Oilfield water injection and polymer injection glass fiber reinforced plastic pipe material and preparation method

Abstract

The application belongs to the technical field of organic polymer compound preparation, and relates to an oilfield water injection and polymer injection glass steel pipeline material and a preparation method, which comprises, from inside to outside, an anticorrosive wear-resistant inner layer and a high-pressure anti-aging outer layer; the anticorrosive wear-resistant inner layer comprises epoxy vinyl ester resin, graphene-polytetrafluoroethylene composite powder, nano silicon dioxide, nano zinc oxide, isothiazolinone microbial inhibitor, methyl tetrahydrophthalic anhydride curing agent and dimethyl aniline accelerator; the high-pressure anti-aging outer layer comprises bisphenol A type epoxy resin, phenolic resin, surface modified glass fiber, nano silicon carbide, aromatic amine curing agent, triethanolamine accelerator, polysulfide rubber toughening agent, ultraviolet absorber, antioxidant and nano boron nitride; through overall cooperation of component matching and process improvement, the performance is obviously improved, the oilfield water injection and polymer injection complex working conditions are adapted, and a plurality of technical shortcomings of the existing glass steel pipeline are solved.

Description

Technical Field

[0001] This invention belongs to the field of organic polymer compound preparation technology, and relates to a fiberglass reinforced plastic (FRP) pipe material and preparation method for oilfield water injection and high-pressure transportation. It can be applied to oilfield water injection and high-pressure transportation conditions, and can improve the pipeline's corrosion resistance, wear resistance, high-pressure anti-aging and anti-microbial corrosion performance, and solve the problems of easy wear, aging and poor interlayer bonding of existing pipelines. Background Technology

[0002] Water injection and polymer injection are core technologies for enhancing oil recovery in oilfields. The working media contain inorganic salts, microorganisms, acid and alkali components, and solid particles, and are subjected to complex conditions of high pressure, high temperature, and continuous scouring for extended periods, placing stringent requirements on the safety and durability of the pipelines. Traditional metal pipelines are prone to corrosion, scaling, and microbial adhesion, resulting in short service lives and safety hazards such as leaks and blockages. They are gradually being replaced by lightweight, high-strength, and corrosion-resistant fiberglass pipelines.

[0003] Existing conventional fiberglass pipe formulations and processes struggle to simultaneously meet the dual requirements of corrosion resistance, wear resistance, and high-pressure aging resistance. The inner layer is prone to wear and corrosion, and microbial degradation, while the outer layer is susceptible to aging, brittleness, and interlayer delamination. Furthermore, insufficient curing and poor bonding result in failure to meet the requirements of continuous high-pressure operations in oilfields. The relevant shortcomings of existing technologies are as follows: Reference document 1: CN112046103B discloses a high wear-resistant fiberglass reinforced plastic (FRP) sand-filled pipe and its manufacturing method. It uses resin as a matrix, adds wear-resistant particles and glass fiber, and improves the pipe's wear resistance through winding molding, making it suitable for conveying media containing particles. This solution only focuses on optimizing wear resistance, without setting up a dual-layer functional structure, adding anti-aging components and microbial inhibitors. The outer layer is prone to UV aging and mechanical property degradation, and it lacks anti-corrosion and anti-microbial corrosion design, making it unsuitable for the complex corrosion and aging conditions of oilfield water injection and polymer injection.

[0004] Reference document 2: CN211441238U discloses a downhole high-pressure fiberglass tubing for layered water injection. The tubing body is made of glass fiber reinforced epoxy resin, with threaded reinforcement at the ends to meet the pressure-bearing and connection requirements of downhole high-pressure water injection. This design focuses on improving high-pressure load-bearing capacity but does not modify the inner wall for corrosion and wear resistance, does not add ultraviolet absorbers or antioxidants, and lacks microbial inhibitors. With long-term use, the inner wall is prone to erosion, wear, corrosion, and perforation. In field service, it is prone to aging and embrittlement, and is unsuitable for the long-term erosion and corrosive environment of the injection medium.

[0005] Comparative document 3: CN207848630U discloses an internally and externally corrosion-resistant hot-flanged water injection pipeline. The pipeline features a polytetrafluoroethylene (PTFE) lining on the inside and a fiberglass layer on the outside, achieving internal and external corrosion protection for the foundation. This design is suitable for ordinary oilfield water injection scenarios. However, this scheme only includes a simple anti-corrosion structural design, lacking a high-pressure reinforcement layer, wear-resistant filler modification, and anti-aging and anti-microbial corrosion optimization. It suffers from insufficient pressure resistance, poor inner wall wear resistance, and inability to withstand the high pressure of polytetrafluoroethylene injection and continuous erosion by solid particles. Furthermore, the outer layer is prone to aging and failure, resulting in a short service life.

[0006] In summary, existing FRP pipes used in oil fields generally suffer from insufficient corrosion and wear resistance, poor aging resistance, low high-pressure tolerance, weak interlayer bonding, and lack of antimicrobial corrosion function, making them unsuitable for complex water injection and polymer injection conditions. There is an urgent need to develop a special high-pressure FRP pipe material that combines corrosion and wear resistance, high-pressure aging resistance, and antimicrobial corrosion resistance. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and solve the technical problems of insufficient corrosion and wear resistance, poor anti-aging performance, low mechanical strength, weak interlayer bonding, and short service life of existing fiberglass pipes, so as to provide a fiberglass pipe material for oilfield water injection and polymer injection.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A fiberglass reinforced plastic (FRP) pipe material for oilfield water injection adopts a double-layer structure, consisting of a 1.5-2.0mm thick anti-corrosion and wear-resistant inner layer and a 2.5-3.0mm thick high-pressure anti-aging outer layer from the inside out. The formula of each layer by weight is as follows: Corrosion-resistant and wear-resistant inner layer: 65-70 parts epoxy vinyl ester resin, 12-15 parts graphene-polytetrafluoroethylene composite micro powder, 6-8 parts nano silica, 4-5 parts nano zinc oxide, 2-3 parts isothiazolinone microbial inhibitor, 2.5-3.5 parts methyltetrahydrophthalic anhydride curing agent, and 1.2-1.8 parts dimethylaniline accelerator; High-pressure anti-aging outer layer: 58-62 parts of bisphenol A type epoxy resin, 20-22 parts of phenolic resin, 28-32 parts of surface-modified glass fiber, 5-6 parts of nano silicon carbide, 3.5-4.5 parts of aromatic amine curing agent, 1.2-1.8 parts of triethanolamine accelerator, 3.2-3.8 parts of polysulfide rubber toughening agent, 2.2-2.8 parts of ultraviolet absorber, 1.2-1.8 parts of antioxidant, and 0.1-0.2 parts of nano boron nitride.

