Patent ID: 7670995

Claim:
A method of treating a subterranean formation which comprises at least one hydrocarbon-bearing zone, comprising providing an oligomeric surfactant with a structure comprising from 2 to 8 linked surfactant monomer subunits, each monomer subunit having a formula (R 1 X) p Z m , where X is a carboxylate charged group, R 1 is a C 10 -C 50 organic tail group comprising a C 10 -C 25 straight chain bonded at a terminal atom thereof to X, Z is an alkali metal counterion, and p and m are equal to 1 so that the surfactant monomer subunit is charge neutral, making a viscoelastic treatment fluid which is an aqueous micellar solution containing a thickening amount of said oligomeric surfactant and where micellar aggregation of surfactant makes said solution viscoelastic, wherein the wellbore treatment fluid further comprises at least one of an alkali metal carbonate, an alkali metal hydroxide, EDTA, an alkali metal salt of EDTA and a mineral acid, so that the fluid functions to dissolve scale, and pumping said viscoelastic treatment fluid through a wellbore and into the subterranean formation whereupon contact with hydrocarbons within the formation dissipates the viscosity of said treatment fluid and causes said treatment fluid to selectively invade a hydrocarbon-bearing zone of the formation.