Phenolic aldehyde pre-reaction polyacrylamide as well as preparation method and application thereof

Abstract

The invention discloses phenolic aldehyde pre-reaction polyacrylamide as well as a preparation method and application thereof.Sodium 2-acrylamide-2-phenyl sulfonate, N-phenylacrylamide and N-hydroxymethyl acrylamide monomers are introduced into polyacrylamide, so that the temperature resistance, salt resistance and hydrophobicity of polyacrylamide are improved, the initial viscosity is relatively low, blockage cannot be formed in a near well, and the phenolic aldehyde pre-reaction polyacrylamide is suitable for being used as a high-performance oil well drilling fluid. Under the oil reservoir condition, as time is prolonged, the 2-acrylamide-2-sodium phenyl sulfonate and the N-phenylacrylamide can react with the N-hydroxymethyl acrylamide to generate jelly, and the profile control effect is improved. The polyacrylamide prepared by the invention has the characteristics of low production energy consumption, stable quality, high viscosity, self-thickening, slow viscosity degradation in a high-temperature and high-salinity environment, high dissolution speed, good solubility and the like.

Description

Technical Field

[0001] This invention belongs to the field of tertiary oil recovery technology, specifically relating to a phenolic pre-reactive polyacrylamide, its preparation method, and its application. Background Technology

[0002] Polyacrylamide has a wide range of applications, especially in oilfield development where demand is high. With the development of oilfield development, most oilfields have entered the tertiary oil recovery stage. The polyacrylamide used in the tertiary recovery stage requires high viscosity, low viscosity degradation rate at high temperatures and high salinity, and the ability to maintain high viscosity for extended periods under high-temperature, high-salinity geological conditions. Currently, most self-thickening polyacrylamides for oilfield use are produced by modifying the polymerization process to a post-hydrolysis polymerization process, i.e., adding a hydrolyzing agent for secondary hydrolysis to increase their molecular weight to over 30 million, ensuring that they maintain a certain viscosity even as their molecular weight degrades under high-temperature, high-salinity geological conditions. Other products add about 5% monomer units carrying sulfonic acid groups during the post-hydrolysis process. However, because sulfonic acid groups hinder the polymerization reaction, even after secondary hydrolysis, their molecular weight is still not very high, mostly between 18 million and 25 million. Furthermore, due to the secondary hydrolysis, their solubility is poor and the dissolution time is long, making it difficult to meet the requirements for oilfield use.

[0003] This invention relates to a method for improving oil recovery in oilfields, specifically an intumescent flowable gel profile control and water shut-off agent, as per authorization announcement number CN101033392B. This agent exhibits significant improvements in water absorption and swelling, delayed crosslinking, and salt and temperature resistance. It can meet the needs of large-dose deep profile control, water shut-off, and flood control in various oilfields, demonstrating remarkable profile control and water shut-off effects. It is prepared by mixing a 0.07%-0.2% high-molecular-weight polyacrylamide solution with a 0.05%-0.8% boron-modified phenolic resin delayed crosslinking agent, controlling the gel reaction temperature at 40-100℃ and the pH of the solution system at 7.2-8.0. Because it uses a compound of boron-modified phenolic resin delayed crosslinking agent and high-molecular-weight polyacrylamide to form an intumescent flowable gel profile control and water shut-off agent, its gel strength is adjustable, and it possesses high water absorption and swelling, delayed crosslinking, and salt and temperature resistance. It meets the needs of different oilfields for large-dose deep profile control, water shut-off, and displacement control, and is suitable for widespread application in oilfields.

[0004] Authorization Announcement No. CN103554360B: A Temperature-Resistant and Salt-Resistant Amphiphilic Copolymer and Its Preparation Method. This invention discloses a temperature-resistant and salt-resistant amphiphilic copolymer and its preparation method. The copolymer uses acrylamide and acrylic acid as water-soluble monomers, N-arylacrylamide as a hydrophobic rigid monomer, and methacryloyloxyethyl dimethylalkylammonium bromide (chloride) as a surface-active flexible monomer, and is copolymerized using water-soluble free radicals. The copolymer of this invention introduces temperature-resistant and salt-resistant rigid side groups onto the acrylamide molecular backbone while covalently linking flexible molecular chains with good solubilizing and thickening properties. This results in excellent performance in shear resistance, temperature and salt resistance, and long-term thermosalinity stability, making it suitable for crude oil extraction in medium-temperature, high-salinity oil fields.

