Block-grafting-hyperbranched volume expansion type profile control agent and preparation method thereof

Abstract

The invention relates to the technical field of oilfield chemistry, and provides a block-grafting-hyperbranched volume expansion type profile control agent and a preparation method thereof. The profile control agent comprises the following raw materials in parts by mass: 10 to 30 parts of a polymer main chain monomer, 2 to 20 parts of a block comonomer, 1 to 10 parts of a grafting monomer, 0.5 to 2 parts of a supramolecular core cross-linking agent, 0.1 to 0.5 part of a water quality stabilizer, 0.1 to 0.5 part of a chain extender, 0.1 to 0.5 part of a molecular structure stabilizer, 0.01 to 0.1 part of an initiator and 35 to 75 parts of water. Compared with a traditional linear polymer structure, molecular chain curl cannot be generated at the high temperature, block and grafting of the salt-tolerant monomer and the rigid structure are carried out, the salt tolerance of the product is greatly improved, the temperature resistance can reach 180 DEG C or above, and the salt tolerance reaches 350,000 ppm or above.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemistry, in particular to a block-graft-hyperbranched bulking profile control agent and a preparation method thereof. Background Art

[0002] During oilfield development, various factors contribute to the development of reservoirs: natural reservoir heterogeneity and fractures; artificial fractures and complex fracture networks created by fracturing; increased reservoir permeability due to crude oil recovery; and the orientation of fluids with minimal flow resistance. In the middle and late stages of oilfield development, water flow pathways of varying degrees develop within the reservoir, leading to inefficient and ineffective circulation of injected water. This significantly increases the water content of produced fluids, significantly reduces the efficiency of water injection in displacing crude oil in the formation, and significantly reduces production benefits. In these situations, oilfields typically employ profile control to address reservoir permeability imbalances, increase water injection sweep, and thus enhance water flooding efficiency. Profile control can seal high permeability layers and reduce their water absorption, thereby improving the reservoir's water absorption profile. This allows subsequent injected water to enter medium- and low-permeability layers and recover the crude oil therein, increasing oil recovery, reducing the water content of produced oil, and improving development outcomes.

[0003] However, for high-temperature reservoirs, commonly used modified polyacrylamide profile control materials experience severe performance degradation or even failure under reservoir conditions, hindering the effectiveness and long-term effectiveness of profile control in high-temperature, high-salinity reservoirs. For high-temperature, high-salinity reservoirs, the material's heat and salt resistance are crucial factors in the effectiveness and long-term effectiveness of profile control measures.

[0004] In existing technologies, profile control agents primarily include inorganic, gel, and pre-crosslinked particle-based agents. Inorganic profile control agents were an early adopter, employing a physical plugging mechanism that prioritizes the compatibility between particle size and pore throats. Commonly used products include cement, clay, and sediment particles. These products suffer from poor fluidity, making them difficult to transfer deep into the formation, and, after solidification, bypassing the injected water, shortening the waterflooding time. While inorganic profile control agents offer high plugging strength, they can easily cause permanent formation damage and hinder deep profile control.

[0005] Gel-type profile control agents are a solid or semi-solid colloidal system with a spatial network structure. They are mainly composed of polymers and supramolecular core crosslinkers. Polymers are formed by the polymerization of monomers. Generally, polymer monomers and supramolecular core crosslinkers are mixed in solution. The gel system can remain stable at high temperatures, but the gelation time of this type of gel system is relatively long, and it will also produce more heat loss, and its viscosity will also decrease over time. Gel-type profile control agents have poor temperature resistance, and gel formation is greatly affected by formation water quality. They have poor shear resistance and are difficult to inject deep into the reservoir. These problems make it difficult to meet the application requirements of reservoir pyrometry oilfields with complex water quality environments.

