Terpolymer, terpolymer scale inhibitor and preparation method and application thereof

Abstract

The present invention discloses a ternary copolymer, a ternary copolymer scale inhibitor, and a preparation method and application thereof, and belongs to the field of water treatment technology. The present invention proposes a ternary copolymer, and its structural formula is: wherein m, n, and p are any integers from 1 to 10, respectively. In addition, the present invention also proposes a preparation method of the above-mentioned ternary copolymer, comprising the following steps: S1, mixing itaconic acid and water, then heating to 60-70°C and adding aconitic acid; then heating to 80-90°C, dripping 4-acryloylmorpholine aqueous solution and initiator to obtain a mixture; S2, continuing to react the mixture at 80-90°C to obtain the ternary copolymer. In addition, the present invention also proposes a ternary copolymer scale inhibitor, including the above-mentioned ternary copolymer or the ternary copolymer obtained by the above-mentioned preparation method. The raw materials of the ternary copolymer obtained by the present invention are easy to obtain, the preparation method is simple, the cost is low, and it has excellent scale inhibition performance.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a terpolymer, a terpolymer scale inhibitor, and a preparation method and application thereof. Background Art

[0002] In order to maintain formation pressure and improve oilfield production efficiency, water injection is required. In order to save water resources, oilfield produced water is usually used, which has complex components and contains scale-forming ions such as calcium, magnesium, barium, and strontium. These inorganic salts precipitate and adhere to the inside of pipelines and mechanical equipment, causing pipeline blockage, equipment damage and other problems. In particular, when injected into the formation, it causes formation scaling and blockage, and production decreases, which directly affects the benefits of oilfield development.

[0003] The main method to solve the scaling problem in the oil field production process is to add chemical agents such as scale inhibitors. Commercial scale inhibitors for carbonate and sulfate scale are usually based on phosphorus-based formulas. Excessive discharge of phosphorus-containing substances will cause eutrophication of water bodies and bring harm to the environment. It is very important to develop an efficient and green scale inhibitor. How to obtain compounds with excellent scale inhibition performance is a technical problem that the existing technology needs to solve. Summary of the invention

[0004] The purpose of the present invention is to overcome the above technical deficiencies, provide a terpolymer, a terpolymer scale inhibitor and a preparation method and application thereof, and solve the technical problem of how to obtain a compound with excellent scale inhibition performance in the prior art.

[0005] In order to achieve the above technical purpose, the technical solution of the present invention provides a terpolymer, whose structural formula is:

[0006] In the formula, m, n, and p are any integers from 1 to 10 respectively.

[0007] In addition, the present invention also provides a method for preparing the above terpolymer, comprising the following steps:

[0008] S1, mixing itaconic acid and water, then heating to 60-70°C and adding aconitic acid; then heating to 80-90°C, dropwise adding 4-acryloylmorpholine aqueous solution and initiator to obtain a mixture;

[0009] S2. Continue to react the mixture at 80-90° C. to obtain the terpolymer.

[0010] In any embodiment, in step S1, the molar ratio of the itaconic acid to the aconitic acid is (1-2):1.

[0011] In any embodiment, in step S1, the molar ratio of itaconic acid to 4-acryloylmorpholine is (1-3):1.

[0012] In any embodiment, in step S1, the initiator is ammonium persulfate.

[0013] In any embodiment, in step S1, the added amount of the initiator is 8%-15% of the total mass of the itaconic acid, the aconitic acid and the 4-acryloylmorpholine.

[0014] In any embodiment, in step S1, the time for dripping the 4-acryloylmorpholine aqueous solution and the time for dripping the initiator are 1-2 hours respectively.

[0015] In any embodiment, in step S2, the heat preservation reaction time at 80-90° C. is 0.5-2 h.

[0016] In any embodiment, in step S1, the mass of water mixed with the itaconic acid is 1.5-2 times the total mass of itaconic acid and aconitic acid; and / or, the mass of water in the 4-acryloylmorpholine aqueous solution is 1.2-1.6 times the mass of 4-acryloylmorpholine.

