Berol Kemi Ab

Tendex Kjemi Service A/s

Eva M Sterberg

Krister A Holmberg

Eva M Andreasson

Finn Egeli

Borje Nystrom

Kjell G Stridh

Novel ether phosphonate surfactants having a branched hydrophobic tail are used in a process for enhanced oil recovery from a subterranean oil reservoir. They combine a high oil-mobilizing capacity with a good tolerance against divalent ions. The ether phosphonate surfactants are summarized by the formula ##STR1## where R.sub.1 and R.sub.2, being the same or different, are hydrocarbons containing 3-18 carbon atoms each and optionally containing functional groups such as ether and hydroxyl; X is an alkyleneoxy group derived from an alkylene oxide having 2-3 carbon atoms; Y is an alkylene group having 1-4 carbon atoms; R.sub.3 is an alkyl group having 1-4 carbon atoms; M.sup.+ is a monovalent cation; n.sub.1 and n.sub.2, being the same or different, are a number from 0 to 4; m.sub.1 and m.sub.2, being the same or different, are 0 or 1, both m.sub.1 and m.sub.2 not being 0 at the same time and m.sub.1 being 1 when n.sub.1 is a number from 1 to 4 and m.sub.2 always being 1 when n.sub.2 is a number from 1 to 4; and p is a number from 0 to 10.

Ether phosphonate surfactants having branched hydrophobic tails and

Formations surrounding oil wells, gas wells, injection wells and similar bore holes are treated by the injection of a microemulsion containing an acid solution. The main surfactant of the microemulsion is characterized by having at least two hydrocarbon groups attached to a nitrogen atom via a polar groups.

Acidizing method using microemulsion

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Goteborg, Sweden

Eva M Sterberg