[0006] Pre-crosslinked particles have been a rapidly developing profile control agent in recent years. These water-swelling plugging agents are primarily composed of molecular monomers, a supramolecular core crosslinker, and other polymers. These products offer advantages such as easy injection, high strength, and long-lasting plugging. As oil and gas exploration and development progress deeper into the strata, the product's heat and salt resistance are a major limitation to its application and a key area of development. While existing pre-crosslinked particles offer some heat and salt resistance, their effectiveness is limited, presenting certain drawbacks for deep-seated oil and gas extraction. Summary of the Invention

[0007] The purpose of the present invention is to provide a block-grafted-hyperbranched bulking profile control agent, whose molecular structure is a self-crosslinking, dendritic divergent structure. Compared with the traditional linear polymer structure, it will not produce molecular chain curling at high temperature. In addition, the blocking and grafting of salt-resistant monomers and rigid structures are carried out, which greatly improves the salt resistance of the product. It can withstand temperatures above 180°C and salt resistance above 350,000 ppm.

[0008] Another object of the present invention is to provide a method for preparing a block-graft-hyperbranched bulking profile control agent, in which a dendritic supramolecular polymer profile control agent with a self-crosslinking structure is prepared by block, grafting and hyperbranched copolymerization of temperature-resistant and salt-resistant monomers.

[0009] The technical solution of the present invention is: In one aspect, the present invention provides a block-graft-hyperbranched bulking profile control agent, the molecular structure of which is shown in Formula 1: Formula 1; Wherein, M is a supramolecular core crosslinker; A1, A2 and A3 are small molecular polymers prepolymerized from graft copolymer monomers; n is 15%-25%; The grafted comonomer includes a grafted monomer and a block comonomer, the grafted monomer is one or more of allyl sulfonic acid, sodium allyl sulfonate, methallyl sulfonic acid, sodium methallyl sulfonate, allyl phosphoric acid, sodium allyl phosphate, 2-acrylamido-2-methylpropanesulfonic acid, and sodium 2-acrylamido-2-methylpropanesulfonate; the block comonomer is one or more of 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamido-2-methylpropanesulfonate, sodium p-styrenesulfonate, and N-vinyl pyrrolidone.

[0010] Furthermore, the profile control agent raw materials include, by mass, 10-30 parts of polymer main chain monomers, 2-20 parts of block copolymer monomers, 1-10 parts of graft monomers, 0.5-2 parts of supramolecular core crosslinkers, 0.1-0.5 parts of water quality stabilizers, 0.1-0.5 parts of chain extenders, 0.1-0.5 parts of molecular structure stabilizers, 0.01-0.1 parts of initiators and 35-75 parts of water.

[0011] Furthermore, the polymer main chain monomer is one or more of acrylamide and acrylic acid.

[0012] Furthermore, the water quality regulator is one or more of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetic acid, hydroxyethylidene diphosphonic acid, and sodium hydroxyethylidene diphosphonate.

[0013] Furthermore, the chain extender is one or more of 1,1'-azobis(N,N-dimethylformamide), ethylenediamine, ethylene glycol, 1,4-butanediol, 2,2-dihydroxymethylbutanoic acid, 2,2-dihydroxymethylpropionic acid, 3-hydroxyethyloxyethyl-1-hydroxyethylphenylene diether, 4,4'-methylenebis(2,6-diethylaniline), and 4,4'-methylenebis(2-ethyl)aniline.

[0014] Furthermore, the molecular structure stabilizer is one or more of urea, ammonium citrate, triammonium citrate, and thiourea.

[0015] Furthermore, the initiator is one or more of ammonium persulfate, sodium bisulfite, potassium persulfate, sodium sulfite, sodium persulfate, ammonium sulfite, hydrogen peroxide, azobisisobutyronitrile imidazoline, and azobisisobutyronitrile imidazoline hydrochloride.

