Asphaltene deposition prevention system and method based on magnetofluid barrier and oil and gas transmission pipeline

Abstract

The invention discloses an asphaltene deposition prevention system based on a magnetic fluid barrier, and relates to the field of oil and gas exploitation and pipeline transportation, the asphaltene deposition prevention system comprises a pipeline body used for transporting asphaltene-containing crude oil, and the pipeline body is an oil pipeline, preferably a metal pipeline / non-metal pipeline with a smooth inner wall; the magnetic field generation module is used for generating a magnetic field gradient pointing to the center of the pipeline from the pipe wall in the inner wall area of the pipeline body; the magnetic fluid supply module is used for supplying magnetic fluid into the pipeline body, the pipe diameter of the pipeline body is selected according to actual requirements, and the magnetic field generation module adopts an annular array formed by neodymium iron boron permanent magnets and is fixed to the outer wall of the pipeline through an adjustable mechanical support. The magnetic fluid is driven by the magnetic field gradient to form a stable physical isolation layer on the inner wall of the pipeline, so that asphaltene is effectively prevented from being in contact with the pipe wall, and dependence on chemical agents and mechanical cleaning is reduced.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas extraction and transportation technology, and particularly relates to an anti-asphalt deposition system, method and oil and gas transportation pipeline based on a magnetohydrodynamic barrier. Background Technology

[0002] During oil extraction and pipeline transportation, asphaltenes in crude oil are prone to precipitate and deposit on the inner wall of pipelines when temperature and pressure change or when light components are added. This deposition can lead to reduced pipe diameter, increased flow resistance, and in severe cases, pipeline blockage, affecting normal production. Currently, mechanical cleaning (such as pipeline pigs) or chemical additives (such as dispersants) are mainly used to address this issue.

[0003] However, in certain specific application scenarios, traditional methods have obvious limitations: 1. Pipelines in special environments: In special environments such as deep-sea pipelines and polar pipelines, mechanical pipeline cleaning operations are difficult to implement, and the cost of routine maintenance increases significantly. The transportation, refueling and recovery of chemical agents in these environments also face many difficulties.

[0004] 2. Laboratory research apparatus: In experimental apparatus for studying the deposition mechanism of bitumen, mechanical cleaning can interfere with the experimental process, and the introduction of chemical additives may affect the accuracy of the experimental results.

[0005] In recent years, the development of magnetic nanomaterials technology has provided new ideas for flow assurance. Existing technologies include methods that directly add magnetorheological fluids as dispersants to crude oil for transportation, suppressing asphaltenes aggregation through the dispersing effect of magnetic nanoparticles. However, this method has the following problems: Magnetofluid is directly mixed into crude oil as an additive, which is difficult to fully recover, resulting in high operating costs. Nanoparticles may affect subsequent crude oil processing. The dispersion effect is greatly affected by the crude oil composition, and its adaptability to different oil fields is limited; It still falls under the category of chemical methods that act inside crude oil and cannot provide physical isolation protection.

[0006] Based on the above reasons, this invention designs an anti-asphalt deposition system, method, and oil and gas transportation pipeline based on a magnetohydrodynamic barrier. Summary of the Invention

[0007] The purpose of this invention is to provide a system, method and application for preventing asphalt deposition based on a magnetohydrodynamic barrier, which solves the problem of asphalt deposition in pipelines through proactive prevention.

[0008] To achieve the above objectives, the present invention adopts the following technical solution. A magnetohydrodynamic barrier-based system for preventing bituminous deposition includes: The pipeline body is used to transport crude oil containing bituminous substances; A magnetic field generating module is used to generate a magnetic field gradient from the pipe wall to the center of the pipe in the inner wall region of the pipe body. A magnetofluid supply module is used to supply magnetofluid into the pipe body; Driven by the magnetic field gradient, the magnetofluid forms a stable wetting film on the inner wall of the pipe, which physically isolates the asphalt from the pipe wall.

[0009] In the above system, the magnetic fluid supplied by the magnetic fluid supply module is prepared by the following method: S1: Preparation of iron ion precursor solution, wherein Fe 3+ with Fe 2+ The molar ratio is approximately 2:1; S2: Add an alkaline precipitant to the precursor solution and carry out a co-precipitation reaction under inert gas protection to generate Fe3O4 precursor; S3: The Fe3O4 precursor is subjected to hydrothermal annealing to obtain Fe3O4 nanoparticles; S4: The Fe3O4 nanoparticles are surface-modified using a silane coupling agent; S5: Surface-modified Fe3O4 nanoparticles and surfactants are co-dispersed in a mineral oil carrier and ultrasonically treated to form a stable magnetic fluid.

[0010] In the above system, the magnetic field generating module is a permanent magnet array arranged around the pipe, and the permanent magnet array is configured so that its corresponding magnetic poles face the pipe wall.

[0011] The system described above also includes a sensing and monitoring module, which comprises: Pressure sensors are installed at the inlet and outlet of the pipeline; Temperature sensors are installed at different axial positions on the pipeline; Multiple magnetic field strength sensors are arranged around the pipe; And an online microscopic imaging device for real-time observation of the liquid film state on the tube wall.

[0012] The system also includes a central control module, which is signal-connected to the sensing and monitoring module, the magnetic field generating module, and the magnetofluid supply module, and is configured as follows: Receive data from the sensor monitoring module; Based on the data, the magnetic field parameters of the magnetic field generating module and the flow rate of the magnetofluid supply module are dynamically adjusted to maintain the stability and integrity of the wetting film during crude oil flow.

