Evaluation method of sheath material for heating insulated cable, sheath material, heating insulated cable and application

Abstract

The invention discloses an evaluation method of a sheath material for a heating insulated cable, the sheath material, the heating insulated cable and application, and the method comprises the steps: carrying out normal-temperature mechanical property test and high-temperature mechanical property test on a sheath raw material based on an actual service condition, and evaluating the normal-temperature mechanical property and the high-temperature mechanical property of the sheath raw material; performing a high-temperature creep property test on the sheath raw material meeting the normal-temperature mechanical property and the high-temperature mechanical property, and evaluating the high-temperature creep property of the sheath raw material; performing a high-temperature and high-pressure corrosion simulation test on the sheath raw material meeting the high-temperature creep property, and evaluating the corrosion allowance of the sheath raw material in a long period; and carrying out high-temperature and high-pressure corrosion simulation test and high-temperature mechanical property test on the sheath raw material meeting the corrosion allowance in a long period so as to comprehensively evaluate the sheath material for the heating insulated cable. According to the method, inapplicable materials can be gradually eliminated, the systematicness is high, and a scientific and objective basis is provided for rapidly determining the material of the sheath material.

Description

Technical Field

[0001] The invention relates to the technical field of sheath material evaluation, and in particular to a sheath material evaluation method for a heating insulation cable, a sheath material, a heating insulation cable and applications. Background Art

[0002] During the in-situ conversion of shale oil, the harsh corrosive environment (such as high temperature, high pressure, corrosive gases such as H2O, CO2, H2S and H2) will cause serious corrosion problems for heating cables. In addition, due to the weight of the cable at a certain length and the squeezing of the cable by the formation pressure when underground, the cable may be deformed and broken, so a layer of sheath material is often made outside the cable to protect the heating cable. Under actual working conditions, the mechanical properties of the sheath material itself, its mechanical properties and corrosion resistance in the working environment, and its mechanical properties after a certain period of service are important criteria for the use of sheath materials. Summary of the invention

[0003] In order to provide theoretical guidance and technical support for the selection of sheath materials for heating insulated cables under complex working conditions, and to solve the current technical problems that the evaluation of sheath materials is not systematic enough, the evaluation means are single; the evaluation is difficult under complex environments; the use of experience judgment is highly subjective and the basis is insufficient; the accuracy of the evaluation results cannot be guaranteed; and to enrich the technical route and increase the selection space, the embodiments of the present invention provide a method for evaluating sheath materials for heating insulated cables, sheath materials, heating insulated cables and applications.

[0004] In a first aspect, an embodiment of the present invention provides a method for evaluating a sheath material for a heating insulation cable, which may include:

[0005] Conducting room temperature mechanical property tests and high temperature mechanical property tests on the raw materials of the sheath based on actual service conditions to evaluate the room temperature mechanical property and high temperature mechanical property of the raw materials of the sheath;

[0006] For the sheath raw materials that meet the normal temperature mechanical properties and high temperature mechanical properties, high temperature creep performance test is carried out to evaluate the high temperature creep performance of the sheath raw materials;

[0007] Conduct high-temperature and high-pressure corrosion simulation tests on sheath raw materials that meet high-temperature creep performance to evaluate the corrosion margin of the sheath raw materials under long-term conditions;

[0008] High-temperature and high-pressure corrosion simulation tests and high-temperature mechanical properties tests are carried out on the sheath raw materials that meet the corrosion margin under long-term conditions, so as to conduct a comprehensive evaluation of the sheath materials for heating insulated cables.

[0009] In one embodiment, a room temperature mechanical property test is performed on the raw material of the jacket based on actual service conditions to evaluate the room temperature mechanical properties of the raw material of the jacket, which may include:

[0010] The raw material of the sheath is flattened and then processed by wire cutting to produce a sample, so that the surface of the sample has no depressions and burrs after processing;

[0011] Use 120 mesh, 360 mesh and 800 mesh sandpaper to polish the sample in sequence to remove the wire cutting marks, and the final polishing marks are consistent with the tensile loading direction of the sample;

[0012] Making an original mark on the surface of the sample, and measuring and recording the length of the original mark;

[0013] Performing a tensile test at room temperature using a high temperature tensile testing machine, and ending the tensile test when the sample is broken;

[0014] Determining the yield strength curve of the sheath raw material at room temperature based on a tensile test;

[0015] Determine the strength requirements of the cable sheath at normal temperature based on the cable weight at the preset depth and the cross-sectional area of ​​the cable sheath material;

[0016] Based on the yield strength curve of the sheath raw material at room temperature and the strength requirements of the cable sheath at room temperature, the room temperature mechanical properties of the sheath raw material are evaluated.

[0017] In another embodiment, the room temperature mechanical properties test is performed on the sheath raw material based on actual service conditions to evaluate the room temperature mechanical properties of the sheath raw material. It can also include: preparing multiple groups of parallel samples of the samples to perform room temperature mechanical properties tests to comprehensively evaluate the room temperature mechanical properties of the sheath raw material.

[0018] In one embodiment, a high temperature mechanical property test is performed on a sheath raw material that meets the normal temperature mechanical properties based on actual service conditions to evaluate the high temperature mechanical properties of the sheath raw material, which may include:

[0019] The raw material of the sheath is flattened and then processed by wire cutting to produce a sample, so that the surface of the sample has no depressions and burrs after processing;

[0020] Use 120 mesh, 360 mesh and 800 mesh sandpaper to polish the sample in sequence to remove the wire cutting marks, and the final polishing marks are consistent with the tensile loading direction of the sample;

[0021] Making an original mark on the surface of the sample, and measuring and recording the length of the original mark;

[0022] Using a high temperature tensile testing machine to heat the tensile region of the sample to the service temperature of the jacket raw material under high temperature conditions to perform a tensile test, and ending the tensile test when the sample is broken;

[0023] Determining the yield strength curve of the sheath raw material under high temperature conditions based on a tensile test;

[0024] Calculating the strength requirement of the jacket raw material under high temperature conditions based on the formation pressure and casing parameters of the jacket raw material when in service;

[0025] Based on the yield strength curve of the sheath raw material under high temperature conditions and the strength requirements of the cable sheath under high temperature conditions, the high temperature mechanical properties of the sheath raw material are evaluated.

[0026] In another embodiment, a high-temperature mechanical property test is performed on the sheath raw material that meets the room-temperature mechanical properties based on actual service conditions to evaluate the high-temperature mechanical properties of the sheath raw material. It may also include: preparing multiple groups of parallel samples of the samples to perform high-temperature mechanical property tests to comprehensively evaluate the high-temperature mechanical properties of the sheath raw material.

