CN108317396B - Simulation device for removing wax plugging of underwater crude oil pipeline by electric heating - Google Patents

Abstract

The application discloses an electric heating releasing simulation device for wax blockage of an underwater crude oil pipeline, which comprises a wax oil preparation and loading and unloading system, a direct electric heating system and a measuring system, wherein a heating power supply is directly connected with a test pipeline section to form a current loop together, and a plurality of sensors for collecting information are arranged on the test pipeline section. The device has the functions of simulating the blockage removal process under different heating powers, different pipeline heat insulating materials and different water quality conditions, pipeline stop conveying temperature drop process and the like.

Description

Simulation device for removing wax plugging of underwater crude oil pipeline by electric heating

technical field

The invention relates to a simulation device for removing wax plugging in a pipe, in particular to a simulation device for removing wax plugging in an underwater crude oil pipeline by electric heating.

Background technique

At present, the production of offshore oil and gas has maintained a rapid growth trend. Waxy crude oil accounts for more than 80% of the crude oil produced in sea areas. It is characterized by high wax content and high freezing point. It faces severe flow security problems during submarine pipeline transportation.

Wax crystals in waxy crude oil will adhere to the inner wall of the pipeline and form a wax layer due to molecular diffusion, shear dispersion, gravity settlement or Brownian motion during transportation. At the same time, the wax layer also contains colloid, asphaltene, sand and other mechanical debris, as well as liquid hydrocarbons bound in the wax crystal grid. On the one hand, the existence of the wax layer increases the thermal resistance of the oil flow to the inner wall of the pipe, which reduces the total heat transfer coefficient of the pipe; Will increase operating costs. Therefore, in production, it is necessary to carry out regular pigging on the waxy crude oil pipeline to remove the wax layer. The most common method is to use a pig for mechanical pigging.

The pig moves forward in the pipe with the flow pressure difference of the crude oil in the pipe as the driving force, scrapes off the wax layer along the way and accumulates it at the front of the pig, when the wax layer in the pipe is thick or the amount of wax is large , it is very likely to cause wax blockage in front of the pig, seriously endangering the flow safety of the pipeline and causing huge economic losses. For wax plugging caused by such situations, traditional plugging removal methods include injection of chemical agents to remove plugging, gas lift and blasting to remove plugging, etc. However, the injection of chemical agents will cause pollution of crude oil in the pipeline, and it needs to be filtered before injecting the agent when it is recycled; gas lift and blasting will endanger the integrity of the pipeline. In short, the traditional plugging removal methods are affected by various limitations, the cost of plugging removal is high and the effect is not satisfactory.

In contrast, the electric heating method has the advantages of zero emission, zero pollution, no use of chemicals, no impact on pipeline integrity, and quick results. The electric heating method can be divided into indirect electric heating and direct electric heating. For pipelines using indirect electric heating, the heating equipment needs to be installed before the pipeline is laid. However, the connection method using direct electric heating - directly connecting the electrodes at both ends of the blocked pipe section - can be directly and conveniently installed on ordinary pipelines that have been put into use, and is more suitable for emergency unblocking of traditional pipelines. There have been many cases of plugging successfully implemented on land. However, this method still lacks corresponding theoretical research and practical experience in the unblocking of underwater pipelines.

Contents of the invention

The purpose of the present invention is to provide an underwater crude oil pipeline wax plugging electric heating removal simulation device.

The purpose of the present invention is achieved by the following technical solutions:

The underwater crude oil pipeline wax blockage electric heating release simulation device of the present invention, the underwater crude oil pipeline wax blockage electric heating release simulation device includes a wax oil preparation and loading and unloading system, a direct electric heating system and a measurement system;

The wax oil preparation and loading and unloading system includes a constant temperature water bath, a recovery tank and a test pipe section;

The two ends of the test pipe section are respectively provided with flanges, which are called A flange and B flange respectively. There are four interfaces on the A flange, and the ventilation and discharge pipes, high-temperature pressure sensors, and industrial endoscopes are installed respectively. And the wax oil loading and unloading pipeline, the ventilation and discharge pipeline is provided with a discharge needle valve, the wax oil loading and unloading pipeline is equipped with a needle valve, a plunger pump and a ball valve, and a probe type K type is installed on the B flange A thermocouple, a patch type thermocouple is installed on the tube wall of the test pipe section;

During the wax oil loading and heating test, the end of the ventilation and discharge pipeline is equipped with a beaker, and the end of the wax oil loading and unloading pipeline is connected to the constant temperature water bath;

When the wax oil is unloaded, the beaker is removed, the end height of the ventilation and discharge pipe is higher than the B flange, and the end of the wax oil loading and unloading pipe is connected with the recovery tank;

The test pipe section is placed in the simulated seawater in the pool, and its two ends are respectively suspended on the hanger by steel wire ropes, and the steel wire ropes at both ends are respectively provided with length adjustment devices.