[0016] On the other hand, the present invention provides a method for preparing a block-grafted-hyperbranched body swelling profile control agent, comprising the following steps: S1. dissolving a grafted monomer in water, adding a pH regulator to adjust the pH of the solution, heating and stirring, and adding an initiator to maintain the temperature for polymerization to obtain a grafted oligomer aqueous solution; S2. dissolving a polymer main chain monomer and a block comonomer in water, adding a pH regulator to adjust the pH of the solution to obtain a main chain-block comonomer mixed solution; S3. adding a water quality stabilizer, a chain extender, a molecular structure stabilizer and an initiator to the main chain-block comonomer mixed solution, stirring and mixing, adding the grafted oligomer aqueous solution, and stirring evenly to obtain a copolymerization reaction precursor mixed solution; S4. deoxygenating the copolymerization reaction precursor mixed solution with nitrogen, and obtaining polymer micelles after standing for reaction; S5. extruding, drying, shearing and granulating the polymer micelles to obtain the profile control agent.

[0017] Furthermore, the pH adjuster is one or more of sodium hydroxide, triethanolamine, and ammonia water.

[0018] Furthermore, the temperature of the heating and stirring in the above S1 is 58-62°C.

[0019] Furthermore, the time for nitrogen deoxygenation in the above S4 is 25-35 minutes.

[0020] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects: 1. The molecular structure of the profile control agent of the present invention is a self-crosslinking, dendritic dispersed structure. Compared with the traditional linear polymer structure, it will not produce molecular chain curling at high temperatures. The sulfonic acid group, phosphoric acid group, benzene ring, and polycyclic structure used can also improve the temperature resistance of the molecular structure of the profile control agent, and has good heat resistance.

[0021] 2. The profile control agent of the present invention has salt-tolerant monomers and rigid structures blocked and grafted in its molecular structure, making the profile control agent insensitive to cations and not curling, thereby greatly improving the salt resistance of the profile control agent.

[0022] 3. The profile control agents are prepared using hydrophilic organic materials, which are polymerized to form self-crosslinked, dendritic supramolecular structures. When exposed to water, the molecular chains expand and swell without dissolving, forming large-sized expanded bodies, thereby improving the product's blocking effect on large cracks and large pores.

[0023] 4. Due to the improvement of heat resistance and salt resistance, the swollen body formed by the profile control agent absorbing water has good stability in the high temperature and high salt environment of the reservoir and is not easy to degrade. Therefore, the profile control agent provided by the present invention can have a longer profile control validity period. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 Schematic diagram of the finished product of the profile control agent of the present invention; Figure 2 This is a SEM analysis diagram of the profile control agent of the present invention; Figure 3 TG-DTA analysis chart of the profile control agent of the present invention; Figure 4 This is a data diagram of the long-term effectiveness evaluation of the profile control agent of the present invention and the comparative example at different temperatures; Figure 5 This is a data diagram of the swelling performance of the profile control agent of the present invention at different salt concentrations. DETAILED DESCRIPTION

[0026] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to specific embodiments.

[0028] In existing technologies, commonly used organic profile control agents include gels and pre-crosslinked particles, all based on linear polyacrylamide (LPA). Under the synergistic destructive mechanism of high temperature and high salinity, LPA materials exhibit poor heat and salt stability. For high-temperature reservoirs, commonly used modified PPA-based profile control materials experience severe performance degradation or even failure under these conditions, hindering the effectiveness and long-term effectiveness of profile control in high-temperature, high-salinity reservoirs.

[0029] On the one hand, the carbon-carbon backbone of polyacrylamide is susceptible to thermal oxidative breakage at high temperatures, especially in the presence of dissolved oxygen or metal ions such as Fe 2+ / Fe 3+ When the free radical chain reaction is accelerated, the molecular weight will be degraded. On the other hand, the amide group (-CONH2) is easily hydrolyzed at high temperature to form a carboxyl group (-COOH), which makes the molecular chain negatively charged and aggravates the reaction with divalent cations such as Ca 2+ Mg 2+ In addition, HPAM hydrolysis introduces carboxylic acid groups (-COO - ) can improve viscosity, but in a high salt environment, the double layer will be compressed, causing the molecular chains to curl up and the viscosity to drop sharply, which is the salt-sensitive effect. The divalent ions combine with the carboxyl groups to form precipitates, further destroying the molecular structure.