[0005] Authorization Announcement No. CN102559159B: A High-Temperature Resistant Phenolic Resin Weak Gel Profile Control and Water Plugging Agent. This invention relates to a high-temperature resistant phenolic resin weak gel profile control and water plugging agent, which is a profile control and water plugging agent formed by the reaction of partially hydrolyzed polyacrylamide through its amide groups with a crosslinking agent. The profile control and water plugging agent comprises, by weight percentage, the following raw materials: partially hydrolyzed polyacrylamide, 0.25%-1.2%; crosslinking agent, 0.2%-1%; additives, 0.01%-1%; and the balance being water. The high-temperature resistant phenolic resin weak gel profile control and water shut-off agent provided by this invention has a water shut-off rate of greater than 80%, an oil shut-off rate of less than 30%, a high-temperature resistance of over 90℃, and a maximum mineralization resistance of 85,000 mg / L (based on 80,000 mg / L sodium chloride and 5,000 mg / L calcium chloride). It has high gel strength, with a breakthrough strength 68% higher than previous methods, and adjustable gelation time. It can achieve the purpose of sealing high-permeability layers in the formation and adjusting the water absorption profile of deep injection wells, thereby realizing deep profile control of oil layers and greatly improving oil recovery.

[0006] Authorization Announcement No. CN104448130B: Oilfield Temperature-Resistant and Salt-Resistant Copolymer, Preparation Method and Application. This invention relates to oilfield temperature-resistant and salt-resistant copolymer, preparation method and application, mainly to solve the problems of polyacrylamide being easy to hydrolyze and having poor temperature and salt resistance under high temperature and high salinity conditions. This invention solves the problem effectively by employing a heat-resistant and salt-resistant copolymer for oilfields, as shown in general formula (I), where R1 and R2 are derived from hydrogen or C1-C16 hydrocarbon groups, and R1 and R2 are not both hydrogen; M1 and M2 are independently derived from any one of hydrogen, alkali metal, or ammonium; and x, y, m, and n are the molar numbers of structural units of acrylamide, hydrolyzed acrylamide, 2-acrylamido-2-methylpropanesulfonate, and N-alkyl-substituted acrylamide, respectively, with x:y:m:n = 100:(1-85):(1-140):(1-70). It can be used as an oilfield oil recovery agent, as well as in oilfield applications such as fracturing fluid thickener, water shut-off and profile control agent, and drilling fluid treatment agent.

[0007] Authorization Announcement No. CN103421475B: A Composite Well-Sealing and Profile-Adjusting Agent for Deep Oil Wells and Its Application. This invention relates to a composite well-sealing and profile-adjusting agent for deep oil wells and its application. The composite well-sealing and profile-adjusting agent is composed of the following components: a gel plugging solution: partially hydrolyzed polyacrylamide, sodium dichromate, and sodium thiosulfate pentahydrate in a weight ratio of 1:0.025:0.35, with an aqueous solution prepared at a total weight concentration of 0.5%-1% for the partially hydrolyzed polyacrylamide, sodium dichromate, and sodium thiosulfate pentahydrate, and hydrochloric acid to adjust the pH of the gel plugging solution to 3.5-4.5; a particulate plugging agent: phenolic resin and oxalic acid in a weight ratio of 1:0.06; a self-generating gas source: CO(NH2)2; and a surfactant: alkyl aryl sulfonate; wherein the weight ratio of the gel plugging solution, particulate plugging agent, self-generating gas source, and surfactant is 60:6:2:1. The composite plugging and profile control agent of the present invention achieves deep plugging and profile control in oil wells by generating foam in the deep formation and the physical plugging effect of solid plugging agent.

[0008] Ye Bo et al. Research on delayed crosslinking system for deep profile control. Drilling and Production Technology. 2005, 104-106. A delayed crosslinking agent of high molecular weight polyacrylamide and phenolic resin is disclosed.