It can be seen from the above-mentioned technical solutions provided by the present invention that the underwater crude oil pipeline wax blockage electric heating simulation device provided by the embodiment of the present invention utilizes the thermal conductivity of the pipe wall and conducts emergency response to the underwater waxy crude oil pipeline according to the principle of direct electric heating. Unblocking can simulate the unblocking process and rules of various working conditions, and record key data in real time for subsequent analysis.

Description of drawings

Fig. 1a is a schematic diagram of the wax oil preparation and loading and unloading system-loading working condition connection in the embodiment of the present invention.

Fig. 1b is a schematic diagram of connection of the wax oil preparation and loading and unloading system-unloading working condition of the embodiment of the present invention.

Fig. 2 is a schematic diagram of the connection of the direct electric heating and measurement system according to the embodiment of the present invention.

Fig. 3 is a layout diagram of the A flange during the direct electric heating test of the embodiment of the present invention.

Figures 4a-4c are respectively the layout diagrams of the uniform distribution, horizontal distribution, and circumferential distribution of the B flanges in the direct electric heating test of the embodiment of the present invention.

Fig. 5 is a layout diagram of thermocouples on the tube wall during the direct electric heating test according to the embodiment of the present invention.

Fig. 6 is a schematic diagram of the current distribution during the direct electric heating test of the embodiment of the present invention.

Explanation of figure markers:

1. Constant temperature water bath box, 2. Recovery tank, 3. Ball valve, 4. Piston pump, 5. A flange, 6. Test pipe section, 7. Steel wire rope, 8. Hanger, 9. Pool, 10. B flange , 11. Needle valve, 12. Measuring cup, 13. High temperature pressure sensor, 14. Probe type K-type thermocouple, 15. SMD type thermocouple, 16. Industrial endoscope, 17. Leakage needle valve, 18. Automatic Coupling regulator rectifier power supply, 19, data collector, 20, computer.

Detailed ways

The embodiments of the present invention will be further described in detail below. The content not described in detail in the embodiments of the present invention belongs to the prior art known to those skilled in the art.

The preferred embodiment of the underwater crude oil pipeline wax blockage electric heating release simulation device of the present invention is as follows:

Including wax oil preparation and loading and unloading system, direct electric heating system and measuring system;

The wax oil preparation and loading and unloading system includes a constant temperature water bath, a recovery tank and a test pipe section;

The two ends of the test pipe section are respectively provided with flanges, which are called A flange and B flange respectively. There are four interfaces on the A flange, and the ventilation and discharge pipes, high-temperature pressure sensors, and industrial endoscopes are installed respectively. And the wax oil loading and unloading pipeline, the ventilation and discharge pipeline is provided with a discharge needle valve, the wax oil loading and unloading pipeline is equipped with a needle valve, a plunger pump and a ball valve, and a probe type K type is installed on the B flange A thermocouple, a patch type thermocouple is installed on the tube wall of the test pipe section;

During the wax oil loading and heating test, the end of the ventilation and discharge pipeline is equipped with a beaker, and the end of the wax oil loading and unloading pipeline is connected to the constant temperature water bath;

When the wax oil is unloaded, the beaker is removed, the end height of the ventilation and discharge pipe is higher than the B flange, and the end of the wax oil loading and unloading pipe is connected with the recovery tank;

The test pipe section is placed in the simulated seawater in the pool, and its two ends are respectively suspended on the hanger by steel wire ropes, and the steel wire ropes at both ends are respectively provided with length adjustment devices.

The direct electric heating system includes a self-coupling voltage-regulating rectifying power supply, and the two poles of the auto-coupling voltage-regulating rectifying power supply are respectively installed at both ends of the test pipe section in a winding manner through cables.

