Detection method for corrosion excavation verification of oil and gas long-distance transmission pipeline

Abstract

A detection method for corrosion excavation verification of an oil and gas long-distance transmission pipeline relates to the technical field of underground pipeline corrosion detection, and comprises the following steps: manufacturing a pulsed eddy current detection reference test block and an ultrasonic reference test block according to the material, size and wall thickness of the pipeline, and carrying out pulsed eddy current detection process calibration by adopting flat-bottom holes with different areas and the same depth; meanwhile, ball holes with different depths and the same size are adopted to verify the detection sensitivity of the full-focusing phased array probe, then a simulation technology is applied to optimize detection parameters of the full-focusing probe, and finally the optimized full-focusing probe is applied to corrosion spot detection of the pipeline, so that the detection precision is improved. The pulse eddy current technology and the ultrasonic full-focusing detection technology are combined, meanwhile, the detection sensitivity is corrected through the reference test block, the probe parameters are optimized through the result ultrasonic simulation technology, and the detection efficiency and the detection precision are completely superior to those of a traditional detection method.

Description

Technical Field

[0001] The invention relates to the technical field of underground pipeline corrosion detection, and in particular to a detection method for verifying corrosion excavation of long-distance oil and gas pipelines. Background Art

[0002] As the main transmission channel for oil and gas supply, long-distance pipelines have developed rapidly in recent years. However, due to the non-standard manufacturing process and construction of steel pipes, it is common for underground oil and gas pipelines to corrode and perforate 1 to 2 years after they are put into operation. This corrosion loss will not only cause oil and gas leakage losses, financial losses and manpower waste, but also may cause further fires, environmental pollution and other serious consequences.

[0003] Internal inspection of long-distance pipelines is an important means of regular inspection of pipelines, and is also an important basic work for pipeline integrity evaluation and guiding pipeline maintenance and repair. Magnetic flux leakage internal inspection is the mainstream technology in the current internal inspection industry. This technology can detect defects such as metal loss inside and outside the pipeline and wall thickness changes.

[0004] When the leakage magnetic detection finds corrosion, the location with the largest wall thickness reduction will generally be selected for excavation verification. During the excavation verification, there will be a certain deviation in both clock positioning and circumferential positioning. In this case, we need to peel off the anti-corrosion layer to measure the thickness and find the wall thickness reduction point. The known leakage magnetic detection generally uses mileage wheel encoding to locate the corrosion based on the nearby weld position. The normal pipe is generally 12m long, which means that there will be one weld every 12m. It is difficult to accurately locate the corrosion position axially. At the same time, in the circumferential detection, since the internal gyroscope is used for circumferential positioning, and the leakage magnetic detector moves fast in the pipeline, even up to several meters per second, the positioning will not be accurate in either the circumferential or axial directions. If the positioning deviation is large, it is necessary to perform large-scale anti-corrosion layer stripping on the defect position given by the leakage magnetic detection. Since the anti-corrosion layer is bonded to the pipeline, it is not only thick, but also very sticky and difficult to strip. Whether it is pulling out the anti-corrosion layer or finding the thinning point, a lot of manpower will be wasted and the detection efficiency is extremely low.

[0005] When measuring the thickness of the peeled anti-corrosion layer, the ultrasonic thickness gauge is usually used. Although the ultrasonic thickness gauge is small and light, the ultrasonic reflection beam will not be directly reflected to the probe during the test because the corrosion surface is not a regular plane. Figure 1As shown. Since the corrosion morphology is generally irregular, the ultrasonic reflection cannot be received by the probe, which can easily lead to missed detection or inaccurate detection results. In this way, it is difficult to find the real corrosion thinning point during ultrasonic thickness gauge detection. At the same time, since the size of the ultrasonic thickness gauge probe is very small, generally about 5mm, it is difficult to find corrosion defects when facing the curved detection surface of the pipeline and the large detection area, especially when the corrosion area is small, the efficiency is lower. Summary of the invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a detection method for verifying corrosion excavation of long-distance oil and gas pipelines. The method first provides a probe verification method to address the problem that pulse eddy current detection in the prior art cannot accurately locate the position, and the verified probe is used for accurate detection of the corrosion position of the long-distance oil and gas pipeline, thereby improving the detection accuracy and avoiding the inefficiency of excavation and maintenance caused by inaccurate detection position accuracy.

