A multifunctional scale inhibitor, its preparation method and application

Abstract

This invention belongs to the field of water treatment technology, specifically relating to a multifunctional scale inhibitor, its preparation method, and its application. It has the structure shown in formula (Ⅰ): Formula (Ⅰ); where m, n, and p are the molar ratio of polymer units, satisfying m:n:p = 1:(0.1~1):(0~0.5); the weight-average molecular weight of the multifunctional scale inhibitor is 4500~11000. Compared with existing technologies, this invention solves the problem of scale inhibition requirements in oilfield water systems with complex compositions, which are difficult to address in existing technologies. The scale inhibitor proposed in this solution improves scale inhibition performance in high-salinity oilfield water systems and also effectively enhances its stability in complex water environments.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a multifunctional scale inhibitor, its preparation method, and its application. Background Technology

[0002] In oilfield development, water treatment is a crucial step in ensuring safe and efficient operation. Oilfield water systems typically consist of produced water, injected water, and circulating water. These water bodies contain large amounts of dissolved salts, minerals, and impurities, especially calcium and magnesium ions. When calcium ions (Ca) in the water... 2+ ) and carbonate ions (CO3) 2- When the concentration of calcium carbonate (CaCO3) is high, it easily forms calcium carbonate (CaCO3) scale; when calcium ions in water react with sulfate ions (SO42-)... 2- When the concentration of calcium sulfate (CaSO4) is high, it easily forms scale. Scale formation not only severely reduces the heat exchange efficiency of oilfield equipment, but can also lead to blockages in pipelines and equipment, increase maintenance costs and operational difficulties, and even affect the production and safety of oilfield extraction.

[0003] In oilfield water treatment, scale inhibitors, as key chemicals for preventing scaling, are widely used in the water treatment of oilfield injection and production systems. Traditional oilfield scale inhibitors mainly include phosphorus compounds, such as organophosphonates. These compounds can effectively inhibit calcium salt scaling, but they can also cause environmental problems such as water pollution. Furthermore, their stability and effectiveness are limited in oilfield water systems with high salinity and high temperature.

[0004] In recent years, there has been an increasing demand for scale inhibitors that are phosphorus-free, green, biodegradable, and capable of maintaining good scale inhibition performance in oilfield water systems with high salinity and hardness. Polyaspartic acid (PASP), as a phosphorus-free and biodegradable polymer, has gradually gained attention in the field of oilfield water treatment due to its good environmental friendliness and strong calcium ion complexing ability. Unmodified PASP has a certain inhibitory effect on some scale, but its scale inhibition performance still has certain limitations in systems with high salinity and complex ionic composition.

[0005] Therefore, chemical modification of polyaspartic acid, especially the introduction of various complexing cation functional groups, to improve its scale inhibition performance and adaptability in complex oilfield water environments has become a current research hotspot. Introducing functional groups such as carboxyl, amino, and sulfonic acid groups can not only enhance its complexing ability for scale-forming ions but also improve its stability in high-salinity water systems, thus giving it broader application prospects.

[0006] Chinese patent CN104250378A primarily modifies PASP using amines such as diethylenetriamine. While this method enhances ion adsorption capacity by introducing amino groups, the active sites for adsorbing or complexing ions on its molecular chain are relatively singular. When treating complex oilfield water systems, a single functional group is insufficient to simultaneously inhibit the formation of different types of scale, and its scale inhibition performance is prone to deterioration under high-temperature conditions. Chinese patent CN105482117A discloses a modified polyaspartic acid scale inhibitor containing amino groups, but its preparation process is complex, requiring reaction in organic solvents, resulting in high costs. Furthermore, its scale inhibition performance is poor in oilfield water systems with complex water quality and the coexistence of multiple ions.