[0017] In addition, the present invention also provides a terpolymer scale inhibitor, comprising the above terpolymer or the terpolymer prepared by the above preparation method.

[0018] The present invention also proposes an application of the terpolymer scale inhibitor in an oilfield water treatment system.

[0019] Compared with the prior art, the beneficial effects of the present invention include: the present invention uses itaconic acid and aconitic acid as polymerization monomers, so that the polymer molecules have a large number of carboxylic acid groups, and at the same time, the introduction of 4-acryloylmorpholine enhances the stability and durability of the polymer molecules, and the morpholine part makes the molecules hydrophilic. The monomer raw materials used in the present invention do not contain phosphorus groups, and are non-toxic and harmless to the environment, meeting the requirements of green scale inhibitor production raw materials, production methods and production reactions, and the obtained terpolymer has excellent scale inhibition performance. In addition, the scale inhibitor raw materials of the present invention are easy to obtain, safe and environmentally friendly, simple to prepare and operate, low in cost, and easy to be industrialized and applied. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the infrared spectrum of the terpolymer scale inhibitor prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0021] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0022] If there is no special explanation, the "include" and "comprising" mentioned in this application represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0023] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0024] This specific embodiment provides a terpolymer, the structural formula of which is:

[0025]

[0026] In the formula, m, n, and p are any integers from 1 to 10 respectively.

[0027] This specific embodiment also proposes a method for preparing the above terpolymer, comprising the following steps:

[0028] S1, itaconic acid and water are mixed, then the temperature is raised to 60-70°C and aconitic acid is added; then the temperature is raised to 80-90°C, 4-acryloylmorpholine aqueous solution and initiator are added dropwise to obtain a mixture, and the addition is completed in 1-2 hours; the molar ratio of the itaconic acid to the aconitic acid is (1-2):1; the molar ratio of the itaconic acid to the 4-acryloylmorpholine is (1-3):1; the initiator is ammonium persulfate, and the added amount of the initiator is 8%-15% of the total mass of the itaconic acid, the aconitic acid and the 4-acryloylmorpholine; the mass of the water mixed with the itaconic acid is 1.5-2 times the total mass of the itaconic acid and the aconitic acid; the mass of the water in the 4-acryloylmorpholine aqueous solution is 1.2-1.6 times the mass of the 4-acryloylmorpholine;

[0029] S2, the mixture is kept warm for reaction at 80-90°C for 0.5-2h to obtain the terpolymer.

[0030] The present invention adopts an ammonium persulfate redox initiator system and obtains a phosphorus-free terpolymer scale inhibitor by free radical copolymerization in aqueous solution. The reaction mechanism involved is:

[0031] During the reaction, the carbon-carbon double bonds of itaconic acid, aconitic acid and 4-acryloylmorpholine are broken, and then chain polymerization occurs. Ammonium persulfate acts as an initiator and becomes an active center, which undergoes an addition reaction with the monomer. The reaction formula is as follows:

[0032]

[0033] This specific embodiment also proposes a terpolymer scale inhibitor, including the above terpolymer or the terpolymer prepared by the above preparation method. The scale inhibitor proposed by the present invention can be only the terpolymer proposed by the present invention, or it can be a composite scale inhibitor in which the terpolymer proposed by the present invention is used in combination with other compounds having scale inhibition performance.

[0034] This specific implementation also proposes an application of the terpolymer scale inhibitor in an oilfield water treatment system.

[0035] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] In the present invention, reference is made to “some embodiments”, “this embodiment”, examples, etc., which describe a subset of all possible embodiments, but it can be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0037] If similar descriptions of "first / second" appear in the application documents, the following instructions are added. In the following description, the terms "first\second\third" involved are merely used to distinguish similar objects and do not represent a specific ordering of the objects. It can be understood that "first\second\third" can be interchanged in a specific order or sequence where permitted, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein.

