Polyglycolic acid composite material for oil and gas field soluble bridge plug and preparation method thereof

Abstract

This invention relates to the field of polymer composite materials technology, specifically disclosing a polyglycolic acid (PGA) composite material for soluble bridge plugs in oil and gas fields and its preparation method. The PGA composite material uses injection-grade PGA as the matrix, carbon fibers treated with organic solvents and silane coupling agents as the reinforcing phase, and adds the heat stabilizer Irganox 1010 and the chain extender ADR-4468. Furthermore, nano-SiO2 can be added as an auxiliary reinforcing phase, and aliphatic hyperbranched polyester HBP as a degradation-modifying phase. The preparation method includes raw material selection, PGA drying, carbon fiber surface treatment, stepwise melt blending, crushing and granulation, and injection molding. This composite material exhibits good mechanical properties while also considering melt processing adaptability and controllable degradation performance, and can be used to prepare soluble bridge plug mandrels, cones, slips, or sealing supports for oil and gas fields.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, and in particular to a polyglycolic acid composite material for soluble bridge plugs in oil and gas fields and its preparation method. Background Technology

[0002] Shale gas extraction is typically achieved through horizontal well fracturing technology, with bridge plugs being a key completion tool. Compared to traditional drillable bridge plugs, soluble bridge plugs can self-dissolve or degrade after fracturing without the need for drilling and grinding. Therefore, the material of soluble bridge plugs needs to possess sufficient mechanical strength during service and dissolve or degrade as expected after completing their sealing function.

[0003] Currently, commonly used materials for soluble bridge plugs include magnesium and aluminum alloys and their composites. However, the dissolution process of these metals relies on electrochemical corrosion, which easily leads to uneven dissolution and corrosion product deposition and blockage. Polyglycolic acid (PGA) is a biodegradable aliphatic polyester material and can be considered a potential alternative for soluble bridge plugs. However, pure PGA materials still suffer from problems in practical applications, such as easy thermal degradation during melt processing, insufficient toughness, limited service strength, and difficulty in controlling the degradation rate. These issues make it difficult to meet the comprehensive requirements of soluble bridge plugs for processing performance, pressure resistance, and controllable degradation performance. Therefore, there is an urgent need in this field to develop a PGA composite material that combines mechanical reinforcement, processing stability, and controllable degradation properties.

[0004] Chinese Patent Publication No. CN120484472A discloses a soluble bridge plug sealing ring and its preparation method. It uses silane-modified glass fiber reinforced PGA and introduces bisoxazoline, tributyl acetyl citrate and HMSN-ZnCl2 composite material to improve the sealing ring strength and control the performance of slow dissolution in the early stage and rapid dissolution in the later stage.

[0005] This shows that existing soluble bridge plug materials still face the problem of not being able to simultaneously achieve optimal performance, processing stability, and degradation rate. Summary of the Invention

[0006] To address the problems in the prior art, this invention provides a polyglycolic acid composite material for soluble bridge plugs in oil and gas fields and its preparation method.

[0007] To achieve the above objectives, the present invention provides a polyglycolic acid composite material for soluble bridge plugs in oil and gas fields, comprising the following components by weight: polyglycolic acid (PGA) as the balance, 5-20 parts of surface-treated carbon fiber, 1 part of heat stabilizer, and 1 part of chain extender; wherein the surface-treated carbon fiber is carbon fiber that has been cleaned with an organic solvent and then treated with a silane coupling agent, the heat stabilizer is the hindered phenolic antioxidant Irganox 1010, and the chain extender is the epoxy functionalized chain extender ADR-4468, with a total of 100 parts of each component.

[0008] This invention also provides a method for preparing the above-mentioned polyglycolic acid composite material for soluble bridge plugs in oil and gas fields, the specific steps of which are as follows: Step S1, raw material selection: injection molding grade PGA is selected as the modified matrix, carbon fiber is selected as the reinforcing phase, heat stabilizer Irganox 1010 and ADR-4468 are selected as processing stabilizers, and nano-SiO2 is optionally selected as the auxiliary reinforcing phase, and aliphatic hyperbranched polyester HBP is optionally selected as the degradation modified phase.