[0007] The technical solution adopted by the present invention is:

[0008] A detection method for corroded excavation verification of long-distance oil and gas pipelines comprises the following steps:

[0009] S110: According to the material of the pipeline to be inspected, the same pulsed eddy current test reference block and ultrasonic comparison test block are made to measure the longitudinal wave sound velocity and pulsed eddy current calibration;

[0010] Defects of corresponding sizes are machined on the pulsed eddy current test reference block and the ultrasonic comparison test block;

[0011] S120: Select the appropriate pulsed eddy current probe according to the size, material, thickness and anti-corrosion layer thickness of the pipeline to be inspected;

[0012] S130: Verify pulsed eddy current probes and instruments using pulsed eddy current test reference blocks;

[0013] Connect the selected probe to the pulsed eddy current tester, place the probe on a pulsed eddy current test reference block with a flexible pad whose thickness is equal to the thickness of the anti-corrosion layer, and select appropriate excitation voltage, A-scan start time, and A-scan duration parameters to ensure that the process can identify corrosion;

[0014] S140: Find the corrosion area in the pulsed eddy current C scan view;

[0015] Apply the verified pulsed eddy current probe to the pipeline under inspection, and use the pulsed eddy current imaging software to form a C-scan image to find the specific location of the corrosion;

[0016] S150: Perform CIVA simulation based on the pipe size, wall thickness and material to determine the acoustic field distribution in the defect area, defect echo, probe type, frequency and number of chips;

[0017] CIVA simulation software is used to perform acoustic field and sensitivity simulation analysis on the size and material of the pipe to be inspected, as well as the size of the corrosion to be inspected, to determine the probe type, frequency and number of chips. When inspecting thinner workpieces, a dual-line array probe and a higher frequency are selected. When the workpiece is thicker, a linear array probe is selected with 64 chips.

[0018] S160: The simulation probe is applied to the ultrasonic comparison test block. The probe should be able to identify all defects of the ultrasonic comparison test block and effectively identify the defect contour;

[0019] S170: placing the probe in the detection area for detection, using a grid scanning method, and generating a C-scan and a 3D view;

[0020] S180: Identify defects in the C-scan view and the 3D view, and determine the inspection position.

[0021] Furthermore, in step S110, pulsed eddy current detection reference blocks and ultrasonic comparison blocks are manufactured according to the pipe material, size and wall thickness to verify the detection sensitivity, wherein the pulsed eddy current reference blocks should be processed into flat-bottom holes of different areas, and the specific specifications and dimensions of the flat-bottom holes should at least include the indicated dimensions detected by magnetic leakage detection, and should also include the flat-bottom hole dimensions that are 50% of the volume of the dimension.

[0022] Furthermore, in step S130, based on the pulse eddy current detection reference block to be tested, a lift-off flexible pad with the same thickness as the anti-corrosion layer of the tested pipeline is prepared at the same time. The probe selected on the pulse eddy current detection reference block of the flexible pad should at least be able to find a flat-bottomed hole equivalent to the leakage magnetic indication. While meeting the sensitivity, a larger size probe and an array probe are selected. The probe footprint size range is: 22mm-46mm, power: 10W-20W; pulse width: 10ms-30ms; pulse frequency: 5Hz-20Hz; A scan start time: 1.5ms-5ms; A scan duration: 10ms-30ms.

[0023] Furthermore, in step S150, before ultrasonic testing, a model should be built based on the size, material and wall thickness of the pipeline to be tested, and the sound field should be simulated using CIVA simulation software. During the simulation, the corrosion defect response can be simulated. A dual linear array probe is selected for thin-walled pipelines, a self-focusing linear array probe is selected for small-size pipe testing, and a linear array probe is selected for thick-walled pipelines. The detection frequency is 5MHz-10MHz, the probe chip size is 0.3mm-0.6mm, the probe passive aperture size is 7.5mm-15mm, and the self-focusing size is 5mm-30mm.

[0024] Furthermore, in step S160, the probe selected by the simulation result is placed on the ultrasonic comparison test block, which should be processed into spherical holes of different depths. A single-line scanning method is used to detect each spherical hole in the reference test block in turn. The full focusing method should be able to detect each spherical hole signal and effectively identify its contour to ensure that its detection sensitivity meets the detection requirements. The full focusing mode is FMC full matrix capture, PWI plane wave imaging or PCI phase coherent imaging mode. The depth direction of the focus area should be greater than twice the plate thickness, and the width direction should be the same as the probe length direction. The pixel resolution of the focus area is 0.01mm-0.02mm.

