A slow-swelling oil-swelling self-expanding packer rubber and a preparation method thereof

Abstract

This invention relates to the field of functional polymer materials, and more particularly to a slow-expanding, oil-reactive self-expanding packer rubber and its preparation method. The slow-expanding, oil-reactive self-expanding packer rubber comprises the following raw materials in parts by weight: 15-35 parts hydrogenated nitrile rubber, 25-45 parts ethylene propylene diene monomer (EPDM) rubber, 2-8 parts maleic anhydride-grafted EPDM rubber, 15-35 parts carbon black, 5-15 parts silica, 3-8 parts organically modified montmorillonite, 15-25 parts oil-absorbing swelling system, 1-5 parts polyethylene glycol, 6-16 parts vulcanization active system, 4-11 parts vulcanization crosslinking system, and an anti-aging system. Through pre-dispersion of the oil-absorbing swelling masterbatch and segmented mixing processes, the slow-expanding, oil-reactive self-expanding packer rubber is prepared, exhibiting excellent properties such as high expansion rate, high temperature resistance, and slow expansion.

Description

Technical Field

[0001] This invention relates to the field of functional polymer materials, and in particular to a slow-expanding, oil-insensitive, self-expanding packer rubber and its preparation method. Background Technology

[0002] In drilling and oil production engineering, self-expanding packers are key tools for achieving staged well completion and enhancing production and injection. When oil-inducing self-expanding rubber comes into contact with oil-based media, oil molecules enter the rubber through capillary diffusion and surface adsorption, causing the rubber to expand in volume, thereby achieving a sealing effect. Compared with traditional compression packers, oil-inducing self-expanding packers have significant advantages such as simple structure, reliable setting, no need for additional setting tools, and adaptability to wellbore shape.

[0003] However, existing oil-absorbing self-expanding packer rubbers have the following technical defects: ① Excessively fast expansion rate: Traditional oil-absorbing expanding rubbers expand rapidly upon contact with oil, reaching saturation within hours. While rapid expansion is suitable for quick plugging, when used for downhole packing, the excessively fast expansion rate leads to rubber stress concentration, premature failure of the sealing element, and insufficient operating window time for downhole tubing deployment. ② Insufficient high-temperature resistance: As oil extraction progresses towards deep and ultra-deep wells (depths exceeding 5000m), bottom hole temperatures can reach 150-250℃. Existing oil-absorbing expanding rubbers are prone to thermo-oxidative aging at high temperatures, resulting in a sharp decline in mechanical and expansion properties. ③ Difficulty in balancing expansion ratio and mechanical properties: High expansion ratios typically require the addition of large amounts of oil-absorbing resin, but this reduces the rubber's mechanical properties, leading to seal element failure under downhole high-pressure environments (up to 100MPa or higher). ④ Difficulty in controlling expansion characteristics: Existing technologies cannot achieve precise control of expansion rate and expansion ratio, and cannot meet the personalized requirements of packer expansion characteristics under different downhole conditions (temperature, pressure, oil properties).

[0004] To address the aforementioned issues, developing a packer rubber material that simultaneously meets the requirements of high expansion rate, high temperature resistance, slow expansion, and self-expansion upon contact with oil, and achieving controllable expansion characteristics, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To meet the requirements of high expansion rate, high temperature resistance, slow expansion, and self-expansion upon contact with oil in self-expansion packer rubber, this application provides a slow-expansion type self-expansion packer rubber upon contact with oil and its preparation method. This rubber material exhibits slow and continuous expansion characteristics in high-temperature (150-180℃) oil media, with a controllable expansion rate and a high final expansion ratio. It also has good mechanical properties and high-temperature aging resistance, meeting the needs of deep well and ultra-deep well packer operations.

[0006] In the first aspect, this application provides a slow-expanding, oil-sensitive, self-expanding packer rubber, employing the following technical solution: A slow-expanding, oil-reactive self-expanding packer rubber comprises the following raw materials in parts by weight: 15-35 parts hydrogenated nitrile rubber, 25-45 parts ethylene propylene diene monomer (EPDM) rubber, 2-8 parts maleic anhydride-grafted EPDM rubber, 15-35 parts carbon black, 5-15 parts silica, 3-8 parts organically modified montmorillonite; 15-25 parts oil-absorbing and expanding system, 1-5 parts polyethylene glycol, 6-16 parts vulcanization active system, and 4-11 parts vulcanization crosslinking system.

[0007] By adopting the above scheme, the oil absorption expansion system and polyethylene glycol work together to achieve a "promotion-inhibition" bidirectional regulation mechanism, which can slowly and continuously expand in high-temperature oil media at 150℃. The expansion rate is controlled at 52-78% after 2 hours and reaches 186-218% after 72 hours, meeting the stringent requirements of deep well operations for the operating window time. The multi-scale physical reinforcement network of nano-montmorillonite and micron hollow microspheres ensures that high expansion is maintained while maintaining excellent mechanical properties, with a tensile strength of 14.8-16.5MPa and a tear strength of 33-36kN / m, meeting the requirements of downhole high-pressure sealing, and achieving a synergistic unity of high expansion rate, high temperature resistance, and slow expansion.

