Testing system and determining method for minimum cathode protection potential of buried pipeline

Abstract

The invention discloses a testing system and a determining method for the minimum cathode protection potential of a buried pipeline. The system comprises a pipeline and soil environment reduction device, an in-pipe medium temperature reduction device, a soil temperature and humidity reduction device, a cathode protection system function device and a potential test function device, and the pipeline and soil environment reduction device comprises a steel pipe and a soil box. The in-pipe medium temperature reduction device comprises a first water supply device and a first water passing pipeline which form a first water circulation channel, the soil temperature and humidity reduction device comprises a second water supply device and a second water passing pipeline which form a second water circulation channel, and the cathode protection system function device comprises a power supply and an anode bar. The anode bar and the steel pipe are respectively connected with a power supply anode and cathode; the potential testing function device comprises a potential tester and a reference electrode, the steel pipe and the reference electrode are connected with the positive end and the negative end of the potential tester respectively, and the system is used for testing the minimum cathode protection potential of the pipeline. And the minimum cathode protection potential of the pipeline can be accurately tested.

Description

Technical Field

[0001] The present invention relates to the technical field of corrosion and protection in oil and gas field surface engineering, and particularly relates to a test system and determination method for the minimum cathodic protection potential of buried pipelines. Background Art

[0002] The buried pipelines in oil and gas fields generally use seamless carbon steel pipes or low-alloy steel pipes. Although the minimum protection potential indexes for cathodic protection of carbon steel and low-alloy steel are specified in the existing national standards, in the actual production process of oil and gas fields, due to the temperature difference inside and outside the buried pipelines, it is impossible to accurately determine the minimum cathodic protection potential of the pipelines with temperature difference inside and outside according to the current standards. At present, the existing technologies for testing the minimum cathodic protection potential of pipelines cannot simulate the environmental conditions of temperature difference inside and outside the pipelines, and the experimental environment is easily affected, resulting in inaccurate test results. Based on this, there is an urgent need for a system or method that can accurately test the minimum cathodic protection potential of buried pipelines under the environmental conditions of temperature difference inside and outside the pipelines. Summary of the Invention

[0003] Most of the buried pipelines in oil and gas fields use seamless carbon steel pipes or low-alloy steel pipes. For carbon steel and low-alloy steel, the minimum protection potential indexes for cathodic protection of carbon steel and low-alloy steel in the current national standard GB / T21448-2017 "Technical Specification for Cathodic Protection of Buried Steel Pipelines" are as follows: 1) When the ambient temperature is lower than 40°C, the minimum protection potential is -0.85V; 2) When the ambient temperature is higher than 60°C, the minimum protection potential is -0.95V; 3) For the ambient temperature of 40 to 60°C, linear conversion is adopted; currently, the standard for determining the minimum cathodic protection potential is the minimum protection potential corresponding to the ambient temperature for cathodic protection, which is applicable to the case of normal temperature (for example, the temperature of the medium inside the pipe is between 20 and 40°C) transportation of the medium inside the pipe. However, in the actual oilfield production process, there is a temperature difference between the inside and outside of the steel pipe. For the determination of the minimum cathodic protection potential required under the environmental conditions of temperature difference between the inside and outside of the steel pipe, the results obtained by implementing the current standard are not accurate and should be determined by the method of simulation experiment testing. However, the existing simulation experiment testing methods for determining the minimum cathodic protection potential cannot simulate the actual operating conditions of low ambient temperature outside the pipeline and relatively high temperature of the medium inside the pipeline, nor can they simulate the realistic environmental conditions of soil compaction degree and bacterial oxidation-reduction effect, and the experimental environment is unstable. In view of the above problems, the present invention is proposed to provide a test system and determination method for the minimum cathodic protection potential of buried pipelines that can overcome the above problems or at least partially solve the above problems.

[0004] In a first aspect, an embodiment of the present invention provides a test system for the minimum cathodic protection potential of a buried pipeline, including: a pipeline and soil environment restoration device, an in-pipe medium temperature restoration device, a soil temperature and humidity restoration device, a cathodic protection system function device, and a potential test function device;

[0005] The pipeline and soil environment restoration device includes a steel pipe and a soil box. The soil box is used to place soil, and the steel pipe is used to be buried in the soil;

[0006] The in-pipe medium temperature restoration device includes a first water supply device and a first water pipe path. The first water supply device, the first water pipe path and the steel pipe are connected to form a first water circulation path. The first water supply device is used to supply water with a preset temperature into the steel pipe and keep the inside of the steel pipe within a preset temperature range;

[0007] The soil temperature and humidity restoration device includes a second water supply device and a second water pipe path. The second water supply device, the water outlet of the second water pipe path and the water inlet of the second water pipe path are connected to form a second water circulation path. A part of the pipe body of the second water pipe path is used to be buried in the soil. The second water supply device is used to supply water with a preset temperature into the second water pipe path to keep the soil within a preset temperature range;

[0008] The cathodic protection system functional device includes a power supply and an anode rod. The steel pipe is connected to the negative pole of the power supply, and the anode rod is connected to the positive pole of the power supply. The anode rod is used to be buried in the soil;

[0009] The potential testing functional device includes a potential tester and a reference electrode. The steel pipe and the reference electrode are respectively connected to the positive and negative terminals of the potential tester. The potential tester is used to test the off - power protection potential or on - power protection potential of the steel pipe.