[0027] In one embodiment, a high temperature creep performance test is performed on a sheath raw material that meets high temperature mechanical properties to evaluate the high temperature creep performance of the sheath raw material, which may include:

[0028] The raw material of the sheath is flattened and then processed by wire cutting to produce a sample, so that the surface of the sample has no depressions and burrs after processing;

[0029] Use 120 mesh, 360 mesh and 800 mesh sandpaper to polish the sample in sequence to remove the wire cutting marks, and the final polishing marks are consistent with the tensile loading direction of the sample;

[0030] Making an original mark on the surface of the sample, and measuring and recording the length of the original mark;

[0031] Using a high temperature creep endurance tester, the tensile region of the sample is heated to the service temperature of the sheath raw material under high temperature conditions to perform a tensile creep test, and the tensile test is terminated when the sample is broken or the creep time is reached;

[0032] Determining the creep curve of the sheath raw material under high temperature creep conditions based on a tensile test;

[0033] According to the service life of the raw materials of the sheath, the high temperature creep strength requirements of the cable sheath under high temperature conditions are determined;

[0034] Based on the creep curve of the sheath raw material under high temperature creep conditions and the high temperature creep strength requirements of the cable sheath under high temperature conditions, the high temperature creep performance of the sheath raw material is evaluated.

[0035] In another embodiment, a high temperature creep performance test is performed on the sheath raw material that meets the high temperature mechanical properties to evaluate the high temperature creep performance of the sheath raw material. It can also include: preparing multiple groups of parallel samples of the samples to perform high temperature creep performance tests to comprehensively evaluate the high temperature creep performance of the sheath raw material.

[0036] In one embodiment, a high temperature and high pressure corrosion simulation test is performed on a sheath material that meets high temperature creep performance to evaluate the corrosion margin of the sheath material under a long period, which may include:

[0037] The raw material of the sheath is flattened and then processed by wire cutting to produce a sample, so that the surface of the sample has no depressions and burrs after processing;

[0038] The sample was polished with 120-mesh, 360-mesh and 800-mesh sandpaper in sequence to remove the wire cutting marks of the sample, and the surface of the sample was smooth and flat after final polishing;

[0039] Marking the surface of the sample to record the serial numbers of the multiple groups of samples;

[0040] Rinse the specimen with deionized water, dehydrate with anhydrous ethanol, remove oil with acetone, and dry with cold air;

[0041] The sample is measured using a vernier caliper with an accuracy of 0.01 mm and weighed using an electronic balance with an accuracy of 0.1 mg;

[0042] The sample is placed on a corundum burning boat and placed in a high temperature and high pressure reactor;

[0043] Inject a quantitative amount of deionized water into the high temperature and high pressure reactor, into which high purity nitrogen is continuously introduced for no less than 24 hours;

[0044] Continuously introducing high-purity nitrogen into the high-temperature and high-pressure reactor for not less than 6 hours to remove the residual air in the high-temperature and high-pressure reactor;

[0045] At room temperature, a CO2-H2S-H2 mixed gas is introduced into the high temperature and high pressure reactor to make the pressure inside the high temperature and high pressure reactor reach 1.3 MPa;

[0046] The sample is subjected to a 168-hour long-term high-temperature and high-pressure corrosion simulation test;

[0047] After the test, turn off the heating device of the high-temperature and high-pressure reactor, and when the temperature in the high-temperature and high-pressure reactor drops below 60°C, open the exhaust valve of the high-temperature and high-pressure reactor to discharge the gas in the high-temperature and high-pressure reactor to the exhaust gas treatment device;

[0048] After the gas in the high-temperature and high-pressure reactor is exhausted, high-purity nitrogen is continuously introduced into the high-temperature and high-pressure reactor for not less than 30 minutes to remove the harmful gases remaining in the reactor and pipelines of the high-temperature and high-pressure reactor;

[0049] Open the high temperature and high pressure reactor, take out the sample and dry it in a vacuum drying oven at 120° C. for 2 h;

[0050] The test piece was weighed after drying, and the corrosion rate was used to evaluate the corrosion margin of the sheath raw material over a long period of time.

[0051] In one embodiment, a high temperature and high pressure corrosion simulation test and a high temperature mechanical property test are performed on a sheath raw material that meets the corrosion margin under a long period to evaluate the high temperature mechanical properties of the sheath raw material after pre-corrosion, which may include:

[0052] The raw material of the sheath is flattened and then processed by wire cutting to produce a sample, so that the surface of the sample has no depressions and burrs after processing;

[0053] Use 120 mesh, 360 mesh and 800 mesh sandpaper to polish the sample in sequence to remove the wire cutting marks, and the final polishing marks are consistent with the tensile loading direction of the sample;

[0054] Marking the surface of the sample to record the serial numbers of the multiple groups of samples;

[0055] Placing the sample in a high-temperature and high-pressure reactor to conduct a pre-corrosion test according to a high-temperature and high-pressure corrosion simulation test;

[0056] Make an original mark on the surface of the sample after the pre-corrosion test, and measure and record the length of the original mark;

[0057] Using a high temperature tensile testing machine, the tensile region of the sample after the pre-corrosion test is heated to the service temperature of the sheath raw material under high temperature conditions to perform a tensile test, and the tensile test is terminated when the sample is broken;

[0058] Determining the yield strength curve of the sheath raw material under high temperature conditions after pre-corrosion based on a tensile test;

[0059] Based on the yield strength curve of the sheath raw material under high temperature conditions after pre-corrosion and the yield strength curve of the sheath raw material under high temperature conditions without pre-corrosion, the high temperature mechanical properties of the sheath raw material after pre-corrosion are evaluated.

[0060] In a second aspect, an embodiment of the present invention provides a sheath material for a heating insulation cable obtained according to the evaluation method for a sheath material for a heating insulation cable according to the first aspect.

[0061] In a third aspect, an embodiment of the present invention provides a heating insulated cable made of a sheath material for a heating insulated cable obtained according to the method for evaluating a sheath material for a heating insulated cable described in the first aspect.

[0062] In a fourth aspect, an embodiment of the present invention provides an application of a heating insulated cable made of a sheath material for a heating insulated cable obtained according to the evaluation method for a sheath material for a heating insulated cable described in the first aspect in an oil and gas field.

