Monitoring Method, Device, Equipment and Medium for Stress Corrosion Cracking of Oil Pipe Steel

Abstract

The present disclosure provides a method, apparatus, device, and storage medium for monitoring stress corrosion cracking, belonging to the technical field of metal material failure monitoring. The method includes: acquiring an electrochemical noise signal and an acoustic emission signal of a tubing steel specimen in the downhole environment of an oil displacement well; monitoring pitting events and microcrack initiation events in the first stage of stress corrosion cracking of the tubing steel specimen according to the electrochemical noise signal; and monitoring crack propagation events and crack tearing events in the second stage of stress corrosion cracking of the tubing steel specimen according to the acoustic emission signal. It is possible to monitor corrosion cracking events in the whole process of SCC of the tubing steel specimen, thereby improving the accuracy of SCC monitoring.

Description

Technical Field

[0001] The present disclosure relates to the technical field of metal material failure monitoring, and particularly to a method, device, equipment and medium for monitoring stress corrosion cracking of tubing steel. Background Art

[0002] SCC (Stress Corrosion Cracking) refers to the behaviors such as crack initiation and crack propagation that occur in metal materials under the combined action of stress and corrosive media. In the scenario of oil displacement using CO2 flooding technology, the tubing steel in the oil displacement wellbore is on the one hand strongly corroded by CO2 and sulfur-containing annulus solution in the oil displacement wellbore, and on the other hand is also subjected to its own gravity and the pulling force of the sucker rod. In this case, the tubing steel is prone to SCC. The phenomenon of local perforation or rupture of the tubing steel caused by SCC will cause the leakage of flammable, explosive and toxic media inside the tubing steel, thus triggering catastrophic accidents. Therefore, it is necessary to monitor the SCC of the tubing steel in the oil displacement wellbore in order to timely warn of the fracture risk of the tubing steel and provide protective measures for the tubing steel.

[0003] In the related art, a single electrochemical method, for example, potentiostatic polarization method, potentiodynamic scanning method, electrochemical impedance spectroscopy, electrochemical noise, micro-area electrochemical technology and other methods, or a single acoustic emission method is used to monitor the whole process of SCC of the tubing steel in the oil displacement wellbore.

[0004] Both the single electrochemical method and the single acoustic emission method can only monitor some corrosion cracking events in the whole process of SCC of the tubing steel, and it is difficult to monitor the whole process of SCC of the tubing steel, and the monitoring accuracy of SCC of the tubing steel is low. Summary of the Invention

[0005] Embodiments of the present disclosure provide a method, device, equipment and storage medium for monitoring SCC, which can comprehensively monitor the whole process of SCC of tubing steel to improve the monitoring accuracy of SCC of tubing steel. The technical solutions are as follows:

[0006] In a first aspect, a method for monitoring stress corrosion cracking of tubing steel is provided. The method includes:

[0007] Obtain the electrochemical noise signal and acoustic emission signal of the tubing steel specimen under the simulated downhole environment; monitor the pitting events and microcrack initiation events in the first stage of stress corrosion cracking of the tubing steel specimen according to the electrochemical noise signal; and monitor the crack propagation events and crack tearing events in the second stage of stress corrosion cracking of the tubing steel specimen according to the acoustic emission signal; wherein, the first stage and the second stage are continuous and the first stage occurs before the second stage.

[0008] Optionally, monitoring pitting events and microcrack initiation events in the first stage of stress corrosion cracking of the tubing steel specimen based on the electrochemistry noise signal includes: determining the amplitude and lifetime of the electrochemistry noise signal peaks; and monitoring the pitting events and the microcrack initiation events based on the amplitude and the lifetime.

[0009] Optionally, monitoring pitting events and microcrack initiation events in the first stage of stress corrosion cracking of the tubing steel specimen based on the electrochemistry noise signal includes: determining the average integral charge and nucleation rate of the electrochemistry noise signal; and monitoring the pitting events and the microcrack initiation events based on the average integral charge and the nucleation rate.

[0010] Optionally, monitoring crack propagation events and crack tearing events in the second stage of stress corrosion cracking of the tubing steel specimen based on the acoustic emission signal includes: determining the cumulative number and cumulative rate of the acoustic emission signal; and monitoring the crack propagation events and the crack tearing events based on the cumulative number and the cumulative rate.

[0011] Optionally, monitoring crack propagation events and crack tearing events in the second stage of stress corrosion cracking of the tubing steel specimen based on the acoustic emission signal includes: determining the amplitude and duration of the waveform of the acoustic emission signal; and monitoring the crack propagation events and the crack tearing events based on the amplitude and the duration.

[0012] In a second aspect, a monitoring device for stress corrosion cracking of tubing steel is provided, the device including:

[0013] An acquisition module, configured to acquire an electrochemistry noise signal and an acoustic emission signal of a tubing steel specimen in a simulated downhole environment; a monitoring module, configured to monitor pitting events and microcrack initiation events in the first stage of stress corrosion cracking of the tubing steel specimen based on the electrochemistry noise signal; and monitor crack propagation events and crack tearing events in the second stage of stress corrosion cracking of the tubing steel specimen based on the acoustic emission signal; wherein, the first stage is continuous with the second stage and the first stage occurs before the second stage.

[0014] Optionally, the monitoring module is configured to determine the amplitude and lifetime of the waveform of the electrochemistry noise signal; monitor the pitting events and the microcrack initiation events based on the amplitude and the lifetime; or, determine the average integral charge and nucleation rate of the electrochemistry noise signal; and monitor the pitting events and the microcrack initiation events based on the average integral charge and the nucleation rate.

