Fluids For Fracking Of Paraffinic Oil Bearing Formations

Abstract

This invention provides a fracturing fluid comprising i) 85 wt.-% or more of an aqueous carrier fluid as continuous phase, ii) 0.001 to 1.5 wt.-% of a first wax inhibitor being dispersed in the carrier fluid, the wax inhibitor being selected from the group consisting of a) copolymers of ethylene and ethylenically unsaturated esters, ethers and/or C.sub.3 to C.sub.30-alkenes, b) homo- or copolymers of ethylenically unsaturated carboxylic acids, bearing C.sub.12-C.sub.50-alkyl radicals bound via ester, amide and/or imide groups, c) ethylene copolymers grafted with ethylenically unsaturated esters and/or ethers, d) homo- and copolymers of C.sub.3 to C.sub.30-olefins, and e) condensation products of alkyl phenols with aldehydes and/or ketones iv) optionally a water soluble polymer for viscosity adjustment,
wherein the amount of water-immiscible hydrocarbons is less than 2.5 wt.-%.

Claims

1. A fracturing fluid comprising i) 85 wt.-% or more of an aqueous carrier fluid as continuous phase, ii) 0.001 to 1.5 wt.-% of a first wax inhibitor being dispersed in the carrier fluid, the wax inhibitor being selected from the group consisting of a) copolymers of ethylene and ethylenically unsaturated esters, ethers and/or C.sub.3 to C.sub.30-alkenes, which contain 4 to 18 mol-% of at least one vinyl ester, acrylic ester, methacrylic ester, alkyl vinyl ether and/or alkene, b) homo- or copolymers of ethylenically unsaturated carboxylic acids, bearing C.sub.12-C.sub.50-alkyl radicals bound via ester, amide and/or imide groups, c) ethylene copolymers grafted with ethylenically unsaturated esters and/or ethers, d) homo- and copolymers of C.sub.3 to C.sub.30-olefins, and e) condensation products of alkyl phenols with aldehydes and/or ketones iv) optionally a water soluble polymer for viscosity adjustment, wherein the amount of water-immiscible hydrocarbons is less than 2.5 wt.-%.

2. The fracturing fluid as claimed in claim 1, further comprising iii) a water insoluble solid proppant.

3. The fracturing fluid as claimed in claim 2, wherein the water insoluble proppant comprises an immobilized second wax inhibitor.

4. The fracturing fluid as claimed in claim 1, in which the first and/or second wax inhibitor comprises a copolymer of ethylene and at least one ethylenically unsaturated ester, ethylenically unsaturated ether or an alkene.

5. The fracturing fluid as claimed in claim 4, in which the ethylenically unsaturated ester is a vinyl ester.

6. The fracturing fluid as claimed in claim 1, in which the first and/or second wax inhibitor comprises a homo- or copolymer of at least one ester of at least one ethylenically unsaturated carboxylic acid, said ester bearing C.sub.12-C.sub.50-alkyl radicals.

7. The fracturing fluid as claimed in claim 6, in which the ethylenically unsaturated carboxylic acid is acrylic acid and/or methacrylic acid.

8. The fracturing fluid as claimed in claim 1, in which the first and/or second wax inhibitor comprises an ethylene copolymer, the ethylene copolymer having side chains being introduced by a grafting reaction of an ethylenically unsaturated ester and/or ether on said copolymer.

9. The fracturing fluid as claimed in claim 6, wherein the ethylenically unsaturated ester independently is an ester of acrylic acid and/or methacrylic acid, said ester bearing C.sub.12-C.sub.50-alkyl radicals.

10. The fracturing fluid as claimed in claim 1, in which the first and/or second wax inhibitor comprises a homo- or copolymer of an ethylenically unsaturated dicarboxylic acid, bearing C.sub.12-C.sub.50-alkyl radicals bound via ester, amide and/or imide groups.

11. The fracturing fluid as claimed in claim 1, in which the first and/or second wax inhibitor comprises a homo- and copolymer of -olefins having 3 to 30 carbon atoms.

12. The fracturing fluid as claimed in claim 1, in which the first and/or second wax inhibitor comprises a condensation product of at least one alkyl substituted phenol and at least one aldehyde or ketone.

13. The fracturing fluid as claimed in claim 3, in which the first wax inhibitor and second wax inhibitor are the same.

14. The fracturing fluid as claimed in claim 3, in which the first wax inhibitor and second wax inhibitor differ in at least one of chemical composition, molecular weight or alkyl chain length.