[0063] The beneficial effects of the above technical solution provided by the embodiment of the present invention include at least:

[0064] The embodiment of the present invention provides a method for evaluating the sheath material for a heating insulation cable, a sheath material, a heating insulation cable and an application thereof. The method is used to evaluate the applicability of the sheath material for a heating insulation cable during the in-situ conversion of shale oil, and can quickly determine the type of required sheath material. Inappropriate materials can be gradually eliminated during the evaluation process, and the implementation is simple, the system is strong, and the accuracy is high. It provides a scientific and objective basis for quickly determining the material of the sheath material, and ensures that the in-situ conversion of shale oil is carried out safely and efficiently.

[0065] The above evaluation method provided in the embodiment of the present invention is in the order of normal temperature mechanical property evaluation, high temperature mechanical property evaluation, high temperature creep property evaluation, corrosion property evaluation and high temperature mechanical property evaluation after corrosion in the evaluation process. The evaluation process is from easy to difficult, step by step, and the evaluation performance is gradually improved. That is, the next performance evaluation is carried out only on the premise of meeting the performance requirements of the previous step. This not only enables layer-by-layer screening, but also avoids the drawback of directly conducting a high-difficulty evaluation and failing to meet the requirements. Furthermore, the method provides theoretical guidance and technical support for the selection of sheath materials for heating insulated cables under complex working conditions, and solves the current technical problems that the evaluation of sheath materials is not systematic enough, the evaluation means are single; the evaluation is difficult in complex environments; the use of experience judgment is highly subjective and the basis is insufficient; the accuracy of the evaluation results cannot be guaranteed, etc.

[0066] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0067] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0069] Figure 1 It is a flow chart of a method for evaluating a sheath material for a heating insulated cable provided in an embodiment of the present invention;

[0070] Figure 2 A flow chart of a normal temperature mechanical property testing method provided in an embodiment of the present invention;

[0071] Figure 3 A structural diagram of a sample 1 provided in an embodiment of the present invention;

[0072] Figure 4 A flow chart of a high temperature mechanical properties testing method provided in an embodiment of the present invention;

[0073] Figure 5 A flow chart of a high temperature creep performance testing method provided in an embodiment of the present invention;

[0074] Figure 6 A structural diagram of a sample 2 provided in an embodiment of the present invention;

[0075] Figure 7 A flow chart of a high temperature and high pressure corrosion simulation test provided in an embodiment of the present invention;

[0076] Figure 8 A structural diagram of a sample 3 provided in an embodiment of the present invention;

[0077] Fig. 9 This is a flow chart of a method for testing high-temperature mechanical properties after pre-corrosion provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0078] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0079] The inventors have found in actual work that there is no systematic and comprehensive evaluation process and method for the sheath materials of insulating heating cables suitable for shale oil in-situ conversion technology. The sheath material is in a state of long-term stress and high-temperature corrosion during use, and due to differences in working areas, the working environment and performance requirements of the sheath material are different. Therefore, a single performance test and requirement for the sheath material cannot meet the evaluation criteria for heating cable materials under actual working conditions. It is worth noting that the corrosive components in the environment will cause the cable to corrode and thin, and the working environment of cables in different regions is not the same. Therefore, the evaluation process and method for the sheath materials for heating insulated cables need to fully consider the above issues. In view of this, it is necessary to design a set of evaluation processes and methods for sheath materials that can be suitable for complex working conditions, and to provide theoretical guidance and technical support for the selection of sheath materials for heating insulated cables under complex working conditions. In order to provide theoretical guidance and technical support for the selection of sheath materials for heating insulated cables under complex working conditions, and to solve the current technical problems that the evaluation of sheath materials is not systematic enough, the evaluation means are single; the evaluation is difficult under complex environments; the empirical judgment is used, which is highly subjective and has insufficient basis; the accuracy of the evaluation results cannot be guaranteed; in view of the above technical problems, an evaluation method for sheath materials for heating insulated cables, sheath materials, heating insulated cables and applications are provided in the embodiments of the present invention.

[0080] In an embodiment of the present invention, a method for evaluating a sheath material for a heating insulation cable is provided. Figure 1 As shown, the evaluation method may include the following steps:

[0081] Step S11, performing room temperature mechanical property tests and high temperature mechanical property tests on the raw materials of the sheath based on actual service conditions, and evaluating the room temperature mechanical properties and high temperature mechanical properties of the raw materials of the sheath.

[0082] During the specific implementation of this step, firstly, a room temperature mechanical property test is performed on the sheath raw material based on actual service conditions to evaluate the room temperature mechanical properties of the sheath raw material; then, a high temperature mechanical property test is performed on the sheath raw material that meets the room temperature mechanical properties based on actual service conditions to evaluate the high temperature mechanical properties of the sheath raw material.

[0083] Step S12: Perform a high temperature creep performance test on the sheath raw material that meets the room temperature mechanical properties and high temperature mechanical properties to evaluate the high temperature creep performance of the sheath raw material.

[0084] Step S13: Perform a high-temperature and high-pressure corrosion simulation test on the sheath raw material that meets the high-temperature creep performance, and evaluate the corrosion margin of the sheath raw material under a long period.

[0085] Step S14: Conduct high-temperature and high-pressure corrosion simulation tests and high-temperature mechanical property tests on the sheath raw materials that meet the corrosion margin under long-term conditions, so as to conduct a comprehensive evaluation of the sheath materials for the heating insulation cable.

[0086] The above-mentioned evaluation method for the sheath material for the heating insulated cable provided in the embodiment of the present invention is used to evaluate the applicability of the sheath material for the heating insulated cable during the in-situ conversion of shale oil, and can quickly determine the type of required sheath material. Inappropriate materials can be gradually eliminated during the evaluation process, and the implementation is simple, the system is strong, and the accuracy is high. It provides a scientific and objective basis for quickly determining the material of the sheath material, and ensures that the in-situ conversion of shale oil is carried out safely and efficiently.

[0087] The above evaluation method provided in the embodiment of the present invention is in the order of normal temperature mechanical property evaluation, high temperature mechanical property evaluation, high temperature creep property evaluation, corrosion property evaluation and high temperature mechanical property evaluation after corrosion in the evaluation process. The evaluation process is from easy to difficult, step by step, and the evaluation performance is gradually improved. That is, the next performance evaluation is carried out only on the premise of meeting the performance requirements of the previous step. This not only enables layer-by-layer screening, but also avoids the drawback of directly conducting a high-difficulty evaluation and failing to meet the requirements. Furthermore, the method provides theoretical guidance and technical support for the selection of sheath materials for heating insulated cables under complex working conditions, and solves the current technical problems that the evaluation of sheath materials is not systematic enough, the evaluation means are single; the evaluation is difficult in complex environments; the use of experience judgment is highly subjective and the basis is insufficient; the accuracy of the evaluation results cannot be guaranteed, etc.