[0007] Furthermore, CN116970167A discloses a polyaspartic acid derivative prepared by graft copolymerization of polysuccinimide with 2-aminoethanesulfonic acid and acetaminoiminoacetic acid, resulting in a polyaspartic acid derivative containing carboxyl, amide, and sulfonic acid groups. While these functional groups help inhibit calcium scale formation, the relatively small number of functional groups may limit its scale inhibition performance in high-salinity and complex ionic systems, especially its weak complexation effect on multiple metal ions, compared to more complex water qualities. For example, CN117069938A discloses a polyaspartic acid derivative, its preparation method, and its application. Using easily degradable polyaspartic acid as a matrix, it is grafted and modified with 2-aminoethanesulfonic acid and lysine to synthesize the polyaspartic acid derivative. Although these groups can effectively inhibit the formation of calcium and silica scale, the variety and number of functional groups may be insufficient to cope with more complex water environments, especially in oilfield water or industrial cooling water with multiple ions, where it may not be able to effectively inhibit multiple types of scale simultaneously. Summary of the Invention

[0008] The purpose of this invention is to address at least one of the aforementioned problems by providing a multifunctional scale inhibitor, its preparation method, and its application. This addresses the limitations of existing technologies in handling scale inhibition requirements in oilfield water systems with complex compositions (multiple ion coexistence, high salinity, etc.). Specifically, existing scale inhibitors have sparsely distributed functional groups, and their calcium ion binding modes are mostly isolated electrostatic attraction or monodentate coordination, making them extremely unstable under the high temperature and high shear stress environment of oilfields. The chemical bonds are easily dissociated, leading to high-temperature failure of the scale inhibitor. The scale inhibitor proposed in this invention improves scale inhibition performance in high-salinity oilfield water systems and also effectively enhances its stability in complex water environments.

[0009] The objective of this invention is achieved through the following technical solution: The first aspect of this invention discloses a multifunctional scale inhibitor having the structure shown in formula (Ⅰ): Equation (Ⅰ); In the formula, m, n, and p are the molar ratios of polymer units, and satisfy m:n:p = 1:(0.1~1):(0~0.5); The weight-average molecular weight of the multifunctional scale inhibitor is 4500–11000.

[0010] A second aspect of this invention discloses a method for preparing a multifunctional scale inhibitor as described above, comprising the following steps: When p=0 in the multifunctional scale inhibitor: the multifunctional scale inhibitor, denoted as CM-DETA-PASP, is prepared by hydrolyzing and ring-opening polysuccinimide, followed by grafting diethylenetriamine structural units and further carboxymethylation. or, When p>0 in the multifunctional scale inhibitor: the multifunctional scale inhibitor, denoted as CM-DETA-AMSA-PASP, is prepared by hydrolyzing and ring-opening polysuccinimide, followed by grafting diethylenetriamine structural units and sulfonation modification, and further carboxymethylation.

[0011] Preferably, it includes the following steps: S1: Grafting reaction: When p=0 in the multifunctional scale inhibitor: then, S1-1: mix polysuccinimide with deionized water, then add diethylenetriamine to react and obtain a polyaspartic acid derivative with a diethylenetriamine graft structure. or, When p>0 in the multifunctional scale inhibitor: then, S1-2: mix polysuccinimide with deionized water, then add diethylenetriamine and aminomethanesulfonic acid to react and obtain a polyaspartic acid derivative grafted with diethylenetriamine and sulfonic acid groups. S2: Carboxymethylation: Sodium chloroacetate solution and sodium hydroxide solution are added to the solution obtained in step S1, and the reaction is carried out to obtain the multifunctional scale inhibitor.

[0012] Preferably, step S1 includes: The mass ratio of polysuccinimide to deionized water is 1:4 to 1:6; When p=0 in the multifunctional scale inhibitor: In step S1-1, the molar ratio of polysuccinimide to diethylenetriamine is 1:(0.1~1); When p>0 in the multifunctional scale inhibitor: In steps S1-2, the molar ratio of polysuccinimide to diethylenetriamine and methyl sulfonic acid is 1:(0.1-0.5):(0.1-0.5).

[0013] Preferably, step S1 includes: The reaction temperature is 60℃, and the reaction time is 6 to 12 hours.

[0014] Preferably, step S2 includes: The sodium chloroacetate solution has a mass concentration of 70%, the sodium hydroxide solution has a mass concentration of 30%, and the molar ratio of sodium hydroxide to sodium chloroacetate is 1:1.

[0015] Preferably, step S2 includes: The reaction temperature is 50℃~70℃, and the reaction time is 8~12 hours. Preferably, step S2 includes: After the reaction, the reaction solution was neutralized with dilute hydrochloric acid, and anhydrous ethanol was added to precipitate the reaction product. After standing, the product was filtered to obtain a solid product. The solid product was then washed, dried, and dialyzed to obtain the multifunctional scale inhibitor.

[0016] Preferably, the dialysis is performed using a dialysis bag with a molecular weight cutoff of 1000.

