The results of laboratory and field studies of the effect of additions of saponified fatty acids and disolvan (a polyalkylglycol ionic surfactant) on the interphase tension of filtrates of clayey solutions and on the coefficient of recovery of the phase permeability of productive oil-bearing formations are presented. It is shown that the uncovering of productive horizons with additions of saponified fatty acids to the drilling solution causes an increase in the phase permeability of sandy collectors with respect to oil.