Cross-linking agent for fracturing and preparation method thereof

Abstract

The invention relates to the technical field of cross-linking agents, and discloses a cross-linking agent for fracturing and a preparation method thereof.The preparation method comprises the steps that a tri (2-aminoethyl) amine diBoc compound, dibromoalkane, glycidol, trifluoroacetic acid and the like are subjected to a reaction, and a polyhydramine complexing agent is obtained; and then reacting with sodium hydroxide and borax to obtain the cross-linking agent for fracturing. The polyhydramine complexing agent contains a plurality of active crosslinking sites of hydroxyl and amino, and reacts with borax to obtain the crosslinking agent for fracturing, so that the crosslinking degree of the crosslinking agent and hydroxypropyl guar gum fracturing fluid is improved, and the polyhydramine complexing agent has very long crosslinking time in a low-concentration guar gum fracturing fluid system and shows good hanging performance under long-time stirring. And the cross-linking agent and the hydroxypropyl guar gum form a stable gel system which shows good high temperature resistance and still has good viscosity at high temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of crosslinking agents, and specifically to a crosslinking agent for fracturing and a preparation method thereof. Background Art

[0002] Guar gum has good water solubility, thickening property, and is cheap, easy to obtain, non-toxic and environmentally friendly, and has wide applications in thickeners, fracturing fluids, etc. Guar gum fracturing fluid usually consists of hydroxypropyl guar gum, crosslinking agent, breaker, stabilizer, etc., and has advantages such as high viscosity, good anti-shearing performance, complete breaking and easy flowback. Among them, the crosslinking agent has a great influence on the performance of guar gum fracturing fluid. Currently, the most common crosslinking agent for guar gum fracturing fluid is an organic boron crosslinking agent, which is mainly prepared by reacting complexing agents such as polyols and polyamines with boric acid and borax. Chinese Patent with publication number CN114213464B discloses a boron-antimony composite crosslinking agent and its preparation method, and a carboxymethyl hydroxypropyl guar gum fracturing fluid system. By reacting an inorganic antimony salt with a polyolamine, an organic acid, boric acid, and an inorganic basic substance, a boron-antimony composite crosslinking agent is obtained, which improves the shear resistance, easy recovery and other properties of the guar gum fracturing fluid. However, this composite crosslinking agent does not improve the crosslinking time of the fracturing fluid. Summary of the Invention

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

[0004] Technical Solution: A preparation method of a crosslinking agent for fracturing: (1) Add potassium carbonate and tris(2-aminoethyl)amine diBoc compound to deionized water. After stirring, add dibromoalkane and ethanol, stir and react, add dichloromethane, shake and then let it stand for layer separation. Separate to obtain 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 obtain a complexing agent precursor. The reaction formula is: .

[0005] (2) Add the complexing agent precursor and glycidol to ethanol, stir and react, rotary evaporate to remove ethanol, then add dichloromethane and trifluoroacetic acid, continue to react, add an 8-12% sodium bicarbonate aqueous solution by mass fraction, shake and then let it stand for layer separation. Separate to obtain 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 obtain a polyolamine complexing agent. The reaction formula is: .

[0006] (3) Add deionized water, sodium hydroxide, and polyolamine complexing agent to the reaction kettle, stir, then add borax, introduce nitrogen, stir and react, cool and discharge to obtain a crosslinking agent for fracturing.

[0007] Among them, the temperature of the reaction in (1) is 70 - 80 °C, and the reaction time is 6 - 10 h.

[0008] Among them, in (1), the molar ratio of potassium carbonate, tris(2-aminoethyl)amine diBoc compound, and dibromoalkane after stirring is (2 - 2.4):(3 - 5):1. The structural formula of the dibromoalkane is Br-(CH2) n Br, where n is any integer from 2 to 6.

[0009] Among them, in (2), the molar ratio of the complexing agent precursor to glycidol is 1:(2.6 - 3.4).

[0010] Among them, in (2), the temperature of the stirring reaction is 60 - 70 °C, and the reaction time is 6 - 8 h; the temperature of the continued reaction is 20 - 30 °C, and the reaction time is 2 - 3 h.

