Magnetic control rheological sealing material for oil casing thread and preparation method thereof

Abstract

The application belongs to the technical field of oil casing thread sealing, and discloses a magnetic control rheological sealing material for oil casing thread connection and a preparation method thereof, wherein components of the magnetic control rheological sealing material include, by mass, 50-60 wt% fluorosilicone gel, 30-40 wt% magnetic control particles, and the balance of fumed silica, zinc phosphate, graphene nanosheet and polytetrafluoroethylene micro powder, and the sum of the components in the formula is 100 wt% by mass. The magnetic control rheological sealing material can realize self-adaptive sealing in the screwing process, dynamically fill the thread gap, and combine the polymer matrix, mechanical locking and solid filler to ensure excellent air tightness, corrosion resistance and long-term durability, thereby solving the problems of poor air tightness, insufficient pressure resistance, high extrusion rate, poor corrosion resistance and poor environmental protection of the traditional sealing agent in high-temperature, high-pressure and strong corrosion environment.

Description

Technical Field

[0001] This application belongs to the field of oil casing thread sealing technology, and specifically relates to a magnetic rheological sealing material for oil casing thread connection and its preparation method. Background Technology

[0002] Threaded connections for oil and gas well casing and tubing are widely used in oil and gas exploration and production. Their reliable quality ensures the airtightness, structural integrity, and long-term reliability of the downhole tubing. The performance of threaded sealing technology directly affects the safety and economic efficiency of downhole operations. Research and field reports show that threaded seal failure rates vary significantly across different regions and well types, exhibiting a wide distribution from low to high, posing challenges to safety and economic efficiency. Seal failure can also result in substantial economic costs and even significant economic losses.

[0003] Existing oil casing thread sealing technologies mainly include API modified thread grease, polytetrafluoroethylene sealant, and special thread metal sealing structures, but each has its shortcomings.

[0004] Most API-modified threadlockers are based on petroleum-based or synthetic oils, with a large amount of heavy metal fillers such as lead, zinc, or copper powder (40-60% by mass) and non-metallic lubricating fillers such as graphite added to fill the thread gaps. Auxiliary sealing is achieved through mechanical compression. The sealing principle mainly relies on the filler filling the thread gaps, and the tightening of the threads forces the solid metal fillers in the threadlocker into the gaps to achieve an auxiliary sealing function. However, in high-temperature environments (>150℃), the base grease is prone to volatilization or degradation, leading to seal failure. In high-pressure gas wells, this auxiliary sealing method also lacks gas-tightness. The lead content also poses a risk of environmental pollution.

[0005] Polytetrafluoroethylene (PTFE) sealants are widely used for thread sealing due to their chemical inertness and low coefficient of friction. Common forms include PTFE tapes and emulsions. The seal relies on PTFE's low friction and chemical stability to form a thin film, and airtightness is achieved by tightening. While this technology offers the advantage of a low coefficient of friction, it still lacks high-temperature sealing performance. Furthermore, PTFE lacks dynamic adaptability and cannot cope with downhole vibrations or pressure fluctuations. After repeated disassembly and reassembly, the PTFE coating is prone to wear, leading to seal failure.

[0006] Special threaded metal sealing structures achieve an elastic interference fit between metals through precision-machined thread geometry, typically aided by a small amount of API grease or PTFE sealant. Typical products include special threads such as VAM 21, which rely on thread geometry and high contact stress to achieve sealing performance. They generally require a high engagement torque value, which can reach over 10,000 Nm. The limitations of this technology include high manufacturing costs, incompatibility between thread types from different manufacturers, cumbersome field operation requirements, and inability to fully meet the demands of long-term dynamic downhole environmental changes. After a certain period of operation, various oil and gas fields or gas storage facilities will experience some degree of annular pressure issues.

[0007] Magnetorheologically modified (MRM) materials achieve reversible changes in viscosity or yield stress by forming chain-like structures from magnetic particles under the influence of a magnetic field. They have been applied in the automotive, industrial, and aerospace fields, but have not yet been used for sealing oil casing threads. Their main working principle is that the MR fluid consists of a base liquid (such as silicone oil or polyether), carbonyl iron particles, and additives (such as surfactants and thickeners). Under the influence of a magnetic field, the viscosity can increase from 100 Pa·s to 10000 Pa·s. Typical applications include automotive suspension dampers and industrial brakes. However, existing MR fluids are liquids, primarily designed for dynamic damping or transmission, without considering thread gap filling or long-term gas-tight sealing requirements. This makes it difficult to meet the high pressure (>100 MPa) and corrosion resistance requirements of oil casings; particle settling or leakage is prone to occur at high temperatures or during long-term static conditions, making them unsuitable for high-airtightness scenarios. Furthermore, the formulation is not optimized for resistance to H2S / CO2 corrosion or thread surface lubrication.

[0008] To address the sealing challenges of oil casing threaded connections under high temperature (>200℃), high pressure (>100MPa), and highly corrosive environments (such as H2S and CO2 concentrations >5%), and to overcome the shortcomings of traditional sealants (such as API grease) such as high-temperature flow failure, insufficient pressure resistance, poor corrosion resistance, high extrusion rate, and poor environmental performance, it is necessary to provide a magnetron rheological material that can maintain sealing integrity under high temperature and high pressure, suitable for oil casing threaded connections in deep wells, high-pressure gas fields, and offshore oil fields. Summary of the Invention

[0009] To address the aforementioned issues, this application provides a magnetron rheological sealing material for oil casing threads, comprising, by weight: 50-60 wt% fluorosilicone gel, 30-40 wt% magnetron particles, 1-3 wt% fumed silica, 3-7 wt% zinc phosphate, and 3-7 wt% polytetrafluoroethylene micropowder, with the sum of all components being 100 wt%.