[0015] The monitoring module is further configured to determine the cumulative number and the cumulative rate of the acoustic emission signals; monitor the crack propagation event and the crack tearing event according to the cumulative number and the cumulative rate; alternatively, determine the amplitude and the duration of the waveform of the acoustic emission signals; and monitor the crack propagation event and the crack tearing event according to the amplitude and the duration.

[0016] In a third aspect, a computer device is provided, including: a processor; and a memory for storing instructions executable by the processor; wherein the processor is configured to execute the method as described above.

[0017] In a fourth aspect, a computer-readable storage medium is provided, which, when the instructions stored therein are executed by the processor of a computer device, enables the computer device to execute the method described in the first aspect above.

[0018] In a fifth aspect, a computer program product is provided, including a computer program / instructions, which, when executed by a processor, implement the method described in the first aspect above.

[0019] The beneficial effects brought by the technical solutions provided in the embodiments of the present disclosure are as follows:

[0020] In the embodiments of the present disclosure, by acquiring the electrochemical noise signals and the acoustic emission signals of a tubing steel specimen under a simulated downhole environment, and monitoring the pitting event and the micro-crack initiation event in the first stage of stress corrosion cracking of the tubing steel specimen according to the electrochemical noise, and monitoring the crack propagation event and the crack tearing event in the second stage of stress corrosion cracking of the tubing steel specimen according to the acoustic emission signals, it is possible to monitor the corrosion cracking events in the whole process of SCC of the tubing steel specimen, thereby improving the accuracy of SCC monitoring. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and those of ordinary skill in the art can obtain other drawings without creative efforts based on these drawings.

[0022] Figure 1 is a schematic structural diagram of an SCC monitoring system provided by an embodiment of the present disclosure;

[0023] Figure 2 is a schematic structural diagram of a tubing steel specimen provided by an embodiment of the present disclosure;

[0024] Figure 3 is a flowchart of an SCC monitoring method provided by an embodiment of the present disclosure;

[0025] Figure 4 is a flowchart of another SCC monitoring method provided by an embodiment of the present disclosure;

[0026] Figure 5 is a schematic diagram of an electrochemical noise signal peak provided by an embodiment of the present disclosure;

[0027] Figure 6 is a schematic diagram of a slow-stretching curve and a corresponding electrochemical noise signal provided by an embodiment of the present disclosure;

[0028] Figure 7 is a schematic diagram of another electrochemical noise signal provided by an embodiment of the present disclosure;

[0029] Figure 8 is a schematic diagram of a slow-stretching curve and a corresponding acoustic emission impact cumulative curve provided by an embodiment of the present disclosure;

[0030] Figure 9 is a schematic diagram of a burst-type acoustic emission signal waveform provided by an embodiment of the present disclosure;

[0031] Figure 10 is a schematic diagram of a continuous-type acoustic emission signal waveform provided by an embodiment of the present disclosure;

[0032] Figure 11 is a structural block diagram of an SCC monitoring device provided by an embodiment of the present disclosure;

[0033] Figure 12 is a structural block diagram of a computer device provided by an embodiment of the present disclosure. Detailed implementation manners

[0034] To make the objectives, technical solutions, and advantages of the present disclosure clearer, the following will further describe the embodiments of the present disclosure in detail with reference to the accompanying drawings.

[0035] Figure 1 is a structural schematic diagram of an SCC monitoring system provided by an embodiment of the present disclosure. As Figure 1 shown, the SCC monitoring system includes a tubing steel specimen (working electrode) 10, an electrochemical noise device 20, an acoustic emission device 30, a computer device 40, and a container 50.

[0036] Among them, the material of the tubing steel specimen 10 can be P110 tubing steel, N80 tubing steel, Super 13Cr tubing steel, etc.

[0037] The container 50 is used to contain a corrosion solution. Exemplarily, the corrosion solution is a 3.5% NaCl solution, the pH of which is adjusted to 2 with hydrochloric acid, and the temperature is 50 °C to simulate the corrosion environment of the tubing steel specimen 10 in the oil displacement well.

[0038] Both ends of the tubing steel specimen 10 are connected to a tensile device, which is used to apply stress tension to both ends of the tubing steel specimen 10 to simulate the stress situation of the tubing steel specimen 10 in the oil displacement well. Exemplarily, the tensile device is a slow tensile testing machine.

[0039] The electrochemical noise device 20 is used to collect the electrochemical noise signals of the tubing steel specimen 10, and the electrochemical noise signals include current noise signals and potential noise signals. The acoustic emission device 30 is used to collect the acoustic emission signals of the tubing steel specimen 10.

[0040] The electrochemical noise device 20 includes a counter electrode 21, a reference electrode 22, and an electrochemical noise meter 23. Among them, the counter electrode 21 is made of the same material as the tubing steel specimen 10. Figure 1 Only one counter electrode 21 is taken as an example for illustration. In practical applications, there are multiple counter electrodes 21, and they are evenly distributed around the tubing steel specimen 10 to ensure uniform polarization of the surface of the tubing steel specimen 10. Exemplarily, there are 4 counter electrodes 21. The galvanic current between the counter electrode 21 and the tubing steel specimen 10 is the current noise signal of the tubing steel specimen 10. The reference electrode 22 is a saturated calomel electrode. The potential between the tubing steel specimen 10 and the reference electrode 22 is the potential noise signal of the tubing steel specimen 10. The electrochemical noise meter 23 is used to transmit the current noise signal and potential noise signal of the tubing steel specimen 10 to the computer 40. Exemplarily, the electrochemical noise meter 23 adopts the CST500 electrochemical noise meter of Wuhan Kest Company.

