Low residue fluid fracturing system and method of use
A fluid system for hydraulic fracturing operations which comprises a low residue fluid that facilitates the clean up of the wellbore following the treatment is disclosed. The system includes a surfactant compound that forms micelles above a critical concentration. Under certain conditions the addition of an associative thickener compound yields a network based on hydrophobic interactions. The resulting viscous fluid can transport proppants, be applied neat or as a foamed or energized system, or used in an acidizing treatment. The fluid system may further include a breaker additive.
1. A method of fracturing a subterranean formation penetrated by a well bore, comprising the step of formulating a fracturing fluid comprising micelles networked by a polymer comprising at least one hydrophilic group and at least one hydrophobic component, wherein the micelles are formed by an anionic surfactant comprising a compound of formulae I.a to I.f or salts thereof, or mixtures thereof:
in which:
R 1 is selected from linear or branched C 16 -C 22 -alkyl, C 16 -C 22 -alkenyl, C 16 -C 22 -alkynyl, (C 15 -C 21 -alkyl)carbonyl, (C 15 -C 21 -alkenyl)carbonyl and (C 15 -C 21 -alkynyl)carbonyl,
Y is a group consisting of from 1 to 20 alkyleneoxy units and
Z is C 1 -C 4 -alkylene, pumping the fracturing fluid down the wellbore at a rate and pressure sufficient to initiate or extend a fracture in the formation and breaking the viscosity by adding a breaker, wherein the breaker is an alkaline material, an alkaline material precursor, or a non-ionic breaking surfactant.
2. The method of claim 1 wherein the fluid further comprises a non-ionic surfactant.
3. The method of claim 1 wherein the fluid further comprises a co-surfactant.
4. The method of claim 1 wherein the fluid has a pH less than about 5.
5. The method of claim 4 wherein the fluid has pH of about 4.3 to about 4.5.
6. The method of claim 1 wherein the fluid has a storage modulus (G′) lower than the loss modulus (G″) when measured at frequencies below 10 rad/sec.
7. The method of claim 1 wherein the polymer is added at a concentration less than the overlap concentration of the polymer.
8. The method of claim 1 wherein the fluid is foamed or energized.
9. The method of claim 1 wherein the fluid further comprises suspended proppants.
10. The method of claim 1 wherein the breaker comprises light burnt magnesium oxide or hard burnt magnesium oxide.
11. The method of claim 10 wherein the magnesium oxide is suspended in mineral oil.
12. The method of claim 11 further comprising a retarding agent.
13. The method of claim 12 wherein the retarding agent comprises a fatty acid, a fatty alcohols, or an alkaline sulfonate salt.
14. The method of claim 1 wherein the breaker is the non-ionic breaking surfactant.
15. The method of claim 14 wherein the non-ionic breaking surfactant comprises a non-ionic surfactant based on alkylpolyethylene glycol ethers, wherein the alkyl chain comprises a linear, saturated fatty alcohol with a chain length of C 12 to C 25 .
16. The method of claim 15 wherein the degree of ethoxylation varies between 10 and 80.
17. The method of claim 14 wherein non-ionic the breaking surfactant is added in solid form, solution, emulsion, encapsulated or as a suspension or emulsion of the encapsulated form.
18. The method of claim 1 wherein the anionic surfactant comprises compounds of formulae I.a and I.b.
19. The method of claim 18 wherein the anionic surfactant is comprised of at least about 50% compounds of formula I.a.
20. The method of claim 19 wherein the anionic surfactant is comprised of a mixture of C 16 -C 18 -alkyl-(O—(CH 2 ) 2 ) 4 —OP(═O)(OH) 2 and [(C 16 -C 18 -alkyl-(O—(CH 2 ) 2 ) 4 )—O] 2 —P(═O)(OH).
21. The method of claim 1 wherein the polymer comprises a hydrophilic bridging group and at least two hydrophobic groups.