[0013] In the above system, the magnetic fluid supply module includes a magnetic fluid storage tank, a feed pump, and a circulation loop, which is used to recover and re-inject the magnetic fluid flowing out of the pipeline to continuously renew the wetting fluid film.

[0014] A method for preventing asphalt deposits using the above system includes the following steps: Pre-filming step: The magnetic fluid is injected into the pipe through the magnetic fluid supply module to pre-form an initial liquid film on the inner wall of the pipe; Barrier establishment steps: Activate the magnetic field generating module, apply and maintain a preset magnetic field gradient, so that the initial liquid film is strengthened under the action of the magnetic field to form a stable anti-deposition barrier; Crude oil transportation steps: Crude oil containing asphalt is introduced into a pipeline with the aforementioned anti-deposition barrier, so that the crude oil flows inside the barrier and is prevented from directly contacting the pipe wall.

[0015] In the above method, during the crude oil transportation step, the magnetofluid is maintained to flow through a circulation loop to dynamically replenish and renew the liquid film on the pipe wall.

[0016] In the above method, the operating parameters are monitored in real time by a sensing and monitoring module, and the magnetic field parameters and magnetofluid flow rate are dynamically adjusted by a central control module to respond to changes in operating conditions and ensure that the anti-deposition barrier remains effective.

[0017] An oil and gas transmission pipeline includes a pipe manufactured using the aforementioned system. The pipe contains an impregnation film formed on the inner wall of the pipe by a magnetofluid driven by a magnetic field gradient applied to the inner wall of the pipe, serving as a physical barrier to isolate asphaltene from the pipe wall.

[0018] The advantages of this invention are: 1. By driving the magnetic fluid through a magnetic field gradient, a stable physical isolation layer is formed on the inner wall of the pipe, which effectively prevents the asphalt from contacting the pipe wall and reduces the reliance on chemical agents and mechanical cleaning.

[0019] 2. The system adopts a magnetohydrodynamic closed-loop circulation and permanent magnet excitation, which realizes the reuse of core components and operation without external power supply, reducing material consumption and energy consumption.

[0020] 3. The integrated sensing and monitoring module and central control module can automatically adjust the magnetic field parameters and magnetic fluid supply in real time according to changes in operating conditions, ensuring the long-term stability of the anti-deposition barrier under different operating conditions. Attached Figure Description

[0021] Figure 1 This is a flowchart of a particle collection and vapor deposition method based on Lorentz force disclosed in this invention.

[0022] Figure 2This is a schematic diagram of a particle collection and vapor deposition method based on Lorentz force disclosed in this invention.

[0023] Figure 3 This is a schematic diagram of a particle collection and vapor deposition device based on Lorentz force disclosed in this invention.

[0024] In the diagram: 1. Oil storage tank; 2. Magnetofluid storage tank; 3. Switch valve one; 4. Sensing and monitoring system; 5. Magnetic field generating module; 6. Central control module; 7. Switch valve two; 8. Switch valve three; 9. Switch valve four; 10. Switch valve five; 11. Flow meter one; 12. Flow meter two; 13. Water bath thermometer; 14. Thermometer one; 15. Pressure gauge one; 16. Thermometer two; 17. Camera; 18. Thermometer three; 19. Pressure gauge two; 20. Neodymium iron boron permanent magnet. Detailed Implementation

[0025] To facilitate understanding of this application and to make the aforementioned objectives, features, and advantages of this application more apparent, a detailed description of specific embodiments of this application is provided below in conjunction with the accompanying drawings. Numerous specific details are set forth in the following description to provide a thorough understanding of this application, and preferred embodiments are shown in the accompanying drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application. This application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application; therefore, this application is not limited to the specific embodiments disclosed below. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified. It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementations. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is only for describing particular implementations and is not intended to limit the scope of this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] Reference Figures 1-3 A magnetohydrodynamic barrier-based asphalt deposition prevention system, comprising: The pipeline body is used to transport crude oil containing bituminous substances, wherein the pipeline body is selected as a metal pipe / non-metal pipe with a smooth inner wall; Magnetic field generating module 5 is used to generate a magnetic field gradient from the pipe wall to the center of the pipe in the inner wall region of the pipe body. A magnetofluid supply module is used to supply magnetofluid into the pipe body.

[0027] The pipeline body is an oil pipeline, made of stainless steel with a smooth inner wall. The pipe diameter can be selected according to actual needs. The magnetic field generating module uses a ring array of neodymium iron boron permanent magnets, which is fixed to the outer wall of the pipeline by an adjustable mechanical support. The magnetofluid supply module includes a magnetofluid storage tank, a precision feed pump, and a circulation loop. The magnetofluid storage tank is equipped with a heating device and a stirrer to ensure uniform and stable magnetofluid flow.

[0028] The advantage of this embodiment is that it drives the magnetic fluid to form a stable wetting film on the pipe wall through the magnetic field gradient, thereby achieving active prevention of asphalt deposition. The system has a simple and reliable structure, does not require changes to the existing main structure of the pipeline, is easy to install and apply on site, and adopts the principle of physical isolation to avoid the use of chemical agents, thus achieving environmental friendliness. In one feasible embodiment, the magnetic fluid supplied by the magnetic fluid supply module is prepared by the following method: S1: Preparation of iron ion precursor solution, wherein Fe 3+ with Fe 2+ The molar ratio is approximately 2:1; S2: Add an alkaline precipitant to the precursor solution and carry out a co-precipitation reaction under inert gas protection to generate Fe3O4 precursor; S3: The Fe3O4 precursor is subjected to hydrothermal annealing to obtain Fe3O4 nanoparticles; S4: The Fe3O4 nanoparticles are surface-modified using a silane coupling agent; S5: Surface-modified Fe3O4 nanoparticles and surfactants are co-dispersed in a mineral oil carrier and ultrasonically treated to form a stable magnetic fluid.