[0009] Li Gang et al., Research on water-soluble phenolic resin as a crosslinking agent for water-based polymer gels, Oilfield Chemistry, 174, 2000, 17(4), 310-313, Polyacrylamide, disclosed a water-soluble phenolic resin delayed crosslinking agent.

[0010] Currently, with the improvement of acrylamide technology, it is widely used in chemical flooding. In order to achieve better results, the molecular weight of polyacrylamide is increasing, the initial viscosity is also increasing, and the oil displacement effect is becoming better. However, the injection pressure gradually increases during pumping, sometimes forcing a shutdown for unclogging, resulting in waste in both directions. Furthermore, to improve the viscosity and temperature and salt resistance of the polymer, special functional monomers or crosslinking agents are added, complicating the construction process. Moreover, the processing of crosslinking agent products causes waste; some heavy metal crosslinking agents cause pollution, and formaldehyde-containing crosslinking agents are harmful to human health. Summary of the Invention

[0011] This invention addresses the shortcomings of existing technologies by providing a phenolic pre-reacted polyacrylamide for oilfield use and a method for preparing it. The polyacrylamide incorporates sodium 2-acrylamido-2-phenylsulfonate, N-phenylacrylamide, and N-hydroxymethylacrylamide monomers. The introduction of sodium 2-acrylamido-2-phenylsulfonate and N-phenylacrylamide improves the polyacrylamide's temperature and salt resistance, and its hydrophobic initial viscosity prevents near-wellbore blockage. Under reservoir conditions, with prolonged exposure, sodium 2-acrylamido-2-phenylsulfonate and N-phenylacrylamide react with N-hydroxymethylacrylamide to form a gel, improving profile control. This phenolic pre-reacted polyacrylamide also incorporates monomers containing benzene rings and sulfonic acid groups to enhance its temperature resistance. Furthermore, the introduction of monomers containing benzene ring hydrophobic groups and hydroxymethyl groups weakens the hydration layer and reduces viscosity due to the introduction of linear benzene ring hydrophobic groups. The phenolic pre-reacted polyacrylamide further reacts at a certain temperature to form a bulk polymer with increased viscosity. This can provide oilfields with a new type of polyacrylamide-based displacement system that is easy to inject, does not clog near the well, and has high strength.

[0012] The method for preparing phenolic pre-reactive polyacrylamide of the present invention includes the following steps:

[0013] Step 1: Mix acrylamide, sodium 2-acrylamide-2-phenylsulfonate, N-phenylacrylamide, N-hydroxymethylacrylamide, cosolvent, and deionized water until completely dissolved and homogeneous. Then adjust the pH value with alkali to obtain a homopolymer solution.

[0014] Step 2: After cooling the homopolymer solution, add it to the polymerization reactor, add the initiator, and then purge with nitrogen gas. After purging with nitrogen gas, stop the polymerization reaction, and then keep it at the temperature and allow it to age to obtain polyacrylamide blocks.

[0015] Step 3: Remove the glue block, cut, granulate, dry, crush, and sieve it to obtain phenolic pre-reactive polyacrylamide.

[0016] Preferably, in step one, 25-40% acrylamide, 2-10% sodium 2-acrylamide-2-phenylsulfonate, 1-5% N-phenylacrylamide, 2-10% N-hydroxymethylacrylamide, 0.15-0.3% cosolvent, and 45-72% deionized water are thoroughly mixed and stirred until completely dissolved and homogeneous, and then the pH value is adjusted to 6.5-7.5 with alkali.

[0017] Preferably, in step one, the alkali for adjusting the pH value is sodium hydroxide or sodium carbonate, and it is prepared as a 10% aqueous solution using deionized water.

[0018] Preferably, after the well-mixed homopolymer solution in step two is added to the polymerization reactor and cooled to 0-5°C, high-purity nitrogen is introduced for 30 minutes. Then, an initiator with a mass ratio of 0.02-0.1% to the homopolymer solution is added, and high-purity nitrogen is introduced for 10 minutes. After the nitrogen is introduced, the process is stopped, and the temperature is controlled at 5°C. After the polymerization reaction is carried out for 2-4 hours, the temperature is gradually increased to 50°C over 1-3 hours and held at 50-60°C for 4-6 hours to obtain an elastic polyacrylamide block.