[0030] The present invention optimizes the molecular structure and the functional group structure, takes a hyperbranched structure inner monomer as the molecular core, and takes a free radical polymerization reaction as the basis. It adopts a highly active polymer main chain monomer and a block polymerization monomer with a temperature-resistant structure and a rigid unit to form a self-crosslinked hyperbranched structure molecule. Under the action of a chain extender and high-temperature free radicals, a graft copolymerization reaction occurs with a grafted oligomer formed by a pre-reaction of the grafted monomer, and finally copolymerizes to form a polyacrylamide derivative with a main chain sulfonic acid group and a rigid structure block, a terminal sulfonic acid group grafted, and a hyperbranched structure modification, thereby improving the salt resistance of the profile control material.

[0031] Based on the basic theoretical design concept of the present invention, a method for preparing a block-graft-hyperbranched bulking profile control agent is proposed, comprising the following steps: S1. Dissolve 1-10 parts of the grafting monomer in 2-10 parts of water by mass, add a pH adjuster to adjust the pH of the solution, heat to 58-62 ° C, stir, and add 0.01-0.1 parts of an initiator to maintain the temperature and polymerize to obtain an aqueous solution of a grafted oligomer, wherein the grafting monomer is one or more of allyl sulfonic acid, sodium allyl sulfonate, methallyl sulfonic acid, sodium methallyl sulfonate, allyl phosphoric acid, sodium allyl phosphate, 2-acrylamido-2-methylpropanesulfonic acid, and sodium 2-acrylamido-2-methylpropanesulfonate; the pH adjuster is one or more of sodium hydroxide, triethanolamine, and ammonia; and the initiator is one or more of ammonium persulfate, sodium bisulfite, potassium persulfate, sodium sulfite, sodium persulfate, ammonium sulfite, hydrogen peroxide, azobisisobutyronitrile imidazoline, and azobisisobutyronitrile imidazoline hydrochloride; S2. By mass fraction, 10-30 parts of a polymer backbone monomer and 2-20 parts of a block comonomer are dissolved in 20-60 parts of water, and a pH adjuster is added to adjust the pH of the solution to obtain a backbone-block comonomer mixed solution, wherein the polymer backbone monomer is one or more of acrylamide and acrylic acid, and the block comonomer is one or more of 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamido-2-methylpropanesulfonate, sodium p-styrenesulfonate, and N-vinyl pyrrolidone; S3. Add 0.5-2 parts of supramolecular core crosslinker, 0.1-0.5 parts of water quality stabilizer, 0.1-0.5 parts of chain extender, 0.1-0.5 parts of molecular structure stabilizer and 0.01-0.2 parts of initiator to the main chain-block copolymer monomer mixed solution by mass, stir and mix, add grafted oligomer aqueous solution, stir evenly to obtain a copolymerization reaction precursor mixed solution, wherein the water quality regulator is ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetic acid, hydroxyethylidene diphosphonic acid, hydroxyethylidene diphosphine The chain extender is one or more of 1,1'-azobis(N,N-dimethylformamide), ethylenediamine, ethylene glycol, 1,4-butanediol, 2,2-dihydroxymethylbutyric acid, 2,2-dihydroxymethylpropionic acid, 3-hydroxyethyloxyethyl-1-hydroxyethylphenylenediether, 4,4'-methylenebis(2,6-diethylaniline), 4,4'-methylenebis(2-ethyl)aniline; the molecular structure stabilizer is one or more of urea, ammonium citrate, triammonium citrate, and thiourea; S4. Deoxygenate the copolymerization precursor mixture with nitrogen for 25-35 min, and allow the reaction to proceed to obtain polymer micelles; S5. Extruding, drying, shearing, and granulating the polymer micelles to obtain a profile control agent.