After the cable is wound around the outer wall of the test pipe section for one week, the insulating rubber at the tail of the cable at the winding end is peeled off, so that the wire is in direct contact with the outer wall of the test pipe section and fixed on the outer wall of the test pipe section with insulating tape. The winding part is also insulated The adhesive tape is fixed to the outer wall of the test pipe section, and finally the simulated seawater is injected into the pool until it submerges the test pipe section.

The four interfaces of the A flange are arranged on the centerline of the A flange in the vertical direction, from top to bottom are point a, point b, point c and point d;

Point a is close to the top of the flange, which is an air hole and a discharge hole, and is the installation point of the ventilation and discharge pipeline;

Point b is located between two points a and c, and is the installation point of the high temperature pressure sensor (13);

Point c is located at the center of the flange and is the insertion point of the industrial endoscope (16);

Point d is located directly below point c, which is the installation point of the wax oil loading and unloading pipeline.

Thirteen probe-type K-type thermocouple sensors are installed on the B flange, and the probe-type K-type thermocouple sensors are evenly distributed on the flange or arranged horizontally on the cross-section or evenly distributed on concentric circles.

Four directions of up, down, left and right of a certain section of the test pipe section are selected, and four patch-type thermocouples are respectively arranged on the outer wall of the test pipe section.

The measurement system includes a computer, and the high-temperature pressure sensor, probe-type K-type thermocouple, patch-type thermocouple and industrial endoscope are connected to the computer through a data collector.

The material of the flange is stainless steel or plexiglass.

The theoretical basis of the present invention is:

In order to apply the electric heating method to the troubleshooting of underwater wax plugging, it is necessary to find out the distribution characteristics of the temperature field and its time-varying law during the wax plugging melting process based on the mechanism of phase change heat transfer and melting for different working conditions , and on this basis, establish the mathematical relationship between the electric heating intensity and the melting time of wax plugging, and provide a more accurate scientific basis for the safe plugging removal of pipelines, energy saving and emission reduction.

When removing plugging by electric heating, the axial temperature gradient is much smaller than the radial temperature gradient and can be ignored. Therefore, the present invention simplifies the three-dimensional model and only pays attention to the phase transition on the cross-section of the two-dimensional pipeline, but the melting phase transition of wax plugging Still a complicated process. First, the heat transfer objects and their heat transfer methods include: the pipe wall structure (insulation layer, pipe wall) and the surrounding waters, the heat transfer method is forced convection heat transfer; the heat transfer method between the inner wall of the pipe and the wax plug is heat conduction, The heat transfer mode between the solid wax plug and its liquid melt is natural convection heat transfer. It should be noted that the melting phase transition of the wax plug is a continuous process, and the phase transition occurs in a wide temperature range, so the solid phase The interface with the liquid phase is actually a solid-liquid mixing zone, that is, the fuzzy zone, and this zone is an important focus of theoretical research. In addition, there will be a small amount of gas in the pipeline, forming cavities at the top of the pipeline, which also affects the temperature field changes during blockage removal.

Based on the above analysis, the research methods that the present invention can adopt include theoretical analysis, numerical simulation and experimental research, reasonable theoretical analysis is the premise of numerical simulation and experimental research, and numerical simulation and experimental research are complementary and mutually verified relations, they The results can deepen the theoretical analysis. Therefore, for the direct electric heating plugging removal measures for underwater pipelines mentioned in the present invention, after a large number of theoretical analyzes and numerical simulations, it is necessary to carry out corresponding experimental research to test and analyze the feasibility and reliability of direct electric heating. To test the accuracy of the numerical simulation and the scientificity of the theoretical model. Therefore, the present invention proposes a laboratory research device for simulating the law of emergency plugging removal by direct electric heating of underwater waxy crude oil pipelines, and carrying out corresponding theoretical research.

The underwater crude oil pipeline wax blockage electric heating release simulation device of the present invention has the functions of simulating temperature field changes, blockage removal time, insulation layer efficiency, seawater conductivity, and crude oil solidification process after pipeline stoppage during the blockage removal process. It overcomes the shortcomings of the existing direct electric heating theory and insufficient experience in melting underwater waxy crude oil pipeline wax plugging.

The underwater crude oil pipeline wax plugging direct electric heating simulating device of the present invention comprises a wax oil preparation and loading and unloading system, a direct electric heating system and a measuring system.