[0010] Furthermore, the magnetron particles are at least one of carbonyl iron particles, iron tetroxide nanoparticles, neodymium iron boron microparticles, and iron-cobalt alloy particles.

[0011] Furthermore, the magnetron-controlled particles are carbonyl iron particles.

[0012] Furthermore, the carbonyl iron particles have a particle size of 3-8µm and a magnetic saturation >1.8T.

[0013] Furthermore, the carbonyl iron particles have a fluorinated silane coating on their surface.

[0014] Furthermore, the particle size of fumed silica is 10-20 nm, and the surface area is >200 m². 2 / g.

[0015] Furthermore, the particle size of zinc phosphate is 1-3µm.

[0016] Furthermore, the solid filler comprises 0.5-2 wt% graphene nanosheets with a thickness of 0.5-10 nm and a modulus >1 GPa.

[0017] Furthermore, the particle size of polytetrafluoroethylene micro powder is 0.5-5 μm.

[0018] This application also discloses a method for preparing the above-mentioned magnetron rheological sealing material, comprising:

[0019] According to the preset ratio, fluorosilicone gel, polytetrafluoroethylene micro powder, graphene nanosheets and zinc phosphate are mixed and vacuum stirred to form a uniform matrix;

[0020] Magnetized particles were added to the matrix and stirred a second time;

[0021] Add fumed silica to the matrix and stir for the third time;

[0022] The matrix after the third stirring was subjected to vacuum degassing to obtain a magnetron rheological sealing material.

[0023] Furthermore, the vacuum degree of the vacuum stirring is 0.01-0.02MPa, the temperature is 50-60℃, the speed is 500-800rpm, and the stirring time is 1.5-2 hours.

[0024] Furthermore, the second stirring is carried out at a temperature of 50-60℃, a speed of 200-400 rpm, and a time of 1-1.5 hours.

[0025] Furthermore, the third stirring is carried out at a temperature of 50-60℃, a speed of 200-400 rpm, and a time of 20-40 minutes.

[0026] Furthermore, the vacuum degree of vacuum degassing is 0.01-0.02 MPa, the temperature is 20-25℃, and the degassing time is 20-40 minutes.

[0027] The technical effects and advantages of this application are as follows:

[0028] 1. The magnetorheological sealing material of this application can achieve adaptive sealing during the fastening process through magnetic field control, dynamically filling the thread gap. Combined with polymer matrix, mechanical locking and solid filler, it ensures excellent air tightness, corrosion resistance and long-term durability, solving the problems of poor air tightness, insufficient pressure resistance, high extrusion rate, poor corrosion resistance and poor environmental performance of traditional sealants in high temperature, high pressure and strong corrosion environment.

[0029] 2. The magnetorheological sealing material of this application can achieve adaptive dynamic sealing through the magnetorheological effect and reasonable magnetization control, which significantly improves sealing performance, durability and environmental adaptability.

[0030] 3. The magnetron rheological sealing material of this application uses fluorosilicone gel as a matrix to provide initial fluidity, ensure thread gap filling and chemical stability, maintain the seal after the magnetic field is removed, the cross-linked network of fluorosilicone gel restricts particle movement, and the fluorinated side chains reduce surface energy and enhance corrosion resistance.

[0031] 4. This application preferably uses carbonyl iron particles as magnetron particles, whose surface has a fluorinated silane coating. Under a magnetic field of 0.2-0.4T, they form a chain-like structure with a response time of <0.1 seconds, a viscosity increase to 15000-20000 Pa·s, and a yield stress >10 kPa. They dynamically fill thread gaps and compensate for surface defects. Specific values ​​can be adjusted due to differences in thread type, material grade, surface condition, temperature, pressure, and magnetization structure.

[0032] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures pointed out in the description and claims. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0034] To address the sealing challenges of threaded connections in oil casing pipes under high temperature, high pressure, and highly corrosive environments, and to overcome the limitations of traditional sealants such as high-temperature flow failure and insufficient pressure resistance, this product, by weight, comprises: 50-60wt% fluorosilicone gel, 30-40wt% magnetron sputtering granules, and the balance being solid filler. Examples include 50wt%, 52wt%, 54wt%, 56wt%, 58wt%, or 60wt% fluorosilicone gel, 30wt%, 32wt%, 34wt%, 36wt%, 38wt%, or 40wt% magnetron sputtering granules, and the balance being solid filler.

[0035] Compared to traditional magnetron rheodynamic fluids that use liquids such as silicone oil or polyether as the matrix, this application selects fluorosilicone gel as the matrix. The gel contains fluorosiloxane polymers with a molecular weight of 10⁵-10⁶ g / mol and a crosslinking degree >10³ mol / m. 3 It has a temperature resistance of -40-250℃, is resistant to H2S and CO2, and has an initial viscosity of 40-60 Pa·s. It can provide initial flowability for magnetron rheological sealing materials, ensuring thread gap filling and chemical stability, and providing long-term viscoelasticity and sealing performance. The cross-linked network of the fluorosilicone gel can restrict particle movement, and the fluorinated side chains reduce surface energy and enhance corrosion resistance. The proposed solution can use commercially available fluorosilicone gels, such as those produced and sold by companies like Zhejiang Huanxin Fluorine Materials Co., Ltd. and Wacker Chemie (China) Co., Ltd.