15. The fracturing fluid as claimed in claim 1, in which the concentration of the first wax inhibitor in the carrier fluid is between 0.005 and 1 wt.-%.

16. The fracturing fluid as claimed in claim 1, in which the first wax inhibitor is present in the carrier fluid in form of a solution or dispersion of the first wax inhibitor in an organic solvent immiscible with water.

17. The fracturing fluid as claimed in claim 16, in which the pour point of the solution or dispersion of the first wax inhibitor in an organic solvent immiscible with water is below the temperature of the formation to be fracked.

18. The fracturing fluid as claimed in claim 1, in which the melting point of the first wax inhibitor is below the temperature of the formation to be fracked.

19. The fracturing fluid as claimed in claim 1, in which the particle size of the dispersed first wax inhibitor is less than 20 m.

20. The fracturing fluid as claimed in claim 3, wherein the water insoluble solid proppant comprising an immobilized second wax inhibitor is a mixture of (i) a water insoluble solid porous proppant functioning as an adsorbent, the cavities of the adsorbent being filled or at least impregnated with the second wax inhibitor, with (ii) a further proppant, the further proppant being different from the adsorbent.

21. The fracturing fluid as claimed in claim 3, wherein the water insoluble solid proppant comprising an immobilized wax inhibitor comprises a proppant selected from the group consisting of sand, ceramics, glass beads, metal beads, bauxite, naturally occurring mineral fiber, crushed walnut hulls and composite particles, coated with a wax inhibitor.

22. The fracturing fluid as claimed in claim 3, wherein the water insoluble solid proppant comprising an immobilized wax inhibitor comprises an adsorbent selected from the group consisting of porous ceramics, finely divided minerals, fibres, ground almond shells, ground walnut shells, ground coconut shells, activated carbon and/or coals, silica particulates, precipitated silica, quartz sand, alumina, silica-alumina, silica gel, mica, silicate, sand, bauxite, kaolin, talc, zirconia, boron, glass microspheres, glass beads, fly ash, zeolites, diatomaceous earth, fuller's earth and organic synthetic high molecular weight water-insoluble adsorbents, clays, bentonite, illite, montmorillonite and synthetic clays and their mixtures, coated and/or impregnated with a wax inhibitor

23. The fracturing fluid as claimed in claim 2, wherein the amount of proppant is between 1 and 20 wt.-% of the fracturing fluid.

24. The fracturing fluid as claimed in claim 1, wherein said fluid comprises, as a further component, 0.001 to 3 wt.-% of a water soluble chemical selected from the group consisting of friction reducer, surfactants, scale inhibitor, biocide, clay stabilizer, salt, pH-adjusting agent, iron control agent, corrosion inhibitor, breaker, and crosslinker.

25. A process for preparing fracturing fluids according to claim 1, wherein the concentration of the dispersed first wax inhibitor is between 0.001 and 1.5 wt.-% of the carrier fluid, by homogenizing constituents i), and optionally iii), iv) and/or v) and then admixing them with a concentrated dispersion having a content of 5 to 70 wt.-% of the first wax inhibitor ii) at a temperature between 10 C. and 60 C.

26. The process as claimed in claim 25 wherein the amount of the dispersion of the first wax inhibitor is between 0.005 and 2 wt.-% of the fracturing fluid.

27. A process for inhibiting wax precipitation during fracturing of a subterranean formation comprising injecting into the well bore a fracturing fluid according to claim 1.

28. (canceled)

Description

EXAMPLES

[0202] A. Methods and Materials Used

[0203] Weight average molecular weights (Mw) of polymers were determined by GPC in THF against poly(styrene standards). The particle sizes and distributions of dispersions were determined by means of a Mastersizer 2000 instrument from Malvern Instruments. Pour points were measured according to ISO 3016. Rheological measurements of crude oil, including viscosity and yield stress were performed on a Thermo Haake Rheostress RS6000 rheometer (Thermo Scientific, Karlsruhe, Germany) using a double gap concentric cylinder measuring geometry CC27 DG Ti or a plate-cone geometry C35/1 CSL. The instrument was equipped with TM-PC Peltier heating/cooling device allowing consistent and accurate temperature ramp profile. Cold finger tests were done using a PSL Systemtechnik (Germany) Cold Finger Model CF15120.

[0204] Dispersions of wax inhibitors were prepared by mixing a solution of the respective polymeric active in xylene or in a higher boiling aromatic solvent (Solvent Naphtha; boiling range 185-220 C.) with anionic surfactant (diethanolammonium salt of carboxylic acids), water and ethylene glycol, according to WO 2008/083724. The dispersions were sheared with an Ultra-Turrax to further reduce the particle size. All dispersions were stable and did not show sediment for at least four weeks.

