A method of enhanced oil recovery in which a mixture of detergents, alcohols, and other solvents is pumped into the porous oil-bearing strata, followed by much brine, which furnishes the pressure necessary to drive the mixture through the rocky structure. Field tests show this process to be no more than 50% efficient, and it will probably not be important in secondary oil recovery for some years. Another technique, called micellar flooding, involves the use of surfactants and a mixture of water and a high polymer. It is a two-step process: the surfactants (petroleum sulfonate and alcohol) are injected into the oil-bearing strata, followed by the water-polymer mixture. Volumes of these materials are required.See Hydraulic Fracturing.