[0009] Step S2: Raw material pretreatment. The PGA matrix is ​​dried to obtain a dry PGA matrix. The carbon fiber is washed with acetone, dried, impregnated with silane coupling agent, and dried in sequence to obtain surface-treated carbon fiber.

[0010] Step S3, melt blending: PGA matrix, surface-treated carbon fiber, heat stabilizer Irganox 1010, chain extender ADR-4468, and optional nano-SiO2 and aliphatic hyperbranched polyester HBP are melt blended using an internal mixer to obtain a blended composite material.

[0011] Step S4, crushing and granulation: the blended material is transferred to a crusher for crushing, and then dried to obtain composite material particles.

[0012] Step S5, injection molding: The particulate composite material is transferred to an injection molding machine for injection molding to obtain a polyglycolic acid composite material suitable for soluble bridge plugs in oil and gas fields.

[0013] Furthermore, in step S1, the melt flow rate of the PGA matrix is ​​46.9 g / 10 min; the carbon fiber is T800 with a diameter of 6 μm; the particle size of nano-SiO2 is 7-40 nm; and the aliphatic hyperbranched polyester HBP has a molecular weight of 1100 g / mol and a functionality of 10-12.

[0014] Furthermore, in step S2, the impurities on the carbon fiber surface are washed using acetone solvent. The washing process is assisted by ultrasound for 30 minutes. After filtration, the carbon fiber is dried to obtain the washed carbon fiber.

[0015] Furthermore, in step S2, the washed carbon fibers are impregnated and modified in a silane coupling agent solution after hydrolysis. The process is assisted by ultrasound for 30 minutes to obtain the impregnated and modified carbon fibers. The silane coupling agent is KH550, the ratio of anhydrous ethanol to deionized water in the solvent is 7:3, the concentration of KH-550 is 1%, and it needs to be hydrolyzed by ultrasound for 30 minutes before use.

[0016] Furthermore, in step S2, the impregnated and modified carbon fiber is filtered and then dried at a drying temperature of 110°C. During the drying process, the machine is stopped for 5 minutes every 10 minutes. During the stop, the surface-modified carbon fiber is turned over. After the turning is completed, the drying continues for 1 hour to obtain surface-treated carbon fiber.

[0017] Furthermore, in step S3, the content of surface-modified carbon fiber is 5-20 parts, the content of heat stabilizer Irganox 1010 is 1 part, and the content of chain extender ADR-4468 is 1 part; when the composite material includes nano-SiO2, the content of nano-SiO2 is 0.5-1.5 parts; when the composite material includes aliphatic hyperbranched polyester HBP, the content of aliphatic hyperbranched polyester HBP is 0.5-2.5 parts; the PGA matrix is ​​the balance, and the total amount of all components is 100 parts.

[0018] Furthermore, step S3 includes: Step S31, first feeding and blending: PGA matrix and heat stabilizer Irganox 1010 are added and then melt-blended; Step S32, second feeding and blending, continue to add surface-modified carbon fibers and optional nano-SiO2 for melt blending; Step S33, third addition of feed and blending, continue to add chain extender ADR-4468 and optional aliphatic hyperbranched polyester HBP for melt blending.

[0019] Furthermore, in step S3, the internal mixer is heated to 230°C, rotated at 60 rpm, and mixed for 7 min; before melt mixing, the internal mixer is preheated to 220°C for 30-45 min.

[0020] Furthermore, in step S4, the drying temperature is 80°C and the drying time is 4 hours.

[0021] Furthermore, in step S5, the injection temperature is 230°C, the mold temperature is 90°C, the injection pressure is 0.5MPa, and the injection time is 8s.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention improves the mechanical properties of PGA by reinforcing and modifying it with surface-treated carbon fibers. After cleaning with acetone and treating with a silane coupling agent, the carbon fibers have fewer surface impurities and increased interfacial activity. This is beneficial for improving the dispersion and interfacial bonding of the carbon fibers in the PGA matrix, enhancing the stress transfer efficiency between the reinforcing phase and the matrix, and enabling the resulting composite material to better meet the stress requirements of soluble bridge plugs in oil and gas fields during setting, pressure bearing, and fracturing operations.

