Working electrode, testing device and method for simulating pipeline solid-phase particle deposition working condition

Abstract

The invention discloses a working electrode for simulating a pipeline solid-phase particle deposition working condition, which comprises carbon steel, the carbon steel is packaged on a bearing table made of an insulating material, the test surface of the carbon steel is exposed outside the bearing table, the non-test surface of the carbon steel is connected with one end of a working electrode wire, and the other end of the working electrode wire extends out of the bearing table. The bearing table is sleeved with a check ring made of an insulating material, the testing surface of the carbon steel is located in the check ring, a solid-phase particle layer is laid on the testing surface of the carbon steel, a molecular sieve plate is arranged on the side, away from the testing surface of the carbon steel, of the solid-phase particle layer, and the molecular sieve plate is installed in the check ring and abuts against the solid-phase particle layer. The invention further discloses a testing device and method using the working electrode. The invention aims to provide the working electrode, the testing device and the method for simulating the pipeline solid-phase particle deposition working condition, and the working electrode, the testing device and the method can truly simulate the internal environment of an oil field gathering and transportation pipeline and can be used for pipeline corrosion behavior research and corrosion inhibitor evaluation and optimization research.

Description

Technical Field

[0001] The invention relates to the field of corrosion electrochemistry, and in particular to a working electrode, a testing device and a method for simulating pipeline solid-phase particle deposition conditions. Background Art

[0002] Oil and natural gas is an extremely important energy source. With the continuous deepening of oil and gas field exploitation, more and more corrosion problems continue to emerge, which not only causes huge economic losses, but also pollutes the environment and threatens personal safety. At present, solid phase particle deposition plays an important role in the corrosion rate and morphology of industrial steel in the production environment, and affects the use effect of corrosion inhibitors. In actual working conditions, solid phase deposits under multiphase stratified flow accumulate at the bottom of the pipeline. These solid phase deposits may come from sand scale and clay, corrosion products and mineral scale in the reservoir. The corrosion inhibitor forms a protective layer by adsorption on the surface of the pipe wall, but the presence of solid deposits will absorb and consume a large amount of corrosion inhibitors. This consumption may cause the corrosion inhibitor to drop below the minimum effective concentration. Solid deposits will not only affect the performance of the corrosion inhibitor, but also have an adverse effect on other aspects such as the production and development of oil and gas fields. It is known that sand scale particles can cause erosion and corrosion, and cause serious damage under deposition. After solid phase particle deposition occurs inside the pipeline, the transportation cross-sectional area inside the pipeline is reduced, the transportation efficiency is reduced, and in severe cases, the transportation pipeline will be blocked and scrapped, affecting the safe and efficient operation of the pipeline. Therefore, it is necessary to study the effect of solid particle deposition in oil field pipelines on corrosion and the effectiveness of corrosion inhibitors.

[0003] Due to the complexity of the internal environment of oil field pipelines, the difficulty of corrosion condition simulation and descaling has increased. At present, the corrosion behavior test of carbon steel (the material of oil pipelines) under solid phase particle deposition conditions mainly uses corrosion electrochemical test methods in China, and the preparation of samples is to lay the sand layer directly on the surface of the metal substrate. On the one hand, due to environmental factors, the sand layer is easy to slide on the surface of the sample, resulting in uneven coverage of the sand layer; on the other hand, the real simulation of oil field transportation conditions and the effectiveness evaluation of corrosion inhibitors cannot be accurately controlled. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a working electrode, a testing device and a method for simulating the solid-phase particle deposition condition of a pipeline, which can truly simulate the internal environment of an oilfield gathering and transportation pipeline and can be used for the study of pipeline corrosion behavior and the evaluation and optimization of corrosion inhibitors.

[0005] The working electrode for simulating the solid-phase particle deposition condition in a pipeline in the present invention comprises a carbon steel provided with a test surface, wherein the carbon steel is encapsulated on a supporting platform made of an insulating material, the test surface of the carbon steel is exposed outside the supporting platform, the non-test surface of the carbon steel is connected to one end of the working electrode wire, the other end of the working electrode wire passes through the supporting platform and extends to the outside of the supporting platform, the supporting platform is provided with a retaining ring made of an insulating material, the test surface of the carbon steel is located in the retaining ring, a solid-phase particle layer is laid on the test surface of the carbon steel, a molecular sieve plate is provided on the side of the solid-phase particle layer away from the carbon steel test surface, and the molecular sieve plate is installed in the retaining ring and abuts against the solid-phase particle layer.

[0006] The working electrode of the present invention simulates the working condition of solid-phase particle deposition in a pipeline, wherein the supporting platform is cylindrical, the carbon steel is plate-shaped, the two plate surfaces of the carbon steel are respectively a test surface and a non-test surface, the two end surfaces of the supporting platform are respectively a load-bearing surface and a non-load-bearing surface, the carbon steel is encapsulated on the load-bearing surface of the supporting platform, the shape of the retaining ring is a circle that matches the outer peripheral wall of the supporting platform, the retaining ring is mounted on the outer peripheral wall of one end of the load-bearing surface of the supporting platform, the molecular sieve plate is a circle that matches the inner peripheral wall of the retaining ring, and the molecular sieve plate is installed on the inner peripheral wall of the retaining ring.