TABLE-US-00001 TABLE 1 Characterization of wax inhibitors used Dispersion D1 Dispersion of a 40 wt.-% active solution in Solvent Naphtha of an ethylene-vinyl acetate copolymer containing 25 wt.-% vinyl acetate and having a weight average molecular weight (Mw) of 95.000 g/mol. The pour point of the dispersed phase was 42 C. The active (polymer) content of the dispersion was 23 wt.-%; the average particle size was 1.6 m. D2 Dispersion of poly(stearyl acrylate) with a K-value of 30 (measured according to Fikentscher in 5% toluene solution) 50 wt.-% active in xylene. The pour point of the dispersed phase was 18 C. The active (polymer) content of the dispersion was 29 wt.-%; the average particle size was 0.9 m. D3 Dispersion of an ethylene-vinyl acetate copolymer which had been grafted with behenyl acrylate in a weight-ratio of 1:4 60 wt.-% active in xylene. The pour point of the dispersed phase was 24 C. The dispersion had an active (polymer) content of 33 wt.-% and an average particle size of 1.5 m. D4 Dispersion of a copolymer of maleic anhydride and C.sub.20-24--olefin, esterified with behenic acid 50% active in Solvent Naphtha. The pour point of the dispersed phase was 27 C. The dispersion had an active (polymer) content of 30 wt.-% and an average particle size of 1.2 m. D5 Dispersion of a C.sub.30+-alkylphenol-formaldehyde resin (Mw 12.000 g/mol) 40 wt.-% active in Solvent Naphtha. The pour point of the dispersed phase was 9 C. The dispersion had an active (polymer) content of 25 wt.-%; the average particle size was 2.0 m. D6 (comp.) Solution of ethylene-vinyl acetate copolymer (25 wt.-% vinyl acetate, Mw 95.000 g/mol) in aromatic solvent having an active (polymer) content of 23 wt.-%. The pour point was 42 C. D7 (comp.) Aqueous dispersion of polyethylene with weight average molecular weight of 100.000 g/mol and a degree of branching of 30 CH.sub.3/1000 CH.sub.2 groups. The melting temperature of the polyethylene was 103 C. The dispersion had an active (polymer) content of 50 wt.-%; the average particle size was 0.3 m.

[0205] B. Stability of Wax Inhibitor Dispersions in Carrier Fluid

[0206] The dispersions characterized in table 1 were added to a typical carrier fluid with stirring for 10 min. The carrier fluid contained 3% KCl in city tap water, 0.001% phosphonate scale inhibitor (diethylenetriaminepenta (methylenephosphonic) acid (DTPMP)), 0.01% nonionic surfactant (alkoxilated lauric alcohol), and 0.005% anionic polyacrylamide friction reducer. The samples were visually graded after standing at room temperature respectively at 75 C. for 2, 4 and 8 hours. The rating given in table 2 was made according to the following grading:

[0207] 1=stable (homogeneously turbid, no separation)

[0208] 2=not stable (waxy or oily precipitate on surface and/or glassware)

TABLE-US-00002 TABLE 2 Stability of the dispersion of wax inhibitor in carrier fluid content stability at room temperature stability at 75 C. example wax inhibitor (wt.-%) 2 hours 4 hours 8 hours 2 hours 4 hours 8 hours 1 D1 0.05 1 1 1 1 1 1 2 D2 0.10 1 1 1 1 1 1 3 D3 0.05 1 1 1 1 1 1 4 D3 0.50 1 1 1 1 1 1 5 D3 0.10 1 1 1 1 1 1 6 D4 0.25 1 1 1 1 1 1 7 D5 0.10 1 1 1 1 1 1 8 D1 + D4 0.1 + 0.1 1 1 1 1 1 1 9 (comp.) D6 0.1 2 2 2 2 2 2 10 (comp.) D7 0.1 1 1 1 1 1 1

[0209] C. Impact of Wax Inhibitors Dispersed in Carrier Fluids on Crude Oil Viscosity

[0210] These examples are to demonstrate the efficacy of wax inhibitors dispersed in carrier fluid on reduction of viscosity of a waxy crude oil under cooling conditions above the pour point of the oil. To mimic downhole conditions for a crude oil-carrier fluid system a sample containing equal amounts of crude oil and carrier fluid containing dispersed wax inhibitor was charged into a Teflon-line pressurized autoclave. The untreated crude oil had a pour point of 24 C., the carrier fluid used was the brine as depicted in examples 1 to 9.