[0041] In the embodiments of the present disclosure, the tubing steel specimen 10, the counter electrode 21, and the reference electrode 22 are all placed in the container 50.

[0042] The acoustic emission device 30 includes an AE (Acoustic Emission) sensor 31 and an acoustic emission collector 32. The AE sensor is used to collect the acoustic emission signals of the tubing steel specimen 10 and convert the acoustic emission signals into electrical signals. Exemplarily, the model of the AE sensor is R15α (frequency range: 50 kHz to 200 kHz). The acoustic emission collector 32 is used to amplify and process the electrical signals obtained by the AE sensor and then transmit them to the computer 40. Exemplarily, the acoustic emission device 30 adopts the USB AE Node device produced by American Acoustic Physics Company.

[0043] The computer device 40 is used to monitor the SCC process of the tubing steel specimen 10 according to the obtained electrochemical noise signals and acoustic emission signals. Exemplarily, the computer device 40 can be a computer, etc.

[0044] Figure 2 It is a schematic structural diagram of a tubing steel specimen provided by the embodiments of the present disclosure, as Figure 2As shown, there are grooves 1 at both ends of the tubing steel specimen 10. The AE sensor 31 is coupled with the grooves 1 at both ends of the tubing steel specimen 10 using vacuum silicone grease, and the AE sensor 31 is fixed on the surface of the tubing steel specimen 10 through a fixture.

[0045] Figure 3 is a flowchart of a method for monitoring SCC provided by an embodiment of the present disclosure. This method can be executed by Figure 1 the computer device 40 in. Refer to Figure 3 , this method includes:

[0046] In step 101, obtain the electrochemical noise signal and acoustic emission signal of the tubing steel specimen under a simulated downhole environment.

[0047] The simulated downhole environment refers to simulating the corrosion environment and stress conditions of the tubing steel specimen in an oil displacement well. For relevant content, refer to the Figure 1 embodiment shown, and detailed description is omitted here.

[0048] The electrochemical noise signal includes a current noise signal and a potential noise signal, which are collected by the Figure 1 electrochemical noise device 20 in. The acoustic emission signal is collected by the Figure 1 acoustic emission device 30 in.

[0049] In step 102, monitor the pitting events and microcrack initiation events in the first stage of SCC of the tubing steel specimen according to the electrochemical noise signal.

[0050] The first stage of SCC of the tubing steel specimen includes pitting events and microcrack initiation events.

[0051] In step 103, monitor the crack propagation events and crack tearing events in the second stage of SCC of the tubing steel specimen according to the acoustic emission signal.

[0052] The second stage of SCC of the tubing steel specimen includes crack propagation events and crack tearing events.

[0053] The first stage in step 102 occurs before the second stage. The first stage starts from the occurrence of pitting on the tubing steel specimen and ends at the starting point of the first crack propagation event of the tubing steel specimen. The second stage starts from the starting point of the first crack propagation event of the tubing steel specimen and ends at the fracture of the tubing steel specimen. After the tubing steel specimen fractures, no electrochemical noise signal and acoustic emission signal can be monitored. In the embodiment of the present disclosure, the obtained electrochemical noise signal and acoustic emission signal are signals of the entire process of SCC of the tubing steel specimen. The starting point of the first crack propagation event can be determined from the electrochemical noise signal graph and acoustic emission signal graph of the entire process of SCC of the tubing steel specimen, and this starting point is used as the demarcation point between the first stage and the second stage.

[0054] In the embodiments of the present disclosure, an electrochemical noise signal and an acoustic emission signal of a tubing steel specimen under a simulated downhole environment are obtained. Moreover, according to the electrochemical noise, pitting events and microcrack initiation events in the first stage of stress corrosion cracking of the tubing steel specimen are monitored, and according to the acoustic emission signal, crack propagation events and crack tearing events in the second stage of stress corrosion cracking of the tubing steel specimen are monitored, so that corrosion cracking events in the whole process of SCC of the tubing steel specimen can be monitored, thereby improving the accuracy of SCC monitoring.

[0055] Figure 4 is a flowchart of another SCC monitoring method provided by the embodiments of the present disclosure, which is applied to Figure 1 the stress corrosion cracking monitoring system shown in. Refer to Figure 4 and the method includes:

[0056] In step 201, an electrochemical noise signal and an acoustic emission signal of a tubing steel specimen under a simulated downhole environment are obtained.

[0057] For the relevant content of the electrochemical noise signal and the acoustic emission signal, refer to the foregoing step 101, and the detailed description is omitted here.

[0058] In the embodiments of the present disclosure, the tubing steel specimen is placed in an NaCl solution to simulate the corrosion environment of the tubing steel specimen in the oil displacement well; and the two ends of the tubing steel specimen are stretched by a stretching device to simulate the stress condition of the tubing steel specimen in the oil displacement well. That is to say, by simulating the environment in which SCC occurs in the oil displacement well for the tubing steel specimen, an electrochemical noise signal and an acoustic emission signal are induced in the tubing steel specimen, and then the whole process of SCC of the tubing steel specimen is monitored according to the electrochemical noise signal and the acoustic emission signal.