[0007] The test device for simulating the working condition of solid-phase particle deposition in a pipeline in the present invention comprises a sealed test tank, in which the above-mentioned working electrode is arranged, and a reference electrode and an auxiliary electrode are also arranged in the test tank, the working electrode is connected to an electrochemical workstation outside the test tank through a working electrode wire, the reference electrode is connected to the electrochemical workstation through a reference electrode wire, the auxiliary electrode is connected to the electrochemical workstation through an auxiliary electrode wire, the electrochemical workstation is connected to a computer, and the test tank is connected to a nitrogen cylinder, a carbon dioxide cylinder and an exhaust gas treatment device through air pipes, respectively.

[0008] The test device of the present invention simulates the working condition of solid-phase particle deposition in a pipeline, wherein one end of a first air pipe is provided in the test tank, the other end of the first air pipe passes through the test tank and extends to the outside of the test tank, the other end of the first air pipe is connected to a second air pipe and a third air pipe, the second air pipe is connected to a nitrogen cylinder, the third air pipe is connected to a carbon dioxide cylinder, and the test tank is connected to an exhaust gas treatment device through a fourth air pipe.

[0009] The test method for simulating the solid-phase particle deposition condition in a pipeline in the present invention comprises the following steps:

[0010] Make a working electrode, and put the working electrode, reference electrode and auxiliary electrode into a sealed test tank.

[0011] Simulate the composition of produced water from the on-site oil field, prepare the corrosion solution, inject the prepared corrosion solution into the test tank and make the liquid level of the corrosion solution higher than the working electrode, reference electrode and auxiliary electrode.

[0012] Place the test tank in a water bath to keep it warm, and heat the water in the water bath to the required temperature and keep it constant.

[0013] Connect the test tank to the nitrogen cylinder, carbon dioxide cylinder and waste gas treatment device through air pipes. First, introduce nitrogen into the corrosion solution in the test tank through the nitrogen cylinder to deoxygenate. After deoxygenation, introduce carbon dioxide gas into the corrosion solution in the test tank through the carbon dioxide cylinder until saturation. Let the waste gas generated during the introduction of nitrogen and carbon dioxide gas flow into the waste gas treatment device.

[0014] Connect the working electrode, reference electrode and auxiliary electrode to the electrochemical workstation, and connect the electrochemical workstation to the computer.

[0015] Turn on the electrochemical workstation and computer, and obtain the electrochemical impedance spectroscopy curve and potentiodynamic polarization curve as required.

[0016] After the test is completed, shut down the electrochemical workstation and computer in turn, and clean up and sweep the test equipment.

[0017] The test method for simulating the solid-phase particle deposition condition in a pipeline in the present invention comprises the following steps:

[0018] Make a working electrode, and put the working electrode, reference electrode and auxiliary electrode into a sealed test tank.

[0019] Simulate the composition of produced water from the on-site oil field, prepare the corrosion solution, then add an appropriate amount of corrosion inhibitor to the prepared corrosion solution, and then inject the corrosion solution into the test tank and make the liquid level of the corrosion solution higher than the working electrode, reference electrode and auxiliary electrode.

[0020] Place the test tank in a water bath to keep it warm, and heat the water in the water bath to the required temperature and keep it constant.

[0021] Connect the test tank to the nitrogen cylinder, carbon dioxide cylinder and waste gas treatment device through air pipes. First, introduce nitrogen into the corrosion solution in the test tank through the nitrogen cylinder to deoxygenate. After deoxygenation, introduce carbon dioxide gas into the corrosion solution in the test tank through the carbon dioxide cylinder until saturation. Let the waste gas generated during the introduction of nitrogen and carbon dioxide gas flow into the waste gas treatment device.

[0022] Connect the working electrode, reference electrode and auxiliary electrode to the electrochemical workstation, and connect the electrochemical workstation to the computer.

[0023] Turn on the electrochemical workstation and computer, and obtain the electrochemical impedance spectroscopy curve and potentiodynamic polarization curve as required.

[0024] After the test is completed, shut down the electrochemical workstation and computer in turn, and clean up and sweep the test equipment.

[0025] In the test method for simulating the solid-phase particle deposition condition in a pipeline of the present invention, the specific steps of making the working electrode are:

[0026] A plate-shaped carbon steel is manufactured, and the two surfaces of the carbon steel are respectively marked as the test surface and the non-test surface. A copper wire for connecting to the electrochemical workstation is welded on the non-test surface of the carbon steel and encapsulated with an insulating material.

[0027] During the packaging process, the insulating material is made into a cylindrical carrier platform, and the two end surfaces of the carrier platform are respectively recorded as the load-bearing surface and the non-load-bearing surface. The carbon steel is packaged on the load-bearing surface of the carrier platform and only the test surface of the carbon steel is exposed outside the carrier platform. At the same time, the copper wire passes through the carrier platform and extends outside the carrier platform.

[0028] The test surface of the carbon steel was polished step by step with 600#, 800# and 1200# water-abrasive sandpaper, then rinsed with deionized water, dehydrated with alcohol, and dried with cold air. Then the carbon steel and the carrier were placed in a dryer for later use.

[0029] Use insulating material to make a retaining ring that matches the outer wall of the carrier platform. Take the carbon steel and the carrier platform out of the dryer, and put the retaining ring on the outer wall of one end of the carrier surface of the carrier platform, and let the test surface of the carbon steel be located in the retaining ring. Then lay a solid phase particle layer of the required thickness on the test surface of the carbon steel.

[0030] A molecular sieve plate with a suitable mesh size that matches the inner wall of the retaining ring is made, and the molecular sieve plate is installed in the retaining ring and abuts against the solid phase particle layer, so that the corrosive solution can pass through the molecular sieve plate and contact the test surface of the carbon steel, while the solid phase particles cannot pass through the molecular sieve plate and enter the corrosive solution.