[0019] Preferably, the co-solvent in step one is thiourea or urea.

[0020] Preferably, the initiator in step two is an azo compound, a persulfide, or a redox system composed of a persulfide and reducing agents sodium sulfite and sodium nitrite.

[0021] Preferably, the initiator in step two is one or more of azobisisobutyronitrile, 4,4'-azobis(cyanopentanoic acid), sodium persulfate, ammonium persulfate, and potassium persulfate.

[0022] The above preparation method for preparing phenolic pre-reactive polyacrylamide using copolymerization is characterized by the following:

[0023] (1) Since acrylamide, N-hydroxymethylacrylamide, sodium 2-acrylamide-2-phenylsulfonate and N-phenylacrylamide monomer are added together during the preparation and the pH of the solution is adjusted to 6.5-7.5, acrylamide hardly undergoes hydrolysis in this medium. Therefore, it is easier to accurately prepare polyacrylamide products with excellent solubility and low degree of hydrolysis.

[0024] (2) The process is simple, as it can be produced using existing production lines, resulting in low equipment investment and production costs.

[0025] (3) Polymerization can be initiated at low temperatures, resulting in a stable reaction process. The obtained polyacrylamide has the following characteristics: low initial viscosity, generally the viscosity of a 20,000 mg / L polymer does not exceed 20 mPa·s; viscosity increases by more than 10 times after crosslinking; high temperature resistance, up to 130℃; good salt resistance, with 100,000 mineralization having little effect on the system. Compared with existing ordinary high molecular weight polyacrylamide, it has the characteristics of good temperature and salt resistance, high viscosity retention rate, and long viscosity retention time, and has excellent solubility and rapid solubility.

[0026] This invention also provides a phenolic pre-reactive polyacrylamide, prepared using the above-described method. The polyacrylamide obtained by this invention has the characteristics of low energy consumption in product production, stable quality, high viscosity, self-thickening, slow viscosity degradation under high temperature and high mineralization environments, and fast dissolution rate and good solubility.

[0027] In another aspect of the present invention, the application of the above-mentioned phenolic pre-reacted polyacrylamide in a three-stage process is provided.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] (1) A phenolic pre-reactive polyacrylamide of the present invention introduces sodium 2-acrylamide-2-phenylsulfonate, N-phenylacrylamide and N-hydroxymethylacrylamide monomers into the polyacrylamide. Due to the introduction of sodium 2-acrylamide-2-phenylsulfonate and N-phenylacrylamide, the temperature resistance and salt resistance of the polyacrylamide are improved, and the hydrophobic initial viscosity is low and will not form blockage near the well. Under reservoir conditions, as time goes on, sodium 2-acrylamide-2-phenylsulfonate and N-phenylacrylamide can react with N-hydroxymethylacrylamide to form a gel, which improves the profile control effect.

[0030] (2) Pre-reacting phenolic resin onto polymerizable monomers: N-phenylacrylamide and N-hydroxymethylacrylamide monomers and then reacting it with propionamide reduces the influence of chromatographic effects.

[0031] (3) Due to the introduction of hydrophobic groups, sodium 2-acrylamide-2-phenylsulfonate containing sulfonic acid, and N-phenylacrylamide, the products have good temperature and salt resistance as well as unique properties such as low initial viscosity and high effective viscosity. Detailed Implementation

[0032] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0033] The method for preparing phenolic pre-reactive polyacrylamide of the present invention includes the following steps:

[0034] Step 1: Mix acrylamide, sodium 2-acrylamide-2-phenylsulfonate, N-phenylacrylamide, N-hydroxymethylacrylamide, cosolvent, and deionized water until completely dissolved and homogeneous. Then adjust the pH value with alkali to obtain a homopolymer solution.

[0035] Step 2: After cooling the homopolymer solution, add it to the polymerization reactor, add the initiator, and then purge with nitrogen gas. After purging with nitrogen gas, stop the polymerization reaction, and then keep it at the temperature and allow it to age to obtain polyacrylamide blocks.

[0036] Step 3: Remove the glue block, cut, granulate, dry, crush, and sieve it to obtain phenolic pre-reactive polyacrylamide.