[0025] Furthermore, in step S170, grid scanning is preferably selected during full-focus phased array detection to form a final C-scan and 3D view, and the thinnest detection area is further determined in the 3D view.

[0026] The present invention also provides a test block for the above-mentioned detection method for verifying corrosion excavation of long-distance oil and gas pipelines, including a pulsed eddy current detection reference test block and an ultrasonic comparison test block made according to the material, size and wall thickness of the inspected pipeline, wherein the pulsed eddy current reference test block should be processed into flat-bottom holes of different areas; the inner wall of the ultrasonic comparison test block is provided with spherical holes with different defects.

[0027] Furthermore, the specific specifications and dimensions of the flat-bottom hole of the pulsed eddy current testing reference test block at least include the indicated dimensions detected by magnetic flux leakage detection.

[0028] The principle of the present invention is:

[0029] As a non-contact electromagnetic detection method, pulsed eddy current detection technology can quickly provide C-scan imaging data of the pipe wall, and is very suitable for the detection of uniform thinning and concentrated corrosion pit areas; it is insensitive to lift-off changes (the distance between the probe and the detection surface); it can perform real-time calibration on the intact parts of the test piece. Pulsed eddy current can be used to detect defects and corrosion in ferromagnetic metal materials under coatings, fireproof layers or insulation layers, and the surface can be coated. However, because the measured value is the result of averaging within a certain range, the accuracy of the measurement of local pitting defects will be affected by the lift-off height.

[0030] Phased array ultrasonic testing is a classic array technology application method. In recent years, a fully focused detection imaging method has been developed based on phased array ultrasonic testing. Fully focused imaging can focus on the detected area. Because it uses a single-chip excitation and multi-chip reception method, it is insensitive to defect directionality, has high resolution of detection results, and has high detection sensitivity. It can be applied to fine detection of raw materials.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] By using pulsed eddy current detection technology, corrosion detection can be carried out even with an anti-corrosion layer. This can greatly reduce the time and effort required to peel off the anti-corrosion layer. However, pulsed eddy current also has technical limitations, that is, its detection accuracy is limited.

[0033] At this time, the anti-corrosion layer is stripped at the corrosion position determined by pulse eddy current detection, and ultrasonic full-focus detection technology is used. Since ultrasonic full-focus detection is not sensitive to the directionality of defects, defects at all angles can be identified, which can better restore the entire defect morphology and accurately measure the corrosion depth value. Ultrasonic full-focus detection technology is significantly better than conventional ultrasonic thickness measurement mode in fine measurement. The limitation of full-focus detection technology is also low detection efficiency.

[0034] This application combines pulsed eddy current technology with ultrasonic full-focusing detection technology, and at the same time corrects its detection sensitivity through a reference test block. As a result, ultrasonic simulation technology optimizes probe parameters to achieve detection efficiency and detection accuracy that are completely superior to traditional detection methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of ultrasonic thickness measurement in the background technology of the present invention.

[0036] Figure 2 This is a schematic diagram of the pulsed eddy current calibration test block of the present invention.

[0037] Figure 3 This is the TFM full focusing reference block of the present invention.

[0038] Figure 4 The figure is a flow chart of the method of the present invention.

[0039] Figure 5 The pulsed eddy current test results of the pulsed eddy current test block.

[0040] Figure 6 This is the CIVA probe acoustic field simulation result.

[0041] Figure 7 Simulation results of different defects detected by the probe.

[0042] Figure 8 This is the on-site pipeline inspection result.

[0043] Fig. 9 This is the pulsed eddy current test result.

[0044] Fig.10 Phased array detection results. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0046] See attached Figure 4 , the method adopted by the present invention comprises the following steps:

[0047] S110: According to the pipeline material, make the same pulsed eddy current test reference block and ultrasonic comparison test block for measuring longitudinal wave sound velocity and pulsed eddy current calibration.