[0059] In some embodiments, the device parameters of the electrochemical noise device are set as: frequency 5 Hz to collect the electrochemical noise signal of the tubing steel specimen. The device parameters of the acoustic emission device are set as: threshold value 27 dB, sampling rate 2 MPS, 2048 points are recorded for each waveform, pre-trigger pre-storage time 40 μs, impact definition time 400 μs, peak definition time 200 μs, impact lock time 200 μs, and analog filter 100 K - 400 KHz to collect the acoustic emission signal of the tubing steel specimen. The electrochemical noise device and the acoustic emission device start collecting signals simultaneously.

[0060] In step 202, the amplitude and lifetime of the waveform of the electrochemical noise signal are determined.

[0061] Figure 5 is a schematic diagram of a peak of the electrochemical noise signal provided by the embodiments of the present disclosure, as shown in Figure 5As shown, the black solid line in the figure represents a single current noise peak or a single voltage noise peak. The amplitude of the waveform of the electrochemical noise signal refers to the amplitude of a single current noise peak and the amplitude of a single potential noise peak. For example Figure 5 the AB segment in Figure 5 . The lifetime of the electrochemical noise signal refers to the difference between the start time and the end time of a single current noise peak and the difference between the start time and the end time of a single potential noise peak. For example the CD segment in

[0062] . The amplitude and lifetime of the waveform of the electrochemical noise signal are automatically calculated by relevant software, such as OriginPro.

[0063] In step 203, according to the amplitude and lifetime of the waveform of the electrochemical noise signal, the pitting corrosion events and microcrack initiation events in the first stage of SCC of the oil pipe steel are monitored.

[0064] Figure 6 is a schematic diagram of a slow stretching curve and an electrochemical noise signal provided by an embodiment of the present disclosure. While stretching both ends of the oil pipe steel sample, the slow stretching curve 1 of the stress borne by the oil pipe steel sample changing with time, the curve 2 of the current noise signal generated by the oil pipe steel sample changing with time, and the curve 3 of the potential noise signal generated by the oil pipe steel sample changing with time can be obtained synchronously.

[0065] According to the slow tensile curve 1, the deformation process of the tubing steel specimen under stress can be divided into four stages: stage I elastic stage, stage II yield stage, stage III hardening stage, and stage IV necking stage. These four stages are a continuous process in time. Among them, stage I elastic stage is the stage where the strain is linearly related to the stress. In this stage, the tubing steel specimen undergoes elastic deformation. When the stress applied to both ends of the tubing steel specimen is removed, the deformation generated by the tubing steel specimen also disappears. Stage II yield stage is the stage where, after the stress borne by the tubing steel specimen exceeds the elastic limit, in addition to elastic deformation, plastic deformation also occurs. In this stage, the stress and strain are no longer linearly related. In stage III hardening stage, since the metal material has enhanced its ability to resist deformation after the yield stage, it is necessary to continue to increase the stress to make the tubing steel specimen continue to deform. In stage IV necking stage, when the stress applied to the tubing steel specimen reaches the strength limit of the tubing steel specimen, plastic deformation begins to occur at the weakest part of the tubing steel specimen, resulting in a sharp necking of the local cross-section of the tubing steel specimen, a rapid reduction in the area that can bear stress, and a rapid decrease in the stress borne by the tubing steel specimen until it fractures.

[0066] Ideally, if the slow tensile curve of the tubing steel specimen in the oil displacement well can be obtained, the deformation state of the tubing steel specimen can be monitored according to this slow tensile curve, and then it can be judged whether the tubing steel specimen fails due to fracture. However, when the tubing steel specimen is in the environment of the oil displacement well, the slow tensile curve of the tubing steel specimen cannot be measured. Therefore, other methods are needed to monitor the state of the tubing steel specimen in the oil displacement well.

[0067] Figure 6 Among the four stages, the characteristics of the current noise signal and the potential noise signal in each stage are different. According to the characteristics of the current noise signal and the potential noise signal, the corrosion cracking events occurring in the tubing steel specimen in each stage can be judged, and then the development process of SCC of the tubing steel can be monitored.

[0068] As Figure 6 shown, in stage I, it is monitored that the tubing steel specimen begins to appear current noise peaks with amplitudes in the first current amplitude range and lifetimes in the first time range, such as the current noise peak labeled a in stage I, and potential noise peaks with amplitudes in the first potential amplitude range and lifetimes in the first time range, such as the potential noise peak labeled b in stage I. This indicates that in stage I, metastable pitting events occurred in the tubing steel specimen. Exemplarily, the first current amplitude range is 1 μA to 30 μA, the first potential amplitude range is 1 mV to 10 mV, and the first time range is 1 s to 5 s.

[0069] Since the generation of metastable pitting causes the potential noise on the surface of the tubing steel specimen to shift negatively and the current noise to shift positively, and the metastable pitting will passivate in a very short time, causing the potential noise on the surface of the tubing steel specimen to shift positively and the current noise to shift negatively, this rapid and continuous change process corresponds to the characteristics of the current noise peak and voltage noise peak in Stage I. It indicates that in Stage I, metastable pitting events occurred on the tubing steel specimen.