[0009] The preparation method of the graphene-polytetrafluoroethylene composite micro powder of the present invention includes the following steps: (1) Raw material pretreatment: Weigh graphene and polytetrafluoroethylene powder at a mass ratio of 1:8.5-9.5, put them into a vacuum oven and dry them at 45-50℃ and vacuum degree of 0.06-0.08MPa for 1-1.5h to remove adsorbed moisture and impurities from the surface of the raw materials. (2) Preparation of rare earth pretreatment solution: Weigh 0.2-0.4% of lanthanide rare earth oxide La2O3, which accounts for 1:10-12 of the total mass of the mixed powder, add a mixture of anhydrous ethanol and deionized water in a volume ratio of 2:1, add dilute nitric acid to adjust the pH to 3.5-4.5, and ultrasonically disperse for 5-8 min to prepare a uniform rare earth pretreatment solution; (3) Premixing treatment: The dried graphene and polytetrafluoroethylene powder are placed in a high-speed mixer, and the prepared rare earth pretreatment liquid is added dropwise at a uniform speed. The mixture is premixed for 8-10 minutes at a speed of 1200-1500 r / min and a temperature of 25-30℃ to make the rare earth elements uniformly adhere to the powder surface. (4) Synergistic modification treatment: Add 0.3-0.5% of silane coupling agent KH-570 to the high-speed mixer, adjust the speed to 1500-1800 r / min, raise the temperature to 40-45℃, and continue mixing for 15-18 min to achieve synergistic modification of rare earth elements and silane coupling agent, and enhance the wear resistance and corrosion resistance of composite micro powder; (5) Vacuum drying: Place the synergistically modified mixed powder into a vacuum drying oven, control the drying temperature at 50-60℃ and the vacuum degree at 0.08-0.1MPa, and dry for 1-1.5h to remove residual solvent; (6) Post-processing: The dried powder is passed through a 200-250 mesh sieve to remove large particles that are not evenly dispersed. The powder is then treated with plasma for 1-2 minutes at a plasma power of 200-250W to further activate the surface and obtain the graphene-polytetrafluoroethylene composite micro powder product.

[0010] In step (1) of the present invention, the graphene is pretreated with plasma with a plasma power of 200-250W and a treatment time of 3-5min.

[0011] The specific parameters of the ultrasonic dispersion treatment in step (2) of this invention are as follows: ultrasonic power 300-350W, ultrasonic time 18-20min, temperature controlled at 25-30℃ during ultrasonication, using the "intermittent ultrasonic" mode, ultrasonic for 3min, stop for 1min, and at the same time add 0.1-0.2wt% of polyethylene glycol 400 as a dispersant to avoid agglomeration of composite micro powder; after ultrasonication, centrifugation is used at a speed of 3000r / min for 5-8min.

[0012] The modification method of the surface-modified glass fiber described in this invention is as follows: alkali-free glass fiber is immersed in a mixed solution of silane coupling agent KH-560 and dopamine at a material-to-liquid ratio of 1:15-18 for 32-38 minutes. The mass ratio of KH-560 to dopamine in the mixed solution is 2:1. After removal, it is dried at 82-88℃ for 2.0-2.8 hours.

[0013] In the anti-corrosion and wear-resistant inner layer of the present invention, the isothiazolinone microbial inhibitor is selected from a compound system of isothiazolinone and formaldehyde with a mass ratio of 3:1.

[0014] In the high-pressure anti-aging outer layer of the present invention, the ultraviolet absorber is UV-327; and the antioxidant is antioxidant 1010.

[0015] During the vacuum drying process described in this invention, ventilation is performed every 30 minutes for 10-15 seconds each time to ensure that the residual anhydrous ethanol completely evaporates, avoid residual solvents affecting the bonding between the composite micropowder and the resin matrix, and prevent graphene oxidation, thus ensuring the modification effect of the composite micropowder.

[0016] This invention also provides a method for preparing fiberglass reinforced plastic (FRP) pipe materials for oilfield water injection, comprising the following steps: (1) Raw material preparation: Weigh each component according to the formula; (2) Preparation of inner layer mixture: epoxy vinyl ester resin, graphene-polytetrafluoroethylene composite micro powder, nano silica and nano zinc oxide are placed in a high-speed mixer and mixed for 15-18 minutes at a speed of 850-950 r / min and a temperature of 26-29℃. Then microbial inhibitor, curing agent and accelerator are added and mixed for another 5-8 minutes to obtain corrosion-resistant and wear-resistant inner layer mixture. (3) Preparation of outer layer mixture: Bisphenol A type epoxy resin, phenolic resin, and polysulfide rubber toughening agent are put into a high-speed mixer and mixed for 10-12 minutes. Then, surface modified glass fiber, nano silicon carbide, nano boron nitride, ultraviolet absorber, antioxidant, curing agent and accelerator are added and mixed evenly to obtain high pressure anti-aging outer layer mixture. (4) Composite molding: The spray molding process is adopted. First, the inner layer mixture is evenly sprayed on the surface of the mold, and the thickness is controlled at 1.5-2.0 mm. Let it stand for 6-8 minutes to remove surface air bubbles. After the inner layer has been initially cured, the outer layer mixture is sprayed, and the thickness is controlled at 2.5-3.0 mm. (5) Segmented curing: The molded material is placed in a curing oven and cured in segments; (6) Post-processing: After natural cooling to 25-30℃, the material is taken out of the mold, polished, trimmed and screened to remove surface defects and obtain the finished product of oilfield water injection and polymer injection fiberglass pipe material.