Wax oil preparation and loading and unloading system, the system includes constant temperature water bath, recovery tank, plunger pump and test pipe section. The preparation of the wax oil is completed in a constant temperature water bath box, and is formed by mixing liquid paraffin and white oil according to a certain ratio (the wax content is respectively 5%, 10%, 15%, 20%, 25%, and 30%). When filling wax oil, the output end of the constant temperature water bath is connected to the input end of the plunger pump, and the output end of the plunger pump is connected to the input end of the test pipe section. When unloading wax oil, the input end of the test pipe section becomes the output end, which is connected with the input end of the plunger pump, and the output end of the plunger pump is connected with the input end of the recovery tank.

Direct electric heating system, the system is composed of test pipe section, flange, hanger, water tank and heating power supply. Among them, the material of the test pipe section is stainless steel, the diameter of the pipe is optimized according to the experimental requirements, and the pipe section can be disassembled to install a series of pipes with different diameters. The presence or absence of the insulation layer and the material can also be replaced; the flange is pre-installed. Temperature and pressure sensors, industrial endoscopes, and pressure relief ports are opened. The material is stainless steel or plexiglass, and different materials are selected according to experimental requirements; an adjustable length steel wire rope is installed on the hanger, and the steel wire rope is connected to both sides of the above test pipe section. The flange connection of the pipe is suspended and placed in the water tank to simulate the underwater environment; the preparation of the underwater environment depends on adding a certain proportion of sodium chloride, magnesium sulfate, calcium chloride, sodium bicarbonate, potassium chloride, etc. to pure water The ingredients are made into artificial seawater; the heating power supply is selected from a voltage-coupling rectifier power supply. This type of power supply has the obvious advantages of less consumables, low cost, small footprint, and large output power, and can rectify the AC input from the original party to DC. Therefore, the system can provide high-power DC current. The auto-coupling rectifier power supply and the test pipe section are connected by cables to form a closed circuit loop. When the DC current passes through the pipeline, the pipeline uses its own resistance to generate Joule heat to melt the inside of the tube. The wax plug provides heat.

Measurement system, which consists of thermocouple sensors, high temperature pressure sensors, industrial endoscopes, data collectors and computers. Thermocouple sensors include probe-type K-type thermocouples and patch-type thermocouples, which can measure the temperature of the medium in the tube and the outer wall of the tube respectively. Among them, a certain number of probe-type K-type thermocouples are installed on the A flange of the non-wax oil input/output side through threaded connections according to a certain arrangement, and a certain number of patch-type thermocouples are adhered with high-temperature-resistant glue On the outer wall of the pipe, it plays the role of current insulation from the pipe wall; the high temperature pressure sensor and the industrial endoscope are installed on the B flange on the side where the wax oil input/output port is opened through threaded connection. The above-mentioned thermocouple, high temperature pressure sensor, industrial endoscope and computer are connected through a data collector.

The beneficial effects of the present invention are:

By changing parameters such as heating power, insulation layer material, medium composition, and underwater environment, the unblocking process and pipeline temperature drop process can be simulated under various working conditions, and the temperature field change and unblocking process can be obtained through a variety of sensor combinations. The time, insulation layer efficiency, conductivity of seawater and other data have laid the foundation for the theoretical research and popularization of this technology.

Specific examples:

1. Construction of the simulation device

Referring to Fig. 1 and Fig. 2, the present application provides a simulation device for removing wax blockage of underwater crude oil pipeline by electric heating. The system includes a wax oil preparation and loading and unloading system, a direct electric heating system and a measurement system.

Figures 1a-1b are wax oil preparation and loading and unloading systems, which are used to prepare and transport wax oil into the test pipe section or to extract wax oil from the test pipe section. When the wax oil is prepared and loaded, the system includes a constant temperature water bath 1, a plunger pump 4 and a test pipe section 6; when the wax oil is unloaded, the system includes a recovery tank 2, a plunger pump 4 and a test pipe section 6. They are connected by stainless steel pipeline threads, and a ball valve 3 is installed between the constant temperature water bath 1 (recovery tank 2) and the plunger pump 4, and a needle valve 11 is installed between the plunger pump 4 and the test pipe section 6.

