CHARACTERIZATION OF WATERFLOOD SATURATION PROFILE HISTORIES BY THE COMPLETE CAPILLARY NUMBER

A simple capillary model of free spontaneous imbibition and waterflood is introduced and used to interpret the 'complete' capillary number C A for immiscible displacement in porous media. The 'complete' capillar y number is applied to characterize saturation profile histories obtai ned in sandpacks. Its value is equal to I in free spontaneous imbibiti on, and in a waterflood it is equal to the ratio of the water injectio n rate to the initial rate of free spontaneous imbibition. In situ sat uration profiles in waterfloods in sandpacks at 1:1 viscosity ratio we re determined by light transmission measurement. For CA much less than 1 capillary forces controlled and the saturation rose practically uni formly along the entire length of the model from the initial connate w ater saturation to the final value, corresponding to residual oil satu ration. For CA much greater than 1 viscous forces controlled and there was a step change in saturation from the connate water to the residua l oil value, advancing as a piston. At intermediate values of CA the s aturation profiles were S-shaped curves. The saturation profile histor ies in two packs of different lengths of the same sand were identical, within experimental error, at the same values of CA in the two packs, if plotted against normalized distance coordinates. The saturation pr ofile histories measured in packs of the same length of two very diffe rent sands A and B were found to be similar for values of CA in the ra tio (CA)(B)/(CA)(A) approximate to 5, for all values of CA.