High temperature stable viscosifier and fluid loss control system

Claim 1

A composition capable of imparting to clay-free aqueous systems a combination of pseudoplasticity and fluid loss control comprising a mixture of: (a) a hydroxy containing aluminum component formed by mixing in an aqueous medium and under a high degree of agitation a water-soluble basic agent selected from the group consisting of an alkali metal aluminate, alkali metal hydroxide, ammonium hydroxide and mixtures thereof with a water-soluble acidic agent selected from an inorganic acid, aluminum chloride, aluminum sulfate, aluminum nitrate, their hydrates and mixtures thereof; at least one of said basic and acidic agents being an aluminum containing compound: said acidic and basic agents being reacted in a ratio such that the resultant product is capable of imparting to an aqueous medium a pH of at least about 8; in combination with (b) a chemical compound capable of converting to a higher oxidation state under alkaline conditions selected from the group consisting of C 1 -C 5 alkanols, unsubstituted or C 1 -C 3 alkyl, aryl or alkaryl substituted phenols, hydroquinone, C 1 -C 15 alkanothiol, alkali metal, alkaline earth metal or ammonium salt of sulfite, bisulfite or nitrite, ferrous metal salts of chloride or sulfate and cuprous metal salts of chloride and sulfate; in combination with (c) a reaction product formed between a polymeric material having a weight average molecular weight of at least about 20,000 selected from the group consisting of polyvinyl alcohol and hydroxy C 1 -C 3 alkyl cellulose and at least from about 1 to 200 percent of stoichiometry of a cross-linking agent selected from the group consisting of a compound containing at least one aldehyde group therein or a compound capable of generating in situ at least one aldehyde or an epihalohydrin; the reaction between said polymeric material and said aldehyde carried out in an aqueous acidic medium having a pH of 5.5 or less and the reaction between said polymer and said epihalohydrin being carried out in an aqueous basic medium having a pH of at least about 9.5; wherein the weight ratio of component (a) to (c) is at least from about 0.75:1 to 3:1 and of component (b) to (c) is at least from about 0.2:1 to 1:1.