On the role of the viscosity ratio during low-capillary-number forced imbibition in porous media
- Univ. of Patras (Greece). Dept. of Chemical Engineering ICE/HT-FORTH, Patras (Greece)
The role of the viscosity ratio K during forced imbibition in porous media is investigated theoretically using a new simulator, and experimentally based on displacements in model pore networks. Both theory and experiment show that K is an important parameter of microdisplacement in porous media, not only for intermediate and large capillary number values, but also for small values, say Ca < 10[sup [minus]6]. In the latter region the residual nonwetting saturation S[sub or], is virtually independent of Ca for K < 1, and increases weakly with decreasing Ca for K > 1. The unexpected result is that, even for very small values of Ca, S[sub or] decreases appreciably as K decreases, especially in the case of very good wettability. Simulations indicate that the effect of K on S[sub or] for low Ca values is enhanced as the contact angle decreases. The phenomenon is attributed to a synergistic effect between capillary microfingering and localized viscous forces. It must be emphasized that the velocity gradients which are created locally by the advance of a single meniscus, or of a wetting film, are sufficiently large to make viscous stresses important, even when the Ca value of the macroscopic flow is very low (say, of order 10[sup [minus]8]). A favorable viscosity ratio reduces the extent of capillary microfingering and thus increases the efficiency of microdisplacement, despite the fact that for Ca < [approximately]10[sup [minus]6] the viscous stresses are negligible on a macroscopic scale. Further work is needed to analyze the synergism between [kappa] and [theta][sub e] at low Ca values.
- OSTI ID:
- 7271345
- Journal Information:
- Journal of Colloid and Interface Science; (United States), Journal Name: Journal of Colloid and Interface Science; (United States) Vol. 165:2; ISSN 0021-9797; ISSN JCISA5
- Country of Publication:
- United States
- Language:
- English