[0211] The autoclave was pressurized with nitrogen gas to 1000 psi and was allowed to incubate for 24 hours under static condition (no mixing) at 75 C. in order to mimic downhole conditions. Subsequently viscosity was analysed using steady shear viscosity measurement upon a cooling program at shear rate of 10 s1.

TABLE-US-00003 TABLE 3 Viscosity of crude oil after oil-brine incubation for 24 hours. Viscosity (cP) example wax inhibitor 20 C. 10 C. 0 C. 10 C. 20 C. 11 (comp.) none 3200 1017 229 24 13 12 0.01 wt.-% D1 390 148 61 22 12 13 0.02 wt.-% D1 378 136 58 22 11 14 0.02 wt.-% D2 403 145 56 23 11 15 0.01 wt.-% D3 360 130 54 23 12 16 0.02 wt.-% D3 368 138 53 22 12 17 0.03 wt.-% D3 364 135 55 23 12 18 0.04 wt.-% D3 371 140 53 23 12 19 0.05 wt.-% D3 382 137 55 23 12 20 0.02 wt.-% D4 379 142 56 22 11 21 0.10 wt.-% D4 358 131 51 21 10 22 0.05 wt.-% D5 410 154 64 22 12 23 (comp.) 0.10 wt.-% D7 2800 905 204 24 13

[0212] Examples 10 to 21 show that the addition of even 0.01 wt.-% of dispersed wax inhibitor to the aqueous carrier phase significantly reduces the viscosity of crude oil above its pour point. On the contrary, the addition of polyethylene (D7) does not give a comparable result. Supposedly the dissolution rate is too slow.

[0213] D. Impact of Wax Inhibitors Dispersed in Carrier Fluid on Crude Yield Stress

[0214] These examples are designed to show the effect of a wax inhibitor dispersed in aqueous carrier fluid on the yield stress of crude oil under downhole conditions. In analogy to the experimental setup of examples 10 to 21 a sample of crude oil with a pour point of 12 C. (untreated) was incubated with an equal amount of carrier fluid containing dispersed wax inhibitor at 1000 psi pressure of nitrogen gas for 24 hours under static condition (no mixing) at 75 C. Subsequently the crude was analysed for yield stress. Yield stress measurements were done using a shear stress ramp of 5 Pa/min from 0.1 to 50 Pa when sample was cooled at constant cooling rate of 1 C./min and incubated at 10 C. for 10 minutes.

TABLE-US-00004 TABLE 4 Crude oil yield stress data after oil and brine incubated for 24 hours. example Wax inhibitor Yield Stress (Pa) 24 (comp.) 0 >50 25 0.02 wt.-% D1 4.3 26 0.02 wt.-% D2 2.9 27 0.01 wt.-% D3 2.3 28 0.02 wt.-% D3 1.4 29 0.03 wt.-% D3 1.4 30 0.04 wt.-% D3 1.3 31 0.05 wt.-% D3 1.2 32 0.01 wt.-% D4 2.5 33 0.05 wt.-% D4 1.5 34 0.02 wt.-% D3 + 0.02 wt.-% D4 1.1 35 0.02 wt.-% D5 1.8 36 0.10 wt.-% D5 1.3 37 (comp.) 0.02 wt.-% D7 44 38 (comp.) 0.10 wt.-% D7 31

[0215] Examples 22-34 show the efficacy of a wax inhibitor dispersed in the carrier fluid on reducing the yield stress of a waxy crude under an extreme cooling condition but still far above the pour point of the crude. It was found that addition of even 0.01 wt.-% of wax inhibitor according to the invention dispersed in the carrier fluid significantly reduces the yield stress of crude from more than 50 Pa to only 2.3 Pa.

[0216] E. Impact of Wax Inhibitors Dispersed in Carrier Fluid on Wax Deposition from Crude Oil

[0217] These examples are designed to show the effect of a wax inhibitor dispersed in aqueous carrier fluid on the wax deposition from crude oil under downhole conditions using the industry widely practiced cold finger test method. In analogy to the experimental setup of examples 10 to 21 a sample of crude oil with a pour point of 6 C. (untreated) was incubated with an equal amount of carrier fluid containing dispersed wax inhibitor at 1000 psi pressure of nitrogen gas for 24 hours under static condition (no mixing) at 50 C. to mimic downhole conditions. 80 mL of the oil phase was then transferred to the Cold Finger Testing apparatus for wax deposition testing. The crude sample was kept at 50 C., while the cold finger was set at 20 C. Testing was conducted for a duration of 4 hours and subsequently the amount of wax collected on the cold finger was measured by weight. Inhibition efficacy was calculated by net reduction of mass of wax collected from treated crude sample compared to the untreated one. Experiments were done in triplicate and an average is reported. The results are summarized in Table 5.