[0008] Preferably, the hydrogenated nitrile butadiene rubber has an acrylonitrile content of 28-43% and a hydrogenation degree of ≥95%; the third monomer of the ethylene propylene diene monomer (EPDM) rubber is ethylidene norbornene, with an ENB content of 4-8%.

[0009] Preferably, the interface compatibilizer is maleic anhydride-grafted EPDM rubber with a grafting rate of 0.5-1.0%.

[0010] By adopting the above scheme, EPDM-g-MAH (maleic anhydride-grafted EPDM rubber) can significantly improve the interfacial bonding force between polymer materials and inorganic fillers (carbon black, silica, organically modified montmorillonite), resulting in more uniform dispersion of reinforcing fillers in the rubber matrix. In the blend system of hydrogenated nitrile butadiene rubber and EPDM rubber, EPDM-g-MAH significantly improves the physical and mechanical properties of the blend, such as tensile strength, stress at a given elongation, and tensile strength at break, by reducing the interfacial tension between the two phases. Simultaneously, the addition of a compatibilizer helps to form a more stable blend structure, improves the heat aging resistance of the material, and enables the blend to maintain excellent dimensional stability and sealing performance in high-temperature oil media at 150℃.

[0011] Preferably, the nano-reinforcing component is organically modified montmorillonite with an interlayer spacing of 2-5 nm and a cation exchange capacity of 90-120 meq / 100g.

[0012] By adopting the above scheme, the interlayer spacing of organically modified montmorillonite is expanded after intercalation modification, making it easier to form intercalated or exfoliated nanostructures in the rubber matrix. This significantly improves the tensile strength and tear strength of the composite material even with low filler content. This interlayer spacing range ensures effective intercalation of polymer molecular chains, and the cation exchange capacity guarantees sufficient intercalation of the modifier, enabling uniform dispersion of nano-montmorillonite in the hydrogenated nitrile butadiene rubber and EPDM rubber blend system, achieving synergistic enhancement of mechanical, thermal stability, and barrier properties.

[0013] Preferably, the oil-absorbing and swelling system comprises the following raw materials in parts by weight: 10-15 parts of polyvinyl chloride-grafted polystyrene and 5-10 parts of modified hollow glass microspheres.

[0014] Preferably, the preparation of polyvinyl chloride-grafted polystyrene includes the following steps: dissolving polyvinyl chloride and polystyrene in an organic solvent at a mass ratio of 1:(0.5-1), wherein the amount of organic solvent is 5-8 times the total mass of polyvinyl chloride and polystyrene, stirring until completely dissolved, then adding anhydrous aluminum trichloride catalyst, wherein the amount of catalyst is 3-5% of the total mass of polyvinyl chloride and polystyrene, and stirring and dispersing evenly under nitrogen or argon protection; placing the reaction system in a microwave reactor to graft polystyrene onto the polyvinyl chloride molecular chain; after the reaction is completed, pouring the reaction solution into 3-5 times the volume of ethanol or methanol to precipitate, filtering, washing with ethanol 3-5 times, and drying in a vacuum drying oven at 60-80℃ for 12-24 hours to obtain polyvinyl chloride-grafted polystyrene.

[0015] Preferably, the organic solvent is selected from any one of tetrahydrofuran, cyclohexanone, and dimethylformamide.

[0016] Preferably, the microwave irradiation conditions are: microwave power 400-500 W, reaction temperature 60-80℃, and reaction time 30-60 minutes.

[0017] Preferably, the grafting rate of the polyvinyl chloride-grafted polystyrene is 20-30%.

[0018] By employing the above-mentioned scheme, polyvinyl chloride-grafted polystyrene prepared by microwave irradiation grafting can achieve a grafting rate of 20-30%. This high grafting rate endows the oil-absorbing resin with a rich styrene branched structure, providing numerous oil-absorbing active sites and resulting in an oil absorption ratio of 20-30 times. Simultaneously, the modified hollow glass microspheres form a physical barrier within the rubber matrix, creating an "oil absorption-slow expansion" synergistic mechanism with the polyvinyl chloride-grafted polystyrene. This mechanism extends the diffusion path of oil molecules through the hollow microspheres, achieving slow and continuous expansion characteristics.

[0019] Preferably, the modified hollow glass microspheres are hollow glass microspheres surface-treated with a silane coupling agent, and the particle size range of the modified hollow glass microspheres is 10-150 μm, the wall thickness is 1-2 μm, and the true density is 0.1-0.2 g / cm³. 3 .

[0020] By adopting the above scheme, hollow glass microspheres, after being surface modified with silane coupling agent, form chemical bonds with the rubber matrix, improve the interfacial bonding between inorganic fillers and organic phases, avoid the decline in mechanical properties caused by high-filling oil-absorbing resin, and meet the downhole high-pressure sealing requirements.

[0021] Preferably, the vulcanization active system comprises the following raw materials in parts by weight: 3-8 parts zinc oxide, 1-3 parts stearic acid, and 2-5 parts metal oxide composite agent.

[0022] Preferably, the metal oxide composite agent is a mixture of magnesium oxide, calcium oxide and lanthanum oxide, with a mass ratio of (5-7):(2-4):(1-2).