[0031] Thus, a working electrode was prepared.

[0032] The working electrode, test device and method for simulating the solid-phase particle deposition working condition of the pipeline of the present invention are different from the prior art in that the solid-phase particle layer on the test surface of the working electrode in the present invention will not slide off the test surface under the restriction of the retaining ring and the molecular sieve plate, and the working electrode, the reference electrode and the auxiliary electrode are all placed in the test tank, and the corrosion solution simulating the components of the produced water of the field oil field is added in the test tank, and the working electrode, the reference electrode and the auxiliary electrode are connected to the electrochemical workstation, and the electrochemical workstation is connected to the computer, and nitrogen and carbon dioxide gas are successively introduced into the corrosion solution during the test, so that the present invention can truly simulate the corrosion environment of the solid-phase particle deposition of the oil and gas pipeline, and can be used in the laboratory to carry out the simulation research work of the solid-phase particle deposition in the oil and gas pipeline, and explore the corrosion mechanism of carbon steel under the solid-phase particle deposition working condition. At the same time, during the use of the present invention, an appropriate amount of corrosion inhibitor can be added to the corrosion solution, and the test results of the corrosion inhibitor added and the test results of the corrosion inhibitor not added can be compared with each other, so that the corrosion inhibitor can be evaluated and screened.

[0033] The present invention will be further described below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the structure of the test device for simulating the solid-phase particle deposition condition in the pipeline in the present invention;

[0035] Figure 2 It is a front view of the working electrode in the present invention;

[0036] Figure 3 It is a front cross-sectional view of the working electrode in the present invention;

[0037] Figure 4 is another front cross-sectional view of the working electrode in the present invention;

[0038] Figure 5 A top view of the working electrode of the present invention;

[0039] Figure 6 It is a bottom view of the working electrode in the present invention. DETAILED DESCRIPTION

[0040] like Figure 2 As shown, combined with Figure 3-6As shown, the working electrode 4 for simulating the solid-phase particle deposition condition in the pipeline in the present invention includes a carbon steel 25 provided with a test surface, the carbon steel 25 is encapsulated on a supporting platform 21 made of insulating material, the test surface of the carbon steel 25 is exposed outside the supporting platform 21, the non-test surface of the carbon steel 25 is connected to one end of the working electrode wire 15, the other end of the working electrode wire 15 passes through the supporting platform 21 and extends to the outside of the supporting platform 21, the supporting platform 21 is provided with a retaining ring 20 made of insulating material, the test surface of the carbon steel 25 is located in the retaining ring 20, a solid-phase particle layer 24 is laid on the test surface of the carbon steel 25, and a molecular sieve plate 23 is provided on the side of the solid-phase particle layer 24 away from the test surface of the carbon steel 25, and the molecular sieve plate 23 is installed in the retaining ring 20 and abuts against the solid-phase particle layer 24.

[0041] The working electrode 4 of the present invention simulates the working condition of solid-phase particle deposition in a pipeline, wherein the supporting platform 21 is cylindrical, the carbon steel 25 is plate-shaped, the two plate surfaces of the carbon steel 25 are respectively a test surface and a non-test surface, the two end surfaces of the supporting platform 21 are respectively a bearing surface and a non-bearing surface, the carbon steel 25 is encapsulated on the bearing surface of the supporting platform 21, the shape of the retaining ring 20 is a circle that matches the outer peripheral wall of the supporting platform 21, the retaining ring 20 is mounted on the outer peripheral wall of one end of the bearing surface of the supporting platform 21, the molecular sieve plate 23 is a circle that matches the inner peripheral wall of the retaining ring 20, and the molecular sieve plate 23 is installed on the inner peripheral wall of the retaining ring 20.

[0042] like Figure 1 As shown, the test device for simulating the working condition of solid-phase particle deposition in a pipeline in the present invention comprises a sealed test tank 3, in which the above-mentioned working electrode 4 is arranged, and a reference electrode 6 and an auxiliary electrode 5 are also arranged in the test tank 3, the working electrode 4 is connected to the electrochemical workstation 8 outside the test tank 3 through a working electrode wire 15, the reference electrode 6 is connected to the electrochemical workstation 8 through a reference electrode wire 16, the auxiliary electrode 5 is connected to the electrochemical workstation 8 through an auxiliary electrode wire 17, the electrochemical workstation 8 is connected to a computer 9 through a wire 19, and the test tank 3 is respectively connected to a nitrogen cylinder 1, a carbon dioxide cylinder 2 and an exhaust gas treatment device 7 through air pipes.

[0043] The test device of the present invention simulates the working condition of solid-phase particle deposition in a pipeline, wherein one end of a first air pipe 14 is provided in the test tank 3, the other end of the first air pipe 14 passes through the test tank 3 and extends to the outside of the test tank 3, the other end of the first air pipe 14 is connected to a second air pipe 12 and a third air pipe 13, the second air pipe 12 is connected to a nitrogen cylinder 1, the third air pipe 13 is connected to a carbon dioxide cylinder 2, and the test tank 3 is connected to an exhaust gas treatment device 7 via a fourth air pipe 18.

[0044] like Figure 1As shown, the test method for simulating the solid-phase particle deposition condition in the pipeline in the present invention comprises the following steps:

[0045] A working electrode 4 is prepared, and the working electrode 4, the reference electrode 6 and the auxiliary electrode 5 are placed in a sealed test tank 3.

