Preparation method of high-temperature-resistant thickening agent for fracturing

Abstract

The invention relates to the technical field of thickening agents, and discloses a preparation method of a high-temperature-resistant thickening agent for fracturing. According to the preparation method disclosed by the invention, acrylamide, sulfobetaine modified acrylamide and pyrrolidone modified naphthyl melamine are polymerized, so that the thickening agent for high-temperature-resistant fracturing is obtained. A triazine ring structure and naphthyl have high stability, the rigidity of a polyacrylamide molecular chain and the hydrophobic association effect between molecules are enhanced, the high temperature resistance and the salt resistance are improved, and due to the conjugation effect formed by two benzene rings in naphthyl, the thermal stability is further enhanced; by introducing vinyl pyrrolidone, hydrolysis of amido in polyacrylamide can be inhibited, and the temperature resistance and salt resistance of the thickening agent are improved; under a high-salt condition, due to weakening and shielding of mutual attraction of salt ions to anionic and cationic groups in the sulfobetaine, polyacrylamide molecules are more stretched, macroscopically, the viscosity is increased or reduced slightly, and the temperature resistance and salt resistance are improved.

Description

Technical Field

[0001] The invention relates to the technical field of thickeners, and in particular to a method for preparing a thickener for high temperature resistant fracturing. Background Art

[0002] Thickener is the main additive of water-based fracturing fluid. Its main function is to increase the viscosity and consistency of fracturing fluid and improve the fracturing effect. Its performance has an important influence on the comprehensive performance of fracturing fluid and the fracturing construction effect. Polyacrylamide thickener is the most widely used thickener in oil fields. Conventional polyacrylamide mainly increases viscosity through the hydration of its molecular skeleton and the increase of hydrodynamic volume. Since the molecular chain is not rigid, it is easily affected by conditions such as salt and temperature. With the development of deep oil and gas, higher temperature and salt resistance requirements are put forward for thickeners for fracturing. In the document "Synthesis Research of Thickener for Emulsion Fracturing", a fracturing thickener was synthesized with acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid as monomers. It has the advantages of fast dissolution speed, high viscosity, low damage, simple and quick preparation, etc., but its temperature and salt resistance needs to be improved. Summary of the invention

[0003] 1. Technical issues to be resolved

[0004] In view of the shortcomings of the prior art, the present invention provides a method for preparing a high temperature resistant fracturing thickener. The fracturing thickener prepared by the present invention has good high temperature resistance and salt resistance.

[0005] (II) Technical solution

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing a high temperature resistant fracturing thickener, the method for preparing a high temperature resistant fracturing thickener comprising the following steps:

[0007] (1) adding 18-24 g of melamine to n-hexane solvent, stirring to dissolve, adding 1-3 g of 2-(2-naphthyl)acetyl chloride thereto at 18-24° C., reacting at constant temperature for 1-2 hours, raising the temperature to 85-95° C., adding 2-5 g of 2-(2-naphthyl)acetyl chloride, reacting at constant temperature for 2-4 hours, and after the reaction is completed, standing to separate, washing the precipitate with deionized water, filtering and vacuum drying to obtain naphthyl melamine;

[0008] (2) adding 13-15 g of N-vinyl pyrrolidone, 30-33 g of formaldehyde solution, and 0.05-0.07 g of p-diphenol reducing agent to a reactor, introducing nitrogen for 30-45 min to deoxygenate, heating to 88-94° C., and dripping 11-14 g of naphthyl melamine thereinto. After the dripping is complete, heating to 135-145° C. to react for 5-8 h. After the reaction is completed, washing and drying are performed to obtain pyrrolidone-modified naphthyl melamine;

[0009] (3) Add 6-14 g of sodium bisulfite to deionized water, stir and dissolve while heating to 68-78° C., add 8-16 g of epichlorohydrin dropwise thereto, and after the addition is complete, heat to 80-85° C. and react at this temperature for 2-2.5 hours. After the reaction is complete, cool the reaction solution in an ice-water bath, filter the precipitated crystals, and recrystallize to obtain sodium 3-chloro-2-hydroxypropane sulfonate;

