Nitrogen and sulfur doped carbon quantum dot scale inhibitor for oilfield development as well as preparation method and application of nitrogen and sulfur doped carbon quantum dot scale inhibitor

Abstract

The invention discloses a nitrogen-sulfur-doped carbon quantum dot scale inhibitor for oilfield development as well as a preparation method and application thereof, and belongs to the technical field of petrochemical industry. The preparation method comprises the following steps: adding citric acid and thioamino acid into deionized water, stirring and dissolving to form a solution; performing high-temperature carbonization reaction on the solution, cooling to room temperature after the high-temperature carbonization reaction is finished to prepare a preliminarily synthesized carbon quantum dot solution, and purifying the preliminarily synthesized carbon quantum dot solution to prepare a purified carbon quantum dot solution; a polyethyleneimine solution is prepared; dropwise adding a polyethyleneimine solution into the purified carbon quantum dot solution to perform surface modification reaction, and after the surface modification reaction is finished, precipitating by using absolute ethyl alcohol, and freeze-drying to obtain the nitrogen-sulfur doped carbon quantum dot scale inhibitor for oilfield development. The surface of the nitrogen-sulfur-doped carbon quantum dot scale inhibitor is provided with a large number of functional groups such as amino groups and carboxyl groups, and the scale inhibitor has efficient scale inhibition performance. And the carbon quantum dots are a material with excellent fluorescence characteristics, low toxicity and good biocompatibility, and have significant technical advantages and wide application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry, and in particular relates to a nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development, and a preparation method and application thereof. Background Art

[0002] With the continuous growth of oilfield exploitation, the treatment of oilfield water has gradually become one of the important factors restricting oilfield production efficiency and environmental protection. Oilfield water contains a large amount of hard water ions (such as calcium ions, etc.). These ions are easy to react with other components in the water under high temperature and high pressure conditions to form mineral precipitation such as calcium carbonate, causing scaling, which in turn affects the normal operation of equipment, increases the maintenance cost of pipelines and equipment, and even leads to production stagnation. Therefore, the application of scale inhibitors has become one of the key technologies in oilfield water treatment.

[0003] At present, the common oilfield water scale inhibitors are mostly organic phosphates, polymers, inorganic salts, etc., but these traditional scale inhibitors have certain limitations in the application process. For example, although organic phosphate scale inhibitors are effective, their long-term use may cause environmental pollution, and their effectiveness is reduced in high-salt environments; polymer scale inhibitors are prone to adverse reactions with other substances in the water, resulting in their effectiveness attenuation. Therefore, the development of environmentally friendly, efficient and stable scale inhibitors has become an important research direction in the field of oilfield water treatment. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development and its preparation method and application. First, citric acid is used as a carbon source and thioamino acids are used as nitrogen and sulfur sources to prepare carbon quantum dots by a hydrothermal method. Then, polyethyleneimine is used to modify the carbon quantum dots through covalent bonds to form the nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: On the one hand, the present invention provides a method for preparing a nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development, comprising the following steps: Add citric acid and thioamino acid into deionized water, stir and dissolve to form a solution; The solution is subjected to a high-temperature carbonization reaction, and after the high-temperature carbonization reaction is completed, the solution is cooled to room temperature to obtain a preliminarily synthesized carbon quantum dot solution, and the preliminarily synthesized carbon quantum dot solution is purified to obtain a purified carbon quantum dot solution; Dissolving polyethyleneimine in deionized water to prepare a polyethyleneimine solution; The polyethyleneimine solution is added dropwise to the purified carbon quantum dot solution to carry out a surface modification reaction. After the surface modification reaction is completed, the carbon quantum dot solution modified by polyethyleneimine is precipitated with anhydrous ethanol, and then freeze-dried to obtain a nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development.

[0006] In one embodiment, the thioamino acid is one of cystine, methionine and cysteine.

[0007] In one embodiment, the mass ratio of the thioamino acid to citric acid is 1:(2-2.4).

