Method of treating subterranean formations using a non-damaging fracturing fluid

Claim 1

A process for fracturing a subterranean formation wherein an aqueous fracturing fluid is injected through a well and into the formation at a pressure and rate sufficient to form a fracture therein, the improvement wherein the aqueous fracturing fluid includes (a) an effective amount of a copolymer of acrylamide and potassium acrylate crosslinked with a titanium or zirconium compound, the acrylamide comprises from 60 to 78 mole % of the copolymer and the potassium acrylate comprises 22 to 40 mole % of the copolymer and the concentration of the crosslinked copolymer being sufficient to provide the aqueous fracturing fluid with a viscosity of between 20 cp and 1,000 cp at 170 sec - at a temperature of at least 200° F.; and (b) an effective amount of an oxidative gel breaker capable of degrading the copolymer after about 2 hours.

Claim 8

A method of fracturing a subterranean formation penetrated by a borehole which comprises (a) injecting into the formation an aqueous fracturing fluid containing from 0.05 to 1.00 wt % of a copolymer of between about 22 and about 40 mole % of acrylamide, and 22 to 40 mole % of potassium acrylate crosslinked with an effective amount of a crosslinker selected from the group consisting of titanium compounds and zirconium compounds, and an effective amount of a persulfate breaker to degrade the crosslinked copolymer following the injection step; (b) permitting the crosslinked polymer to degrade; and (c) removing at least a portion of the degraded polymer from the fracture.

Claim 9

A method of fracturing a subterranean formation penetrated by a borehole which comprises (a) injecting into the formation an aqueous fracturing fluid containing from 0.05 to 1.00 wt % of a copolymer of between about 22 and about 40 mole % of acrylamide, and 22 to 40 mole % of potassium acrylate crosslinked with an effective amount of a crosslinker selected from the group consisting of titanium compounds and zirconium compounds, and an effective amount of a persulfate breaker to degrade the crosslinked copolymer following the injection step; (b) permitting the crosslinked polymer to degrade; and (c) removing at least a portion of the degraded polymer from the fracture.

Claim 13

A method of fracturing a subterranean formation penetrated by a wellbore which comprises (a) continuously pumping an aqueous fluid down the wellbore and into the formation; (b) adding to the fluid from 0.05 wt % to 1.0 wt % of a copolymer comprising from 60 to 78 mole % of an acrylamide and from 22 to 40 mole % of a potassium acrylate; (c) thereafter adding to the aqueous fluid containing the copolymer (i) an effective amount of a crosslinker selected from the group consisting of zirconium compounds and titanium compounds to provide the fracturing fluid with a viscosity of between 20 cp and 1000 cp at the formation temperature and a shear rate of 170 sec -1 , and (ii) an effective amount of an oxidative breaker to degrade the crosslinked copolymer after about two hours; (d) pumping the viscosified aqueous fluid in the formation to form a fracture therein; (e) permitting the aqueous fluid to set wherein the breaker causes the crosslinked copolymer to degrade; and (f) flowing formation fluids into the wellbore to remove portions of the aqueous fluid.

Claim 14

A method of fracturing a subterranean formation penetrated by a wellbore which comprises (a) continuously pumping an aqueous fluid down the wellbore and into the formation; (b) adding to the fluid from 0.05 wt % to 1.0 wt % of a copolymer comprising from 60 to 78 mole % of an acrylamide and from 22 to 40 mole % of a potassium acrylate; (c) thereafter adding to the aqueous fluid containing the copolymer (i) an effective amount of a crosslinker selected from the group consisting of zirconium compounds and titanium compounds to provide the fracturing fluid with a viscosity of between 20 cp and 1000 cp at the formation temperature and a shear rate of 170 sec -1 , and (ii) an effective amount of an oxidative breaker to degrade the crosslinked copolymer after about two hours; (d) pumping the viscosified aqueous fluid in the formation to form a fracture therein; (e) permitting the aqueous fluid to set wherein the breaker causes the crosslinked copolymer to degrade; and (f) flowing formation fluids into the wellbore to remove portions of the aqueous fluid.