glycols exhibit good insulating properties when according to the composition of this invention they are used as a solvent for a viscosifier in one preferred composition the glycol is a propylene glycol that can be selected from mono propylene glycol di propylene glycol tri propylene glycol tetra propylene glycol or combinations thereof the one or more viscosifiers can be selected from hydroxy propyl methyl cellulose commercially available as methocell os from the dow chemical co xanthan commercially available as rhodopol 23 from rhodia hydroxy propyl guar commercially available as jaguar 413 from rhodia and combinations thereof when thermal insulation is required under high temperature conditions the glycol can be butylene glycol and one preferred thermal insulating fluid comprises butylene glycol in an aqueous brine because butylene glycol is viscous at lower temperatures additional viscosifiers are not necessary until the butylene glycol thermal insulating fluid is considered for use under higher temperatures conditions above 190 u00b0 f for example butylene glycol can be selected from 1 2 butylene glycol 2 3 butylene glycol 1 3 butylene glycol 1 4 butylene glycol or combinations thereof one preferred embodiment of the thermal insulating fluid comprises a propylene glycol solvent for a viscosifier and a viscosifier the glycol is the solvent and water content of the fluid can range from about 0 1 to about 5 0 alternatively an aqueous brine may be added as a weighting agent in one aspect the preferred thermal insulating fluid comprises a propylene glycol used.