[0017] As a further technical solution, the segmented curing process is as follows: first, the temperature is increased to 85-95℃ at a heating rate of 5-8℃ / min and held for 2-2.5 hours for low-temperature pre-curing; then, the temperature is increased to 125-135℃ at a heating rate of 6-9℃ / min and held for 4-4.5 hours for medium-temperature curing; finally, the temperature is increased to 160-170℃ at a heating rate of 6-9℃ / min and held for 1-1.5 hours for high-temperature setting; the cooling rate at each stage is controlled at 3-5℃ / min.

[0018] Compared with existing technologies, this invention offers at least the following advantages: First, through a dual-layer structure and layered formulation design, the corrosion-resistant and wear-resistant inner layer and the high-pressure anti-aging outer layer complement each other, achieving a comprehensive improvement from the material's microstructure to its overall performance. The inner layer uses epoxy vinyl ester resin as the main body, combined with graphene-polytetrafluoroethylene composite micropowder. Utilizing the high barrier properties of graphene and the self-lubricating properties of polytetrafluoroethylene, a dense and low-friction coefficient protective layer is formed on the material surface. Combined with the filling and reinforcing effects of nano-silica and nano-zinc oxide, the density and hardness of the inner layer are improved, reducing wear caused by media penetration and solid particle erosion. At the same time, graphene and rare earth modification further optimize the filler dispersion, reduce interface defects, and effectively inhibit the intrusion of corrosive media, thereby significantly improving the corrosion-resistant and wear-resistant performance of the inner layer and solving the problems of pipe wall thinning and perforation caused by long-term erosion and chemical corrosion. Isothiazolinone-based microbial inhibitors can selectively inhibit the growth and metabolism of common oilfield microorganisms, preventing microbial corrosion from damaging the material matrix. Synergistically working with anti-corrosion components, they achieve dual functions of chemical and biological corrosion protection, extending the service life of the inner layer. Secondly, the outer layer in the technical solution uses bisphenol A epoxy resin and phenolic resin as the matrix, relying on surface-modified glass fibers for skeletal reinforcement. Modification treatment enhances the interfacial bonding between the fiber and resin, reducing interlayer voids and defects. Combined with the rigid filling and wear-resistant support of nano-silicon carbide and nano-boron nitride, the mechanical strength and high-pressure resistance of the outer layer are significantly improved, meeting the structural safety requirements of high-pressure transportation conditions in oilfields. Aromatic amine curing agents and triethanolamine accelerators are matched to ensure full cross-linking and curing of the resin. Polysulfide rubber toughening agents alleviate internal stress in the material, improving impact resistance and deformation resistance. UV-327, an ultraviolet absorber, absorbs external ultraviolet radiation, while antioxidant 1010 inhibits thermo-oxidative aging and degradation. Together, they block the aging pathway, delaying material embrittlement and performance degradation, thus solving the aging failure problem caused by long-term outdoor use. The various nanofillers, resin, and fibers form an interpenetrating network structure, improving overall density and stability, giving the outer layer high-pressure load-bearing capacity, anti-aging properties, and deformation resistance. Thirdly, through the overall synergy of component formulation and process improvement, significant performance enhancements are achieved. Rare earth elements and coupling agents in the graphene-PTFE composite micropowder synergistically modify the filler dispersion and interfacial bonding; surface-modified glass fibers enhance interlayer bonding strength and mechanical transfer efficiency; and segmented curing processes eliminate internal stress, ensure sufficient cross-linking, and prevent the formation of bubbles and defects. The dual-layer structure enables functional zoning. The inner layer focuses on corrosion resistance, wear resistance, and antimicrobial properties, while the outer layer focuses on high-pressure anti-aging and toughening. Ultimately, this gives the pipeline material excellent corrosion resistance, wear resistance, antimicrobial corrosion resistance, high-pressure tolerance, anti-aging properties, and mechanical stability, significantly extending its service life, reducing replacement and maintenance costs, adapting to the complex working conditions of water injection and polymer injection in oil fields, solving many technical shortcomings of existing FRP pipelines, and possessing significant engineering application value. Attached Figure Description

[0019] Figure 1This is a statistical diagram illustrating the tensile strength retention rate of the present invention and a comparative example.

[0020] Figure 2 This invention relates to a process flow diagram of a method for preparing fiberglass reinforced plastic (FRP) pipe materials for oilfield water injection. Detailed Implementation

[0021] The technical solution of the present invention will now be clearly and completely described in conjunction with the embodiments and accompanying drawings.

[0022] Example 1: Preparation of graphene-polytetrafluoroethylene composite micropowder: Raw material pretreatment: Graphene and polytetrafluoroethylene powder were weighed at a mass ratio of 1:8.5. Graphene was pretreated with plasma at a plasma power of 200W for 3 minutes. The pretreated graphene and polytetrafluoroethylene powder were placed in a vacuum oven and dried at 45℃ and 0.06MPa for 1 hour.

[0023] Preparation of rare earth pretreatment solution: Weigh 0.2% of lanthanide rare earth oxides La2O3, which account for 1.2% of the total mass of the mixed powder, and add a mixture of anhydrous ethanol and deionized water in a volume ratio of 2:1 at a material-to-liquid ratio of 1:10. Adjust the pH to 3.5 with dilute nitric acid and ultrasonically disperse for 5 min. The ultrasonic power is 300W and the ultrasonic time is 18 min. The temperature is controlled at 25℃ during the ultrasonic process. Use intermittent ultrasonic mode, ultrasonic for 3 min, stop for 1 min, and add 0.1 wt% of polyethylene glycol 400 as a dispersant. After ultrasonication, centrifuge at 3000 r / min for 5 min to prepare a uniform rare earth pretreatment solution.

[0024] Premixing treatment: The dried graphene and polytetrafluoroethylene powder are placed in a high-speed mixer, and the prepared rare earth pretreatment solution is added dropwise at a uniform speed. The mixture is premixed for 8 minutes at a speed of 1200 r / min and a temperature of 25℃ to ensure that the rare earth elements are uniformly attached to the powder surface.