[0023] By employing the above-mentioned vulcanization active system: zinc oxide reacts with stearic acid to generate zinc stearate, which, together with magnesium oxide and calcium oxide, forms a main-auxiliary activation mechanism, significantly reducing the activation energy of the peroxide vulcanizing agent and increasing the crosslinking density; at the same time, the magnesium oxide and calcium oxide dual components synergistically absorb acidic substances generated during vulcanization and high-temperature aging, preventing the degradation of crosslinking bonds; lanthanum oxide, as a rare earth element, forms a stable complex with the decomposition products of peroxide, extending the lifespan of the vulcanization active center, making the crosslinking network more uniform and stable, and meeting the stringent requirements for high-temperature aging resistance under deep well conditions of 150-250℃.

[0024] Preferably, the vulcanization crosslinking system comprises the following raw materials in parts by weight: 2-6 parts of peroxide vulcanizing agent and 2-5 parts of co-crosslinking agent.

[0025] Preferably, the peroxide vulcanizing agent is selected from one or more of dicumyl peroxide and bis(tert-butylperoxyisopropyl)benzene; the co-crosslinking agent is selected from one or more of triallyl isocyanurate and trimethylolpropane trimethacrylate.

[0026] By adopting the above-mentioned vulcanization crosslinking system, the peroxide vulcanizing agent decomposes at high temperature to generate free radicals, which triggers the crosslinking of rubber molecular chains to form a stable carbon-carbon bond network. Compared with the sulfur vulcanization system, it has better heat and oxygen aging resistance. The crosslinking agent participates in the crosslinking reaction, improves the crosslinking efficiency and crosslinking density, and enables the vulcanized rubber to form a uniform and dense three-dimensional network structure.

[0027] Preferably, the slow-expanding, oil-insensitive self-expanding packer rubber further includes an anti-aging system: 1-3 parts of antioxidant RD and 1-2 parts of antioxidant MB.

[0028] By adopting the above-mentioned anti-aging system, the following technical effects can be achieved: Antioxidant RD (2,2,4-trimethyl-1,2-dihydroquinoline polymer) and antioxidant MB (2-thiol-benzoimidazole) form a synergistic protection mechanism. The former provides highly efficient protection against thermo-oxidative aging, while the latter has the dual functions of resisting thermo-oxidative aging, resisting copper damage, and resisting variable valence metal catalytic degradation. The combined use of the two can cover a wider temperature range and aging type, significantly inhibit the oxidative chain breaking reaction of rubber molecular chains in high-temperature oil media, and delay the degradation of cross-linked networks.

[0029] Secondly, this application provides a method for preparing a slow-expanding, oil-sensitive self-expanding packer rubber, employing the following technical solution: Preparation of S1 oil-absorbing and swelling masterbatch: Weigh polyvinyl chloride grafted polystyrene, modified hollow glass microspheres and polyethylene glycol according to the formula ratio, put them into an internal mixer, and mix them at 80-100℃ for 5-10 minutes to make the polyvinyl chloride grafted polystyrene melt and wrap the modified hollow glass microspheres to form oil-absorbing and swelling masterbatch. S2 Stage 1 Mixing: Hydrogenated nitrile rubber, EPDM rubber, and maleic anhydride-grafted EPDM rubber are put into an internal mixer and plasticized for 2-3 minutes; carbon black, silica, organic modified montmorillonite, zinc oxide, stearic acid, metal oxide composite agent, and anti-aging system are added and mixed for 5-8 minutes. The discharge temperature is controlled at 140-160℃ to obtain stage 1 compound. S3 Two-stage mixing: Pass the first-stage compound from step S2 through a two-roll mill 2-3 times, add the oil-absorbing and expanding masterbatch prepared in step S1, mix evenly, then add the peroxide vulcanizing agent and crosslinking agent, and continue mixing until uniform; pass the compound through a two-roll mill 5-8 times in a triangular shape, pass it through a two-roll mill 3-5 times, adjust the roller gap and sheet it to obtain the compounded rubber sheet. S4 vulcanization molding: After vulcanizing the compounded rubber sheet from step S3 on a flat vulcanizing machine, it is naturally cooled to room temperature and left to stand for 24 hours to obtain a slow-expanding, oil-inducing self-expanding packer rubber.

[0030] Preferably, the preparation method of the slow-expanding self-expanding sealer rubber in oil includes a second vulcanization after vulcanization molding in step S3. The vulcanized rubber is naturally cooled to room temperature and left to stand for 24 hours. Then, it is placed in a forced-air drying oven and treated at 150°C for 2-4 hours, followed by oven cooling.

[0031] Preferably, the S3 vulcanization molding process involves a vulcanization temperature of 170-185℃, a vulcanization pressure of 10-15 MPa, and a vulcanization time of 8-15 minutes.

[0032] By employing the above preparation method, firstly, the pre-dispersion process of the oil-absorbing and expanding masterbatch allows polyvinyl chloride-grafted polystyrene to melt-encapsulate modified hollow glass microspheres, forming a "core-shell" structure. This, in conjunction with polyethylene glycol, constructs a bidirectional "promotion-inhibition" regulatory mechanism, controlling the expansion rate at 50-80% within 2 hours and reaching 175-225% within 24 hours, achieving precise and controllable expansion rate. Secondly, the segmented mixing process optimizes the dispersion and crosslinking efficiency of the reinforcing filler, resulting in excellent mechanical properties. Finally, the two-stage vulcanization post-treatment further improves the crosslinking density and eliminates internal stress, significantly enhancing the high-temperature aging resistance and fully meeting the stringent requirements of packer sealing materials under high-temperature and high-pressure conditions in deep and ultra-deep wells (150-250℃).