[0036] In some embodiments of this application, the magnetron sputtering particles are at least one of carbonyl iron particles, iron(III) oxide nanoparticles, neodymium iron boron micropowder, and iron-cobalt alloy particles. Preferably, the magnetron sputtering particles are carbonyl iron particles with a particle size of 3-8 µm, magnetic saturation >1.8T, purity >99.5%, and a fluorinated silane coating on the surface of the carbonyl iron particles with a coating thickness of 8-12 nm. Under a magnetic field of 0.2-0.4T, the magnetic dipole interaction drives the carbonyl iron particles to align, forming a chain structure within 0.1 seconds, increasing the viscosity to 15000-20000 Pa·s, and enhancing shear resistance. The carbonyl iron particles achieve adaptive filling during thread tightening through the magnetic field, filling all gaps and dangerous defects during and after thread tightening, significantly improving the initial sealing quality. After the chain structure of the carbonyl iron particles disintegrates, the matrix, mechanical locking, and filler work together to maintain a long-term seal. The proposed solution may use commercially available carbonyl iron particles, such as those produced and sold by Jiangxi Yuean New Materials Co., Ltd.

[0037] In some embodiments of this application, the solid filler comprises 1-3 wt% fumed silica by total mass, such as 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, or 3 wt% fumed silica, wherein the particle size of the fumed silica is 10-20 nm and the surface area is >200 m². 2 / g, purity >99.9%. By adding fumed silica to the magnetron rheological sealing material, a nano-thickening network can be formed, maintaining the viscosity of the magnetron rheological sealing material in the absence of a magnetic field, preventing stratification, and achieving a sedimentation rate of <1% per year.

[0038] In some embodiments of this application, the solid filler further includes 3-7 wt% zinc phosphate, such as 3 wt%, 4 wt%, 5 wt%, 6 wt%, or 7 wt% zinc phosphate, with a particle size of 1-3 µm and a purity >99%. The chemisorption of zinc phosphate can form a stable protective film, inhibiting H2S / CO2 corrosion.

[0039] In some embodiments of this application, the solid filler further includes 0.5-2 wt% graphene nanosheets by total mass, such as 0.5 wt%, 0.8 wt%, 1.1 wt%, 1.4 wt%, 1.7 wt%, or 2 wt% graphene nanosheets. The thickness of the graphene nanosheets is 0.5-10 nm, and the number of layers in the layered structure of the graphene nanosheets is 5, 6, 7, 8, 9, or 10, with a modulus >1 GPa and a purity >98%. The layered structure of the graphene nanosheets can disperse shear stress. Adding an appropriate amount of graphene nanosheets can enhance the wear resistance and mechanical strength of the magnetron rheological sealing material, and extend the sealing life under high vibration environments.

[0040] In some embodiments of this application, the solid filler comprises 3-7 wt% polytetrafluoroethylene (PTFE) micro powder, such as 3 wt%, 4 wt%, 5 wt%, 6 wt%, or 7 wt% PTFE micro powder, with a particle size of 0.5-5 μm and a purity of >99%. The surface energy of the PTFE micro powder is <20 mN / m, which can reduce the friction of the threaded connection, control the torque increase, protect the threads, and support multiple disassembly and assembly (>5 times).

[0041] To ensure industrial feasibility, this application also discloses a method for preparing the above-mentioned magnetron rheological sealing material, comprising:

[0042] Matrix mixing:

[0043] According to the preset ratio, add fluorosilicone gel, PTFE micro powder, graphene nanosheets and zinc phosphate into a vacuum mixer, control the vacuum degree to 0.01-0.02MPa, the temperature to 50-60℃, the speed to 500-800rpm, and the stirring time to 1.5-2 hours to form a uniform matrix.

[0044] Add magnetron particles:

[0045] Add magnetron particles to the matrix and stir a second time. Taking carbonyl iron particles as an example, control the temperature of the second stirring at 50-60℃, the speed at 200-400rpm, and the time at 1-1.5 hours to ensure uniform dispersion and protect the fluorinated silane coating of the carbonyl iron particles.

[0046] Add thickener:

[0047] Add fumed silica to the matrix and stir for the third time. The temperature of the third stirring is 50-60℃, the speed is 200-400rpm, and the time is 20-40 minutes. When the stirring is finished, the viscosity of the matrix is ​​stable at 50-60Pa·s.

[0048] Vacuum degassing:

[0049] The matrix after the third stirring was subjected to vacuum degassing at a vacuum level of 0.01-0.02 MPa, a temperature of 20-25℃, and a degassing time of 20-40 minutes. The bubble rate of the matrix after degassing was <0.1 vol%, yielding the magnetron rheological sealing material. The magnetron rheological sealing material was then sealed and stored in an environment with a humidity of <50%.