[0029] The specific process is as follows: (1) Preparation of precursor solution This liquid is a mixed precursor solution mainly composed of Fe2+ and Fe3+ ions, providing raw materials for the subsequent synthesis of magnetic iron oxide nanoparticles. Specific preparation steps: Weigh 2.70 g of FeCl3·6H2O and 0.99 g of FeCl2·4H2O, and let Fe... 3+ with Fe 2+ The molar ratio is approximately 2:1. The two iron salts were dissolved in 50 mL of deionized water and stirred on a magnetic stirrer at approximately 400 rpm at room temperature for about 10 minutes until completely dissolved, resulting in a clear, yellow-brown solution, indicating that the iron ion precursor solution had been successfully prepared.

[0030] (2) Precipitation reaction Approximately 25 mL of 25% ammonia solution (NH3·H2O) was slowly added dropwise to the above iron salt precursor solution. The dropping rate was controlled to not exceed 1 mL / min to avoid violent exothermic reactions. As the ammonia solution was added, the pH of the solution gradually increased, and the solution color changed successively from yellowish-brown to brownish-red, eventually resulting in a black precipitate. The appearance of the black precipitate indicates that the Fe3O4 precursor has been formed.

[0031] Inert nitrogen gas is continuously introduced during the reaction to purge air and prevent Fe from being released. 2+ Oxidized into Fe 3+ This affects product quality. After precipitation, avoid direct contact with hands or prolonged exposure to air to reduce premature oxidation or aggregation of nanoparticles. Nitrogen protection is crucial to ensuring the purity of the Fe3O4 product, preventing oxygen oxidation of Fe. 2+ The rate at which ammonia is added must be strictly controlled; adding it too quickly can lead to localized overheating and uneven particle size. The resulting black Fe3O4 precipitate should be processed immediately while still fresh to avoid prolonged storage that could cause particle aging or oxidation.

[0032] (3) Hydrothermal crystallization treatment The main purpose of this step is to utilize hydrothermal synthesis conditions to transform the aforementioned amorphous or low-crystallinity Fe3O4 precursor into highly crystalline nano-Fe3O4 particles, thereby improving magnetism and stability. Specifically, the moist black Fe3O4 precipitate obtained in step (2) is rapidly transferred to the inner liner of a stainless steel high-pressure reactor (or microwave hydrothermal reactor) lined with polytetrafluoroethylene (PTFE). A small amount of deionized water and lauric acid are added to the inner liner as surfactants, with the amount being approximately 10% of the precipitate mass. After sealing the reactor, the reaction is heated in a microwave hydrothermal synthesis device at a temperature of 180°C for 30 minutes. The heating process is kept as uniform as possible (approximately 5°C / min) to avoid excessive temperature shocks. During the reaction, the water is heated and vaporized to generate high pressure, allowing the Fe3O4 nanocrystals to gradually grow and mature under high temperature and high pressure. After the reaction is complete, the heating is turned off, and the reactor is allowed to cool naturally to room temperature. After cooling, the reactor is opened to obtain a fully crystalline black Fe3O4 nanoparticle suspension. The hydrothermal reaction mechanism involves the formation and growth of Fe3O4 crystal nuclei at a high temperature of 180℃. High pressure inhibits excessive crystal growth, resulting in uniformly sized nanoparticles. Simultaneously, the added lauric acid molecules adsorb onto the particle surface, inhibiting particle aggregation and improving their dispersibility.

[0033] (4) Magnetic separation and cleaning The black suspension resulting from the hydrothermal reaction was poured into a beaker. A strong magnet was brought close to the outer wall of the beaker to adsorb and concentrate the magnetic Fe3O4 particles from the solution onto the magnet. After most of the particles had aggregated, the supernatant was carefully discarded. Approximately 100 mL of deionized water was then added to the beaker, the precipitate was stirred to suspend it, and the beaker was placed in an ultrasonic cleaning bath and sonicated for 10 minutes to disperse the particles and remove impurities. The particles were then concentrated again using magnetic separation, and the supernatant was discarded. This "ultrasonication-magnetic separation-discarding" cleaning process was repeated three times until the supernatant from the final wash was nearly colorless and transparent, indicating that soluble impurities had been largely removed. After the final magnetic separation, the moistened magnetic particles were collected in a container and dried to obtain pure Fe3O4 nanoparticles.

[0034] (5) Surface silanization modification 1.0 g of dried Fe3O4 nanoparticle powder was placed in a beaker and 50 mL of anhydrous ethanol was added to prepare a suspension. A silane coupling agent solution was prepared by adding 0.5 mL of 3-aminopropyltriethoxysilane (APTES) to the suspension. The mixture was ultrasonically dispersed for 30 minutes using an ultrasonic disperser to ensure uniform dispersion of the nanoparticles and adequate contact with the silane coupling agent. The mixture was then transferred to a round-bottom flask equipped with a reflux condenser and heated in a water bath at 80 °C for 4 hours under nitrogen protection. During the reaction, the ethoxy group (-OEt) on the APTES molecule hydrolyzed and condensed (esterified) with the hydroxyl group (-OH) on the surface of the Fe3O4 particles to form stable Si-O~Fe bonds, while simultaneously introducing -CH2CH2CH2NH2 groups onto the particle surface. After the reaction was complete, heating was stopped and the mixture was cooled to room temperature. The modified particles were recovered by magnetic separation and washed twice each with anhydrous ethanol and acetone to remove unreacted silane and byproducts. Finally, the product was dried under vacuum to obtain Fe3O4 nanoparticles with amine functional groups on the surface.