[0048] According to the size and material of the pipeline, pulsed eddy current and ultrasonic fully focused reference test blocks of the same size are made respectively, and defects of corresponding sizes are processed on the test blocks, which are mainly used for pulsed eddy current and ultrasonic fully focused phased array sensitivity calibration to ensure effective corrosion detection. The pulsed eddy current reference test block should be processed into flat-bottom holes of different areas; the inner wall of the ultrasonic comparison test block is provided with spherical holes with different defects. And the specific specifications and dimensions of the flat-bottom holes of the pulsed eddy current detection reference test block at least include the indicated dimensions detected by magnetic flux leakage.

[0049] S120: Select the appropriate pulsed eddy current probe based on the size, material, thickness and anti-corrosion layer thickness of the workpiece to be inspected.

[0050] Pulse eddy current probes are generally divided into small, medium and large probes, and also include array probes and high-definition probes. When the diameter of the inspected pipe is small, it is recommended to choose a small probe. When the diameter of the pipe is large, it is recommended to choose an array probe. When the wall thickness is thin, it is recommended to choose a high-definition probe.

[0051] S130: Verify pulsed eddy current probes and instruments using reference test blocks.

[0052] Connect the selected probe to the pulsed eddy current tester, place the probe on a pulsed eddy current test reference block with a flexible pad (flexible pad thickness equal to the thickness of the anti-corrosion layer), and select appropriate parameters (excitation voltage, A-scan start time, A-scan duration) to ensure that the process can identify corrosion.

[0053] S140: Find the corrosion area in the pulsed eddy current C scan view.

[0054] This detection technology is applied to pipeline inspection, and pulse eddy current imaging software is used to form C-scan imaging to find the specific location of corrosion.

[0055] S150: Perform CIVA simulation based on the pipe size, wall thickness and material to determine the acoustic field distribution and defect echo in the defect area. Determine the probe type, frequency and number of chips.

[0056] CIVA simulation software is used to simulate and analyze the acoustic field and sensitivity of the pipe size and material to be tested, as well as the size of the corrosion to be tested, to determine the probe type, frequency and number of chips. When testing thinner workpieces, dual-line array probes and higher frequencies are generally selected. When the workpiece thickness is larger, linear array probes can be selected. Due to the use of full-focus detection technology, the more chips there are, the better the detection effect. Generally, 64 chips are recommended. If the pipe diameter is too small, the number of chips can be reduced.

[0057] S160: When applying the dummy probe to the ultrasonic comparison test block, the probe should be able to identify all defects and effectively identify the defect contours.

[0058] The probe of the simulation result is applied to the ultrasonic comparison test block. The probe should be able to clearly display the outlines of all defects in the ultrasonic comparison test block. At this time, a detection instrument with ultrasonic full focusing performance is required.

[0059] S170: Place the probe in the inspection area for inspection, use a grid scanning method during the inspection, and generate a C-scan and a 3D view.

[0060] Place the probe at the corrosion location, connect the ultrasonic full-focus detection instrument and the two-dimensional encoder, and use the full-focus software for acquisition. The software can directly generate C-scans and 3D views.

[0061] S180: Identify defects in the C-scan view and the 3D view.

[0062] The detection position is determined through the above steps.

[0063] Based on the above method, the present invention firstly makes a pulsed eddy current test reference block and an ultrasonic comparison test block according to the pipe material, size and wall thickness, see the attached Figure 2 , used to verify the detection sensitivity. The pulse eddy current reference test block should be processed into flat-bottom holes of different areas. The specific specifications and dimensions of the flat-bottom hole should at least include the indicated dimensions detected by the magnetic leakage detection. It should also include the flat-bottom hole size of 50% of the volume of this size. According to the reference test block to be tested, prepare the same thickness of the lift-off flexible pad at the same time, and select a suitable probe. At least a flat-bottom hole equivalent to the magnetic leakage indication should be found. If the sensitivity is met, a larger size probe and array probe should be selected. Probe footprint size range: 22mm-46mm, power: 10W-20W; pulse width: 10ms-30ms; pulse frequency: 5Hz-20Hz; A scan start time: 1.5ms-5ms; A scan duration: 10ms-30ms.

[0064] Due to the limitation of low detection accuracy brought by pulsed eddy current detection, it is impossible to determine a suitable probe to complete high-precision detection. The present invention can preliminarily determine the probe to be used based on the pulsed eddy current detection reference test block through the above method, so that the preliminarily determined probe can meet the range of corrosion positions, and then further determine the accuracy of the probe. The pulsed eddy current of the present invention selects an array probe.