[0050] The magnetic control devices corresponding to the magnetic rheological sealing materials of this application include:

[0051] Electromagnetic coil: 0.8-1.2mm high-temperature resistant enameled wire, 800-1500 turns; with a soft magnetic core and closed magnetic circuit structure, the coil inner diameter is 120-200 mm; when supplied with an 8-12 A pulse current (12-24 V DC power supply, 50-150 W), it can generate an effective magnetic field of 0.2-0.4 T in the threaded area (based on actual measurement by a Hall sensor), and can be integrated into a hydraulic clamp. The effective magnetic flux density at the threaded meshing surface can reach the set value (0.2-0.4 T). It is powered by a lithium battery or well site power supply at 12-24V DC, with a power of 50-100W. The electromagnetic coil has a built-in switching circuit, generating pulses through rapid switching current. It can be manually switched or programmed for automatic switching, switching in stages according to the number of turns.

[0052] Microprocessor: Controls the switching circuit to open and close based on torque and / or angle sensor signals, with sensor accuracy ±0.1%.

[0053] Control panel: Located on the hydraulic clamp, used to set the pulse duration and interval to ensure precise magnetization.

[0054] Pulse triggering logic: When the thread engagement is 30%, 50%, and 90%, 0.2T, 0.3T, and 0.4T pulses are activated respectively, each lasting 0.5 seconds.

[0055] Pulse implementation method: The power supply module converts DC power into 1-5A pulse current, which drives the electromagnetic coil to generate a pulse magnetic field.

[0056] To achieve optimal sealing performance, this application modulates the properties of the magnetorheological sealing material through batch magnetization during the initial sealing phase. After the magnetic field is removed, the chain structure of the magnetorheological sealing material partially disintegrates due to Brownian and thermal motion, and the viscosity drops back to 50-100 Pa·s. The nano-network of fluorosilicone gel and fumed silica confines the particles to complete randomization, maintaining a viscous paste-like consistency. The threaded mechanical constraint locking material, combined with PTFE micropowder, graphene nanosheets, and zinc phosphate, ensures long-term airtightness.

[0057] If initial magnetization is not possible, a single 0.4-0.6T pulse can be applied after the top is closed, lasting 0.5-1 seconds, to increase the viscosity of the magnetron rheological sealing material to 5000-10000 Pa·s.

[0058] The working principle of the magnetron rheological sealing material in this application is as follows:

[0059] During the upper-coiling stage, magnetorheological effects are used to induce carbonyl iron particles to form a chain structure under a magnetic field of 0.2-0.4T, increasing the viscosity from 50 Pa·s to 15000-20000 Pa·s, with a yield stress >10 kPa. This dynamically fills all gaps in the thread, compensates for surface defects, and achieves a filling rate >95 vol%. Viscosity control is optimized through batch pulses, and the use of PTFE micropowder and graphene nanosheets ensures a friction coefficient <0.1 and a torque increase <6%.

[0060] After the magnetic field is removed, the viscosity of the fluorosilicone gel is 50-100 Pa·s. The fluorosilicone gel provides viscoelasticity, and when combined with threaded mechanical fastening materials, the gap is <0.01 mm, and the thread stress is >500 MPa, maintaining airtightness. Solid filler fumed silica prevents delamination, PTFE micropowder and graphene nanosheets enhance wear resistance, and zinc phosphate forms an anti-corrosion film. The fluorosilicone gel matrix, mechanical locking, and solid filler work together to maintain a long-term seal.

[0061] To better explain this solution, the following embodiments are provided.

[0062] Example 1

[0063] This embodiment uses API stepped thread (outer diameter 139.7mm, wall thickness 10.54mm) as the application object, which is suitable for deep well environment and achieves airtight sealing effect.

[0064] In this embodiment, the following components are precisely formulated to form a magnetron rheological sealing material.

[0065] 56wt% fluorosilicone gel, containing fluorosiloxane polymer, molecular weight 5×10 5g / mol, degree of crosslinking 1200 mol / m 3 Viscosity 50 Pa·s, shear rate 1 s at 25℃ -1 Temperature resistant from -40℃ to 250℃, resistant to H2S / CO2 corrosion. Source: Zhejiang Huanxin Fluorine Materials Co., Ltd., Product Model: HX-FS-500.

[0066] 33wt% carbonyl iron particles, particle size 3-8µm, fluorinated silane coating thickness 10nm, magnetic saturation greater than 1.8T, purity 99.6%, yield stress >10kPa under 0.4T magnetic field. Source: Jiangxi Yuean New Material Co., Ltd., model YA-CIP-05.

[0067] 4wt% PTFE micro powder, particle size <5µm, coefficient of friction 0.08, purity 99.5%. Source: Shanghai Sanaifu New Material Technology Co., Ltd., model SF-PTFE-03.

[0068] 1wt% graphene nanosheets, thickness <10nm, 5-10 layers, modulus >1GPa, purity 98.5%. Source: Xiamen Kaina Graphene Technology Co., Ltd., model KN-GNP-08.

[0069] 4wt% zinc phosphate, particle size 1-3µm, purity 99.2%. Source: Hebei Runbu Biotechnology Co., Ltd., model RB-ZP-02.

[0070] 2wt% fumed silica, 15nm particle size, 220m² surface area 2 / g, purity 99.9%, sedimentation rate <1% / year. Source: Evonik Degussa (China), model Aerosil 200.