[0010] In one embodiment, the first water pipe path includes a water inlet pipe and a water outlet pipe;

[0011] Both ends of the water inlet pipe are respectively connected to one end of the steel pipe and the first water supply device;

[0012] Both ends of the water outlet pipe are respectively connected to the other end of the steel pipe and the first water supply device.

[0013] In one embodiment, the first water supply device includes a first water bucket, a first heating rod, a first water pump, a first temperature sensor and a second temperature sensor;

[0014] The first water bucket is respectively connected to one end of the water outlet pipe and one end of the water inlet pipe;

[0015] The first water pump is arranged on the water inlet pipe;

[0016] The first heating rod is arranged on the water inlet pipe or the water outlet pipe;

[0017] The first temperature sensor is arranged in the first water bucket;

[0018] The second temperature sensor is disposed on the outer wall of the steel pipe.

[0019] In one embodiment, the second water supply device includes: a second water bucket, a second heating rod, a second water pump, a third temperature sensor, and a fourth temperature sensor;

[0020] The second water bucket is connected to the water outlet and the water inlet of the second water pipe;

[0021] The second water bucket is respectively connected to the water outlet and the water inlet of the second water pipe;

[0022] The second water pump and the second heating rod are both disposed on the second water pipe;

[0023] The third temperature sensor is disposed in the second water bucket;

[0024] The fourth temperature sensor is disposed in the soil.

[0025] In a second aspect, an embodiment of the present invention provides a method for determining the minimum cathodic protection potential of a buried pipeline. The method is implemented by the above-mentioned test device for the minimum cathodic protection potential of a buried pipeline, and includes:

[0026] Turn on the power supply to polarize the steel pipe, and turn off the power supply after polarization is completed;

[0027] Start the power supply with a preset voltage, record the voltage and current of the power supply and the energized protection potential of the steel pipe, turn off the power supply, and record the off - energized protection potential of the steel pipe;

[0028] Gradually increase the voltage of the power supply to be started with a first amplitude, and record the corresponding voltage, current, the energized protection potential and the off - energized protection potential of the steel pipe each time the power supply is started;

[0029] Determine the minimum cathodic protection potential of the steel pipe according to the voltage, current, the energized protection potential and the off - energized protection potential of the steel pipe recorded each time.

[0030] In one embodiment, the step of turning on the power supply to polarize the steel pipe includes:

[0031] Set the polarization voltage of the power supply so that under the polarization voltage, the off - energized potential of the steel pipe reaches a preset off - energized potential threshold, turn on the power supply, and polarize the pipeline;

[0032] Until the steel pipe reaches a preset condition, turn off the power supply;

[0033] The conditions are as follows: if the error between the increasing power-on protection potential curve and the decreasing power-on protection potential curve of the steel pipe is less than or equal to a preset error threshold, then the polarization treatment of the steel pipe is completed; the increasing power-on protection potential curve is obtained by increasing the voltage in sequence according to a second amplitude within a preset voltage range and turning on the power supply, and recording each voltage value and the corresponding power-on protection potential; and it is plotted based on each voltage value and the corresponding power-on protection potential during the increasing process; the decreasing power-on protection potential curve is obtained by decreasing the voltage in sequence according to the second amplitude within the same voltage range, and recording each voltage value and the corresponding power-on protection potential; and it is plotted based on each voltage and the corresponding power-on protection potential during the decreasing process.

[0034] In one embodiment, determining the minimum cathodic protection potential of the steel pipe according to each recorded voltage, current, the power-on protection potential and the power-off protection potential of the steel pipe includes:

[0035] If the power-off protection potential of the steel pipe does not change for a continuous number of times, then the last recorded power-off protection potential is used as the minimum cathodic protection potential of the steel pipe.

[0036] In one embodiment, before performing the polarization treatment on the steel pipe, initializing the testing device for the minimum cathodic protection potential of the buried pipeline includes:

[0037] Setting the humidity of the soil according to a preset humidity range;

[0038] Setting the pH value of the soil according to a preset pH range;

[0039] Setting the pressure of the soil according to a preset pressure range;

[0040] Starting the first water supply device and the second water supply device of the testing device for the minimum cathodic protection potential of the buried pipeline; so that the temperature inside the steel pipe, the temperature on the surface of the steel pipe, and the soil temperature are respectively maintained within corresponding preset temperature ranges.

[0041] In one embodiment, obtaining the target soil temperature, target soil humidity, target soil pH value, and target soil pressure value in the environment where the pipeline to be tested is located;

[0042] Initializing the testing device for the minimum cathodic protection potential of the buried pipeline according to the target soil temperature, target soil humidity, target soil pH value, and target soil pressure value.

[0043] In a third aspect, an embodiment of the present invention provides a computer storage medium, in which computer-executable instructions are stored, and when the computer-executable instructions are executed by a processor, the method for determining the minimum cathodic protection potential of the buried pipeline as described above is implemented.