Wherein, both ends of the test pipe section 6 are sealed with flanges. In the following description, the A flange 5 is one end connected to the plunger pump 4, and the B flange 10 is the corresponding flange at the other end. Before the flange is fixed on the two ends of the pipe section, four interfaces are opened on the A flange, and the ventilation and discharge pipeline, the high temperature pressure sensor 13, the industrial endoscope 16 and the wax oil loading and unloading pipeline are installed respectively. For the convenience of observation, the material of A flange is selected as transparent plexiglass; the probe type K-type thermocouple 14 is installed on the B flange; the patch type thermocouple 15 is installed on the pipe wall. Among them, during the wax oil loading and heating test, the end of the drain needle valve 17 is equipped with a beaker 12, which facilitates the discharge of air and excess wax oil on the one hand, and judges whether the wax oil is full of the test pipe section 6; Dynamically collect the volume of wax oil overflowed due to thermal expansion, especially the rapid expansion of phase transition during electric heating, and weigh the mass in real time. When the wax oil is unloaded, the beaker 12 is removed and only the vent pipe is kept and the height of the vent pipe is guaranteed to be higher than the B flange, so as to maintain the air pressure balance inside and outside the test pipe 6 and facilitate the discharge of the wax oil.

On this basis, the test pipe section 6 is suspended by the steel wire rope 7 on the hanger 8, and the pipe section is in an inclined state by adjusting the length of the steel wire ropes on both sides, simulating the change of the inclination angle of the actual pipeline, and facilitating the loading and unloading of wax oil.

Figure 2 shows the direct electric heating system and measurement system. After the wax oil in the pipe is completely solidified, the high-temperature pressure sensor 13, the probe-type K-type thermocouple 14, the patch-type thermocouple 15 and the industrial endoscope 16 are connected to the computer 20 through the data collector 19, the purpose of which is to Record the corresponding data. The two stages of the self-coupling voltage regulating rectifier power supply 18 are installed on both ends of the test pipe section 6 in a winding manner through cables. It is in direct contact with the outer wall of the test pipe section and fixed on the outer wall of the pipe section with insulating tape, and the winding part is also fixed with the outer wall of the pipe section with insulating tape. Finally, water is injected into the pool 9 until the test pipe section is covered. The injected water can be prepared by adding a certain proportion of sodium chloride, magnesium sulfate, calcium chloride, sodium bicarbonate, potassium chloride and other components according to the test requirements to simulate seawater.

The simulation device is mainly used for scientific research, so its measurement system is a key component of the device. The sensors in the measurement system are mainly distributed on the flanges and pipe walls at both ends of the test pipe section. The distribution of sensors in the measurement system will be described in detail below.

As shown in Fig. 3, it is a layout diagram of the A flange 5 during the direct electric heating test. Point a is close to the top of the flange, which is an air hole and a discharge hole, and is equipped with a needle valve 17; point b is located between points a and c, and is the installation point of the high-temperature pressure sensor 13; point c is located in the center of the flange, It is the insertion point of the industrial endoscope 16; the point d is located directly below the point c, which is the installation point of the wax oil loading and unloading pipeline, and is equipped with a needle valve 11. Specifically, one end of the needle valve 17 at point a is threadedly connected to the A flange 5, and the other end is connected to the beaker through a pipeline during the wax oil loading and heating test. Whether it is full of the test pipe section 6, on the other hand, hold and measure the volume and quality of the wax oil overflowing due to thermal expansion during electric heating; the wax oil loading and unloading pipeline connected at point d is connected with the test pipe section 6 when the wax oil is loading and unloading, It is removed during the heating test to avoid heat loss.

Figures 4a-4c are the layout diagrams of the B flange 10 during the direct electric heating test. It is planned to install 13 probe-type K-type thermocouple sensors 14 on the B flange to measure the temperature field change of the cross-section of the pipeline during the unblocking process. According to different temperature measurement purposes, the distribution of thermocouple sensors includes but is not limited to the following three methods: As shown in Figure 4a, thermocouples are evenly distributed on the flange to measure the overall temperature field of a vertical section of the horizontal pipeline change; as shown in Figure 4b, the thermocouples are arranged horizontally on the cross section, which can be used to test the stratification of temperature; as shown in Figure 4c, the thermocouples are evenly distributed on concentric circles, which can be used to test the temperature on circles with different radii of the distribution.

