High-temperature-resistant and high-salt-resistant carbon dot-hydrogel blocking agent as well as preparation method and application thereof

Abstract

The invention relates to a high-temperature-resistant and high-salt-resistant carbon dot-hydrogel blocking agent and a preparation method and application thereof.The preparation method comprises the following steps that a reaction monomer, an initiator, an organic cross-linking agent and an inorganic cross-linking agent are added into water to be evenly mixed, and a precursor mixed solution is obtained; adding a polysaccharide polymer into the precursor mixed solution, and stirring and dissolving to obtain a hydrogel prepolymer; polymerizing and partially hydrolyzing the hydrogel prepolymer to obtain partially hydrolyzed interpenetrating network hydrogel; the partially hydrolyzed interpenetrating network hydrogel is carbonized at the constant temperature of 50-70 DEG C to form carbon dots, and the carbon dot-hydrogel blocking agent is obtained. The prepared carbon dot-hydrogel has the advantages that synthesis is green, raw materials are easy to obtain, and toxic reagents do not need to be introduced; the nano enhancement effect of the carbon dots and the physical entanglement effect of the polysaccharide polymer enable the obtained hydrogel to have high toughness and compression strength after high salinity and high-temperature aging, and the hydrogel can be used for profile control and water shutoff of high-temperature and high-salinity oil reservoirs so as to improve the recovery rate of crude oil.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil field plugging agents, in particular to a high-temperature and high-salt carbon dot-hydrogel plugging agent and a preparation method and application thereof. BACKGROUND

[0002] With the continuous deepening of oil production, the heterogeneity of the reservoir is aggravated due to long-term water injection scouring, high-permeability channels are formed between the injection wells and the production wells, and each oilfield has entered the high-water-cut and ultra-high-water-cut development stage. The water production rate of oil wells has increased significantly, and water coning, water channeling, finger-like and other phenomena have occurred in the formation. In order to improve the oil recovery, various plugging agents have been applied in oilfield sites. The gel / condensate plugging agent is the most widely used type in the field, and the hydrogel is usually prepared by using acrylamide (AM) as the main monomer through free radical polymerization to prepare polyacrylamide (PAM), which can achieve a high swelling multiple in water.

[0003] However, the exploitation conditions of many oilfields are very harsh, for example, the reservoir temperature of Tahe oilfield is as high as 130 ℃, the salinity is as high as 22×10 4 mg / L, and the reservoir temperature of Halahatang is even more than 150 ℃, and the salinity is 25×10 4 mg / L. Studies have shown that under the conditions of high temperature and high salinity, the molecular weight of the commonly used hydrogel PAM will decrease from 10 MDa to 200 kDa (decrease by more than 98%). Free radical capture experiments have confirmed that hydroxyl radicals (·OH) and peroxide radicals (ROO·) in the high-temperature aerobic environment are the main degradation driving force, leading to main chain rupture and oligomer generation; and under a higher salinity, the presence of electrolytes leads to a decrease in the repulsion between groups, the molecular chain becomes curled, the crosslinking degree decreases, the swelling degree of the gel system decreases, and it is easily broken under stress compression. For this reason, many gel plugging agents cannot effectively play a role, which has seriously affected the economic effect of oilfield development, and oilfields around the world have been plagued by this problem.