[0070] In Stage II, current noise peaks with amplitudes in the second current amplitude range and lifetimes in the second time range were monitored on the tubing steel specimen, such as the current noise peak labeled c in Stage II, and potential noise peaks with amplitudes in the second potential amplitude range and lifetimes in the second time range, such as the potential noise peak labeled d in Stage II. It indicates that in Stage II, microcrack events occurred on the tubing steel specimen. Exemplarily, the second current amplitude range is 1 μA to 20 μA, the second potential amplitude range is 1 mV to 20 mV, and the second time range is 10 s to 100 s.

[0071] In Stage III, current noise peaks with amplitudes in the second current amplitude range and lifetimes in the second time range were monitored on the tubing steel specimen, such as the current noise peak labeled e in Stage III, and potential noise peaks with amplitudes in the second potential amplitude range and lifetimes in the second time range, such as the potential noise peak labeled f in Stage III; there were also current noise peaks with amplitudes in the third current amplitude range and lifetimes in the third time range, such as the current noise peak labeled g in Stage III, and potential noise peaks with amplitudes in the third potential amplitude range and lifetimes in the third time range, such as the potential noise peak labeled h in Stage III. It indicates that in Stage III, both microcrack events and stable pitting events occurred on the tubing steel specimen. Exemplarily, the third current amplitude range is 10 μA to 30 μA, the third potential amplitude range is 5 mV to 20 mV, and the third time range is 5 s to 10 s.

[0072] In Stage IV, current noise peaks with amplitudes in the first current amplitude range and lifetimes in the first time range were monitored on the tubing steel specimen, such as the current noise peak labeled i in Stage IV, and potential noise peaks with amplitudes in the first potential amplitude range and lifetimes in the first time range, such as the potential noise peak labeled j in Stage IV. It indicates that in Stage IV, the main events occurring on the surface of the tubing steel specimen are metastable pitting events. In fact, in Stage IV, the SCC of the tubing steel specimen may have progressed to the second stage, and the main events occurring are crack tearing events and crack propagation events.

[0073] The first current amplitude range, the second current amplitude range, and the third current amplitude range may partially overlap, and the first potential amplitude range, the second potential amplitude range, and the third potential amplitude range may partially overlap. The upper limit value of the first duration range is less than or equal to the lower limit value of the third duration range, and the upper limit value of the third duration range is less than or equal to the lower limit value of the second duration range. The first current amplitude range, the second current amplitude range, the third current amplitude range, the first potential amplitude range, the second potential amplitude range, the third potential amplitude range, the first duration range, the second duration range, and the third duration range are set by relevant technicians according to experience. It should be noted that Figure 6 Both the current noise peak and the potential noise peak in Figure 5 are in the form of

[0074] Figure 7 FIG. is a schematic diagram of another electrochemical noise signal provided by an embodiment of the present disclosure, which is obtained by magnifying the graph of the electrochemical noise signal in a certain time period in Figure 6 . As shown in Figure 7 , the noise peaks in the figure can be current noise peaks or potential noise peaks. The noise peak labeled i represents a metastable pitting event, the noise peak labeled ii represents a stable pitting event, and the noise peak labeled iii represents a microcrack event. The lifetime of the noise peak corresponding to the metastable pitting event is less than the lifetime of the noise peak corresponding to the stable pitting event, and the lifetime of the noise peak corresponding to the stable pitting event is less than the lifetime of the noise peak corresponding to the microcrack event.

[0075] Since the electrochemical noise device is sensitive to the weak current noise signal or weak voltage noise signal generated by the pitting event or microcrack event, and is insensitive to the strong current noise signal or voltage noise signal generated by the crack propagation event or crack tearing event. Therefore, in stage IV, crack tearing and crack propagation events cannot be monitored. That is, the electrochemical noise signal collected by the electrochemical noise signal acquisition device is more suitable for monitoring the first stage of SCC.

[0076] In the embodiment of the present disclosure, since the electrochemical noise device is sensitive to the current noise signal and potential noise signal generated by the pitting event and microcrack event in the first stage of SCC, therefore, monitoring the first stage of SCC through the electrochemical noise signal is relatively accurate.

[0077] Optionally, in the embodiment of the present disclosure, steps 202 and 203 can also be replaced by: determining the average integral charge and nucleation rate of the electrochemical noise signal; and monitoring the pitting event and microcrack initiation event in the first stage of SCC of the tubing steel specimen according to the average integral charge and nucleation rate.

[0078] Wherein, the nucleation rate represents the number of current noise peaks per unit time.

[0079] In the embodiments of the present disclosure, the average charge of the electrochemical noise signal is calculated using Equation (1), and Equation (1) is as follows:

[0080]

[0081] In Equation (1), represents the electrochemical noise signal, T represents the test duration of the electrochemical noise device; t n and t n ' respectively represent the initial and termination times of the nth noise peak; i n (t) represents the function of the current noise signal corresponding to the nth noise peak varying with time t; i b is the baseline current of the noise peak; λ represents the nucleation rate, with the unit of s -1 .

[0082] In the embodiments of the present disclosure, according to the average integrated charge and the nucleation rate, the pitting events and microcrack initiation events in the first stage of SCC of the tubing steel specimen are monitored, including: when λ is less than the first rate threshold, is less than the first integrated charge threshold, it indicates that no corrosion cracking event has occurred in the tubing steel specimen; when λ increases monotonically and is less than the second rate threshold, value increases monotonically and is less than the second integrated charge threshold, it indicates that a metastable pitting event has occurred in the tubing steel specimen; when λ increases monotonically and is less than the third rate threshold, value increases monotonically and is less than the third integrated charge threshold, it indicates that a microcrack event has occurred on the tubing steel specimen. Among them, the first rate threshold is less than the second rate threshold, and the second rate threshold is less than the third rate threshold. The first integrated charge threshold is less than the second integrated charge threshold, and the second integrated charge is less than the third integrated charge threshold. The first rate threshold, the second rate threshold, the third rate threshold, the first integrated charge threshold, the second integrated charge threshold, and the third integrated charge threshold are set by those skilled in the art according to experience.

