Injection fluids comprising anionic surfactants and alkoxylated alcohols and the use of such fluids in chemical enhanced oil recovery processes
A method for using a surfactant formulation in chemical enhanced oil recovery, wherein said surfactant formulation comprises at least: (i) an anionic salt of an alkyl alkoxylated sulfate, wherein said alkyl alkoxylated sulfate has a molecular structure as shown in (I), wherein R is a linear, branched or mixture of linear and branched alkyl group having from 10 to 20 carbon atoms, n=4 −15, m=0-10, M+ is an alkali metal ion, an alkanolamine ion, an alkyl amine ion or an ammonium ion; and (ii) a non-ionic alcohol O ethoxylate, wherein said alcohol ethoxylate has a molecular structure as shown in (II), wherein R 1 is a linear, branched or mixture of linear and branched alkyl group having from 8 to 24 carbon atoms, y=20-100.
1. A surfactant formulation for use in chemical enhanced oil recovery, wherein said surfactant formulation comprises at least:
i) an anionic salt of an alkyl alkoxylated sulfate, wherein said alkyl alkoxylated sulfate has a molecular structure as shown in [I]:
wherein
R is a linear, branched or mixture of linear and branched alkyl group having from 10 to 20 carbon atoms,
n=4-15,
m=0-10,
M + is an alkali metal ion, an alkanolamine ion, an alkyl amine ion or an ammonium ion; and
ii) a non-ionic alcohol ethoxylate, wherein said alcohol ethoxylate has a molecular structure as shown in [II]:
wherein
R1 is a linear, branched or mixture of linear and branched alkyl group having from 8 to 24 carbon atoms,
y=20-100.
2. The surfactant formulation of claim 1 , wherein R is a branched alkyl group.
3. The surfactant formulation of claim 2 , wherein R is a 2-alkyl branched group.
4. The surfactant formulation of claim 1 , wherein m=0.
5. The surfactant formulation of claim 1 , wherein R has from 12 to 16 carbon atoms.
6. The surfactant formulation of claim 1 , wherein R 1 =C 12 -C 24 .
7. The surfactant formulation of claim 1 , wherein 40≤y 100.
8. The surfactant formulation of claim 1 wherein the weight ratio of i)/ii) is from 6:1 to 1:6.
9. The surfactant formulation of claim 1 wherein the combined concentration of i) and ii) does not exceed 0.5 weight % of the total formulation.
10. The surfactant formulation of claim 1 wherein said surfactant formulation lowers the interfacial tension of crude oil to ultralow values of at or below 10 −1 mN/m.
11. The surfactant formulation of claim 1 above wherein said surfactant formulation is able to lower interfacial tension values of crude oil in brines with salinities from 4% up to 15% total dissolved solids.
12. A method for chemical enhanced oil recovery from a subterranean formation that is penetrated by at least one injection well and one production well, comprising:
i) injecting into an injection well a surfactant formulation such that said surfactant formulation contacts crude oil present in said subterranean formation to lower the interfacial tension of said crude oil to ultralow values at or below 10 −2 mN/m, said surfactant formulation being able to lower interfacial tension values in temperatures from 25° C. up to 70° C. and in brines with from 4% up to 15% total dissolved solids, at least a portion of said dissolved solids being divalent cations, said surfactant formulation comprising at least
a) an anionic salt of an alkyl alkoxylated sulfate, wherein said alkyl alkoxylated sulfate has a molecular structure as shown in [I]:
wherein
R is a linear, branched or mixture of linear and branched alkyl group having from 10 to 20 carbon atoms,
n=4-15,
m=0-10,
M + is an alkali metal ion, an alkanolamine ion, an alkyl amine ion or an ammonium ion; and
b) a non-ionic alcohol ethoxylate, wherein said alcohol ethoxylate has a molecular structure as shown in [II]:
wherein
R1 is a linear, branched or mixture of linear and branched alkyl group having from 8 to 24 carbon atoms,
y=20-100,
recovering oil from the subterranean formation from a production well.
13. The method of claim 12 , wherein R is a branched alkyl group.
14. The method of claim 12 , wherein R is a 2-alkyl branched group.
15. The method of claim 12 , wherein m=0.
16. The method of claim 12 , wherein R has from 12 to 16 carbon atoms.
17. The method of claim 12 , wherein R 1 =C 12 -C 24 .
18. The method of claim 12 , wherein 40<y≤100.
19. The method of claim 12 , wherein the weight ratio of i)/ii) is from 6:1 to 1:6.
20. The method of claim 12 , wherein the combined concentration of i) and ii) does not exceed 0.5 weight % of the total formulation.
21. The method of claim 12 , wherein said surfactant formulation lowers the interfacial tension of crude oil to ultralow values of at or below 10 −1 mN/m.
22. The method of claim 12 , wherein said surfactant formulation is able to lower interfacial tension values of crude oil in brines with salinities from 4% up to 15% total dissolved solids.