[0025] Synergistic modification treatment: Add 0.3% of the total mass of the mixed powder of silane coupling agent KH-570 to the high-speed mixer, adjust the speed to 1500 r / min, raise the temperature to 40℃, and continue mixing for 15 min.

[0026] Vacuum drying: The synergistically modified mixed powder is placed in a vacuum drying oven, and the drying temperature is controlled at 50℃ and the vacuum degree is 0.08MPa for 1 hour. During the vacuum drying process, ventilation is carried out once every 30 minutes for 10 seconds each time.

[0027] Post-processing: The dried powder is passed through a 200-mesh sieve to remove large particles that are not evenly dispersed. It is then subjected to plasma treatment for 1 minute at a plasma power of 200W to obtain the graphene-polytetrafluoroethylene composite micro powder product.

[0028] Preparation of surface-modified glass fibers: Alkali-free glass fibers were immersed in a mixed solution of silane coupling agent KH-560 and dopamine at a material-to-liquid ratio of 1:15 for 32 minutes. The mass ratio of KH-560 to dopamine in the mixed solution was 2:1. After immersion, the fibers were dried at 82°C for 2.0 hours.

[0029] Pipe material formula: Corrosion-resistant and wear-resistant inner layer (1.5mm thickness): 65 parts epoxy vinyl ester resin, 12 parts graphene-polytetrafluoroethylene composite micro powder, 6 parts nano silica, 4 parts nano zinc oxide, 2 parts isothiazolinone and formaldehyde compound microbial inhibitor (mass ratio 3:1), 2.5 parts methyltetrahydrophthalic anhydride curing agent, and 1.2 parts dimethylaniline accelerator. High-pressure anti-aging outer layer (2.5mm thickness): 58 parts bisphenol A type epoxy resin, 20 parts phenolic resin, 28 parts surface-modified glass fiber, 5 parts nano silicon carbide, 3.5 parts aromatic amine curing agent, 1.2 parts triethanolamine accelerator, 3.2 parts polysulfide rubber toughening agent, 2.2 parts UV-327 ultraviolet absorber, 1.2 parts antioxidant 1010, and 0.1 parts nano boron nitride.

[0030] Preparation method of fiberglass reinforced plastic (FRP) pipe material for oilfield water injection: Raw material preparation: Weigh each component according to the above formula.

[0031] Preparation of inner layer mixture: Epoxy vinyl ester resin, graphene-polytetrafluoroethylene composite micro powder, nano silica, and nano zinc oxide are placed in a high-speed mixer and mixed for 15 minutes at a speed of 850 r / min and a temperature of 26℃. Then, microbial inhibitors, methyltetrahydrophthalic anhydride curing agent, and dimethylaniline accelerator are added, and the mixture is mixed for another 5 minutes to obtain the anti-corrosion and wear-resistant inner layer mixture.

[0032] Preparation of outer layer mixture: Bisphenol A type epoxy resin, phenolic resin, and polysulfide rubber toughening agent are placed in a high-speed mixer and mixed for 10 minutes. Then, surface-modified glass fiber, nano silicon carbide, nano boron nitride, UV-327, antioxidant 1010, aromatic amine curing agent, and triethanolamine accelerator are added and mixed evenly to obtain high-pressure anti-aging outer layer mixture.

[0033] Composite molding: Using a spray molding process, the inner layer mixture is first evenly sprayed onto the mold surface, with a thickness of 1.5mm, and left to stand for 6 minutes to remove surface air bubbles; after the inner layer has initially cured, the outer layer mixture is then sprayed, with a thickness of 2.5mm.

[0034] Segmented curing: The molded material is placed in a curing oven. First, the temperature is increased to 85°C at a rate of 5°C / min and held for 2 hours for low-temperature pre-curing. Then, the temperature is increased to 125°C at a rate of 6°C / min and held for 4 hours for medium-temperature curing. Finally, the temperature is increased to 160°C at a rate of 6°C / min and held for 1 hour for high-temperature setting. The cooling rate at each stage is controlled at 3°C / min.

[0035] Post-processing: After natural cooling to 25℃, the material is removed from the mold, polished, trimmed, and screened to remove surface defects, thus obtaining the finished product of the oilfield water injection fiberglass pipe material.

[0036] Example 2: Preparation of graphene-polytetrafluoroethylene composite micropowder: Raw material pretreatment: Graphene and polytetrafluoroethylene powder were weighed at a mass ratio of 1:9.5. Graphene was pretreated with plasma at a power of 250W for 5 minutes. The pretreated graphene and polytetrafluoroethylene powder were then placed in a vacuum oven and dried at 50°C and 0.08MPa for 1.5 hours.

[0037] Preparation of rare earth pretreatment solution: Weigh 0.4% of lanthanide rare earth oxides La2O3, which account for 1.4% of the total mass of the mixed powder, and add a mixture of anhydrous ethanol and deionized water in a volume ratio of 2:1 at a material-to-liquid ratio of 1:12. Adjust the pH to 4.5 with dilute nitric acid and ultrasonically disperse for 8 min. The ultrasonic power is 350W and the ultrasonic time is 20 min. The temperature is controlled at 30℃ during the ultrasonic process. Use intermittent ultrasonic mode, ultrasonic for 3 min, stop for 1 min, and add 0.2wt% of polyethylene glycol 400 as a dispersant. After ultrasonication, centrifuge at 3000 r / min for 8 min to prepare a uniform rare earth pretreatment solution.

[0038] Premixing treatment: The dried graphene and polytetrafluoroethylene powder are placed in a high-speed mixer, and the prepared rare earth pretreatment solution is added dropwise at a uniform speed. The mixture is premixed for 10 minutes at a speed of 1500 r / min and a temperature of 30℃ to ensure that the rare earth elements are uniformly attached to the powder surface.

[0039] Synergistic modification treatment: Add 0.5% of the total mass of the mixed powder of silane coupling agent KH-570 to the high-speed mixer, adjust the speed to 1800 r / min, raise the temperature to 45℃, and continue mixing for 18 min.

