A crosslinking agent for fracturing and its preparation method

Abstract

The present invention relates to the technical field of cross-linking agents and discloses a cross-linking agent for fracturing and a preparation method thereof. The invention involves reacting a tris(2-aminoethyl)amine diBoc compound, a dibromoalkane, glycidol, trifluoroacetic acid, and the like to obtain a polyolamine complexing agent; the polyolamine complexing agent is then reacted with sodium hydroxide and borax to obtain the cross-linking agent for fracturing. The polyolamine complexing agent contains multiple active cross-linking sites of hydroxyl and amino groups. When reacted with borax, the cross-linking agent for fracturing is obtained. This improves the degree of cross-linking between the cross-linking agent and hydroxypropyl guar gum fracturing fluid, exhibits a long cross-linking time in a low-concentration guar gum fracturing fluid system, and exhibits good pick-up performance under prolonged stirring. Furthermore, the cross-linking agent and hydroxypropyl guar gum form a stable gel system, exhibiting excellent high-temperature resistance and maintaining good viscosity even at high temperatures.

Description

Technical Field

[0001] The present invention relates to the technical field of cross-linking agents, in particular to a cross-linking agent for fracturing and a preparation method thereof. Background Art

[0002] Guar gum has good water solubility and thickening properties, and is cheap and easy to obtain, non-toxic and environmentally friendly, and is widely used in aspects such as thickeners and fracturing fluids. Guar gum fracturing fluid is usually composed of hydroxypropyl guar gum, a cross-linking agent, a gel breaker, a stabilizer, etc., and has the advantages of high viscosity, good shear resistance, and easy flowback of gel breaking. Among them, the cross-linking agent has a great impact on the performance of guar gum fracturing fluid. At present, the most common cross-linking agent of guar gum fracturing fluid is an organic boron cross-linking agent, which is mainly prepared by reacting complexing agents such as polyols and polyamines with boric acid and borax. Publication number CN114213464B discloses a boron antimony composite cross-linking agent and its preparation method, a carboxymethyl hydroxypropyl guar gum fracturing fluid system, wherein an inorganic antimony salt is reacted with a polyol amine, an organic acid, boric acid, and an inorganic alkaline substance to obtain a boron antimony composite cross-linking agent, which improves the shear resistance of the guar gum fracturing fluid and the performance such as easy recovery, but the composite cross-linking agent does not improve the cross-linking time of the fracturing fluid. Summary of the Invention

[0003] The invention solves the problems of poor high temperature resistance and low crosslinking time of the organic boron crosslinking agent.

[0004] Technical solution: A method for preparing a cross-linking agent for fracturing:

[0005] (1) Add potassium carbonate and tris(2-aminoethyl)amine diBoc compound to deionized water, stir, then add dibromoalkane and ethanol, stir and react, add dichloromethane, shake and let stand to separate, separate the dichloromethane organic phase, rotary evaporate, and separate the product by silica gel column chromatography, using a mixed solution of dichloromethane and methanol as the mobile phase to separate the complexing agent precursor. The reaction formula is:

[0006] .

[0007] (2) Add the complexing agent precursor and propylene glycol to ethanol, stir to react, and remove the ethanol by rotary evaporation. Then add dichloromethane and trifluoroacetic acid, continue the reaction, add 8-12% sodium bicarbonate aqueous solution, shake and let stand to separate the layers, separate the dichloromethane organic phase, rotary evaporate, and separate the product by silica gel column chromatography, using a mixed solution of dichloromethane and methanol as the mobile phase to separate the polyolamine complexing agent. The reaction formula is:

[0008] .

[0009] (3) Add deionized water, sodium hydroxide, and polyolamine complexing agent into the reactor, stir, add borax, introduce nitrogen, stir to react, cool and discharge, and obtain a cross-linking agent for fracturing.

[0010] The reaction temperature in (1) is 70-80°C and the reaction time is 6-10h.

