Surfactant waterflooding enhanced oil recovery process

摘要

Disclosed is an improved surfactant waterflooding enhanced oil recovery process employing a fluid containing as substantial in the only anionic surfactant, an ethoxylated and sulfated or ethoxylated and sulfonated surfactant. The degree of ethoxylation of the surfactant is determined by determining the degree of ethoxylation which produces the first inflection point in the electrical conductivity of a fluid as the degree of ethoxylation is increased from a value below that which causes solubility of the fluid in the aqueous environment in which it is tested to a value slightly greater than borderline solubility. Optimum results are obtained if the average degree of ethoxylation of the ethoxylated and sulfated or ethoxylated and sulfonated surfactant is from n-0.2 to n+0.1 and preferably from n-0.15 to n+0.05, where n is the degree of ethoxylation corresponding to the first inflection point in electrical conductivity.