TABLE-US-00005 TABLE 5 Wax deposition and inhibition using cold finger method example wax inhibitor (wt.-% of carrier fluid) Inhibition (%) 39 (comp.) 0 0 40 0.030 wt.-% D1 14 41 0.020 wt.-% D2 10 42 0.060 wt.-% D2 52 43 0.080 wt.-% D2 58 44 0.030 wt.-% D3 18 45 0.060 wt.-% D3 62 46 0.025 wt.-% D4 9 47 0.050 wt.-% D4 42 48 0.075 wt.-% D4 65 49 0.100 wt.-% D4 71 50 0.025 wt.-% D1 + 0.025 wt.-% D2 64 51 0.050 wt.-% D5 38 52 (comp.) 0.050 wt.-% D7 2 53 (comp.) 0.200 wt.-% 12

[0218] F. Impact of Wax Inhibitors Dispersed in Carrier Fluid on Wax Deposition from Model Oil

[0219] To mimic wax deposition upon cooling of the formation by injecting fracturing fluid under downhole conditions a model crude was prepared. 1.0 wt.-% of high molecular weight paraffins with a carbon chain distribution from C.sub.35-C.sub.65 (often known in industry as problematic ones) were dissolved in kerosene. The pour point of this model oil was 42 C. In analogy to the experimental setup of examples 10 to 21 a sample of this model crude was incubated with an equal amount of carrier fluid containing 0.1 wt.-% of wax inhibitor dispersion was kept at 1000 psi pressure of nitrogen gas for 24 hours under static condition (no mixing) at 75 C.

[0220] 80 mL of the oil phase was then transferred to a Cold Finger Testing apparatus for wax deposition testing. The crude sample was kept at 50 C., while the cold finger was set at 40 C. The testing was conducted for duration of 8 hours and subsequently the amount of wax collected on the cold finger was measured by weight. Inhibition efficacy was calculated by net reduction of mass of wax deposit collected from treated crude sample compared to the untreated one. Experiments were done in duplicates and an average was reported. Results are summarized in Table 6.

TABLE-US-00006 TABLE 6 Wax deposition and inhibition using cold finger method. example Wax inhibitor Inhibition % 54 (comp.) none 0 55 D1 15 56 D2 31 57 D3 37 58 D4 49 59 D5 39 60 Mixture of D1, D3 and D4 59 (at 1:1:1 wt.-ratio) 61 Mixture of D2, D3 and D4 62 (at 1:1:1 wt.-ratio) 62 Mixture of D3 and D4 65 (at 1:1 wt.-ratio) 63 Mixture of D3, D4 and D5 61 (at 1:1:1 wt.-ratio)

[0221] The examples given in tables 5 and 6 show the efficacy of wax inhibitors dispersed in the carrier fluid on inhibition of paraffin wax deposition on surfaces. In the examples the neat crude oils selected have pour points well below the finger temperature, so they can still flow under the experimental conditions. However, at the fingers deposition of wax occurs and is reduced by addition of wax inhibitor dispersion to the carrier fluid, the reduction ranging from 15% to 65%. It was also found that a combination of inhibitors provides higher inhibition when compared to single products.

[0222] G. Impact of Wax Inhibitors Dispersed in Carrier Fluid on Fracturing Fluid Gel Stability

[0223] Stability of a borate cross-linked guar slurry fracturing fluid upon addition of wax inhibitor dispersions D1 and D3 was evaluated by measuring the viscosity of the gelled carrier fluid at elevated temperature. The carrier fluid was prepared from 0.4 wt.-% guar in 3 wt.-% KCl solution, added with wax inhibitor dispersion D1 respectively D3 and crosslinked using a borate additive. A Brookfield rotational viscometer model PVS was used to measure the viscosity of the fluid at a constant shear rate of 100 s.sup.1 and a pressure of 1000 psi. The fluid was heated to 80 C. within a period of 15 min and maintained at that temperature for 45 min. Viscosity data for the gelled fluids are given in Table 7.