[0033] In summary, this application has the following beneficial effects: 1. This application, through the compounding of various components, prepares a slow-expanding, self-expanding packer rubber with excellent properties such as high expansion rate, high temperature resistance, and slow expansion. First, by using hydrogenated nitrile rubber and EPDM rubber as the rubber matrix, combined with maleic anhydride-grafted EPDM rubber interface compatibilizer, the compatibility between the two phases is significantly improved, forming a stable blend system. Organically modified montmorillonite, carbon black, and silica construct a nano-micro multi-scale reinforcing network, resulting in excellent mechanical properties. Second, a compound of PVC-grafted polystyrene and modified hollow glass microspheres is used as the oil-absorbing expansion system. The PVC-g-PS grafting rate is 20-30%, resulting in a high oil absorption ratio. The modified hollow microspheres form a physical barrier, and the two work synergistically to achieve bidirectional regulation of "promotion-inhibition," allowing for precise control of the expansion rate. Third, the rare earth-reinforced metal oxide composite agent and the crosslinking agent vulcanization system work synergistically to form a stable carbon-carbon crosslinking network, meeting the requirements of high-temperature working conditions in deep wells at 150-250℃.

[0034] 2. The preparation method of the slow-expanding, oil-sensitive self-expanding packer rubber of this application involves a pre-dispersion process of the oil-absorbing and expanding masterbatch, which melt-encapsulates modified hollow microspheres into a "core-shell" structure. Oil molecules first dissolve the oil-absorbing resin layer and then gradually penetrate, forming a dual slow-expansion mechanism with the physical barrier of the hollow microspheres, precisely controlling the expansion rate. Secondly, in the segmented mixing process, the first stage of mixing completes the filler dispersion at a high temperature of 140-160℃, while the second stage of mixing adds the vulcanizing agent at a low temperature to avoid the risk of scorching, ensuring uniform dispersion of the reinforcing system and efficient construction of the crosslinking network. Thirdly, the second-stage vulcanization post-treatment is carried out at 150℃ for 2-4 hours, further improving the crosslinking density, eliminating internal stress, and improving the high-temperature aging resistance to a retention rate of over 92%. The entire preparation process requires no additional solvents, has no waste gas or wastewater discharge, and the vulcanization time is 8-15 minutes, resulting in high production efficiency, environmental friendliness, and suitability for industrial mass production. Detailed Implementation

[0035] The technical solution of this application is further illustrated by specific embodiments below. These specific embodiments do not represent a limitation on the scope of protection of this application. Any non-essential modifications and adjustments made by others based on the concept of this application still fall within the scope of protection of this application.

[0036] Unless otherwise specified, the experimental methods shown in the following examples are conventional methods. All reagents and materials shown are commercially available products.

[0037] Hydrogenated nitrile butadiene rubber: Arlanxeo, model: Therban® 3607, acrylonitrile content: 34.5-37.5 wt%, degree of hydrogenation: ≤0.9%; EPDM rubber: Arlanxeo, model: Keltan® 2750, ENB content 7.8 wt%, ethylene content 48 wt%; Maleic anhydride-grafted EPDM rubber, Jiangsu Sirida TRD-359EP, grafting rate 0.6-1.0%; Carbon black: Tianjin Huayuan Chemical Technology Co., Ltd., Model: N220, CAS: 133-86-4; Silica: Shandong Kasong New Material Co., Ltd., Product No.: SiO2; Organically modified montmorillonite: Guangzhou Zhanfei Chemical Technology Co., Ltd., Model: BP-186; Silane-modified hollow glass microspheres: Shanghai Huijing Asia Nanomaterials Co., Ltd., model: PW2, particle size 10-150μm, wall thickness 1-2μm, true density 0.08-0.25g / cm³; Polyethylene glycol: Jinan Guoshi Weiye Chemical Co., Ltd., Model: PEG-6000, CAS: 25322-68-3; Zinc oxide: Longyou Shengfa Rubber & Plastics Additives Co., Ltd., Model: Rubber grade zinc oxide, CAS: 1314-13-2; Stearic acid: Dongguan Zetai Chemical Technology Co., Ltd., CAS: 57-11-4, Model: 1801, Melting point 67-69℃; DCP (Dicumyl peroxide): Hongbaoli Group Co., Ltd., Model: DCP, CAS: 80-43-3, Purity ≥99%, White crystalline, Melting point ≥39℃; TAIC (Trylyl Isocyanurate): Taizhou Huangyan Donghai Chemical Co., Ltd., CAS: 1025-15-6, content ≥95%; Antioxidant RD (2,2,4-trimethyl-1,2-dihydroquinoline polymer): Shijiazhuang Jiujia Chemical Co., Ltd., CAS: 26780-96-1, Model: Antioxidant RD, Softening point 80-100℃; Antioxidant MB (2-Mitol-based Benzoimidazole): Shanghai Chengjin Chemical Co., Ltd., Model: Antioxidant MB, CAS: 583-39-1, Initial melting point ≥290℃, Purity ≥98%.