[0044] The beneficial effects of the above technical solutions provided by the embodiments of the present invention at least include:

[0045] A test system for the minimum cathodic protection potential of a buried pipeline provided by an embodiment of the present invention includes: a pipeline and soil environment restoration device, an in-pipe medium temperature restoration device, a soil temperature and humidity restoration device, a cathodic protection system function device, and a potential test function device. The pipeline and soil environment restoration device includes a steel pipe and a soil box. Soil is placed in the soil box, and the steel pipe is buried in the soil, which can simulate the actual scenario of a steel pipe deeply buried in the formation. The in-pipe medium temperature restoration device includes a first water supply device and a first water pipe path. The first water supply device, the first water pipe path, and the steel pipe are connected to form a first water circulation path. The first water supply device is used to supply water at a preset temperature into the steel pipe to keep the inside of the steel pipe pipeline at a constant temperature, and can truly restore the temperature state of the steel pipe inside the formation. The temperature and humidity restoration device includes a second water supply device and a second water pipe path. The outlet and the inlet of the second water supply device, the second water pipe path are connected to form a second water circulation path. A part of the pipe body of the second water pipe path is used to be buried in the soil. The second water supply device is used to supply water at a preset temperature into the second water pipe path to keep the soil within a preset temperature range, and can restore the soil environmental state around the steel pipe in the formation environment where the steel pipe is located in reality. The cathodic protection system function device includes a power supply and an anode rod. The steel pipe is connected to the negative electrode of the power supply, and the anode rod is connected to the positive electrode of the power supply. The anode rod is used to be buried in the soil. The potential test function device includes a potential tester and a reference electrode. The steel pipe and the reference electrode are respectively connected to the positive and negative terminals of the potential tester. The potential tester is used to test the off-power protection potential or on-power protection potential of the steel pipe. The test system for the minimum cathodic protection potential of a buried pipeline can simulate the actual operation situation where the external environment temperature of the steel pipe pipeline is low and the in-pipe medium is relatively high temperature, and the stability of the simulated test environment is higher.

[0046] A method for determining the minimum cathodic protection potential of a buried pipeline provided by an embodiment of the present invention is realized by the above test system for the minimum cathodic protection potential of a buried pipeline. The power supply is turned on to polarize the steel pipe, and the power supply is turned off after polarization is completed; the power supply is started again with a preset voltage, the voltage and current of the power supply and the on-power protection potential of the steel pipe are recorded, the power supply is turned off, and the off-power protection potential of the steel pipe is recorded; the voltage of the power supply is gradually increased in a first amplitude, and the corresponding voltage, current, on-power protection potential, and off-power protection potential of the steel pipe after each start of the power supply are recorded; according to the voltage, current, on-power protection potential, and off-power protection potential recorded each time, the minimum cathodic protection potential of the steel pipe is determined. Compared with the existing method for determining the minimum protection potential by using a slope extrapolation line, the method for determining the minimum cathodic protection potential of a buried pipeline provided in this embodiment overcomes the influence of unstable test simulation environment on data selection and improves the accuracy of test results.

[0047] Other features and advantages of the present invention will be set forth in the following description, and in part will be obvious from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention may be realized and attained by the structure particularly pointed out in the written description, claims, as well as the drawings.

[0048] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The drawings are provided to further understand the present invention, and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0050] Figure 1 is a schematic structural diagram of a test system for the minimum cathodic protection potential of buried pipelines in an embodiment of the present invention;

[0051] Figure 2 is a schematic structural diagram of a pipeline in an embodiment of the present invention;

[0052] Figure 3 is a schematic structural diagram of a second water pipe line in an embodiment of the present invention;

[0053] Figure 4 is a flowchart of a method for determining the minimum cathodic protection potential of buried pipelines in an embodiment of the present invention;

[0054] Figure 5 is one of the curves of the output voltage and current of the power supply, the energized potential and the de-energized potential of the steel pipe in an embodiment of the present invention;

[0055] Figure 6 is another curve of the output voltage and current of the power supply, the energized potential and the de-energized potential of the steel pipe in an embodiment of the present invention;

[0056] Figure 7 is the Tafel curve in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0057] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be completely conveyed to those skilled in the art.

[0058] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0059] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", "connected" 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 directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0060] In order to solve the problem in the prior art that the minimum cathodic protection potential of buried pipelines cannot be accurately measured, the embodiments of the present invention provide a test system and a determination method for the minimum cathodic protection potential of buried pipelines, which are particularly suitable for the situation where the external environment temperature of the pipeline is low and the medium inside the pipeline is relatively high in temperature.

[0061] Embodiment

[0062] The embodiments of the present invention provide a test system for the minimum cathodic protection potential of buried pipelines, and its structure is as Figure 1 shown, including:

[0063] A pipeline and soil environment restoration device, a temperature restoration device for the medium inside the pipe, a soil temperature and humidity restoration device, a cathodic protection system function device, and a potential test function device;

[0064] The pipeline and soil environment restoration device includes a steel pipe 9 and a soil box 8. The soil box 8 is used to place soil (not marked in the figure), and the steel pipe 9 is used to be buried in the soil;

[0065] The temperature restoration device for the medium inside the pipe includes a first water supply device and a first water pipe line. The first water supply device, the first water pipe line and the steel pipe 9 are connected to form a first water circulation path. The first water supply device is used to supply water with a preset temperature into the steel pipe 9 and keep the inside of the steel pipe 9 within a preset temperature range;

[0066] The soil temperature and humidity restoration device includes a second water supply device and a second water pipe 4. The second water supply device, the water outlet of the second water pipe 4, and the water inlet of the second water pipe 4 are connected to form a second water circulation path. A part of the pipe body of the second water pipe 4 is used to be buried in the soil. The second water supply device is used to supply water at a preset temperature to the second water pipe 4 to keep the soil within a preset temperature range;

[0067] The cathodic protection system functional device includes a power supply 1 and an anode rod 2. The steel pipe 9 is connected to the negative electrode of the power supply 1, and the anode rod 2 is connected to the positive electrode of the power supply 1. The anode rod 2 is used to be buried in the soil;

[0068] The potential test functional device includes a potential tester 10 and a reference electrode 11. The steel pipe 9 and the reference electrode 11 are respectively connected to the positive and negative terminals of the potential tester 10. The potential tester 10 is used to test the off - power protection potential or on - power protection potential of the steel pipe 9.