[0071] The preparation process was carried out in a standard industrial environment using a vacuum stirrer (model VSM-100, volume 50L, maximum vacuum degree 0.01MPa) to ensure material homogeneity and stability. The specific steps are as follows:

[0072] S1: Matrix Mixing

[0073] Fluorosilicone gel, PTFE micropowder, graphene nanosheets, and zinc phosphate were added to a vacuum mixer. The vacuum level was set to 0.015 MPa, the temperature to 55℃, and the rotation speed to 600 rpm, and the mixture was stirred for 1.8 hours. The resulting matrix was a uniform milky white paste, and the cross-linked network of the fluorosilicone gel and the solid filler were initially fused together.

[0074] S2: Add magnetron particles

[0075] Carbonyl iron particles were slowly added to the matrix at a rate of 0.5 kg / min, while maintaining a temperature of 55°C and a rotation speed of 300 rpm for 1.2 hours. The carbonyl iron particles were uniformly distributed in the matrix, and the fluorinated silane coating remained intact, ensuring magnetron sputtering performance.

[0076] S3: Add fumed silica

[0077] Fumed silica was added to the matrix, and the mixture was stirred for 30 minutes at 55°C and 300 rpm. After adding fumed silica, the viscosity of the matrix at 25°C increased to 52 Pa·s, and the anti-settling properties were enhanced.

[0078] S4: Vacuum degassing

[0079] Under a vacuum of 0.015 MPa, the temperature was lowered to 22°C, and the mixture was allowed to stand for 30 minutes to degas, reducing the matrix bubble rate to approximately 0.05 vol%. The resulting magnetron rheological sealing material was a uniform gray-black paste, which, when sealed and stored in a stainless steel container (humidity <50%), exhibited stability >12 months.

[0080] Taking the API trapezoidal thread top thread as an example, and combining a hydraulic clamp (model HYD-500, maximum torque 15000Nm) and an integrated magnetization system, this embodiment demonstrates the application and dynamic sealing process of the magnetron rheological sealing material prepared in this example:

[0081] The prepared magnetron rheological sealing material (viscosity 52 Pa·s) was uniformly coated onto the male thread surface using a nylon brush, with a thickness of 0.15 mm and a coating area of ​​approximately 0.02 m². 2 Fluorosilicone gel ensures fluidity, while PTFE micropowder reduces the coefficient of friction to 0.08, making it easy to apply.

[0082] The hydraulic clamp rotates the male thread at 5 rpm, with thread engagement taking 4 seconds, reducing the gap from 0.1 mm to <0.01 mm. The magnetization system (electromagnetic coil: 0.8 mm enameled copper wire, 250 turns, 150 mm inner diameter; power supply: 24V, 80W) triggers pulses in three stages:

[0083] First pulse: 30% engagement (1.5 revolutions, 0.05mm gap, 3200Nm torque), applying a 0.2T magnetic field (1A, 0.5 seconds). The carbonyl iron particles rapidly aggregate into chains, increasing viscosity to 5000Pa·s, promoting gap filling, with a filling rate of 95 vol%.

[0084] Second pulse: 60% engagement (3 turns, 0.03mm gap, 5200Nm torque), apply a 0.3T magnetic field (1.5A, 0.5 seconds), viscosity reaches 10000Pa·s, strengthen the sealing layer.

[0085] Third pulse: 90% engagement (4.5 turns, gap <0.01mm, torque 10500Nm), applied 0.4T magnetic field (2A, 0.5 seconds), peak viscosity 18000Pa·s, yield stress 12kPa, compaction seal, under ISO 13679 / API 5C5 standard conditions (23 ± 2 ℃, N2, 20 MPa), leakage rate <0.01 cm. 3 / s.

[0086] The microprocessor (model STM32, response time 0.08 seconds) monitors in real time through a torque sensor (accuracy ±0.1%) and an angle sensor (±0.1°), triggers a pulse, increases torque by 5.8%, achieves an extrusion rate of 4.5 vol%, and has an adhesion of 1.2 MPa. It does not slip off for 24 hours at a 90° tilt.

[0087] After the magnetic field was removed, the chain structure of the carbonyl iron particles partially disintegrated, and the viscosity dropped back to 80 Pa·s. The viscoelasticity (storage modulus 10⁻⁶) of the fluorosilicone gel... 4 (Pa) Like a tough colloid, combined with a nano-network of fumed silica, maintaining paste stability. Thread compressive stress (550MPa) is like an iron lock fixing the sealing layer, PTFE micro powder and graphene nanosheets reduce friction, and zinc phosphate forms a 1µm thick protective film, resistant to H2S / CO2 corrosion rate <0.01mm / year.

[0088] During disassembly, an alternating magnetic field (0.2T, 5Hz, 10 seconds) is applied, causing the viscosity of the magnetron rheological sealing material to drop to 40 Pa·s, facilitating separation. The magnetron rheological sealing material can be recoated and used more than 5 times with performance degradation of <5%.

[0089] Example 2

[0090] This embodiment uses API stepped thread (outer diameter 139.7mm, wall thickness 10.54mm) as the application object, which is suitable for deep well environment and achieves airtight sealing effect.

[0091] In this embodiment, the following components are precisely formulated to form a magnetron rheological sealing material with a total mass of 10 kg.

[0092] 52wt% fluorosilicone gel, containing fluorosiloxane polymer, molecular weight 5×10⁵ g / mol, degree of crosslinking 1200 mol / m 3 Viscosity 50 Pa·s, shear rate 1 s at 25℃ -1 Temperature resistant from -40℃ to 250℃, resistant to H2S / CO2 corrosion. Source: Zhejiang Huanxin Fluorine Materials Co., Ltd., Product Model: HX-FS-500.

