A parametric analysis of capillary pressure effects during geologic carbon sequestration in a sandstone reservoir

During carbon capture and sequestration, capillary forces and buoyancy effects strongly influence CO2 migration and plume geometry. To understand interactions between these processes, we implement a numerical modeling experiment of CO2 injections in a sandstone reservoir to understand how parametric variability reported in the literature affects numerical predictions of CO2 migration. We simulate ten years of supercritical CO2 (scCO(2)) injections for 189 unique parameter combinations (entry pressure, P-o, and van Genuchten fitting parameter, lambda) that control the van Genuchten capillary pressure model. Results are analyzed on the basis of a dimensionless ratio, omega, which is a modified Bond number that defines the relationship between buoyancy pressure and capillary pressure. When omega > 1, buoyancy governs the system and CO2 plume geometry is governed by upward flow. In contrast, when omega < 1, then buoyancy is smaller than capillary force and lateral flow governs CO2 plume geometry. We show that the omega ratio is an easily implemented screening tool for qualitative assessment of CO2 distribution characteristics. We also show how parametric variability affects the relationship between buoyancy and capillary force, and thus controls CO2 plume geometry: (1) small entry pressure P-o encourages vertical flow and large entry pressure P-o inhibits vertical flow; and (2) the van Genuchten fitting parameter lambda exhibits minimal control on the spatial distribution of CO2, as evidenced by the 2 x difference between the partial differential omega/ partial differential P-o and partial differential omega/ partial differential lambda gradients quantified using response surface analysis of the omega ratio. (c) 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.