[0069] Buried pipelines in oil and gas fields generally use seamless carbon steel pipes or low - alloy steel pipes. In the formation, it is easy to have a situation where the temperature of the medium inside the pipeline is inconsistent with the temperature of the pipeline surface. Refer to Figure 2 as shown. Figure 2 In the upper pipeline cross - section schematic diagram shown, it represents a pipeline with a relatively low - temperature medium. That is, the pipeline surface is accelerated in electrochemical corrosion due to the increase in environmental temperature, and the internal flowing low - temperature medium promotes the heat dissipation of the pipeline body. The pipeline body is in a relatively low - temperature state from the inside out. In other words, the temperature of the medium inside the pipeline is lower than the temperature of the pipeline surface. In the actual production process of oil fields, gathering and transportation pipelines need to transport the medium at a high temperature (for example, the transportation temperature range is 50 - 80 degrees Celsius) and adopt thermal insulation process technology, which is likely to cause both the pipeline body and the surface to be in a high - temperature state. And after the local thermal insulation layer and surface anti - corrosion layer are damaged and water enters, a local high - temperature primary battery is formed. This forms a pipeline with a relatively high - temperature medium. Refer to Figure 2 In the lower pipeline cross - section schematic diagram shown, that is, the high - temperature transportation of the medium causes the pipeline body to be in a high - temperature state from the inside out, while the natural environmental temperature of the soil where the pipeline is buried is 20 - 30 °C (relatively low temperature). The exposed pipeline surface is in a high - temperature state under the combined action of the internal and external temperature difference and the thermal insulation layer. The existing simulation experimental test methods for determining the minimum cathodic protection potential cannot simulate the actual operating conditions where there is a temperature difference between the inside and outside of the pipeline, nor can they simulate the real environmental conditions of soil compaction and bacterial oxidation - reduction. Moreover, the experimental environment is unstable. The buried pipeline minimum cathodic protection potential test system provided by the embodiments of the present invention can simulate the scenario where the actual steel pipe 9 is deeply buried in the formation, truly restore the temperature state of the steel pipe 9 inside the formation, restore the surrounding soil environmental state in the formation environment where the steel pipe 9 is located, can simulate the actual operating conditions where the temperature of the external environment of the steel pipe 9 is low and the medium inside the pipeline is relatively high, and the stability of the simulated test environment is higher.

[0070] At present, the indicators for determining the simulated experimental environment and testing the minimum cathodic protection potential are as follows: 1) Use a potentiostat or an electrochemical workstation to build an indoor cathodic protection system using a three-electrode test method; 2) Electrolyte environment: Depending on the configuration of the soil solution, or taking soil, drying it, and then adjusting the humidity by adding water and adjusting the environmental temperature with a constant temperature water bath and other devices to carry out the test of the minimum cathodic protection potential under different temperature conditions indoors; 3) The evaluation method uses the polarization curve method in combination with coupon or hanging coupon weighing to verify and determine the minimum cathodic protection potential. However, the results of the minimum cathodic protection potential of buried pipelines measured using the above indicators have the following problems: 1) The coupons or pipe fittings used in the three-electrode test method are heated by the balanced environmental temperature and cannot represent the actual operating conditions where the external environment temperature of the pipeline is low and the medium inside the pipeline is relatively high; 2) The electrolyte environment cannot fully simulate the soil compaction and the actual environmental conditions of bacterial oxidation-reduction reactions; 3) The polarization curve method adopted in the above method determines the minimum protection potential using the slope extrapolation line. The selection of data points and the data source depend on the stability of the test simulation environment, which will directly affect the accuracy of the minimum protection potential value.

[0071] In some alternative embodiments, for the steel pipe 9 used in the test system for the minimum cathodic protection potential of buried pipelines, the production pipeline steel pipe 9 or the steel pipe 9 of the same material is adopted. An anti-corrosion and insulation layer is simulated on the surface of the steel pipe 9. For example, tape anti-corrosion can be used, or epoxy primer and insulation layer can be used together for anti-corrosion. Cut a part of the area to keep the pipeline surface exposed to simulate the damage of the pipeline surface anti-corrosion layer. The size of the cut area is determined according to the actual simulation situation, and the embodiments of the present invention do not limit this.

[0072] The soil box 8 can be made of PVC or other insulating materials, and the length, width, and depth dimensions can be set according to the actual situation. Preferably, the length, width, and depth dimensions are 120 cm × 90 cm × 35 cm.

[0073] In some alternative embodiments, the first water pipe includes a water inlet pipe 13 and a water outlet pipe 12;

[0074] Both ends of the water inlet pipe 13 are respectively connected to one end of the steel pipe 9 and the first water supply device;

[0075] Both ends of the water outlet pipe 12 are respectively connected to the other end of the steel pipe 9 and the first water supply device.

[0076] Optionally, the water inlet pipe 13 can be formed by sequentially connecting multiple water pipes, and the water outlet pipe 12 can be formed by sequentially connecting multiple water pipes.

[0077] In some alternative embodiments, the first water supply device includes a first water bucket 17, a first heating rod 15, a first water pump 16, a first temperature sensor 14, and a second temperature sensor 18;

[0078] The first water bucket 17 is respectively connected to one end of the water outlet pipe 12 and one end of the water inlet pipe 13;

[0079] The first water pump 16 is arranged on the water inlet pipe 13;

[0080] The first heating rod 15 is arranged on the water inlet pipe 13 or the water outlet pipe 12;

[0081] The first temperature sensor 14 is arranged inside the first water bucket 17;

[0082] The second temperature sensor 18 is arranged on the outer wall of the steel pipe 9.

