Foam well cleanout using oligomeric sulfonates

In a method of circulating a gas-in-liquid foam in a well the improvement which comprises generating said foam from a gas and a foamable aqueous solution containing as foaming agent the oligomer obtained by the process which comprises heating in the liquid phase a feed comprising at least one compound having a carbon atom content of at least 5 but less than 50 selected from the group of the formula ##EQU4##

• b. RCH(OH)(CH.sub.2).sub.x CHRSO.sub.3 H, and
• c. RCH=CH(CH.sub.2).sub.y CHRSO.sub.3 H
• wherein x is the number 0 and integers 1-3 and y is a whole number in the range 0-n wherein n is a number which is 4 less than the number of carbon atoms in the longest straight chain of the compound containing the --SO.sub.3 H group as a substituent, and wherein the several R groups are the same or different and are hydrogen or alkyl hydrocarbon radicals;
• said heating being at a temperature above about 110.degree.C and below the carbonization temperature of the feed, in the substantial absence of water, and for a period at least sufficient for a significant conversion of the feed to the corresponding oligomeric disulfonic acids, said oligomer being neutralized with ammonia, an alkali metal base, a calcium base, a magnesium base, or a mixture thereof and circulating said foam in said well.