[0010] (4) adding 10-14 g of sodium 3-chloro-2-hydroxypropanesulfonate to deionized water, stirring to dissolve, heating to 62-70° C., adding 11-16 g of N,N-dimethylacrylamide and 0.03-0.07 g of a catalyst, heating to 85-95° C. to react for 6-10 h, and after the reaction is completed, washing and drying to obtain sulfobetaine-modified acrylamide;

[0011] (5) Add 12-16 g of acrylamide, 4-6 g of sulfobetaine-modified acrylamide, and 5-8 g of pyrrolidone-modified naphthyl melamine to deionized water, stir and dissolve, adjust the pH to neutral with a sodium hydroxide solution with a mass fraction of 30%-34%, control the temperature at 18-28° C., pass nitrogen for 20-30 min to deoxygenate, add 0.04-0.06 g of an oxidant and 0.02-0.05 g of a reducing agent, raise the temperature to 42-50° C. and react for 7-10 h. After the reaction is completed, a high-temperature resistant fracturing thickener is obtained.

[0012] Preferably, the mass fraction of the formaldehyde solution in step (2) is 39%-43%.

[0013] Preferably, the dripping time of epichlorohydrin in step (3) is controlled to be 1.5-2h.

[0014] Preferably, the catalyst in step (4) is sodium hydroxide.

[0015] Preferably, in step (5), the oxidant is potassium persulfate and the reducing agent is sodium bisulfite.

[0016] (III) Beneficial technical effects

[0017] The invention obtains a thickener for high temperature resistant fracturing by polymerizing acrylamide, sulfobetaine modified acrylamide and pyrrolidone modified naphthyl melamine under the action of an oxidant and a reducing agent.

[0018] The amino group in melamine reacts with 2-(2-naphthyl)acetyl chloride to obtain naphthyl melamine, the secondary amine in naphthyl melamine reacts with N-vinyl pyrrolidone and formaldehyde to obtain pyrrolidone-modified naphthyl melamine, sodium bisulfite reacts with epichlorohydrin to obtain sodium 3-chloro-2-hydroxypropane sulfonate, the chlorine in sodium 3-chloro-2-hydroxypropane sulfonate reacts with the tertiary amine in N,N-dimethylacrylamide to obtain sulfobetaine-modified acrylamide.

[0019] The triazine ring structure and naphthyl group in pyrrolidone-modified naphthyl melamine have high stability, which improves the rigidity of the polyacrylamide molecular chain, enhances the hydrophobic association between molecules, and forms a reversible spatial network structure between molecules. This spatial network structure can remain stable under high salt conditions and is not easily destroyed, thereby improving the high temperature resistance and salt resistance of the thickener. Due to the conjugation effect formed by the two benzene rings in the naphthyl group, the thermal stability of the thickener is further enhanced; by introducing vinyl pyrrolidone, the hydrolysis of the amide group in polyacrylamide can be effectively inhibited, thereby The heat and salt resistance of the thickener is improved; in sulfobetaine-modified acrylamide, the strongly polar sulfonic acid group can complex and adsorb metal cations to improve the salt resistance. The cations can repel each other with the metal cations, thereby keeping the polyacrylamide molecular chain in an active and stretched state in the salt solution. Under high salt conditions, the salt ions weaken and shield the mutual attraction between the anion and cation groups in the sulfobetaine, making the polyacrylamide molecules more stretched, and the viscosity increases or decreases on a macro scale, thereby improving the heat and salt resistance of the thickener. DETAILED DESCRIPTION

[0020] Example 1

[0021] (1) Add 18 g of melamine to n-hexane solvent, stir to dissolve, add 1 g of 2-(2-naphthyl)acetyl chloride at 18° C., react at constant temperature for 1 hour, raise the temperature to 85° C., continue to add 2 g of 2-(2-naphthyl)acetyl chloride, react at constant temperature for 2 hours, and after the reaction is completed, stand to separate, wash the precipitate with deionized water, filter and vacuum dry to obtain naphthyl melamine;

