Abstract: A method is disclosed in which the production of petroleum is improved or reinstated in formations that have been partially depleted by primary recovery techniques or where the communication between the injection well and the production well has been restricted by the swelling of water sensitive clays in the formation. In this method an aqueous fluid comprising polysaccharide in sufficient concentration to increase the viscosity of the aqueous fluid, a water soluble quanidine compound and a naturally occurring salt is injected into the formation through an injection well and petroleum and aqueous fluids are produced through a production well.

Abstract: In a surfactant flooding process for recovering oil from a subterranean petroleum reservoir, surfactant loss by adsorption onto the mineral grains of the reservoir matrices is reduced by the addition to the surfactant solution of a sacrificial agent selected from the group consisting of polybasic carboxylic acids, their water soluble salts and mixtures thereof.