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Spontaneous imbibition 299

Figure 10.11 Oil recovery factor versus the scaled or normalized time (Sheng, 2013b).

Figure 10.12 Effect of Bond number on trapping of residual oil saturation. Data from
Morrow, N.R., Songkran, B., 1981. Effect of viscous and buoyancy forces on nonwetting
phase trapping in porous media. In: Shah, D.O. (Ed.), Surface Phenomena in Enhanced Oil
Recovery. Plenum Press, 387e411.

cocurrent for the two phases. Bourbiaux and Kalaydjian’s (1990) relative
permeability data showed that cocurrent relative permeabilities were higher
than countercurrent values for capillary-dominated flow. For intermediate
values of the bond number (0.5 e 5 according to Schechter et al. (1994)),
the gravity contribution is strong enough to cause considerable segregation
of the flow, and the capillary force is also strong enough. Schechter et al.’s
(1994) experimental data showed that the combined effects of gravity and
IFT led to faster recovery of the nonwetting phase than that observed by
either gravity-dominated or capillary-dominated flow. The above discus-
sions apply to conventional reservoirs.