[0065] After the probe is preliminarily determined, the probe is verified to obtain an accurate probe that meets the conditions of the pipeline to be inspected. In this step, before ultrasonic testing, a model is first built based on the size, material and wall thickness of the pipeline to be inspected, and the sound field is simulated using CIVA simulation software. During the simulation, the corrosion defect response can be simulated. For thin-walled pipelines, a dual-line array probe should be selected. For small-size pipe inspection, a self-focusing line array probe should be selected. For thick-walled pipelines, a line array probe should be selected. Detection frequency (generally recommended is 5MHz-10MHz). Probe chip size pitch (0.3mm-0.6mm), probe passive aperture size: 7.5mm-15mm, self-focusing size: (5mm-30mm). Place the probe selected by the simulation results on the ultrasonic comparison test block. See the schematic diagram of the ultrasonic comparison test block. Figure 3 The ultrasonic comparison test block has the same size, material and wall thickness as the pipeline to be tested. Spherical holes with different defects are set on the inner wall of the ultrasonic comparison test block. Its function is to use a determined probe to scan and detect the defects of the reference test block to determine the accuracy of the probe. Since the ultrasonic comparison test block is the same as the pipeline to be tested, when the scanning and detection of the ultrasonic comparison test block is completely accurate, it means that the determined probe meets the conditions and can be used to scan underground pipelines, and the results obtained after scanning are also accurate. If the scanning and detection results of the ultrasonic comparison test block deviate from the defects set in the ultrasonic comparison test block, that is, when the results are inaccurate, the probe cannot be used to detect underground pipelines, and the probe needs to be further verified until an accurate probe is obtained. The probe verified and determined by the present invention uses a single-line scanning method to detect each spherical hole in the ultrasonic comparison test block in turn. The full focusing method should be able to detect the signal of each spherical hole and effectively identify its contour. It is used to ensure that its detection sensitivity can meet the detection requirements. The full focus mode can be FMC full matrix capture, PWI plane wave imaging and PCI phase coherent imaging mode. The depth of the focus area should be slightly greater than twice the plate thickness, and the width should be equivalent to the length of the probe. The pixel resolution of the focus area is 0.01mm-0.02mm. When performing full focus phased array detection, it is advisable to select grid scanning to form the final C scan and 3D view, and determine the thinnest detection area in the 3D view.

[0066] Based on the above implementation modes, in the pipeline corrosion detection, the present invention adopts flat-bottom holes of different areas and the same depth to calibrate the pulsed eddy current detection process, and adopts spherical holes of different depths and the same size to verify the detection sensitivity of the fully focused phased array probe, and then applies the simulation technology to optimize the detection parameters of the fully focused probe. Finally, the optimized fully focused probe is applied to the corrosion point detection of the pipeline to improve the detection accuracy.

[0067] Example

[0068] In this embodiment, the corrosion points of the 508×6.3 pipeline are excavated for verification.

[0069] According to the pipe size and material, pulsed eddy current test reference blocks and ultrasonic comparison blocks of the same size are made respectively, and defects of corresponding sizes are processed on the test blocks, which are mainly used for pulsed eddy current and ultrasonic fully focused phased array sensitivity calibration.

[0070] Pulse eddy current detection was carried out on the pulse eddy current test block. The selected probe model was PECA-6CH-MED-H05S, which is an array probe with a footprint size of 46mm. The detection parameters were as follows: maximum power: 10W; pulse width: 23.9ms; pulse frequency: 14.13Hz; A-scan start time: 2.1ms; and duration: 22.6ms.

[0071] This detection technology is applied to pipeline inspection, and pulse eddy current imaging software is used to form C-scan imaging to find the specific location of corrosion.

[0072] CIVA simulation is performed based on the pipe size, wall thickness and material to determine the acoustic field distribution and defect echo in the defect area. The probe type, frequency and number of chips are determined.

[0073] The probe parameters after simulation in this embodiment are: pitch: 0.5 mm, number of chips: 64, passive aperture: 10 mm, wedge height: 10 mm, self-focusing radius: 25 mm, focusing area: 50 mm×15 mm, resolution: 0.02 mm, focusing law: FMC, mode: LL.

