A temperature- and salt-resistant thickener and its preparation method

Abstract

This invention discloses a temperature- and salt-resistant thickener and its preparation method, relating to the field of fracturing fluid technology. The preparation method of this temperature- and salt-resistant thickener includes the following steps: a first monomer and diethanolamine undergo an epoxy ring-opening reaction; after the reaction, the mixture is separated and purified to obtain an intermediate; the intermediate is taken, and a quaternizing agent is added to undergo a quaternization reaction, followed by separation and purification to obtain the active monomer; the first monomer is one of allyl alcohol glycidyl ether, acrylate glycidyl ether, and methacrylate glycidyl ether, and the quaternizing agent is one of a halocarboxylate or a halosulfonate; acrylamide, the active monomer, and an unsaturated phosphate ester are taken and dissolved, and then subjected to free radical polymerization under the action of an initiator to obtain the final product. The thickener of this invention exhibits good temperature and salt resistance, capable of withstanding brine with a salinity of 120,000 mg / L and high temperatures of 150°C.

Description

Technical Field

[0001] This invention relates to the field of fracturing fluid technology, specifically to a temperature- and salt-resistant thickener and its preparation method. Background Technology

[0002] With the deepening of oil and gas field development both domestically and internationally, high-temperature and high-salinity reservoirs have gradually become the focus of development. For example, existing oil and gas fields have a relatively large number of reservoirs with salinity exceeding 10,000 mg / L and temperatures exceeding 120℃. Large domestic oil and gas fields such as Shengli Oilfield and Karamay Oilfield both contain numerous high-temperature and high-salinity oil reservoirs. Water-based drilling fluids are crucial for oil and gas reservoir development. They are typically composed of water, thickeners, clay, and additives. Among these, the thickener is the most important component of water-based drilling fluids, affecting various functions such as rheology, lithology, and wellbore stability.

[0003] Existing tackifiers are mainly divided into natural gums, cellulose derivatives, and synthetic polymers. Natural gums are mainly xanthan gum and guar gum, while cellulose derivatives are usually carboxymethyl cellulose, which have the advantage of good environmental performance. Synthetic polymers are mainly polyacrylamide polymers. Due to the designability of their molecular structure, they usually have certain temperature resistance. However, their disadvantage is poor salt resistance. In the existing technology, there are also technologies that modify polyacrylamide by adding a variety of monomers. However, the large number of monomers not only leads to increased costs but also makes the production process relatively complex. Summary of the Invention

[0004] In view of the above technical problems, the purpose of this invention is to provide a temperature- and salt-resistant thickener and its preparation method, addressing the deficiencies of the prior art.

[0005] This invention employs the following technical solution: a method for preparing a temperature- and salt-resistant tackifier, comprising the following steps: taking a first monomer and diethanolamine in a molar ratio of 1:1 to 1.1 to undergo an epoxy ring-opening reaction; after the reaction, separating and purifying to obtain an intermediate; taking the intermediate, adding a quaternizing agent to undergo a quaternization reaction, and then separating and purifying to obtain the active monomer; the first monomer is one of allyl alcohol glycidyl ether, glycidyl acrylate, and glycidyl methacrylate, and the quaternizing agent is one of a halocarboxylate or a halosulfonate;

[0006] Take 20-40 parts by weight of acrylamide, 1-5 parts of active monomer, and 2-5 parts of unsaturated phosphate ester and dissolve them. Then, carry out free radical polymerization under the action of an initiator to obtain the product.

[0007] In the above process, the synthesized active monomer contains a large number of active groups: three hydroxyl groups, one quaternary ammonium group, and one anionic group. The quaternary ammonium group and the anionic group not only possess strong hydrophilic properties, but their betaine structure also significantly increases the polymer's temperature and salt resistance, and to some extent enhances its shear resistance. The multiple hydroxyl groups have strong hydrophilicity and can form hydrogen bonds with water and other monomers to enhance the thickening properties of the tackifier. Furthermore, the multiple hydroxyl groups effectively mitigate the problem of slow polymer water solubility caused by the betaine structure. In this process, the amount of quaternizing agent added is similar to that in conventional quaternization reactions, with a molar ratio of 1:1 to 1.2 to the intermediate, and a slight excess of the quaternizing agent.