[0008] In one embodiment, the amount of deionized water added to the solution is 15 to 20 times the total mass of the thioamino acid and citric acid.

[0009] In one embodiment, the reaction temperature of the high temperature carbonization reaction is 160-180° C., and the reaction time of the high temperature carbonization reaction is 8-10 h; The reaction temperature of the surface modification reaction is 60-80°C, and the reaction time of the surface modification reaction is 20-24h.

[0010] In one embodiment, the purification process is as follows: The large particles were removed by microporous membrane filtration, and the unreacted small molecule impurities were removed by dialysis bag for 3 days to obtain a purified carbon quantum dot solution; The particle size of the microporous filter membrane is 0.22 μm, and the molecular weight cutoff of the dialysis bag is 1000 Da.

[0011] In one embodiment, the mass ratio of polyethyleneimine to deionized water in the polyethyleneimine solution is 1:(15-20).

[0012] In one embodiment, the mass ratio of the polyethyleneimine solution to the purified carbon quantum dot solution is 1:(2-3).

[0013] The present invention also provides a nitrogen-sulfur-doped carbon quantum dot scale inhibitor for oil field development, which is prepared by the preparation method of the nitrogen-sulfur-doped carbon quantum dot scale inhibitor for oil field development.

[0014] The present invention also provides the use of the nitrogen-sulfur-doped carbon quantum dot scale inhibitor for oil field development prepared by the preparation method of the nitrogen-sulfur-doped carbon quantum dot scale inhibitor for oil field development in the process of oil field development.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing a nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development. The method first uses citric acid as a carbon source and thioamino acids as nitrogen and sulfur sources to prepare carbon quantum dots by a hydrothermal method, and then uses polyethyleneimine to modify the carbon quantum dots by covalent bonds to form the nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development. The method introduces thioamino acids so that nitrogen and sulfur elements are directly doped into the structure of carbon quantum dots in a hydrothermal reaction, thereby avoiding a complex multi-step doping process. Polyethyleneimine reacts with carboxyl or hydroxyl groups on the surface of carbon quantum dots by covalent bonds to form stable chemical bonds, thereby avoiding the instability of physical adsorption modification.

[0016] The carbon quantum dot scale inhibitor prepared by the present invention, first of all, has efficient scale inhibition performance, and the surface of the carbon quantum dots modified by polyethyleneimine carries a large number of functional groups such as amino and carboxyl groups. These functional groups can effectively adsorb metal cations in complex water, inhibit them from reacting with other ions to form precipitation, and reduce the possibility of scaling. Secondly, the carbon quantum dots themselves have excellent fluorescence properties, and the distribution and effect of the scale inhibitor can be observed in real time by a fluorescence microscope or a fluorescence detector. Finally, the carbon quantum dots themselves are materials with low toxicity and good biocompatibility. Compared with traditional phosphate scale inhibitors, the carbon quantum dot scale inhibitor modified by polyethyleneimine will not produce secondary pollution in the environment. Its green and environmentally friendly characteristics make it a more sustainable solution, especially suitable for oilfield water treatment and other fields that need to pay attention to environmental protection, with significant technical advantages and broad application prospects.

[0017] The carbon quantum dot scale inhibitor prepared by the present invention is suitable for use in the oil field development process. The carbon quantum dot scale inhibitor can not only effectively inhibit the formation of common scales, but also has a certain fluorescence intensity, which is convenient for real-time monitoring of the concentration of the scale inhibitor in the water system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the particle size distribution diagram of the carbon quantum dot scale inhibitor prepared in Example 6; Figure 2 This is the fluorescence spectrum of the carbon quantum dot scale inhibitor prepared in Example 6; Figure 3 This is a diagram of the scale inhibition performance of the carbon quantum dot scale inhibitor prepared in Example 6. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0020] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0021] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0022] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0023] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0024] In recent years, carbon quantum dots, as a new type of nanomaterial, have been widely used in many fields due to their good fluorescence properties, chemical stability, low toxicity and environmental friendliness. Carbon quantum dots have abundant surface functional groups, which can significantly reduce the formation of scale through adsorption and complexation when reacting with metal ions or minerals in the solution. They have gradually become a research hotspot in the field of oilfield water treatment and have broad application prospects and market potential.