[0088] In an optional embodiment, the room temperature mechanical properties test of the sheath raw material is carried out based on the actual service conditions to evaluate the room temperature mechanical properties of the sheath raw material, referring to Figure 2 As shown, the following steps may be specifically included:

[0089] Step S201: Flatten the raw material of the jacket and perform wire cutting to produce a sample, so that the sample surface has no dents or burrs after processing. Figure 3 As shown, in the embodiment of the present invention, Figure 3 The sheath raw material is processed by wire cutting in the tensile test specimen structure. The processing requirements must meet the requirement that the sample surface has no obvious defects such as dents and burrs that affect the performance of the sample.

[0090] Step S202: Use 120-mesh, 360-mesh and 800-mesh sandpaper to polish the sample in turn to remove the wire cutting marks, and the final polishing marks are consistent with the tensile loading direction of the sample. In this embodiment, the tensile loading direction of the sample is the tensile force direction.

[0091] Step S203, make an original mark on the surface of the sample, and measure and record the length of the original mark. In this step, a thinner marker is used to draw the original mark on the surface of the sample, so that the length of the mark before and after stretching can be accurately measured.

[0092] Step S204, use the high temperature tensile testing machine to perform a tensile test at room temperature, and end the tensile test when the sample is broken. In this embodiment, a computer (control device) is connected to the high temperature tensile testing machine, the sample is loaded onto the high temperature tensile testing machine, the computer and the high temperature tensile testing machine are turned on, and then the tensile testing machine control software on the computer is turned on to perform the tensile test.

[0093] Step S205: Determine the yield strength curve of the sheath raw material at room temperature based on the tensile test. In the specific implementation of this step, a room temperature tensile test can be performed according to GB / T 228.1-2021 "Metallic Materials Tensile Test Part 1: Room Temperature Test Method" to determine the yield strength curve.

[0094] Step S206: Determine the strength requirement of the cable sheath at room temperature based on the cable weight at the preset depth and the cross-sectional area of ​​the cable sheath material. The preset depth in this step is the depth of the cable from the ground to the well, and at the preset depth, the cable weight needs to be borne by the cable sheath material on the outer layer of the cable.

[0095] Step S207: Based on the yield strength curve of the sheath raw material at room temperature and the strength requirement of the cable sheath at room temperature, the room temperature mechanical properties of the sheath raw material are evaluated.

[0096] The above-mentioned room-temperature mechanical properties testing method provided in the embodiment of the present invention first avoids sample defects by flattening the sheath raw material and then performing wire cutting; then it is polished with sandpaper and length marked, and finally a tensile test is performed under room temperature conditions. The yield strength curve of the sample under room temperature conditions can be accurately obtained, and finally the cable's own weight and cross-sectional area ratio are used as evaluation requirements. It plays a guiding role in the room-temperature mechanical properties evaluation of the sheath raw material, and provides a complete theoretical basis and verification criteria for further screening out sheath raw materials that meet the room-temperature mechanical properties requirements.

[0097] In another optional embodiment, the above-mentioned normal temperature mechanical property test of the sheath raw material based on the actual service conditions may also include: step S208, preparing multiple groups of parallel samples for normal temperature mechanical property test to comprehensively evaluate the normal temperature mechanical properties of the sheath raw material. In this step, after step S204, new samples are installed, for example, 3 groups of parallel samples are set for each test. It should also be noted that after the parallel samples are tested in step S204 and this step, the samples are vacuum dried and stored, so as to avoid oxidation of the sample fracture due to long-term storage.

[0098] In another optional embodiment, a high temperature mechanical property test is performed on the sheath raw material that meets the room temperature mechanical properties based on the actual service conditions to evaluate the high temperature mechanical properties of the sheath raw material, referring to Figure 4 As shown, the following steps may be specifically included:

[0099] Step S401: Flatten the raw material of the jacket and perform wire cutting to produce a sample, so that the sample surface has no dents or burrs after processing. Figure 3 As shown, in the embodiment of the present invention, Figure 3 The sheath raw material is processed by wire cutting in the tensile test specimen structure. The processing requirements must meet the requirement that the sample surface has no obvious defects such as dents and burrs that affect the performance of the sample.

[0100] Step S402: Use 120-mesh, 360-mesh and 800-mesh sandpaper to polish the sample in turn to remove the wire cutting marks, and the final polishing marks are consistent with the tensile loading direction of the sample. In this embodiment, the tensile loading direction of the sample is the tensile force direction.

[0101] Step S403: Make an original mark on the surface of the sample, and measure and record the length of the original mark. In this step, a thinner marker is used to draw the original mark on the surface of the sample, so that the length of the mark before and after stretching can be accurately measured.

[0102] Step S404: Use a high temperature tensile testing machine to heat the tensile area of ​​the sample to the service temperature of the jacket raw material under high temperature conditions to perform a tensile test, and end the tensile test when the sample is broken. In this embodiment, a computer (control device) is connected to the high temperature tensile testing machine, the sample is loaded onto the high temperature tensile testing machine, the computer and the high temperature tensile testing machine are turned on, and then the tensile testing machine control software on the computer is turned on to perform the tensile test.

[0103] Step S405: Determine the yield strength curve of the sheath raw material under high temperature conditions based on the tensile test. In the specific implementation of this step, a high temperature tensile test can be performed according to GB / T 228.1-2021 "Metallic Materials Tensile Test Part 2: High Temperature Test Method" to determine the yield strength curve.

[0104] Step S406: Calculate the strength requirement (minimum yield strength) of the sheath raw material under high temperature conditions based on the formation pressure and casing parameters of the sheath raw material when in service. In this step, the sheath raw material is subjected to extrusion force when in service, and the strength requirement of the sheath raw material under high temperature conditions is calculated according to the following formula, which is as follows:

[0105]

[0106] Among them, P YPis the crushing pressure of the material (which can be determined according to the formation pressure), D is the outer diameter of the casing, t is the thickness of the casing, and Y P is the minimum yield strength.

[0107] Step S407: Evaluate the high temperature mechanical properties of the sheath raw material based on the yield strength curve of the sheath raw material under high temperature conditions and the strength requirement (minimum yield strength) of the cable sheath under high temperature conditions.