[0004] In the prior art, a certain amount of high molecular polymer (polyvinyl alcohol, guanidium gel, cellulose, etc.) is added to enhance the gel network and form a network interpenetrating structure to protect the main chain PAM. For example, patent CN119192479A adds 15% of superfine cellulose, which still has strong plugging performance under high temperature and high pressure; patent CN120383925A adds 10% of nano silicon dioxide, which transfers stress from the fragile polymer network to itself by combining with the surrounding polymer chains, thereby avoiding the rupture of the polymer chains due to excessive local stress, and thus improving the anti-breaking strength and elastic modulus of the hydrogel. In such work, the gel plugging agent is mostly enhanced in mechanical properties by additional addition of high polymer or nanoparticles, and surfactants, coagulants, toughening agents or solubilizers and other additives need to be added to maintain the interface stability. These additives not only are difficult to precisely control the multi-component ratio, but also pollute the formation. The traditional protection methods such as single network crosslinking or physical blending of nanoparticles have the problem of insufficient synergistic effect, and it is difficult to simultaneously meet the requirements of high temperature resistance, salt resistance and high strength. Moreover, under the high shear flow or complex fluid scouring in the fractured formation, such weak interaction (weak hydrogen bond or physical adsorption) is prone to interface separation, resulting in the destruction of the three-dimensional network structure and the weakening of the plugging strength, which hinders the benefit development of high temperature reservoirs. SUMMARY

[0005] The purpose of the present application is to overcome the above technical deficiencies, provide a high-temperature and high-salt carbon dot-hydrogel plugging agent, its preparation method and application, and solve the technical problem that the plugging agent is prone to damage under high temperature and high salt conditions in the prior art, resulting in poor plugging effect.

[0006] To achieve the above technical purpose, the technical solution provided by the present application is as follows: In a first aspect, the present application provides a preparation method of a high-temperature and high-salt carbon dot-hydrogel plugging agent, comprising the following steps: S1, adding reaction monomers, initiators, organic crosslinking agents and inorganic crosslinking agents into water and mixing uniformly to obtain a precursor mixed solution; S2, adding a polysaccharide polymer into the precursor mixed solution and stirring to dissolve to obtain a hydrogel prepolymer; S3, the hydrogel prepolymer is polymerized and partially hydrolyzed to obtain a partially hydrolyzed interpenetrating network hydrogel; the partially hydrolyzed interpenetrating network hydrogel is carbonized at a constant temperature of 50-70°C to form carbon dots, thereby obtaining the carbon dot-hydrogel plugging agent.

[0007] In a second aspect, the present application provides a carbon dot-hydrogel plugging agent prepared by the above preparation method.

[0008] In a third aspect, the present application provides an application of the above carbon dot-hydrogel plugging agent in oil reservoir profile control and water plugging.

[0009] Compared with the prior art, the present application has the following advantages: The present application forms carbon dots by partial hydrolysis and carbonization at low temperature, which does not damage the polymer chain and forms a high-temperature-resistant protective layer. The prepared carbon dot-hydrogel has the advantages of green synthesis and easy availability of raw materials. The preparation of carbon dots does not require the introduction of toxic reagents, which meets the requirements of green chemistry. The nanometer enhancement effect of carbon dots and the physical entanglement of polysaccharide polymers greatly improve the toughness and compressive strength of the obtained hydrogel after high salinity and high temperature aging compared with traditional gels, which can be used for profile control and water plugging in high temperature and high salinity reservoirs to improve oil recovery. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 The intermediate product of the carbon dot-hydrogel prepared by the present application is shown in the figure. Figure 2 The scanning electron microscope (SEM) of the carbon dot-hydrogel prepared by the present application is shown in the figure. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0012] In view of the defects that the plugging agent is easily damaged under high temperature and high salinity conditions, resulting in poor plugging effect, the present application provides a high-temperature and high-salt-resistant carbon dot-hydrogel plugging agent and its preparation method and application. The hydrogel plugging agent can still be compressed without damage under a stress of about 5 MPa after aging for 7 days at a salinity of 21×10 4 mg / L and a temperature of 130℃, meeting the use requirements of oil and gas exploitation in high temperature and high salinity environments.

[0013] In the first aspect, the present application provides a preparation method of a high-temperature and high-salt-resistant carbon dot-hydrogel plugging agent, comprising the following steps: S1, adding reaction monomers, initiators, organic cross-linking agents and inorganic cross-linking agents into water and mixing uniformly to obtain a precursor mixture; S2, adding polysaccharide polymers into the precursor mixture and stirring to dissolve to obtain a hydrogel prepolymer; S3, the hydrogel prepolymer is polymerized and partially hydrolyzed to obtain a partially hydrolyzed interpenetrating network hydrogel; the partially hydrolyzed interpenetrating network hydrogel is carbonized at a constant temperature of 50-70℃ to form carbon dots, and a carbon dot-hydrogel plugging agent is obtained.