[0074] The probe of the simulation result is applied to the ultrasonic comparison test block. The probe should be able to clearly display the outlines of all defects in the ultrasonic comparison test block. This shows that the simulation result is accurate. Place the probe in the test area for testing. The grid scanning method is used during the test, and a C-scan and 3D view are generated. Place the probe at the corrosion position, use the full focus software for acquisition, and directly generate a C-scan and 3D view. Identify the defects in the C-scan view and the 3D view. Finally determine the test position.

[0075] The verification results of this example are as follows:

[0076] Figure 5The pulse eddy current test results of the pulse eddy current test block are shown in Figure 2.

[0077] In the C-scan test results of the pulsed eddy current test plate, the selected probe and parameters can effectively identify the corrosion defects in the test block. The normal wall thickness value is displayed in blue, while the defective parts are displayed in red and yellow. Red indicates large-area corrosion, while yellow indicates small-area corrosion.

[0078] Figure 6 This is the CIVA probe acoustic field simulation result. It shows that:

[0079] In the CIVA acoustic field simulation results, the distribution range of the acoustic field energy can be intuitively displayed. The blue represents the concentrated area of ​​the acoustic field energy, which means that we pay more attention to deeper corrosion during detection. This allows for higher detection accuracy, and even small but deep defects will not be missed.

[0080] Figure 7 The simulation results of different defects detected by the probe are shown in Figure 2.

[0081] The figure shows the simulation result of a flat-bottom hole defect, which is used to detect defects with a certain corrosion depth to ensure its detection sensitivity and detection resolution. It can be seen from the simulation results that the bottom surface echo and defect echo (displayed in red) can be effectively displayed. At the same time, it can be observed that the defect display outline is clear and easy to distinguish and measure.

[0082] Figure 8 The results of on-site pipeline pulse eddy current testing are shown below.

[0083] The results of on-site pipeline pulse eddy current testing showed that large-area screening was carried out using pulse eddy current under the condition of an insulation layer. It was found that the area where the blue transitioned to green and finally to yellow was the corrosion area.

[0084] Fig. 9 is the phased array detection result. It shows that:

[0085] The pulsed eddy current was used to determine the defective area, and the anti-corrosion layer was stripped and polished. The phased array scanning was performed using the detection process determined by the simulation. The obtained C-scan image is as follows: Fig. 9 As shown, the results on the left and right sides are depth views and amplitude views, both of which can clearly show the morphology, size and location information of the defects.

[0086] Fig.10 This is a 3D view of the phased array. It shows:

[0087] The phased array test results are converted into 3D views to form a 3D view display of the scanning position, which makes the display results more intuitive.

[0088] The above implementation modes are only used for understanding the technical solutions of the present invention, and are not used to limit the protection scope of the present invention. Any obvious adjustments and modifications made to the technical concepts of the present invention should also fall within the protection scope of the present invention.

Claims

1. A detection method for corrosion excavation verification of long-distance oil and gas pipelines, characterized in that The following steps are involved: S110: According to the material of the pipeline to be inspected, the same pulsed eddy current test reference block and ultrasonic comparison test block are made to measure the longitudinal wave sound velocity and pulsed eddy current calibration; Defects of corresponding sizes are machined on the pulsed eddy current test reference block and the ultrasonic comparison test block; S120: Select the appropriate pulsed eddy current probe according to the size, material, thickness and anti-corrosion layer thickness of the pipeline to be inspected; S130: Verify pulsed eddy current probes and instruments using pulsed eddy current test reference blocks; Connect the selected probe to the pulsed eddy current tester, place the probe on a pulsed eddy current test reference block with a flexible pad whose thickness is equal to the thickness of the anti-corrosion layer, and select appropriate excitation voltage, A-scan start time, and A-scan duration parameters to ensure that the process can identify corrosion; S140: Find the corrosion area in the pulsed eddy current C scan view; Apply the verified pulsed eddy current probe to the pipeline inspection, use the pulsed eddy current imaging software to form a C-scan image to find the specific location of the corrosion; S150: Perform CIVA simulation based on the pipe size, wall thickness and material to determine the acoustic field distribution in the defect area, defect echo, probe type, frequency and number of chips; CIVA simulation software is used to perform acoustic field and sensitivity simulation analysis on the size and material of the pipe to be inspected, as well as the size of the corrosion to be inspected, to determine the probe type, frequency and number of chips. When inspecting thinner workpieces, a dual-line array probe and a higher frequency are selected. When the workpiece is thicker, a linear array probe is selected with 64 chips. S160: The simulation probe is applied to the ultrasonic comparison test block. The probe should be able to identify all defects of the ultrasonic comparison test block and effectively identify the defect contour; S170: placing the probe in the detection area for detection, using a grid scanning method, and generating a C-scan and a 3D view; S180: Identify defects in the C-scan view and the 3D view, and determine the inspection position.