[0046] Simulate the composition of produced water from an on-site oil field, prepare a corrosion solution 22, inject the prepared corrosion solution 22 into the test tank 3 and make the liquid level of the corrosion solution 22 higher than the working electrode 4, the reference electrode 6 and the auxiliary electrode 5.

[0047] Place the test tank 3 in a water bath to keep it warm, and heat the water in the water bath to the required temperature (70°C) and keep it constant.

[0048] The test tank 3 is connected to the nitrogen cylinder 1, the carbon dioxide cylinder 2 and the waste gas treatment device 7 through the air pipes. First, nitrogen is introduced into the corrosion solution 22 in the test tank 3 through the nitrogen cylinder 1 for deoxygenation (nitrogen is introduced for more than half an hour). After deoxygenation, carbon dioxide gas is introduced into the corrosion solution 22 in the test tank 3 through the carbon dioxide cylinder 2 until saturation (carbon dioxide gas is introduced for more than two hours). The waste gas generated during the introduction of nitrogen and carbon dioxide gases flows into the waste gas treatment device 7.

[0049] The working electrode 4, the reference electrode 6 and the auxiliary electrode 5 are all connected to the electrochemical workstation 8 (the working electrode 4 is connected to the electrochemical workstation 8 via the working electrode wire 15, the reference electrode 6 is connected to the electrochemical workstation 8 via the reference electrode wire 16, and the auxiliary electrode 5 is connected to the electrochemical workstation 8 via the auxiliary electrode wire 17), and the electrochemical workstation 8 is connected to the computer 9 via the wire 19,

[0050] Turn on the electrochemical workstation 8 and the computer 9, and obtain the electrochemical impedance spectroscopy curve and the potentiodynamic polarization curve as required.

[0051] After the test is finished, the electrochemical workstation 8 and the computer 9 are shut down in sequence, and the test device is cleaned and cleared.

[0052] like Figure 1 As shown, in order to evaluate the performance of the corrosion inhibitor, an appropriate amount of corrosion inhibitor can be added to the corrosive solution 22, and then the test is performed, that is, the test method for simulating the solid phase particle deposition condition of the pipeline in the present invention includes the following steps:

[0053] A working electrode 4 is prepared, and the working electrode 4, the reference electrode 6 and the auxiliary electrode 5 are placed in a sealed test tank 3.

[0054] Simulate the composition of produced water from an on-site oil field, prepare a corrosion solution 22, then add an appropriate amount of corrosion inhibitor to the prepared corrosion solution 22, and then inject the corrosion solution 22 into the test tank 3 and make the liquid level of the corrosion solution 22 higher than the working electrode 4, the reference electrode 6 and the auxiliary electrode 5.

[0055] Place the test tank 3 in a water bath to keep it warm, and heat the water in the water bath to the required temperature (70°C) and keep it constant.

[0056] The test tank 3 is connected to the nitrogen cylinder 1, the carbon dioxide cylinder 2 and the waste gas treatment device 7 through the air pipes. First, nitrogen is introduced into the corrosion solution 22 in the test tank 3 through the nitrogen cylinder 1 for deoxygenation (nitrogen is introduced for more than half an hour). After deoxygenation, carbon dioxide gas is introduced into the corrosion solution 22 in the test tank 3 through the carbon dioxide cylinder 2 until saturation (carbon dioxide gas is introduced for more than two hours). The waste gas generated during the introduction of nitrogen and carbon dioxide gases flows into the waste gas treatment device 7.

[0057] The working electrode 4, the reference electrode 6 and the auxiliary electrode 5 are all connected to the electrochemical workstation 8 (the working electrode 4 is connected to the electrochemical workstation 8 via the working electrode wire 15, the reference electrode 6 is connected to the electrochemical workstation 8 via the reference electrode wire 16, and the auxiliary electrode 5 is connected to the electrochemical workstation 8 via the auxiliary electrode wire 17), and the electrochemical workstation 8 is connected to the computer 9 via the wire 19,

[0058] Turn on the electrochemical workstation 8 and the computer 9, and obtain the electrochemical impedance spectroscopy curve and the potentiodynamic polarization curve as required.

[0059] After the test is finished, the electrochemical workstation 8 and the computer 9 are shut down in sequence, and the test device is cleaned and cleared.

[0060] By comparing and analyzing the test results of the corrosion solution 22 with the corrosion inhibitor added thereto and the test results of the corrosion solution 22 without the corrosion inhibitor added thereto, the corrosion inhibitor can be evaluated and screened.

[0061] like Figure 2-6 As shown, the test method for simulating the solid-phase particle deposition condition in the pipeline in the present invention, wherein the specific steps of making the working electrode 4 are:

[0062] A plate-shaped carbon steel 25 is prepared, and two plate surfaces of the carbon steel 25 are respectively marked as a test surface and a non-test surface. A copper wire (i.e., the working electrode wire 15 mentioned above) for connecting to the electrochemical workstation 8 is welded on the non-test surface of the carbon steel 25 and encapsulated with an insulating material.

[0063] During the packaging process, the insulating material is made into a cylindrical carrier 21, and the two end surfaces of the carrier 21 are respectively recorded as the bearing surface and the non-bearing surface. The carbon steel 25 is packaged on the bearing surface of the carrier 21 and only the test surface of the carbon steel 25 is exposed outside the carrier 21. At the same time, the copper wire passes through the carrier 21 and extends to the outside of the carrier 21.

