Styrenic block copolymers as thermally-activated viscosifiers for oilfield applications
View Patent ↗Provided herein is a dispersion composition comprising a blend of a semi-crystalline, selectively hydrogenated block copolymer and a low polarity fluid for oilfield applications. The block copolymer comprises blocks of semi-crystalline hydrogenated polybutadiene, blocks of poly(mono alkenyl arenes), and blocks of hydrogenated, non-crystalline conjugated dienes. The dispersions can be converted to thixotropic fluids or cohesive gels and find application as insulating packer fluids, fluid loss pills, drilling fluids and completion fluids.
1. A dispersion composition for oilfield applications, the composition comprising a blend of:
a selectively hydrogenated block copolymer having the general formula C-A-B or C-A-B-A-C or (C-A-B) n X wherein
C is a semi-crystalline hydrogenated block of butadiene having a vinyl content of 15 mol % or less before hydrogenation and a molecular weight of 7,500 to 15,000 grams per mole,
A is a mono-alkenyl arene block having a molecular weight of 30,000 to 100,000 grams per mole,
B is a non-crystalline, hydrogenated polymer block comprising conjugated diene and having a molecular weight of at least 70,000 grams per mole,
n ranges from 1.5 to 6.0, and
X is the residue of a coupling agent, and
a low polarity fluid,
wherein said blend is a low viscosity fluid dispersion having a viscosity of no greater than 500 cP at 70° F.
2. The dispersion composition of claim 1 wherein the mono-alkenyl arene is styrene.
3. The dispersion composition of claim 1 wherein the conjugated diene of the B block is butadiene or isoprene or a mixture thereof.
4. The dispersion composition of claim 3 wherein the conjugated diene is butadiene and the vinyl content is greater than 25 mol %.
5. The dispersion composition of claim 1 wherein the low polarity fluid is selected from the group consisting of mineral oils, alkyl substituted paraffin fluids, internal olefin fluids, or mixtures thereof.
6. The dispersion composition of claim 1 wherein the semi-crystalline, selectively hydrogenated block copolymer has the general formula C-A-B.
7. The dispersion composition of claim 1 wherein the semi-crystalline, selectively hydrogenated block copolymer has the general formula C-A-B-A-C or (C-A-B) n X.
8. The dispersion composition of claim 1 wherein the C block of the semi-crystalline, selectively hydrogenated block copolymer has a vinyl content of 10 mol % or less.
9. The dispersion composition of claim 1 wherein said blend comprises from 4 to 10 wt. % of the selectively hydrogenated block copolymer and 90 to 96 wt. % of the low polarity fluid.
10. The dispersion composition of claim 1 wherein the selectively hydrogenated block copolymer comprises up to 50 wt. % of a diblock copolymer having the general formula A-B wherein A is a mono-alkenyl arene block and B is a hydrogenated conjugated diene block.
11. A cohesive gel for oilfield applications, the cohesive gel comprising:
a semi-crystalline, selectively hydrogenated block copolymer having the general formula C-A-B-A-C or (C-A-B) n X wherein C is a semi-crystalline, hydrogenated block of butadiene having a vinyl content of 15 mol % or less before hydrogenation and a molecular weight of 7,500 to 15,000 grams per mole, A is a mono-alkenyl arene block having a molecular weight of 30,000 to 100,000 grams per mole, B is a non-crystalline, hydrogenated polymer block comprising conjugated diene and having a molecular weight of at least 70,000 grams per mole, n ranges from 1.5 to 6.0, and X is the residue of a coupling agent, and
a low polarity fluid
wherein the semi-crystalline, selectively hydrogenated block copolymer is dissolved in the low polarity fluid.
12. The cohesive gel of claim 11 wherein the mono-alkenyl arene is styrene.
13. The cohesive gel of claim 11 wherein the conjugated diene is butadiene or isoprene or a mixture thereof.
14. The cohesive gel of claim 13 wherein the conjugated diene is butadiene and the vinyl content is greater than 25 mol %.
15. The cohesive gel of claim 11 wherein the low polarity fluid is selected from the group consisting of mineral oils, alkyl substituted paraffin fluids, internal olefin fluids, or mixtures thereof.
16. The cohesive gel of claim 11 wherein the C block of the semi-crystalline, selectively hydrogenated block copolymer has a vinyl content of 10 mol % or less.
17. The cohesive gel of claim 11 wherein said blend comprises from 4 to 10 wt. % of the semi-crystalline, selectively hydrogenated block copolymer and 90 to 96 wt. % of the low polarity fluid.
18. A thixotropic fluid for oilfield applications, the thixotropic fluid comprising:
a semi-crystalline, selectively hydrogenated block copolymer having the general formula C-A-B wherein C is a semi-crystalline, selectively hydrogenated block of butadiene having a vinyl content of 15 mol % or less before hydrogenation and a molecular weight of 7,500 to 15,000 grams per mole, A is a monoalkenyl arene block having a molecular weight of 30,000 to 100,000 grams per mole, B is a non-crystalline, hydrogenated polymer block comprising conjugated diene and having a molecular weight of at least 70,000 grams per mole, and
a low polarity fluid
wherein the semi-crystalline, selectively hydrogenated block copolymer is dissolved in the low polarity fluid.
19. The thixotropic fluid of claim 18 wherein the mono-alkenyl arene is styrene.
20. The thixotropic fluid of claim 18 wherein the conjugated diene is butadiene or isoprene or a mixture thereof.
21. The thixotropic fluid of claim 20 wherein the conjugated diene is butadiene and the vinyl content is greater than 25 mol %.
22. The thixotropic fluid of claim 18 wherein the low polarity fluid is selected from the group consisting of mineral oils, alkyl substituted paraffin fluids, internal olefin fluids, or mixtures thereof.
23. The thixotropic fluid of claim 18 wherein the C block of the semi-crystalline, selectively hydrogenated block copolymer has a vinyl content of 10 mol % or less.
24. The thixotropic fluid of claim 18 wherein the B block of the semi-crystalline, selectively hydrogenated block copolymer has a vinyl content of at least 30 mol %.
25. The thixotropic fluid of claim 18 wherein said blend comprises from 4 to 10 wt. % of the semi-crystalline, selectively hydrogenated block copolymer and 90 to 96 wt. % of the low polarity fluid.
26. A process for forming a cohesive gel comprising heating the dispersion composition of claim 7 to a temperature of at least 150° F.
27. A process for forming a thixotropic fluid comprising heating the dispersion composition of claim 6 to a temperature of at least 150° F.