[0022] (2) adding 13 g of N-vinyl pyrrolidone, 30 g of a 39% formaldehyde solution, and 0.05 g of a p-diphenol reducing agent to a reactor, introducing nitrogen for 30 min to deoxygenate, heating to 88° C., and dripping 11 g of naphthyl melamine thereinto. After the dripping is complete, heating to 135° C. to react for 5 h. After the reaction is complete, washing and drying are performed to obtain pyrrolidone-modified naphthyl melamine;

[0023] (3) Add 6 g of sodium bisulfite to deionized water, stir and dissolve while heating, raise the temperature to 68° C., add 8 g of epichlorohydrin dropwise thereto, and control the dropping time to 1.5 h. After the dropping is completed, raise the temperature to 80° C. and react at this temperature for 2 h. After the reaction is completed, cool the reaction solution in an ice water bath, filter the precipitated crystals, and recrystallize to obtain sodium 3-chloro-2-hydroxypropane sulfonate;

[0024] (4) adding 10 g of sodium 3-chloro-2-hydroxypropanesulfonate to deionized water, stirring to dissolve, heating to 62° C., adding 11 g of N,N-dimethylacrylamide and 0.03 g of sodium hydroxide catalyst, heating to 85° C. to react for 6 h, and after the reaction is completed, washing and drying to obtain sulfobetaine-modified acrylamide;

[0025] (5) Add 12 g of acrylamide, 4 g of sulfobetaine-modified acrylamide, and 5 g of pyrrolidone-modified naphthyl melamine to deionized water, stir and dissolve, adjust the pH to neutral with a 30% by mass sodium hydroxide solution, control the temperature at 18° C., pass nitrogen for 20 min to deoxygenate, add 0.04 g of potassium persulfate oxidant and 0.02 g of sodium bisulfite reductant, raise the temperature to 42° C. and react for 7 h. After the reaction is completed, a high-temperature resistant fracturing thickener is obtained.

[0026] Example 2

[0027] (1) Add 24 g of melamine to n-hexane solvent, stir to dissolve, add 3 g of 2-(2-naphthyl)acetyl chloride at 24° C., react at constant temperature for 2 h, raise the temperature to 95° C., continue to add 5 g of 2-(2-naphthyl)acetyl chloride, react at constant temperature for 4 h, after the reaction is completed, stand and separate, wash the precipitate with deionized water, filter and vacuum dry to obtain naphthyl melamine;

[0028] (2) adding 15 g of N-vinyl pyrrolidone, 33 g of a 43% formaldehyde solution, and 0.07 g of a p-diphenol reducing agent to a reactor, introducing nitrogen for 45 min to remove oxygen, heating the reactor to 94° C., and dripping 14 g of naphthyl melamine thereinto. After the dripping is complete, heating the reactor to 145° C. to react for 8 h. After the reaction is complete, washing and drying the reactor to obtain pyrrolidone-modified naphthyl melamine;

[0029] (3) Add 14 g of sodium bisulfite to deionized water, stir and dissolve while heating, raise the temperature to 78° C., add 16 g of epichlorohydrin dropwise thereto, and control the dropping time to be 2 h. After the dropping is completed, raise the temperature to 85° C. and react at this temperature for 2.5 h. After the reaction is completed, cool the reaction solution in an ice water bath, filter the precipitated crystals, and recrystallize to obtain sodium 3-chloro-2-hydroxypropane sulfonate;

[0030] (4) adding 14 g of sodium 3-chloro-2-hydroxypropanesulfonate to deionized water, stirring to dissolve, heating to 70° C., adding 16 g of N,N-dimethylacrylamide and 0.07 g of sodium hydroxide catalyst, heating to 95° C. to react for 10 h, and after the reaction is completed, washing and drying to obtain sulfobetaine-modified acrylamide;

[0031] (5) Add 16 g of acrylamide, 6 g of sulfobetaine-modified acrylamide, and 8 g of pyrrolidone-modified naphthyl melamine to deionized water, stir and dissolve, adjust the pH to neutral with a 34% by mass sodium hydroxide solution, control the temperature at 28°C, pass nitrogen for 30 min to deoxygenate, add 0.06 g of potassium persulfate oxidant and 0.05 g of sodium bisulfite reductant, raise the temperature to 50°C and react for 10 h. After the reaction is completed, a high temperature resistant fracturing thickener is obtained.