[0064] The test surface of the carbon steel 25 was polished step by step using 600#, 800# and 1200# water-abrasive sandpapers respectively, then rinsed with deionized water, dehydrated with alcohol, and dried with cold air. Then, the carbon steel 25 and the carrier 21 were placed in a dryer for standby use.

[0065] A retaining ring 20 is made of insulating material to match the outer peripheral wall of the carrier 21. The carbon steel 25 and the carrier 21 are taken out of the dryer, and the retaining ring 20 is mounted on the outer peripheral wall of one end of the carrier surface of the carrier 21, and the test surface of the carbon steel 25 is located inside the retaining ring 20. Then, a solid phase particle layer 24 of a required thickness is laid on the test surface of the carbon steel 25.

[0066] A molecular sieve plate 23 with a suitable mesh size and matching the inner wall of the retaining ring 20 is manufactured, and the molecular sieve plate 23 is installed in the retaining ring 20 and abuts against the solid phase particle layer 24, so that the corrosive solution 22 can pass through the molecular sieve plate 23 and contact the test surface of the carbon steel 25, while the solid phase particles cannot pass through the molecular sieve plate 23 and enter the corrosive solution 22.

[0067] Thus, the working electrode 4 was prepared.

[0068] The working electrode 4, the testing device and the method for simulating the solid-phase particle deposition working condition of the pipeline of the present invention are different from the prior art in that the solid-phase particle layer 24 on the testing surface of the working electrode 4 of the present invention will not slide off the testing surface under the restriction of the retaining ring 20 and the molecular sieve plate 23, and the working electrode 4, the reference electrode 6 and the auxiliary electrode 5 are all placed in the testing tank 3, and the corrosive solution 22 simulating the components of the produced water in the on-site oil field is added to the testing tank 3, and the working electrode 4, the reference electrode 6 and the auxiliary electrode 5 are connected to the electrochemical workstation 8, and the electrochemical workstation 8 is connected to the computer 9, and nitrogen and carbon dioxide gases are successively introduced into the corrosive solution 22 during the test, so that the present invention can truly simulate the corrosion environment of solid-phase particle deposition in oil and gas pipelines, and can be used in laboratories to carry out simulation research on solid-phase particle deposition in oil and gas pipelines, and explore the corrosion mechanism of carbon steel 25 under solid-phase particle deposition working conditions. Meanwhile, during the use of the present invention, a proper amount of corrosion inhibitor may be added to the corrosive solution 22, and the test results with the corrosion inhibitor added may be compared with the test results without the corrosion inhibitor added, so as to evaluate and screen the corrosion inhibitor.

[0069] For the convenience of control, a pressure reducing valve 10 and a control valve 11 are provided on both the second air pipe 12 and the third air pipe 13, and the pressure reducing valve 10 on the second pipeline is closer to the nitrogen cylinder 1 than the control valve 11, and the pressure reducing valve 10 on the third pipeline is closer to the carbon dioxide cylinder 2 than the control valve 11. One end of the first air pipe 14 located in the test tank 3 extends into the corrosive solution 22, so that nitrogen and carbon dioxide gas can be passed into the corrosive solution 22. One end of the fourth air pipe 18 located in the test tank 3 is arranged above the liquid surface of the corrosive solution 22, so that the exhaust gas can enter the exhaust gas treatment device 7 from the fourth air pipe 18. The exhaust gas can be discharged into the environment after being purified by the exhaust gas treatment device 7. It should be noted that the exhaust gas treatment device 7 can adopt conventional exhaust gas treatment means, such as setting an acid and alkali solution in the container for neutralization treatment, setting an activated carbon adsorption layer in the container for purification treatment, and using ultraviolet light for decomposition treatment. The selection is made according to the composition of the exhaust gas, and is not limited here.

[0070] When nitrogen is introduced into the corrosive solution 22 in the test tank 3, the pressure reducing valve 10 and the control valve 11 on the third air pipe 13 are closed first, and then the pressure reducing valve 10 and the control valve 11 on the second air pipe 12 are opened, so that the nitrogen in the nitrogen bottle 1 is introduced into the corrosive solution 22 in the test tank 3 through the second air pipe 12 and the first air pipe 14 in sequence. Since the pressure reducing valve 10 on the second air pipe 12 is closer to the nitrogen bottle 1 than the control valve 11, the nitrogen flows through the pressure reducing valve 10 first and then through the control valve 11 when flowing through the second air pipe 12.

[0071] After the nitrogen is passed through, the pressure reducing valve 10 and the control valve 11 on the second air pipe 12 are closed, and then the pressure reducing valve 10 and the control valve 11 on the third air pipe 13 are opened, so that the carbon dioxide gas in the carbon dioxide cylinder 2 is passed through the third air pipe 13 and the first air pipe 14 in turn into the corrosive solution 22 in the test tank 3. Since the pressure reducing valve 10 on the third air pipe 13 is closer to the carbon dioxide cylinder 2 than the control valve 11, when the carbon dioxide gas flows through the third air pipe 13, it first flows through the pressure reducing valve 10 and then flows through the control valve 11. After the carbon dioxide gas is passed through, the pressure reducing valve 10 and the control valve 11 on the third air pipe 13 can be closed.

[0072] The reason why nitrogen is introduced into the corrosive solution 22 is to deoxygenate the corrosive solution 22 ; the reason why carbon dioxide is introduced into the corrosive solution 22 is to simulate the carbon dioxide gas content in the oil and natural gas pipeline.