[0083] Specifically, one end of the water outlet pipe 12 and one end of the water inlet pipe 13 are respectively connected to both ends of the steel pipe 9, and the other end of the water outlet pipe 12 and the other end of the water inlet pipe 13 are respectively connected to the first water bucket 17, specifically, inserted into the water in the first water bucket 17. The water in the first water bucket 17 is pumped into the pipelines of the water inlet pipe 13, the steel pipe 9 and the water outlet pipe 12 through the first water pump 16 to form a first water circulation path, and the water in the first water circulation path is heated by the first heating rod 15. For example, the first heating rod 15 can be an electric heating rod or other types of heating rods. The heating time is controlled by the temperature signals collected by the first temperature sensor 14 and the second temperature sensor 18. For example, the temperature signals can be collected through a programmable logic controller (PLC control system), or other temperature control technologies can also be selected. The embodiments of the present invention do not limit this, so as to keep the water temperature inside the steel pipe 9 at a constant temperature and the surface temperature of the steel pipe 9 at a constant temperature, so as to simulate the environment of the temperature difference between the inside and outside of the steel pipe 9. There are various choices for temperature sensors, and contact temperature sensors or other types of temperature sensors can be selected, such as infrared temperature sensors; the contact temperature sensor is adopted in the embodiments of the present invention.

[0084] In some alternative embodiments, the second water supply device includes: a second water bucket 7, a second heating rod 3, a second water pump 5, a third temperature sensor 6 and a fourth temperature sensor 19;

[0085] The second water bucket 7 is connected to the water outlet and the water inlet of the second water pipe 4;

[0086] The second water bucket 7 is respectively connected to the water outlet and the water inlet of the second water pipe 4;

[0087] Both the second water pump 5 and the second heating rod 3 are arranged on the second water pipe 4;

[0088] The third temperature sensor 6 is arranged inside the second water bucket 7;

[0089] The fourth temperature sensor 19 is arranged in the soil.

[0090] Among them, the second water pipe path 4 can be formed by sequentially connecting multiple water pipes. The two ends of the second water pipe path 4 are respectively a water outlet and a water inlet, and the water outlet and the water inlet are respectively inserted into the water in the first water bucket 17. The water in the second water bucket 7 is pumped into the second water pipe path 4 by the second water pump 5 to form a second water circulation path. The water in the second water circulation path is heated by the second heating rod 3, and the heating time is controlled by the temperature signals of the third temperature sensor 6 and the fourth temperature sensor collected, so as to keep the soil temperature during the test consistent with the soil temperature at the target area site.

[0091] When the soil in the soil box 8 is relatively thick or the environmental temperature requirement is relatively high, in order to make the soil in the soil box 8 heat more evenly to ensure the accuracy of the test results, the second water pipe path as shown in Figure 3 can be adopted.

[0092] In order to further eliminate the influence of soil reasons on the accuracy of the test results, the soil collected and placed in the soil box 8 uses the soil with the buried depth of the pipeline at the target area site to ensure consistency with the target area site environment and restore the soil environment where the production pipeline is located. In addition, according to the humidity, PH, and compaction degree values of the soil with the buried depth of the pipeline at the target area site, the humidity, PH value, and compaction degree value of the soil in the soil box 8 are set. For example, a direct insertion type soil multi-parameter tester is used to detect the soil humidity with the buried depth of the pipeline in the target area, and the on-site groundwater is slowly sprayed into the soil box 8 to keep the soil in the soil box 8 moist. At the same time, a soil parameter tester is used to maintain the soil PH with the buried depth of the pipeline in the test target area.

[0093] In addition, it is necessary to simulate the soil compaction degree with the buried depth of the pipeline in the target area. Specifically, during the test, after the steel pipe 9 is buried, the soil is slowly compacted. After the soil is compacted, the soil near the test steel pipe 9 is taken through a soil sampler, and the soil with a preset volume is cut and weighed. If the weight ratio to the soil with the same volume and the buried depth of the pipeline at the target area site is greater than the preset ratio, it means that the compaction degree in the soil box 8 is qualified. For example, 27 cubic centimeters of soil near the test steel pipe 9 is taken, and the soil with the same volume and the buried depth of the pipeline at the target area site is taken. If the weight ratio of the two exceeds 90%, it means that the soil compaction degree in the soil box 8 is qualified.

[0094] The potential test function device is used to test the on - power potential and off - power potential to simulate the potential test function of the production pipeline. There are various choices for the reference electrode 11. For example, a copper sulfate reference electrode 11 or a silver chloride reference electrode 11 can be used. For the accuracy of the test results, the distance between the connection point of the positive terminal of the potential tester 10 and the steel pipe 9 and the connection point of the negative terminal of the DC power supply 1 and the steel pipe 9 is greater than or equal to the preset distance threshold, for example, greater than or equal to 10 centimeters.