[0017] The third aspect of this invention discloses the application of the multifunctional scale inhibitor described above in the oilfield water treatment process.

[0018] The working principle of this invention is as follows: The scale inhibitor proposed and prepared in this invention introduces multiple functional groups (including carboxyl, amino, and sulfonic acid groups) into the polyaspartic acid molecule. The CM-DETA-PASP and CM-DETA-AMSA-PASP molecules respectively introduce functional groups such as diethylenetriamine (DETA) and aminomethanesulfonic acid (AMSA), each possessing a strong chelating effect. The amino group (-NH2) in the DETA molecule interacts with calcium ions (Ca... 2+ It has a strong coordination ability and can stably coordinate with Ca. 2+ The formation of chelates inhibits the nucleation and growth of calcium scale. Simultaneously, the sulfonic acid groups (-SO3H) in AMSA possess strong hydrophilicity and charge distribution, enabling further chelation with calcium ions and providing additional stabilizing effects. The synergistic effect between these functional groups (the combined chelating effect of DETA and AMSA) significantly enhances the adsorption capacity for calcium ions, thereby improving the scale inhibition effect against calcium scale.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) The scale inhibitors of the present invention introduce complexing functional groups such as carboxyl, amino and sulfonic acid groups. The scale inhibitors CM-DETA-PASP and CM-DETA-AMSA-PASP prepared by the present invention have a variety of complexing cation functional groups, which can synergistically inhibit the formation of scale under different mechanisms and have a significant effect on inhibiting common inorganic scales such as calcium sulfate and calcium carbonate.

[0020] (2) The scale inhibitors of the present invention not only significantly improve the scale inhibition performance in high-salinity oilfield water systems, but also effectively enhance their stability in complex water environments. In particular, the materials of the present invention exhibit significant effects in inhibiting CaSO4 and CaCO3 scale: at a dosage of 4 mg / L, the scale inhibition rate of CM-DETA-PASP for CaSO4 is not less than 92%; at a dosage of 8 mg / L, the scale inhibition rate of CM-DETA-AMSA-PASP for CaSO4 is not less than 95%; and at a dosage of 50 mg / L, the scale inhibition rates of both scale inhibitors provided by the present invention for CaCO3 can reach approximately 50%.

[0021] (3) The multifunctional scale inhibitor of the present invention is suitable for complex water systems such as oilfield produced water, injection water and circulating water, and exhibits excellent scale inhibition effect, especially in water environments with high mineralization and high hardness.

[0022] (4) The multifunctional scale inhibitor of the present invention does not contain phosphorus, which meets the requirements of green environmental protection and can simultaneously take into account the dual advantages of high efficiency scale inhibition and environmental friendliness. The preparation method of the multifunctional scale inhibitor of the present invention is simple, the reaction conditions are mild, the raw materials are widely available, and it is easy to industrialize.

[0023] Furthermore, compared to existing technologies that disclose a series of polyaspartic acid derivatives as scale inhibitors for water bodies, this method employs a strategy of first grafting DETA onto polysuccinimide (PSI) and then performing carboxymethylation with chloroacetic acid. This sequence ensures that the active sites of the amino groups are first locked onto the polymer backbone and then controlled to be converted into carboxyl groups, avoiding excessive cross-linking of side chains. Each modified site forms a locally high charge density region that can better bind free calcium ions. Moreover, the resulting multifunctional scale inhibitor has a greater number of carboxyl and amino groups: more carboxyl groups significantly enhance the complexing ability of calcium ions, thereby improving the inhibition effect on calcium scale; while the increase in amino groups enhances the adsorption capacity for various metal ions, improving performance in complex water quality environments.

[0024] Existing technologies produce scale inhibitors with extremely short side chains. These short side chains lack longitudinal extension when adsorbed onto metal surfaces or crystal nuclei, resulting in extremely thin molecular layers and small capture radii for calcium ions. Unlike existing technologies, this approach introduces a composite long side chain composed of DETA and carboxymethyl groups. The longer side chain exhibits an extended conformation in water, increasing the adhesion between the scale inhibitor molecules and free Ca2+. 2+ This increases the probability of effective collisions and improves the efficiency of trapping scale-forming ions. Furthermore, multiple N and O atoms in the molecule can simultaneously interact with the same Ca²⁺ ion. 2+Coordination occurs. According to coordination chemistry theory, the ring structure formed by multidentate chelation possesses extremely high thermodynamic stability. Therefore, the multifunctional scale inhibitor in this scheme exhibits superior scale inhibition performance. Attached Figure Description

[0025] Figure 1 Infrared spectra of CM-DETA-PASP prepared in Example 1 and CM-DETA-AMSA-PASP prepared in Example 3, as well as PASP and PSI. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0027] Unless otherwise specified in the following description, the reagents used are conventional commercial products, the methods used are well-known in the art, and any other matters not covered herein may be handled using existing technologies.