[0073] The test tank 3 includes a tank body and a tank cover. The tank body is barrel-shaped, and the tank cover is sealed at the barrel mouth of the tank body. The tank cover can be arranged at the barrel mouth of the tank body by a screw connection or by an interference fit. In order to enhance the sealing performance of the test tank 3, a sealing ring can be arranged between the tank cover and the barrel mouth of the tank body.

[0074] The tank cover is provided with an air inlet for passing through the first air pipe 14, an air outlet for passing through the fourth air pipe 18, a first wire port for passing through the working electrode wire 15, a second wire port for passing through the reference electrode wire 16, and a third wire port for passing through the auxiliary electrode wire 17. The first air pipe 14 passes through the air inlet on the tank cover in a sealed manner, such as a sealing ring is provided between the first air pipe 14 and the air inlet. Similarly, the fourth air pipe 18 also passes through the air outlet of the tank cover in the sealed manner, and the three electrode wires also pass through their respective wire ports in the sealed manner.

[0075] In order to conveniently inject the corrosion solution 22 into the test tank 3, a liquid injection port can be provided on the tank cover of the test tank 3. The liquid injection port is usually sealed by a plug. When the liquid is injected, the plug is pulled out and the corrosion solution 22 can be injected into the test tank 3 through the liquid injection port.

[0076] The working electrode 4, the reference electrode 6 and the auxiliary electrode 5 form a three-electrode system, and its working principle belongs to the prior art and will not be described in detail. If the working electrode 4, the reference electrode 6 or the auxiliary electrode 5 is too heavy, it can be installed in the test tank 3 by a bracket made of polytetrafluoroethylene material.

[0077] The carbon steel 25 in the working electrode 4 is a square plate with a size of 10 mm×10 mm×3 mm, and the material of the support platform 21 is epoxy resin. Of course, a mixed material of epoxy resin, dibutyl phthalate and ethylenediamine can also be used, and the mass ratio of the three is 100 g epoxy resin: 10 g dibutyl phthalate: 7 g ethylenediamine. The copper wire connected to the non-test surface of the carbon steel 25 is the working electrode wire 15, which is connected to the electrochemical workstation 8.

[0078] like Figure 3 As shown, the retaining ring 20 is a polytetrafluoro ring, and the retaining ring 20 is mounted on the outer peripheral wall of one end of the bearing surface of the supporting platform 21 by interference fit. A solid phase particle layer 24, that is, a sand scale layer (sand particles or corrosion scale, silica particles with a particle size of 1 mm) is laid on the test surface of the carbon steel 25 inside the retaining ring 20, and the molecular sieve plate 23 is installed inside the retaining ring 20 and abutted against the solid phase particle layer 24. In this way, the solid phase particle layer 24 is fixed on the test surface of the carbon steel 25 by the retaining ring 20 and the molecular sieve plate 23.

[0079] When the thickness of the solid phase particle layer 24 needs to be adjusted, first move the position of the retaining ring 20 on the supporting platform 21, that is, move the retaining ring 20 a certain distance away from / close to the supporting surface, so that the retaining ring 20 can accommodate a thicker / thinner solid phase particle layer 24, and then install the molecular sieve plate 23 in the retaining ring 20.

[0080] In addition to adjusting the thickness of the solid phase particle layer 24, the area of ​​the solid phase particle layer 24 covering the test surface of the carbon steel 25 can also be adjusted, for example, only half of the solid phase particle layer 24 is covered on the test surface of the carbon steel 25, such as Figure 4 As shown, a solid phase particle layer 24 is laid on the left half of the test surface of the carbon steel 25, and correspondingly, a semicircular protrusion is provided on the right half of the lower side of the molecular sieve plate 23, and the thickness of the semicircular protrusion is the same as the thickness of the solid phase particle layer 24. In this way, after the molecular sieve plate 23 is installed inside the retaining ring 20, the left half of the lower side of the molecular sieve plate 23 is in contact with the solid phase particle layer 24, and the semicircular protrusion on the lower side of the molecular sieve plate 23 is in contact with the right half of the test surface of the carbon steel 25 and the right half of the bearing surface, so that the solid phase particle layer 24 fills the semicircular cavity surrounded by the molecular sieve plate 23, the retaining ring 20, the bearing platform 21 and the carbon steel 25. At this time, the solid phase particle layer 24 only covers the left half of the test surface of the carbon steel 25. Of course, the same method can also be used to cover other proportions (such as one third, two thirds, etc.) of the solid phase particle layer 24 only on the test surface of the carbon steel 25.

[0081] The reference electrode 6 is a saturated calomel electrode, which is arranged just above the working electrode 4. The auxiliary electrode 5 is a platinum electrode, which is arranged near the working electrode 4.

[0082] During the manufacturing process of the working electrode 4, after the carbon steel 25 is encapsulated on the supporting platform 21, if the material of the supporting platform 21 is epoxy resin or a mixture of epoxy resin, dibutyl phthalate and ethylenediamine, it is necessary to wait for the above materials to cool and solidify before performing subsequent operations such as polishing on the test surface of the carbon steel 25.

[0083] Since most oil and gas pipelines are made of carbon steel 25, in the present invention, the test sample in the working electrode 4 is also made of carbon steel 25. When preparing the corrosion solution 22, standard chemicals and deionized water are used to prepare the corrosion solution 22. The corrosion solution 22 contains Ca 2+ , Cl - 、SO4 2- , K + 、Na + Mg 2+ and HCO3 - , where Ca 2+ The concentration is 547 mg / L, Cl - The concentration is 13500mg / L, SO42- The concentration of K is 1706 mg / L. + The concentration is 2096 mg / L, Na + The concentration is 15000mg / L, Mg 2+ The concentration is 278mg / L, HCO3 - The concentration is 655mg / L.