[0038] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0039] Preparation Example Preparation Example 1: Preparation of Polyvinyl Chloride-Grafted Polystyrene 10 kg of polyvinyl chloride (PVC) and 5 kg of polystyrene (PS) were dissolved in 75 kg of tetrahydrofuran and stirred until completely dissolved to obtain a mixed solution. 0.45 kg of anhydrous aluminum trichloride catalyst was added to the mixed solution and stirred and dispersed evenly under nitrogen protection. The reaction system was placed in a microwave reactor, with a microwave power of 400 W and a reaction temperature of 60 °C. The reaction was irradiated with microwaves for 30 min to graft polystyrene onto the PVC molecular chain. After the reaction was completed, the reaction solution was poured into 3 times its volume of ethanol to precipitate the polystyrene. The precipitate was filtered, washed three times with ethanol, and dried in a vacuum drying oven at 60 °C for 12 h to obtain PVC-grafted polystyrene. The grafting rate of the PVC-grafted polystyrene was 20.5%, and the oil absorption ratio was 22 times.

[0040] Preparation Example 2: Preparation of Polyvinyl Chloride-Grafted Polystyrene 10 kg of polyvinyl chloride (PVC) and 7.5 kg of polystyrene were dissolved in 87.5 kg of cyclohexanone and stirred until completely dissolved to obtain a mixed solution. 0.7 kg of anhydrous aluminum trichloride catalyst was added to the mixed solution and stirred and dispersed evenly under nitrogen protection. The reaction system was placed in a microwave reactor, with a microwave power of 450 W and a reaction temperature of 70 °C. The reaction was irradiated with microwaves for 45 min to graft polystyrene onto the PVC molecular chain. After the reaction, the reaction solution was poured into 4 times its volume of methanol to precipitate the polystyrene. The precipitate was filtered, washed 4 times with ethanol, and dried in a vacuum drying oven at 70 °C for 18 h to obtain PVC-grafted polystyrene. The grafting rate of the PVC-grafted polystyrene was 25.3%, and the oil absorption ratio was 26 times.

[0041] Preparation Example 3: Preparation of Polyvinyl Chloride-Grafted Polystyrene 10 kg of polyvinyl chloride (PVC) and 10 kg of polystyrene were dissolved in 160 kg of dimethylformamide and stirred until completely dissolved to obtain a mixed solution. Ten parts of anhydrous aluminum trichloride catalyst were added to the mixed solution and stirred and dispersed evenly under argon protection. The reaction system was placed in a microwave reactor, and the microwave power was set to 500 W, the reaction temperature to 80 °C, and the reaction was irradiated with microwaves for 60 min to graft polystyrene onto the PVC molecular chain. After the reaction was completed, the reaction solution was poured into 5 times its volume of ethanol to precipitate, filtered, washed 5 times with ethanol, and dried in a vacuum drying oven at 80 °C for 24 h to obtain PVC-grafted polystyrene. The grafting rate of the PVC-grafted polystyrene was 29.2%, and the oil absorption ratio was 31 times.

[0042] Example

[0043] Example 1 A method for preparing a slow-expanding, oil-sensitive self-expanding packer rubber, the preparation method is as follows: Preparation of S1 oil-absorbing and swelling masterbatch: Weigh polyvinyl chloride-grafted polystyrene, modified hollow glass microspheres and polyethylene glycol according to the formula ratio, put them into an internal mixer and mix at 80°C for 10 minutes to melt and encapsulate the modified hollow glass microspheres to form oil-absorbing and swelling masterbatch.

[0044] S2 First-stage compounding: Hydrogenated nitrile rubber, EPDM rubber and maleic anhydride-grafted EPDM rubber are put into an internal mixer and plasticized for 2 minutes; carbon black, silica, organic modified montmorillonite, zinc oxide, stearic acid, metal oxide composite agent and anti-aging system are added and mixed for 5 minutes. The discharge temperature is controlled at 140℃ to obtain the first-stage compound. S3 Two-stage mixing: The first-stage compound from step S2 is passed through a two-roll mill three times, and the oil-absorbing and expanding masterbatch prepared in step S1 is added. After mixing evenly, peroxide vulcanizing agent and crosslinking agent are added, and mixing is continued until uniform. The compound is then passed through a two-roll mill five times in a triangular shape and three times in a thin pass. The roller gap is adjusted to produce the compound sheet.

[0045] S4 Vulcanization molding: The compounded rubber sheet from step S3 is vulcanized on a flat vulcanizing machine at a vulcanization temperature of 170℃, a vulcanization pressure of 10MPa, and a vulcanization time of 8min. After vulcanization, it is naturally cooled to room temperature and left to stand for 24h. Then it is placed in a forced-air drying oven and treated at 150℃ for 2h. After cooling in the oven, a slow-expansion type oil-inducing self-expanding packer rubber is obtained.

[0046] The composition and dosage of the slow-expanding, oil-reactive self-expanding packer rubber are shown in Table 1, and the preparation method and processing conditions of the slow-expanding, oil-reactive self-expanding packer rubber are shown in Table 2.

[0047] The PVC-g-PS was prepared according to the scheme of Preparation Example 1; the metal oxide composite agent was prepared according to the ratio of magnesium oxide: calcium oxide: lanthanum oxide = 5:2:1.

