FIELD: mining.
SUBSTANCE: drilling mud additive ensuring thermal stability contains the mixture of: reaction product of amine and polyfunctional isocyanate and reaction product of carboxylic acid with, at least, two carboxylic fragments; of polyamine, containing two or more functional amine groups; and chemical substance, chosen out of the group, consisted of: alkoxylated alkylamine, amides of fatty acids and their compounds. The invention is developed in dependant claims.
EFFECT: providing the thermal stability of drilling muds.
29 cl, 4 tbl, 3ex