[0040] Vacuum drying: The synergistically modified mixed powder is placed in a vacuum drying oven, and the drying temperature is controlled at 60℃ and the vacuum degree is 0.1MPa for 1.5h. During the vacuum drying process, ventilation is carried out once every 30min for 15s each time.

[0041] Post-processing: The dried powder is passed through a 250-mesh sieve to remove large particles that are not evenly dispersed. It is then subjected to plasma treatment for 2 minutes at a plasma power of 250W to obtain the graphene-polytetrafluoroethylene composite micro powder product.

[0042] Preparation of surface-modified glass fibers: Alkali-free glass fibers were immersed in a mixed solution of silane coupling agent KH-560 and dopamine at a ratio of 1:18 for 38 minutes. The mass ratio of KH-560 to dopamine in the mixed solution was 2:1. After immersion, the fibers were dried at 88°C for 2.8 hours.

[0043] Pipe material formula: Corrosion-resistant and wear-resistant inner layer (2.0mm thickness): 70 parts epoxy vinyl ester resin, 15 parts graphene-polytetrafluoroethylene composite micro powder, 8 parts nano silica, 5 parts nano zinc oxide, 3 parts isothiazolinone and formaldehyde compound microbial inhibitor (mass ratio 3:1), 3.5 parts methyltetrahydrophthalic anhydride curing agent, and 1.8 parts dimethylaniline accelerator. High-pressure anti-aging outer layer (3.0mm thickness): 62 parts bisphenol A type epoxy resin, 22 parts phenolic resin, 32 parts surface-modified glass fiber, 6 parts nano silicon carbide, 4.5 parts aromatic amine curing agent, 1.8 parts triethanolamine accelerator, 3.8 parts polysulfide rubber toughening agent, 2.8 parts UV-327 ultraviolet absorber, 1.8 parts antioxidant 1010, and 0.2 parts nano boron nitride.

[0044] Preparation method of fiberglass reinforced plastic (FRP) pipe material for oilfield water injection: Raw material preparation: Weigh each component according to the above formula.

[0045] Preparation of inner layer mixture: Epoxy vinyl ester resin, graphene-polytetrafluoroethylene composite micro powder, nano silica, and nano zinc oxide are placed in a high-speed mixer and mixed for 18 minutes at a speed of 950 r / min and a temperature of 29℃. Then, microbial inhibitors, methyltetrahydrophthalic anhydride curing agent, and dimethylaniline accelerator are added, and mixing is continued for 8 minutes to obtain the anti-corrosion and wear-resistant inner layer mixture.

[0046] Preparation of outer layer mixture: Bisphenol A type epoxy resin, phenolic resin, and polysulfide rubber toughening agent are placed in a high-speed mixer and mixed for 12 minutes. Then, surface-modified glass fiber, nano silicon carbide, nano boron nitride, UV-327, antioxidant 1010, aromatic amine curing agent, and triethanolamine accelerator are added and mixed evenly to obtain high-pressure anti-aging outer layer mixture.

[0047] Composite molding: Using a spray molding process, the inner layer mixture is first evenly sprayed onto the mold surface, with a thickness of 2.0mm, and left to stand for 8 minutes to remove surface air bubbles; after the inner layer has initially cured, the outer layer mixture is then sprayed, with a thickness of 3.0mm.

[0048] Segmented curing: The molded material is placed in a curing oven. First, the temperature is increased to 95°C at a rate of 8°C / min and held for 2.5 hours for low-temperature pre-curing. Then, the temperature is increased to 135°C at a rate of 9°C / min and held for 4.5 hours for medium-temperature curing. Finally, the temperature is increased to 170°C at a rate of 9°C / min and held for 1.5 hours for high-temperature setting. The cooling rate at each stage is controlled at 5°C / min.

[0049] Post-processing: After natural cooling to 30℃, the material is removed from the mold, polished, trimmed, and screened to remove surface defects, thus obtaining the finished product of the oilfield water injection fiberglass pipe material.

[0050] Example 3: Preparation of graphene-polytetrafluoroethylene composite micropowder: Raw material pretreatment: Graphene and polytetrafluoroethylene powder were weighed at a mass ratio of 1:9. Graphene was pretreated with plasma at a plasma power of 225W for 4 minutes. The pretreated graphene and polytetrafluoroethylene powder were placed in a vacuum oven and dried at 47.5℃ and 0.07MPa for 1.25 hours.

[0051] Preparation of rare earth pretreatment solution: Weigh 0.3% of lanthanide rare earth oxides La2O3, which account for 1.3% of the total mass of the mixed powder, and add a mixture of anhydrous ethanol and deionized water in a volume ratio of 2:1 at a material-to-liquid ratio of 1:11. Adjust the pH to 4.0 with dilute nitric acid and ultrasonically disperse for 6.5 min. The ultrasonic power is 325W and the ultrasonic time is 19 min. The temperature is controlled at 27.5℃ during the ultrasonic process. Use intermittent ultrasonic mode, ultrasonic for 3 min, stop for 1 min, and add 0.15wt% of polyethylene glycol 400 as a dispersant. After ultrasonication, centrifuge at 3000 r / min for 6.5 min to prepare a uniform rare earth pretreatment solution.

[0052] Premixing treatment: The dried graphene and polytetrafluoroethylene powder are placed in a high-speed mixer, and the prepared rare earth pretreatment solution is added dropwise at a uniform speed. The mixture is premixed for 9 minutes at a speed of 1350 r / min and a temperature of 27.5℃ to ensure that the rare earth elements are uniformly attached to the powder surface.

[0053] Synergistic modification treatment: Add 0.4% of the total mass of the mixed powder of silane coupling agent KH-570 to the high-speed mixer, adjust the speed to 1650 r / min, raise the temperature to 42.5℃, and continue mixing for 16.5 min.

[0054] Vacuum drying: The synergistically modified mixed powder was placed in a vacuum drying oven, and the drying temperature was controlled at 55℃ and the vacuum degree at 0.09MPa for 1.25h. During the vacuum drying process, ventilation was carried out once every 30min for 12.5s each time.

