Relative Permeability Variation Depending on Viscosity Ratio and Capillary Number
Natanael Suwandi, Fei Jiang, Takeshi Tsuji
Abstract
Abstract The relative roles of parameters governing relative permeability, a crucial property for two‐phase fluid flows, are incompletely known. To characterize the influence of viscosity ratio ( M ) and capillary number ( Ca ), we calculated relative permeabilities of nonwetting fluids ( k nw ) and wetting fluids ( k w ) in a 3D model of Berea sandstone under steady state condition using the lattice‐Boltzmann method. We show that k nw increases and k w decreases as M increases due to the lubricating effect, locally occurred pore‐filling behavior, and instability at fluid interfaces. We also show that k nw decreases markedly at low Ca (log Ca < −1.25), whereas k w undergoes negligible change with changing Ca . An M‐Ca‐k nw correlation diagram, displaying the simultaneous effects of M and Ca , shows that they cause k nw to vary by an order of magnitude. The color map produced is useful to provide accurate estimates of k nw in reservoir‐scale simulations and to help identify the optimum properties of the immiscible fluids to be used in a geologic reservoir.