[0095] Based on the same inventive concept, an embodiment of the present invention further provides a method for determining the minimum cathodic protection potential of a buried pipeline. This method is implemented by the aforementioned test device for the minimum cathodic protection potential of a buried pipeline, and its process is as follows Figure 4 shown, including the following steps:

[0096] Step S41: Turn on power supply 1 to polarize the steel pipe 9, and turn off power supply 1 after polarization is completed;

[0097] Step S42: Start power supply 1 with a preset voltage amplitude, record the voltage, current of power supply 1 and the energized protection potential of the steel pipe 9, turn off power supply 1, and record the off - energized protection potential of the steel pipe 9;

[0098] Step S43: Gradually increase the voltage of power supply 1 in a first amplitude, and record the corresponding voltage, current, energized protection potential and off - energized protection potential of the steel pipe 9 each time power supply 1 is started;

[0099] Step S44: Determine the minimum cathodic protection potential of the steel pipe 9 according to the voltage, current, energized protection potential and off - energized protection potential recorded each time.

[0100] In some alternative embodiments, before polarizing the steel pipe 9, the steel pipe 9 is initialized in the following manner:

[0101] Set the humidity of the soil according to a preset humidity range;

[0102] Set the pH value of the soil according to a preset pH range;

[0103] Set the pressure of the soil according to a preset pressure range;

[0104] Start the first water supply device and the second water supply device of the test device for the minimum cathodic protection potential of the buried pipeline; so that the temperature inside the steel pipe 9, the temperature on the surface of the steel pipe 9 and the soil temperature are respectively maintained within the corresponding preset temperature ranges.

[0105] For example, start the first water supply device and the second water supply device, and use a PLC control system to keep the water temperature in the test steel pipe 9 at the temperature of the soil at the buried depth of the target area pipeline, for example, keep it at 55°C; keep the temperature on the surface of the steel pipe 9 constant at a preset temperature, for example, constant at 50°C; use a PLC control system to keep the temperature in the soil heating pipeline the same as the temperature of the soil at the buried depth of the target area pipeline, for example, keep it at 25°C.

[0106] In some alternative embodiments, in the above - mentioned step S41, the steel pipe 9 is polarized in the following manner:

[0107] Set the polarization voltage of power supply 1 so that under the polarization voltage, the off - state potential of steel pipe 9 reaches a preset off - state potential threshold. Turn on power supply 1 and perform polarization treatment on the pipeline;

[0108] Until the steel pipe 9 meets the preset conditions, turn off power supply 1;

[0109] The conditions are as follows: the error between the increasing energized protection potential curve and the decreasing energized protection potential curve of steel pipe 9 is less than or equal to a preset error threshold, then the polarization treatment of steel pipe 9 is completed; the increasing energized protection potential curve is obtained by increasing the voltage in sequence according to the second amplitude within a preset voltage range and turning on power supply 1, and recording each voltage value and the corresponding energized protection potential; the decreasing energized protection potential curve is obtained by decreasing the voltage in sequence according to the second amplitude within the same voltage range, and recording each voltage value and the corresponding energized protection potential.

[0110] Set the off - state potential to - 1.2V, start power supply 1 (for example, select a DC power supply) to perform cathodic polarization on steel pipe 9 for a period of time, and the polarization time exceeds 24 hours. During the polarization period, maintain the soil temperature and humidity in soil box 8 and the water circulation temperature in the pipe.

[0111] The increasing energized protection potential curve is obtained by the following method:

[0112] Start the DC power supply 1 from the preset polarization start voltage, increase the output voltage of the DC power supply 1 in sequence according to the second amplitude until the voltage of the DC power supply 1 is increased to the off - state protection potential of - 1.2V and then stop (for example, at this time, the voltage of the corresponding DC power supply 1 is 7V). Record the output voltage of the DC power supply 1 and the corresponding energized protection potential in each increasing state. Take a specific example to illustrate: start the DC power supply 1 from 0V, record the output voltage VZ0 of the DC power supply 1 at this time and the corresponding energized protection potential VZt0, increase the output voltage of power supply 1 by 0.5V successively, and record the output voltage of the DC power supply 1 and the corresponding energized protection potential in each increasing state [VZ0.5, VZt0.5], [VZ1, VZt1], [VZ1.5, VZt1.5]…[VZ7, VZt7]. Draw the increasing energized protection potential curve according to the output voltage value of the DC power supply 1 and the corresponding energized protection potential value in each group.

[0113] The decreasing energized protection potential curve is obtained by the following method:

[0114] Starting from 7V, gradually decrease the output voltage of the DC power supply 1 in the second amplitude until the voltage of the DC power supply 1 is decreased to 0V and then stop. Record the output voltage of the DC power supply 1 and the corresponding energized protection potentials [VJ7, VJt7], [VJ6.5, VJt6.5], [VJ6, VJt6]... [VJ0, VJt0] under each decreasing state. According to the output voltage value of the DC power supply 1 and the corresponding energized protection potential value in each group, draw a decreasing energized protection potential curve.

[0115] If the decreasing energized protection potential curve coincides with the increasing energized protection potential curve, it proves that the polarization treatment is completed.

[0116] It can also be judged whether the planned treatment is completed by calculation. By calculating the absolute difference between the increasing energized protection potential and the decreasing energized protection potential corresponding to the output voltage of the same DC power supply 1, and judging whether the absolute difference is less than the preset difference threshold. If so, it proves that the polarization treatment is completed. For example, △VT0.5 = |VZt0.5 - VJt0.5|. If △VT0.5 ≤ 0.1 * Vt0.5, the polarization treatment is completed.

[0117] If the condition for terminating the plan is not met, continue to maintain polarization for a period of time until the energized and de-energized protection potential differences corresponding to the increase and decrease meet the requirements, and then start the next step. The preferred polarization time can be greater than 24 hours and not exceed 72 hours.