The layout of thermocouples on the tube wall during the direct electric heating test is shown in Figure 5. Select the four directions of up, down, left and right of a certain section, and arrange four patch-type thermocouples 15 on the outer wall of the tube to monitor the heating of the tube wall.

2. General workflow

With reference to Figure 1a to Figure 5, the general workflow of the simulation device described in this application is:

1. Determine the waxy ratio of wax oil (5%, 10%, 15%, 20%, 25%, 30%), and calculate the required solid paraffin and white oil based on the 1.1-1.3 times of the volume of the test pipe section 6 volume;

②Pour the solid paraffin into the constant temperature water bath 1, after the solid paraffin is melted into liquid, pour the white oil into the constant temperature water bath 1 and stir with the liquid paraffin evenly;

③Adjust the steel wire rope to adjust the test pipe section 6 to the upward inclined state at the end of A flange 5, keep the ball valve 3, needle valve 11 and needle valve 17 in the open state, start the plunger pump 4, and pump the wax oil into the test pipe section 6, the pipe section Stop pumping after being filled with wax oil, close ball valve 3, needle valve 11 and needle valve 17;

④Remove the wax oil loading and unloading pipeline at point d, adjust the test pipe section 6 to the level, connect the high temperature pressure sensor 13, the probe type K-type thermocouple 14, the chip type thermocouple 15 and the industrial endoscope 16 to the computer and make For debugging, connect the auto-coupling rectifier power supply 18 and the test pipe section 6, and wait for the wax oil to fully solidify;

⑤ After the wax oil is fully solidified, inject artificial seawater into the pool 9, turn on the auto-voltage regulating rectifier power supply 18 and adjust it to the required voltage, and the test pipe section 6 will gradually melt the internal wax plug through Joule effect heating;

⑥Record and observe the data measured by each sensor during the melting process, and timely open the needle valve 17 at point a according to the pressure data to overflow the wax oil to ensure the safety of the experiment. After the paraffin is completely melted, turn off the power supply 18 and the needle valve 17 at point a , the single simulation plugging removal experiment is over;

⑦ When unloading the wax oil, replace the constant temperature water bath 1 with the recovery tank 2, exchange the input end and the output end of the plunger pump 4, tilt the A flange 5 end of the test pipe section 6 downward, and install the wax oil at point d Load and unload the pipeline, open the ball valve 3, the plunger pump 4, the needle valve 11 and the needle valve 17 to complete the recovery of wax oil.

3. Brief description of each function

In summary, the wax oil preparation and loading and unloading system, the direct electric heating system and the measurement system together constitute the simulation device in this application. With the help of this set of simulation device, the plugging removal simulation function of multi-working conditions can be realized, and in turn, the formation process of wax plugging can also be simulated when the pipeline is shut down. The main functions of this device will be described in detail below.

Function 1: Simulate the deblocking time and the temperature field change of the medium in the pipe under constant power

This is the most basic function of this simulation device. Adjust the auto-coupling rectifier power supply 18 to set different heating voltages, and obtain the temperature field changes in the tube under different heating powers through different combinations of thermocouple sensors installed on the B flange 10. Data and time required for unblocking. In addition, in order to improve the blocking removal efficiency, the voltage can also be properly adjusted during the heating process. It should be noted here that in order to ensure a safe heating temperature range, it is necessary to pay close attention to the temperature changes of the thermocouples 14 and 15 when adjusting the heating voltage.

The simulation process is:

Steps ①-⑥ are the same as those described above.

⑦Wait for the wax oil to fully solidify, turn on the auto-voltage regulating rectifier power supply 18 and adjust its voltage value to gradually melt the wax plug, record and observe the data measured by each sensor during the melting process, and timely open the needle valve 17 at point a according to the pressure data , to ensure the safety of the experiment, turn off the power supply 18 and the needle valve 17 at point a after the paraffin is completely melted;

⑧Repeat step ⑦ until all required data are obtained;

⑨ Same as step ⑦ in the general workflow.

Function 2: Simulate the thermal insulation performance of thermal insulation materials

In order to reduce energy loss in oil and gas transportation, underwater pipelines or subsea pipelines are usually equipped with insulation layers, but the selection of insulation layer materials and thickness is not the same. In order to test the thermal insulation performance of different thermal insulation materials, or to compare the heating efficiency with and without thermal insulation layer, to keep the heating power conditions of each unblocking experiment consistent, the water quality in the pool consistent, the ambient temperature consistent, and the thickness of the thermal insulation layer consistent, etc., use different The test pipe section is wrapped with high-quality thermal insulation material, and the thermal insulation performance is judged according to the length of the final unblocking time.