[0035] (6) Preparation of magnetic fluid dispersion Select a mineral oil with moderate viscosity and chemical inertness as the carrier liquid for the magnetic fluid. Weigh out the appropriate mass of surface-modified Fe3O4 nanoparticles according to the required magnetic fluid concentration (generally 1-2 wt.%, i.e., nanoparticles accounting for 1-2% of the total mass). Place a certain amount of mineral oil in a beaker, add oleic acid (surfactant) at approximately 10% of the nanoparticle mass, and stir until homogeneous. Then add the nanoparticle powder to the oleic acid-modified mineral oil. Treat the mixture using an ultrasonic dispersion device; a power of approximately 200W, a frequency of 20kHz, and a duration of 30 minutes are recommended. To avoid overheating of the liquid during ultrasonication, pause for 2 minutes every 10 minutes to allow for heat dissipation. After ultrasonic treatment, a uniform and stable black magnetic fluid can be observed to form, without any visible sedimentation or agglomeration.

[0036] (7) Magnetofluid quality assessment This step mainly involves a comprehensive characterization of the obtained magnetofluid, evaluating its quality in terms of particle size, magnetic properties, stability, and rheology to ensure that it meets the requirements for anti-asphalt deposition applications.

[0037] Particle size distribution detection: Take an appropriate amount of the prepared magnetic fluid, dilute it appropriately with the same carrier oil, and then use a laser particle size analyzer to determine its particle size distribution. It is expected that the average hydrated particle size of the nanoparticles in the magnetic fluid is in the range of 50~200nm, and the polydispersity index (PDI) < 0.3, which indicates a narrow particle size distribution, which is beneficial to the stability and repeatability of the magnetic fluid.

[0038] Magnetization measurement: Approximately 0.5 mL of the magnetic fluid sample was placed in the VSM sample chamber, and the magnetization curve was scanned and measured under an applied magnetic field. Special attention was paid to the saturation magnetization (Ms). In this embodiment, the Ms of the magnetic fluid was above approximately 50 emu / g, indicating the presence of a sufficient proportion of magnetic Fe3O4 to ensure a significant magnetic response under the influence of a magnetic field.

[0039] Long-term stability test: The magnetofluid sample was sealed and allowed to stand at room temperature for 7 days. Observe for any visible particle sedimentation or stratification. Simultaneously, the zeta potential was measured before and after standing, or a turbidimeter was used to assess stability. The goal is to have no significant precipitation after one week of standing, and for the zeta potential to remain above ±30mV, indicating strong colloidal stability of the system.

[0040] Rheological property determination: Using a rotational rheometer, at different shear rates (e.g., 0.01~1000 s⁻¹). -1 The viscosity of the magnetorheological fluid was measured under normal temperature and pressure to evaluate its rheological behavior. Ideally, the magnetorheological fluid of this invention exhibits Newtonian fluid characteristics at room temperature and pressure, meaning its viscosity remains essentially unchanged with shear rate. Within the detection range, the viscosity should be maintained between 100 and 500 cP (centipoise), comparable to the reference viscosity of the corresponding carrier oil, thereby ensuring that the magnetorheological fluid does not cause excessive additional resistance to flow when transported in pipelines.

[0041] In one feasible embodiment, the magnetic field generating module 5 is optimized. The permanent magnet array is arranged in a specific way so that the same magnetic poles (N poles) of all magnets face the center of the pipe wall. This configuration can generate a magnetic field with an intensity of 0.5~2.0T and a gradient of 50~200T / m inside the pipe. The direction of the magnetic field is strictly maintained from the pipe wall to the center of the pipe. This configuration of the same magnetic poles facing the pipe wall can generate a stronger magnetic field gradient, which significantly enhances the stability and adhesion of the magnetofluid film. The permanent magnets do not require external power supply, have low operating costs, and are particularly suitable for applications in remote areas and subsea pipelines. The permanent magnets are neodymium iron boron permanent magnets 20. This embodiment achieves continuous adjustment of the magnetic field strength through a mechanical adjustment device, adapting to different operating conditions; The ring array arrangement ensures a uniform distribution of the magnetic field around the pipeline, avoiding any blind spots in protection.

[0042] In one feasible embodiment, multiple sensors are arranged at key locations in the piping system: High-precision pressure sensors, including pressure gauge 15 and pressure gauge 29, with a range of 0~50MPa and an accuracy of ±0.1%, are installed at the pipe inlet and outlet; three thermometers, including thermometer 14, thermometer 26, and thermometer 38, are arranged along the pipe axis, with a measurement range of -20~200℃ and an accuracy of ±0.1℃; and eight Hall effect sensors are evenly arranged circumferentially. Figure 2 At point aj, the magnetic field strength distribution is monitored in real time; a camera 17 is installed in the observation section to observe the liquid film state in real time through a sapphire window.

[0043] The aforementioned technological advantages are reflected in the ability to comprehensively grasp the system's operating status through the collaborative monitoring of multiple parameters; Among these features, high-frequency data acquisition can be set up to detect abnormal fluctuations in a timely manner, and the complementary use of optical observation and electrical measurement can provide an intuitive assessment of the operating status. Meanwhile, the distributed sensor network provides sufficient data support for intelligent control.

[0044] In one feasible embodiment, this embodiment focuses on improving the system's control strategy. The central control module 6 adopts an industrial-grade PLC and is equipped with a control algorithm. During system operation, the controller collects data from various sensors in real time and dynamically adjusts the magnetofluid flow rate and magnetic field parameters based on the established liquid film stability model. When abnormal pressure fluctuations are detected, the system can respond within 100ms, automatically enhancing the magnetic field gradient or increasing the magnetofluid replenishment.

