changed during the time that drilling and pumping of the drilling fluid takes place a fully hydrated depolymerized polymer suitable for preferred use in the invention may be manufactured by various means known to those skilled in the art for example the polymer may be manufactured by forming a hydratable polymer having a relatively high molecular weight as a result of derivatization of a polysaccharide and then subjecting it to extensive depolymerization whereby the polymer backbone is divided into short chain polymer segments the manufacture of such polymers can be performed by for example rhodia inc of cranberry n j using well known derivatization and depolymerization techniques the hydratable polymer used for forming the short chain segments may be any polysaccharide and is preferably a guar derivative polymer selected from the group consisting of hydroxypropylguar carboxymethylhydroxypropylguar carboxymethylguar hydroxyethyl cellulose carboxymethyl cellulose carboxymethylhydroxyethyl cellulose and the like of these depolymerized hydroxypropylguar is preferred polyacrylamides and or polyacrylonitriles may also be used instead of or in addition to polysaccharides the depolymerized polymer should have an average molecular weight in the range of from about 25 000 to about 400 000 and preferably has an average molecular weight in the range of from about 50 000 to about 250 000 if desired for purposes of transportation storage or otherwise the depolymerized polymer may be stored in dry form and when.