The simulation process is:

Steps ①-⑥ are the same as those described above.

⑦Wait for the wax oil to fully solidify, lift the test pipe section 6 from the water to the air, wrap it with a certain thickness of insulation layer and sink it into the pool 9, turn on the auto-coupling rectifier power supply 18 and keep the voltage value unchanged, record and observe According to the data measured by each sensor during the melting process, open the needle valve 17 at point a in good time according to the pressure data to ensure the safety of the experiment. After the paraffin is completely melted, turn off the power supply 18 and the needle valve 17 at point a;

⑧Repeat step ⑦, replace the insulation layer with different thickness and material each time until all the required data are obtained;

⑨ Same as step ⑦ in the general workflow.

Function 3: Simulate the conductivity of the underwater environment

The water quality environment of the underwater pipeline in the project is not pure water, and the direct electric heating method adopted by this simulation device means that not all the electric energy will pass through the test pipe section 6 when heating and unblocking, and the current is at the positive point where the power supply and the pipeline are connected. The electrode is divided into two paths, one part of the current flows on the tube wall, the other part of the current uses water as a conductor and flows in a path parallel to the pipeline, and the two currents converge at the negative electrode at the other end, as shown in Figure 6. Therefore, in order to simulate the conductivity of water in different water environments, artificial seawater (additional ingredients include sodium chloride, magnesium sulfate, calcium chloride, sodium bicarbonate, potassium chloride, etc.) can be configured in the pool 9 according to specific water quality data, After a single unblocking experiment, the conductivity of the artificial seawater was calculated based on the power consumption and heat absorption.

The simulation process is:

Steps ①-④ are the same as those described above.

⑤ After the wax oil is fully solidified, inject artificial seawater with the lowest ion concentration in the concentration to be tested into the pool 9, turn on the auto-coupling rectifier power supply 18 and adjust it to the required voltage, and the test pipe section will generate heat through the Joule effect to block the internal wax. gradually melted;

⑥Record and observe the data measured by each sensor during the melting process, and timely open the needle valve 17 at point a according to the pressure data to ensure the safety of the experiment. After the paraffin is completely melted, turn off the power supply 18 and the needle valve 17 at point a for a single simulation The unblocking experiment is over;

⑦Wait for the wax oil to fully solidify, lift the test pipe section 6 from the water to the air, add various salts to the pool 9 to the next level of concentration, turn on the auto-coupling rectifier power supply 18 and keep the voltage value unchanged, record and observe According to the data measured by each sensor during the melting process, open the needle valve 17 at point a in good time according to the pressure data to ensure the safety of the experiment. After the paraffin is completely melted, turn off the power supply 18 and the needle valve 17 at point a;

⑧Repeat step ⑦, according to the ion concentration from low to high ratio of seawater in each simulation, until all the required data are obtained;

⑨ Same as step ⑦ in the general workflow.

Function 4: Simulate the temperature drop process when the power supply is stopped

Submarine pipelines usually face planned or unexpected stoppages during operation. The stoppage will cause the temperature inside the pipeline to drop. At this time, the risk of wax plugging in waxy crude oil pipelines will increase. The simulation device can also be used to simulate the process of temperature drop in the pipeline under such circumstances.

The simulation process is:

Steps ①-③ are the same as those described above.

④Remove the wax oil loading and unloading pipeline, adjust the test pipe section 6 to the level, connect the high temperature pressure sensor 13, the probe type K-type thermocouple 14, the chip type thermocouple 15 and the industrial endoscope 16 to the computer and perform debugging;

⑤ Inject artificial seawater into the pool 9, record and observe the data measured by each sensor during the melting process, to ensure the safety of the experiment, and complete a wax plugging simulation experiment after the wax oil is fully solidified;

⑥ When the wax oil is unloaded, use the auto-coupling rectifier power supply 18 to melt the wax plug in the pipe, replace the constant temperature water bath 1 with the recovery tank 2, exchange the input end and the output end of the plunger pump 4, and test the pipe section 6. A flange 5 end is inclined downward, install the wax oil loading and unloading pipeline, open the ball valve 3, the plunger pump 4, the needle valve 11 and the needle valve 17, and complete the unloading of the wax oil.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person familiar with the technical field can easily conceive of changes or changes within the technical scope disclosed in the present invention. Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (2)