[0055] Post-processing: The dried powder is passed through a 225-mesh sieve to remove large particles that are not evenly dispersed. It is then subjected to plasma treatment for 1.5 minutes at a plasma power of 225W to obtain the graphene-polytetrafluoroethylene composite micro powder product.

[0056] Preparation of surface-modified glass fibers: Alkali-free glass fibers were immersed in a mixed solution of silane coupling agent KH-560 and dopamine at a ratio of 1:16.5 for 35 minutes. The mass ratio of KH-560 to dopamine in the mixed solution was 2:1. After immersion, the fibers were dried at 85°C for 2.4 hours.

[0057] Pipe material formula: Corrosion-resistant and wear-resistant inner layer (1.75mm thick): 67.5 parts epoxy vinyl ester resin, 13.5 parts graphene-polytetrafluoroethylene composite micro powder, 7 parts nano silica, 4.5 parts nano zinc oxide, 2.5 parts isothiazolinone and formaldehyde compound microbial inhibitor (mass ratio 3:1), 3 parts methyltetrahydrophthalic anhydride curing agent, and 1.5 parts dimethylaniline accelerator. High-pressure anti-aging outer layer (2.75mm thick): 60 parts bisphenol A type epoxy resin, 21 parts phenolic resin, 30 parts surface-modified glass fiber, 5.5 parts nano silicon carbide, 4 parts aromatic amine curing agent, 1.5 parts triethanolamine accelerator, 3.5 parts polysulfide rubber toughening agent, 2.5 parts UV-327 ultraviolet absorber, 1.5 parts antioxidant 1010, and 0.15 parts nano boron nitride.

[0058] Preparation method of fiberglass reinforced plastic (FRP) pipe material for oilfield water injection: Raw material preparation: Weigh each component according to the above formula.

[0059] Preparation of inner layer mixture: Epoxy vinyl ester resin, graphene-polytetrafluoroethylene composite micro powder, nano silica, and nano zinc oxide are placed in a high-speed mixer and mixed for 16.5 min at a speed of 900 r / min and a temperature of 27.5℃. Then, microbial inhibitors, methyltetrahydrophthalic anhydride curing agent, and dimethylaniline accelerator are added, and mixing is continued for 6.5 min to obtain the anti-corrosion and wear-resistant inner layer mixture.

[0060] Preparation of outer layer mixture: Bisphenol A type epoxy resin, phenolic resin, and polysulfide rubber toughening agent are placed in a high-speed mixer and mixed for 11 minutes. Then, surface-modified glass fiber, nano silicon carbide, nano boron nitride, UV-327, antioxidant 1010, aromatic amine curing agent, and triethanolamine accelerator are added and mixed evenly to obtain high-pressure anti-aging outer layer mixture.

[0061] Composite molding: Using a spray molding process, the inner layer mixture is first evenly sprayed onto the mold surface, with a thickness of 1.75mm, and left to stand for 7 minutes to remove surface air bubbles; after the inner layer has initially cured, the outer layer mixture is then sprayed, with a thickness of 2.75mm.

[0062] Segmented curing: The molded material is placed in a curing oven. First, the temperature is increased to 90℃ at a rate of 6.5℃ / min and held for 2.25 hours for low-temperature pre-curing. Then, the temperature is increased to 130℃ at a rate of 7.5℃ / min and held for 4.25 hours for medium-temperature curing. Finally, the temperature is increased to 165℃ at a rate of 7.5℃ / min and held for 1.25 hours for high-temperature setting. The cooling rate at each stage is controlled at 4℃ / min.

[0063] Post-processing: After natural cooling to 27.5℃, the material is removed from the mold, polished, trimmed, and screened to remove surface defects, thus obtaining the finished product of the oilfield water injection fiberglass pipe material.

[0064] Comparative Example 1: Compared with Example 3, no graphene-PTFE composite micro powder was added, but the rest of the formulation, preparation process and modification process were exactly the same.

[0065] Comparative Example 2: Compared with Example 3, no isothiazolinone-type microbial inhibitors were added, but the rest of the formulation, preparation process, and modification process were exactly the same.

[0066] Comparative Example 3: Compared with Example 3, the outer layer does not contain UV absorber UV-327 and antioxidant 1010, but the rest of the formulation, preparation process and modification process are exactly the same.

[0067] Comparative Example 4: Compared with Example 3, ordinary unmodified glass fiber was used instead of surface-modified glass fiber, while the rest of the formulation, preparation process and modification process were exactly the same.

[0068] Performance testing: Experiment 1: Corrosion and wear resistance test: Experimental objective: The corrosion resistance level and wear amount of Examples 1-3 and Comparative Examples 1-4 were tested to verify the effect of graphene-polytetrafluoroethylene composite micropowder on corrosion resistance and wear resistance.

[0069] Test method: Corrosion resistance: Referring to the oilfield water and polymer injection medium environment, a simulated corrosion solution containing sodium chloride, sodium bicarbonate, and calcium chloride was prepared. The sample was immersed in the simulated corrosion solution at a temperature of 60℃ for 30 days. The mass change rate before and after corrosion was tested to evaluate the corrosion resistance level.

[0070] Wear resistance: The wear amount of the sample was tested using a wear testing machine with a loading pressure of 5MPa, a rotation speed of 200r / min, and a wear time of 2h.

[0071] Experimental data: Table 1

[0072] Examples 1-3 all exhibited a mass change rate of less than 0.15%, a corrosion resistance grade of Level 1, and wear loss of less than 20 mg, demonstrating excellent corrosion and wear resistance. Comparative Example 1, lacking graphene-PTFE composite micropowder, showed a significant decrease in surface density and lubricity, reducing corrosion resistance to Level 4 and significantly increasing wear loss, which is the core factor affecting corrosion and wear resistance. Comparative Example 2, lacking microbial inhibitors, and Comparative Example 3, lacking anti-aging components, had no significant impact on corrosion and wear resistance. Comparative Example 4, using ordinary glass fiber, exhibited poor interfacial bonding, resulting in a decrease in both corrosion and wear resistance, but the degree of deterioration was lower than that of Comparative Example 1.