[0038] In this embodiment, the term "and / or" is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, object A and / or object B may represent three situations: object A exists alone, object A and object B exist at the same time, and object B exists alone.

[0039] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0040] Example 1

[0041] This embodiment provides a phosphorus-free terpolymer scale inhibitor, which is prepared by the following steps:

[0042] S1. Add itaconic acid and a certain amount of deionized water into a three-necked flask equipped with a reflux condenser, a thermometer and a stirring device, stir at a uniform speed until dissolved at 65°C, then add aconitic acid and stir to dissolve; the molar ratio of itaconic acid to aconitic acid is 1:1, and the mass of deionized water added is 1.6 times the total mass of itaconic acid and aconitic acid; heat the water bath to 80°C, uniformly add dropwise 4-acryloylmorpholine aqueous solution, the molar ratio of itaconic acid to 4-acryloylmorpholine is 1:1, the deionized water in the 4-acryloylmorpholine aqueous solution is 1.5 times the mass of 4-acryloylmorpholine, and the dropping time is 2h; at the same time, uniformly add dropwise ammonium persulfate initiator equivalent to 10% of the total mass of itaconic acid, aconitic acid and 4-acryloylmorpholine, and the dropping time is 2h;

[0043] S2. After the dropwise addition is completed, the water bath is heated to 90°C and the reaction is carried out for 45 minutes. After the reaction is completed, the solution is cooled to room temperature to obtain a reaction product. The product is precipitated with anhydrous ethanol to obtain a solid, which is filtered, washed, and vacuum dried to obtain a purified terpolymer scale inhibitor.

[0044] Example 2

[0045] This embodiment provides a phosphorus-free terpolymer scale inhibitor, which is prepared by the following steps:

[0046] S1. Add itaconic acid and a certain amount of deionized water into a three-necked flask equipped with a reflux condenser, a thermometer and a stirring device, stir at a uniform speed at 65°C until dissolved, then add aconitic acid and stir to dissolve; the molar ratio of itaconic acid to aconitic acid is 3:2, and the mass of deionized water added is 1.6 times the total mass of itaconic acid and aconitic acid; heat the water bath to 85°C, uniformly add 4-acryloylmorpholine aqueous solution dropwise, the molar ratio of itaconic acid to 4-acryloylmorpholine is 3:1, the deionized water in the 4-acryloylmorpholine aqueous solution is 1.5 times the mass of 4-acryloylmorpholine, and the dropping time is 1h; at the same time, uniformly add ammonium persulfate initiator equivalent to 15% of the total mass of itaconic acid, aconitic acid and 4-acryloylmorpholine, and the dropping time is 1.5h;

[0047] S2. After the addition is completed, the water bath temperature is maintained at 85°C, and the reaction is carried out for 2 hours. After the reaction is completed, the solution is cooled to room temperature to obtain a reaction product solution. The product is precipitated into a solid by anhydrous ethanol, and the purified polymer scale inhibitor is obtained by filtration, washing, and vacuum drying.

[0048] Figure 1 This is the infrared spectrum of the scale inhibitor prepared in this example. Figure 1 Found 3436.7cm -1 、1724.2cm -1 、1444.6cm -1 、1196.5cm -1 、1104.2cm -1 、615.7cm -1 The characteristic absorption peaks are 1724.2cm -1 and 615.7cm -1 The vibration is caused by the stretching vibration peaks of C=O and -COOH. The characteristic absorption peak of carboxyl is at 3436.7cm -1 , 1444.6cm -1 It is caused by the stretching vibration of -COO- in the carboxylic acid group. 1196.5cm -1 and 1104.2cm -1 They are the stretching vibration peaks of CN and CN in the morpholine group. At the same time, no 1620-1640cm -1 The C=C absorption peak shows that the monomers have been copolymerized, indicating that the target product terpolymer has been obtained.