[0014] Preferably, the preparation raw materials of the high-temperature and high-salt-resistant carbon dot-hydrogel plugging agent include, by mass percentage, 15-25% of reaction monomers, 0.01-0.05% of initiators, 0.01-0.05% of organic cross-linking agents, 0.20-0.60% of inorganic cross-linking agents and 0.5-2.5% of polysaccharide polymers, and the balance is water.

[0015] Preferably, in step S1, the reaction monomer comprises one or more of acrylamide, sodium acrylate, and acrylamide derivatives.

[0016] Further preferably, the acrylamide derivative comprises 2-acrylamido-2-methylpropane sulfonic acid.

[0017] Preferably, in step S1, the initiator comprises one or more of ammonium persulfate, potassium persulfate, and azobisimidozolin hydrochloride, preferably a combination of ammonium persulfate and azobisimidozolin hydrochloride.

[0018] Preferably, in step S1, the organic crosslinking agent comprises one or more of N,N-methylenebisacrylamide, methylenebisacrylamide, and ethylene glycol dimethacrylate, preferably N,N-methylenebisacrylamide.

[0019] Preferably, in step S1, the inorganic crosslinking agent comprises one or more of calcium carbonate, calcium sulfate, calcium chloride, magnesium chloride, and aluminum chloride, preferably calcium sulfate.

[0020] Preferably, in step S1, the mixing is performed at 20-32 °C until the mixture is uniform.

[0021] Preferably, in step S2, the polysaccharide polymer comprises one or more of carboxymethyl cellulose, guanidium gum, sodium alginate, sodium hyaluronate, pectin, and xanthan gum, preferably a combination of sodium alginate and carboxymethyl cellulose.

[0022] Preferably, in step S2, the stirring and dissolving are performed at 20-32 °C for 0.5-1.5 h.

[0023] Preferably, in step S3, the polymerization is performed at 50-60 °C for 3.5-4.5 h.

[0024] Preferably, in step S3, the partial hydrolysis is performed by placing the resulting interpenetrating network hydrogel in a sulfuric acid solution and sealing for 40-60 h at 20-28 °C.

[0025] Preferably, in step S3, the constant-temperature carbonization is performed for 20-48 h.

[0026] Preferably, in step S3, the carbon dot-hydrogel plugging agent is washed with ethanol and dried to obtain a carbon dot-hydrogel plugging agent powder.

[0027] Further preferably, the washing with ethanol is performed by immersing in an ethanol solution for 2-6 h, and the drying is performed at 40-55 °C for 3-5 h under vacuum.

[0028] It can be understood that the ethanol cleaning can be directly completed once or carried out in multiple times, for example, cleaned three times, each time for 2h. After freeze-drying, the dry product can be crushed to a certain particle size. After the plugging agent is made into a powder, the volume and weight are effectively reduced, which is convenient for storage and transportation.

[0029] In a second aspect, the present application provides a carbon dot-hydrogel plugging agent prepared by the above preparation method.

[0030] The carbon dot-hydrogel plugging agent of the present application is a hydrophilic reaction monomer, an initiator, an organic crosslinking agent, an inorganic crosslinking agent and a polysaccharide polymer, which are cooperatively constituted by a dynamic topological network formed by physical entanglement and a static covalent network constructed by chemical crosslinking.

[0031] In a third aspect, the present application provides an application of the above carbon dot-hydrogel plugging agent in reservoir profile control and water plugging.

[0032] Preferably, the reservoir temperature of the oil reservoir is above 100℃, and the salinity is above 10 4 mg / L.