[0084] The thickness of the solid phase particle layer 24 on the test surface of the carbon steel 25 can be 1-5 mm, and the mesh number of the molecular sieve plate 23 is 40-70 meshes. As described above, the molecular sieve plate 23 with a suitable mesh number is selected, and the pore size of the molecular sieve plate 23 is smaller than the particle size of the solid phase particles, so that the solid phase particles cannot pass through the molecular sieve plate 23 to enter the corrosion solution 22, thereby fixing the solid phase particles on the test surface of the carbon steel 25, and allowing the solid phase particle layer 24 to be evenly distributed, while the corrosion solution 22 can pass through the molecular sieve plate 23 to enter the test surface of the carbon steel 25 for testing.

[0085] When obtaining the electrochemical impedance spectroscopy curve and the dynamic potentiodynamic polarization curve, the present invention turns on the electrochemical workstation 8 and the computer 9, and operates the computer 9 to set the test parameters such as the open circuit potential, the polarization curve, and the EIS impedance spectrum. After that, the open circuit potential (OCP) is measured for 30 minutes, and the range of the open circuit potential fluctuation is stabilized within ±10mV, and the electrochemical impedance spectroscopy and the dynamic potentiodynamic polarization curve tests are performed in sequence. The electrochemical impedance spectroscopy curve test (EIS) is performed under OCP, the test frequency is 100kHz-10mHz, and the impedance measurement signal is a sine wave with an amplitude of ±10mV. The potential scanning range of the dynamic potentiodynamic polarization curve test is -250mV-250mV (vs.Eocp), and the scanning rate is 0.5mV / s.

[0086] The present invention can study the corrosion mechanism of oil and gas pipelines under solid phase particle deposition conditions by changing parameters such as solid phase particle thickness, area of ​​the test surface covered by the solid phase particle layer 24, solid phase particle type, temperature of the corrosive solution 22, solution composition, pH value, etc.

[0087] The present invention can truly simulate the corrosion environment of solid-phase particle deposition in oil and gas pipelines, and can be used in laboratories to carry out simulation research on solid-phase particle deposition in oil and gas pipelines, and explore the corrosion mechanism of carbon steel 25 under solid-phase particle deposition conditions. It can also be used for the evaluation and screening of added corrosion inhibitors, that is, the test results obtained by the corrosion solution 22 with the corrosion inhibitor added are compared and analyzed with the test results obtained by the corrosion solution 22 without the corrosion inhibitor added, so as to evaluate and screen the corrosion inhibitors.

[0088] The present invention is suitable for the study of the corrosion mechanism of carbon steel 25 and the evaluation of corrosion inhibitors under solid-phase particle deposition conditions. The advantage of the working electrode 4 is that solid deposits such as sand and scale can be fixed on the surface of the carbon steel 25 through the polytetrafluoroethylene ring and the molecular sieve plate 23, which makes up for the lack of electrochemical devices under solid-phase particle deposition conditions. The present invention is simple to operate and easy to install, and can perform electrochemical tests under solid-phase particle deposition conditions, so that the obtained electrochemical test results are more in line with actual conditions. Therefore, the present invention is of great significance to the study of the corrosion mechanism and the evaluation of corrosion inhibitors under solid-phase particle deposition conditions of oil and gas pipelines.

[0089] It should be noted that the directions or positional relationships indicated by terms such as “center”, “up”, “down”, “front”, “back”, “left”, “right”, and “middle” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on the present invention.

[0090] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0091] The embodiments described above are merely descriptions of preferred implementation modes of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A working electrode for simulating the solid-phase particle deposition condition in a pipeline, characterized in that: It includes carbon steel with a test surface, which is encapsulated on a carrier platform made of insulating material, the test surface of the carbon steel is exposed outside the carrier platform, the non-test surface of the carbon steel is connected to one end of the working electrode wire, the other end of the working electrode wire passes through the carrier platform and extends to the outside of the carrier platform, the carrier platform is equipped with a retaining ring made of insulating material, the test surface of the carbon steel is located in the retaining ring, a solid phase particle layer is laid on the test surface of the carbon steel, a molecular sieve plate is provided on the side of the solid phase particle layer away from the carbon steel test surface, and the molecular sieve plate is installed in the retaining ring and abuts against the solid phase particle layer.

2. The working electrode for simulating pipeline solid-phase particle deposition conditions according to claim 1, characterized in that: The supporting platform is cylindrical, the carbon steel is plate-shaped, the two plate surfaces of the carbon steel are respectively a test surface and a non-test surface, the two end surfaces of the supporting platform are respectively a load-bearing surface and a non-load-bearing surface, the carbon steel is encapsulated on the load-bearing surface of the supporting platform, the shape of the retaining ring is a circle that matches the outer peripheral wall of the supporting platform, the retaining ring is mounted on the outer peripheral wall of one end of the load-bearing surface of the supporting platform, the molecular sieve plate is a circle that matches the inner peripheral wall of the retaining ring, and the molecular sieve plate is installed on the inner peripheral wall of the retaining ring.

