This paper reports the effect of using black liquor and spent sulfite liquors, which emanate as effluent from Nowgong Paper Mill, Jagiroad, Assam, in enhanced crude oil recovery from Naharkotiya porous media. An attempt has been made to study the effect of interfacial tension of black liquor and how it affects the recovery of crude oil from the porous rock of Naharkotiya reservoir of Oil India Limited, Duliajan, Assam. The main constituent of black liquor is Na-lignosulfonate, an anionic water soluble surfactant. Addition of Na-lignosulfonate to crude oil emulsions gives rise to ultra-low inter-facial tensions between the oil and the aqueous phase, which are very much in demand in enhanced oil recovery projects. Reduction of interfacial tension leads to the release of residual oil droplets from the capillaries in the porous media, thereby increasing substantially the amount of petroleum obtainable from a given porous media.