in its rheological properties at high temperatures and permits smooth practice of the fracturing operation application_number US 86962486 A description in accordance with the present invention at least one compound selected from the thiol derivatives of heterocyclic compounds is added to the fracturing fluid containing at least one of guar gum and its derivatives addition of such compounds provides a fracturing fluid having rheological properties much superior to those of the conventional fracturing fluids suitable examples of the thiol derivatives of heterocyclic compounds for use in the method of stabilization of the present invention are 2 thioimidazolidone formula 1 2 mercaptothiazoline formula 2 benzooxazole 2 thiol formula 3 n pyridineoxide 2 thiol formula 4 1 3 4 thiadiazole 2 5 dithiol formula 5 and 4 ketothiazolidine 2 thiol formula 6 str1 in the above formulae x is a hydrogen atom an alkali metal e g na k etc or ammonium in accordance with the present invention at least one stabilizing compound selected from the thiol derivatives of heterocyclic compounds is added to the fracturing fluid the amount of the stabilizing compound added is preferably 0 001 to 0 1 part by weight more preferably 0 005 to 0 05 part by weight per 100 parts by weight of the fracturing fluid if the amount of the stabilizing compound added is less than 0 001 part by weight the stabilization effect is poor on the other hand even if the stabilizing compound is added in an amount in excess of 0 1 part by weight no additional effect can be obtained that is the effect obtained by addition of more than 0 1 part by weight of the stabilizing compound is almost the same as that obtained by addition of 0 1 part by weight of the.