[0033] The main action mechanism and advantages of the present application are: The present application uses a hydrophilic reaction monomer and a polysaccharide polymer as main raw materials, and forms a double network structure of a dynamic topological network formed by physical entanglement and a static covalent network constructed by chemical crosslinking under the action of an initiator, an organic crosslinking agent and an inorganic crosslinking agent, thereby effectively enhancing the stability thereof; and the polysaccharide polymer is carbonized in situ at low temperature after acidification ring-opening to form carbon dots, which not only do not destroy the polymer chain but also form a high-temperature-resistant protective layer, thereby strengthening the network structure, effectively enhancing the anti-aging ability and structural stability of the gel network, and endowing the hydrogel with excellent temperature-resistant, salt-resistant and anti-aging properties.

[0034] The present application will be further described in detail through specific examples. In order to avoid redundancy, the test standards or methods used are described as follows: (1) Maximum swelling multiple performance evaluation method: under the conditions of a salinity of 21x10 4 mg / L and a temperature of 130℃, different gels are placed in a reaction kettle for aging, and after every 2 days, the surface moisture is wiped off and weighed, and the swelling multiple is calculated. With the progress of aging, the swelling multiple of the gel will show a trend of first increasing and then decreasing, and the extreme point is defined as the maximum swelling multiple.

[0035] (2) Mechanical property evaluation method: The compressibility of the gel was tested at room temperature using a universal testing machine (maximum compressive force 2000 N). Following existing literature methods, the compressive stress test was conducted by moving the mold at a constant rate of 50 mm / min. The gel used in the test was molded into a cylinder with a height of 10 mm and a diameter of 20 mm in the mold, and the strain test range was set to 0–98%. Different types of hydrogels were selected and placed in a reaction vessel for aging treatment (mineralization of 21 × 10⁻⁶). 4 The compression curves of the hydrogel (mg / L, temperature 130 ℃) were measured before aging and 7 days after aging. The maximum stress value that the material can withstand during compression corresponds to the peak point of the stress in the curve, which directly reflects the ultimate bearing capacity of the hydrogel under compressive load and is defined as the compressive strength of different products.

[0036] Example 1 A method for preparing a high-temperature, high-salt resistant carbon dot-hydrogel blocking agent, see [link to relevant documentation]. Figure 1 This includes the following steps: S1, 20% acrylamide was dissolved in deionized water by stirring. After it was completely dissolved, 0.4% calcium sulfate, 0.04% potassium persulfate and 0.01% N,N-methylenebisacrylamide were added in sequence. The mixture was magnetically stirred at 30 °C until homogeneous to obtain the precursor mixture. S2, then 1.5% polysaccharide polymer (sodium alginate and carboxymethyl cellulose in a mass ratio of 1:1) was added to the precursor mixture, and the mixture was stirred and dissolved for 1 h to form a uniform hydrogel prepolymer. S3. After pouring the hydrogel prepolymer into a cell culture plate, it was transferred to a 60 ℃ oven for constant temperature reaction for 4 h to obtain an interpenetrating network hydrogel (IPN). Then, the obtained IPN was placed in a 3 mol / L sulfuric acid solution and sealed and soaked at room temperature for 48 h to achieve partial hydrolysis of the polysaccharide polymer. Subsequently, it was transferred to a 60 ℃ oven and carbonized at a constant temperature for 24 h to form carbon dots, thus obtaining a carbon dot-hydrogel blocking agent (CIPN).

[0037] To facilitate storage and transportation, the obtained sealing agent can be made into powder. Specifically, the carbon dot-hydrogel sealing agent is cut into small pieces and soaked in ethanol for 4 hours for cleaning. After soaking, it is taken out and dried in a vacuum drying oven at 50 ℃ for 4 hours. After drying, it is pulverized to finally obtain a high-temperature and high-salt resistant carbon dot-hydrogel sealing agent powder.

[0038] See Figure 1 The interpenetrating network hydrogel prepared by this invention is a light yellow transparent gel. After acidification and partial hydrolysis, it becomes basically colorless and transparent. After carbonization, it forms a black carbon dot-hydrogel sealing agent.