[0032] It should be noted that the supramolecular core crosslinker is CL25 produced by Sichuan Vivoton Petroleum Technology Co., Ltd. In the above steps, the pH regulator is added to adjust the pH of the solution to neutral.

[0033] It should also be noted that in step S5, the polymer micelles are granulated, dried, and crushed to obtain a powder microsphere profile control agent product; the polymer micelles are granulated, roller-milled, and sieved to obtain a granular profile control agent product.

[0034] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0035] Example 1 This embodiment provides a method for preparing a block-graft-hyperbranched bulking profile control agent, comprising the following steps: S1. Dissolve 2 parts of sodium allyl sulfonate and 2 parts of sodium allyl phosphate in 8 parts of water, add 0.1 parts of triethanolamine to adjust the solution, heat to 60 ° C with stirring, and add 0.05 parts of an initiator prepared by mixing 20% ammonium persulfate and sodium bisulfite in a mass ratio of 3:1. Heat and polymerize to obtain an aqueous solution of grafted oligomers; S2. In parts by mass, 15 parts of acrylamide, 5 parts of acrylic acid, 5 parts of 2-acrylamido-2-methylpropanesulfonic acid and 2 parts of N-vinyl pyrrolidone were dissolved in 56.8 parts of water, and 2.5 parts of sodium hydroxide were added to adjust the pH of the solution to obtain a main chain - block comonomer mixed solution; S3. To the main chain-block comonomer mixed solution, 0.8 parts of a supramolecular core crosslinker CL25, 0.2 parts of a water stabilizer prepared by mixing disodium ethylenediaminetetraacetate and oxalic acid in a mass ratio of 2:1, 0.2 parts of 1,1'-azobis(N,N-dimethylformamide), 0.5 parts of urea, and 0.05 parts of an initiator prepared by mixing 20% ammonium persulfate and sodium bisulfite in a mass ratio of 3:1 were added, by weight, and then the grafted oligomer aqueous solution was added and stirred to obtain a copolymerization precursor mixture. S4. The copolymerization precursor mixture was deoxygenated with nitrogen for 30 min and allowed to stand for reaction to obtain polymer micelles; S5. Extruding, drying, shearing, granulating, drying, and crushing the polymer micelles to obtain a powdered microsphere profile control agent.

[0036] Example 2 This embodiment provides a method for preparing a block-graft-hyperbranched bulking profile control agent, comprising the following steps: S1. Dissolve 2 parts of sodium methyl allyl sulfonate and 3 parts of sodium allyl phosphate in 10 parts of water, add 0.1 parts of triethanolamine to adjust the pH of the solution, heat to 60°C with stirring, and add 0.05 parts of an initiator prepared by mixing 20% ammonium persulfate and sodium bisulfite in a mass ratio of 3:1. Heat and polymerize to obtain an aqueous solution of grafted oligomers. S2. In parts by mass, 15 parts of acrylamide, 10 parts of sodium 2-acrylamido-2-methylpropanesulfonate, 2 parts of sodium p-styrenesulfonate and 2 parts of N-vinyl pyrrolidone were dissolved in 54.1 parts of water, and 2 parts of sodium hydroxide were added to adjust the pH of the solution to obtain a main chain - block comonomer mixed solution; S3. To the main chain-block comonomer mixed solution, 0.8 parts of a supramolecular core crosslinker CL25, 0.2 parts of a water stabilizer prepared by mixing disodium ethylenediaminetetraacetate and oxalic acid in a mass ratio of 2:1, 0.2 parts of 1,1'-azobis(N,N-dimethylformamide), 0.5 parts of urea, and 0.05 parts of an initiator prepared by mixing 20% ammonium persulfate and sodium bisulfite in a mass ratio of 3:1 were added, by weight, and then the grafted oligomer aqueous solution was added and stirred to obtain a copolymerization precursor mixture. S4. The copolymerization precursor mixture was deoxygenated with nitrogen for 30 min and allowed to stand for reaction to obtain polymer micelles; S5. Extruding, drying, shearing, granulating, roller-milling, and screening the polymer micelles to obtain a granular profile control agent.

