Aqueous fracturing fluid composition and fracturing process using the composition

1. A fracturing fluid comprising, in solution in water, a proppant and an associative amphoteric polymer, said polymer having a molecular weight of at least 1,000,000 g/mol, and comprising units derived from:

0.01 to 10 mol % of at least one cationic monomer containing a hydrophobic chain and of general formula I:

in which:

R1 and R2 are independently selected from hydrogen, CH 3 , CH 2 COOH, COOH, CH 2 COOR 7 COOR 7 , CH 2 CONR 7 R 8 , and CONR 7 R 8 ;

R3, R4, and R5 are independently selected from hydrogen, CH 3 , and C 2 H 5 ;

R6 is an alkyl or arylalkyl chain comprising from 8 to 30 carbons;

Q is an alkyl chain comprising from 1 to 8 carbons;

Z is oxygen or NR 7 ;

R7 and R8 are independently selected from hydrogen and an alkyl chain comprising from 1 to 8 carbons;

X is a halide selected from the group consisting of bromide, chloride, iodide, and fluoride, or a counterion of negative charge,

from 0.09 to 89.99 mol % of at least one anionic monomer; and

from 10 to 99 mol % of at least one nonionic water-soluble monomer.

2. The fracturing fluid according to claim 1 , wherein the fluid comprises up to 500 ppm of at least one surfactant.

3. The fracturing fluid according to claim 1 , wherein:

R1 and R2 are independently selected from a hydrogen atom and CH 3 ,

R3 is hydrogen,

R4 and R5 are CH 3 ,

Q is an alkyl chain comprising 2 or 3 carbons; and

Z is oxygen or NH.

4. The fracturing fluid according to claim 1 , wherein the proppant is chosen from the group consisting of sand, ceramic, bauxite, glass beads and resin-impregnated sand.

5. The fracturing fluid according to claim 1 , wherein the proppant represents from 0.5% to 40% of the fluid.

6. The fracturing fluid according to claim 1 , wherein the polymer represents from 0.05% to 2% by weight of the fluid.

7. The fracturing fluid according to claim 1 , wherein the cationic monomer is chosen from the group consisting of N-acrylamidopropyl-N,N-dimethyl-N-dodecylammonium chloride (DMAPA Cl(C12)), N-methacrylamidopropyl-N,Ndimethyl-N-dodecylammonium chloride (DMAPMA Cl(C12)), N-acrylamidopropyl-N,N-dimethyl-N-dodecylammonium bromide (DMAPA Br(C12)), N-methacrylamidopropyl-N,N-dimethyl-N-dodecylammonium bromide (DMAPMA Br(C12)), N-acrylamidopropyl-N,N-dimethyl-N-octadecylammonium chloride (DMAPA Cl(C18)), N-methacrylamidopropyl-N,N-dimethyl-N-octadecylammonium chloride (DMAPMA Cl(C18)), N-acrylamidopropyl-N,N-dimethyl-N-octadecylammonium bromide (DMAPA Br(C18)), N-methacrylamidopropyl-N,N-dimethyl-N-octadecylammonium bromide (DMAPMA Br(C18)), N-ethylhemimaleate, N,N-dimethyl N-decylammonium bromide, N-ethylacrylate, N,N-dimethyl, and N-dodecylammonium bromide.

8. The fracturing fluid according to claim 1 , wherein the anionic monomers are chosen from the group consisting of acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, 2-acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, vinylphosphonic acid, allylsulfonic acid, allylphosphonic acid, and styrenesulfonic acid and the water-soluble alkali metal, alkaline-earth metal and ammonium salts thereof.

9. The fracturing fluid according to claim 1 , wherein the nonionic monomers are chosen from the group consisting of acrylamide and methacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, N-tert-butylacrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyridine and/or N-vinylpyrrolidone, acryloylmorpholine, acryloylpyrrolidone, and alkyl-polyethylene glycol methacrylates.

10. The fracturing fluid according to claim 1 , wherein the polymer comprises:

from 0.05 to 5 mol % of hydrophobic cationic monomer,

from 5 to 54.95 mol % of at least one anionic monomer, and

from 45 to 90 mol % of at least one water-soluble nonionic monomer.

11. The fracturing fluid according to claim 1 , wherein the polymer comprises:

from 0.05 to 2 mol % of hydrophobic cationic monomer,

from 5 to 24.95 mol % of at least one sulfonated anionic monomer

from 0 to 30 mol % of an anionic carboxylate monomer, and

from 45 to 90 mol % of at least one water-soluble nonionic monomer.

12. A process for fracturing an unconventional oil or gas reservoir, wherein:

the fracturing fluid according to claim 1 is prepared, and

the fluid is injected under pressure so as to create fractures distributed perpendicularly to the production well.

13. The process according to claim 12 , wherein at least one oxidizing compound and/or at least one surfactant is then injected into the reservoir.

14. The fracturing fluid according to claim 5 , wherein the proppant represents from 1% to 25% of the fluid.

15. The fracturing fluid according to claim 14 , wherein the proppant represents from 1.5% to 20% by weight of the fluid.

16. The fracturing fluid according to claim 6 , wherein the polymer represents from 0.1% to 1% by weight of the fluid.

17. The fracturing fluid according to claim 16 , wherein the polymer represents from 0.1% to 0.75% by weight of the fluid.

18. The fracturing fluid according to claim 10 , wherein:

the at least one anionic monomer is selected from acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid, and salts thereof; and

the at least one water-soluble nonionic monomer is selected from acrylamide, N-isopropylacrylamide, N—N-dimethylacrylamide, N-tert-butylacrylamide, N-vinylformamide, N-vinylpyrrolidone, acryloylmorpholine, and acryloylpyrrolidone.

19. The fracturing fluid according to claim 11 , wherein:

the at least one sulfonated anionic monomer is 2-acrylamido-2-methylpropanesulfonic acid or a salt thereof,

the anionic carboxylate monomer is acrylic acid or a salt thereof, and

the at least one water-soluble nonionic monomer is acrylamide.

20. The fracturing fluid according to claim 11 , wherein:

R1 and R2 are independently selected from a hydrogen atom and CH 3 ,

R3 is hydrogen,

R4 and R5 are CH 3 ,

Q is an alkyl chain comprising 2 or 3 carbons; and

Z is oxygen or NH.