[0039] Example 2 The only difference from Example 1 is that sodium alginate was used for all polysaccharide polymers in step S2, while the other steps and conditions were the same as in Example 1.

[0040] Example 3 The only difference from Example 1 is that the polysaccharide polymer in step S2 is entirely carboxymethyl cellulose, while the other steps and conditions are the same as in Example 1.

[0041] Comparative Example 1 The only difference from Example 1 is that the polysaccharide polymer is completely removed in step S2, while the other steps and conditions are the same as in Example 1.

[0042] The expansion ratio and compressive strength of the hydrogels obtained in Example 1 (CIPN), Example 2 (without carboxymethyl cellulose), Comparative Example 1 (without sodium alginate) and Comparative Example 2 (without polysaccharide polymer) were measured respectively. The test results are shown in Table 1.

[0043] Table 1. Performance evaluation of hydrogels obtained in Examples 1-2 and Comparative Examples 1-2

[0044] Note: A compressive strength of 0 MPa indicates that the structure of the gel was completely destroyed after 7 days of aging and could not be tested.

[0045] As shown in Table 1, the hydrogel in Comparative Example 1 without the addition of polysaccharide polymer was decomposed by sulfuric acid during acidification and could not be further carbonized, so the expansion factor was 0. However, the addition of polysaccharide polymer in Examples 1-3 not only protected the main structure of the gel from being destroyed during acidification, but also formed in-situ carbon dots. The gels in Example 2 containing only sodium alginate and Example 3 containing only carboxymethyl cellulose had much better strength after aging than those in Comparative Example 1. Their compressive strength was significantly improved (compressive strength ≥3.9 MPa before aging) and their anti-aging properties were greatly improved (compressive strength ≥3.7 MPa after 7 days of aging). Among them, the carbon dot hydrogel (CIPN) prepared by the combination of sodium alginate and carboxymethyl cellulose in Example 1 performed the best, with a compressive strength of 4.9 MPa before aging, 4.8 MPa after 7 days of aging, and 4.2 MPa after 31 days of aging. This shows that polysaccharide polymer can effectively enhance the anti-aging ability and structural stability of the gel network through in-situ carbon dots.

[0046] Example 4 The only difference from Example 1 is that the amount of polysaccharide polymer in step S2 is adjusted to 0.5%, 1.0%, 2% and 2.5% respectively, wherein the polysaccharide polymer is a mixture of sodium alginate and carboxymethyl cellulose in a mass ratio of 1:1. Other steps and conditions are the same as in Example 1.

[0047] The expansion ratio and compressive strength of the obtained hydrogel were measured, and the test results are shown in Table 2.

[0048] Table 2. Evaluation of hydrogel properties with different polysaccharide polymer contents

[0049] Note: The group with a content of 1.5% is Example 1.

[0050] As shown in Table 2, the content of polysaccharide polymer (sodium alginate and carboxymethyl cellulose 1:1) plays a key regulatory role in the performance of carbon dot hydrogels: when the content is 0.5% and 1.0%, the network stability is relatively poor due to insufficient carbon dot formation, and the strength drops to zero after 31 days of aging. This is suitable for short-term plugging scenarios with high initial strength requirements. When the content is 1.5% (Example 1), the carbon dots formed by in-situ carbonization of polysaccharide uniformly strengthen the network, resulting in an expansion ratio of 3.1. The strength before aging is 4.9 MPa, which still reaches 4.8 MPa after 7 days and 4.2 MPa after 31 days, achieving the optimal synergy of expansion, mechanical and anti-aging properties. When the content is 2.0% and 2.5%, the polysaccharide aggregation leads to slightly uneven carbon dot dispersion, network density imbalance, and a sharp drop in initial strength, but the long-term strength is well preserved. In summary, the amount of polysaccharide polymer used in this invention can be selected from 0.5% to 2.5% depending on the situation. Considering the cost, it is preferably 0.5% to 1.5%. Further considering the overall performance, it is more preferably 1.5%. At this point, carbon dots can effectively strengthen the network structure and give the hydrogel excellent temperature resistance, salt resistance and anti-aging properties.