22. The method of claim 21 wherein each hydrophobic group comprises a linear or branched C 12 -C 22 -alkyl, C 12 -C 22 -alkenyl or 2-hydroxy(C 12 -C 22 -alk-1-yl).
23. The method of claim 21 wherein each hydrophilic bridging group comprises hydrophilic units comprising polyether and/or polyvinyl alcohol.
24. The method of claim 23 wherein the hydrophilic units comprises —[(O—(CH 2 ) 2 ) y1 (O—CH(CH 3 )CH 2 ) y2 ]—in which the sequence of the alkyleneoxy units is as desired and y 1 and y 2 are each independently an integer from 0 to 300, where the sum of y 1 and y 2 is from 10 to 300.
25. The method of claim 24 wherein the hydrophilic units are linked by multivalent gamma bridging units.
26. The method of claim 21 wherein the polymer has a molecular weight of between about 3000 to about 50,000 g/mol.
27. The method of claim 1 wherein the fluid further comprises a non-ionic surfactant.
28. The method of claim 27 wherein the non-ionic surfactant comprises compounds of formula (IV)
R 3 —[(O(CH 2 ) 2 ) z1 (OCH(CH 3 )CH 2 ) z2 ]—OH (IV)
in which:
the sequence of the alkyleneoxy units is as desired,
R 3 is selected from C 12 -C 22 -alkyl, C 12 -C 22 -alkenyl, C 12 -C 22 -alkynyl, (C 11 -C 21 -alkyl)-carbonyl, (C 11 -C 21 -alkenyl)carbonyl and (C 11 -C 21 -alkynyl)carbonyl, and
z 1 and z 2 are each independently an integer from 0 to 20, where the sum of z 1 and z 2 is from 1 to 20.
29. The method of claim 28 in which the R 3 radicals have on average at most one branch.
30. The method of claim 29 in which the R 3 radicals are each independently selected from palmityl, stearyl, oleyl, linoleyl, arachidyl, gadoleyl, behenyl, erucyl, isostearyl, 2-hexydecyl, 2-heptyldecyl, 2-heptylundecyl and 2-octyldodecyl.
31. The method of claim 30 wherein the sum of z 1 and z 2 is from 1 to 10.
32. The method of claim 31 wherein the sum of z 1 and z 2 is from 3 to 9.
33. A method of fracturing a subterranean formation penetrated by a wellbore, comprising the step of formulating a fracturing fluid comprising micelles networked by a polymer comprising at least one hydrophilic group and at least one hydrophobic component, and pumping the fracturing fluid down the wellbore at a rate and pressure sufficient to initiate or extend a fracture in the formation, wherein the micelles are formed by:
a. an anionic surfactant comprising a compound of formulae I.a to I.f or salts thereof, or mixtures thereof:
in which:
R 1 is selected from linear or branched C 16 -C 22 -alkyl, C 16 -C 22 -alkenyl, C 16 -C 22 -alkynyl, (C 15 -C 21 -alkyl)carbonyl, (C 15 -C 21 -alkenyl)carbonyl and (C 15 -C 21 -alkynyl)carbonyl,
Y is a group consisting of from 1 to 20 alkyleneoxy units and
Z is C 1 -C 4 -alkylene, and
b. optionally, a nonionic surfactant,
wherein the total amount of anionic surfactant, nonionic surfactant and polymer forms about 0.1 to about 30% by weight of the fracturing fluid, and the concentration of the polymer is less than the overlap concentration of the polymer and breaking the viscosity by adding a breaker, wherein the breaker is an alkaline material, an alkaline material precursor, or a non-ionic breaking surfactant.
34. The method of claim 33 wherein the pH of the fracturing fluid is adjusted to less than about 5.
35. The method of claim 33 wherein the ratio of surfactant to polymer is between about 1:1 and about 100:1.
36. The method of claim 35 wherein the ratio of surfactant to polymer is about 9:1.
37. The method of claim 33 wherein the fracturing fluid is foamed prior to being pumped downhole.
38. The method of claim 33 wherein the regain permeability of the formation is at least about 50% after treatment with the fracturing fluid.