[0011] Among them, in (3), the molar ratio of sodium hydroxide, polyolamine complexing agent, and borax is :(4 - 4.8):1:(8 - 10).

[0012] Among them, in (3), the temperature of the reaction is 120 - 130 °C, and the reaction time is 5 - 7 h.

[0013] The beneficial technical effects of the present invention: The present invention uses tris(2-aminoethyl)amine diBoc compound, dibromoalkane, glycidol, etc. as raw materials to prepare a novel polyolamine complexing agent, which contains multiple active cross-linking sites of hydroxyl and amino groups. The more cross-linking sites, the higher the complexing performance of borate ions. Reacting with borax to obtain a cross-linking agent for fracturing, which improves the cross-linking degree of the cross-linking agent with the hydroxypropyl guar gum fracturing fluid. In a low-concentration guar gum fracturing fluid system, it has a long cross-linking time and shows good suspending performance under long-term stirring. And the cross-linking agent forms a stable gel system with hydroxypropyl guar gum, showing good high-temperature resistance and still having good viscosity at high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is the infrared spectrum diagram of the complexing agent precursor prepared in Example 1.

[0015] Figure 2 It is the infrared spectrum diagram of the polyolamine complexing agent prepared in Example 1.

[0016] Figure 3 It is the infrared spectrum diagram of the cross-linking agent for fracturing prepared in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hydroxypropyl guar gum, with an active substance content of 99%, was purchased from Shandong Guangpu Biotechnology Co., Ltd. The co - surfactant model is LX - 2009, purchased from Shaanxi Lanxin Chemical Co., Ltd. The breaker model is F3309, purchased from Jiujiang Lanzuo New Materials Technology Co., Ltd.

[0018] The tris(2 - aminoethyl)amine diBoc compound was prepared according to the method described in the journal Chem. Commun, 2019, 55, 4761 - 4764, literature "Double - headed nanosystems for oral drug delivery". Add 6.83 mmol of tris(2 - aminoethyl)amine to 10 mL of methanol, add 13.6 mmol of di - tert - butyl dicarbonate, 50 mL of triethylamine in a nitrogen atmosphere, react at 20 °C for 24 h, rotary evaporate to remove methanol, add dichloromethane, extract and wash successively with 1 mol / L hydrochloric acid solution and deionized water, collect 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 obtain the tris(2 - aminoethyl)amine diBoc compound, whose structural formula is .

[0019] Example 1 (1) Add 40 mmol of potassium carbonate and 80 mmol of tris(2 - aminoethyl)amine diBoc compound to 80 mL of deionized water. After stirring, add 20 mmol of 1,4 - dibromobutane and 20 mL of ethanol, heat to 70 °C, stir and reflux for 10 h, add dichloromethane, shake and let stand for liquid - liquid separation, 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 obtain the complexing agent precursor. Figure 1 In the infrared spectrum of, the absorption peak at 1751 cm -1 is the absorption peak of the carbonyl - C=O -, and the absorption peak at 1348 cm -1 is the absorption peak of the tert - butyl - C(CH3)3.

[0020] (2) Add 20 mmol of the complexing agent precursor and 58 mmol of glycidol to 150 mL of ethanol, heat to 65 °C, stir and reflux for 8 h, rotary evaporate to remove ethanol, then add 80 mL of dichloromethane and 30 mL of trifluoroacetic acid, react at 25 °C for 3 h, add 10% sodium bicarbonate aqueous solution by mass, shake and let stand for liquid - liquid separation, 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 obtain the polyolamine complexing agent. Figure 2 In the infrared spectrum of, the absorption peaks at 3395 - 3476 cm -1 are the absorption peaks of hydroxyl and amino groups, and 1751 cm-1 The absorption peak of the carbonyl group -C=O- and 1348 cm -1 The absorption peak of the tert-butyl group -C(CH3)3 disappeared.