[0028] A multifunctional scale inhibitor is a polyaspartic acid graft polymer containing at least carboxyl, amino, and optionally sulfonic acid groups, and its structure is shown in formula (Ⅰ): Equation (Ⅰ); In equation (Ⅰ), m, n, and p are the molar ratios of polymer units, satisfying m:n:p=1:(0.1~1):(0~0.5).

[0029] Specifically, when p=0, the scale inhibitor is a polymer containing carboxyl and amine groups, specifically polyaspartic acid CM-DETA-PASP modified by grafting with diethylenetriamine and further carboxymethylation; when p>0, the scale inhibitor is a polymer containing carboxyl, amine and sulfonic acid groups, specifically polyaspartic acid CM-DETA-AMSA-PASP modified by grafting with diethylenetriamine and methyl sulfonic acid and further carboxymethylation.

[0030] The weight-average molecular weight of this multifunctional scale inhibitor is 4500–11000.

[0031] A method for preparing multifunctional scale inhibitors involves a hydrolytic ring-opening reaction of polysuccinimide, grafting diethylenetriamine structural units, optional sulfonation modification, and further carboxymethylation to prepare synergistic multifunctional scale inhibitors CM-DETA-PASP and CM-DETA-AMSA-PASP. This method is simple, uses mild reaction conditions, utilizes widely available raw materials, and is easily suitable for industrial production.

[0032] The preparation method of this multifunctional scale inhibitor (CM-DETA-PASP) specifically includes: Polysuccinimide is mixed with deionized water at a mass ratio of 1:4 to 1:6.

[0033] Further, diethylenetriamine was added to the solution and reacted with polysuccinimide. The molar ratio of polysuccinimide to diethylenetriamine was 1:(0.1-1), the reaction temperature was 60℃, and the reaction time was 6-12 hours to obtain a polyaspartic acid derivative with a diethylenetriamine grafted structure.

[0034] Further, sodium chloroacetate is dissolved in deionized water and the sodium chloroacetate solution is added to the above reaction solution, wherein the mass fraction of the sodium chloroacetate solution is 70%.

[0035] Further, a 30% sodium hydroxide solution was added to the above reaction solution, with a molar ratio of sodium hydroxide to sodium chloroacetate of 1:1. The reaction temperature was 50℃~70℃, and the reaction time was 8~12 hours to obtain modified polyaspartic acid.

[0036] Further, after the reaction was completed, the above reaction solution was neutralized with dilute hydrochloric acid to pH=7.0, and 150 mL of anhydrous ethanol was added to precipitate the reaction product. After standing for 12 hours, the product was filtered to obtain a solid product.

[0037] Finally, the solid product was washed several times with anhydrous ethanol and dried to constant weight in a constant temperature drying oven. Finally, it was dialyzed using a dialysis bag with a molecular weight cutoff of 1000 to obtain the CM-DETA-PASP product.

[0038] The preparation method of this multifunctional scale inhibitor (CM-DETA-AMSA-PASP) specifically includes: Polysuccinimide is mixed with deionized water at a mass ratio of 1:4 to 1:6.

[0039] Further, diethylenetriamine and aminomethanesulfonic acid were added to the above reaction system, with the molar ratio of polysuccinimide to diethylenetriamine and aminomethanesulfonic acid being 1:(0.1-0.5):(0.1-0.5). The reaction was carried out at 60°C for 6-12 hours to obtain a polyaspartic acid derivative grafted with diethylenetriamine and sulfonic acid groups.

[0040] Further, a 70% sodium chloroacetate aqueous solution was added to the above reaction system, followed by a slow dropwise addition of a 30% sodium hydroxide solution. The molar ratio of sodium hydroxide to sodium chloroacetate was 1:1. The reaction was carried out at 50℃ to 70℃ for 8 to 12 hours.