[0083] Since the electrochemical noise device is sensitive to the current noise signals generated by the pitting events and microcrack events in the first stage of SCC, the average charge calculated from the current noise signals collected by the electrochemical noise device is relatively accurate. Therefore, it is relatively accurate to monitor the pitting events and microcrack events in the early stage of SCC through the average charge.

[0084] Optionally, in the embodiments of the present disclosure, the pitting events and microcrack initiation events in the first stage of SCC of the tubing steel specimen can also be monitored simultaneously according to the amplitude and lifetime of the electrochemical noise signal peaks and the average integrated charge and nucleation rate of the electrochemical noise signal.

[0085] In step 204, according to the cumulative number and cumulative rate of acoustic emission signals, the crack propagation events and crack tearing events in the second stage of SCC are monitored.

[0086] Among them, the cumulative number of acoustic emission signals refers to the number of times that the amplitude of the acoustic emission signal exceeds the threshold amplitude. The threshold amplitude is set for the acoustic emission device by relevant technicians according to experience. The cumulative rate of acoustic emission signals refers to the change amount of the cumulative number of acoustic emission signals per unit time.

[0087] Figure 8 is a schematic diagram of a slow tensile curve and a corresponding acoustic emission cumulative curve provided by an embodiment of the present disclosure. As Figure 8 shown, the curve labeled 1 in the figure is the slow tensile curve, and this curve is the same as the slow tensile curve labeled 1 in Figure 6 . The curve labeled 4 in the figure is the acoustic emission cumulative curve.

[0088] As Figure 8 shown, in stage I, within about 0 to 8 h, as the stress increases, the cumulative number of acoustic emission signals increases from 0 to 2000, and the cumulative rate of acoustic emission signals (the slope of curve 4) also gradually increases. Since the number of oscillations of the acoustic emission signals generated by metastable pitting events is small, the corresponding cumulative number of acoustic emission signals is small. When metastable pitting events occur at multiple locations on the oil pipe steel specimen, the cumulative rate of acoustic emission will increase. Therefore, it can be inferred that in stage I, a large number of metastable pitting events occur on the oil pipe steel specimen.

[0089] In stage II, within about 8 h to 17 h, as the stress increases, the cumulative number of acoustic emission signals increases from 2000 to 2400, and the cumulative rate of acoustic emission signals remains basically unchanged (the slope of curve 4). Since the number of oscillations of the acoustic emission signals generated by stable pitting events is small and more than that of the acoustic emission signals generated by metastable pitting events. Therefore, it can be inferred that in stage II, stable pitting events occur on the oil pipe steel specimen.

[0090] In stage III, within about 17 h to 25 h, as the stress increases, the cumulative number of acoustic emission signals increases from 0 to 3000, and the cumulative rate of acoustic emission signals gradually decreases (the slope of curve 4). Since the number of oscillations of the acoustic emission signals generated by crack propagation events is large, the corresponding cumulative number of acoustic emission signals is high. Therefore, in stage III, crack propagation events occur on the oil pipe steel specimen.

[0091] In Stage IV, approximately after 25 h, as the stress increases, the cumulative number of acoustic emission signals increases from 3000 to 3100, and the cumulative rate of acoustic emission signals remains basically unchanged (the slope of Curve 4). Since the number of oscillations of the acoustic emission signals generated by crack tearing events is large and higher than that of the acoustic emission signals generated by crack propagation events, in Stage IV, crack tearing events occur in the tubing steel specimen.

[0092] Since the acoustic emission device is sensitive to crack propagation events and crack tearing events and can easily monitor crack propagation events and crack tearing events, and the acoustic emission device is insensitive to pitting events and is not easy to monitor pitting events. Therefore, in the embodiments of the present disclosure, it is more accurate to monitor crack propagation events and crack tearing events in the second stage of SCC of the tubing steel specimen according to acoustic emission signals.

[0093] From Figure 6 it can be seen that the electrochemical noise device is difficult to monitor crack propagation events and crack tearing events in the second stage ( Figure 6 Stage IV in) of SCC of the tubing steel specimen, but can monitor a large number of metastable pitting events and stable pitting events in the first stage of SCC of the tubing steel specimen; while the acoustic emission device monitors limited metastable pitting events and stable pitting events in the first stage of SCC of the tubing steel specimen, but can monitor a higher cumulative number of acoustic emissions ( Figure 8 Stages III and IV in) in the second stage of SCC of the tubing steel specimen. Therefore, in the embodiments of the present disclosure, monitoring the first stage of the tubing steel specimen according to electrochemical noise signals and monitoring the second stage of the tubing steel specimen according to acoustic emission signals can monitor the whole process of SCC of the tubing steel specimen and improve the accuracy of SCC monitoring.

[0094] Optionally, in the embodiments of the present disclosure, step 204 can also be replaced by: determining the amplitude and duration of the waveform of the acoustic emission signal; and monitoring crack propagation events and crack tearing events in the second stage of stress corrosion cracking of the tubing steel specimen according to the amplitude and duration.