[0093] 35wt% carbonyl iron particles, particle size 3-8µm, fluorinated silane coating thickness 10nm, magnetic saturation greater than 1.8T, purity 99.6%, yield stress >10kPa under 0.4T magnetic field. Source: Jiangxi Yuean New Material Co., Ltd., model YA-CIP-05.

[0094] 5wt% PTFE micro powder, particle size <5µm, coefficient of friction 0.08, purity 99.5%. Source: Shanghai Sanaifu New Material Technology Co., Ltd., model SF-PTFE-03.

[0095] 1wt% graphene nanosheets, thickness <10nm, 5-10 layers, modulus >1GPa, purity 98.5%. Source: Xiamen Kaina Graphene Technology Co., Ltd., model KN-GNP-08.

[0096] 5wt% zinc phosphate, particle size 1-3µm, purity 99.2%. Source: Hebei Runbu Biotechnology Co., Ltd., model RB-ZP-02.

[0097] 2wt% fumed silica, 15nm particle size, 220m² surface area 2 / g, purity 99.9%, sedimentation rate <1% / year. Source: Evonik Degussa (China), model Aerosil 200.

[0098] The preparation process was carried out in a standard industrial environment using a vacuum stirrer (model VSM-100, volume 50L, maximum vacuum degree 0.01MPa) to ensure material homogeneity and stability. The specific steps are as follows:

[0099] S1: Matrix Mixing

[0100] Fluorosilicone gel, PTFE micropowder, graphene nanosheets, and zinc phosphate were added to a vacuum mixer. The vacuum level was set to 0.01 MPa, the temperature to 50°C, and the rotation speed to 500 rpm, and the mixture was stirred for 1.5 hours. The resulting matrix was a uniform milky white paste, and the cross-linked network of the fluorosilicone gel and the solid filler were initially fused together.

[0101] S2: Add magnetron particles

[0102] Carbonyl iron particles were slowly added to the matrix at a rate of 0.5 kg / min, while maintaining a temperature of 50°C and a rotation speed of 200 rpm for 1 hour. The carbonyl iron particles were uniformly distributed in the matrix, and the fluorinated silane coating remained intact, ensuring magnetron sputtering performance.

[0103] S3: Add fumed silica

[0104] Fumed silica was added to the matrix, and the mixture was stirred for 20 minutes at 50°C and 200 rpm. After adding fumed silica, the viscosity of the matrix at 25°C increased to 52 Pa·s, and the anti-settling properties were enhanced.

[0105] S4: Vacuum degassing

[0106] Under a vacuum of 0.01 MPa, the temperature was lowered to 20°C, and the mixture was allowed to stand for 20 minutes to degas, resulting in a matrix bubble rate of 0.05 vol%. The final magnetron rheological sealing material was a uniform gray-black paste, which, when sealed and stored in a stainless steel container (humidity <50%), exhibited a stability of >12 months.

[0107] Taking the API trapezoidal thread top thread as an example, and combining a hydraulic clamp (model HYD-500, maximum torque 15000Nm) and an integrated magnetization system, this embodiment demonstrates the application and dynamic sealing process of the magnetron rheological sealing material prepared in this example:

[0108] The prepared magnetron rheological sealing material (viscosity 52 Pa·s) was uniformly coated onto the male thread surface using a nylon brush, with a thickness of 0.15 mm and a coating area of ​​approximately 0.02 m². 2 Fluorosilicone gel ensures fluidity, while PTFE micropowder reduces the coefficient of friction to 0.08, making it easy to apply.

[0109] The hydraulic clamp rotates the male thread at 5 rpm, with thread engagement taking 4 seconds, reducing the gap from 0.1 mm to <0.01 mm. The magnetization system (electromagnetic coil: 0.8 mm enameled copper wire, 250 turns, 150 mm inner diameter; power supply: 24V, 80W) triggers pulses in three stages:

[0110] First pulse: 30% engagement (1.5 revolutions, 0.05mm gap, 3200Nm torque), applying a 0.2T magnetic field (1A, 0.5 seconds). The carbonyl iron particles rapidly aggregate into chains, increasing viscosity to 5000Pa·s, promoting gap filling, with a filling rate of 95 vol%.

[0111] Second pulse: 60% engagement (3 turns, 0.03mm gap, 5200Nm torque), apply a 0.3T magnetic field (1.5A, 0.5 seconds), viscosity reaches 10000Pa·s, strengthen the sealing layer.

[0112] Third pulse: 90% engagement (4.5 turns, gap <0.01mm, torque 10500Nm), applied 0.4T magnetic field (2A, 0.5 seconds), peak viscosity 18000Pa·s, yield stress 12kPa, compaction seal, under ISO 13679 / API 5C5 standard conditions (23 ± 2 ℃, N2, 20 MPa), leakage rate <0.01 cm. 3 / s.

[0113] The microprocessor (model STM32, response time 0.08 seconds) monitors in real time through a torque sensor (accuracy ±0.1%) and an angle sensor (±0.1°), triggers a pulse, increases torque by 5.8%, achieves an extrusion rate of 4.5 vol%, and has an adhesion of 1.2 MPa. It does not slip off for 24 hours at a 90° tilt.

