Crosslinked polymers for use in crude oil recovery
Mobility control polymers can be used to increase recovery of crude oil from a subterranean hydrocarbon-containing formation. A flooding fluid comprising the polymer are injected into a well that is in contact with the subterranean hydrocarbon-containing formation. The polymers are derived from reacting a crosslinking agent with a polymer and the crosslinking agent comprises a polyvalent metal ion having a weight/weight ratio of polymer to crosslinking agent of at least 60:1. These flooding fluids have improved injectivity into the well; the improved injectivity can be measured in terms of the flooding fluid's filter ratio, flow rate, and viscosity.
1. A method for increasing recovery of crude oil from a subterranean hydrocarbon-containing formation, the method comprising injecting an aqueous flooding fluid into a well that is in contact with the subterranean hydrocarbon-containing formation, the aqueous flooding fluid comprising injection water and a mobility control agent, the mobility control agent comprising a crosslinked water-soluble polymer,
wherein the crosslinked water-soluble polymer is derived from reacting a crosslinking agent with a polymer and the crosslinking agent comprises a polyvalent metal ion having a weight/weight ratio of polymer to crosslinking agent of at least 60:1; and
wherein the aqueous flooding fluid improves the mobility of the oil in the formation without blocking the pores of the formation.
2. The method of claim 1 , wherein the weight/weight ratio of polymer to crosslinking agent is from about 70:1 to about 120:1.
3. The method of claim 1 , wherein the weight/weight ratio of polymer to crosslinking agent is from about 90:1 to about 200:1 when the aqueous flooding fluid comprises at least 0.5 weight percent KCl.
4. The method of claim 1 , wherein the pressure differential of the flooding fluid containing the crosslinked water-soluble polymer is not greater than the pressure differential of a flooding fluid containing an otherwise identical water-soluble polymer that is not crosslinked with a polyvalent metal ion.
5. The method of claim 1 , wherein the water-soluble polymer comprises a repeat unit derived from acrylic acid, an acrylic acid salt, a methacrylic acid salt, methacrylic acid, diacetone acrylamide, acrylamide, methacrylamide, a 2-acrylamido-2-methylpropane sulfonate, an acrylamido-t-butyl sulfonate, a styrene sulfonate, 2-(acryloyloxy)-N,N,N-trimethylethanaminium, N,N-dimethylaminoethyl acrylate methyl chloride, N,N-dimethylaminoethyl methacrylate methyl chloride quaternary salt, N,N-dimethylaminopropyl acrylamide methyl chloride, N,N-dimethylaminopropyl methacrylamide methyl chloride, N-vinylformamide, N-vinylpyrrolidinone, diallyldimethyl ammonium chloride, carboxymethylcellulose, vinyl alcohol, or a combination thereof.
6. The method of claim 5 , wherein the water-soluble polymer comprises a repeat unit derived from acrylic acid, an acrylic acid salt, a methacrylic acid salt, methacrylic acid, acrylamide, a 2-acrylamido-2-methylpropane sulfonate, or a combination thereof.
7. The method of claim 6 , wherein the water-soluble polymer comprises a repeat unit derived from acrylic acid, an acrylic acid salt, acrylamide, or a combination thereof.
8. The method of claim 7 , wherein the water-soluble polymer comprises hydrolyzed polyacrylamide.
9. The method of claim 8 , wherein the hydrolyzed polyacrylamide is from about 20 percent hydrolyzed to about 40 percent hydrolyzed.
10. The method of claim 1 , wherein the polyvalent metal ion is a calcium ion, a zinc(II) ion, a chromium(II) ion, a chromium(III) ion, an aluminum ion, or a combination thereof.
11. The method of claim 10 , wherein the crosslinking agent is aluminum acetate, aluminum lactate, aluminum oxalate, aluminum maleate, aluminum succinate, aluminum glutarate, aluminum citrate, aluminum phosphonate, aluminum sulfonate, aluminum carbonate, aluminum chloride, aluminum bromide, or a combination thereof.
12. The method of claim 10 , wherein the crosslinking agent comprises aluminum citrate.
13. The method of claim 1 , wherein the crosslinked water-soluble polymer is produced in the form of an emulsion, a dry powder, a dispersion, or a solution.
14. The method of claim 1 , wherein the weight average molecular weight of the uncrosslinked water-soluble polymer is greater than 1,000,000 Da.
15. The method of claim 13 , wherein the weight average molecular weight of the uncrosslinked water-soluble polymer is from about 10,000,000 Da to about 16,000,000 Da.
16. The method of claim 1 , wherein the aqueous flooding fluid comprising the crosslinked water-soluble polymer has a filter ratio of from 1 to about 1.5 at 900 ppm polymer concentration when the membrane filter size is less than 5.0 microns.
17. The method of claim 16 , wherein the membrane filter size is 1.2 microns.
18. The method of claim 15 , wherein the aqueous flooding fluid comprises about 100 ppm to about 10000 ppm of the crosslinked water-soluble polymer.
19. The method of claim 1 , wherein the aqueous flooding fluid further comprises a surfactant, a biocide, an antioxidant, or a combination thereof.
20. The method of claim 1 , further comprising displacing the hydrocarbon fluid in the formation into one or more production vessels.