[0021] (3) Add 30 mL of deionized water, 40 mmol of sodium hydroxide, and 10 mmol of polyol amine complexing agent to the reaction kettle. After stirring, add 10 mmol of borax, introduce nitrogen gas, heat to 130 °C, stir and react for 5 h, cool and discharge to obtain a crosslinking agent for fracturing. Figure 3 In the infrared spectrum diagram of, 1524 cm -1 is the absorption peak of the B-N bond, 1398 cm -1 is the absorption peak of the B-O bond.

[0022] Example 2 (1) Add 44 mmol of potassium carbonate and 60 mmol of tris(2-aminoethyl)amine diBoc compound to 100 mL of deionized water. After stirring, add 20 mmol of 1,2-dibromoethane and 20 mL of ethanol, heat to 75 °C, stir and reflux for 6 h, add dichloromethane, shake and let stand for liquid separation, separate to obtain 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 obtain the complexing agent precursor.

[0023] (2) Add 20 mmol of the complexing agent precursor and 68 mmol of glycidol to 200 mL of ethanol, heat to 70 °C, stir and reflux for 6 h, rotary evaporate to remove ethanol, then add 80 mL of dichloromethane and 40 mL of trifluoroacetic acid, react at 30 °C for 2 h, add an aqueous solution of 12% sodium bicarbonate by mass fraction, shake and let stand for liquid separation, separate to obtain 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 obtain the polyol amine complexing agent.

[0024] (3) Add 30 mL of deionized water, 40 mmol of sodium hydroxide, and 10 mmol of polyol amine complexing agent to the reaction kettle. After stirring, add 8 mmol of borax, introduce nitrogen gas, heat to 130 °C, stir and react for 5 h, cool and discharge to obtain a crosslinking agent for fracturing.

[0025] Example 3 (1) Add 48 mmol of potassium carbonate and 100 mmol of tris(2-aminoethyl)amine diBoc compound to 100 mL of deionized water. After stirring, add 20 mmol of 1,6-dibromohexane and 30 mL of ethanol. Heat to 70 °C, stir and reflux for 10 h. Add dichloromethane, shake and let stand for phase separation. 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 obtain the complexing agent precursor.

[0026] (2) Add 20 mmol of the complexing agent precursor and 52 mmol of glycidol to 150 mL of ethanol. Heat to 70 °C, stir and reflux for 6 h. Rotary evaporate to remove ethanol, then add 70 mL of dichloromethane and 40 mL of trifluoroacetic acid, react at 20 °C for 3 h. Add an aqueous solution of 12% sodium bicarbonate by mass, shake and let stand for phase separation. 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 obtain the polyolamine complexing agent.

[0027] (3) Add 35 mL of deionized water, 44 mmol of sodium hydroxide, and 10 mmol of the polyolamine complexing agent to the reaction kettle. After stirring, add 9 mmol of borax, introduce nitrogen, heat to 125 °C, stir and react for 7 h, cool and discharge to obtain the crosslinking agent for fracturing.

[0028] Example 4 (1) Add 44 mmol of potassium carbonate and 80 mmol of tris(2-aminoethyl)amine diBoc compound to 100 mL of deionized water. After stirring, add 20 mmol of 1,3-dibromopropane and 20 mL of ethanol. Heat to 80 °C, stir and reflux for 6 h. Add dichloromethane, shake and let stand for phase separation. 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 obtain the complexing agent precursor.

[0029] (2) Add 20 mmol of the complexing agent precursor and 60 mmol of glycidol to 200 mL of ethanol. Heat to 60 °C, stir and reflux for 8 h. Rotary evaporate to remove ethanol, then add 70 mL of dichloromethane and 30 mL of trifluoroacetic acid, react at 25 °C for 3 h. Add an aqueous solution of 8% sodium bicarbonate by mass, shake and let stand for phase separation. 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 obtain the polyolamine complexing agent.

[0030] (3) Add 35 mL of deionized water, 40 mmol of sodium hydroxide, and 10 mmol of a polyol amine complexing agent into a reactor, stir, add 9 mmol of borax, introduce nitrogen, heat to 120°C, stir and react for 7 h, cool and discharge the product, and obtain a cross-linking agent for fracturing.