[0011] The potassium carbonate and tris(2-aminoethyl)amine diBoc compound in (1) are stirred and then added with dibromoalkane in a molar ratio of (2-2.4):(3-5):1. The structural formula of dibromoalkane is Br-(CH2) n Br, n is any integer from 2 to 6.

[0012] Among them, the molar ratio of the complexing agent precursor and propylene oxide in (2) is 1: (2.6-3.4).

[0013] The stirring reaction temperature in (2) is 60-70°C, and the reaction time is 6-8h; the continued reaction temperature is 20-30°C, and the reaction time is 2-3h.

[0014] Among them, the molar ratio of sodium hydroxide, polyol amine complexing agent and borax in (3) is: (4-4.8):1: (8-10).

[0015] The reaction temperature in (3) is 120-130°C, and the reaction time is 5-7h.

[0016] The present invention has the beneficial technical effects of preparing a novel polyolamine complexing agent using tris(2-aminoethyl)amine (diBoc), dibromoalkanes, and glycidol as raw materials. This complexing agent contains multiple active crosslinking sites with hydroxyl and amino groups. The more crosslinking sites, the higher the complexing performance of borate ions. When reacted with borax, it produces a crosslinking agent for fracturing. This improves the degree of crosslinking between the crosslinker and hydroxypropyl guar gum fracturing fluid. In low-concentration guar gum fracturing fluid systems, the crosslinking agent exhibits a long crosslinking time and good pick-up performance under prolonged stirring. Furthermore, the crosslinker and hydroxypropyl guar gum form a stable gel system that exhibits excellent high-temperature resistance and maintains good viscosity even at high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the infrared spectrum of the complexing agent precursor prepared in Example 1.

[0018] Figure 2 This is the infrared spectrum of the polyolamine complexing agent prepared in Example 1.

[0019] Figure 3 This is the infrared spectrum of the cross-linking agent for fracturing prepared in Example 1. DETAILED DESCRIPTION

[0020] Hydroxypropyl guar gum, active substance content 99%, was purchased from Shandong Guangpu Biotechnology Co., Ltd. Drainage aid model LX-2009 was purchased from Shaanxi Lanxin Chemical Co., Ltd. Gel breaker model F3309 was purchased from Jiujiang Lanzhuo New Materials Technology Co., Ltd.

[0021] The tris(2-aminoethyl)amine diBoc compound was prepared according to the method described in the journal Chem. Commun, 2019, 55, 4761-4764, in the document "Double-headed nanosystems for oral drug delivery". 6.83 mmol of tris(2-aminoethyl)amine was added to 10 mL of methanol, and 13.6 mmol of di-tert-butyl dicarbonate and 50 mL of triethylamine were added under a nitrogen atmosphere. The mixture was reacted at 20°C for 24 hours. The methanol was removed by rotary evaporation, and dichloromethane was added. The mixture was extracted and washed with 1 mol / L hydrochloric acid solution and deionized water in sequence. The dichloromethane organic phase was collected and rotary evaporated. The product was separated by silica gel column chromatography using a mixed solution of dichloromethane and methanol as the mobile phase to obtain the tris(2-aminoethyl)amine diBoc compound with the structural formula: .

[0022] Example 1

[0023] (1) Add 40 mmol potassium carbonate and 80 mmol tris(2-aminoethyl)amine diBoc compound to 80 mL deionized water, stir, add 20 mmol 1,4-dibromobutane and 20 mL ethanol, heat to 70 °C, stir and reflux for 10 h, add dichloromethane, shake and let stand to separate the layers, separate the dichloromethane organic phase, rotary evaporate, and separate the product by silica gel column chromatography using a mixed solution of dichloromethane and methanol as the mobile phase to separate the complexing agent precursor. Figure 1 In the infrared spectrum, 1751 cm -1 It is the absorption peak of carbonyl -C=O-, 1348cm -1 It is the absorption peak of tert-butyl -C(CH3)3.