[0049] Example 3

[0050] This embodiment provides a phosphorus-free terpolymer scale inhibitor, which is prepared by the following steps:

[0051] S1. Add itaconic acid and a certain amount of deionized water to a three-necked flask equipped with a reflux condenser, a thermometer and a stirring device, stir at a uniform speed at 65°C until dissolved, then add aconitic acid and stir to dissolve. The molar ratio of itaconic acid to aconitic acid is 1:1, and the mass of deionized water added is 1.6 times the total mass of itaconic acid and aconitic acid; heat to 85°C in a water bath, uniformly add 4-acryloylmorpholine aqueous solution, the molar ratio of itaconic acid to 4-acryloylmorpholine is 2:1, the deionized water in the 4-acryloylmorpholine aqueous solution is 1.5 times the mass of 4-acryloylmorpholine, and the addition time is 1.5h; at the same time, uniformly add ammonium persulfate initiator equivalent to 15% of the total mass of itaconic acid, aconitic acid and 4-acryloylmorpholine, and the addition time is 1.5h;

[0052] S2. After the addition is completed, the water bath temperature is maintained at 85°C, and the reaction is carried out for 1.5 hours. After the reaction is completed, the solution is cooled to room temperature to obtain a reaction product. The product is precipitated into a solid by anhydrous ethanol, and the purified polymer scale inhibitor is obtained by filtration, washing, and vacuum drying.

[0053] Example 4

[0054] This embodiment provides a phosphorus-free terpolymer scale inhibitor, which is prepared by the following steps:

[0055] S1. In a three-necked flask equipped with a reflux condenser, a thermometer and a stirring device, add itaconic acid and a certain amount of deionized water, stir at a uniform speed at 65°C until dissolved, then add aconitic acid and stir to dissolve; the molar ratio of itaconic acid to aconitic acid is 2:1, and the mass of deionized water added to the 4-acryloylmorpholine aqueous solution is 1.6 times the total mass of itaconic acid and aconitic acid; heat the water bath to 85°C, uniformly add dropwise the 4-acryloylmorpholine aqueous solution, the molar ratio of itaconic acid to 4-acryloylmorpholine is 2:1, the deionized water is 1.5 times the mass of 4-acryloylmorpholine, and the dropping time is 2h; at the same time, uniformly add dropwise ammonium persulfate initiator equivalent to 15% of the total mass of itaconic acid, aconitic acid and 4-acryloylmorpholine, and the dropping time is 1.5h;

[0056] S2. After the dropwise addition is completed, the water bath temperature is maintained at 85°C, and the reaction is carried out for 1.5 hours. After the reaction is completed, the solution is cooled to room temperature to obtain a reaction product solution; the product is precipitated into a solid by anhydrous ethanol, and the purified polymer scale inhibitor is obtained by filtration, washing, and vacuum drying.

[0057] Comparative Example 1

[0058] The difference between this comparative example and Example 2 is that 4-acryloylmorpholine is not added, and the amount of 4-acryloylmorpholine added is replaced by itaconic acid, as follows:

[0059] This comparative example proposes a scale inhibitor, which is prepared by the following steps:

[0060] S1. Add itaconic acid and a certain amount of deionized water into a three-necked flask equipped with a reflux condenser, a thermometer and a stirring device, stir at a uniform speed at 65°C until dissolved, then add aconitic acid and stir to dissolve; the molar ratio of itaconic acid to aconitic acid is 3:2, and the mass of deionized water added is 1.6 times the total mass of itaconic acid and aconitic acid; heat the water bath to 85°C, add itaconic acid in an amount equivalent to 4-acryloylmorpholine in Example 2, and at the same time, uniformly dropwise add ammonium persulfate initiator equivalent to 15% of the total mass of itaconic acid and aconitic acid, and the dropping time is 1.5h;

[0061] S2. After the addition is completed, the water bath temperature is maintained at 85°C, and the reaction is carried out for 2 hours. After the reaction is completed, the solution is cooled to room temperature to obtain a reaction product. The product is precipitated into a solid by anhydrous ethanol, and the purified scale inhibitor is obtained by filtration, washing, and vacuum drying.

