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

• US 5,007,481 A
• Filed: 02/02/1990
• Issued: 04/16/1991
• Est. Priority Date: 02/02/1990
• Status: Expired due to Fees

• Current Assignee: Nalco/Exxon Energy Chemicals L.P. (Exxon Mobil Corporation)
• Original Assignee: Exxon Chemical Patents Inc. (Exxon Mobil Corporation)
• Inventors: Horton, Roger L., Chumley, Robert E., Williams, Dennis A., Newlove, John C.
• Primary Examiner(s): Suchfield, George A.
• Application Number:
  US07/473,863
• Time in Patent Office: 438 Days
• Field of Search: 166/271, 166/300, 166/308, 252/8.551
• US Class Current: 166/300
• CPC Class Codes: C09K 8/685 containing cross-linking agents
• CPC Class Codes: Y10S 507/903 Crosslinked resin or polymer
• CPC Class Codes: Y10S 507/921 Specified breaker component for emulsion or gel
• CPC Class Codes: Y10S 507/922 Fracture fluid

Abstract

Subterranean formations are fractured by use of an aqueous fracturing fluid containing an effective amount of a copolymer of acrylamide and potassium acrylate crosslinked with a titanium or zirconium compounds. The fracturing fluid also contains an oxidative gel breaker. The method is particularly suited for treatment of deep, high temperature formations.

Claims

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.

2. The method of claim 1 wherein the titanium compound is titanium acetyl acetonate and is present in the fracturing fluid at a concentration of between 0.03 to 0.10 wt %, and the zirconium compound is zirconium triethanolamine and is present at a concentration of 400 to 2,000 ppm, said concentrations based on the weight of the fracturing fluid.

3. The method of claim 1 wherein acrylamide comprises from 65 to 75 mole % of the copolymer and the potassium acrylate comprises from 25 to 35 mole % of the copolymer.

4. The method of claim 3 wherein the copolymer has a number average molecular weight of between 500,000 to 20,000,000.

5. The method of claim 1 wherein the copolymer is present in the aqueous fluid in a concentration of between 0.05 to 1.00 wt % and has the following formula ##STR2##

6. The method of claim 1 wherein the formation has a temperature of between 200°

and 400°

F., and said gelled fracturing fluid is stable at the formation temperature prior to breaking by said breaker.

7. 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.

8. The method of claim 7 wherein the fracturing fluid further contains propping agent to prop the fracture open following treatment.

9. The method of claim 8 wherein the crosslinker is a titanium compound.

10. The method of claim 9 wherein the crosslinked copolymer is stable up to temperatures of 400°

F.

11. 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.

12. The method of claim 11 wherein the formation has a temperature of between 200°

F. and 400°

F.