[0114] After the magnetic field was removed, the chain structure of the carbonyl iron particles partially disintegrated, and the viscosity dropped back to 80 Pa·s. The viscoelasticity (storage modulus 10⁻⁶) of the fluorosilicone gel... 4 (Pa) Like a tough colloid, combined with a nano-network of fumed silica, maintaining paste stability. Thread compressive stress (550MPa) is like an iron lock fixing the sealing layer, PTFE micro powder and graphene nanosheets reduce friction, and zinc phosphate forms a 1µm thick protective film, resistant to H2S / CO2 corrosion rate <0.01mm / year.

[0115] During disassembly, an alternating magnetic field (0.2T, 5Hz, 10 seconds) is applied, causing the viscosity of the magnetron rheological sealing material to drop to 40 Pa·s, facilitating separation. The magnetron rheological sealing material can be recoated and used more than 5 times with performance degradation of <5%.

[0116] Example 3

[0117] This embodiment uses API stepped thread (outer diameter 139.7mm, wall thickness 10.54mm) as the application object, which is suitable for deep well environment and achieves airtight sealing effect.

[0118] In this embodiment, the following components are precisely formulated to form a magnetron rheological sealing material.

[0119] 52wt% fluorosilicone gel, containing fluorosiloxane polymer, molecular weight 5×10⁵ g / mol, degree of crosslinking 1200 mol / m 3 Viscosity 50 Pa·s, shear rate 1 s at 25℃ -1 Temperature resistant from -40℃ to 250℃, resistant to H2S / CO2 corrosion. Source: Zhejiang Huanxin Fluorine Materials Co., Ltd., Product Model: HX-FS-500.

[0120] 37wt% carbonyl iron particles, particle size 3-8µm, fluorinated silane coating thickness 10nm, magnetic saturation greater than 1.8T, purity 99.6%, yield stress >10kPa under 0.4T magnetic field. Source: Jiangxi Yuean New Material Co., Ltd., model YA-CIP-05.

[0121] 3wt% PTFE micro powder, particle size <5µm, coefficient of friction 0.08, purity 99.5%. Source: Shanghai Sanaifu New Material Technology Co., Ltd., model SF-PTFE-03.

[0122] 1wt% graphene nanosheets, thickness <10nm, 5-10 layers, modulus >1GPa, purity 98.5%. Source: Xiamen Kaina Graphene Technology Co., Ltd., model KN-GNP-08.

[0123] 5wt% zinc phosphate, particle size 1-3µm, purity 99.2%. Source: Hebei Runbu Biotechnology Co., Ltd., model RB-ZP-02.

[0124] 2wt% fumed silica, 15nm particle size, 220m² surface area 2 / g, purity 99.9%, sedimentation rate <1% / year. Source: Evonik Degussa (China), model Aerosil 200.

[0125] The preparation process was carried out in a standard industrial environment using a vacuum stirrer (model VSM-100, volume 50L, maximum vacuum degree 0.01MPa) to ensure material homogeneity and stability. The specific steps are as follows:

[0126] S1: Matrix Mixing

[0127] Fluorosilicone gel, PTFE micropowder, graphene nanosheets, and zinc phosphate were added to a vacuum mixer. The vacuum level was set to 0.02 MPa, the temperature to 60℃, and the rotation speed to 800 rpm for 2 hours. The resulting matrix was a uniform milky white paste, and the cross-linked network of the fluorosilicone gel and the solid filler were initially fused.

[0128] S2: Add magnetron particles

[0129] Carbonyl iron particles were slowly added to the matrix at a rate of 0.5 kg / min, while maintaining a temperature of 60°C and a rotation speed of 400 rpm for 1.5 hours. The carbonyl iron particles were uniformly distributed in the matrix, and the fluorinated silane coating remained intact, ensuring magnetron sputtering performance.

[0130] S3: Add fumed silica

[0131] Fumed silica was added to the matrix, and the mixture was stirred for 40 minutes at 60°C and 400 rpm. After adding fumed silica, the viscosity of the matrix at 25°C increased to 52 Pa·s, and the anti-settling properties were enhanced.

[0132] S4: Vacuum degassing

[0133] Under a vacuum of 0.02 MPa, the temperature was lowered to 25°C, and the mixture was allowed to stand for 40 minutes to degas, reducing the matrix bubble rate to 0.05 vol%. The resulting magnetron rheological sealing material was a uniform gray-black paste, which, when sealed and stored in a stainless steel container (humidity <50%), exhibited stability >12 months.

[0134] Taking the API trapezoidal thread top thread as an example, and combining a hydraulic clamp (model HYD-500, maximum torque 15000Nm) and an integrated magnetization system, this embodiment demonstrates the application and dynamic sealing process of the magnetron rheological sealing material prepared in this example:

[0135] The prepared magnetron rheological sealing material (viscosity 52 Pa·s) was uniformly coated onto the male thread surface using a nylon brush, with a thickness of 0.15 mm and a coating area of ​​approximately 0.02 m². 2 Fluorosilicone gel ensures fluidity, while PTFE micropowder reduces the coefficient of friction to 0.08, making it easy to apply.