[0041] Further, after the reaction was completed, the above reaction solution was neutralized with dilute hydrochloric acid to pH=7.0, 150 mL of anhydrous ethanol was added, stirred evenly and allowed to stand for 12 hours to allow the product to be fully separated; the solid product was collected by filtration and washed several times with anhydrous ethanol.

[0042] Further, the obtained solid product was dried to constant weight and then purified by dialysis using a dialysis bag with a molecular weight cutoff of 1000 to obtain the final CM-DETA-AMSA-PASP product.

[0043] The scale inhibitor obtained by this invention possesses multiple complexed cation functional groups, exhibiting significant scale inhibition performance in oilfield circulating water systems against common inorganic scale such as calcium sulfate (CaSO4) and calcium carbonate (CaCO3). The multifunctional scale inhibitor provided by this invention is phosphorus-free, meets green chemistry requirements, and has good environmental friendliness. It can be widely applied to scale control in complex water systems such as oilfield produced water, injection water, and circulating water, and also possesses good environmental friendliness and biodegradability.

[0044] Example 1 A method for preparing a multifunctional scale inhibitor includes the following steps: Weigh 5.05 g of polysuccinimide, measure 30.0 mL of deionized water and 5.38 mL of diethylenetriamine, mix them in a three-necked flask, and stir the mixture at 60 °C for 12 hours. After cooling, add a 70% aqueous solution prepared from 20.38 g of sodium chloroacetate to the three-necked flask, and slowly add 17.54 mL of 30% NaOH solution. React at 60 °C for 8 hours.

[0045] After the reaction was complete, the solution was neutralized to pH 7.0 with dilute hydrochloric acid, and 150 mL of anhydrous ethanol was added. The mixture was stirred until homogeneous and allowed to stand for 12 hours to precipitate the product. The solid product was filtered, washed several times with anhydrous ethanol, and finally dried to constant weight. It was then purified by dialysis using a dialysis bag with a molecular weight cutoff of 1000 to obtain the product CM-DETA-PASP.

[0046] According to gel permeation chromatography (GPC) analysis, the polymer's weight-average molecular weight is 4867. The infrared spectrum is shown below. Figure 1 As shown in the PSI spectrum, the stretching vibration absorption peaks of NH and C=O in the five-membered imide ring are at 3435.56 cm⁻¹. -1 1713.3 cm -1 .

[0047] In the PASP spectrum, the peaks for NH and C=O appear at 3257.06 cm⁻¹. -1 and 1561.34 cm -1 Location. 1387.66 cm-1 This corresponds to the symmetrical stretching of the carboxylate group (-COO-). 1713.3 cm⁻¹ in PSI. -1 The complete disappearance of the C=O stretching vibration absorption peak proves that the imine ring completely opens under high alkaline conditions and transforms into a polyamide skeleton.

[0048] In the CM-DETA-PASP spectrum, NH and C=O appear at 3305.31 cm⁻¹, respectively. -1 and 1570.98 cm -1 Location, 1392.49 cm -1 This corresponds to the symmetrical stretching of the carboxylate group (-COO-). Besides having the same characteristic peaks as PASP, a different peak can be found at 1146.45 cm⁻¹ in the fingerprint region. -1 Several sharp peaks appeared nearby, which correspond to the CN stretching vibration in the DETA side chain and the CO vibration after carboxymethylation, proving that the complex side chain structure has been successfully grafted onto the main chain.

[0049] Example 2 A method for preparing a multifunctional scale inhibitor includes the following steps: Weigh 5.05 g of polysuccinimide, measure 30.0 mL of deionized water and 0.54 mL of diethylenetriamine, mix them in a three-necked flask, and stir the mixture at 60 °C for 12 hours. After cooling, add a 70% aqueous solution prepared from 2.04 g of sodium chloroacetate to the three-necked flask, and slowly add 1.75 mL of 30% NaOH solution. React at 60 °C for 8 hours.

[0050] After the reaction was complete, the solution was neutralized to pH 7.0 with dilute hydrochloric acid, and 150 mL of anhydrous ethanol was added. The mixture was stirred until homogeneous and allowed to stand for 12 hours to precipitate the product. The solid product was filtered, washed several times with anhydrous ethanol, and finally dried to constant weight. It was then purified by dialysis using a dialysis bag with a molecular weight cutoff of 1000 to obtain the product CM-DETA-PASP.

[0051] According to GPC analysis, the weight-average molecular weight of the polymer is 6686.