[0023] 2. This invention further achieves synergistic regulation of reinforcing and degradation properties by introducing nano-SiO2 and aliphatic hyperbranched polyester HBP. Nano-SiO2, as an auxiliary reinforcing phase, can improve the mechanical properties of the composite material; the aliphatic hyperbranched polyester HBP has a multi-terminal structure, which can regulate the hydrolytic degradation behavior of the PGA matrix, enabling the composite material to maintain good load-bearing capacity during service and possess controllable degradation properties after completing its sealing function, thereby meeting the dual requirements of soluble bridge plugs for service strength and post-operation failure.

[0024] 3. This invention utilizes the heat stabilizer Irganox 1010, the chain extender ADR-4468, and a stepwise addition melt blending process to improve the stability of PGA composites during melt processing. First, PGA is melt-blended with the heat stabilizer, which helps to slow down the thermal degradation of PGA during processing. Then, surface-treated carbon fibers and nano-SiO2 are added to ensure sufficient dispersion of the reinforcing phase. Finally, aliphatic hyperbranched polyester HBP and the chain extender ADR-4468 are added to reduce matrix degradation caused by premature action of HBP, and the chain extender compensates for molecular chain loss during processing, thereby obtaining a polyglycolic acid composite material with coordinated mechanical properties, processing stability, and degradation performance.

[0025] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0027] Figure 1 A flowchart of a method for preparing a polyglycolic acid composite material for soluble bridge plugs in oil and gas fields; Figure 2 A flowchart illustrating the carbon fiber pretreatment process in a method for preparing polyglycolic acid composite material for soluble bridge plugs in oil and gas fields; Figure 3 This is a flowchart illustrating the stepwise feeding process in the preparation of a polyglycolic acid composite material for soluble bridge plugs in oil and gas fields. Detailed Implementation

[0028] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the present invention will be further described below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Unless otherwise stated, the amounts of each component in the following embodiments and comparative examples are by mass, and the total amount of each component is 100 parts.

[0029] The polyglycolic acid PGA used in this embodiment of the invention is injection molding grade PGA with a melt flow rate of 46.9 g / 10 min; the carbon fiber used is T800 carbon fiber with a diameter of 6 μm; the particle size of the nano-SiO2 used is 7-40 nm; the number average molecular weight of the aliphatic hyperbranched polyester HBP used is 1100 g / mol, and the functionality is 10-12; the heat stabilizer used is Irganox 1010; and the chain extender used is ADR-4468.

[0030] Please see Figure 1 , Figure 1 This is a flowchart illustrating the preparation method of polyglycolic acid composite material for soluble bridge plugs in oil and gas fields according to an embodiment of the present invention.

[0031] The present invention provides a method for preparing polyglycolic acid composite materials for soluble bridge plugs in oil and gas fields, comprising: Polyglycolic acid (PGA) was dried at 80°C for 8 hours to obtain dried PGA.

[0032] Please see Figure 2 , Figure 2 This is a flowchart of the carbon fiber pretreatment process in the method for preparing composite materials for soluble bridge plugs in oil and gas fields, as described in an embodiment of the present invention.

[0033] Carbon fibers were added to acetone at a liquid-to-solid ratio of 10:1 and ultrasonically assisted cleaning was performed for 30 minutes to remove impurities from the carbon fiber surface. After cleaning, the carbon fibers were removed and dried at 80°C for 1 hour.

[0034] KH-550 silane coupling agent was prepared into a 1% (w / w) silane coupling agent solution, wherein the solvent was a mixture of anhydrous ethanol and deionized water, with a volume ratio of anhydrous ethanol to deionized water of 7:3. After ultrasonic-assisted hydrolysis of the silane coupling agent solution for 30 min, carbon fibers that had been washed with acetone and dried were added, with a liquid-to-solid ratio of carbon fibers to the silane coupling agent solution of 10:1. Ultrasonic treatment was continued for another 30 min. After treatment, the carbon fibers were removed and dried at 110℃ for 1 h. During the drying process, the drying process was stopped for 5 min every 10 min, and the carbon fibers were stirred during the stops. After drying, surface-treated carbon fibers were obtained.