[0118] In some alternative embodiments, after the polarization treatment is completed, perform the above step S42. For example, the output voltage of the DC power supply 1 is started from 0V, and the voltage, current of the power supply 1 and the energized protection potential of the steel pipe 9 are recorded at this time. Keep the power on for a period of time, preferably 12 seconds. Then turn off the DC power supply 1 and power off for a period of time, preferably 3 seconds. Record the corresponding de-energized protection potential at the moment of power off.

[0119] Gradually increase the output voltage of the DC power supply 1 in the first amplitude, and record the voltage, current, energized protection potential of the power supply 1 each time and the corresponding de-energized protection potential. According to the voltage, current, energized protection potential of the power supply 1 each time and the corresponding de-energized protection potential value, draw a curve of the output voltage and current of the power supply 1 and the energized and de-energized potential data of the test steel pipe 9. Refer to Figure 5 as shown. Figure 5 The stable section value of the de-energized potential is the minimum cathodic protection potential of the test steel pipe 9 under the current medium temperature in the pipe and soil temperature conditions.

[0120] To more clearly illustrate the curve of the output voltage and current of the power supply 1 and the energized and de-energized potentials of the steel pipe 9, refer to Figure 6 as shown. Figure 6The upper part in the figure shows the changing trends of the output voltage and current of the power supply 1. Among them, the output voltage gradually increases, and the current also gradually increases. Figure 6 The upper part in the figure shows the changing trends of the energized potential and the de-energized potential of the steel pipe 9. Among them, as the output voltage increases, the energized potential gradually increases, while the de-energized potential tends to be stable. The breakpoint voltage in the stable state is the value of the minimum cathodic protection potential of the experimental steel pipe 9 under the current medium temperature and soil temperature conditions. Refer to Figure 6 As shown, the minimum cathodic protection potential of the pipeline is -1.09V.

[0121] Taking the minimum cathodic protection potential of the pipeline calculated by the Tafel curve (i.e., the logarithmic curve of the power supply output voltage and current) as a comparison, refer to Figure 7 The drawn Tafel curve. The intersection point of the slopes of the Tafel curve is the minimum cathodic protection potential of the test steel pipe 9 under the current conditions. When the voltage of the power supply 1 is 2V, the energized protection potential of the experimental steel pipe 9 is about 1.4V, and the de-energized protection potential is 1.02V. By comparison, it is found that the method for determining the minimum cathodic protection potential of the buried pipeline provided by the embodiment of the present invention can more accurately obtain the minimum cathodic protection potential of the steel pipe 9 pipeline.

[0122] In some alternative embodiments, the temperature of the soil in the soil box 8 and the temperature of the medium in the steel pipe 9 can be changed by adjusting the water temperature, and steps S41 - S44 are repeatedly executed to obtain the simulation test results of different pipeline internal medium temperatures under different soil temperature conditions.

[0123] In some alternative embodiments, the area of the exposed cut of the pipeline can be changed, and steps S41 - S44 are repeatedly executed to obtain the test results of the minimum cathodic protection potential of the pipeline at different exposed areas.

[0124] Unless otherwise specifically stated, terms such as processing, calculating, operating, determining, displaying, etc. can refer to the actions and / or processes of one or more processing or computing systems, or similar devices, and the actions and / or processes will represent the data operation and conversion of physical (such as electronic) quantities in the registers or memories of the processing system into other data that are similarly represented as physical quantities in the memories, registers, or other such information storage, transmission, or display devices of the processing system. Information and signals can be represented using any of a variety of different technologies and methods. For example, the data, instructions, commands, information, signals, bits, symbols, and chips mentioned throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0125] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of the present disclosure. The appended method claims present the elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy recited.

[0126] In the foregoing detailed description, various features are combined in a single embodiment to simplify the present disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are expressly recited in each claim. Rather, as reflected by the appended claims, the invention lies in less than all of the features of a single disclosed embodiment. Thus, the appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0127] The above description includes examples of one or more embodiments. Of course, it is not possible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but those of ordinary skill in the art should recognize that the various embodiments can be further combined and arranged. Accordingly, the embodiments described herein are intended to embrace all such changes, modifications, and variations that fall within the scope of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, this term is inclusive in a manner similar to the term "including" as interpreted when used as a transitional word in a claim. Further, any use of the term "or" in the claims or specification is to mean "non-exclusive or".

Claims

1. A test system for the minimum cathodic protection potential of buried pipelines, characterized in that, it includes: a pipeline and soil environment restoration device, an in-pipeline medium temperature restoration device, a soil temperature and humidity restoration device, a cathodic protection system function device, and a potential test function device; The pipeline and soil environment restoration device includes a steel pipe and a soil box. The soil box is used to place soil, and the steel pipe is used to be buried in the soil; The in-pipeline medium temperature restoration device includes a first water supply device and a first water pipe path. The first water supply device, the first water pipe path, and the steel pipe are connected to form a first water circulation path. The first water supply device is used to supply water at a preset temperature into the steel pipe and keep the inside of the steel pipe within a preset temperature range; The soil temperature and humidity restoration device includes a second water supply device and a second water pipe path. The second water supply device, the water outlet of the second water pipe path, and the water inlet of the second water pipe path are connected to form a second water circulation path. A part of the pipe body of the second water pipe path is used to be buried in the soil. The second water supply device is used to supply water at a preset temperature into the second water pipe path to keep the soil within a preset temperature range; The cathodic protection system function device includes a power supply and an anode rod. The steel pipe is connected to the negative electrode of the power supply, and the anode rod is connected to the positive electrode of the power supply. The anode rod is used to be buried in the soil; The potential test function device includes a potential tester and a reference electrode. The steel pipe and the reference electrode are respectively connected to the positive and negative terminals of the potential tester. The potential tester is used to test the off - power protection potential or on - power protection potential of the steel pipe.

