Delayed gelation of polymers
The disclosure is directed to methods and compositions delaying the gelation of polymers in water flooding by sequentially or co-injecting a carboxylate-containing polymer solution, a gel-delaying polymer, and gelation agent into a hydrocarbon reservoir. Delays of weeks are observed.
1. A delayed gelling composition, said composition made by:
a) sequentially combining ingredients comprising:
i) an expandable polymeric particle in an injection fluid, said particle comprising a copolymer of about 80-98 mole percent acrylamide and about 2-20 mole % sodium acrylate;
ii) at least one gel-delaying polymer; and
iii) a crosslinker;
b) thereby forming a delayed gelling composition without forming a separate nanogel.
2. The delayed gelling composition of claim 1 , wherein said gel-delaying polymer has a gelation time of at least 30 days at 85° C. before a non-flowing gel is set.
3. The delayed gelling composition of claim 1 , wherein said crosslinker is a multivalent metal ion selected from chromium, zirconium, iron, aluminum, and titanium.
4. The delayed gelling composition of claim 1 , wherein said crosslinker is polyethylenimine (PEI).
5. The delayed gelling composition of claim 1 , wherein said gel-delaying polymer is made from monomers selected from the group of vinyl, allyl, styrene, and acrylamide monomers and their derivatives, conjugated with a dicarboxylate or a tricarboxylate.
6. The delayed gelling composition of claim 1 , wherein said gel-delaying polymer is polyvinyl alcohol succinate (PVAS), N-hydroxymethyl N-hydroxylmethyl acrylamide (NHMA) succinate, allyl alcohol succinate and allylamine succinate, PVA malate, NHMA malate, allyl alcohol malate or allylamine malate.
7. The delayed gelling composition of claim 1 , wherein said gel-delaying polymer is carboxylated polymer polyaspartate (PAsp), polymalate, polyoxalate, polymalonate, polyglutarate, polyadipate, or polypimelate.
8. The delayed gelling composition of claim 1 , wherein said gel-delaying polymer is PAsp and said crosslinker is Cr(III).
9. A method of increasing the recovery of hydrocarbon fluids in a subterranean formation comprising:
a) injecting the delayed gelling composition of claim 8 into a subterranean formation, wherein said gel-delaying polymer delays the gelation of said expandable polymeric particle by said crosslinker in said subterranean formation;
b) injecting fluid into said subterranean formation to displace said delayed gelling composition deeper into said subterranean formation;
c) waiting for said delayed gelling composition to gel; and then
d) sweeping said reservoir for oil and producing said oil.
10. The delayed gelling composition of claim 1 , wherein said gel-delaying polymer is PVAS and said crosslinker is Cr(III).
11. A method of increasing the recovery of hydrocarbon fluids in a subterranean formation comprising:
a) injecting the delayed gelling composition of claim 10 into a subterranean formation, wherein said gel-delaying polymer delays the gelation of said expandable polymeric particle by said crosslinker in said subterranean formation;
b) injecting fluid into said subterranean formation to displace said delayed gelling composition deeper into said subterranean formation;
c) waiting for said delayed gelling composition to gel; and then
d) sweeping said reservoir for oil and producing said oil.
12. The delayed gelling composition of claim 1 , wherein said expandable polymeric particle, said at least one gel-delaying polymer, and said crosslinker together form a complex.
13. The delayed gelling composition of claim 12 , wherein said complex comprises PVAS or PAsp as the gel-delaying polymer and Cr(III) as the crosslinker.
14. The delayed gelling composition of claim 12 , wherein said expandable polymeric particle comprises a copolymer of about 95 mole percent acrylamide and about 5 mole % sodium acrylate.
15. A method of increasing the recovery of hydrocarbon fluids in a subterranean formation comprising:
a) injecting the delayed gelling composition of claim 14 into a subterranean formation, wherein said gel-delaying polymer delays the gelation of said expandable polymeric particle by said crosslinker in said subterranean formation;
b) injecting fluid into said subterranean formation to displace said delayed gelling composition deeper into said subterranean formation;
c) waiting for said delayed gelling composition to gel; and then
d) sweeping said reservoir for oil and producing said oil.
16. The delayed gelling composition of claim 1 , wherein said expandable polymeric particle comprises a copolymer of about 95 mole percent acrylamide and about 5 mole % sodium acrylate.
17. A method of increasing the recovery of hydrocarbon fluids in a subterranean formation comprising:
a) injecting the delayed gelling composition of claim 16 into a subterranean formation, wherein said gel-delaying polymer delays the gelation of said expandable polymeric particle by said crosslinker in said subterranean formation;
b) injecting fluid into said subterranean formation to displace said delayed gelling composition deeper into said subterranean formation;
c) waiting for said delayed gelling composition to gel; and then
d) sweeping said reservoir for oil and producing said oil.
18. A method of increasing the recovery of hydrocarbon fluids in a subterranean formation comprising:
a) injecting the delayed gelling composition of claim 1 into a subterranean formation, wherein said gel-delaying polymer delays the gelation of said expandable polymeric particle by said crosslinker in said subterranean formation;
b) injecting fluid into said subterranean formation to displace said delayed gelling composition deeper into said subterranean formation;
c) waiting for said delayed gelling composition to gel; and then
d) sweeping said reservoir for oil and producing said oil.