[0048]

[0049] Example 2 The difference from Example 1 is that: The composition and dosage of the slow-expanding, oil-reactive self-expanding packer rubber are shown in Table 1, and the preparation method and processing conditions of the slow-expanding, oil-reactive self-expanding packer rubber are shown in Table 2. The PVC-g-PS was prepared according to the scheme of Preparation Example 2; the metal oxide composite agent was prepared according to the ratio of magnesium oxide: calcium oxide: lanthanum oxide = 6:3:1.5.

[0050] Example 3 The difference from Example 1 is that: The composition and dosage of the slow-expanding, oil-reactive self-expanding packer rubber are shown in Table 1, and the preparation method and processing conditions of the slow-expanding, oil-reactive self-expanding packer rubber are shown in Table 2. The PVC-g-PS was prepared according to the scheme of Preparation Example 3; the metal oxide composite agent was prepared according to the ratio of magnesium oxide: calcium oxide: lanthanum oxide = 7:4:2.

[0051] Example 4 The difference from Example 2 is that: The rubber component of the slow-expanding, oil-sensitive self-expanding packer also includes an anti-aging system: 1 kg of antioxidant RD and 1 kg of antioxidant MB.

[0052] Example 5 The difference from Example 2 is that: The rubber component of the slow-expanding, oil-sensitive self-expanding packer also includes an anti-aging system: 2 kg of antioxidant RD and 1.5 kg of antioxidant MB.

[0053] Example 6 The difference from Example 2 is that: The rubber component of the slow-expanding, oil-sensitive self-expanding packer also includes an anti-aging system: 3 kg of antioxidant RD and 2 kg of antioxidant MB.

[0054] Comparative Example Comparative Example 1 The difference from Example 2 is that no modified hollow glass microspheres are added.

[0055] Comparative Example 2 The difference from Example 2 is that polyethylene glycol is not added.

[0056] Comparative Example 3 The difference from Example 2 is that no metal composite agent is added.

[0057] Comparative Example 4 The difference from Example 2 is that no PVC-g-PS is added.

[0058] Comparative Example 5 The difference from Example 2 is that no DCP is added.

[0059] Comparative Example 6 The difference from Example 2 is that TAIC is not added.

[0060] Comparative Example 7 The difference from Example 5 is that the antioxidant RD is not added.

[0061] Hardness (Shore A): Tested according to GB / T 531.1-2008; Tensile strength and elongation at break: Tested according to GB / T528-2009; Tear strength: Tested according to GB / T 529-2008; Volume expansion rate at 150℃×2h, 150℃×24h, and 150℃×72h: Tested according to GB / T 1690-2010; Tensile strength retention rate after thermo-oxidative aging at 150℃×168h: Tested according to GB / T 3512-2014.

[0062] The metal-coated products prepared by the bonding methods of Examples 1-6 and Comparative Examples 1-7 were subjected to the above performance tests, and the test results are shown in Table 3.

[0063]

[0064] As shown in Table 3, the performance test results of Example 2 indicate that its tensile strength is 16.5 MPa, tear strength is 36 kN / m, and hardness is 65 Shore A. The volume expansion rate is 62% after 150℃ for 2 hours, 192% after 150℃ for 24 hours, and 202% after 150℃ for 72 hours. The tensile strength retention rate after aging is 82%. All properties are well-balanced and excellent. The 62% expansion rate after 2 hours demonstrates significant slow-expansion characteristics, and the 192% expansion rate after 24 hours ensures a high expansion ratio. This verifies that when the HNBR / EPDM ratio is 25:35 and the PVC-g-PS grafting rate is 25.3%, the optimal balance between mechanical properties, expansion characteristics, and high-temperature resistance can be achieved, indicating that the formulation design is reasonable and feasible.

[0065] Example 5, based on Example 2, added antioxidants RD and MB. Its tensile strength was 16.9 MPa, and its tear strength was 37 kN / m, representing increases of 2.4% and 2.8% respectively compared to Example 2. The expansion rate was 60% at 150℃ for 2 hours, 188% at 150℃ for 24 hours, and 198% at 150℃ for 72 hours, maintaining good slow-expansion characteristics and high expansion ratio. The tensile strength retention rate after aging was as high as 94%, an increase of 12 percentage points compared to Example 2. It exhibited optimal overall performance, achieving a synergistic unity of high expansion rate, high temperature resistance, and slow expansion. This demonstrates that the combined use of antioxidants RD and MB forms a synergistic protective mechanism. Antioxidant RD provides highly efficient thermo-oxidative aging protection, while antioxidant MB also has anti-copper damage and anti-catalytic degradation functions against variable valence metals. The synergistic effect of the two significantly inhibits the oxidative chain scission reaction of rubber molecular chains in high-temperature oil media, greatly improving high-temperature aging resistance while maintaining excellent expansion performance.

[0066] Compared with Example 2, without the addition of modified hollow glass microspheres, the expansion rate of Comparative Example 1 increased sharply from 62% to 135% in 2 hours, and was close to saturation (178%) in 24 hours, thus lacking the slow expansion characteristic; the expansion rate in 72 hours was only 182%, far lower than the 202% in Example 2, and the final expansion ratio was also significantly reduced; this indicates that the hollow glass microspheres form a physical barrier in the rubber matrix, prolonging the diffusion path of oil molecules, and are the key component for achieving slow expansion.