2. The test system for the minimum cathodic protection potential of buried pipelines according to claim 1, characterized in that, the first water pipe path includes a water inlet pipe and a water outlet pipe; Both ends of the water inlet pipe are respectively connected to one end of the steel pipe and the first water supply device; Both ends of the water outlet pipe are respectively connected to the other end of the steel pipe and the first water supply device.

3. The test system for the minimum cathodic protection potential of buried pipelines according to claim 2, characterized in that, the first water supply device includes a first water bucket, a first heating rod, a first water pump, a first temperature sensor, and a second temperature sensor; The first water bucket is respectively connected to one end of the water outlet pipe and one end of the water inlet pipe; The first water pump is arranged on the water inlet pipe; The first heating rod is arranged on the water inlet pipe or the water outlet pipe; The first temperature sensor is arranged inside the first water bucket; The second temperature sensor is arranged on the outer wall of the steel pipe.

4. The test system for the minimum cathodic protection potential of buried pipelines according to claim 1, characterized in that, the second water supply device includes: a second water bucket, a second heating rod, a second water pump, a third temperature sensor, and a fourth temperature sensor; The second water bucket, the water outlet of the second water pipe path, and the water inlet of the second water pipe path are connected; The second water bucket is respectively connected to the water outlet and the water inlet of the second water pipe path; The second water pump and the second heating rod are both arranged on the second water pipe path; The third temperature sensor is disposed within the second water bucket; The fourth temperature sensor is disposed in the soil.

5. A method for determining the minimum cathodic protection potential of a buried pipeline, the method being implemented by the test device for the minimum cathodic protection potential of a buried pipeline according to any one of claims 1-4, characterized in that, comprising: Turn on the power supply to polarize the steel pipe, and turn off the power supply after polarization is completed; Start the power supply with a voltage of a preset volt, record the voltage and current of the power supply and the energized protection potential of the steel pipe, turn off the power supply, and record the off - energized protection potential of the steel pipe; Gradually increase the voltage of the power supply to start with a first amplitude, and record the corresponding voltage, current, energized protection potential and off - energized protection potential of the steel pipe each time the power supply is started; Determine the minimum cathodic protection potential of the steel pipe according to the voltage, current, energized protection potential and off - energized protection potential of the steel pipe recorded each time.

6. The method for determining the minimum cathodic protection potential of a buried pipeline according to claim 5, characterized in that, The step of turning on the power supply to polarize the steel pipe includes: Set the polarization voltage of the power supply so that under the polarization voltage, the off - energized potential of the steel pipe reaches a preset off - energized potential threshold, turn on the power supply, and polarize the pipeline; Until the steel pipe reaches a preset condition, turn off the power supply; The condition is: the error between the increasing energized protection potential curve and the decreasing energized protection potential curve of the steel pipe is less than or equal to a preset error threshold, then the polarization of the steel pipe is completed; the increasing energized protection potential curve is obtained by successively increasing the voltage within a preset voltage range according to a second amplitude and turning on the power supply, and recording each voltage value and the corresponding energized protection potential; and is plotted according to each voltage value and the corresponding energized protection potential during the increasing process; the decreasing energized protection potential curve is obtained by successively decreasing the voltage within the same voltage range according to the second amplitude, and recording each voltage value and the corresponding energized protection potential; and is plotted according to each voltage and the corresponding energized protection potential during the decreasing process.

7. The method for determining the minimum cathodic protection potential of a buried pipeline according to claim 5, characterized in that, The step of determining the minimum cathodic protection potential of the steel pipe according to the voltage, current, energized protection potential and off - energized protection potential of the steel pipe recorded each time includes: If the off - energized protection potential of the steel pipe does not change for a continuous number of times, then take the off - energized protection potential recorded last time as the minimum cathodic protection potential of the steel pipe.

8. The method for determining the minimum cathodic protection potential of a buried pipeline according to claim 5, characterized in that, Before polarizing the steel pipe, perform an initialization process on the test device for the minimum cathodic protection potential of the buried pipeline, including: Set the humidity of the soil according to a preset humidity range; Set the pH value of the soil according to a preset pH range; Set the pressure of the soil according to a preset pressure range; Start the first water supply device and the second water supply device of the test device for the minimum cathodic protection potential of the buried pipeline; make the temperature inside the steel pipe, the temperature on the surface of the steel pipe, and the soil temperature respectively remain within the corresponding preset temperature ranges.

9. The method for determining the minimum cathodic protection potential of a buried pipeline according to claim 5, characterized in that, it further includes: Obtain the soil target temperature, soil target humidity, soil target pH value, and soil target pressure value in the environment where the pipeline to be tested is located; According to the soil target temperature, soil target humidity, soil target pH value, and soil target pressure value, perform initialization processing on the test device for the minimum cathodic protection potential of the buried pipeline.

10. A computer storage medium, characterized in that, computer-executable instructions are stored in the computer storage medium, and when the computer-executable instructions are executed by a processor, the method for determining the minimum cathodic protection potential of a buried pipeline according to any one of claims 5-9 is implemented.

11. A terminal device, characterized in that, it includes: a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the program, the method for determining the minimum cathodic protection potential of a buried pipeline according to any one of claims 5-9 is implemented.

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