[0008] One embodiment of the present invention is that the halocarboxylic acid is one of chloroacetic acid, 2-chloropropionic acid, and 3-chloropropionic acid, and the halosulfonic acid is one of sodium 2-chloroethylsulfonate, sodium 3-bromopropylsulfonate, and sodium 3-chloro-2-hydroxypropylsulfonate. These belong to the category of small molecule halocarboxylic acids and halosulfonic acids commonly found in the art.

[0009] Preferably, the halosulfonic acid is sodium 3-chloro-2-hydroxypropyl sulfonate. Compared with other halosulfonic acids, sodium 3-chloro-2-hydroxypropyl sulfonate contains an additional hydroxyl group. When it is grafted onto the active monomer, there is also a hydrophilic hydroxyl group between the quaternary ammonium and the sulfonic acid. Therefore, it can alleviate the problem of slow dissolution rate of conventional betaine due to intramolecular / intermolecular forces. At the same time, the temperature and salt resistance of the polymer is further enhanced.

[0010] In one embodiment of the present invention, the unsaturated phosphate ester is diethyl allylphosphonate. The added unsaturated phosphate ester not only increases the polymer's salt resistance but also, to some extent, increases its temperature resistance.

[0011] One embodiment of the present invention comprises the following steps for preparing the intermediate: dissolving the diethanolamine in water, adding the first monomer dropwise to the diethanolamine solution at 50-70°C under an inert atmosphere, reacting for 1-3 hours after the addition is complete, and removing low-boiling components by vacuum distillation after the reaction is complete. In this process, the secondary amine group in the diethanolamine undergoes a ring-opening reaction with the glycidyl group in the first monomer, and the reaction process and conditions are relatively conventional. In the separation and purification step, most of the solvent and reactants can be removed by vacuum distillation alone, and the final product contains a tertiary amine group, providing a raw material for the subsequent quaternization reaction.

[0012] One embodiment of the present invention is that the preparation method of the active monomer includes the following steps: dissolving the intermediate in water, adding the quaternizing agent to the aqueous solution of the intermediate under alkaline conditions and a temperature of 60~90℃, and continuing the reaction for 8~40h. After the reaction is completed, removing the low-boiling substances by vacuum distillation, adding ethanol, dissolving it completely, removing the solid phase, and then removing the ethanol to obtain the product.

[0013] In this process, the tertiary amine group obtained in the previous step can react well with the quaternizing agent to obtain the quaternary ammonium salt. However, it should be noted that due to the relatively large steric hindrance of the tertiary amine and the fact that the quaternizing agent is not a conventional reagent with a shorter chain length such as bromoethane or iodomethane, in the actual reaction process, it is necessary to increase the temperature and carry out the reaction for a longer time depending on the selected quaternizing agent.

[0014] In the separation and purification steps of the product, the initial vacuum distillation is mainly to remove the solvent from the product; subsequently, ethanol is added to remove the inorganic salts from the product. The amount of ethanol added varies depending on the raw materials used. The amount of ethanol to be added can be determined as follows: First, add an equal mass of ethanol to the product, stir well, then add another equal mass of ethanol and continue stirring. Observe the amount of insoluble matter in the solution. When the change in insoluble matter in the water is small or basically unchanged after two consecutive additions of ethanol, it indicates that almost all of the product has dissolved. According to the inventor's experiments, the amount of ethanol added is usually 2 to 5 times the mass of the product. In fact, after removing ethanol, further purification can be carried out, such as recrystallizing the product in acetone and drying the precipitate; however, since the residual material does not affect the final product, the subsequent recrystallization operation may not be necessary.

[0015] In one embodiment of the present invention, the initiator in the free radical polymerization is a redox initiator, the amount of initiator added is 0.05~0.5wt% of the total mass of the reactants, the reaction temperature is 20~50℃, and the solvent is a mixture of a small molecule alcohol and water with a volume ratio of 0.5~2:10, wherein the small molecule alcohol is methanol or ethanol. The redox initiator is typically a mixture of potassium persulfate and sodium bisulfite with a mass ratio of 1:1, which has a relatively low initiation temperature and is relatively mild. In fact, persulfate initiators (such as potassium persulfate) or water-soluble azo initiators (such as azobisisobutylamidine hydrochloride) can also be used.