[0035] Weigh out polyglycolic acid PGA, surface-treated carbon fiber, nano-SiO2, aliphatic hyperbranched polyester HBP, Irganox 1010 and chain extender ADR-4468 according to the formula shown in Table 1. When the amount of a certain component in Table 1 is 0 parts, the corresponding component is not added in the preparation step.

[0036] Please see Figure 3 , Figure 3 This is a flowchart illustrating the melt blending and stepwise feeding process in the preparation method of polyglycolic acid composite material for soluble bridge plugs in oil and gas fields, as described in an embodiment of the present invention.

[0037] Before melt blending, preheat the internal mixer to 220°C for 30-45 minutes.

[0038] Dry PGA and Irganox 1010 were added to a mixer and melt-blended for the first time at 230°C and 60 rpm. Then, surface-treated carbon fibers and nano-SiO2 were added and melt-blended for the second time. Finally, aliphatic hyperbranched polyester HBP and chain extender ADR-4468 were added and melt-blended for the third time. The blending time was 7 min to obtain the blended composite material.

[0039] The obtained blended composite material was transferred to a crusher for crushing and granulation to obtain composite material particles. The composite material particles were dried at 80°C for 4 hours, and then transferred to an injection molding machine for injection molding. During the injection molding process, the injection temperature was 230°C, the mold temperature was 90°C, the injection pressure was 0.5 MPa, and the injection time was 8 seconds, resulting in a polyglycolic acid composite material for soluble bridge plugs in oil and gas fields.

[0040] The group assignments for the embodiments and comparative examples are as follows: Table 1. Component ratios of the Examples and Comparative Examples The mechanical properties of the composite material were tested using an electronic universal testing machine. Tensile tests were conducted according to the testing specifications of GB / T 1040.2-2022, with a tensile speed of 5 mm / min. Five well-formed specimens without obvious defects were tested for each group of specimens. The tensile strength and elongation at break of the composite material were calculated based on the average value of the test results.

[0041] To investigate the degradation performance of PGA composites in an aqueous environment, a hydrolysis experiment was conducted on the PGA composites under simulated high-temperature aqueous media conditions. Samples of uniform size were cut from the same location of the same specimen, and their initial masses were weighed and recorded. The samples were placed in test tubes filled with 90°C pure water and then placed in a constant-temperature incubator to maintain a stable water temperature of 90°C. To minimize the impact of water evaporation on the experimental conditions, the samples were sealed with aluminum foil and placed in the incubator for constant-temperature degradation. Since PGA is a hydrophilic material, the samples underwent a certain degree of water absorption and swelling during degradation. To avoid interference from water absorption on the experimental results, the samples were removed after 72 hours of degradation, dried at 80°C for 8 hours, and their mass after drying was weighed and recorded. The mass loss rate was used to characterize the degradation performance of the samples, and the calculation formula is as follows: in, m 0 indicates the original mass of the sample block. m t The residual mass of the sample after degradation and drying.

[0042] Since the contents of carbon fiber, nano-SiO2, and other modified components vary in different embodiments, to facilitate comparison of the degradation degree of the PGA matrix in different composite systems, the mass loss rate is further recalculated based on the initial PGA content. This recalculation is used to characterize the relative loss degree of the PGA matrix when it is assumed that the mass loss mainly originates from the PGA matrix. The recalculation formula is as follows: in, ω PGA This represents the initial mass fraction of PGA in the sample. It should be noted that the PGA equivalent mass loss rate is used to compare the relative hydrolysis loss trend of the PGA matrix in different composite systems, and does not represent the absolute degradation rate of the PGA component.