[0032] Example 3

[0033] (1) Add 21 g of melamine to n-hexane solvent, stir to dissolve, add 2 g of 2-(2-naphthyl)acetyl chloride at 21° C., react at constant temperature for 1.5 h, raise the temperature to 90° C., continue to add 3.5 g of 2-(2-naphthyl)acetyl chloride, react at constant temperature for 3 h, and after the reaction is completed, stand to separate, wash the precipitate with deionized water, filter and vacuum dry to obtain naphthyl melamine;

[0034] (2) adding 14 g of N-vinyl pyrrolidone, 31.5 g of a 41% formaldehyde solution, and 0.06 g of a p-diphenol reducing agent to a reactor, introducing nitrogen for 38 min to remove oxygen, heating the reactor to 91° C., and dripping 12.5 g of naphthyl melamine thereinto. After the dripping is complete, heating the reactor to 140° C. to react for 6.5 h. After the reaction is complete, washing and drying the reactor to obtain pyrrolidone-modified naphthyl melamine;

[0035] (3) Add 10 g of sodium bisulfite to deionized water, stir and dissolve while heating, raise the temperature to 73° C., add 12 g of epichlorohydrin dropwise thereto, and control the dropping time to 1.8 h. After the dropping is completed, raise the temperature to 82° C. and react at this temperature for 2.3 h. After the reaction is completed, cool the reaction solution in an ice water bath, filter the precipitated crystals, and recrystallize to obtain sodium 3-chloro-2-hydroxypropane sulfonate;

[0036] (4) adding 12 g of sodium 3-chloro-2-hydroxypropanesulfonate to deionized water, stirring to dissolve, heating to 66° C., adding 13.5 g of N,N-dimethylacrylamide and 0.05 g of sodium hydroxide catalyst, heating to 90° C. to react for 8 h, and after the reaction is completed, washing and drying to obtain sulfobetaine-modified acrylamide;

[0037] (5) Add 14 g of acrylamide, 5 g of sulfobetaine-modified acrylamide, and 6.5 g of pyrrolidone-modified naphthyl melamine to deionized water, stir and dissolve, adjust the pH to neutral with a 32% by mass sodium hydroxide solution, control the temperature at 23° C., pass nitrogen for 25 min to deoxygenate, add 0.05 g of potassium persulfate oxidant and 0.03 g of sodium bisulfite reductant, raise the temperature to 46° C. and react for 8.5 h. After the reaction is completed, a high-temperature resistant fracturing thickener is obtained.

[0038] Example 4

[0039] (1) Add 18 g of melamine to n-hexane solvent, stir to dissolve, add 1 g of 2-(2-naphthyl)acetyl chloride at 18° C., react at constant temperature for 1 hour, raise the temperature to 85° C., continue to add 2 g of 2-(2-naphthyl)acetyl chloride, react at constant temperature for 2 hours, and after the reaction is completed, stand to separate, wash the precipitate with deionized water, filter and vacuum dry to obtain naphthyl melamine;

[0040] (2) adding 13 g of N-vinyl pyrrolidone, 30 g of a 39% formaldehyde solution, and 0.05 g of a p-diphenol reducing agent to a reactor, introducing nitrogen for 30 min to deoxygenate, heating to 88° C., and dripping 11 g of naphthyl melamine thereinto. After the dripping is complete, heating to 135° C. to react for 5 h. After the reaction is complete, washing and drying are performed to obtain pyrrolidone-modified naphthyl melamine;

[0041] (3) Add 14 g of sodium bisulfite to deionized water, stir and dissolve while heating, raise the temperature to 78° C., add 16 g of epichlorohydrin dropwise thereto, and control the dropping time to be 2 h. After the dropping is completed, raise the temperature to 85° C. and react at this temperature for 2.5 h. After the reaction is completed, cool the reaction solution in an ice water bath, filter the precipitated crystals, and recrystallize to obtain sodium 3-chloro-2-hydroxypropane sulfonate;