[0016] One embodiment of the present invention comprises 28-32 parts acrylamide, 3-4 parts reactive monomer, and 3.5-4.5 parts unsaturated phosphate ester in the free radical polymerization. Under this combination of conditions, the effect is even better.

[0017] One embodiment of the present invention is that the free radical polymerization includes 24-26 parts of acrylamide, 3.5-4.5 parts of active monomer, and 2.5-3.5 parts of unsaturated phosphate ester.

[0018] Another object of the present invention is to disclose a temperature- and salt-resistant thickener, which is prepared by any of the methods described above.

[0019] The beneficial effects of this invention are:

[0020] The tackifier of the present invention has good temperature and salt resistance, and can withstand salt water with a mineralization of 120,000 mg / L and a high temperature of 150°C. At the same time, the tackifier is a terpolymer with fewer monomer types and a relatively simple preparation method. Attached Figure Description

[0021] Figure 1 The graph shows the viscosity test results. Detailed Implementation

[0022] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail with reference to the embodiments, but this should not be construed as limiting the scope of implementation of the present invention.

[0023] Unless otherwise specified, the operations described in the following embodiments are conventional operations in the art.

[0024] Unless otherwise specified, the raw materials used in the following embodiments are all conventional commercial products in the art.

[0025] In the following embodiments, unless otherwise specified, the number of parts refers to parts by weight.

[0026] Example 1: 11 parts of diethanolamine were added to water and dissolved. After purging with nitrogen for 30 minutes, 11.4 parts of allyl alcohol glycidyl ether were added dropwise at 60°C with continuous stirring. After the addition was complete, the reaction continued for 2 hours. After the reaction was completed, the low-boiling substances were removed by vacuum distillation to obtain the intermediate. 11 parts of the intermediate were dissolved in water, and the pH was adjusted to 9. At the same time, 10.6 parts of sodium 3-chloro-2-hydroxypropyl sulfonate were dissolved in water and the temperature was raised to 90°C. Then, the sodium 3-chloro-2-hydroxypropyl sulfonate solution was added dropwise to the intermediate solution. The reaction was carried out for 24 hours with continuous stirring. After the reaction was completed, the low-boiling substances were removed by vacuum distillation. Then, 60 parts of ethanol were added and stirred to dissolve the solution. After filtering out the solid phase, the liquid phase was distilled under vacuum to obtain the active monomer.

[0027] Take 30 parts of acrylamide, 3.5 parts of active monomer, and 4 parts of diethyl allylphosphonate and add them to a mixed solution of ethanol and water with a volume ratio of 1:10 and dissolve them. Under the conditions of 30℃ and deoxygenation, add 0.0365 parts of potassium persulfate / sodium bisulfite initiator with a mass ratio of 1:1 and continue the reaction for 1.5 hours. After the reaction is completed, spray dry to obtain the product.

[0028] Example 2: 11 parts of diethanolamine were added to water and dissolved. After purging with nitrogen for 30 minutes, 14.2 parts of glycidyl methacrylate were added dropwise at 55°C with continuous stirring. After the addition was complete, the reaction continued for 1.5 hours. After the reaction was completed, the low-boiling substances were removed by vacuum distillation to obtain the intermediate. 12.35 parts of the intermediate were added to water, sodium hydroxide solution was added and the pH was adjusted to 9.5. At the same time, 8.8 parts of sodium 2-chloroethylsulfonate were added to the above solution. The temperature was raised to 85°C and the reaction continued for 30 hours. After the reaction was completed, the low-boiling substances were removed by vacuum distillation. Then 55 parts of ethanol were added and dissolved completely. The solid phase was filtered off, and the liquid phase was subjected to vacuum distillation to obtain the active monomer.

[0029] Take 25 parts of acrylamide, 3 parts of active monomer, and 3 parts of diethyl allylphosphonate and add them to a mixed solution of ethanol and water with a volume ratio of 1:10 and dissolve them. Under the conditions of 35℃ and deoxygenation, add 0.0365 parts of potassium persulfate / sodium bisulfite initiator with a mass ratio of 1:1 and continue the reaction for 1.5 hours. After the reaction is completed, spray dry to obtain the product.