[0024] (2) Add 20 mmol of complexing agent precursor and 58 mmol of glycidol to 150 mL of ethanol, heat to 65 ° C, stir and condense under reflux for 8 h, remove ethanol by rotary evaporation, then add 80 mL of dichloromethane and 30 mL of trifluoroacetic acid, react at 25 ° C for 3 h, add 10% by mass sodium bicarbonate aqueous solution, shake and let stand to separate the layers, separate the dichloromethane organic phase, rotary evaporate, and separate the product by silica gel column chromatography, using a mixed solution of dichloromethane and methanol as the mobile phase to separate the polyol amine complexing agent. Figure 2 In the infrared spectrum, 3395-3476 cm -1It is the absorption peak of hydroxyl and amino groups, and 1751cm -1 The absorption peak of carbonyl -C=O- and 1348cm -1 The absorption peak of tert-butyl-C(CH3)3 disappears.

[0025] (3) Add 30 mL of deionized water, 40 mmol of sodium hydroxide, and 10 mmol of a polyol amine complexing agent to the reactor, stir, add 10 mmol of borax, introduce nitrogen, heat to 130 ° C, stir and react for 5 h, cool and discharge the material to obtain a cross-linking agent for fracturing. Figure 3 In the infrared spectrum, 1524 cm -1 is the absorption peak of BN bond, 1398cm -1 It is the absorption peak of BO bond.

[0026] Example 2

[0027] (1) Add 44 mmol potassium carbonate and 60 mmol tris(2-aminoethyl)amine diBoc compound to 100 mL deionized water, stir, add 20 mmol 1,2-dibromoethane and 20 mL ethanol, heat to 75 °C, stir and reflux for 6 h, add dichloromethane, shake and let stand to separate the layers, separate the dichloromethane organic phase, rotary evaporate, and separate the product by silica gel column chromatography using a mixed solution of dichloromethane and methanol as the mobile phase to separate the complexing agent precursor.

[0028] (2) Add 20 mmol of complexing agent precursor and 68 mmol of glycidol to 200 mL of ethanol, heat to 70 °C, stir and reflux under condensation for 6 h, remove ethanol by rotary evaporation, then add 80 mL of dichloromethane and 40 mL of trifluoroacetic acid, react at 30 °C for 2 h, add 12% sodium bicarbonate aqueous solution by mass, shake and let stand to separate the layers, separate the dichloromethane organic phase, rotary evaporate, and separate the product by silica gel column chromatography using a mixed solution of dichloromethane and methanol as the mobile phase to separate the polyolamine complexing agent.

[0029] (3) Add 30 mL of deionized water, 40 mmol of sodium hydroxide, and 10 mmol of a polyolamine complexing agent to the reactor, stir, add 8 mmol of borax, introduce nitrogen, heat to 130 ° C, stir and react for 5 h, cool and discharge the material to obtain a cross-linking agent for fracturing.

[0030] Example 3

[0031] (1) Add 48 mmol potassium carbonate and 100 mmol tris(2-aminoethyl)amine diBoc compound to 100 mL deionized water, stir, add 20 mmol 1,6-dibromohexane and 30 mL ethanol, heat to 70 °C, stir and reflux for 10 h, add dichloromethane, shake and let stand to separate the layers, separate the dichloromethane organic phase, rotary evaporate, and separate the product by silica gel column chromatography using a mixed solution of dichloromethane and methanol as the mobile phase to separate the complexing agent precursor.

[0032] (2) Add 20 mmol of complexing agent precursor and 52 mmol of glycidol to 150 mL of ethanol, heat to 70 ° C, stir and condense under reflux for 6 h, remove ethanol by rotary evaporation, then add 70 mL of dichloromethane and 40 mL of trifluoroacetic acid, react at 20 ° C for 3 h, add 12% by mass sodium bicarbonate aqueous solution, shake and let stand to separate the layers, separate the dichloromethane organic phase, rotary evaporate, and separate the product by silica gel column chromatography, using a mixed solution of dichloromethane and methanol as the mobile phase to separate the polyol amine complexing agent.