[0045] This embodiment establishes an intelligent decision-making mechanism based on multi-parameter fusion, adopts a feedforward-feedback composite control strategy, improves the system response speed, and has a self-learning function. It optimizes control parameters based on historical operating data and sets up multiple safety protection mechanisms to ensure reliable operation of the system under various working conditions.

[0046] In one feasible embodiment, the magnetofluid supply module is designed in detail. The system adopts a closed-loop circulation system and includes components such as a magnetofluid storage tank 2, a plunger-type metering pump, a filter, and a heat exchanger. The tank volume is designed according to the pipe size, and a nitrogen protection system is equipped to prevent oxidation of the magnetofluid. The circulation flow rate is precisely controlled according to the pipe diameter to ensure that the liquid film thickness is maintained within the range of 0.2~0.5mm.

[0047] The specific settings for various sensors include: Temperature sensor: A Pt100 platinum resistance thermometer is preferred, installed at the inlet, middle, and outlet of the pipeline to measure the temperature of the mixture of magnetic fluid and crude oil flowing through it. The sensor has an accuracy of ±0.1℃, a measurement range of -20℃ to 200℃, and a response time of <1s, ensuring the ability to capture temperature fluctuations. The temperature data is used to determine the operating status of the heating system and changes in the viscosity of the magnetic fluid, as temperature directly affects the magnetization and rheological properties of the magnetic fluid.

[0048] Pressure sensors: A high-precision pressure sensor (range 0–50 MPa, accuracy ±0.1 MPa) is installed at the inlet, outlet, and before and after the main magnetic field area of ​​the pipeline. These sensors monitor the pressure drop of the fluid flow and the absolute pressure inside the pipe. An abnormal increase in pressure at any point may indicate a ruptured wetting film leading to local blockage or increased flow resistance, serving as an early warning signal.

[0049] Magnetic field strength sensor: 4–8 Hall effect sensors are evenly arranged circumferentially around the pipe to measure the magnetic field strength in real time. The accuracy is ±0.05T, and the measurement frequency is DC–1kHz. By comparing the magnetic field readings at different locations, the uniformity of the magnetic field can be assessed, and problems such as magnet demagnetization or electromagnetic coil malfunctions can be detected promptly.

[0050] Flow meters: Install one non-insertion flow meter (e.g., ultrasonic or electromagnetic flow meter, accuracy ±1%) at both the inlet and outlet of the pipeline. These are used to monitor the actual flow rate of the crude oil / magnetic fluid mixture and compare it to the set value to ensure proper fluid supply and prevent leaks. If the outlet flow rate is significantly lower than the inlet flow rate, it may indicate the gradual formation of deposits or other blockages, requiring attention.

[0051] Online microscopic imaging system: A miniature high-resolution camera or optical sensor is installed in the monitoring section of the pipeline to observe the condition of the pipe wall through a transparent window. The resolution can reach several micrometers, enabling the capture of images of initial bitumen deposition or magnetohydrodynamic film defects. Once thinning of the film, damage, or the formation of deposition spots is detected, the system will issue an alarm to prompt manual intervention.

[0052] The closed-loop design significantly reduces the consumption of magnetic fluid, and the online filtration system can effectively remove impurities and extend the service life of the magnetic fluid. Flow control is set to ensure the stability of the liquid film thickness, and the above structure is easy to maintain and replace magnetic fluid through modular design.

[0053] The present invention also provides a method for preventing asphalt deposition, comprising the following steps: First, system initialization is performed, including equipment self-check, parameter setting, and preheating. Then, magnetofluid pre-laying is executed, injecting magnetofluid at a flow rate of 0.5~1.0 mL / min to form an initial liquid film on the pipe wall. Next, a magnetic field barrier is established, gradually increasing the magnetic field gradient to the operating point (1.0~1.5T). After the system stabilizes, crude oil is started to be delivered, controlling the flow rate within the set range. During operation, various parameters are continuously monitored, and the operating status is dynamically optimized through intelligent algorithms.

[0054] This method specifically includes: Step 1: System Self-Check. Turn on the main power supply of the device and start the PLC control program. The system checks the connection and communication status of each sensor and actuator in sequence to ensure that the data is read correctly and the actuator is in normal standby mode. Verify that the safety devices (such as the emergency stop button and pressure relief valve) are in their initial positions. The system loads the preset operating parameter configuration and performs a CRC check to verify the integrity of the program.

[0055] Step 2: Equipment Preheating. Start the temperature-controlled heating system and slowly increase the temperature at a rate of approximately 1℃ / min until the pipes and internal magnetic fluid reach the target operating temperature (e.g., 55℃). Slow heating avoids excessive stress on the equipment due to thermal expansion and contraction. Simultaneously, start the hydraulic power system, with each pump operating at standby speed to ensure continuous flow. If electromagnetic coils are used, their excitation power is connected but temporarily maintained at zero current, to be used gradually as the field is raised.

[0056] Step 3: Parameter Setting. The operator confirms or inputs operating parameters through the human-machine interface, including target magnetic field strength, planned crude oil flow rate, operating temperature setpoint, pressure limit, and operating time. The system records the parameters and transmits key thresholds to the monitoring and alarm module.

[0057] Step 4: Status Confirmation. Before entering formal operation, the system automatically observes various parameters for a period of time to ensure stability. If the temperature is within the acceptable range and constant, the outlet pressure of each pump is normal, the positions of all switches and valves 3, 7, 8, 9, and 10 are correct, and the magnetic field equipment is in normal standby mode, then the system can proceed to the next stage.