1. The device is characterized by comprising a wax oil preparation and loading and unloading system, a direct electric heating system and a measuring system;

the wax oil preparation and loading and unloading system comprises a constant-temperature water bath box (1), a recovery tank (2) and a test pipe section (6);

the two ends of the test pipe section (6) are respectively provided with a flange, namely an A flange (5) and a B flange (10), the A flange (5) is provided with four interfaces, a ventilation and drainage pipeline, a high-temperature pressure sensor (13), an industrial endoscope (16) and a wax oil loading and unloading pipeline are respectively installed, the ventilation and drainage pipeline is provided with a drainage needle valve (17), the wax oil loading and unloading pipeline is provided with a needle valve (11), a plunger pump (4) and a ball valve (3), the B flange (10) is provided with a probe type K thermocouple (14), and the wall of the test pipe section (6) is provided with a patch type thermocouple (15);

the wax-containing proportion of the wax oil comprises 5%, 10%, 15%, 20%, 25% and 30%;

during wax oil loading and heating test, the tail end of the ventilation and drainage pipeline is provided with a beaker (12), and the tail end of the wax oil loading and unloading pipeline is connected with the constant-temperature water bath box (1);

removing the beaker (12) when wax oil is unloaded, wherein the tail end of the ventilation and drainage pipeline is higher than the B flange (10), and the tail end of the wax oil loading and unloading pipeline is connected with the recovery tank (2);

the test pipe section (6) is arranged in simulated seawater in the pool (9), two ends of the test pipe section are respectively hung on the hanging bracket (8) through steel wire ropes (7), and the steel wire ropes (7) at the two ends are respectively provided with a length adjusting device;

the simulated seawater comprises the added components of sodium chloride, magnesium sulfate, calcium chloride, sodium bicarbonate and potassium chloride;

the direct electric heating system comprises an auto-coupling voltage-regulating rectifying power supply (18), wherein two poles of the auto-coupling voltage-regulating rectifying power supply (18) are respectively arranged at two ends of the test tube section (6) in a winding manner through cables;

after the cable is wound around the outer wall of the test tube section (6), the insulating rubber at the tail part of the cable at the winding end is peeled off, so that a lead is in direct contact with the outer wall of the test tube section (6) and is fixed on the outer wall of the test tube section (6) by using an insulating tape, the winding part is also fixed with the outer wall of the test tube section (6) by using the insulating tape, and finally, the simulated seawater is injected into the pool (9) until the test tube section (6) is over;

four interfaces of the A flange (5) are arranged on the central line of the A flange (5) in the vertical direction, and a point a, a point b, a point c and a point d are sequentially arranged from top to bottom;

the point a is close to the top of the flange and is an air hole and a drainage hole and is a mounting point of the ventilation drainage pipeline;

b points are positioned between the points a and c and are mounting points of the high-temperature pressure sensor (13);

c is positioned at the center of the flange and is the insertion point of the industrial endoscope (16);

d is a mounting point of the wax oil loading and unloading pipeline and is positioned right below the point c;

13 probe type K thermocouple sensors (14) are arranged on the B flange (10), and the probe type K thermocouple sensors (14) are uniformly distributed on the flange or horizontally arranged on the section or uniformly distributed on the concentric circumference;

selecting four directions of up, down, left and right of a certain section of the test tube section (6), and respectively arranging 4 patch thermocouples (15) on the outer wall of the test tube section (6);

the measuring system comprises a computer (20), wherein the high-temperature pressure sensor (13), the probe type K thermocouple (14), the patch thermocouple (15) and the industrial endoscope (16) are connected to the computer (20) through a data collector (19);

the device can simulate the plugging removing process and the pipeline transportation stopping temperature lowering process under various working conditions by changing heating power, heat preservation materials, medium components and underwater environmental parameters, and obtain the conductive data of temperature field change, plugging removing time, heat preservation efficiency and seawater by various sensor combination modes.

2. The device for simulating the removal of wax-blocking electrical heating of an underwater crude oil pipeline according to claim 1, wherein the flanges (5, 10) are made of stainless steel or plexiglass.