[0136] The hydraulic clamp rotates the male thread at 5 rpm, with thread engagement taking 4 seconds, reducing the gap from 0.1 mm to <0.01 mm. The magnetization system (electromagnetic coil: 0.8 mm enameled copper wire, 250 turns, 150 mm inner diameter; power supply: 24V, 80W) triggers pulses in three stages:

[0137] First pulse: 30% engagement (1.5 revolutions, 0.05mm gap, 3200Nm torque), applying a 0.2T magnetic field (1A, 0.5 seconds). The carbonyl iron particles rapidly aggregate into chains, increasing viscosity to 5000Pa·s, promoting gap filling, with a filling rate of 95 vol%.

[0138] Second pulse: 60% engagement (3 turns, 0.03mm gap, 5200Nm torque), apply a 0.3T magnetic field (1.5A, 0.5 seconds), viscosity reaches 10000Pa·s, strengthen the sealing layer.

[0139] Third pulse: 90% engagement (4.5 turns, gap <0.01mm, torque 10500Nm), applied 0.4T magnetic field (2A, 0.5 seconds), peak viscosity 18000Pa·s, yield stress 12kPa, compaction seal, under ISO 13679 / API 5C5 standard conditions (23 ± 2 ℃, N2, 20 MPa), leakage rate <0.01 cm. 3 / s.

[0140] The microprocessor (model STM32, response time 0.08 seconds) monitors in real time through a torque sensor (accuracy ±0.1%) and an angle sensor (±0.1°), triggers a pulse, increases torque by 5.8%, achieves an extrusion rate of 4.5 vol%, and has an adhesion of 1.2 MPa. It does not slip off for 24 hours at a 90° tilt.

[0141] After the magnetic field was removed, the chain structure of the carbonyl iron particles partially disintegrated, and the viscosity dropped back to 80 Pa·s. The viscoelasticity (storage modulus 10⁻⁶) of the fluorosilicone gel... 4(Pa) Like a tough colloid, combined with a nano-network of fumed silica, maintaining paste stability. Thread compressive stress (550MPa) is like an iron lock fixing the sealing layer, PTFE micro powder and graphene nanosheets reduce friction, and zinc phosphate forms a 1µm thick protective film, resistant to H2S / CO2 corrosion rate <0.01mm / year.

[0142] During disassembly, an alternating magnetic field (0.2T, 5Hz, 10 seconds) is applied, causing the viscosity of the magnetron rheological sealing material to drop to 40 Pa·s, facilitating separation. The magnetron rheological sealing material can be recoated and used more than 5 times with performance degradation of <5%.

[0143] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A magnetron rheological sealing material for oil casing threads, characterized in that, Its components, by mass, include: 50-60 wt% fluorosilicone gel, 30-40 wt% magnetron particles, 1-3 wt% fumed silica, 3-7 wt% zinc phosphate, 0.5-2 wt% graphene nanosheets, and 3-7 wt% polytetrafluoroethylene micro powder, with the sum of all components being 100 wt%.

2. The magnetron rheological sealing material for oil casing threads according to claim 1, characterized in that, The magnetron particles are at least one of carbonyl iron particles, iron tetroxide nanoparticles, neodymium iron boron microparticles, and iron-cobalt alloy particles.

3. The magnetron rheological sealing material for oil casing threads according to claim 1, characterized in that, The magnetron particles are carbonyl iron particles.

4. The magnetron rheological sealing material for oil casing threads according to claim 3, characterized in that, The carbonyl iron particles have a particle size of 3-8µm and a magnetic saturation of >1.8T.

5. The magnetron rheological sealing material for oil casing threads according to claim 3, characterized in that, The surface of the carbonyl iron particles has a fluorinated silane coating.

6. The magnetron rheological sealing material for oil casing threads according to claim 1, characterized in that, The fumed silica has a particle size of 10-20 nm and a surface area >200 m². 2 / g.

7. The magnetron rheological sealing material for oil casing threads according to claim 1, characterized in that, The zinc phosphate has a particle size of 1-3µm.

8. The magnetron rheological sealing material for oil casing threads according to claim 1, characterized in that, The graphene nanosheets have a thickness of 0.5-10 nm and a modulus >1 GPa.

9. The magnetron rheological sealing material for oil casing threads according to claim 1, characterized in that, The particle size of polytetrafluoroethylene (PTFE) micro powder is 0.5-5 μm.

10. A method for preparing the magnetron rheological sealing material according to any one of claims 1-9, characterized in that, include: According to the preset ratio, fluorosilicone gel, polytetrafluoroethylene micro powder, graphene nanosheets and zinc phosphate are mixed and vacuum stirred to form a uniform matrix; Magnetized particles are added to the matrix and a second stirring is performed; Add fumed silica to the matrix and stir for a third time; The matrix after the third stirring was subjected to vacuum degassing to obtain a magnetron rheological sealing material.

11. The method according to claim 10, characterized in that, The vacuum stirring is performed at a vacuum level of 0.01-0.02 MPa, a temperature of 50-60℃, a speed of 500-800 rpm, and a stirring time of 1.5-2 hours.

12. The method according to claim 10, characterized in that, The second stirring is performed at a temperature of 50-60℃, a speed of 200-400 rpm, and a time of 1-1.5 hours.

13. The method according to claim 10, characterized in that, The third stirring is performed at a temperature of 50-60℃, a speed of 200-400 rpm, and a time of 20-40 minutes.

14. The method according to claim 10, characterized in that, The vacuum degassing process involves a vacuum level of 0.01-0.02 MPa, a temperature of 20-25°C, and a degassing time of 20-40 minutes.