[0108] The above-mentioned high-temperature mechanical properties testing method provided in the embodiment of the present invention first avoids sample defects by flattening the sheath raw material and then performing wire cutting; then it is polished with sandpaper and length marked, and finally a tensile test is performed under normal temperature conditions, so that the yield strength curve of the sample under normal temperature conditions can be accurately obtained. Finally, the strength requirement of the sheath raw material under high temperature conditions is calculated based on the formation pressure of the sheath raw material when in service as the evaluation requirement, which plays a guiding role in the high-temperature mechanical properties evaluation of the sheath raw material and provides a complete theoretical basis and verification criteria for further screening out sheath raw materials that meet the high-temperature mechanical properties requirements.

[0109] In another optional embodiment, the above-mentioned high-temperature mechanical property test of the sheath raw material based on the actual service conditions may also include: step S408, preparing multiple groups of parallel samples for high-temperature mechanical property test to comprehensively evaluate the high-temperature mechanical properties of the sheath raw material. In this step, after step S404, new samples are installed, for example, 3 groups of parallel samples are set for each test. It should also be noted that after the parallel samples are tested in step S404 and this step, the samples are vacuum dried and stored, so as to avoid oxidation of the sample fracture due to long-term storage.

[0110] In another optional embodiment, a high temperature creep performance test is performed on the sheath raw material that meets the high temperature mechanical properties to evaluate the high temperature creep performance of the sheath raw material, referring to Figure 5 As shown, the following steps may be specifically included:

[0111] Step S501: Flatten the raw material of the jacket and perform wire cutting to produce a sample, so that the sample surface has no dents or burrs after processing. Figure 6 As shown, in the embodiment of the present invention, Figure 6 The medium and high temperature creep specimen structure is processed by wire cutting on the raw materials of the sheath. The processing requirements must meet the requirements that the sample surface has no obvious defects such as dents and burrs that affect the performance of the sample.

[0112] Step S502: Use 120-mesh, 360-mesh and 800-mesh sandpaper to polish the sample in turn to remove the wire cutting marks, and the final polishing marks are consistent with the tensile loading direction of the sample. In this embodiment, the tensile loading direction of the sample is the tensile force direction.

[0113] Step S503: Make an original mark on the surface of the sample, and measure and record the length of the original mark. In this step, a thinner marker is used to draw an original mark on the surface of the sample, so that the length of the mark before and after high temperature creep can be accurately measured.

[0114] Step S504, use a high temperature creep endurance tester to heat the tensile area of ​​the sample to the service temperature of the jacket raw material under high temperature conditions to perform a tensile creep test, and end the tensile test when the sample is broken or the creep time (e.g., 100 hours) is reached. In this embodiment, a computer (control device) is connected to the high temperature creep endurance tester, the sample is loaded onto the high temperature creep endurance tester, the computer and the high temperature creep endurance tester are turned on, and then the high temperature creep endurance tester control software on the computer is turned on to perform a high temperature creep tensile test.

[0115] Step S505: Determine the creep curve of the sheath raw material under high temperature creep conditions based on the tensile test. In the specific implementation of this step, a high temperature creep tensile test under a certain period can be performed according to GB / T2039-2012 "Metallic Material Uniaxial Tensile Creep Test Method".

[0116] Step S506: Determine the high temperature creep strength requirement of the cable sheath under high temperature conditions according to the service life of the sheath raw materials. In this step, a creep test in a short time period is used to verify the high temperature creep strength requirement under long-term high temperature conditions, that is, the long-term high temperature creep strength requirement is inferred based on the creep amount in a known time period.

[0117] Step S507: Evaluate the high temperature creep performance of the sheath raw material based on the creep curve of the sheath raw material under high temperature creep conditions and the high temperature creep strength requirement of the cable sheath under high temperature conditions.

[0118] The above-mentioned high-temperature creep performance evaluation method provided in the embodiment of the present invention first avoids sample defects by flattening the sheath raw material and then performing wire cutting; then it is polished with sandpaper and length marked, and finally a high-temperature creep tensile test is performed, so that the creep curve of the sample under high-temperature creep conditions can be accurately obtained. Finally, the high-temperature creep strength requirement of the cable sheath under high-temperature conditions is used as the evaluation requirement, which plays a guiding role in the high-temperature creep performance evaluation of the sheath raw material, and provides a complete theoretical basis and verification criteria for further screening out sheath raw materials that meet the high-temperature creep performance requirements.

[0119] In another optional embodiment, the high temperature creep performance test to evaluate the high temperature creep performance of the sheath raw material may also include the following steps: Step S508, prepare multiple groups of parallel samples for high temperature creep performance test to comprehensively evaluate the high temperature creep performance of the sheath raw material. After step S504, new samples are installed. For example, 3 groups of parallel samples are set for each test. It should also be noted that after the parallel samples are tested in step S504 and this step, the samples are vacuum dried and stored, so as to avoid oxidation of the sample fracture due to long-term storage.

[0120] In another optional embodiment, a high temperature and high pressure corrosion simulation test is performed on the sheath raw material that meets the high temperature creep performance to evaluate the corrosion margin of the sheath raw material under a long period. In this embodiment, the corrosion parameters may include: temperature, H2O partial pressure, H2S partial pressure, CO2 partial pressure, H2 partial pressure, corrosion cycle, etc. In this embodiment, the corrosion parameters can be adjusted according to the actual working conditions. Figure 7 As shown, the following steps may be specifically included:

[0121] Step S701: Flatten the raw material of the jacket and perform wire cutting to produce a sample, so that the sample surface has no dents or burrs after processing. Figure 8 As shown, in the embodiment of the present invention, Figure 3 The sheath raw material is processed by wire cutting in the sample structure. The processing requirements must meet the requirement that the sample surface has no obvious defects such as dents and burrs that affect the performance of the sample.

[0122] Step S702: Use 120-mesh, 360-mesh and 800-mesh sandpaper to polish the sample in sequence to remove the wire cutting marks, and finally the surface of the sample is smooth and flat after polishing.

[0123] Step S703, make original marks on the surface of the sample to record the numbers of multiple groups of samples. In this embodiment, the marking is to mark the sample numbers. The difference between the high-temperature and high-pressure corrosion simulation test in the embodiment of the present invention and the above-mentioned normal temperature mechanical properties test, high-temperature mechanical properties test and high-temperature creep properties test is that in the above three tests, one sample is tested, and after the test is completed, the parallel sample is replaced and the test is repeated. The high-temperature and high-pressure corrosion simulation test in the embodiment of the present invention is that multiple samples are tested at the same time, that is, multiple samples are placed in a high-temperature and high-pressure reactor at the same time after treatment, so as to ensure the consistency of the corrosion environment and avoid the occurrence of different corrosion results due to different corrosion environments.

[0124] Step S704: rinse the sample with deionized water, dehydrate with anhydrous ethanol, remove oil with acetone, and dry with cold air.

