Abstract
The relative roles of parameters governing relative permeability, a crucial property for two-phase fluid flows, are imperfectly 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 using the lattice Boltzmann method. We applied the Euler–Poincaré characteristic to quantify the morphology of both fluids. We show thatk nw increases and k wdecreases as M increases due to the lubricating effect and instability at fluid interfaces resulting from viscosity contrast. We also show that k nw decreases markedly at lowCa (log Ca < −1.25), whereask w undergoes negligible change with changingCa . An MCak nwcorrelation diagram, displaying the simultaneous effects of M andCa , shows that they cause k nw to vary by an order of magnitude, an effect not incorporated in current estimation techniques.