[0062] Comparative Example 2

[0063] The difference between this comparative example and Example 2 is that itaconic acid is not added, and the amount of itaconic acid added is replaced by aconitic acid, as follows:

[0064] This comparative example proposes a scale inhibitor, which is prepared by the following steps:

[0065] S1. In a three-necked flask equipped with a reflux condenser, a thermometer and a stirring device, add aconitic acid and a certain amount of deionized water in an amount equal to that of itaconic acid in Example 2, stir at a uniform speed at 65° C. until dissolved, then add aconitic acid and stir to dissolve, the mass of deionized water added is 1.6 times the total mass of aconitic acid; heat in a water bath to 85° C., uniformly drip the 4-acryloylmorpholine aqueous solution in the amount of Example 2, the deionized water in the 4-acryloylmorpholine aqueous solution is 1.5 times the mass of 4-acryloylmorpholine, and the dripping time is 1 hour; at the same time, uniformly drip an ammonium persulfate initiator equivalent to 15% of the total mass of aconitic acid and 4-acryloylmorpholine, and the dripping time is 1.5 hours;

[0066] S2. After the addition is completed, the water bath temperature is maintained at 85°C, and the reaction is carried out for 2 hours. After the reaction is completed, the solution is cooled to room temperature to obtain a reaction product solution. The product is precipitated into a solid by anhydrous ethanol, and the purified polymer scale inhibitor is obtained by filtration, washing, and vacuum drying.

[0067] Comparative Example 3

[0068] The difference between this comparative example and Example 2 is that no aconitic acid is added, and the amount of aconitic acid added is replaced by itaconic acid, as follows:

[0069] This comparative example proposes a scale inhibitor, which is prepared by the following steps:

[0070] S1. Add itaconic acid and a certain amount of deionized water into a three-necked flask equipped with a reflux condenser, a thermometer and a stirring device, stir at a uniform speed until dissolved at 65° C., then add itaconic acid in an amount equal to that of aconitic acid in Example 2, stir to dissolve, and the mass of deionized water added is 1.6 times the total mass of itaconic acid; heat to 85° C. in a water bath, uniformly drip the amount of 4-acryloylmorpholine aqueous solution in Example 2, the deionized water in the 4-acryloylmorpholine aqueous solution is 1.5 times the mass of 4-acryloylmorpholine, and the dripping time is 1 hour; at the same time, uniformly drip an ammonium persulfate initiator equivalent to 15% of the total mass of itaconic acid and 4-acryloylmorpholine, and the dripping time is 1.5 hours;

[0071] S2. After the addition is completed, the water bath temperature is maintained at 85°C, and the reaction is carried out for 2 hours. After the reaction is completed, the solution is cooled to room temperature to obtain a reaction product solution. The product is precipitated into a solid by anhydrous ethanol, and the purified polymer scale inhibitor is obtained by filtration, washing, and vacuum drying.

[0072] Evaluation of scale inhibition performance

[0073] The scale inhibition ability of the polymer scale inhibitors prepared in Examples 1 to 4 and Comparative Examples 1 to 3 on calcium sulfate was tested. The test method was as follows:

[0074] Accurately weigh 0.50g of scale inhibitor, dissolve it in a small amount of pure water, transfer it to a 250mL volumetric flask and dilute to the mark to obtain a scale inhibitor solution. Take 150mL of pure water in a 250mL volumetric flask and add the pre-prepared CaCl 2 solution, making Ca 2+ Content: 3000mg·L -1 . Add 3.75 ml of antiscalant solution accurately, let it stand for 10 minutes, and then add the pre-prepared Na 2 SO 4 solution, making SO 4 2- Content: 7335mg·L -1 Dilute with pure water to the mark and put into a ground-mouth conical flask, place in a water bath at 50℃±1℃ for 30 minutes and let stand for 24 hours.