[0030] Example 3: 11 parts of diethanolamine were added to water and dissolved. After purging with nitrogen for 30 minutes, 11.4 parts of allyl alcohol glycidyl ether were added dropwise at 60°C with continuous stirring. After the addition was complete, the reaction continued for 2 hours. After the reaction was completed, the low-boiling substances were removed by vacuum distillation to obtain the intermediate. 11 parts of the intermediate were taken and dissolved in water, and the pH was adjusted to 9. At the same time, 4.8 parts of chloroacetic acid were taken and dissolved in water, and the temperature was raised to 90°C. Then, chloroacetic acid was added dropwise to the intermediate solution. During the addition, sodium hydroxide solution was added dropwise to maintain the pH at around 9. The reaction was carried out for 24 hours with continuous stirring. After the reaction was completed, the low-boiling substances were removed by vacuum distillation. Then, 60 parts of ethanol were added and stirred to dissolve the residue. After filtering out the solid phase, the liquid phase was distilled under vacuum to obtain the active monomer.

[0031] Take 30 parts of acrylamide, 3.5 parts of active monomer, and 4 parts of diethyl allylphosphonate and add them to a mixed solution of ethanol and water with a volume ratio of 1:10 and dissolve them. Under the conditions of 30℃ and deoxygenation, add 0.0365 parts of potassium persulfate / sodium bisulfite initiator with a mass ratio of 1:1 and continue the reaction for 1.5 hours. After the reaction is completed, spray dry to obtain the product.

[0032] Example 4: 11 parts of diethanolamine were added to water and dissolved. After purging with nitrogen for 30 minutes, 11.4 parts of allyl alcohol glycidyl ether were added dropwise at 60°C with continuous stirring. After the addition was complete, the reaction continued for 2 hours. After the reaction was completed, the low-boiling substances were removed by vacuum distillation to obtain the intermediate. 11 parts of the intermediate were dissolved in water and the pH was adjusted to 9. At the same time, 10.6 parts of sodium 3-chloro-2-hydroxypropyl sulfonate were dissolved in water and the temperature was raised to 90°C. Then, the sodium 3-chloro-2-hydroxypropyl sulfonate solution was added dropwise to the intermediate solution and the reaction was carried out for 24 hours with continuous stirring. After the reaction was completed, the low-boiling substances were removed by vacuum distillation. Then, 60 parts of ethanol were added and stirred to dissolve the solution. After filtering out the solid phase, the liquid phase was distilled under vacuum to obtain the active monomer.

[0033] Take 35 parts of acrylamide, 4.5 parts of active monomer, and 2.8 parts of diethyl allylphosphonate and add them to a mixed solution of ethanol and water with a volume ratio of 1:10 and dissolve them. Under the conditions of 30℃ and deoxygenation, add 0.0365 parts of potassium persulfate / sodium bisulfite initiator with a mass ratio of 1:1 and continue the reaction for 1.5 hours. After the reaction is completed, spray dry to obtain the product.

[0034] Comparative Example 1 differs from Example 1 in that it does not contain diethyl allylphosphonate, while all other aspects are the same.

[0035] Comparative Example 2 differs from Example 1 in that, in the preparation of the active monomer, 8.5 parts of dimethylaminopropylacrylamide were used instead of 11 parts of the intermediate, while the rest remained the same.

[0036] To further illustrate the performance of the thickener prepared by this invention, specific test results are given below.

[0037] 1. Viscosity test

[0038] The thickeners prepared in Examples 1-4 and Comparative Example 1 were mixed with brine of different mineralization degrees to prepare solutions with a concentration of 0.3 wt%. Their viscosity under room temperature conditions was measured, and the final results are as follows: Figure 1 As shown in the figure. The salt in the brine is composed of sodium chloride and calcium chloride in a mass ratio of 20:1.

[0039] from Figure 1 It can be seen that the viscosity of the thickener prepared in the embodiments of the present invention increases with the increase of mineralization when the mineralization is low, and decreases slightly when the viscosity increases to a certain extent.