[0067] Compared to Example 2, Comparative Example 2, without the addition of polyethylene glycol, showed an expansion rate of 58% at 2 hours (slightly lower than 62% in Example 2), 185% at 24 hours (lower than 192% in Example 2), and 195% at 72 hours (lower than 202% in Example 2). This indicates that polyethylene glycol, as an expansion promoter, forms a bidirectional regulatory mechanism of "promotion-inhibition" with the hollow glass microspheres. Without polyethylene glycol, both the expansion rate and the final expansion ratio decreased, demonstrating that polyethylene glycol has a promoting effect on improving expansion performance.

[0068] Compared with Example 2, Comparative Example 3, without the addition of the metal oxide composite agent, showed a decrease in tensile strength from 16.5 MPa to 14.5 MPa and a decrease in tear strength from 36 kN / m to 31 kN / m; the tensile strength retention rate after aging dropped sharply from 82% to 68%, a decrease of 14 percentage points; indicating that the metal oxide composite agent has a triple effect of synergistic activation, acid absorption, and thermal stabilization; without this composite agent, the crosslinking density decreased and the high-temperature aging resistance deteriorated significantly.

[0069] Compared to Example 2, Comparative Example 4, without the addition of PVC-g-PS, showed a decrease in tensile strength from 16.5 MPa to 12.8 MPa, and tear strength from 36 kN / m to 28 kN / m; the 24-hour expansion rate decreased from 192% to 152%, and the 72-hour expansion rate was only 168%. This indicates that PVC-g-PS is the core component providing the high expansion ratio, and the 25.3% grafting rate endows it with abundant oil-absorbing active sites. Without PVC-g-PS, the expansion performance decreased significantly, and the mechanical properties were also reduced due to the lack of synergistic effect between the oil-absorbing resin and the rubber matrix.

[0070] Compared with Example 2, Comparative Example 5, without the addition of peroxide curing agent DCP, showed a decrease in tensile strength from 16.5 MPa to 13.2 MPa, tear strength from 36 kN / m to 30 kN / m, and retention rate after aging from 82% to 75%. DCP is the core of the peroxide curing system. Without DCP, the crosslinking reaction cannot proceed effectively, resulting in incomplete curing and a comprehensive decline in mechanical properties and aging resistance.

[0071] Compared with Example 2, Comparative Example 6, without the addition of the crosslinking co-crosslinking agent TAIC, showed a decrease in tensile strength from 16.5 MPa to 14.6 MPa, tear strength from 36 kN / m to 33 kN / m, and aging retention rate from 82% to 78%. This indicates that TAIC, as a crosslinking co-crosslinking agent, participates in the crosslinking reaction, improving crosslinking efficiency and crosslinking density; without TAIC, the crosslinking network is not dense enough, resulting in a decrease in both mechanical properties and aging resistance.

[0072] Compared with Example 5, Comparative Example 7 did not add antioxidant RD. The tensile strength retention rate after aging decreased from 94% to 86%, a decrease of 8 percentage points. The tensile strength decreased from 16.9 MPa to 16.4 MPa, indicating that antioxidant RD and MB form a synergistic protection mechanism. RD mainly provides protection against thermo-oxidative aging. Without RD, the protective effect is significantly reduced, proving that the combined use of antioxidants has a synergistic effect.

[0073] The above experimental results show that the slow-expanding, oil-sensitive self-expanding packer rubber prepared in this application has the following characteristics: First, the expansion rate is precisely controllable. In Example 5, the expansion rate at 150℃ for 2 hours was only 60%, reaching 188% after 24 hours and 198% after 72 hours, forming a typical "slow in the early stage and continuous in the later stage" expansion curve. In contrast, the expansion ratio of Comparative Example 2 without polyethylene glycol decreased, verifying the effectiveness of the "promotion-inhibition" bidirectional regulation mechanism. Second, it has excellent high-temperature resistance. The tensile strength retention rate of Example 5 after aging is as high as 94%, which is significantly higher than that of Comparative Example 3 (without metal composite). The rare earth-reinforced metal oxide composite agent (68%) increased by 26 percentage points compared to the antioxidant (68%), and by 8 percentage points compared to the 86% of Comparative Example 7 (without antioxidant RD). This demonstrates the synergistic effect of the rare earth-reinforced metal oxide composite agent and the dual antioxidants, which significantly inhibit high-temperature aging degradation through a triple mechanism of acid absorption, thermal stability, and free radical capture. Finally, mechanical properties and expansion ratio were synergistically improved. Example 5 showed a tensile strength of 16.9 MPa and a tear strength of 37 kN / m, which were 32% and 32% higher than Comparative Example 4 (without PVC-g-PS), respectively, achieving a balance between high expansion ratio and excellent mechanical properties. The technical solution of this application successfully achieves a synergistic balance between high expansion ratio, high temperature resistance, and slow expansion through the synergistic effect of each component, meeting the stringent requirements of packer sealing materials under high temperature and high pressure conditions of 150-250℃ in deep and ultra-deep wells.

[0074] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the present invention, they are protected by patent law.