[0025] Based on the above content, the present invention provides a method for preparing a nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development, comprising the following steps: Add citric acid and thioamino acid into deionized water, stir and dissolve to form a solution; The solution is subjected to a high-temperature carbonization reaction using a high-temperature and high-pressure reactor, and after the high-temperature carbonization reaction is completed, the solution is cooled to room temperature to obtain a preliminarily synthesized carbon quantum dot solution, and the preliminarily synthesized carbon quantum dot solution is purified to obtain a purified carbon quantum dot solution; Dissolving polyethyleneimine in deionized water to prepare a polyethyleneimine solution; The polyethyleneimine solution is added dropwise to the purified carbon quantum dot solution to carry out a surface modification reaction. After the surface modification reaction is completed, the carbon quantum dot solution modified by polyethyleneimine is precipitated with anhydrous ethanol to remove unreacted polyethyleneimine and other impurities. The product solution after the impurities are removed is then freeze-dried to obtain a nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development.

[0026] More specific preparation steps are as follows: S1: Add a certain amount of citric acid and thioamino acid to deionized water, stir ultrasonically for 30 min to completely dissolve them and form a uniform transparent solution. Transfer the solution to a high-pressure reactor with a polytetrafluoroethylene liner and perform a high-temperature carbonization reaction at 160-180°C for 8-10 h. After the high-temperature carbonization reaction, the reactor is naturally cooled to room temperature to obtain a brown-yellow transparent solution, which is the initially synthesized carbon quantum dot solution. Use a microporous filter membrane to remove large particles, and use a dialysis bag for 3 days to remove unreacted small molecular impurities to obtain a purified carbon quantum dot solution, which is recorded as solution A.

[0027] Among them, the thioamino acid is one of cystine, methionine and cysteine, the mass ratio of the thioamino acid to citric acid is 1:(2~2.4), the amount of deionized water added is 15~20 times the total mass of the thioamino acid and citric acid, the particle size of the microporous filter membrane is 0.22 μm, and the cutoff molecular weight of the dialysis bag is 1000 Da.

[0028] S2: A certain amount of polyethyleneimine was dissolved in deionized water and magnetically stirred for 20 min to obtain solution B, i.e., polyethyleneimine solution. A certain amount of solution B was slowly added dropwise to solution A, placed in a three-necked flask with a stirring device, and subjected to surface modification reaction at 60-80°C for 20-24 h, and then anhydrous ethanol was used to precipitate the carbon quantum dot solution modified by polyethyleneimine for 10-12 h, and then the product solution after impurities were removed was freeze-dried to obtain a solid powder, which was the nitrogen-sulfur doped carbon quantum dot scale inhibitor for the oil field development.

[0029] Among them, the mass ratio of polyethyleneimine to deionized water is 1: (15~20), and the mass ratio of solution B to solution A is 1: (2~3).

[0030] The nitrogen-sulfur doped carbon quantum dot scale inhibitor prepared by the present invention has a large number of amino and carboxyl functional groups on its surface, which can effectively adsorb metal cations in complex water, inhibit them from reacting with other ions to generate precipitation, and has high scale inhibition performance. In addition, the carbon quantum dots themselves are a material with excellent fluorescence properties, low toxicity and good biocompatibility, and have significant technical advantages and broad application prospects.

