Abstract: A method of treating a subterranean formation with a xanthan-viscosified cesium formate brine wherein the pH and/or another characteristic selected from density, xanthan loading, sodium formate loading, potassium formate loading and combinations thereof are modified to delay solid hydrogel formation and maintain pumpability. Also disclosed is a method of delaying onset of solid hydrogel formation, in a gel comprising cesium formate brine viscosified with xanthan polymer, comprises introducing acid into the brine in an amount effective for a pH from 7 to 11, wherein the acid introduction is before, during or after xanthan viscosification and prior to hydrogel formation, wherein the hydrogel formation in the acidified gel occurs at a later time relative to the same gel at a natural pH.

Abstract: A method includes providing a wellbore treatment fluid having a divalent brine and an amount of polymer and lowering a pH value of the treatment fluid. The method further includes retaining the treatment fluid at the lower pH value until the polymer achieves a primary hydration value. The method further includes adding a cross-linking agent and a cross-linking delay agent to the treatment fluid. The cross-linking agent includes zirconium and/or titanium, and the cross-linking delay agent is a polyol. The method further includes performing a wellbore treatment with the treatment fluid.

Abstract: The invention discloses a method of treating a wellbore by providing an aqueous mixture of a hydrated polysaccharide with a salt; adding to the mixture a cross-linking agent for cross-linking the hydrated polysaccharide, wherein the cross-linking agent comprises a zirconium compound, glutamic acid, and a polyol; pumping the aqueous mixture of the hydrated polysaccharide and the cross-linking agent into the wellbore; and cross-linking the hydrated polysaccharide.

Abstract: A method includes providing a wellbore treatment fluid having a divalent brine and an amount of polymer and lowering a pH value of the treatment fluid. The method further includes retaining the treatment fluid at the lower pH value until the polymer achieves a primary hydration value. The method further includes adding a cross-linking agent and a cross-linking delay agent to the treatment fluid. The cross-linking agent includes zirconium and/or titanium, and the cross-linking delay agent is a polyol. The method further includes performing a wellbore treatment with the treatment fluid.

Abstract: A method of treating a subterranean formation penetrated by a wellbore is carried out by providing a treatment fluid comprising a hydratable polymer, a divalent metal salt in an amount of at least about 0.25 mol/L and an aluminum crosslinking agent. The fluid is provided with a pH of from about 5 or higher. The treatment fluid may be caused to contact the formation by introducing the fluid into the wellbore. The fluid may optionally contain a polyol.