[0033] (3) Add 35 mL of deionized water, 44 mmol of sodium hydroxide, and 10 mmol of a polyol amine complexing agent to the reactor, stir, add 9 mmol of borax, introduce nitrogen, heat to 125 ° C, stir and react for 7 h, cool and discharge the material to obtain a cross-linking agent for fracturing.

[0034] Example 4

[0035] (1) Add 44 mmol potassium carbonate and 80 mmol tris(2-aminoethyl)amine diBoc compound to 100 mL deionized water, stir, add 20 mmol 1,3-dibromopropane and 20 mL ethanol, heat to 80 °C, stir and reflux for 6 h, add dichloromethane, shake and let stand to separate the layers, separate the dichloromethane organic phase, rotary evaporate, and separate the product by silica gel column chromatography using a mixed solution of dichloromethane and methanol as the mobile phase to separate the complexing agent precursor.

[0036] (2) Add 20 mmol of complexing agent precursor and 60 mmol of glycidol to 200 mL of ethanol, heat to 60 ° C, stir and condense under reflux for 8 h, remove ethanol by rotary evaporation, then add 70 mL of dichloromethane and 30 mL of trifluoroacetic acid, react at 25 ° C for 3 h, add 8% by mass sodium bicarbonate aqueous solution, shake and let stand to separate the layers, separate the dichloromethane organic phase, rotary evaporate, and separate the product by silica gel column chromatography, using a mixed solution of dichloromethane and methanol as the mobile phase to separate the polyol amine complexing agent.

[0037] (3) Add 35 mL of deionized water, 40 mmol of sodium hydroxide, and 10 mmol of a polyol amine complexing agent to the reactor, stir, add 9 mmol of borax, introduce nitrogen, heat to 120 ° C, stir and react for 7 h, cool and discharge the material to obtain a cross-linking agent for fracturing.

[0038] Comparative Example 1

[0039] (1) Add 20 mmol of tris(2-aminoethyl)amine and 120 mmol of glycidol to 150 mL of ethanol, heat to 70°C, stir and reflux for 6 h, remove ethanol by rotary evaporation, and separate the product by silica gel column chromatography using a mixed solution of dichloromethane and methanol as the mobile phase to obtain a polyol complexing agent.

[0040] (2) Add 35 mL of deionized water, 44 mmol of sodium hydroxide, and 10 mmol of a polyol complexing agent to the reactor, stir, add 9 mmol of borax, introduce nitrogen, heat to 125 ° C, stir and react for 7 h, cool and discharge the material to obtain a cross-linking agent.

[0041] Comparative Example 2

[0042] (1) Add 35 mL of deionized water, 44 mmol of sodium hydroxide, and 10 mmol of N,N-bis(2-hydroxyethyl)ethylenediamine as a polyol complexing agent to the reactor, stir, add 9 mmol of borax, introduce nitrogen, heat to 125 °C, stir and react for 7 h, cool and discharge to obtain a crosslinking agent.

[0043] Comparative Example 3

[0044] Add 5 g of boric acid and 9.8 g of ethylene glycol to 5 mL of ethanol, heat to 80°C, stir and reflux for 2 h, remove the solvent by distillation under reduced pressure, then add 9.6 g of tetraethylenepentamine, heat to 150°C, react for 4 h, cool and discharge to obtain a crosslinking agent.

[0045] To 100 mL of deionized water, add 0.4 g of hydroxypropyl guar gum, 0.16 g of drainage aid, 0.04 g of shale oil breaker, and 0.22 g of crosslinker. Adjust the pH to 11 with sodium hydroxide and stir to form a gel fracturing fluid. Test the crosslinking time of the gel fracturing fluid according to the SYT5107-2016 standard.

