Effect of Wetting-Phase Viscosity on Cocurrent Spontaneous Imbibition

Spontaneous imbibition is an important mechanism for oil recovery in naturally fractured reservoirs. Understanding the effects of fluid viscosity on spontaneous imbibition is important for the design of injection projects and the prediction of reservoir production performances. We previously focused on the effects of the nonwetting-phase viscosity on spontaneous imbibition (Meng Energy Fuels 2015, 29, 686−694), and we now investigate the effects of the wetting-phase viscosity on spontaneous imbibition. Different wetting-phase viscosities were obtained by mixing glycerol with synthetic seawater, and the wetting-phase viscosities varied from 1 to 61.5 mPa s. Experiments on cocurrent imbibition were conducted with both glass-bead and quartz-sand packings with different wetting-phase viscosities. The geometry of the glass bead was spherical and regular with a narrow size distribution, and the geometry of the quartz sand was angular and irregular with a wide size distribution. The residual oil saturation in gl...