Polymer emulsions for use in crude oil recovery
View Patent ↗Emulsions of mobility control polymers can be used to increase recovery of crude oil from a subterranean hydrocarbon-containing formation. A flooding fluid comprising the polymer emulsions are injected into a well that is in contact with the subterranean hydrocarbon-containing formation. The polymers can be temporarily cross-linked and have protected shear degradation and improved injectivity into the well; the shear resistance can be measured in terms of viscosity loss due to shear, and 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 an emulsion of an aqueous phase and an oil phase, the aqueous phase comprising a cross-linked water-soluble polymer and the oil phase comprising a surfactant and an organic solvent or a hydrocarbon oil, wherein after injecting the aqueous flooding fluid into the formation, cross-links break to produce an un-crosslinked water-soluble polymer in the aqueous flooding fluid and the un-crosslinked water-soluble polymer moves throughout the formation without blocking pores of the formation, thereby providing mobility control of the crude oil without blocking pores in the formation;
wherein the water-soluble polymer comprises from about 1 mol% to about 99 mol% acrylamide repeat units and at least one anionic monomer unit derived from a monomer selected from the group consisting of an acrylic acid salt, a methacrylic acid salt, a 2-acrylamido-2-methylpropane suulfonic acid salt and a styrene sulfonic acid salt and wherein the cross-links formed by covalently bonded cross-linking units having the following formula (IIa):
wherein:
each R is independently hydrogen or methyl;
Z is a bond or a C 1 -C 12 alkylenyl group; and
each represents a point of attachment to a first polymer backbone, and each represents a point of attachment to the first polymer backbone or to a second polymer backbone;
wherein after cross-links break in the cross-linked water-soluble polymer, the aqueous flooding fluid comprising the un-crosslinked water-soluble polymer has a filter ratio of from 0.8 to about 1.5 and a flow rate of at least 0.1 g/s when a membrane filter size is 5 microns and the pressure is 20 psi.
2. The method claim 1 , wherein the membrane filter size is 1.2 microns.
3. The method of claim 2 , wherein the aqueous flooding fluid as injected into the well has a filter ratio of from 1 to about 1.2.
4. The method of claim 2 , wherein the aqueous flooding fluid as injected into the well has a filter ratio of from 1 to about 1.1.
5. The method of claim 1 , wherein the surfactant is a high molecular weight, structured multiester of a polyol or high molecular weight, structured multiether of polyol has a molecular weight from about 950 Daltons to about 500,000 Daltons.
6. The method of claim 5 , wherein the high molecular weight, structured multiester of a polyol or high molecular weight, structured multiether of a polyol has a molecular weight from about 950 Daltons to about 50,000 Daltons.
7. The method of claim 1 , wherein the surfactant is a high molecular weight, structured multiester of a polyol comprises a polyoxyalkylene sorbitan di-, tri-, or tetra-oleate, a polyoxyalkylene sorbitan di-, tri-, or tetra-stearate, a sorbitol tri-, tetra-, penta-, or hexa-oleate, a sorbitol tri-, tetra-, penta-, or hexa-stearate, a polyoxyalkylene sorbitol di-, tri-,tetra-, penta, or hexa-oleate, a polyoxyalkylene sorbitol di-, tri-, tetra-, penta-, or hexa-stearate, a copolymer of poly(12-hydroxystearic acid) and polyoxyalkylene, an alkylated polyglycerol, an oxyalkylated polyglycerol, an alkylated polyglycoside, an oxyalkylate polyglycoside, an alkylated polysaccharide, an oxyalkylated polysaccharide, or a combination thereof.
8. The method of claim 1 , wherein one or more of the cross-links between polymer strands are broken by hydrolysis.
9. The method of claim 1 , wherein the surfactant comprises a polyoxyethylene sorbitan trioleate, a copolymer of poly(12-hydroxystearic acid) and poly(ethylene oxide), polyoxyethylene sorbitol hexaoleate, or a combination thereof.
10. The method of claim 1 , wherein the aqueous flooding fluid further comprises a surfactant of sorbitan monooleate, sorbitan dioleate, sorbitan trioleate or combination thereof.
11. The method of claim 1 , wherein an average aqueous droplet size in the emulsion is from about 0.01 micron to about 100 micron.
12. The method of claim 11 , wherein the average aqueous droplet size in the emulsion is less than about 1 micron.
13. The method of claim 1 , wherein the covalently bonded cross-linking units have the following formula (IIb):
14. The method of claim 1 , wherein the viscosity of the aqueous flooding fluid decreases less than 10% upon application of a shear rate from 30,000 s −1 to 100,000 s −1 .
15. The method of claim 14 , wherein the viscosity of the aqueous flooding fluid comprising the un-crosslinked water-soluble polymer decreases less than 5% upon application of a shear rate from 30,000 s −1 to 100,000 s −1 to the aqueous flooding fluid comprising the cross-linked water-soluble polymer as compared to the viscosity of an aqueous flooding fluid comprising the un-crosslinked water-soluble polymer not subjected to the shear rate from 30,000 s −1 to 100,000 s −1 .
16. The method of claim 1 , wherein the aqueous flooding fluid comprises the cross-linked water-soluble polymer and the aqueous flooding fluid is subjected to a shear rate from 30,000 s −1 to 100,000 s −1 .
17. The method of claim 16 , wherein when cross-links break to form the un-crosslinked water-soluble polymer, the viscosity of the aqueous flooding fluid decreases less than 10% upon application of a shear rate from 30,000 s −1 to 100,000 s −1 to the aqueous flooding fluid comprising the cross-linked water-soluble polymer as compared to the viscosity of an aqueous flooding fluid comprising the un-crosslinked water-soluble polymer not subjected to the shear rate from 30,000 s −1 to 100,000 s −1 .
18. The method of claim 16 , wherein when cross-links break to form the un-crosslinked water-soluble polymer, the viscosity of the aqueous flooding fluid decreases less than 1% upon application of a shear rate from 30,000 s −1 to 100,000 s −1 to the aqueous flooding fluid comprising the cross-linked water-soluble polymer as compared to the viscosity of an aqueous flooding fluid comprising the un-crosslinked water-soluble polymer not subjected to the shear rate from 30,000 s −1 to 100,000 s −1 .
19. The method of claim 1 , wherein the water-soluble polymer comprises about 0.1 ppm to about 20,000 ppm hydrolyzable cross-linking units based on the weight of the water-soluble polymer.
20. The method of claim 1 , wherein the water-soluble polymer comprises from about 0.1 ppm to about 500 ppm covalently bonded cross-linking units based on the weight of the water-soluble polymer.