[0125] Step S705: Use a vernier caliper with an accuracy of 0.01 mm to measure the sample and an electronic balance with an accuracy of 0.1 mg to weigh the sample.

[0126] Step S706, placing the sample on a corundum burning boat and placing it in a high-temperature and high-pressure reactor. In a specific example, the present invention uses a 3L electromagnetic heating high-temperature and high-pressure Hastelloy reactor to conduct a corrosion simulation test based on the service environment of the sheath material for the heated insulated cable. In the specific implementation, the test temperature is 600°C, the H2O partial pressure is 15MPa, the H2S partial pressure is 1MPa, the CO2 partial pressure is 2MPa, and the H2 partial pressure is 0.82MPa, totaling 18.82MPa, to simulate the actual service conditions.

[0127] Step S707, inject a quantitative amount of deionized water into the high-temperature and high-pressure reactor, and continuously introduce high-purity nitrogen for no less than 24 hours. In this step, the deionized water is introduced with high-purity nitrogen so as to remove oxygen from the deionized water and avoid the influence of oxygen on the test results, so as to improve the test accuracy. In the above example, the embodiment of the present invention can calculate the amount of the above deionized water as 120g according to the ideal gas state equation, so as to ensure that the water vapor partial pressure is 15MPa.

[0128] Step S708: High-purity nitrogen is continuously introduced into the high-temperature and high-pressure reactor for no less than 6 hours to remove the residual air in the high-temperature and high-pressure reactor. In this step, high-purity nitrogen is introduced into the high-temperature and high-pressure reactor to remove oxygen from the reaction system and avoid the influence of oxygen on the test results, so as to improve the test accuracy.

[0129] Step S709: At room temperature, introduce a CO2-H2S-H2 mixed gas into the high temperature and high pressure reactor to make the pressure inside the reactor reach 1.3MPa. It should be noted that the CO2-H2S-H2 mixed gas is pre-mixed according to the partial pressure of each gas, and the introduction of a 1.3MPa mixed gas at room temperature is pre-calculated based on the ideal gas state equation, so that after the high temperature and high pressure reactor is heated to 600°C, the pressure inside the reactor can be calculated to be 18.82MPa according to the ideal gas state equation, which meets the corrosion environment of the actual working conditions in the simulation well.

[0130] Step S710: Perform a 168h long-term high-temperature and high-pressure corrosion simulation test on the sample.

[0131] Step S711, after the test is completed, turn off the heating equipment of the high-temperature and high-pressure reactor, and when the temperature inside the high-temperature and high-pressure reactor drops below 60°C, open the exhaust valve of the high-temperature and high-pressure reactor to discharge the gas in the high-temperature and high-pressure reactor to the exhaust gas treatment device.

[0132] Step S712: After the gas in the high-temperature and high-pressure reactor is exhausted, high-purity nitrogen is continuously introduced into the high-temperature and high-pressure reactor for not less than 30 minutes to remove the harmful gases remaining in the reactor and pipelines of the high-temperature and high-pressure reactor.

[0133] Step S713, open the high temperature and high pressure reactor, take out the sample and dry it in a vacuum drying oven at 120°C for 2 hours.

[0134] Step S714: weigh the dried test piece and evaluate the corrosion margin of the sheath raw material under long-term corrosion rate.

[0135] In this embodiment, the corrosion rate can be calculated according to the following formula, and the specific calculation formula is as follows:

[0136]

[0137] Among them, V CR is the corrosion rate, mm / y; W1 and W2 are the weight of the sample before and after corrosion, g; S is the surface area of ​​the sample (before corrosion), cm 2 ; ρ is the sample density (before corrosion), g / cm 3 ; t is the corrosion time, h; 8.76×10 4 is the unit conversion constant.

[0138] It should be noted that the corrosion margin of the sheath material under long-term conditions can be determined based on the corrosion rate. Different samples can be used to conduct high-temperature and high-pressure corrosion simulation tests for 3 days, 7 days, 15 days, and 1 month, respectively. Due to the change in time parameters, it can be determined that the corrosion rate gradually decreases. It should be further noted that in the embodiment of the present invention, a scanning electron microscope can also be used to observe the surface and cross-section of the corrosion sample to determine whether uneven corrosion behaviors such as local corrosion occur. If so, it is determined that the high-temperature and high-pressure corrosion resistance is not good.

[0139] The high temperature and high pressure corrosion simulation test of the above-mentioned sheath raw material provided in the embodiment of the present invention first avoids sample defects by flattening the sheath raw material and then performing wire cutting; then it is polished with sandpaper and the sample number is marked, and finally a high temperature and high pressure corrosion simulation test is performed, which can accurately obtain the corrosion rate of the sample under high temperature and high pressure conditions. Finally, the specific service time of the sheath raw material when in service is used as the evaluation requirement, which plays a guiding role in the corrosion performance evaluation of the sheath raw material, and provides a complete theoretical basis and verification criteria for further screening out sheath raw materials that meet the corrosion performance requirements.

[0140] In another optional embodiment, a high temperature and high pressure corrosion simulation test and a high temperature mechanical property test are performed on the sheath raw material that meets the corrosion margin under a long period to evaluate the high temperature mechanical properties of the sheath raw material after pre-corrosion, referring to Fig. 9As shown, the following steps may be specifically included:

[0141] Step S901: Flatten the raw material of the jacket and perform wire cutting to produce a sample, so that the sample surface has no dents or burrs after processing. Figure 3 As shown, in the embodiment of the present invention, Figure 3 The sheath raw material is processed by wire cutting in the tensile test specimen structure. The processing requirements must meet the requirement that the sample surface has no obvious defects such as dents and burrs that affect the performance of the sample.

[0142] Step S902: Use 120-mesh, 360-mesh and 800-mesh sandpaper to polish the sample in turn to remove the wire cutting marks, and the final polishing marks are consistent with the tensile loading direction of the sample. In this embodiment, the tensile loading direction of the sample is the tensile force direction.

[0143] Step S903: perform original marking on the surface of the sample to record the serial numbers of multiple groups of samples.

[0144] Step S904: Place the sample in a high temperature and high pressure reactor and perform a pre-corrosion test according to a high temperature and high pressure corrosion simulation test. The process of the high temperature and high pressure corrosion simulation test in the embodiment of the present invention can refer to steps S704 to S713 in the above embodiment, and the embodiment of the present invention will not be repeated here.

[0145] Step S905: make an original mark on the surface of the sample after the pre-corrosion test, and measure and record the length of the original mark.