[0058] Phase Two: Magnetohydrodynamic Pre-arrangement Step 1: Magnetofluid Injection. Open valve 3, the switch valve from the magnetofluid storage tank to the pipeline inlet, and start the magnetofluid feed pump to slowly inject the magnetofluid into the bottom of the pipeline at a low speed of about 0.5 mL / min.

[0059] Step 2: Formation of the wetting film. Continue running the feed pump at a low flow rate to maintain the slow circulation of the magnetofluid within the pipe. This makes the initially formed magnetofluid film more uniform. Due to the surface tension of the magnetofluid itself and its good wetting properties against the pipe wall, the film will gradually spread from the bottom of the pipe along the entire pipe wall. After several minutes of circulation, a uniform film adhesion layer with a thickness of approximately 0.3–0.4 mm can be formed.

[0060] Step 3: Adjust flow balance. Slowly increase the speed of the magnetohydrodynamic (MHD) circulation pump to increase the circulation flow rate by 0.5 mL / min to continuously replenish the liquid film loss. At this point, the MHD forms a thin-layer circulation loop in the pipeline, continuously flushing the pipe wall to ensure that any initial impurities are carried away and the liquid film is completely and uninterruptedly covered. Pressure changes should be closely monitored throughout the process. Under normal circumstances, the pipeline pressure drop should be stable at 1–2 MPa. If any abnormality is detected, the adjustment should be paused.

[0061] Phase 3: Establishment of Magnetic Field Excitation Step 1: Gradually apply the magnetic field. After the magnetohydrodynamic film forms and the system parameters are normal, begin applying the working magnetic field. If it is electromagnetically driven, gradually increase the excitation current, smoothly raising the field at a rate of approximately 0.1 T / min, from 0 to the target magnetic flux density (e.g., 1.5 T). If it is permanently magnet driven, a similar gradual field application effect can be achieved by mechanically approaching the magnet or inserting it into the magnetic circuit. The entire field raising process lasts approximately 15 minutes. This device is permanently magnet driven.

[0062] Step 2: Magnetic Field Stabilization Control. When the magnetic field approaches the set strength, the control system reads data from each Hall sensor to determine the actual field strength and uniformity. If a slight drift or deviation from the set value (more than 0.05% change) is detected, compensation is made by moving the permanent magnet. The system records the baseline value after the magnetic field stabilizes, and then monitors the drift rate every minute, requiring the magnetic field drift to be less than 0.01% / min to ensure constant magnetic force during long-term operation.

[0063] Step 3: Check the magnetic field uniformity. Use the readings from the multi-point Hall sensors to compare the field strength at various circumferential locations along the pipe. If the maximum difference exceeds 5%, the field inhomogeneity may be due to the position or performance of the magnets, requiring adjustment. For permanent magnet arrays, the magnet spacing can be finely adjusted. Once uniformity is achieved (deviation within ±5%), the system enters the normal magnetic field maintenance state.

[0064] Step 4: Liquid Film Strengthening. With the establishment of a strong magnetic field and gradient field, the magnetofluid liquid film on the pipe wall undergoes significant changes: nanoparticles are magnetized and attract each other to form chains, transforming the liquid film from a thin, low-viscosity liquid layer into a viscoelastic semi-solid film. The apparent viscosity of the magnetofluid increases, and this increase in viscosity and particle chain formation enhances the liquid film's resistance to external disturbances (such as oil flow shear) by more than an order of magnitude. The liquid film thickness is redistributed to approximately 0.2–0.4 mm and adheres more uniformly to the pipe wall. Simultaneously, the adhesion force of the magnetofluid to the pipe wall increases, making it difficult for the liquid film to be mechanically peeled off under the influence of the magnetic field. At this point, a robust magnetofluid barrier layer has been established, providing protection for subsequent crude oil flow containing asphaltene.

[0065] Phase 4: Processing of Asphalt-Containing Crude Oil Step 1: Crude Oil Injection Preparation. Confirm that the crude oil has been preheated to between 50-66°C. The crude oil viscosity at this point is approximately 50–200 cP, allowing for smooth flow. Set the crude oil injection flow rate, which can be adjusted within the range of 0.5–5 mL / min according to experimental or production requirements.

[0066] Step 2: Crude Oil Entry and Flow Field Formation. Open the valve in the crude oil storage tank and start the crude oil inlet pump, allowing the asphaltene-containing crude oil to slowly flow into the inlet of the anti-deposition device. Simultaneously, maintain the magnetohydrodynamic (MHD) circulation pump at a low flow rate, allowing a small amount of MHD to continue flowing and renewing the pipe wall. This creates a layered structure in the flow cross-section: the center of the pipe mainly contains the newly entered crude oil, while the area near the pipe wall (0–0.5 mm thickness) remains a MHD wetting film, with a mixed transition layer in between. In this transition layer, some MHD is sheared out by the crude oil but quickly pulled back to the wall under the influence of the gradient magnetic field, thus achieving dynamic equilibrium.