3. A test device for simulating the solid phase particle deposition condition in a pipeline, characterized in that: A test tank with a sealed arrangement is provided, wherein the working electrode according to any one of claims 1 to 2 is provided in the test tank, and a reference electrode and an auxiliary electrode are also provided in the test tank, wherein the working electrode is connected to an electrochemical workstation outside the test tank via a working electrode wire, the reference electrode is connected to the electrochemical workstation via a reference electrode wire, the auxiliary electrode is connected to the electrochemical workstation via an auxiliary electrode wire, the electrochemical workstation is connected to a computer, and the test tank is connected to a nitrogen cylinder, a carbon dioxide cylinder and an exhaust gas treatment device via air pipes, respectively.

4. The testing device according to claim 3, characterized in that: One end of a first air pipe is provided in the test tank, the other end of the first air pipe passes through the test tank and extends outside the test tank, the other end of the first air pipe is connected to a second air pipe and a third air pipe, the second air pipe is connected to a nitrogen cylinder, the third air pipe is connected to a carbon dioxide cylinder, and the test tank is connected to an exhaust gas treatment device through a fourth air pipe.

5. A test method for simulating the solid phase particle deposition condition in a pipeline, characterized in that: The following steps are involved: Make a working electrode, and put the working electrode, reference electrode and auxiliary electrode into a sealed test tank. Simulate the composition of produced water from the on-site oil field, prepare the corrosion solution, inject the prepared corrosion solution into the test tank and make the liquid level of the corrosion solution higher than the working electrode, reference electrode and auxiliary electrode. Place the test tank in a water bath to keep it warm, and heat the water in the water bath to the required temperature and keep it constant. Connect the test tank to the nitrogen cylinder, carbon dioxide cylinder and waste gas treatment device through air pipes. First, introduce nitrogen into the corrosion solution in the test tank through the nitrogen cylinder to deoxygenate. After deoxygenation, introduce carbon dioxide gas into the corrosion solution in the test tank through the carbon dioxide cylinder until saturation. Let the waste gas generated during the introduction of nitrogen and carbon dioxide gas flow into the waste gas treatment device. Connect the working electrode, reference electrode and auxiliary electrode to the electrochemical workstation, and connect the electrochemical workstation to the computer. Turn on the electrochemical workstation and computer, and obtain the electrochemical impedance spectroscopy curve and potentiodynamic polarization curve as required. After the test is completed, shut down the electrochemical workstation and computer in turn, and clean up and sweep the test equipment.

6. A test method for simulating the solid phase particle deposition condition in a pipeline, characterized in that: The following steps are involved: Make a working electrode, and put the working electrode, reference electrode and auxiliary electrode into a sealed test tank. Simulate the composition of produced water from the on-site oil field, prepare the corrosion solution, then add an appropriate amount of corrosion inhibitor to the prepared corrosion solution, and then inject the corrosion solution into the test tank and make the liquid level of the corrosion solution higher than the working electrode, reference electrode and auxiliary electrode. Place the test tank in a water bath to keep it warm, and heat the water in the water bath to the required temperature and keep it constant. Connect the test tank to the nitrogen cylinder, carbon dioxide cylinder and waste gas treatment device through air pipes. First, introduce nitrogen into the corrosion solution in the test tank through the nitrogen cylinder to deoxygenate. After deoxygenation, introduce carbon dioxide gas into the corrosion solution in the test tank through the carbon dioxide cylinder until saturation. Let the waste gas generated during the introduction of nitrogen and carbon dioxide gas flow into the waste gas treatment device. Connect the working electrode, reference electrode and auxiliary electrode to the electrochemical workstation, and connect the electrochemical workstation to the computer. Turn on the electrochemical workstation and computer, and obtain the electrochemical impedance spectroscopy curve and potentiodynamic polarization curve as required. After the test is completed, shut down the electrochemical workstation and computer in turn, and clean up and sweep the test equipment.

7. The testing method according to claim 5 or 6, characterized in that: The specific steps of making the working electrode are: A plate-shaped carbon steel is manufactured, and the two surfaces of the carbon steel are respectively marked as the test surface and the non-test surface. A copper wire for connecting to the electrochemical workstation is welded on the non-test surface of the carbon steel and encapsulated with an insulating material. During the packaging process, the insulating material is made into a cylindrical carrier platform, and the two end surfaces of the carrier platform are respectively recorded as the load-bearing surface and the non-load-bearing surface. The carbon steel is packaged on the load-bearing surface of the carrier platform and only the test surface of the carbon steel is exposed outside the carrier platform. At the same time, the copper wire passes through the carrier platform and extends outside the carrier platform. The test surface of the carbon steel was polished step by step with 600#, 800# and 1200# water-abrasive sandpaper, then rinsed with deionized water, dehydrated with alcohol, and dried with cold air. Then the carbon steel and the carrier were placed in a dryer for later use. Use insulating material to make a retaining ring that matches the outer wall of the carrier platform. Take the carbon steel and the carrier platform out of the dryer, and put the retaining ring on the outer wall of one end of the carrier surface of the carrier platform, and let the test surface of the carbon steel be located in the retaining ring. Then lay a solid phase particle layer of the required thickness on the test surface of the carbon steel. A molecular sieve plate with a suitable mesh size that matches the inner wall of the retaining ring is made, and the molecular sieve plate is installed in the retaining ring and abuts against the solid phase particle layer, so that the corrosive solution can pass through the molecular sieve plate and contact the test surface of the carbon steel, while the solid phase particles cannot pass through the molecular sieve plate and enter the corrosive solution. Thus, a working electrode was prepared.

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