[0037] Example 3 This embodiment provides a method for preparing a block-graft-hyperbranched bulking profile control agent, comprising the following steps: S1. Dissolve 2.5 parts of sodium methyl allyl sulfonate and 25 parts of allyl phosphoric acid in 10 parts of water, add 0.1 parts of triethanolamine to adjust the pH of the solution, heat to 60°C with stirring, and add 0.05 parts of an initiator prepared by mixing 20% ammonium persulfate and ammonium sulfite in a mass ratio of 3:1. Polymerize at this temperature to obtain an aqueous solution of a grafted oligomer. S2. In parts by mass, 10 parts of acrylamide, 15 parts of 2-acrylamido-2-methylpropanesulfonic acid and 2 parts of sodium p-styrenesulfonate were dissolved in 53.1 parts of water, and 3 parts of sodium hydroxide were added to adjust the pH of the solution to obtain a main chain - block comonomer mixed solution; S3. To the main chain-block comonomer mixed solution, 0.8 parts of a supramolecular core crosslinker CL25, 0.1 parts of a water stabilizer prepared by mixing ethylenediaminetetraacetic acid and hydroxyethylidene diphosphonic acid in a mass ratio of 1:1, 0.2 parts of 1,1'-azobis(N,N-dimethylformamide), 0.2 parts of thiourea, and 0.05 parts of an initiator prepared by mixing 20% ammonium persulfate and ammonium sulfite in a mass ratio of 3:1 were added, by weight, and then the grafted oligomer aqueous solution was added and stirred to obtain a copolymerization precursor mixture. S4. The copolymerization precursor mixture was deoxygenated with nitrogen for 30 min and allowed to stand for reaction to obtain polymer micelles; S5. Extruding, drying, shearing, granulating, roller-milling, and screening the polymer micelles to obtain a granular profile control agent.

[0038] Test Example 1 This test example 1 uses the granular profile control agent prepared in Example 2 and conducts a temperature resistance test on it. The finished product is as follows: Figure 1 shown.

[0039] The prepared granular profile control agent was subjected to hyperbranched morphology analysis, and its SEM analysis diagram is shown as follows: Figure 2 As shown, the three-dimensional network cross-linked structure between and within the molecules indicates that the product forms a three-dimensional branched cross-linked structure through the hyperbranching reaction, and the hyperbranched structure is successfully achieved. At the same time, it can be seen from the figure that its molecular structure is dendritic, which meets the design requirements of the present invention.

[0040] The prepared granular profile control agent was subjected to thermogravimetric analysis, and the TG-DTA analysis results are as follows: Figure 3 The results show that the product structure has a temperature resistance of more than 300℃.

[0041] The profile control agent is placed in water or brine, and after it has completely absorbed water and swelled, it is transferred to a high-temperature aging tank for a high-temperature aging test. The shelf life of the profile control agent is evaluated based on the expansion volume retention rate after different aging times. When the expansion volume retention rate is less than 5%, the profile control agent is considered to have completely failed.

[0042] Evaluation of the shelf life of profile control agents at different temperatures Figure 4 As shown in the figure, it can be seen from the results that when the temperature is lower than 120℃, the dehydration rate of the swelling body is very slow, and the effective period of the profile control agent is estimated to be more than 3 years; the effective period at 140℃ and 160℃ is estimated to be more than 1 year, and it can still maintain good structural stability and swelling stability at 180℃, which greatly improves the applicable temperature of the profile control agent and meets the technical requirements of high-temperature reservoir profile control.

