface multiphase movement. However, the influence of capillary pressure on scCO₂ migration at reservoir scale during the GCS process has not been deeply understood. Nowadays the laboratory method is maturely utilized to obtain constitutive models of P_cap as a function of wetting phase saturation (S_w) at core-scale. As a result, it arouses uncertainty problems when applying laboratory-measured P_cap model to field-scale GCS simulations. Five combinations of Van Genuchten capillary pressure model quantitatively represent a large variance of capillary pressure experimental core-scale measurements. In this study, a ten years injection of scCO₂ within a 2-D radially symmetric sandstone reservoir is simulated for the five combinations of the van Genuchten model parameters λ and entry pressure (P₀). Small P₀ encourages vertical flow and large P₀ inhibits vertical flow. The parameter λ controls the curvature of the van Genuchten model and affects the position of vertical flow. For small λ, the curve shows an “S” shape and the upward flow increases from the edge of the plume to the injection well side. Oppositely, large λ, the curve is more plat and the upward flow is inhibited as in the plume developing direction. Simulation results demonstrate that P₀ governs CO₂ movement to a larger degree comparing to that of λ.