[0042] (4) adding 14 g of sodium 3-chloro-2-hydroxypropanesulfonate to deionized water, stirring to dissolve, heating to 70° C., adding 16 g of N,N-dimethylacrylamide and 0.07 g of sodium hydroxide catalyst, heating to 95° C. to react for 10 h, and after the reaction is completed, washing and drying to obtain sulfobetaine-modified acrylamide;

[0043] (5) Add 14 g of acrylamide, 5 g of sulfobetaine-modified acrylamide, and 6.5 g of pyrrolidone-modified naphthyl melamine to deionized water, stir and dissolve, adjust the pH to neutral with a 32% by mass sodium hydroxide solution, control the temperature at 23° C., pass nitrogen for 25 min to deoxygenate, add 0.05 g of potassium persulfate oxidant and 0.03 g of sodium bisulfite reductant, raise the temperature to 46° C. and react for 8.5 h. After the reaction is completed, a high-temperature resistant fracturing thickener is obtained.

[0044] Example 5

[0045] (1) Add 24 g of melamine to n-hexane solvent, stir to dissolve, add 3 g of 2-(2-naphthyl)acetyl chloride at 24° C., react at constant temperature for 2 h, raise the temperature to 95° C., continue to add 5 g of 2-(2-naphthyl)acetyl chloride, react at constant temperature for 4 h, after the reaction is completed, stand and separate, wash the precipitate with deionized water, filter and vacuum dry to obtain naphthyl melamine;

[0046] (2) adding 15 g of N-vinyl pyrrolidone, 33 g of a 43% formaldehyde solution, and 0.07 g of a p-diphenol reducing agent to a reactor, introducing nitrogen for 45 min to remove oxygen, heating the reactor to 94° C., and dripping 14 g of naphthyl melamine thereinto. After the dripping is complete, heating the reactor to 145° C. to react for 8 h. After the reaction is complete, washing and drying the reactor to obtain pyrrolidone-modified naphthyl melamine;

[0047] (3) Add 10 g of sodium bisulfite to deionized water, stir and dissolve while heating, raise the temperature to 73° C., add 12 g of epichlorohydrin dropwise thereto, and control the dropping time to 1.8 h. After the dropping is completed, raise the temperature to 82° C. and react at this temperature for 2.3 h. After the reaction is completed, cool the reaction solution in an ice water bath, filter the precipitated crystals, and recrystallize to obtain sodium 3-chloro-2-hydroxypropane sulfonate;

[0048] (4) adding 12 g of sodium 3-chloro-2-hydroxypropanesulfonate to deionized water, stirring to dissolve, heating to 66° C., adding 13.5 g of N,N-dimethylacrylamide and 0.05 g of sodium hydroxide catalyst, heating to 90° C. to react for 8 h, and after the reaction is completed, washing and drying to obtain sulfobetaine-modified acrylamide;

[0049] (5) Add 12 g of acrylamide, 4 g of sulfobetaine-modified acrylamide, and 5 g of pyrrolidone-modified naphthyl melamine to deionized water, stir and dissolve, adjust the pH to neutral with a 30% by mass sodium hydroxide solution, control the temperature at 18° C., pass nitrogen for 20 min to deoxygenate, add 0.04 g of potassium persulfate oxidant and 0.02 g of sodium bisulfite reductant, raise the temperature to 42° C. and react for 7 h. After the reaction is completed, a high-temperature resistant fracturing thickener is obtained.

[0050] Comparative Example 1

[0051] The difference between this comparative example and Example 5 is that no sulfobetaine-modified acrylamide is added in step (5).

[0052] Comparative Example 2

[0053] The difference between this comparative example and Example 5 is that pyrrolidone-modified naphthyl melamine is not added in step (5).

[0054] The apparent viscosity of the thickeners in Examples 1-5 and Comparative Examples 1-2 at different temperatures was tested using a rheometer. The mass fraction of the thickener was 1.2%, and the shear rate was 170 s -1 The test results are shown in Table 1.

[0055] Table 1: High temperature resistance test.