[0146] Step S906, use a high temperature tensile testing machine to heat the tensile area of ​​the sample after the pre-corrosion test to the service temperature of the sheath raw material under high temperature conditions for tensile testing, and end the tensile test when the sample is broken. It should be noted that after this step is completed, a new sample (the sample after the pre-corrosion test) is installed in the high temperature tensile testing machine. For example, 3 groups of parallel samples are set for each group of tests to perform high temperature mechanical properties tests after pre-corrosion. It should also be noted that after the test is completed, the sample is vacuum dried and stored to prevent the sample fracture from being oxidized due to long-term storage.

[0147] Step S907: Determine the yield strength curve of the sheath raw material under high temperature conditions after pre-corrosion based on the tensile test. In the specific implementation of this step, a high temperature tensile test can be performed according to GB / T 228.1-2021 "Tensile Test of Metallic Materials Part 2: High Temperature Test Method" to determine the yield strength curve under high temperature conditions after pre-corrosion.

[0148] Step S908: Evaluate the high-temperature mechanical properties of the sheath raw material after pre-corrosion based on the yield strength curve of the sheath raw material under high-temperature conditions after pre-corrosion and the yield strength curve of the sheath raw material under high-temperature conditions without pre-corrosion.

[0149] In this step, the high temperature mechanical properties of the sheath raw materials after pre-corrosion are evaluated. Specifically, the following formula can be used for performance evaluation:

[0150]

[0151] Among them, I σ is the yield strength loss, σ s is the yield strength after 7 days of corrosion (7 days is set from the perspective of experimental difficulty; the longer the time, the smaller the corrosion and creep rates), and σ0 is the yield strength before corrosion.

[0152] The method for testing the high-temperature mechanical properties of the above-mentioned sheath raw material after pre-corrosion provided in the embodiment of the present invention first avoids sample defects by flattening the sheath raw material and then wire cutting it; then, it is subjected to high-temperature and high-pressure pre-corrosion treatment after sandpaper polishing and marking, and a high-temperature mechanical property test is performed after further length marking based on the pre-corrosion treatment. This method can determine the yield strength loss based on the yield strength after corrosion under high temperature conditions and the yield strength before corrosion, which provides a guiding direction for the evaluation of the high-temperature mechanical properties of the sheath raw material after pre-corrosion, and provides a complete theoretical basis and verification criteria for further screening out sheath raw materials that meet the requirements of high-temperature mechanical properties after pre-corrosion.

[0153] In the embodiment of the present invention, after the sheath raw material meets the above-mentioned room temperature mechanical properties, high temperature mechanical properties, high temperature creep properties, high temperature and high pressure corrosion properties and high temperature mechanical properties after pre-corrosion, it can be accurately judged that the sheath raw material meets the requirements of sheath materials for heating insulation cables, which provides a scientific and objective basis for quickly determining the material of the sheath material and ensures that the in-situ conversion of shale oil is carried out safely and efficiently.

[0154] Based on the same inventive concept, an embodiment of the present invention further provides a sheath material for a heating insulating cable obtained according to the above-mentioned evaluation method for a sheath material for a heating insulating cable.

[0155] Based on the same inventive concept, an embodiment of the present invention further provides a heating insulated cable made of a sheath material for a heating insulated cable obtained according to the above-mentioned evaluation method for a sheath material for a heating insulated cable.

[0156] Based on the same inventive concept, an embodiment of the present invention also provides an application of a heating insulated cable made of a heating insulated cable sheath material obtained according to the above-mentioned heating insulated cable sheath material evaluation method in an oil and gas field.

[0157] The beneficial effects of the above-mentioned sheath material for heating insulated cables, heating insulated cables and application of heating insulated cables in oil and gas fields in the embodiments of the present invention can refer to the above-mentioned evaluation method for sheath materials for heating insulated cables, and the embodiments of the present invention will not be repeated here.

[0158] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for evaluating sheath materials for heating insulation cables, characterized in that: include: Conducting room temperature mechanical property tests and high temperature mechanical property tests on the raw materials of the sheath based on actual service conditions to evaluate the room temperature mechanical property and high temperature mechanical property of the raw materials of the sheath; For the sheath raw materials that meet the normal temperature mechanical properties and high temperature mechanical properties, high temperature creep performance test is carried out to evaluate the high temperature creep performance of the sheath raw materials; Conduct high-temperature and high-pressure corrosion simulation tests on sheath raw materials that meet high-temperature creep performance to evaluate the corrosion margin of the sheath raw materials under long-term conditions; High-temperature and high-pressure corrosion simulation tests and high-temperature mechanical properties tests are carried out on the sheath raw materials that meet the corrosion margin under long-term conditions, so as to conduct a comprehensive evaluation of the sheath materials for heating insulated cables.

2. The method according to claim 1, characterized in that The room temperature mechanical properties test of the sheath raw material is carried out based on actual service conditions to evaluate the room temperature mechanical properties of the sheath raw material, including: The raw material of the sheath is flattened and then processed by wire cutting to produce a sample, so that the surface of the sample has no depressions and burrs after processing; Use 120 mesh, 360 mesh and 800 mesh sandpaper to polish the sample in sequence to remove the wire cutting marks, and the final polishing marks are consistent with the tensile loading direction of the sample; Making an original mark on the surface of the sample, and measuring and recording the length of the original mark; Performing a tensile test at room temperature using a high temperature tensile testing machine, and ending the tensile test when the sample is broken; Determining the yield strength curve of the sheath raw material at room temperature based on a tensile test; Determine the strength requirements of the cable sheath at normal temperature based on the cable weight at the preset depth and the cross-sectional area of ​​the cable sheath material; Based on the yield strength curve of the sheath raw material at room temperature and the strength requirements of the cable sheath at room temperature, the room temperature mechanical properties of the sheath raw material are evaluated.

3. The method according to claim 2, characterized in that Also includes: A plurality of groups of parallel samples of the samples are prepared to carry out room temperature mechanical property tests, so as to comprehensively evaluate the room temperature mechanical properties of the raw materials of the sheath.

4. The method according to claim 2, characterized in that: For sheath raw materials that meet the room temperature mechanical properties, high temperature mechanical properties tests are performed based on actual service conditions to evaluate the high temperature mechanical properties of the sheath raw materials, including: The raw material of the sheath is flattened and then processed by wire cutting to produce a sample, so that the surface of the sample has no depressions and burrs after processing; Use 120 mesh, 360 mesh and 800 mesh sandpaper to polish the sample in sequence to remove the wire cutting marks, and the final polishing marks are consistent with the tensile loading direction of the sample; Making an original mark on the surface of the sample, and measuring and recording the length of the original mark; Using a high temperature tensile testing machine to heat the tensile region of the sample to the service temperature of the jacket raw material under high temperature conditions to perform a tensile test, and ending the tensile test when the sample is broken; Determining the yield strength curve of the sheath raw material under high temperature conditions based on a tensile test; Calculating the strength requirement of the jacket raw material under high temperature conditions based on the formation pressure and casing parameters of the jacket raw material when in service; Based on the yield strength curve of the sheath raw material under high temperature conditions and the strength requirements of the cable sheath under high temperature conditions, the high temperature mechanical properties of the sheath raw material are evaluated.

