Treating wells with a temporarily thickening cellulose ether solution

Claim 1

A process for temporarily plugging a subterranean earth formation in or around the borehole of a well, comprising: buffering an aqueous solution to retain a pH of from about 2 to 6 while a selected amount of hydroxyl ions are being added to the solution; dissolving in the aqueous solution a reactive compound that gradually yields enough hydroxyl ions to overcome the buffering and make the solution at least substantially alkaline; dissolving in the aqueous solution a reactive compound that reacts more slowly than the hydroxyl ion-yielding reactant but yields enough hydrogen ions to subsequently make the solution significantly acidic; dispersing in the aqueous solution an unhydrated cellulose ether which hydrates relatively slowly in a significantly acidic aqueous liquid, hydrates relatively rapidly in a substantially alkaline aqueous liquid and, when hydrated, dissolves in an aqueous liquid to form a relatively viscous solution; adjusting the compositions and concentrations of the materials dissolved and dispersed in the aqueous liquid relative to the time-temperature exposure of fluid flowed into contact with the subterranean earth formation and the extent and duration selected for the viscosity of a fluid temporarily plugging the earth formation; and flowing the aqueous liquid into contact with the subterranean earth formation so that the selected extent of viscosity is exhibited for the selected time while the solution is in contact with the subterranean earth formation.