TABLE-US-00007 TABLE 7 Viscosity of carrier fluid in the presence of wax inhibitor dispersion Viscosity (cP) Test carrier carrier carrier Time fluid fluid + fluid + Temp example (min) (comp.) 0.1 wt.-% D1 0.1 wt.-% D3 ( C.) 64 1 1840 1689 1603 30 65 5 1113 1254 1158 54 66 10 719 801 726 76 67 20 490 623 579 80 68 30 531 596 582 80 69 40 541 651 640 80 70 50 527 627 579 80 71 60 520 623 637 80

[0224] The viscosity of fracturing fluids has direct impact on carrying proppant loading and keeping proppant suspended during fracturing job and after fracture pressure is lifted. Linear or cross-linked gels are typically used to increase viscosity of hydraulic fracturing fluids. As found from above experiments, wax inhibitor dispersions have no negative impact on fluid viscosity at temperatures from 30 to 80 C.

[0225] H. Impact of Wax Inhibitors Dispersed in Fracturing Fluid Comprising Proppant impregnated with second wax inhibitor on crude viscosity

[0226] To show the synergism between the carrier fluid containing the dispersion of a first wax inhibitor and a solid second wax inhibitor the effect of the single components was compared with their combination.

[0227] In analogy to the experimental setup of examples 10 to 21 a crude oil with pour point of 30 C. (neat) was incubated with an equal amount of carrier fluid containing 0.1 wt.-% of a mixture of wax inhibitor dispersions D3 and D4 at 1:1 wt.-ratio (D3/D4) at 1000 psi pressure of nitrogen gas for 24 hours under static condition (no mixing) at 75 C. (example 73).

[0228] In a second test (example 74, comparative), a further sample of the same crude oil was stored in contact with the carrier fluid in the Teflon-line pressurized autoclave. Here a proppant impregnated with wax inhibitor (solid wax inhibitor) comprising a porous ceramic impregnated with polymeric wax inhibitor, having a specific gravity of 2.3 was added at 1.0 wt.-% to the system, but no wax inhibitor dispersion was added. Due to its high specific gravity the solid wax inhibitor resides in the aqueous carrier fluid.

[0229] In a third test (example 75) similar to the second, additionally wax inhibitor dispersion was added at 0.1 wt.-% to the system already comprising the solid inhibitor.

[0230] In a fourth test (example 76, comparative), crude oil was stored in contact with solid wax inhibitor but no carrier fluid was included.

[0231] In a further set of comparative tests in analogy to examples 73 and 75 the mixture of wax inhibitor dispersions D3 and D4 was substituted by 0.1 wt.-% of dispersion D7.

[0232] The crudes were collected after 24 hours and analysed using steady shear viscosity measurement upon a cooling program at shear rate of 10 s.sup.1. Results are summarized in Table 8.

TABLE-US-00008 TABLE 8 Crude oil viscosity data after incubation for 24 hours. Viscosity (cP) example experiment 20 C. 30 C. 40 C. 50 C. 60 C. 72 (comp.) untreated crude oil 2580 556 72.4 15.6 6.3 73 crude + CF + WID (D3/D4) 763 48.6 15.8 8.2 6.1 74 (comp.) crude + CF + SPI 2326 550 71.0 16.2 6.2 75 crude + CF + WID + SPI 689 42.4 14.2 7.9 5.3 76 (comp.) crude + SPI 942 51.3 18.4 8.5 5.6 77 (comp.) crude + CF + WID (D7) 2187 516 64.3 14.8 6.1 78 (comp.) crude + CF + WID (D7) + SPI 1956 472 60.1 14.1 6.0 * WID = wax inhibitor dispersion, consisting of 0.1 wt.-% of a mixture of equal amounts of D3 and D4; CF = carrier fluid; SPI = solid wax inhibitor;

[0233] Results of examples 74 and 76 clearly demonstrate that once solid paraffin inhibitor is in direct contact with crude, active component is released from the substrate and reduces the viscosity of the crude oil. However, as demonstrated in comparative example 74, the solid wax inhibitor does not have any effect on crude viscosity when it resides in the carrier fluid; no inhibitor is partitioned to the oil phase and thus no impact on rheology is observed. On the other hand, in examples 73 and 75 when a dispersion of wax inhibitor is used with or without solid wax inhibitor, an immediate effect occurs as pronounced in net viscosity reduction upon cooling at steady shear rate. This clearly indicates benefits of utilization of wax inhibitor dispersion in the carrier fluid to manage wax formation and deposition in early stages of fracturing operations.