[0095] Wherein, the amplitude of the acoustic emission signal represents the peak-to-peak value of the acoustic emission signal waveform, and the duration of the acoustic emission signal represents the time experienced from the first time the acoustic emission signal crosses the threshold amplitude to the final drop to the threshold amplitude.

[0096] In the embodiments of the present disclosure, the acoustic emission signals include two types: burst-type acoustic emission signals and continuous-type acoustic emission signals. Figure 9 is a schematic diagram of the waveform of a burst-type acoustic emission signal provided by the embodiments of the present disclosure, as Figure 9As shown, the burst-type acoustic emission signal has a high amplitude, a low frequency, and a short duration. The waveform of the burst-type acoustic emission signal is manifested as an independent damped oscillation curve, representing an independent metastable pitting event or a microcrack event. Figure 10 It is a schematic diagram of a continuous-type acoustic emission signal waveform provided by an embodiment of the present disclosure. As Figure 10 shown, the continuous-type acoustic emission signal has a low amplitude, a high frequency, and a long duration. The continuous-type acoustic emission signal consists of a series of inseparable events, representing the continuous growth of cracks. Therefore, in the embodiments of the present disclosure, the type of the acoustic emission signal can be determined according to the amplitude, frequency, and duration of the acoustic emission signal. When the acoustic emission signal is a continuous-type acoustic emission signal, the crack propagation event and the crack tearing event in the second stage of stress corrosion cracking of the tubing steel specimen are monitored according to the amplitude and duration of the acoustic emission signal.

[0097] In the embodiments of the present disclosure, according to the amplitude and duration of the acoustic emission signal, the crack propagation event and the crack tearing event in the second stage of stress corrosion cracking of the tubing steel specimen are monitored, including: if the amplitude of the continuous-type acoustic emission signal continuously increases and the amplitude is within the first amplitude range, and the duration of the continuous-type acoustic emission signal continuously increases and the duration is within the first set time period, it is determined that a crack propagation event occurs in the tubing steel specimen; if the amplitude of the continuous-type acoustic emission signal continuously increases and the amplitude is within the second amplitude range, and the duration of the continuous-type acoustic emission signal continuously increases and the duration is within the second set time period, it is determined that a crack tearing event occurs in the tubing steel specimen. The upper limit value of the first amplitude range is less than or equal to the lower limit value of the second amplitude range, and the first set time period is less than the second set time period. The first amplitude range, the second amplitude range, the first set time period, and the second set time period are set by those skilled in the art according to experience.

[0098] In the embodiments of the present disclosure, the electrochemical noise signal and the acoustic emission signal of the tubing steel specimen are obtained, and, according to the electrochemical noise signal, the pitting event and the microcrack initiation event in the first stage of stress corrosion cracking of the tubing steel specimen are monitored, and according to the acoustic emission signal, the crack propagation event and the crack tearing event in the second stage of stress corrosion cracking of the tubing steel specimen are monitored, so as to monitor the corrosion cracking events in the whole process of SCC of the tubing steel specimen, thereby improving the accuracy of SCC monitoring.

[0099] In the embodiments of the present disclosure, the possibility of SCC occurring in downhole tubing steel can be reduced by at least one of the following methods:

[0100] Adding an inhibitor to the downhole annulus fluid to reduce the cracking risk caused by the diffusion of hydrogen atoms into the metal interior;

[0101] Improving the stress condition of the tubing steel in the oil displacement well to avoid or reduce local stress concentration;

[0102] Improve the material of the tubing steel and use materials resistant to SCC, such as high-purity austenitic steel, duplex stainless steel, etc.

[0103] Figure 11 It is a structural block diagram of a SCC monitoring device 1100 provided by an embodiment of the present disclosure. As Figure 11 shown, the device includes: an acquisition module 1101 and a monitoring module 1102.

[0104] The acquisition module 1101 is used to acquire the electrochemical noise signal and the acoustic emission signal of the tubing steel specimen under the simulated downhole environment. The monitoring module 1102 is used to monitor the pitting event and the microcrack initiation event in the first stage of stress corrosion cracking of the tubing steel specimen according to the electrochemical noise signal; and monitor the crack propagation event and the crack tearing event in the second stage of stress corrosion cracking of the tubing steel specimen according to the acoustic emission signal; wherein, the first stage is continuous with the second stage and the first stage occurs before the second stage.

[0105] Optionally, the monitoring module 1102 is used to determine the amplitude and lifetime of the peak of the electrochemical noise signal; monitor the pitting event and the microcrack initiation event according to the amplitude and the lifetime; or, used to determine the average integral charge and the nucleation rate of the electrochemical noise signal; monitor the pitting event and the microcrack initiation event according to the average integral charge and the nucleation rate.

[0106] The monitoring module 1102 is further used to determine the cumulative number and the cumulative rate of the acoustic emission signal; monitor the crack propagation event and the crack tearing event according to the cumulative number and the cumulative rate; or, used to determine the amplitude and the duration of the waveform of the acoustic emission signal; monitor the crack propagation event and the crack tearing event according to the amplitude and the duration.

[0107] It should be noted that: when the above-mentioned SCC monitoring device 1100 of the tubing steel provided by the above embodiment monitors the SCC of the tubing steel, only the above-mentioned division of each functional module is used for illustration. In actual application, the above functions can be allocated to different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. In addition, the above-mentioned SCC monitoring device of the tubing steel provided by the above embodiment and the embodiment of the SCC monitoring method of the tubing steel belong to the same concept, and the specific implementation process is detailed in the method embodiment, which will not be repeated here.