[0043] The performance test results of Comparative Examples 1-2 and Examples 1-12 are as follows: Table 2. Performance test results of Comparative Examples 1-2 and Examples 1-12 As shown in Table 2, Examples 1-4 improved the mechanical properties of polyglycolic acid by adding different amounts of surface-treated carbon fibers; Examples 5-7 maintained the tensile strength of the composite material at a high level by further adding nano-SiO2, indicating that nano-SiO2 can play an auxiliary reinforcing role; The results of Examples 8-12 show that the PGA equivalent mass loss rate generally increases with the increase of HBP content, indicating that HBP can enhance the degradation regulation effect of the composite system; The tensile strength of the material decreases when the HBP content is high, indicating that the HBP content needs to be controlled within an appropriate range to balance mechanical properties and degradation performance.

[0044] This invention utilizes the synergistic effect of surface-treated carbon fibers, nano-SiO2, aliphatic hyperbranched polyester HBP, Irganox 1010, and chain extender ADR-4468 to enable polyglycolic acid composite materials to possess good mechanical properties, melt processing adaptability, and controllable degradation properties, making them suitable for soluble bridge plug materials in oil and gas fields.

Claims

1. A polyglycolic acid composite material for soluble bridge plugs in oil and gas fields, characterized in that, By weight, it includes the following components: polyglycolic acid PGA as the balance, surface-treated carbon fiber 5-20 parts, heat stabilizer 1 part, chain extender 1 part, and the total amount of all components is 100 parts.

2. The polyglycolic acid composite material for soluble bridge plugs in oil and gas fields according to claim 1, characterized in that, The surface-treated carbon fiber is carbon fiber that has been washed with acetone and then impregnated and modified with KH550 silane coupling agent. The heat stabilizer is hindered phenolic antioxidant Irganox 1010, and the chain extender is epoxy functionalized chain extender ADR-4468.

3. The polyglycolic acid composite material for soluble bridge plugs in oil and gas fields according to claim 1, characterized in that, The polyglycolic acid composite material also contains nano-SiO2, and the content of nano-SiO2 is 0.5-1.5 parts.

4. A polyglycolic acid composite material for soluble bridge plugs in oil and gas fields according to any one of claims 1-3, characterized in that, The polyglycolic acid composite material also includes aliphatic hyperbranched polyester HBP, wherein the content of aliphatic hyperbranched polyester HBP is 0.5-2.5 parts.

5. A method for preparing a polyglycolic acid composite material for soluble bridge plugs in oil and gas fields as described in any one of claims 1 to 4, characterized in that, include: Step S1: Injection molding grade PGA, carbon fiber, heat stabilizer Irganox 1010 and chain extender ADR-4468 are selected as base raw materials, and nano-SiO2 and aliphatic hyperbranched polyester HBP are optionally selected as modifying raw materials. Step S2: The polyglycolic acid PGA is dried to obtain dried PGA; the carbon fiber is washed and modified with silane coupling agent to obtain surface-treated carbon fiber. Step S3: Dry PGA, surface-treated carbon fiber, heat stabilizer, chain extender, and optional nano-SiO2 and aliphatic hyperbranched polyester HBP are melt-blended to obtain a blended composite material. Step S4: The blended composite material is crushed and granulated to obtain composite material particles; Step S5: The composite material particles are injection molded to obtain a polyglycolic acid composite material for soluble bridge plugs in oil and gas fields.

6. The method for preparing a polyglycolic acid composite material for soluble bridge plugs in oil and gas fields according to claim 5, characterized in that, The step S3 melt blending includes: Step S31: For the first feeding, polyglycolic acid (PGA) and heat stabilizer Irganox 1010 are added and melt-blended. Step S32: The second feeding continues with the addition of surface-treated carbon fibers and optional nano-SiO2 for melt blending; In step S33, the chain extender ADR-4468 and optional aliphatic hyperbranched polyester HBP are added for melt blending in the third feeding.

7. The method for preparing a polyglycolic acid composite material for soluble bridge plugs in oil and gas fields according to claim 5, characterized in that, In step S3, the melt blending temperature is 220-240℃, the rotation speed is 60-90rpm, and the blending time is 5-8min. Before melt blending, the internal mixer is preheated at 220℃ for 30-45min.

Images