[0043] Test Example 2 This test example 2 uses the granular profile control agent prepared in Example 2 and conducts a salt tolerance test on it.

[0044] The test prepared 350,000 ppm sea salt solution and simulated brine, respectively. The simulated brine consisted of 250,000 ppm sea salt, 88,000 ppm calcium chloride, and 12,000 ppm magnesium chloride, wherein the concentration of calcium and magnesium ions was 35,000 ppm. The prepared sea salt solution and simulated brine were diluted into test brine samples of 280,000 ppm, 180,000 ppm, 80,000 ppm, 30,000 ppm, 10,000 ppm, 4,000 ppm, and 400 ppm, respectively.

[0045] Take 500mL of sea salt solution and simulated brine respectively, add 5g of profile control agent to each in a threaded bottle, and evaluate the complete swelling rate after constant temperature swelling at 90℃ for 3 days. The test results are as follows: Figure 5 shown.

[0046] Please refer to Figure 5 The swelling performance test results show that the water absorption swelling ratio of the product decreases with the increase of salinity. When the salinity is higher than 50,000 ppm, the swelling performance of the product is little affected by the salinity. The swelling ratio of the profile control agent in fresh water exceeds 100 times, and the swelling ratio in 280,000 ppm brine exceeds 25 times. The swelling ratio in 350,000 ppm brine can still be maintained at more than 20 times, indicating that it has excellent salt resistance and resistance to calcium and magnesium ions, and can meet the use conditions of high salinity in oil fields.

[0047] Comparative Example This comparative example is basically the same as Example 2, except that no grafting monomer is added to verify the effect of the grafting step on the technical effect of the present invention. The specific steps are as follows: S1. In parts by mass, 15 parts of acrylamide, 10 parts of sodium 2-acrylamido-2-methylpropanesulfonate, 2 parts of sodium p-styrenesulfonate and 2 parts of N-vinyl pyrrolidone were dissolved in 69.9 parts of water, and 2 parts of sodium hydroxide were added to adjust the pH of the solution to obtain a main chain - block comonomer mixed solution; S2. To the main chain-block comonomer mixed solution, 0.8 parts of a supramolecular core crosslinker CL25, 0.2 parts of a water stabilizer prepared by mixing disodium ethylenediaminetetraacetate and oxalic acid in a mass ratio of 2:1, 0.2 parts of 1,1'-azobis(N,N-dimethylformamide), 0.5 parts of urea, and 0.05 parts of an initiator prepared by mixing 20% ammonium persulfate and sodium bisulfite in a mass ratio of 3:1 were added, by weight, and then the grafted oligomer aqueous solution was added and stirred to obtain a copolymerization precursor mixture. S3. The copolymerization precursor mixture was deoxygenated with nitrogen for 30 min and allowed to stand for reaction to obtain polymer micelles; S4. Extruding, drying, shearing, granulating, roller-milling, and screening the polymer micelles to obtain a granular profile control agent.

[0048] The granular profile control agent prepared in this comparative example was tested for its temperature and salt resistance using the test methods of Test Example 1 and Test Example 2. The test results are as follows: The results of the swelling performance test show that the water absorption swelling ratio of the control example decreases with the increase of mineralization. When the mineralization is higher than 10,000 ppm, the swelling performance of the product is greatly affected by the mineralization. The swelling ratio of the profile control agent in fresh water is 104 times, which is reduced to 20 times in 10,000 ppm brine and 15 times in 30,000 ppm brine, indicating that its salt resistance is poor.

[0049] The heat resistance test shows that the comparative example water-absorbing swelling body dehydrates and degrades quickly in the 140℃ aging test, and has completely lost its structure after aging for 30 days. Figure 4 As shown, its temperature resistance is poor. The data show that the addition of grafting monomers and the implementation of the grafting step can significantly enhance the temperature and salt resistance of the profile control agent. Without the addition, the dendritic structure is destroyed, resulting in a decrease in its technical effect.

