Abstract: An oil base packer fluid for use in completing oil and gas wells comprising:(a) a liquid oleaginous medium;(b) an organophilic clay comprising the reaction product of an organic onium compound and a smectite clay;(c) a polar dispersant for said clay; and(d) a polyfunctional amino silane represented by the formula: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each selected from the group consisting of hydrogen, alkyl, aryl, cycloalkyl, and alkylaryl; and X is selected from the group consisting of alkylene, arylene, alkarylene, arylalkylene, cycloalkylene, aminoalkylene, aminoarylene, aminoalkylarylene, aminoarylalkylene and aminocycloalkylene.The packer fluids are characterized by being thin and pumpable at temperatures up to about 130.degree. F. but are gelled to form an insulating medium at temperatures above about 130.degree. F.

Abstract: A method of insulating a well bore with a pumpable, oil base packer fluid which gels to a thick grease-like consistency at elevated temperatures, the packer fluid comprising a liquid oleaginous phase, an aqueous phase, an oleophilic polymer such as a copolymer of maleic anhydride and a long chain alpha-olefin, a water-in-oil emulsifier and lime.