[0037] Preferably, in step one, 25-40% acrylamide, 2-10% sodium 2-acrylamide-2-phenylsulfonate, 1-5% N-phenylacrylamide, 2-10% N-hydroxymethylacrylamide, 0.15-0.3% cosolvent, and 45-72% deionized water are thoroughly mixed and stirred until completely dissolved and homogeneous, and then the pH value is adjusted to 6.5-7.5 with alkali.

[0038] Preferably, in step one, the alkali for adjusting the pH value is sodium hydroxide or sodium carbonate, and it is prepared as a 10% aqueous solution using deionized water.

[0039] Preferably, after the well-mixed homopolymer solution in step two is added to the polymerization reactor and cooled to 0-5°C, high-purity nitrogen is introduced for 30 minutes. Then, an initiator with a mass ratio of 0.02-0.1% to the homopolymer solution is added, and high-purity nitrogen is introduced for 10 minutes. After the nitrogen is introduced, the process is stopped, and the temperature is controlled at 5°C. After the polymerization reaction is carried out for 2-4 hours, the temperature is gradually increased to 50°C over 1-3 hours and held at 50-60°C for 4-6 hours to obtain an elastic polyacrylamide block.

[0040] Preferably, the co-solvent in step one is thiourea or urea.

[0041] Preferably, the initiator in step two is an azo compound, a persulfide, or a redox system composed of a persulfide and reducing agents sodium sulfite and sodium nitrite.

[0042] Preferably, the initiator in step two is one or more of azobisisobutyronitrile, 4,4'-azobis(cyanopentanoic acid), sodium persulfate, ammonium persulfate, and potassium persulfate.

[0043] In step (1) of the above scheme, acrylamide is an industrial product with CAS number 79-06-1 and a content of ≥99%.

[0044] In step (1) of the above scheme, N-hydroxymethylacrylamide is an industrial product with CAS number 924-42-5 and a content of ≥99.5%.

[0045] In step (1) of the above scheme, sodium 2-acrylamide-2-phenylsulfonate is a self-synthesized product.

[0046] In step (1) of the above scheme, the purity of N-phenylacrylamide is greater than or equal to 99%, according to CAS number 2210-24-4.

[0047] In another aspect of the present invention, the application of the above-mentioned phenolic pre-reacted polyacrylamide in a three-stage process is provided.

[0048] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0049] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

[0050] The present invention will be further described below with reference to specific embodiments.

[0051] In this invention, all the devices or equipment used are conventional devices or equipment known in the art and are readily available.

[0052] Unless otherwise specified, all reagents used in the following examples and comparative examples are commercially available chemically pure reagents.

[0053] Example 1:

[0054] (1) In a 1L enamel synthesis reactor, add 630g of deionized water, 300g of acrylamide, 20g of sodium 2-acrylamide-2-phenylsulfonate, 20g of N-phenylacrylamide, 40g of N-hydroxymethylacrylamide, and 2g of urea. Mix thoroughly and stir until completely dissolved and homogeneous. Then, adjust the pH to 7.2 with about 0.5g of 10% sodium hydroxide to obtain a transparent or semi-transparent homopolymer solution.

[0055] (2) Add the well-mixed homopolymer solution from (1) into the polymerization reactor and cool it to 0-5°C.

[0056] After step C, high-purity nitrogen gas is introduced for 30 minutes, then 0.3g of ammonium persulfate and 0.2g of sodium sulfite are added. High-purity nitrogen gas is introduced for 10 minutes, then the process is stopped. The temperature is controlled at 5℃, and the polymerization reaction is carried out for 3 hours. Then, the temperature is maintained at 50-60℃ for 5 hours of aging reaction to obtain a transparent and elastic polyacrylamide block.

[0057] (3) Take out the glue block, cut, granulate, dry, crush and sieve it to obtain phenolic pre-reactive polyacrylamide.

[0058] Product performance evaluation:

[0059] 1. Evaluation of the product's self-thickening performance

[0060] The following are the experimental results of preparing polymer solutions of different concentrations and placing them in a constant temperature oven:

[0061]

[0062]

[0063] The polymer takes 5 days to fully gel, and its viscosity increases more than 10 times after gelation.