[0052] Example 3 A method for preparing a multifunctional scale inhibitor includes the following steps: Weigh 5.05 g of polysuccinimide, 40.0 mL of deionized water, 2.7 mL of diethylenetriamine, and 2.78 g of sulfamic acid. Mix them in a three-necked flask and heat at 60 °C for 6 hours. Add sodium hydroxide solution dropwise until the pH reaches 9–11, and stir at 60 °C for 12 hours. After cooling, prepare a 70% aqueous solution of 20.38 g of sodium chloroacetate and add it to the three-necked flask. Slowly add 8.8 mL of 30% NaOH solution and react at 60 °C for 12 hours.

[0053] After the reaction was complete, the solution was neutralized to pH 7.0 with dilute hydrochloric acid, and 150 mL of anhydrous ethanol was added. The mixture was stirred until homogeneous and allowed to stand for 12 hours to precipitate the product. The solid product was filtered, washed several times with anhydrous ethanol, and finally dried to constant weight. It was then purified by dialysis using a dialysis bag with a molecular weight cutoff of 1000 to obtain the product CM-DETA-AMSA-PASP.

[0054] GPC analysis showed that the polymer's weight-average molecular weight was 10345. The infrared spectrum is shown below. Figure 1 As shown in the CM-DETA-AMSA-PASP spectrum, the peaks for NH and C=O appear at 3305.31 cm⁻¹. -1 and 1585.46 cm -1 Location. 1397.31 cm -1 This corresponds to the symmetrical stretching of the carboxylate group (-COO-). In addition to the characteristic peaks shared with PASP, several new peaks were observed in the fingerprint region. 1182.63 cm⁻¹ -1 Corresponding to the antisymmetric stretching of the sulfonic acid group (-SO3-), 1047.55 cm -1 This corresponds to the symmetrical stretching of the sulfonic acid group, and 1182.63 cm. -1 The peaks together constitute the fingerprint characteristics of sulfonates. 1146.45 cm⁻¹ -1 and 1107.86 cm -1 The peaks correspond to CN / CO stretching vibrations, reflecting the amino skeleton of DETA and the ether / ester bond characteristics of CM, proving that CM-DETA-AMSA-PASP was successfully synthesized.

[0055] Comparative Examples 1-2 The commonly available scale inhibitors EDTA and DTPA are used.

[0056] Scale inhibition performance test The scale inhibition performance of the polymer products prepared in Examples 1-3 on calcium sulfate was tested using the following methods: Calcium sulfate: In accordance with the People's Republic of China Petroleum and Natural Gas Industry Standard SY / T 5673-2020 "General Technical Conditions for Oilfield Scale Inhibitors", a static scale inhibition experiment was conducted on the scale inhibition effect of the prepared modified polyaspartic acid on CaSO4 scale.

[0057] Prepare a test solution in a 250 mL volumetric flask containing 2000 mg / L calcium ions and 4800 mg / L sulfate ions. Add an appropriate amount of borax buffer solution to make the test solution weakly alkaline. Add a certain amount (see Tables 1-3) of the polymer scale inhibitor solution prepared in Examples 1-3 to the volumetric flask, and simultaneously perform a blank control group experiment (without adding scale inhibitor). Incubate the solution in a 70°C water bath for 6 hours. After the reaction is complete, cool the solution to room temperature and filter it using quantitative filter paper. Titrate the CaSO4 filtrate with ethylenediaminetetraacetic acid standard solution to determine the Ca2+ content. 2+ The concentration of calcium sulfate was determined. A blank test was conducted simultaneously. The scale inhibition performance of the calcium sulfate in the three examples is shown in Tables 1, 2, and 3, respectively.

[0058] Calcium carbonate: In accordance with GB / T 16632-2019 "Determination of scale inhibition performance of water treatment agents - calcium carbonate deposition method", a static scale inhibition experiment was conducted on the scale inhibition effect of the prepared modified polyaspartic acid on CaCO3 scale.

