Patent ID: 7247604

Claim:
A method for well drilling, completion or workover operation, comprising circulating an oil-based well fluid that is temperature-stable and particularly suitable for high pressure/high temperature drilling, comprising an aqueous phase dispersed in a non-miscible continuous phase, and comprising a liquid emulsification system comprising: a) at least one superamide having at least 90% by weight of at least one compound of the following formulae: [R 1 —CON(R 2 )—CH 2 CHR 3 —O] p X (I) where R 1 represents a linear or branched, saturated or unsaturated C 7 -C 30 hydrocarbon radical, optionally carrying at least one hydroxyl group; R 2 represents a hydrogen atom; R 3 represents a hydrogen atom or a C 1 -C 4 hydrocarbon radical; X represents a hydrogen atom, a C 1 -C 6 hydrocarbon radical, a phosphate, carboxylate, sulphate or sulphonate group; p is 1 or 2 depending on the nature of X; (b) and at least one co-surfactant selected from the group consisting of fatty acids, dicarboxylic acids and carboxylates, wherein co-surfactant b) represents from 40 to 90% by weight of the liquid emulsification system.