[0073] Experiment 2: Anti-aging and mechanical property tests: Experimental objective: The retention rates of tensile strength and interlaminar shear strength after UV aging were tested in Examples 1-3 and Comparative Examples 1-4 to verify the effects of UV absorbers, antioxidants and surface-modified glass fibers.

[0074] Test method: UV aging: A UV aging test chamber was used with a wavelength of 340nm and an irradiation intensity of 0.51W / m². 2 The test lasted 500 hours, and the tensile strength before and after aging was tested to calculate the retention rate.

[0075] Interlaminar shear strength: The interlaminar shear strength of the specimen is tested according to conventional mechanical testing methods.

[0076] Experimental data: Table 2

[0077] Examples 1-3 showed tensile strength retention rates exceeding 85% and interlaminar shear strength exceeding 40 MPa after UV aging, demonstrating excellent anti-aging and mechanical properties. Comparative Example 3, lacking UV absorbers and antioxidants, experienced rapid degradation under UV light, resulting in a significant drop in tensile strength retention to 62.3% and a marked decrease in mechanical properties. Comparative Example 4, using ordinary glass fiber, exhibited poor interfacial bonding with the resin matrix, leading to an interlaminar shear strength reduction to 28.4 MPa and a significantly lower strength retention rate after UV aging. Comparative Example 1 lacked graphene-PTFE composite micropowder, resulting in decreased mechanical properties. Comparative Example 2, lacking anti-aging components and modified glass fiber, showed no significant deterioration in mechanical and anti-aging properties.

[0078] Experiment 3: Effect of staged curing regime on tensile strength retention rate: Experimental objective: Based on the formula and molding process of Example 3, only the curing method was changed. The effects of single low-temperature curing, single medium-temperature curing, single high-temperature curing, and the three-stage segmented curing of this example were compared to verify the effect of segmented curing on the retention rate of tensile strength of oilfield water injection and polymer injection fiberglass pipeline materials after ultraviolet aging.

[0079] Basic experimental conditions: Basic formula: Example 3 Complete formula: The basic process, including spray coating, double-layer thickness, raw material mixing, and modification process, is completely consistent with Example 2. UV aging conditions: wavelength 340nm, irradiation intensity 0.51W / m 2 Aging time: 500 hours Test index: Tensile strength retention rate after UV aging (%): Experimental group design: Group 1 (Example 3): This example uses a three-stage segmented curing process; Group 2: Single low-temperature curing only; Group 3: Cured at a single medium temperature only; Group 4: Cured only at high temperature; Curing process parameters for each group: Group 1 (three-stage segmented curing): Heat to 85℃ at 5℃ / min and hold for 2 hours; heat to 125℃ at 6℃ / min and hold for 4 hours; heat to 160℃ at 6℃ / min and hold for 1 hour; cooling rate throughout: 3℃ / min.

[0080] Group 2 (single low-temperature curing): Heating rate 5℃ / min to 85℃, total holding time 7.5h; cooling rate 3℃ / min. (Total holding time is the same as the total time of the three segments in Group 1); Group 3 (single medium-temperature curing): Heating rate 6℃ / min to 125℃, total holding time 7.5h; cooling rate 3℃ / min. (Total holding time is the same as the total time of the three stages in Group 1); Group 4 (single high-temperature curing): Heating to 160℃ at a rate of 6℃ / min, with a total holding time of 7.5h; cooling rate of 3℃ / min. (Total holding time is the same as the total time of the three segments in Group 1). Experimental data: Table 3

[0081] The three-stage segmented curing process yields the best results. Group 1 employs the low-temperature pre-curing, medium-temperature curing, and high-temperature shaping segmented process of this invention. The resin cross-linking is gradually and completely completed, small molecules are fully discharged, and internal stress is effectively released. The material structure is dense and stable, and the tensile strength retention rate after UV aging reaches 89.5%, which is significantly better than single-temperature curing.

[0082] The single low-temperature curing (Group 2) has poor performance. The temperature is too low, the resin cannot achieve deep cross-linking, the degree of curing is insufficient, the overall strength of the material is low, the aging resistance is poor, and the tensile strength retention rate is only 55.2%.

[0083] The single medium-temperature curing (Group 3) has average performance. It lacks a low-temperature pre-curing stage, and the rapid gelation of the resin makes it difficult to remove internal bubbles and defects. It also lacks a high-temperature setting stage, so thermal stress is not eliminated. Its overall performance is moderate, with a retention rate of 73.7%.

[0084] The single high-temperature curing (group 4) has the worst performance. Direct high temperature causes the resin to gel instantly and small molecules to volatilize violently, forming a large number of pores and microcracks. At the same time, it generates severe internal stress, making the material brittle, prone to aging and failure, with a retention rate of only 61.8%.

Claims

1. A fiberglass reinforced plastic (FRP) pipe material for oilfield water injection, characterized in that, It adopts a double-layer structure, consisting of a 1.5-2.0mm thick anti-corrosion and wear-resistant inner layer and a 2.5-3.0mm thick anti-aging outer layer from the inside out. The formula of each layer by weight is as follows: Corrosion-resistant and wear-resistant inner layer: 65-70 parts epoxy vinyl ester resin, 12-15 parts graphene-polytetrafluoroethylene composite micro powder, 6-8 parts nano silica, 4-5 parts nano zinc oxide, 2-3 parts isothiazolinone microbial inhibitor, 2.5-3.5 parts methyltetrahydrophthalic anhydride curing agent, and 1.2-1.8 parts dimethylaniline accelerator; Anti-aging outer layer: 58-62 parts bisphenol A type epoxy resin, 20-22 parts phenolic resin, 28-32 parts surface-modified glass fiber, 5-6 parts nano silicon carbide, 3.5-4.5 parts aromatic amine curing agent, 1.2-1.8 parts triethanolamine accelerator, 3.2-3.8 parts polysulfide rubber toughening agent, 2.2-2.8 parts ultraviolet absorber, 1.2-1.8 parts antioxidant, and 0.1-0.2 parts nano boron nitride; The modification method of the surface-modified glass fiber is as follows: alkali-free glass fiber is immersed in a mixed solution of silane coupling agent KH-560 and dopamine at a material-to-liquid ratio of 1:15-18 for 32-38 minutes. The mass ratio of KH-560 to dopamine in the mixed solution is 2:

1. After removal, it is dried at 82-88℃ for 2.0-2.8 hours.

2. The fiberglass reinforced plastic (FRP) pipeline material for oilfield water injection as described in claim 1, characterized in that, The preparation method of the graphene-polytetrafluoroethylene composite micro powder includes the following steps: (1) Raw material pretreatment: Weigh graphene and polytetrafluoroethylene powder at a mass ratio of 1:8.5-9.5, and place them separately in a vacuum oven and dry them for 1-1.5 h at 45-50℃ and a vacuum degree of 0.06-0.08MPa; (2) Preparation of rare earth pretreatment solution: Weigh 0.2-0.4% of lanthanide rare earth oxide La2O3, which accounts for 1:10-12 of the total mass of the mixed powder, add a mixture of anhydrous ethanol and deionized water in a volume ratio of 2:1, add dilute nitric acid to adjust the pH to 3.5-4.5, and ultrasonically disperse for 5-8 min to prepare a uniform rare earth pretreatment solution; (3) Premixing treatment: The dried graphene and polytetrafluoroethylene powder are placed in a high-speed mixer, and the prepared rare earth pretreatment liquid is added dropwise at a uniform speed. The mixture is premixed for 8-10 minutes at a speed of 1200-1500 r / min and a temperature of 25-30℃ to make the rare earth elements uniformly adhere to the powder surface. (4) Synergistic modification treatment: Add 0.3-0.5% of the total mass of the mixed powder to the high-speed mixer, adjust the speed to 1500-1800 r / min, raise the temperature to 40-45℃, and continue mixing for 15-18 min; (5) Vacuum drying: Place the synergistically modified mixed powder into a vacuum drying oven, control the drying temperature at 50-60℃ and the vacuum degree at 0.08-0.1MPa, and dry for 1-1.5h; (6) Post-processing: The dried powder is passed through a 200-250 mesh sieve to remove large particles that are not evenly dispersed. The powder is then treated with plasma for 1-2 minutes at a plasma power of 200-250W to obtain the graphene-polytetrafluoroethylene composite micro powder product.

3. The fiberglass reinforced plastic (FRP) pipeline material for oilfield water injection according to claim 2, characterized in that, In step (1), the graphene is pretreated with plasma with a plasma power of 200-250W and a treatment time of 3-5min.

4. The fiberglass reinforced plastic (FRP) pipeline material for oilfield water injection according to claim 2, characterized in that, The specific parameters for ultrasonic dispersion in step (2) are as follows: ultrasonic power 300-350W, ultrasonic time 18-20min, temperature controlled at 25-30℃ during ultrasonication, "intermittent ultrasonication" mode, ultrasonication for 3min, pause for 1min, and 0.1-0.2wt% of polyethylene glycol 400 as a dispersant; after ultrasonication, centrifugation is performed at 3000r / min for 5-8min.

5. The fiberglass reinforced plastic (FRP) pipeline material for oilfield water injection according to claim 1, characterized in that, In the corrosion-resistant and wear-resistant inner layer, the isothiazolinone microbial inhibitor is selected from a compound system of isothiazolinone and formaldehyde with a mass ratio of 3:

1.

6. The fiberglass reinforced plastic (FRP) pipeline material for oilfield water injection according to claim 1, characterized in that, In the anti-aging outer layer, the ultraviolet absorber is UV-327; the antioxidant is antioxidant 1010.

7. The fiberglass reinforced plastic (FRP) pipeline material for oilfield water injection according to claim 2, characterized in that, During the vacuum drying process, ventilation is performed once every 30 minutes, with each ventilation lasting 10-15 seconds.

8. The method for preparing oilfield water injection fiberglass reinforced plastic (FRP) pipe material according to any one of claims 1-7, characterized in that, Includes the following steps: (1) Raw material preparation: Weigh each component according to the formula; (2) Preparation of inner layer mixture: epoxy vinyl ester resin, graphene-polytetrafluoroethylene composite micro powder, nano silica and nano zinc oxide are placed in a high-speed mixer and mixed for 15-18 minutes at a speed of 850-950 r / min and a temperature of 26-29℃. Then microbial inhibitor, curing agent and accelerator are added and mixed for another 5-8 minutes to obtain corrosion-resistant and wear-resistant inner layer mixture. (3) Preparation of outer layer mixture: Bisphenol A type epoxy resin, phenolic resin, and polysulfide rubber toughening agent are put into a high-speed mixer and mixed for 10-12 minutes. Then, surface modified glass fiber, nano silicon carbide, nano boron nitride, ultraviolet absorber, antioxidant, curing agent and accelerator are added and mixed evenly to obtain anti-aging outer layer mixture. (4) Composite molding: The spray molding process is adopted. First, the inner layer mixture is evenly sprayed on the surface of the mold, and the thickness is controlled at 1.5-2.0 mm. Let it stand for 6-8 minutes to remove surface air bubbles. After the inner layer has been initially cured, the outer layer mixture is sprayed, and the thickness is controlled at 2.5-3.0 mm. (5) Segmented curing: The molded material is placed in a curing oven and cured in segments; (6) Post-processing: After natural cooling to 25-30℃, the material is taken out of the mold, polished, trimmed and screened to remove surface defects and obtain the finished product of oilfield water injection and polymer injection fiberglass pipe material.

9. The preparation method according to claim 8, characterized in that, The segmented curing process is as follows: first, the temperature is increased to 85-95℃ at a rate of 5-8℃ / min and held for 2-2.5 hours for low-temperature pre-curing; then, the temperature is increased to 125-135℃ at a rate of 6-9℃ / min and held for 4-4.5 hours for medium-temperature curing; finally, the temperature is increased to 160-170℃ at a rate of 6-9℃ / min and held for 1-1.5 hours for high-temperature setting; the cooling rate at each stage is controlled at 3-5℃ / min.

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