[0050] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

Claims

1. A block-graft-hyperbranched bulking profile control agent, characterized in that: The molecular structure of the profile control agent is shown in Formula 1: Formula 1; Wherein, M is a supramolecular core crosslinker; A1, A2 and A3 are small molecular polymers prepolymerized from graft copolymer monomers; n is 15%-25%; The grafted comonomer includes a grafted monomer and a block comonomer, wherein the grafted monomer is one or more of allyl sulfonic acid, sodium allyl sulfonate, methallyl sulfonic acid, sodium methallyl sulfonate, acryl phosphoric acid, sodium acryl phosphate, 2-acrylamido-2-methylpropanesulfonic acid, and sodium 2-acrylamido-2-methylpropanesulfonate; and the block comonomer is one or more of 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamido-2-methylpropanesulfonate, sodium p-styrenesulfonate, and N-vinyl pyrrolidone.

2. The profile control agent according to claim 1, characterized in that The raw materials include, by mass, 10-30 parts of polymer backbone monomers, 2-20 parts of block comonomers, 1-10 parts of graft monomers, 0.5-2 parts of supramolecular core crosslinking agents, 0.1-0.5 parts of water quality stabilizers, 0.1-0.5 parts of chain extenders, 0.1-0.5 parts of molecular structure stabilizers, 0.01-0.1 parts of initiators, and 35-75 parts of water; Wherein, the polymer main chain monomer is one or more of acrylamide and acrylic acid.

3. The profile control agent according to claim 2, characterized in that The water quality regulator is one or more of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetic acid, hydroxyethylidene diphosphonic acid, and sodium hydroxyethylidene diphosphonate.

4. The profile control agent according to claim 2, characterized in that The chain extender is one or more of 1,1'-azobis(N,N-dimethylformamide), ethylenediamine, ethylene glycol, 1,4-butanediol, 2,2-dihydroxymethylbutanoic acid, 2,2-dihydroxymethylpropionic acid, 3-hydroxyethyloxyethyl-1-hydroxyethylphenylenediether, 4,4'-methylenebis(2,6-diethylaniline), and 4,4'-methylenebis(2-ethyl)aniline.

5. The profile control agent according to claim 2, characterized in that The molecular structure stabilizer is one or more of urea, ammonium citrate, triammonium citrate, and thiourea.

6. The profile control agent according to claim 2, characterized in that The initiator is one or more of ammonium persulfate, sodium bisulfite, potassium persulfate, sodium sulfite, sodium persulfate, ammonium sulfite, hydrogen peroxide, azobisisobutyronitrile imidazoline, and azobisisobutyronitrile imidazoline hydrochloride.

7. A method for preparing a profile control agent according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. The grafted monomer is dissolved in water, a pH regulator is added to adjust the pH of the solution, heated with stirring and an initiator is added to heat and polymerize to obtain an aqueous solution of a grafted oligomer; S2. The polymer backbone monomer and block comonomer are dissolved in water, and a pH adjuster is added to adjust the pH of the solution to obtain a main chain - block comonomer mixed solution; S3. To the main chain - block comonomer mixed solution was added a water stabilizer, a chain extender, a molecular structure stabilizer and an initiator, stirred and mixed, and then the grafted oligomer aqueous solution was added and stirred to obtain a copolymerization precursor mixture; S4. Deoxygenating the copolymerization precursor liquid mixture with nitrogen, and allowing the reaction to proceed to obtain polymer micelles; S5. Extruding, drying, shearing, and granulating the polymer micelle to obtain a profile control agent.

8. The method according to claim 7, characterized in that The pH regulator is one or more of sodium hydroxide, triethanolamine, and ammonia water.

9. The method according to claim 7, characterized in that The temperature of heating and stirring in S1 is 58-62°C.

10. The method according to claim 7, characterized in that The time for nitrogen deoxygenation in S4 is 25-35 minutes.

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