Abstract A method of recovering oil from a subterranean formation using an aqueous surfactant solution with a predetermined and controlled viscosity. The ability of the surfactant composition to impart viscosity to the aqueous solution is dependent upon the weight ratio of hydrocarbon oil in the composition to the surfactants in the composition. This oil/surfactant weight ratio must be maintained within the range of 0.05 to 0.40 to obtain a surfactant composition having the ability to impart a desired viscosity to its aqueous solution. The ratio can be maintained within this range and varied in value to change the viscosityimparting properties of the surfactant composition by adjusting the deoiling process during the manufacture of the surfactant composition or by adding hydrocarbon oil to the surfactant composition.
A method as defined in claim 1 wherein the concentration of said surfactant in said solution is approximately two percent by weight.
Claim 2
Dependent Claim
58 words
A method as defined by claim 1 in which said surfactant is prepared by contacting a hydrocarbon feedstock containing at least ten percent by weight of the sulfonatable constituents present in a 700*-1100*F boiling range fraction of a petroleum crude with gaseous SO3 in a thin-film reactor and said oil is an unreacted portion of said hydrocarbon feedstock.
Claim 3
Dependent Claim
25 words
A method as defined by claim 1 further comprising adding viscosity increasing agent to the surfactant solution to further increase the viscosity of the solution.
Claim 4
Dependent Claim
15 words
A method as defined by claim 1 wherein the surfactant solution exhibits non-Newtonian fluid behavior.
Claim 5
Dependent Claim
16 words
A method as defined by claim 5 wherein the non-Newtonian fluid behavior is pseudo-plastic and thixotropic.