5. The method according to claim 4, characterized in that Also includes: A plurality of groups of parallel samples of the samples are prepared to carry out high temperature mechanical property tests, so as to comprehensively evaluate the high temperature mechanical properties of the raw materials of the sheath.

6. The method according to claim 4, characterized in that For sheath raw materials that meet high temperature mechanical properties, high temperature creep performance tests are carried out to evaluate the high temperature creep performance of the sheath raw materials, including: The raw material of the sheath is flattened and then processed by wire cutting to produce a sample, so that the surface of the sample has no depressions and burrs after processing; Use 120 mesh, 360 mesh and 800 mesh sandpaper to polish the sample in sequence to remove the wire cutting marks, and the final polishing marks are consistent with the tensile loading direction of the sample; Making an original mark on the surface of the sample, and measuring and recording the length of the original mark; Using a high temperature creep endurance tester, the tensile region of the sample is heated to the service temperature of the sheath raw material under high temperature conditions to perform a tensile creep test, and the tensile test is terminated when the sample is broken or the creep time is reached; Determining the creep curve of the sheath raw material under high temperature creep conditions based on a tensile test; According to the service life of the raw materials of the sheath, the high temperature creep strength requirements of the cable sheath under high temperature conditions are determined; Based on the creep curve of the sheath raw material under high temperature creep conditions and the high temperature creep strength requirements of the cable sheath under high temperature conditions, the high temperature creep performance of the sheath raw material is evaluated.

7. The method according to claim 6, characterized in that Also includes: A plurality of groups of parallel samples of the samples are prepared to carry out high temperature creep performance tests, so as to comprehensively evaluate the high temperature creep performance of the raw materials of the sheath.

8. The method according to claim 6, characterized in that A high temperature and high pressure corrosion simulation test is conducted on the sheath raw materials that meet the high temperature creep performance to evaluate the corrosion margin of the sheath raw materials under long-term conditions, including: The raw material of the sheath is flattened and then processed by wire cutting to produce a sample, so that the surface of the sample has no depressions and burrs after processing; The sample was polished with 120-mesh, 360-mesh and 800-mesh sandpaper in sequence to remove the wire cutting marks of the sample, and the surface of the sample was smooth and flat after final polishing; Marking the surface of the sample to record the serial numbers of the multiple groups of samples; Rinse the specimen with deionized water, dehydrate with anhydrous ethanol, remove oil with acetone, and dry with cold air; The sample is measured using a vernier caliper with an accuracy of 0.01 mm and weighed using an electronic balance with an accuracy of 0.1 mg; The sample is placed on a corundum burning boat and placed in a high temperature and high pressure reactor; Inject a quantitative amount of deionized water into the high temperature and high pressure reactor, into which high purity nitrogen is continuously introduced for no less than 24 hours; Continuously introducing high-purity nitrogen into the high-temperature and high-pressure reactor for not less than 6 hours to remove the residual air in the high-temperature and high-pressure reactor; At room temperature, a CO2-H2S-H2 mixed gas is introduced into the high temperature and high pressure reactor to make the pressure inside the high temperature and high pressure reactor reach 1.3 MPa; The sample is subjected to a 168-hour long-term high-temperature and high-pressure corrosion simulation test; After the test, turn off the heating device of the high-temperature and high-pressure reactor, and when the temperature in the high-temperature and high-pressure reactor drops below 60°C, open the exhaust valve of the high-temperature and high-pressure reactor to discharge the gas in the high-temperature and high-pressure reactor to the exhaust gas treatment device; After the gas in the high-temperature and high-pressure reactor is exhausted, high-purity nitrogen is continuously introduced into the high-temperature and high-pressure reactor for not less than 30 minutes to remove the harmful gases remaining in the reactor and pipelines of the high-temperature and high-pressure reactor; Open the high temperature and high pressure reactor, take out the sample and dry it in a vacuum drying oven at 120° C. for 2 h; The test piece was weighed after drying, and the corrosion rate was used to evaluate the corrosion margin of the sheath raw material over a long period of time.

9. The method according to claim 8, characterized in that The sheath raw materials that meet the corrosion allowance under long-term conditions are subjected to high-temperature and high-pressure corrosion simulation tests and high-temperature mechanical properties tests to evaluate the high-temperature mechanical properties of the sheath raw materials after pre-corrosion, including: The raw material of the sheath is flattened and then processed by wire cutting to produce a sample, so that the surface of the sample has no depressions and burrs after processing; Use 120 mesh, 360 mesh and 800 mesh sandpaper to polish the sample in sequence to remove the wire cutting marks, and the final polishing marks are consistent with the tensile loading direction of the sample; Marking the surface of the sample to record the serial numbers of the multiple groups of samples; Placing the sample in a high-temperature and high-pressure reactor to conduct a pre-corrosion test according to a high-temperature and high-pressure corrosion simulation test; Make an original mark on the surface of the sample after the pre-corrosion test, and measure and record the length of the original mark; Using a high temperature tensile testing machine, the tensile region of the sample after the pre-corrosion test is heated to the service temperature of the sheath raw material under high temperature conditions to perform a tensile test, and the tensile test is terminated when the sample is broken; Determining the yield strength curve of the sheath raw material under high temperature conditions after pre-corrosion based on a tensile test; Based on the yield strength curve of the sheath raw material under high temperature conditions after pre-corrosion and the yield strength curve of the sheath raw material under high temperature conditions without pre-corrosion, the high temperature mechanical properties of the sheath raw material after pre-corrosion are evaluated.

10. A sheath material for a heating insulated cable obtained according to the method for evaluating a sheath material for a heating insulated cable according to any one of claims 1 to 9.

11. A heating insulated cable made of a sheath material for a heating insulated cable obtained by the method for evaluating a sheath material for a heating insulated cable according to any one of claims 1 to 9.

12. Application of a heating insulated cable made of a heating insulated cable sheath material obtained by the method for evaluating a heating insulated cable sheath material according to any one of claims 1 to 9 in an oil and gas field.

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