[0056]

[0057] It can be seen from Table 1 that, compared with Comparative Examples 1-2, Examples 1-5 of the present invention still have higher apparent viscosity at high temperatures and have better high temperature resistance.

[0058] 39.87 g of NaCl, 1.34 g of KCl, 5.82 g of Na2SO4, 14.47 g of MgCl2·6H2O, and 2.39 g of CaCl2·2H2O were added to 1 L of deionized water, and then diluted to salt water with different mineralization degrees. The thickeners in Examples 1-5 and Comparative Examples 1-2 were dissolved in the salt water to prepare a polymer solution with a mass fraction of 1.2%. The apparent viscosity was tested using a rheometer at 30°C. The test results are shown in Table 2.

[0059] Table 2: Salt resistance test.

[0060]

[0061] As can be seen from Table 2, compared with Comparative Examples 1-2, Examples 1-5 of the present invention still have higher apparent viscosity at high mineralization and better salt resistance.

[0062] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a high temperature resistant fracturing thickener, characterized in that: The method for preparing the high temperature resistant fracturing thickener comprises the following steps: (1) adding 18-24 g of melamine to n-hexane solvent, stirring to dissolve, adding 1-3 g of 2-(2-naphthyl)acetyl chloride thereto at 18-24° C., reacting at constant temperature for 1-2 hours, raising the temperature to 85-95° C., adding 2-5 g of 2-(2-naphthyl)acetyl chloride, reacting at constant temperature for 2-4 hours, and after the reaction is completed, standing to separate, washing the precipitate with deionized water, filtering and vacuum drying to obtain naphthyl melamine; (2) adding 13-15 g of N-vinyl pyrrolidone, 30-33 g of formaldehyde solution, and 0.05-0.07 g of p-diphenol reducing agent to a reactor, introducing nitrogen for 30-45 min to deoxygenate, heating to 88-94° C., and dripping 11-14 g of naphthyl melamine thereinto. After the dripping is complete, heating to 135-145° C. to react for 5-8 h. After the reaction is completed, washing and drying are performed to obtain pyrrolidone-modified naphthyl melamine; (3) Add 6-14 g of sodium bisulfite to deionized water, stir and dissolve while heating to 68-78° C., add 8-16 g of epichlorohydrin dropwise thereto, and after the addition is complete, heat to 80-85° C. and react at this temperature for 2-2.5 hours. After the reaction is complete, cool the reaction solution in an ice-water bath, filter the precipitated crystals, and recrystallize to obtain sodium 3-chloro-2-hydroxypropane sulfonate; (4) adding 10-14 g of sodium 3-chloro-2-hydroxypropanesulfonate to deionized water, stirring to dissolve, heating to 62-70° C., adding 11-16 g of N,N-dimethylacrylamide and 0.03-0.07 g of a catalyst, heating to 85-95° C. to react for 6-10 h, and after the reaction is completed, washing and drying to obtain sulfobetaine-modified acrylamide; (5) Add 12-16 g of acrylamide, 4-6 g of sulfobetaine-modified acrylamide, and 5-8 g of pyrrolidone-modified naphthyl melamine to deionized water, stir and dissolve, adjust the pH to neutral with a sodium hydroxide solution with a mass fraction of 30%-34%, control the temperature at 18-28° C., pass nitrogen for 20-30 min to deoxygenate, add 0.04-0.06 g of an oxidant and 0.02-0.05 g of a reducing agent, raise the temperature to 42-50° C. and react for 7-10 h. After the reaction is completed, a high-temperature resistant thickener for fracturing is obtained.

2. The high temperature resistant fracturing thickener according to claim 1, characterized in that: The mass fraction of the formaldehyde solution in step (2) is 39%-43%.

3. The high temperature resistant fracturing thickener according to claim 1, characterized in that: The dripping time of epichlorohydrin in the step (3) is controlled within 1.5-2 hours.

4. The high temperature resistant fracturing thickener according to claim 1, characterized in that: The catalyst in step (4) is sodium hydroxide.

5. The high temperature resistant fracturing thickener according to claim 1, characterized in that: In the step (5), the oxidizing agent is potassium persulfate and the reducing agent is sodium bisulfite.

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