[0059] Add 250 mL of water to a 500 mL volumetric flask. Using a burette, add a specific volume of calcium chloride standard solution to bring the calcium ion concentration to 240 mg / L. Add a specific volume of scale inhibitor solution using a pipette and mix well. Then add 20 mL of borax buffer solution and mix well. Slowly add a specific volume of sodium bicarbonate standard solution using a burette (while shaking) to bring the bicarbonate ion concentration to 732 mg / L. Dilute to the mark with water and mix well. Transfer to an Erlenmeyer flask and incubate at 80°C for 10 hours. After the reaction is complete, cool the solution to room temperature and filter using quantitative filter paper. Titrate the CaCO3 filtrate with ethylenediaminetetraacetic acid standard solution to determine the CaCO3 concentration. 2+ The concentration was determined. A blank test (without scale inhibitor) was conducted simultaneously. The scale inhibition performance of calcium carbonate in the three examples is shown in Table 4.

[0060] Table 1 Static scale inhibition test of calcium sulfate in Example 1 Table 2 Example 2 Static scale inhibition test of calcium sulfate Table 3 Example 3 Static scale inhibition test of calcium sulfate As shown in Tables 1 and 2, the multifunctional scale inhibitor provided by this invention has good inhibition performance against calcium sulfate. A scale inhibition efficiency of over 92% can be achieved with 4 mg / L of the scale inhibitor CM-DETA-PASP. As shown in Table 3, a scale inhibition efficiency of over 95% can be achieved with 8 mg / L of the scale inhibitor CM-DETA-AMSA-PASP.

[0061] Table 4 Static scale inhibition tests of calcium carbonate in Examples 1, 2, and 3 As shown in Table 4, the multifunctional scale inhibitor provided by this invention also has good inhibition performance against calcium carbonate, and a scale inhibition efficiency of about 50% can be achieved with 50 mg / L of scale inhibitor.

[0062] Scale inhibition tests were conducted on Comparative Example 1 (EDTA) and Comparative Example 2 (DTPA), and the results are shown in Tables 5 and 6.

[0063] Table 5 Static scale inhibition test of commonly used scale inhibitor calcium sulfate Table 6 Static scale inhibition test of commonly used scale inhibitor calcium carbonate In summary, this invention demonstrates significant scale inhibition in the field of oilfield water treatment, and also exhibits good environmental friendliness and biodegradability.

[0064] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A multifunctional scale inhibitor, characterized in that, It has the structure shown in equation (Ⅰ): Equation (Ⅰ); In the formula, m, n, and p are the molar ratios of polymer units, and satisfy m:n:p = 1:(0.1~1):(0~0.5); The weight-average molecular weight of the multifunctional scale inhibitor is 4500–11000.

2. A method for preparing the multifunctional scale inhibitor as described in claim 1, characterized in that, Includes the following steps: When p=0 in the multifunctional scale inhibitor: the multifunctional scale inhibitor is prepared by hydrolyzing and ring-opening polysuccinimide, then grafting diethylenetriamine structural units, and further performing carboxymethylation. or, When p>0 in the multifunctional scale inhibitor: the multifunctional scale inhibitor is prepared by hydrolyzing and ring-opening polysuccinimide, followed by grafting diethylenetriamine structural units and sulfonation modification, and further carboxymethylation.

3. The method for preparing a multifunctional scale inhibitor according to claim 2, characterized in that, Includes the following steps: S1: Grafting reaction: When p=0 in the multifunctional scale inhibitor: then, S1-1: mix polysuccinimide with deionized water, then add diethylenetriamine to react and obtain a polyaspartic acid derivative with a diethylenetriamine graft structure. or, When p>0 in the multifunctional scale inhibitor: then, S1-2: mix polysuccinimide with deionized water, then add diethylenetriamine and aminomethanesulfonic acid to react and obtain a polyaspartic acid derivative grafted with diethylenetriamine and sulfonic acid groups. S2: Carboxymethylation: Sodium chloroacetate solution and sodium hydroxide solution are added to the solution obtained in step S1, and the reaction is carried out to obtain the multifunctional scale inhibitor.

4. The method for preparing a multifunctional scale inhibitor according to claim 3, characterized in that, Step S1 includes: The mass ratio of polysuccinimide to deionized water is 1:4 to 1:6; When p=0 in the multifunctional scale inhibitor: In step S1-1, the molar ratio of polysuccinimide to diethylenetriamine is 1:(0.1~1); When p>0 in the multifunctional scale inhibitor: In steps S1-2, the molar ratio of polysuccinimide to diethylenetriamine and methyl sulfonic acid is 1:(0.1-0.5):(0.1-0.5).

5. The application of the multifunctional scale inhibitor as described in claim 1 in the oilfield water treatment process.

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