[0067] Step 3: The anti-deposition barrier takes effect. When crude oil flows through the device, the asphaltenes it carries typically collide and aggregate in the fluid, forming larger colloids or particles. Without intervention, these asphaltenes aggregates will adhere to the pipe wall (especially oleophilic metal or mineral walls) upon contact, releasing heat and gradually depositing as scale. However, in the device of this invention, the pipe wall is completely covered by a magnetofluid film, preventing asphaltenes aggregates from directly approaching the actual pipe wall surface. They can only reach the interface between the magnetofluid film and the crude oil, which is approximately 0.3–0.4 mm from the actual pipe wall. This distance is far greater than the effective range of the intermolecular forces (van der Waals forces) of asphaltenes (typically <0.2 nm), so the asphaltenes particles are almost unaware of the solid wall surface. Furthermore, the presence of magnetofluid at the interface alters the interaction energy between asphaltenes and the surface. The adsorption free energy ΔE of asphaltenes on polar surfaces such as SiO2 on the pipe wall is approximately -5 to -8 kJ / mol, while the effective adsorption energy on the magnetofluid surface decreases to near 0 kJ / mol, significantly weakening its adhesion driving force thermodynamically. Coupled with the continuous action of the applied gradient magnetic field, the magnetofluid film remains stable and difficult to detach, preventing asphaltenes from adhering even if they wish to deposit. Ultimately, the asphaltenes are forced to flow out of the outlet along with the crude oil, achieving active suppression of asphaltenes deposition during the flow process.

[0068] Step 4: Real-time Monitoring and Adjustment. During normal operation, the device collects sensor data approximately every 10 seconds, which is then processed in real-time by the PLC. On one hand, it monitors whether the system is operating within the set parameters, such as maintaining a stable inlet-outlet pressure difference within the range of 1-3 MPa, temperature fluctuations not exceeding ±0.5℃, magnetic field strength maintained near the target value, and crude oil flow matching the set value. On the other hand, the monitoring data is used for dynamic adjustment: for example, if an increase in crude oil flow rate is detected causing a rise in pipeline pressure drop, the system can appropriately increase the magnetohydrodynamic pump flow rate or strengthen the magnetic field to consolidate the liquid film; if the temperature drops slightly, the heating power is automatically fine-tuned. Through closed-loop control, the asphaltene anti-deposition effect is effectively maintained under various fluctuation conditions.

[0069] Step 5: Abnormal Situation Response. The system is configured with abnormal judgment criteria. Alarms or protection actions will be triggered when the following conditions occur: If the pressure in a section of the pipeline suddenly increases by more than 30% above the normal value, it may indicate a rupture of the magnetofluid membrane and the beginning of asphalt deposition and blockage. The system will immediately increase the magnetic field gradient to attempt to repair the liquid film. If the pressure does not decrease, the crude oil flow rate will be reduced until automatic shutdown. If the temperature rises abnormally by more than 2°C, it suggests that the magnetofluid membrane may be damaged, leading to frictional heating or a sharp increase in crude oil viscosity. The system will reduce the magnetic field or flow rate and check if the heater is functioning properly. If the magnetic field strength decreases by more than 5% or abnormal fluctuations occur, it indicates a magnetic actuator malfunction. In this case, the system will issue an alarm and systematically shut down the crude oil feed to prevent asphalt deposition when there is no magnetic field. If the crude oil or magnetofluid flow rate deviates significantly from the set value, it indicates a possible leak or valve malfunction. The system will also stop the feed and notify maintenance.

[0070] Meanwhile, the online microscopic imaging system also helps to provide intuitive judgment: if it is observed that the local pipe wall begins to darken and become rough (signs of bituminous deposition) or that the liquid film is interrupted and has voids, it indicates that the anti-deposition barrier may have failed, and operation should be stopped in time and the liquid film should be re-established.

[0071] Phase 5: Liquid Discharge and Post-treatment Step 1: Produced Liquid Management. Crude oil protected by the magnetohydrodynamic barrier is collected at the pipeline outlet. Since asphaltenes do not precipitate or deposit within the pipeline during the entire flow process, the properties of the outlet crude oil are essentially the same as the inlet. An online viscometer or sampling port is installed at the outlet to monitor the crude oil viscosity. If the unit is operating normally, the outlet viscosity should not differ significantly from the inlet viscosity, indicating that no additional asphaltenes have accumulated or precipitated.

[0072] Step 2: Magnetofluid Recovery and Regeneration. When operation stops or maintenance is required, shut off the crude oil feed and start the magnetofluid circulation pump to collect the residual magnetofluid in the pipeline back to the storage tank. The pipeline inner wall can be flushed with a small amount of solvent to ensure complete removal of the magnetofluid. If the recovered magnetofluid shows no significant deterioration, it can be filtered to remove impurities and replenished with surfactant before reuse; if its performance deteriorates, new magnetofluid should be prepared and replenished. Regularly check the physicochemical properties of the magnetofluid to determine the replacement cycle.

[0073] Step 3: Equipment Inspection and Reset. After the device has cooled down, inspect and maintain the pipes and components. Pay special attention to ensuring the pipe walls are clean and free of asphalt residue to verify the effectiveness of the invention. If any residue is found, it can be removed mechanically or chemically. Then, re-inject the magnetic fluid and repeat the above process to prepare for the next operation.

[0074] Reference Figure 2This describes the overall structure of the device and the logical relationships between its various systems. The device mainly consists of an oil storage tank 1, a magnetofluid storage tank 2, a feed pump (P1), circulation pumps (P2-P3), a sensing and monitoring system 4, a magnetic field generation module 5, and a central control module 6, forming a complete closed-loop circulation system for preventing magnetofluid deposition. Oil storage tank 1 and magnetofluid storage tank 2 store pretreated magnetofluid or asphalt-containing crude oil. Heating and stirring units can be installed in the tanks to maintain fluid uniformity. Feed pump P1 injects magnetofluid into the pipeline at a set flow rate, controlling the film formation speed. Circulation pumps P2-P3 maintain the circulating flow of the magnetofluid, ensuring stable film thickness and continuous renewal. The sensing and monitoring system 4 includes temperature, pressure, and magnetic field strength monitoring modules for real-time feedback of operating status. The magnetic field generation module 5 consists of a permanent magnet array, generating an adjustable magnetic field gradient to maintain the adhesion of the magnetofluid film. Central Control Module 6: Using a PLC or host computer, it realizes parameter acquisition, closed-loop control and abnormal alarm. The system realizes the whole process of "magnetic fluid injection - liquid film formation - magnetic field maintenance - status feedback - automatic adjustment" through closed-loop operation.