[0064] 2. Evaluation of the product's salt resistance

[0065] Experiments were conducted at polymer concentrations of 10000 mg / L under different mineralization levels, with sodium chloride used to adjust the mineralization.

[0066]

[0067]

[0068] It is evident that the degree of mineralization has little impact on the performance of the system.

[0069] A polymer solution with a mineralization of 10000 mg / L sodium chloride salt was prepared and placed in an oven at 130℃ for 24 hours to gel. After 6 months, the gel state showed no significant change.

[0070] It is evident that the product of this invention exhibits high temperature resistance, reaching up to 130℃; good salt resistance, with a mineralization level of 100,000 having little impact on the system. Compared to existing ordinary high molecular weight polyacrylamide, it possesses superior temperature and salt resistance, high viscosity retention rate, and long viscosity retention time, along with excellent solubility and rapid dissolution.

[0071] Example 2:

[0072] (1) In a 1L enamel synthesis reactor, add 630g deionized water, 320g acrylamide, 10g sodium 2-acrylamide-2-phenylsulfonate, 40g N-phenylacrylamide, 60g N-hydroxymethylacrylamide, and 2g urea. Mix thoroughly and stir until completely dissolved and homogeneous. Then, adjust the pH to 7.2 with about 0.5g of 10% sodium hydroxide to obtain a transparent or semi-transparent homopolymer solution.

[0073] (2) After adding the homopolymer solution mixed in (1) into the polymerization kettle and cooling it to 0-5°C, high-purity nitrogen gas is introduced for 30 min. Then, 0.3 g of ammonium persulfate and 0.2 g of sodium sulfite are added. After introducing high-purity nitrogen gas for 10 min, the process is stopped. The temperature is controlled at 5°C. After the polymerization reaction is completed for 3 hours, the temperature is maintained at 50-60°C for 5 hours to age the product and obtain a transparent and elastic polyacrylamide block.

[0074] (3) Take out the glue block, cut, granulate, dry, crush and sieve it to obtain phenolic pre-reactive polyacrylamide.

[0075] Product performance evaluation:

[0076] 1. Evaluation of the product's self-thickening performance

[0077] The following are the experimental results of preparing polymer solutions of different concentrations and placing them in a constant temperature oven:

[0078]

[0079] The polymer takes 5 days to fully gel, and its viscosity increases more than 10 times after gelation.

[0080] 2. Evaluation of the product's salt resistance

[0081] Experiments were conducted at polymer concentrations of 10000 mg / L under different mineralization levels, with sodium chloride used to adjust the mineralization.

[0082]

[0083] It is evident that the degree of mineralization has little impact on the performance of the system.

[0084] A polymer solution with a mineralization of 10000 mg / L sodium chloride salt was prepared and placed in an oven at 130℃ for 24 hours to gel. After 6 months, the gel state showed no significant change.

[0085] It is evident that the product of this invention exhibits high temperature resistance, reaching up to 130℃; good salt resistance, with a mineralization level of 100,000 having little impact on the system. Compared to existing ordinary high molecular weight polyacrylamide, it possesses superior temperature and salt resistance, high viscosity retention rate, and long viscosity retention time, along with excellent solubility and rapid dissolution.

[0086] Example 3:

[0087] (1) In a 1L enamel synthesis reactor, add 630g of deionized water, 350g of acrylamide, 20g of sodium 2-acrylamide-2-phenylsulfonate, 20g of N-phenylacrylamide, 40g of N-hydroxymethylacrylamide, and 2g of thiourea. Mix thoroughly until completely dissolved and homogeneous. Then, adjust the pH to 7.2 with about 0.5g of 10% sodium hydroxide to obtain a transparent or semi-transparent homopolymer solution.

[0088] (2) After adding the homopolymer solution mixed in (1) into the polymerization kettle and cooling it to 0-5°C, high-purity nitrogen gas is introduced for 30 min, then 0.5 g of potassium persulfate is added, and high-purity nitrogen gas is introduced for 10 min. After the nitrogen gas is introduced, the process is stopped. The temperature is controlled at 5°C. After the polymerization reaction is carried out for 3 hours, the temperature is kept at 50-60°C and the aging reaction is carried out for 5 hours to obtain a transparent and elastic polyacrylamide block.