[0075] When the reaction is complete, the solution is cooled to room temperature and filtered with quantitative filter paper. 4 The filtrate was titrated with ethylenediaminetetraacetic acid (EDTA) standard solution to determine Ca 2+ The blank test was carried out at the same time. The test results are recorded in Table 1.

[0076] Table 1 Scale inhibition performance test results of Examples 1-4 and Comparative Examples 1-3

[0077]

[0078]

[0079] As can be seen from Table 1, the present invention uses itaconic acid, aconitic acid and 4-acryloylmorpholine as raw materials, uses ammonium persulfate redox initiator, and obtains a phosphorus-free terpolymer scale inhibitor through free radical copolymerization of aqueous solution, which has good scale inhibition performance for calcium sulfate; when the scale inhibitor dosage is 30 mg / L, the scale inhibition rate for calcium sulfate is 92.6% to 98.8%, achieving the prevention of scale formation in high hardness and high sulfate water at a lower concentration. The scale inhibition rate of the scale inhibitor of Comparative Example 1 without adding 4-acryloylmorpholine is lower, and the scale inhibition rates of the scale inhibitors of Comparative Example 2 without adding itaconic acid and Comparative Example 3 without adding aconitic acid are all lower.

[0080] In addition, it can be seen from the above results that the scale inhibition effect of Example 2 of the present invention is better, indicating that when the molar ratio of itaconic acid, aconitic acid and 4-acryloylmorpholine monomers is 3:2:1 and the amount of ammonium persulfate added is 15% of the total mass of itaconic acid, aconitic acid and 4-acryloylmorpholine, the product has a higher scale inhibition rate.

[0081] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A terpolymer, characterized in that Its structural formula is: In the formula, m, n, and p are any integers from 1 to 10 respectively.

2. A method for preparing the terpolymer according to claim 1, characterized in that: The following steps are involved: S1, mixing itaconic acid and water, then heating to 60-70°C and adding aconitic acid; then heating to 80-90°C, dropwise adding 4-acryloylmorpholine aqueous solution and initiator to obtain a mixture; S2. Continue to react the mixture at 80-90° C. to obtain the terpolymer.

3. The method for preparing the terpolymer according to claim 2, characterized in that: In step S1, the molar ratio of itaconic acid to aconitic acid is (1-2):1; and / or the molar ratio of itaconic acid to 4-acryloylmorpholine is (1-3):

1.

4. The method for preparing the terpolymer according to claim 2, characterized in that: In step S1, the initiator is ammonium persulfate.

5. The method for preparing the terpolymer according to claim 2 or 4, characterized in that: In step S1, the added amount of the initiator is 8%-15% of the total mass of the itaconic acid, the aconitic acid and the 4-acryloylmorpholine.

6. The method for preparing the terpolymer according to claim 2, characterized in that: In step S1, the time for dripping the 4-acryloylmorpholine aqueous solution and the time for dripping the initiator are 1-2 hours respectively.

7. The method for preparing the terpolymer according to claim 2, characterized in that: In step S2, the heat preservation reaction time at 80-90°C is 0.5-2h.

8. The method for preparing the terpolymer according to claim 2, characterized in that: In step S1, the mass of water mixed with the itaconic acid is 1.5-2 times the total mass of itaconic acid and aconitic acid; and / or the mass of water in the 4-acryloylmorpholine aqueous solution is 1.2-1.6 times the mass of 4-acryloylmorpholine.

9. A terpolymer scale inhibitor, characterized in that: The invention comprises the terpolymer according to claim 1 or the terpolymer prepared by the preparation method according to any one of claims 2 to 8.

10. Use of the terpolymer scale inhibitor according to claim 9 in an oilfield water treatment system.

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