[0051] Comparative Example 2 A method for preparing a polyacrylamide hydrogel includes the following steps: 20% acrylamide was dissolved in deionized water by stirring. After it was completely dissolved, 0.04% potassium persulfate and 0.01% N,N-methylenebisacrylamide were added. The mixture was magnetically stirred at 30 °C until it became clear and transparent. The solution was then poured into a mold and transferred to a 60 °C oven for constant temperature reaction for 4 h to prepare polyacrylamide hydrogel (PAM).

[0052] Comparative Example 3 Compared with Comparative Example 2, the only difference was that acrylamide was replaced with a mixture of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid in a mass ratio of 1:1. All other steps and conditions were the same as in Comparative Example 2, and hydrogel PAA was obtained.

[0053] Comparative Example 4 Interpenetrating network hydrogel (IPN) prepared in Example 1.

[0054] The expansion ratio and compressive strength of the hydrogels obtained in Comparative Examples 2-4 were tested and compared with those of the hydrogel obtained in Example 1. The results are shown in Table 3. Simultaneously, the hydrogel obtained in Example 1 was subjected to electron microscopy scanning, and the results are as follows: Figure 2 As shown.

[0055] Table 3 Comparison of the properties of hydrogels obtained in Comparative Examples 2-4 and hydrogels obtained in Example 1

[0056] Depend on Figure 2 As shown in Table 3, the carbon dot hydrogel of the present invention exhibits a rich three-dimensional network structure—this is the result of the synergistic cross-linking of carbon dots formed by in-situ carbonization of polysaccharide polymers and gel networks. In contrast, the PAM and PAA hydrogels of Comparative Examples 2 and 3, which did not introduce carbon dots, although their initial expansion performance was acceptable, completely disintegrated their three-dimensional network after aging, and their compressive strength dropped sharply to 0. In order to increase the temperature and salt resistance of the hydrogel, Comparative Example 3 added the commonly used functional monomer 2-acrylamido-2-methylpropanesulfonic acid to Comparative Example 2, but it did not have a beneficial effect. The uncarbonized IPN hydrogel of Comparative Example 4 showed improved mechanical properties before aging, but due to the lack of the reinforcing effect of carbon dots, its structure also failed after aging.

[0057] The dense network framework of the carbon dot hydrogel of this invention not only endows it with excellent mechanical strength, but also enables it to effectively resist temperature and salinity environments thanks to the special role of carbon dots: the network structure is stable and does not disintegrate at high temperatures, avoiding performance failure caused by thermally induced chain relaxation; in high-salt environments, the uniform dispersion of carbon dots and the precise control of network pores can inhibit ion-induced gel aggregation or dehydration shrinkage, ensuring stable expansion performance, fully demonstrating the significant enhancing effect of polysaccharide polymer-derived carbon dots on the temperature and salt resistance and anti-aging properties of hydrogels.

[0058] Comparative Example 5 Compared with Example 1, the only difference is that sodium alginate and acrylamide are added to deionized water at the same time, while the other steps and conditions are the same as in Example 1.

[0059] The results showed that adding sodium alginate first would hinder the construction of a uniform prepolymer system, which would lead to uneven dispersion of carbon dots in the gel matrix, making it impossible to form a stable synergistic network, and ultimately significantly weakening the temperature and salt resistance core properties of the carbon dot hydrogel.

[0060] In summary, the high-temperature and high-salt resistant carbon dot-hydrogel prepared by this invention has the advantages of green synthesis and readily available raw materials. For example, the polysaccharide raw materials (such as carboxymethyl cellulose) are biodegradable, and the preparation of carbon dots does not require the introduction of toxic reagents, which meets the requirements of green chemistry. The nano-reinforcing effect of carbon dots and the physical entanglement of polysaccharide polymers significantly improve the toughness and compressive strength of the gel after high mineralization and high-temperature aging compared with traditional gels. At a mineralization of 21 × 10⁻⁶, the hydrogel exhibits significantly improved toughness and compressive strength. 4 mg / L, it can expand to 2 to 4 times at 130℃, and retain its original shape after 31 days of aging. It can be used for profile control and water shut-off in high-temperature and high-salinity oil reservoirs to improve crude oil recovery.