[0089] (3) Take out the glue block, cut, granulate, dry, crush and sieve it to obtain phenolic pre-reactive polyacrylamide.

[0090] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A phenolic pre-reactive polyacrylamide, characterized in that, The product comprises, by weight percentage, the following components: 25-40% acrylamide, 2-10% sodium 2-acrylamide-2-phenylsulfonate, 1-5% N-phenylacrylamide, 2-10% N-hydroxymethylacrylamide, 0.15-0.3% cosolvent, 45-72% deionized water, and 0.02-0.1% initiator.

2. The phenolic pre-reactive polyacrylamide according to claim 1, wherein the co-solvent is thiourea or urea.

3. The phenolic pre-reactive polyacrylamide as described in claim 1, wherein the initiator is an azo compound or a persulfide or a redox system composed of a persulfide and reducing agents sodium sulfite and sodium nitrite.

4. The phenolic pre-reactive polyacrylamide according to claim 3, wherein the initiator is one or more of azobisisoheptanenitrile, 4,4'-azobis(cyanopentanoic acid), sodium persulfate, ammonium persulfate, and potassium persulfate.

5. The method for preparing phenolic pre-reactive polyacrylamide according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Mix acrylamide, sodium 2-acrylamide-2-phenylsulfonate, N-phenylacrylamide, N-hydroxymethylacrylamide, cosolvent, and deionized water until completely dissolved and homogeneous. Then adjust the pH value with alkali to obtain a homopolymer solution. Step 2: After cooling the homopolymer solution, add it to the polymerization reactor, add the initiator, and then purge with nitrogen gas. After purging with nitrogen gas, stop the polymerization reaction, and then keep it at the temperature and allow it to age to obtain polyacrylamide blocks. Step 3: Remove the glue block, cut, granulate, dry, crush, and sieve it to obtain phenolic pre-reactive polyacrylamide.

6. The method for preparing phenolic pre-reactive polyacrylamide as described in claim 5, characterized in that, In step one, mix 25-40% acrylamide, 2-10% sodium 2-acrylamide-2-phenylsulfonate, 1-5% N-phenylacrylamide, 2-10% N-hydroxymethylacrylamide, 0.15-0.3% cosolvent, and 45-72% deionized water by weight percentage until completely dissolved and homogeneous. Then, adjust the pH value to 6.5-7.5 with alkali.

7. The method for preparing phenolic pre-reactive polyacrylamide as described in claim 6, characterized in that, In step one, sodium hydroxide or sodium carbonate is used as the alkali to adjust the pH value, and a 10% aqueous solution is prepared using deionized water.

8. The method for preparing phenolic pre-reactive polyacrylamide as described in claim 5, characterized in that, In step two, the well-mixed homopolymer solution is added to the polymerization reactor and cooled to 0-5℃. After purging with high-purity nitrogen for 30 minutes, an initiator with a mass ratio of 0.02-0.1% to the homopolymer solution is added. After purging with high-purity nitrogen for 10 minutes, the purging is stopped. The temperature is controlled at 5℃. After the polymerization reaction is carried out for 2-4 hours, the temperature is gradually increased to 50℃ over 1-3 hours and held at 50-60℃ for 4-6 hours to obtain an elastic polyacrylamide block.

9. The method for preparing phenolic pre-reactive polyacrylamide as described in claim 5, characterized in that, The co-solvent mentioned in step one is thiourea or urea.

10. The method for preparing phenolic pre-reactive polyacrylamide as described in claim 5, characterized in that, The initiator mentioned in step two is an azo compound or a persulfide, or a redox system composed of a persulfide and a reducing agent, sodium sulfite or sodium nitrite.

11. The method for preparing phenolic pre-reactive polyacrylamide as described in claim 5, characterized in that, The initiator mentioned in step two is one or more of azobisisoheptanenitrile, 4,4'-azobis(cyanopentanoic acid), sodium persulfate, ammonium persulfate, and potassium persulfate.

12. The application of the phenolic pre-reacted polyacrylamide as described in any one of claims 1-4 in tertiary oil recovery.

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