[0031] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0032] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0033] Example 1 This embodiment provides a method for preparing a nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development, comprising the following steps: S1: Add 2 g of citric acid and 1 g of cystine to 45 g of deionized water, stir ultrasonically for 30 min to completely dissolve them and form a uniform transparent solution. Transfer the solution to a high-pressure reactor with a polytetrafluoroethylene liner and react at 160°C for 8 h. After the reaction, the reactor was naturally cooled to room temperature to obtain a brown-yellow transparent solution, which was the initially synthesized carbon quantum dot solution. Use a 0.22 μm microporous filter membrane to remove large particles, and use a dialysis bag with a molecular weight cutoff of 1000 Da for 3 days to remove unreacted small molecule impurities to obtain a purified carbon quantum dot solution, which is recorded as solution A.

[0034] S2: Dissolve 1 g of polyethyleneimine in 15 g of deionized water and stir magnetically for 20 min to obtain solution B. Slowly add 16 g of solution B to 32 g of solution A, place in a three-necked flask with a stirring device, and react at 60°C for 20 h. Then use anhydrous ethanol to precipitate the solution for 10 h, freeze-dry to obtain a solid powder, which is the nitrogen-sulfur doped carbon quantum dot scale inhibitor for the oil field development.

[0035] Example 2 This embodiment provides a method for preparing a nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development, comprising the following steps: S1: Add 2.2 g of citric acid and 1 g of methionine to 48 g of deionized water, stir ultrasonically for 30 min to completely dissolve them and form a uniform transparent solution. Transfer the solution to a high-pressure reactor with a polytetrafluoroethylene liner and react at 170°C for 8 h. After the reaction, the reactor was naturally cooled to room temperature to obtain a brown-yellow transparent solution, which was the initially synthesized carbon quantum dot solution. Use a 0.22 μm microporous filter membrane to remove large particles, and use a dialysis bag with a molecular weight cutoff of 1000 Da for 3 days to remove unreacted small molecule impurities to obtain a purified carbon quantum dot solution, which is recorded as solution A.

[0036] S2: Dissolve 1 g of polyethyleneimine in 20 g of deionized water and stir magnetically for 20 min to obtain solution B. Slowly add 21 g of solution B to 45 g of solution A, place in a three-necked flask with a stirring device, and react at 80°C for 20 h. Then use anhydrous ethanol to precipitate the solution for 12 h, freeze-dry to obtain a solid powder, which is the nitrogen-sulfur doped carbon quantum dot scale inhibitor for the oil field development.

[0037] Example 3 This embodiment provides a method for preparing a nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development, comprising the following steps: S1: Add 2.4 g of citric acid and 1 g of cysteine ​​to 51 g of deionized water, stir ultrasonically for 30 min to completely dissolve them and form a uniform transparent solution. Transfer the solution to a high-pressure reactor with a polytetrafluoroethylene liner and react at 180°C for 8 h. After the reaction, the reactor was naturally cooled to room temperature to obtain a brown-yellow transparent solution, which was the initially synthesized carbon quantum dot solution. Use a 0.22 μm microporous filter membrane to remove large particles, and use a dialysis bag with a molecular weight cutoff of 1000Da for 3 days to remove unreacted small molecule impurities to obtain a purified carbon quantum dot solution, which is recorded as solution A.

[0038] S2: 1 g of polyethyleneimine was dissolved in 15 g of deionized water and stirred magnetically for 20 min to obtain solution B. 16 g of solution B was slowly added dropwise to 40 g of solution A, placed in a three-necked flask with a stirring device, and reacted at 60°C for 20 h. Then, the solution was precipitated with anhydrous ethanol for 10 h and freeze-dried to obtain a solid powder, which was the nitrogen-sulfur doped carbon quantum dot scale inhibitor for the oil field development.

[0039] Example 4 This embodiment provides a method for preparing a nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development, comprising the following steps: S1: Add 2 g of citric acid and 1 g of cysteine ​​to 60 g of deionized water, stir ultrasonically for 30 min to completely dissolve them and form a uniform transparent solution. Transfer the solution to a high-pressure reactor with a polytetrafluoroethylene liner and react at 160°C for 10 h. After the reaction, the reactor was naturally cooled to room temperature to obtain a brown-yellow transparent solution, which was the initially synthesized carbon quantum dot solution. Use a 0.22 μm microporous filter membrane to remove large particles, and use a dialysis bag with a molecular weight cutoff of 1000 Da for 3 days to remove unreacted small molecule impurities to obtain a purified carbon quantum dot solution, which is recorded as solution A.