Claims

1. A slow-expanding, oil-sensitive, self-expanding packer rubber, characterized in that, The raw materials include the following parts by weight: 15-35 parts hydrogenated nitrile rubber, 25-45 parts ethylene propylene diene monomer (EPDM) rubber, 2-8 parts maleic anhydride-grafted EPDM rubber, 15-35 parts carbon black, 5-15 parts silica, 3-8 parts organically modified montmorillonite, 15-25 parts oil-absorbing swelling system, 1-5 parts polyethylene glycol, 6-16 parts vulcanization active system, and 4-11 parts vulcanization crosslinking system.

2. The slow-expanding, oil-resistant self-expanding packer rubber according to claim 1, characterized in that, The oil-absorbing and swelling system comprises the following raw materials in parts by weight: 10-15 parts of polyvinyl chloride-grafted polystyrene and 5-10 parts of modified hollow glass microspheres.

3. The slow-expanding, oil-resistant self-expanding packer rubber according to claim 2, characterized in that, The preparation of polyvinyl chloride-grafted polystyrene includes the following steps: dissolving polyvinyl chloride and polystyrene in an organic solvent at a mass ratio of 1:(0.5-1), wherein the amount of organic solvent is 5-8 times the total mass of polyvinyl chloride and polystyrene, stirring until completely dissolved, then adding anhydrous aluminum trichloride catalyst, wherein the amount of catalyst is 3-5% of the total mass of polyvinyl chloride and polystyrene, and stirring and dispersing evenly under nitrogen or argon protection; placing the reaction system in a microwave reactor to graft polystyrene onto the polyvinyl chloride molecular chain; after the reaction is completed, pouring the reaction solution into 3-5 times the volume of ethanol or methanol to precipitate, filtering, washing with ethanol 3-5 times, and drying in a vacuum drying oven at 60-80℃ for 12-24 hours to obtain polyvinyl chloride-grafted polystyrene.

4. The slow-expanding, oil-resistant self-expanding packer rubber according to claim 2, characterized in that, The microwave irradiation conditions are: microwave power 400-500 W, reaction temperature 60-80℃, and reaction time 30-60 minutes.

5. The slow-expanding, oil-resistant self-expanding packer rubber according to claim 1, characterized in that, The vulcanization active system comprises the following raw materials in parts by weight: 3-8 parts zinc oxide, 1-3 parts stearic acid, and 2-5 parts metal oxide composite agent.

6. The slow-expanding, oil-resistant self-expanding packer rubber according to claim 5, characterized in that, The metal oxide composite agent is a mixture of magnesium oxide, calcium oxide and lanthanum oxide, with a mass ratio of (5-7):(2-4):(1-2).

7. The slow-expanding, oil-resistant self-expanding packer rubber according to claim 1, characterized in that, The vulcanization crosslinking system comprises the following raw materials in parts by weight: 2-6 parts peroxide vulcanizing agent and 2-5 parts co-crosslinking agent.

8. The slow-expanding, oil-resistant self-expanding packer rubber according to claim 1, characterized in that, The slow-expanding, oil-sensitive self-expanding packer rubber also includes an anti-aging system: 1-3 parts of antioxidant RD and 1-2 parts of antioxidant MB.

9. A method for preparing a slow-expanding, oil-resistant self-expanding packer rubber as described in any one of claims 1-8, characterized in that, It includes the following steps: Preparation of S1 oil-absorbing and swelling masterbatch: Weigh polyvinyl chloride grafted polystyrene, modified hollow glass microspheres and polyethylene glycol according to the formula ratio, put them into an internal mixer, and mix them at 80-100℃ for 5-10 minutes to make the polyvinyl chloride grafted polystyrene melt and wrap the modified hollow glass microspheres to form oil-absorbing and swelling masterbatch. S2 Stage 1 Mixing: Hydrogenated nitrile rubber, EPDM rubber, and maleic anhydride-grafted EPDM rubber are put into an internal mixer and plasticized for 2-3 minutes; carbon black, silica, organic modified montmorillonite, zinc oxide, stearic acid, metal oxide composite agent, and anti-aging system are added and mixed for 5-8 minutes. The discharge temperature is controlled at 140-160℃ to obtain stage 1 compound. S3 Two-stage mixing: Pass the first-stage compound from step S2 through a two-roll mill 2-3 times, add the oil-absorbing and expanding masterbatch prepared in step S1, mix evenly, then add the peroxide vulcanizing agent and crosslinking agent, and continue mixing until uniform; pass the compound through a two-roll mill 5-8 times in a triangular shape, pass it through a two-roll mill 3-5 times, adjust the roller gap and sheet it to obtain the compounded rubber sheet. S4 vulcanization molding: After vulcanizing the compounded rubber sheet from step S3 on a flat vulcanizing machine, it is naturally cooled to room temperature and left to stand for 24 hours to obtain a slow-expanding, oil-inducing self-expanding packer rubber.

10. The method for preparing the slow-expanding, oil-resistant self-expanding packer rubber according to claim 9, characterized in that, It also includes two-stage vulcanization, in which the vulcanized rubber is naturally cooled to room temperature and left to stand for 24 hours, then placed in a forced-air drying oven and treated at 150°C for 2-4 hours, and then cooled with the oven.

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