2. The detection method for corrosion excavation verification of long-distance oil and gas pipelines according to claim 1 is characterized by: In step S110, pulsed eddy current detection reference blocks and ultrasonic comparison blocks are manufactured according to the pipe material, size and wall thickness to verify the detection sensitivity, wherein the pulsed eddy current reference blocks should be processed into flat-bottom holes of different areas, and the specific specifications and dimensions of the flat-bottom holes should at least include the indicated dimensions detected by magnetic leakage detection, and should also include the flat-bottom hole dimensions that are 50% of the volume of the dimension.

3. The detection method for corrosion excavation verification of long-distance oil and gas pipelines according to claim 1 is characterized by: In step S130, based on the pulse eddy current detection reference block to be tested, a lift-off flexible pad with the same thickness as the anti-corrosion layer of the tested pipeline is prepared at the same time. The probe selected on the pulse eddy current detection reference block of the flexible pad should at least be able to find a flat-bottomed hole equivalent to the leakage magnetic indication. While meeting the sensitivity, a larger size probe and an array probe are selected. The probe footprint size range is: 22mm-46mm, power: 10W-20W; pulse width: 10ms-30ms; pulse frequency: 5Hz-20Hz; A scan start time: 1.5ms-5ms; A scan duration: 10ms-30ms.

4. The detection method for corrosion excavation verification of long-distance oil and gas pipelines according to claim 1 is characterized by: In step S150, before ultrasonic testing, a model should be built according to the size, material and wall thickness of the pipeline to be tested, and the sound field should be simulated using CIVA simulation software. During the simulation, the corrosion defect response can be simulated. A dual linear array probe is selected for thin-walled pipelines, a self-focusing linear array probe is selected for small-size pipe detection, and a linear array probe is selected for thick-walled pipelines. The detection frequency is 5MHz-10MHz, the probe chip size is 0.3mm-0.6mm, the probe passive aperture size is 7.5mm-15mm, and the self-focusing size is 5mm-30mm.

5. The detection method for corrosion excavation verification of long-distance oil and gas pipelines according to claim 1 is characterized by: In step S160, the probe selected by the simulation result is placed on the ultrasonic comparison test block. The ultrasonic comparison test block should be processed into spherical holes of different depths. A single-line scanning method is used to detect each spherical hole in the reference test block in turn. The full focusing method should be able to detect the signal of each spherical hole and effectively identify its contour to ensure that its detection sensitivity can meet the detection requirements.

6. The detection method for corrosion excavation verification of long-distance oil and gas pipelines according to claim 5 is characterized by: The full focusing mode is FMC full matrix capture, PWI plane wave imaging or PCI phase coherence imaging mode. The depth of the focus area should be greater than twice the plate thickness, and the width should be the same as the probe length. The pixel resolution of the focus area is 0.01mm-0.02mm.

7. The detection method for corrosion excavation verification of long-distance oil and gas pipelines according to claim 1 is characterized by: In step S170, grid scanning is preferably selected during full-focus phased array detection to form a final C-scan and 3D view, and the thinnest detection area is further determined in the 3D view.

8. A test block for use in the detection method for verifying corrosion excavation of a long-distance oil and gas pipeline according to any one of claims 1 to 7, characterized in that: It includes a pulse eddy current detection reference test block and an ultrasonic comparison test block made according to the material, size and wall thickness of the inspected pipeline, wherein the pulse eddy current reference test block should be processed into flat-bottom holes of different areas; the inner wall of the ultrasonic comparison test block is provided with spherical holes with different defects.

9. The test block for the detection method for verifying corrosion excavation of long-distance oil and gas pipelines according to claim 8 is characterized by: The specific specifications and dimensions of the flat-bottom hole of the pulsed eddy current testing reference test block at least include the indicated dimensions detected by the magnetic flux leakage detection.

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