[0040] S2: Dissolve 1 g of polyethyleneimine in 20 g of deionized water and stir magnetically for 20 min to obtain solution B. Slowly add 21 g of solution B to 50 g of solution A, place in a three-necked flask with a stirring device, and react at 80°C for 24 h. Then use anhydrous ethanol to precipitate the solution for 12 h, freeze-dry to obtain a solid powder, which is the nitrogen-sulfur doped carbon quantum dot scale inhibitor for the oil field development.

[0041] Example 5 This embodiment provides a method for preparing a nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development, comprising the following steps: S1: Add 2.2 g of citric acid and 1 g of methionine to 64 g of deionized water, stir ultrasonically for 30 min to completely dissolve them and form a uniform transparent solution. Transfer the solution to a high-pressure reactor with a polytetrafluoroethylene liner and react at 170°C for 10 h. After the reaction, the reactor was naturally cooled to room temperature to obtain a brown-yellow transparent solution, which was the initially synthesized carbon quantum dot solution. Use a 0.22 μm microporous filter membrane to remove large particles, and use a dialysis bag with a molecular weight cutoff of 1000 Da for 3 days to remove unreacted small molecule impurities to obtain a purified carbon quantum dot solution, which is recorded as solution A.

[0042] S2: Dissolve 1 g of polyethyleneimine in 15 g of deionized water and stir magnetically for 20 min to obtain solution B. Slowly add 16 g of solution B to 48 g of solution A, place in a three-necked flask with a stirring device, and react at 60°C for 24 h. Then use anhydrous ethanol to precipitate the solution for 10 h, freeze-dry to obtain a solid powder, which is the nitrogen-sulfur doped carbon quantum dot scale inhibitor for the oil field development.

[0043] Example 6 This embodiment provides a method for preparing a nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development, comprising the following steps: S1: Add 2.4 g of citric acid and 1 g of cystine to 68 g of deionized water, stir ultrasonically for 30 min to completely dissolve them and form a uniform transparent solution. Transfer the solution to a high-pressure reactor with a polytetrafluoroethylene liner and react at 180°C for 10 h. After the reaction, the reactor was naturally cooled to room temperature to obtain a brown-yellow transparent solution, which was the initially synthesized carbon quantum dot solution. Use a 0.22 μm microporous filter membrane to remove large particles, and use a dialysis bag with a molecular weight cutoff of 1000 Da for 3 days to remove unreacted small molecule impurities to obtain a purified carbon quantum dot solution, which is recorded as solution A.

[0044] S2: Dissolve 1 g of polyethyleneimine in 20 g of deionized water and stir magnetically for 20 min to obtain solution B. Slowly add 21 g of solution B to 55 g of solution A, place in a three-necked flask with a stirring device, and react at 80°C for 24 h. Then use anhydrous ethanol to precipitate the solution for 12 h, freeze-dry to obtain a solid powder, which is the nitrogen-sulfur doped carbon quantum dot scale inhibitor for the oil field development.

[0045] Performance Characterization In order to evaluate the relevant performance of the nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development, the carbon quantum dot scale inhibitor prepared in Example 6 was prepared into a 1 mg / mL solution, and its particle size was analyzed using a nanoparticle size potentiometer. The results are as follows Figure 1 As shown. Figure 1 It can be seen that the particle size of the nitrogen-doped carbon quantum dot scale inhibitor prepared by the present invention is within 1-10 nm, which is an important feature of the carbon quantum dot material, indicating the successful preparation of the carbon quantum dots.