[0108] Figure 12 It is a structural block diagram of a computer device provided by an embodiment of the present disclosure. The computer device includes: a processor 1201 and a memory 1202.

[0109] The processor 1201 may include one or more processing cores, such as a quad-core processor, an octa-core processor, etc. The processor 1201 may be implemented in at least one hardware form of DSP (Digital Signal Processing), FPGA (Field-Programmable Gate Array), or PLA (Programmable Logic Array). The processor 1201 may also include a main processor and a coprocessor. The main processor is a processor for processing data in the wake state, also known as the CPU (Central Processing Unit); the coprocessor is a low-power processor for processing data in the standby state. In some embodiments, the processor 1201 may be integrated with a GPU (Graphics Processing Unit), and the GPU is responsible for rendering and drawing the content to be displayed on the display screen. In some embodiments, the processor 1201 may further include an AI (Artificial Intelligence) processor, and the AI processor is used to process computational operations related to machine learning.

[0110] The memory 1202 may include one or more computer-readable storage media, and the computer-readable storage media may be non-transitory. The memory 1202 may further include high-speed random access memory and non-volatile memory, such as one or more disk storage devices and flash storage devices. In some embodiments, the non-transitory computer-readable storage media in the memory 1202 is used to store at least one instruction, and the at least one instruction is used to be executed by the processor 1201 to implement the method for monitoring SCC of oil pipeline steel provided in the embodiments of the present application.

[0111] Those skilled in the art can understand that Figure 12 the structure shown in [[ ]] does not constitute a limitation on the computer device, and may include more or fewer components than shown in the figure, or combine certain components, or adopt a different component layout.

[0112] The embodiment of the present invention also provides a non-transitory computer-readable storage medium. When the instructions in the storage medium are executed by the processor of the computer device, the computer device can execute the method for monitoring SCC of oil pipeline steel provided in the embodiments of the present disclosure.

[0113] A computer program product includes a computer program / instructions, and when the computer program / instructions are executed by the processor, the method for monitoring SCC of oil pipeline steel provided in the embodiments of the present disclosure is implemented.

[0114] The above are only optional embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included within the protection scope of the present disclosure.

Claims

1. A monitoring method for stress corrosion cracking of tubing steel, characterized in that, The method includes: Obtaining an electrochemical noise signal and an acoustic emission signal of a tubing steel specimen under a simulated downhole environment, where the electrochemical noise signal includes a current noise signal and a potential noise signal; Monitoring pitting events and microcrack initiation events in the first stage of stress corrosion cracking of the tubing steel specimen according to the electrochemical noise signal; and Monitoring crack propagation events and crack tearing events in the second stage of stress corrosion cracking of the tubing steel specimen according to the acoustic emission signal; Wherein, the first stage is continuous with the second stage and the first stage occurs before the second stage. The first stage starts from the occurrence of pitting on the tubing steel specimen and ends at the starting point of the first crack propagation event of the tubing steel specimen. The second stage starts from the starting point of the first crack propagation event of the tubing steel specimen and ends at the fracture of the tubing steel specimen. The obtained electrochemical noise signal and acoustic emission signal are signals of the entire process of stress corrosion cracking of the tubing steel specimen. The starting point of the first crack propagation event is determined according to the electrochemical noise signal graph and the acoustic emission signal graph of the entire process of stress corrosion cracking of the tubing steel specimen, and the starting point of the first crack propagation event is used as the demarcation point between the first stage and the second stage.

2. The method according to claim 1, wherein The monitoring of pitting events and microcrack initiation events in the first stage of stress corrosion cracking of the tubing steel specimen according to the electrochemical noise signal includes: Determining the amplitude and lifetime of the peaks of the electrochemical noise signal; Monitoring the pitting events and the microcrack initiation events according to the amplitude and the lifetime.

3. The method according to claim 1, wherein The monitoring of pitting events and microcrack initiation events in the first stage of stress corrosion cracking of the tubing steel specimen according to the electrochemical noise signal includes: Determining the average integral charge and nucleation rate of the electrochemical noise signal; Monitoring the pitting events and the microcrack initiation events according to the average integral charge and the nucleation rate.

4. The method according to any one of claims 1 to 3, characterized in that, The monitoring of crack propagation events and crack tearing events in the second stage of stress corrosion cracking of the tubing steel specimen according to the acoustic emission signal includes: Determining the cumulative number and cumulative rate of the acoustic emission signal; Monitoring the crack propagation events and the crack tearing events according to the cumulative number and the cumulative rate.

5. The method according to any one of claims 1 to 3, characterized in that, The monitoring of crack propagation events and crack tearing events in the second stage of stress corrosion cracking of the tubing steel specimen according to the acoustic emission signal includes: Determining the amplitude and duration of the waveform of the acoustic emission signal; Monitoring the crack propagation events and the crack tearing events according to the amplitude and the duration.

6. A computer device, characterized in that, Includes: A processor; A memory for storing instructions executable by the processor; Wherein, the processor is configured to execute the method according to any one of claims 1 to 5.

7. A computer-readable storage medium, characterized in that, When the instructions in the computer-readable storage medium are executed by the processor of the computer device, the computer device is enabled to execute the method according to any one of claims 1 to 5.

8. A computer program product, comprising a computer program / instructions, characterized in that, The computer program / instructions, when executed by the processor, implement the method according to any one of claims 1 to 5.

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