Hydraulic fracturing fluids and methods of use with friction reducer slurry formulation
A method of preparing a fracturing fluid for hydraulic fracturing in unconventional reservoirs such as coal beds, sandstones, and shales. The method includes selecting an anionic surfactant, such as an anionic sulphonate surfactant; and contacting the anionic surfactant with a fracturing fluid or with a precursor of said fracturing fluid. The fracturing fluid may further include friction reducing polymers and a booster formulation that provides enhanced polymer performance for increased friction reduction as well as faster polymer dissolution in the fracturing fluid.
1. A method of preparing a fracturing fluid (YY), the method comprising:
(i) selecting a booster formulation comprising an anionic surfactant (AS) and water;
(ii) contacting the booster formulation comprising said anionic surfactant (AS) and water with a fracturing fluid (XX);
wherein the fracturing fluid (XX) incorporates a friction reducer formulation;
wherein said friction reducer formulation comprises a water-soluble polymer (B) in combination with an oil phase, wherein polymer (B) is dispersed in said oil phase and comprises 0.1 to 100 μm particles of said polymer (B):
wherein said friction reducer formulation further comprises a slurry and said slurry comprises a polymer (C) wherein particles of polymer (C) are dispersed in said oil phase as solid discrete particles and said particles have a mean particle diameter of at least 100 μm and less than 1000 μm, wherein said polymer (C) includes an acrylamide repeat unit; and
wherein said anionic surfactant (AS) is an anionic sulphonate surfactant.
2. The method according to claim 1 , wherein said friction reducer formulation comprises a combination of an emulsion and a powder slurried in a fluid.
3. The method according to claim 1 , wherein said water-soluble polymer (B) includes optionally-substituted acrylamide repeat units and, optionally, acrylate repeat units.
4. The method according to claim 1 , wherein said polymer (B) includes an optionally-substituted acrylamide repeat unit; and acrylate and/or 2-acrylamido-2-methylpropane sulfonate (AMPS)-based repeat units.
5. The method according to claim 1 , wherein said anionic surfactant (AS) includes a moiety of formula:
Z 1 —O—Z 2
wherein Z 1 and Z 2 are, independently, optionally-substituted alkyl or aryl.
6. The method according to claim 5 , wherein groups Z 1 and Z 2 include at least at least 3 carbon atoms; and/or the sum of the number of carbon atoms in groups Z 1 and Z 2 is in the range 2-100, and/or at least one of Z 1 and Z 2 includes a C4 to C15 linear or branched alkyl group.
7. The method according to claim 5 , wherein only one of Z 1 and Z 2 includes an alkyl group.
8. The method according to claim 5 , wherein 85 to 100% of molecules of said surfactant are disulphonated.
9. The method according to claim 5 , wherein said moiety of formula Z 1 —O—Z 2 is of general formula
wherein at least one of the phenyl groups is sulphonated and R 40 is a C4 to C15 linear or branched alkyl group which is unsubstituted.
10. The method according to claim 1 , further comprising contacting said fracturing fluid (XX) or a precursor of said fracturing fluid (XX) with a second anionic surfactant.
11. The method according to claim 10 , wherein said the second anionic surfactant comprises alkyl benzene sulphonate of general formula:
where R 42 CHR 43 is a linear or branched alkyl group; M is H, Na or an ammonium moiety derived from neutralizing said alkyl benzene sulfonic acid with an alkanolamine.
12. The method according to claim 10 , wherein the anionic surfactant (AS) is provided as part of a booster formulation, wherein said booster formulation comprises 1 to 50 wt % of the anionic surfactant (AS) and 1 to 25 wt % of the second anionic surfactant.
13. The method according to claim 12 , wherein said booster formulation comprises from 5 to 20 wt % of anionic surfactant (AS) and from 5-10 wt % of the second anionic surfactant; and/or the ratio of the wt % of said anionic surfactant (AS) divided by the wt % of said the second anionic surfactant within said booster formulation is in the range 0.9 to 2.5.
14. The method according to claim 1 , wherein polymer (C) is poly(ethylene oxide) or includes a repeat unit which includes an acrylamide.
15. The method according to claim 1 , wherein said friction reducer formulation comprises an inverse emulsion and/or a dewatered emulsion, wherein said friction reducer formulation comprises a fluid (D) comprising the oil phase and polymer (B) dispersed in said oil phase to define said emulsion.
16. The method according to claim 15 , wherein said fluid (D) is an emulsion which includes 15-40 wt % of said oil phase, 15-40 wt % of polymer (B) and 15-40 wt % of water.
17. The method according to claim 1 , further comprising making a fracturing fluid which includes 25 to 5,000 ppm of fracturing fluid (XX) in an aqueous liquid.
18. The method according to claim 1 , wherein, at some stage in the method, one or a plurality of proppants is contacted with fracturing fluid (XX).
19. The method according to claim 1 , wherein, at some stage in the method, said fracturing fluid (XX) or fracturing fluid (YY) includes 2.9 to 54 wt % of proppants.
20. A method of fracturing a subterranean formation, the method comprising contacting the formation with a fracturing fluid (YY) made in a method of claim 1 .
21. An assembly positioned adjacent a subterranean formation and arranged to deliver a fracturing fluid (YY) as described in claim 1 into the subterranean formation, said assembly comprising:
(I) a receptacle containing a friction reducer formulation;
(II) a receptacle containing a booster formulation comprising an anionic surfactant (AS) and water;
(III) an aqueous liquid;
(IV) a pump (PI) for dosing said friction reducer formulation from said receptacle containing said friction reducer formulation to define at least part of the fracturing fluid (YY);
(V) a pump (P2) for dosing said booster formulation from said receptacle containing said booster formulation to define at least part of a fracturing fluid (YY);
(VI) a conduit for delivering fracturing fluid (YY) into the formation; and
(VII) a pump (P3) for injecting the fracturing fluid (YY) via said conduit into the formation.
22. The assembly according to claim 21 , wherein said booster formulation comprises 40 to 70 wt % water.
23. The method according to claim 1 , wherein said booster formulation comprises 40 to 70 wt % water.