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 M –Ca –k 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.