[0040] 2. Temperature resistance test

[0041] The thickeners prepared in Examples 1-4 and Comparative Example 1 were added to brine with a mineralization of 80,000 mg / L to prepare a 0.3 wt% solution. The viscosity of the solution was measured under different temperature conditions, and the final results are shown in Table 1. The brine consisted of sodium chloride and calcium chloride in a mass ratio of 20:1.

[0042] The thickeners prepared in Examples 1-4 and Comparative Example 1 were added to saline solution with a mineralization of 80,000 mg / L to prepare a solution with a concentration of 0.3 wt%. The solution was kept at 150°C for a period of time, and its viscosity was measured every day. The time when the viscosity was less than 50 mPa·s was recorded. The solution was cooled to room temperature before measurement to characterize its temperature resistance stability. The final results are shown in Table 2.

[0043] Table 1 Viscosity test results under different temperature conditions

[0044]

[0045] Table 2 Temperature stability test table

[0046]

[0047] As shown in Tables 1 and 2, the thickener prepared in the embodiments of the present invention has good temperature and salt resistance and can withstand high temperatures. Furthermore, compared to the conventional betaine in Comparative Example 2, the active intermediate of the present invention exhibits better performance.

[0048] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a temperature- and salt-resistant thickener, characterized in that, Includes the following steps: The first monomer and diethanolamine were reacted in a molar ratio of 1:1 to 1.1 to undergo an epoxy ring-opening reaction. After the reaction was completed, the intermediate was separated and purified. The intermediate was then subjected to a quaternization reaction with a quaternizing agent, followed by separation and purification to obtain the active monomer. The first monomer was one of allyl alcohol glycidyl ether, glycidyl acrylate, and glycidyl methacrylate. The quaternizing agent was one of a halocarboxylate or a halosulfonate. Take 20-40 parts by weight of acrylamide, 1-5 parts of active monomer, and 2-5 parts of unsaturated phosphate ester and dissolve them. Then, carry out free radical polymerization under the action of an initiator to obtain the product.

2. The method according to claim 1, characterized in that, The halocarboxylic acid is one of chloroacetic acid, 2-chloropropionic acid, and 3-chloropropionic acid, and the halosulfonic acid is one of sodium 2-chloroethylsulfonate, sodium 3-bromopropylsulfonate, and sodium 3-chloro-2-hydroxypropylsulfonate.

3. The method according to claim 2, characterized in that, The halosulfonic acid is sodium 3-chloro-2-hydroxypropyl sulfonate.

4. The method according to claim 1, characterized in that, The unsaturated phosphate ester is diethyl allylphosphonate.

5. The method according to claim 1, characterized in that, The preparation method of the intermediate includes the following steps: dissolving diethanolamine in water, adding the first monomer dropwise to the diethanolamine solution at 50~70℃ and under an inert atmosphere, reacting for 1~3 hours after the addition is complete, and removing low-boiling substances by vacuum distillation after the reaction is complete to obtain the intermediate.

6. The method according to claim 1, characterized in that, The preparation method of the active monomer includes the following steps: dissolving the intermediate in water, adding the quaternizing agent to the aqueous solution of the intermediate under alkaline conditions and a temperature of 60~90℃, and continuing the reaction for 8~40h. After the reaction is completed, removing the low-boiling substances by vacuum distillation, adding ethanol, dissolving it completely, removing the solid phase, and then removing the ethanol to obtain the product.

7. The method according to claim 1, characterized in that, In the free radical polymerization, the initiator is a redox initiator, the amount of initiator added is 0.05~0.5wt% of the total mass of the reactants, the reaction temperature is 20~50℃, and the solvent is a mixture of small molecule alcohol and water with a volume ratio of 0.5~2:10, wherein the small molecule alcohol is methanol or ethanol.

8. The method according to claim 1, characterized in that, The free radical polymerization includes 28-32 parts acrylamide, 3-4 parts active monomer, and 3.5-4.5 parts unsaturated phosphate ester.

9. The method according to claim 1, characterized in that, The free radical polymerization includes 24-26 parts acrylamide, 3.5-4.5 parts active monomer, and 2.5-3.5 parts unsaturated phosphate ester.

10. A temperature- and salt-resistant thickener, prepared by the method described in any one of claims 1-9.

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