[0046] The viscosity of the fracturing fluid at different temperatures was tested using a high-temperature and high-pressure rheometer with a shear rate of 170s -1 , shearing time 10min.

[0047] Table 1 Fracturing fluid performance cross-linking test

[0048] Cross-linking time (s) Example 1 167.8 Example 2 253.6 Example 3 196.0 Example 4 215.3 Comparative Example 1 121.7 Comparative Example 2 81.0 Comparative Example 3 93.6

[0049] Table 2 Fracturing fluid viscosity test

[0050]

[0051] After testing, compared with Comparative Examples 1-3, Examples 1-4 reacted a polyolamine complexing agent with borax to obtain a crosslinking agent for fracturing. The polyolamine complexing agent contained multiple active crosslinking sites of hydroxyl and amino groups. The more crosslinking sites, the higher the complexing performance with borate ions, thereby increasing the borate content in the crosslinking agent, which is beneficial for increasing the crosslinking degree between the crosslinking agent and the hydroxypropyl guar gum fracturing fluid. Even in a low-concentration guar gum fracturing fluid system, the crosslinking time was very long and good hanging performance was exhibited under long-term stirring. In addition, the crosslinking agent and hydroxypropyl guar gum formed a stable jelly system, exhibiting good high-temperature resistance and still having good viscosity at a high temperature of 140°C.

Claims

1. A method for preparing a cross-linking agent for fracturing, characterized in that: The preparation method is: (1) Add potassium carbonate and the structural formula tris(2-aminoethyl)amine di-tert-butyloxycarbonyl compound, stirring, adding dibromoalkane and ethanol, stirring to react, adding dichloromethane, shaking, standing and layering, separating to obtain a dichloromethane organic phase, rotary evaporation, and separating the product by silica gel column chromatography, using a mixed solution of dichloromethane and methanol as the mobile phase, to separate and obtain a complexing agent precursor; The structural formula of the dibromoalkane is Br-(CH2) n Br, n is any integer from 2 to 6; The structural formula of the complexing agent precursor is as follows: ； The molar ratio of potassium carbonate, tris(2-aminoethyl)amine di-tert-butyloxycarbonyl compound, and dibromoalkane is (2-2.4):(3-5):1; (2) Adding a complexing agent precursor and propylene oxide to ethanol, stirring the reaction, and removing the ethanol by rotary evaporation, then adding dichloromethane and trifluoroacetic acid, continuing the reaction, adding a sodium bicarbonate aqueous solution, shaking and standing to separate the layers, separating the dichloromethane organic phase, rotary evaporation, and separating the product by silica gel column chromatography, using a mixed solution of dichloromethane and methanol as the mobile phase to separate the polyolamine complexing agent; The molar ratio of the complexing agent precursor to glycidol is 1:(2.6-3.4); The structural formula of the polyolamine complexing agent is as follows: ； (3) Add deionized water, sodium hydroxide, and a polyolamine complexing agent to a reactor, stir, add borax, introduce nitrogen, stir to react, cool, and discharge to obtain a cross-linking agent for fracturing; The molar ratio of the sodium hydroxide, the polyol amine complexing agent and the borax is: (4-4.8):1:(8-10).

2. The method for preparing a cross-linking agent for fracturing according to claim 1, characterized in that: The reaction temperature in (1) is 70-80°C and the reaction time is 6-10h.

3. The method for preparing a cross-linking agent for fracturing according to claim 1, characterized in that: The temperature for the stirring reaction in (2) is 60-70°C, and the reaction time is 6-8h; the temperature for the continued reaction is 20-30°C, and the reaction time is 2-3h.

4. The method for preparing a cross-linking agent for fracturing according to claim 1, characterized in that: The reaction temperature in (3) is 120-130°C, and the reaction time is 5-7h.

5. A cross-linking agent for fracturing obtained by the preparation method according to any one of claims 1 to 4.

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