[0061] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a high-temperature and high-salt resistant carbon dot-hydrogel plugging agent, characterized in that, The preparation method comprises the following steps: S1, adding reaction monomers, initiators, organic cross-linking agents and inorganic cross-linking agents into water to mix uniformly to obtain a precursor mixed solution; S2, adding a polysaccharide polymer into the precursor mixed solution to stir and dissolve to obtain a hydrogel pre-polymer; S3, the hydrogel pre-polymer is polymerized and partially hydrolyzed to obtain a partially hydrolyzed interpenetrating network hydrogel; the partially hydrolyzed interpenetrating network hydrogel is carbonized at a constant temperature of 50-70 ℃ to form carbon dots, thereby obtaining a carbon dot-hydrogel plugging agent.

2. The method for preparing high temperature and high salt resistant carbon dots-hydrogel plugging agent according to claim 1, characterized in that, The preparation raw materials of the high-temperature and high-salt resistant carbon dot-hydrogel plugging agent, by mass percentage, comprise: 15-25% of reaction monomers, 0.01-0.05% of initiators, 0.01-0.05% of organic cross-linking agents, 0.20-0.60% of inorganic cross-linking agents and 0.5-2.5% of polysaccharide polymers, and the balance is water.

3. The method for preparing high temperature and high salt resistant carbon dots-hydrogel plug according to claim 1, characterized in that, In step S1, the reaction monomers comprise one or more of acrylamide, sodium acrylate and acrylamide derivatives; and / or, The initiators comprise one or more of ammonium persulfate, potassium persulfate and azobisimidozolin hydrochloride; and / or, The organic cross-linking agents comprise one or more of N,N-methylene bisacrylamide, methylene bisacrylamide and ethylene glycol dimethyl acrylate; and / or, The inorganic cross-linking agents comprise one or more of calcium carbonate, calcium sulfate, calcium chloride, magnesium chloride and aluminum chloride.

4. The preparation method of the high-temperature and high-salt resistant carbon dot-hydrogel blocking agent according to claim 1, characterized in that, In step S1, the uniform mixing is stirring to a uniform state at 20-32 ℃.

5. The preparation method of the high-temperature and high-salt resistant carbon dot-hydrogel blocking agent according to claim 1, characterized in that, In step S2, the polysaccharide polymer comprises one or more of carboxymethyl cellulose, guanidium gum, sodium alginate, sodium hyaluronate, pectin and xanthan gum.

6. The preparation method of the high-temperature and high-salt resistant carbon dot-hydrogel blocking agent according to claim 1, characterized in that, In step S2, the stirring and dissolving is stirring at 20-32 ℃ for 0.5-1.5 h.

7. The preparation method of the high-temperature and high-salt resistant carbon dot-hydrogel blocking agent according to claim 1, characterized in that, In step S3, the polymerization is reacting at 50-60 ℃ for 3.5-4.5 h; and / or, The partial hydrolysis is placing the interpenetrating network hydrogel obtained by polymerization into a sulfuric acid solution, and sealing and soaking at 20-28 ℃ for 40-60 h.

8. The preparation method of the high-temperature and high-salt resistant carbon dot-hydrogel blocking agent according to claim 1, characterized in that, In step S3, the constant temperature carbonization time is 20-48 h; and / or, The carbon dot-hydrogel plugging agent is cleaned with ethanol and dried to obtain a carbon dot-hydrogel plugging agent powder.

9. The carbon dot-hydrogel plugging agent prepared by the preparation method in any one of claims 1-8.

10. The application of the carbon dot-hydrogel plugging agent in claim 9 in reservoir profile control and water plugging.

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