Experimental and visual analysis of co- and counter-current spontaneous imbibition for different viscosity ratios, interfacial tensions, and wettabilities

We analyzed the dynamics of spontaneous imbibition using core and sand pack (made of transparent glass beads) visualization experiments. The effects of the critical factors such as temperature, wettability, gravity, oil viscosity, interfacial tension (IFT), and matrix boundary conditions on the process were studied. First, data were collected through experiments conducted on Berea sandstone samples for air-water and oil-water pairs. The samples were coated to ensure co-current and counter-current type interaction. To support the observations obtained through the core scale experiments, visual data obtained from 2-D sand pack models were used. This was helpful in depicting the phase distribution in the matrix and defining the causes of the residual non-wetting phase saturation. Significant differences were observed between oil-water and air-water capillary imbibition dynamics and phase distribution in the matrix. For the air-water pair, it was noticed that more fingering occurs as the temperature is increased. For horizontal orientation, in the absence of gravity effect, the wetting phase invasion developed from a single point as a single finger and displacement was achieved by the growth of this finger, which was much thicker in case of mineral oil compared to the kerosene case. The same was observed for the aged (less water-wet case). For co-current interaction, when the two (bottom and top parts) sides are in contact with the wetting phase, fingering was remarkable for the high viscosity oil. Finally, a quantitative analysis was performed by testing different dimensionless groups. Modifications to them were suggested to have a robust dimensionless group that covers all the parameters considered and to be used further in the scaling applications. (C) 2009 Elsevier B.V. All rights reserved.