[0075] Figure 3 The diagram illustrates the structural layout of the experimental pipe section and the relationship between the sensor positions. This pipe section serves as the core experimental area, used to verify the formation and anti-deposition effect of the magnetofluid liquid film. The magnet array, arranged in a ring along the outer wall of the pipe, forms a magnetic field gradient from the pipe wall to the pipe center, driving the magnetofluid to adhere to the wall surface and form a liquid film. A Hall effect magnetic field sensor (aj) is installed on the outside of the pipe to monitor the magnetic field strength and uniformity in real time. Thermometers, including thermometer 14 and thermometer 26, are located at the pipe inlet, middle, and end to monitor fluid temperature changes. Pressure gauges, including pressure gauge 15 and pressure gauge 29, are located at the inlet and outlet ends to measure the flow pressure drop, determine the integrity of the liquid film, and whether subsequent asphaltene deposition occurs. Camera 17 monitors the liquid film state and asphaltene deposition process through a transparent pipe window. The arrows indicate the direction of the magnetic field. This diagram reflects the multi-point distribution design of the monitoring system, enabling continuous monitoring of the coupled state of the magnetic field, flow, and deposition fields.

[0076] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative and not exhaustive. All modifications within the scope of this invention or its equivalents are included in this invention.

Claims

1. A system for preventing asphalt deposition based on a magnetohydrodynamic barrier, characterized in that, include: The pipeline body is used to transport crude oil containing bituminous substances; A magnetic field generating module is used to generate a magnetic field gradient from the pipe wall to the center of the pipe in the inner wall region of the pipe body. A magnetofluid supply module is used to supply magnetofluid into the pipe body; Driven by the magnetic field gradient, the magnetofluid forms a stable wetting film on the inner wall of the pipe, which physically isolates the asphalt from the pipe wall.

2. The system according to claim 1, characterized in that, The magnetic fluid supplied by the magnetic fluid supply module is prepared by the following method: S1: Preparation of iron ion precursor solution, wherein Fe 3+ with Fe 2+ The molar ratio is approximately 2:1; S2: Add an alkaline precipitant to the precursor solution and carry out a co-precipitation reaction under inert gas protection to generate Fe3O4 precursor; S3: The Fe3O4 precursor is subjected to hydrothermal annealing to obtain Fe3O4 nanoparticles; S4: The Fe3O4 nanoparticles are surface-modified using a silane coupling agent; S5: Surface-modified Fe3O4 nanoparticles and surfactants are co-dispersed in a mineral oil carrier and ultrasonically treated to form a stable magnetic fluid.

3. The system according to claim 1, characterized in that, The magnetic field generating module is a permanent magnet array arranged around the pipe, and the permanent magnet array is configured so that its corresponding magnetic poles face the pipe wall.

4. The system according to claim 1, characterized in that, It also includes a sensing and monitoring module, which includes: Pressure sensors are installed at the inlet and outlet of the pipeline; Temperature sensors are installed at different axial positions on the pipeline; Multiple magnetic field strength sensors are arranged around the pipe; And an online microscopic imaging device for real-time observation of the liquid film state on the tube wall.

5. The system according to claim 3, characterized in that, It also includes a central control module, which is signal-connected to the sensing and monitoring module, the magnetic field generating module, and the magnetohydrodynamic supply module, and is configured as follows: Receive data from the sensor monitoring module; Based on the data, the magnetic field parameters of the magnetic field generating module and the flow rate of the magnetofluid supply module are dynamically adjusted to maintain the stability and integrity of the wetting film during crude oil flow.

6. The system according to claim 1, characterized in that, The magnetofluid supply module includes a magnetofluid storage tank, a feed pump, and a circulation loop, used to recover and re-inject the magnetofluid flowing out of the pipeline to continuously renew the wetting fluid film.

7. A method for preventing asphaltene deposition using the system as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Pre-filming step: The magnetic fluid is injected into the pipe through the magnetic fluid supply module to pre-form an initial liquid film on the inner wall of the pipe; Barrier establishment steps: Activate the magnetic field generating module, apply and maintain a preset magnetic field gradient, so that the initial liquid film is strengthened under the action of the magnetic field to form a stable anti-deposition barrier; Crude oil transportation steps: Crude oil containing asphalt is introduced into a pipeline with the aforementioned anti-deposition barrier, so that the crude oil flows inside the barrier and is prevented from directly contacting the pipe wall.

8. The method according to claim 6, characterized in that, In the crude oil transportation step, the magnetofluid is maintained to flow through a circulation loop to dynamically replenish and renew the liquid film on the pipe wall.

9. The method according to claim 6, characterized in that, The operating parameters are monitored in real time by the sensing and monitoring module, and the magnetic field parameters and magnetofluid flow rate are dynamically adjusted by the central control module to respond to changes in operating conditions and ensure that the anti-deposition barrier remains effective.

10. An oil and gas transportation pipeline, comprising a pipeline, wherein the pipeline is manufactured using an anti-asphalt deposition system based on a magnetohydrodynamic barrier as described in any one of claims 1 to 5, characterized in that, The pipe contains an impregnating liquid film, which is formed on the inner wall of the pipe by a magnetofluid driven by a magnetic field gradient applied to the inner wall of the pipe, and serves as a physical barrier to isolate the asphalt from the pipe wall.

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