[0031] Comparative Example 1 (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.

[0032] (2) Add 35 mL of deionized water, 44 mmol of sodium hydroxide, and 10 mmol of a polyol complexing agent into a reaction kettle, 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.

[0033] Comparative Example 2 (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 into a reaction kettle, stir, add 9 mmol of borax, introduce nitrogen, heat to 125°C, stir and react for 7 h, cool and discharge, and obtain a cross-linking agent.

[0034] Comparative Example 3 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 cross-linking agent.

[0035] 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 cross-linking agent were added to 100 mL of deionized water, and sodium hydroxide was added to adjust the pH to 11, and the mixture was stirred to form a gel fracturing fluid. The cross-linking time of the gel fracturing fluid was tested according to the SYT5107-2016 standard.

[0036] 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.

[0037] Table 1 Fracturing fluid performance cross-linking test Crosslinking 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 Table 2 Fracturing fluid viscosity test

[0038] After testing, compared with Comparative Examples 1-3, in Examples 1-4, a polyolamine complexing agent reacts with borax to obtain a crosslinking agent for fracturing. The polyolamine complexing agent contains active crosslinking sites with multiple hydroxyl and amino groups. The more crosslinking sites there are, the higher the complexing performance with borate ions, thereby increasing the content of borate in the crosslinking agent, which is beneficial to improving the crosslinking degree of the crosslinking agent with the hydroxypropyl guar gum fracturing fluid. In a low-concentration guar gum fracturing fluid system, it also has a long crosslinking time and exhibits good suspending performance under long-term stirring. Moreover, the crosslinking agent forms a stable gel system with hydroxypropyl guar gum, showing good high-temperature resistance. At a high temperature of 140 °C, it still has good viscosity.

Claims

1. A preparation method of a crosslinking agent for fracturing, characterized in that, The preparation method is as follows: (1) Add potassium carbonate and tris(2-aminoethyl)amine diBoc compound with the structural formula to deionized water. After stirring, add dibromoalkane and ethanol, stir and react, add dichloromethane, shake and then let it stand for layer separation. 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 obtain the complexing agent precursor; The molar ratio of potassium carbonate, tris(2-aminoethyl)amine diBoc compound, and dibromoalkane is (2 - 2.4):(3 - 5):1; (2) Add the complexing agent precursor and glycidol to ethanol, stir and react, rotary evaporate to remove ethanol, then add dichloromethane and trifluoroacetic acid, continue to react, add an aqueous solution of sodium bicarbonate, shake and let stand for liquid separation, separate to obtain 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 obtain the polyolamine complexing agent; The molar ratio of the complexing agent precursor to glycidol is 1:(2.6 - 3.4); (3) Add deionized water, sodium hydroxide, and polyolamine complexing agent to the reaction kettle, stir, add borax, introduce nitrogen, stir and react, cool and discharge to obtain the crosslinking agent for fracturing; The molar ratio of sodium hydroxide, polyolamine complexing agent, and borax is (4 - 4.8):1:(8 - 10).

2. The preparation method of the crosslinking agent for fracturing according to claim 1, wherein, The temperature of the reaction in (1) is 70 - 80 °C, and the reaction time is 6 - 10 h.

3. The preparation method of the crosslinking agent for fracturing according to claim 1, characterized in that, The structural formula of the dibromoalkane is Br-(CH2) n Br, where n is any integer from 2 to 6.

4. The preparation method of the crosslinking agent for fracturing according to claim 1, wherein, The temperature of the stirring reaction in (2) is 60 - 70 °C, and the reaction time is 6 - 8 h; the temperature of the continued reaction is 20 - 30 °C, and the reaction time is 2 - 3 h.

5. The preparation method of the crosslinking agent for fracturing according to claim 1, wherein The temperature of the reaction in (3) is 120 - 130 °C, and the reaction time is 5 - 7 h.

6. A crosslinking agent for fracturing obtained by the preparation method according to any one of claims 1 - 5.

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