Abstract: The present invention relates to a well fluid for releasing tubular elements stuck in the well. The fluid comprises a part A consisting of one or more esters obtained by reaction of a linear or branched monocarboxylic acid (A.1) having between 8 and 24 carbon atoms and a linear or branched polyol (A.2) having between 2 and 20 carbon atoms, a part B consisting of one or more linear or branched monocarboxylic acids having between 8 and 24 carbon atoms, where the carboxylic acid (A.1 and part B) is a mixture of at least 80% carboxylic acids having between 1 and 3 insaturations, and a part C consisting of a different ester or olefins, the quantity of part C is determined in relation to the other components in such a way that the viscosity of the fluid is lower than 40 mPa·s at 40° C. The invention also relates to a method for releasing drillpipes stuck in a well.