[0046] The carbon quantum dot scale inhibitor prepared in Example 6 was prepared into a 1 mg / mL solution and tested using a fluorescence spectrometer. The results are as follows: Figure 2 As shown. Figure 2 It can be seen that the optimal emission wavelength of the carbon quantum dot scale inhibitor is 460 nm. This characteristic wavelength is located in the blue light region, which is consistent with the typical fluorescence emission range of carbon quantum dots. And the emission peak has a narrow half-peak width, indicating that the prepared carbon quantum dots have good monodispersity and size uniformity. In addition, the strong fluorescence emission at 460 nm shows that the carbon quantum dot scale inhibitor has good fluorescence properties.

[0047] The carbon quantum dot scale inhibitor prepared in Example 6 was prepared into solutions of different concentrations, and its scale inhibition performance against CaSO4 and CaCO3 was tested at 60°C. The specific test method was referred to "SY / T 5673-2020 General Technical Requirements for Oilfield Scale Inhibitors". The results are as follows: Figure 3 As shown. Figure 3It can be seen that when the concentration of the scale inhibitor is 20 mg / L, the scale inhibition rate for CaSO4 and CaCO3 can reach more than 90%, which has excellent scale inhibition performance and can be used in the field of oilfield water treatment.

[0048] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development, characterized in that: The following steps are involved: Add citric acid and thioamino acid into deionized water, stir and dissolve to form a solution; The solution is subjected to a high-temperature carbonization reaction, and after the high-temperature carbonization reaction is completed, the solution is cooled to room temperature to obtain a preliminarily synthesized carbon quantum dot solution, and the preliminarily synthesized carbon quantum dot solution is purified to obtain a purified carbon quantum dot solution; Dissolving polyethyleneimine in deionized water to prepare a polyethyleneimine solution; The polyethyleneimine solution is added dropwise to the purified carbon quantum dot solution to carry out a surface modification reaction. After the surface modification reaction is completed, the carbon quantum dot solution modified by polyethyleneimine is precipitated with anhydrous ethanol, and then freeze-dried to obtain a nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development.

2. The method for preparing the nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development according to claim 1, characterized in that: The thioamino acid is one of cystine, methionine and cysteine.

3. The method for preparing the nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development according to claim 1, characterized in that: The mass ratio of the thioamino acid to citric acid is 1:(2-2.4).

4. The method for preparing the nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development according to claim 1, characterized in that: The amount of deionized water added to the solution is 15 to 20 times the total mass of the thioamino acid and citric acid.

5. The method for preparing the nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development according to claim 1, characterized in that: The reaction temperature of the high temperature carbonization reaction is 160-180°C, and the reaction time of the high temperature carbonization reaction is 8-10h; The reaction temperature of the surface modification reaction is 60-80° C., and the reaction time of the surface modification reaction is 20-24 h.

6. The method for preparing the nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development according to claim 1, characterized in that: The purification process is as follows: The large particles were removed by microporous membrane filtration, and the unreacted small molecule impurities were removed by dialysis bag for 3 days to obtain a purified carbon quantum dot solution; The particle size of the microporous filter membrane is 0.22 μm, and the molecular weight cutoff of the dialysis bag is 1000 Da.

7. The method for preparing the nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development according to claim 1, characterized in that: The mass ratio of polyethyleneimine to deionized water in the polyethyleneimine solution is 1:(15-20).

8. The method for preparing the nitrogen-sulfur doped carbon quantum dot scale inhibitor for oil field development according to claim 1, characterized in that: The mass ratio of the polyethyleneimine solution to the purified carbon quantum dot solution is 1:(2~3).

9. A nitrogen-sulfur-doped carbon quantum dot scale inhibitor for oil field development prepared by the method for preparing the nitrogen-sulfur-doped carbon quantum dot scale inhibitor for oil field development according to any one of claims 1 to 8.

10. Use of the nitrogen-sulfur-doped carbon quantum dot scale inhibitor for oil field development prepared by the preparation method of the nitrogen-sulfur-doped carbon quantum dot scale inhibitor for oil field development as claimed in any one of claims 1 to 8 in the process of oil field development.

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