A deformation monitoring system for oil and gas pipelines in water-sealed tunnels

Abstract

The present invention discloses a water-sealed tunnel oil and gas pipeline deformation monitoring system, including a pipeline deformation monitoring subsystem placed in the tunnel, a data collection and transmission subsystem outside the tunnel, and a monitoring and early warning subsystem located in a monitoring and early warning center. The pipeline deformation monitoring subsystem includes a pipeline macro deformation monitoring device and a pipeline micro deformation monitoring device. The pipeline macro deformation monitoring device is arranged at a location where the pipeline displacement is obvious, and the pipeline micro deformation monitoring device is installed adjacent to the pipeline macro deformation monitoring device to comprehensively analyze the pipeline deformation and stress state. The present invention is based on the principle of controlling key and dangerous parts, reasonably arranges monitoring sections, and the monitoring layout is more scientific and reasonable, with outstanding economy. According to the monitoring results, real-time analysis and solution and early warning information are released, and preventive measures are taken in time, which helps to ensure the safety of pipeline operation. In addition, this monitoring system has no requirements for pipeline operating conditions during installation, does not require pressure reduction, and does not affect the normal operation of oil and gas pipelines.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas pipeline deformation monitoring, and in particular to a water-sealed tunnel oil and gas pipeline deformation monitoring system. Background Art

[0002] River crossing is a key project in the construction of long-distance oil and gas pipelines. In recent years, shield crossing has been widely used to lay oil and gas pipelines when crossing large and medium-sized rivers. Tunnel crossing is divided into two categories: water-sealed tunnels and non-water-sealed tunnels. Water-sealed tunnels are usually used in tunnels with poor water sealing and obvious water seepage on the tunnel wall.

[0003] Unlike buried pipelines, tunnel crossing sections have obvious uphill and downhill sections in their structural design to adapt to the tunnel terrain, and there are large elbow angles at the corners. However, the constraints of the pipelines in the tunnel are limited, and the elbows produce an unbalanced effect under the action of internal pressure, which can easily cause elbow deformation and may cause damage to adjacent pipe clamps and large pipeline displacement. Especially in water-sealed tunnels, due to the deep water depth, the external pressure and buoyancy of water on the pipeline will also cause pipeline deformation and displacement. Water-sealed tunnels are usually operated with water injection and sealing, and personnel cannot enter the tunnel. The pipeline status can only be checked through regular maintenance. Before the maintenance of water-sealed tunnels, personnel must enter the confined space to conduct pipeline safety inspections only after the water is pumped out and fully ventilated. Not only is the project large in volume, the operation cycle is long, and the cost is high, but the changes in water pressure and buoyancy before and after the maintenance are also likely to cause changes in pipeline force, which may threaten the safety of pipeline operation.

[0004] According to the results of regular inspections of several water-sealed tunnels in recent years, the pipeline is subject to the combined effects of bending moment, axial tension and external pressure, which easily produces a large load combination at the turning point of the tunnel, resulting in obvious displacement of the local pipeline, serious deformation of the pipe clamps originally used to fix the pipeline, and even the breakage of the anchor bolts of the pipe clamps, which seriously affects the normal operation of the pipeline. Since each pipeline inspection can only obtain the displacement and deformation state of the pipeline at the time of inspection, and the in-situ state of the pipeline cannot be grasped during operation, especially under conditions such as tunnel water injection, pumping, pressure regulation, and tunnel displacement, it is impossible to obtain the pipeline safety status in real time, and there is great uncertainty and risk. Once the force on the pipeline exceeds the strength of the pipeline material, it will cause accidents such as pipeline leakage and deflagration, and the risk is huge. The pipeline in the tunnel is a high-risk section and should be paid special attention to. Carry out real-time monitoring of oil and gas pipelines in water-sealed tunnels. By monitoring the macroscopic and microscopic deformation of the pipeline, the in-situ state and stress of the pipeline can be grasped. When abnormalities are found, early warning information can be issued in time to prevent pipeline safety accidents. Summary of the invention

[0005] In order to realize the deformation monitoring of pipelines in water-sealed tunnels, the present invention provides a monitoring system for measuring the macro-deformation and micro-deformation of pipelines under water-sealed environments. By long-term monitoring of pipeline displacement and pipeline strain, the in-situ status and stress conditions of underwater pipelines can be accurately grasped, and safety early warnings for oil and gas pipelines in water-sealed tunnels can be carried out based on the monitoring results.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A water-sealed tunnel oil and gas pipeline deformation monitoring system comprises a pipeline deformation monitoring subsystem placed in the tunnel, a data acquisition and transmission subsystem placed outside the tunnel, and a monitoring and early warning subsystem located in a monitoring and early warning center; the pipeline deformation monitoring subsystem comprises a pipeline macro deformation monitoring device and a pipeline micro deformation monitoring device; the data acquisition and transmission subsystem comprises an optical fiber terminal box, an optical fiber grating demodulator, a data transmission module, a lightning protection device, and a power supply device; the monitoring and early warning subsystem is located at a physical server or a cloud server end of the monitoring and early warning center; it comprises a data center for receiving monitoring data and screening data, a data analysis module for carrying out pipeline displacement analysis and pipeline strain / stress analysis, a monitoring and early warning module that integrates pipeline macro displacement deformation and pipeline stress state, and takes pipeline intrinsic safety monitoring and early warning as the core, and issues corresponding early warning information according to the calculated ratio of the maximum values ​​of pipeline axial additional tension and compressive stress to the allowable values ​​of axial additional tension and compressive stress.

[0008] In the above-mentioned water-sealed tunnel oil and gas pipeline deformation monitoring system, the pipeline macro deformation monitoring device includes a special stainless steel pipe clamp, a pipe clamp fixing bolt, an upper adjustment plate, a fiber grating displacement meter connecting rod, a fiber grating displacement meter, a lower adjustment plate, and a ground fixing bolt; the special stainless steel pipe clamp is divided into two semicircles and is fastened to the pipeline surface by the pipe clamp fixing bolt; to prevent the special stainless steel pipe clamp from damaging the pipeline and the three-layer PE anti-corrosion layer, a 6mm thick rubber plate is installed between the pipeline and the stainless steel pipe clamp; on the side close to the tunnel step, the upper adjustment plate is connected to the special stainless steel pipe clamp by the pipe clamp fixing bolt; the lower adjustment plate is fixed to the tunnel ground by the ground fixing bolt, and during installation, ensure that the center lines of the upper adjustment plate and the lower adjustment plate coincide in the vertical direction; the fiber grating displacement meter is installed between the upper adjustment plate and the lower adjustment plate, and the connecting rods at both ends of the grating displacement meter are fastened to the clamping holes of the upper adjustment plate and the lower adjustment plate.

[0009] In the above-mentioned water-sealed tunnel oil and gas pipeline deformation monitoring system, the pipeline micro-deformation monitoring device includes a fiber grating strain gauge, a fiber grating thermometer, a monitoring section protective layer, a single-core armored optical cable, an optical cable protection tube, a tunnel optical cable, and a tunnel optical cable junction box; the fiber grating strain gauge and the fiber grating thermometer are both installed on the surface of the pipeline steel body. During installation, the three-layer PE anti-corrosion layer of the pipeline needs to be partially opened, and the fiber grating strain gauge and the fiber grating thermometer are welded to the pipeline surface using spot welding technology.

[0010] In the above-mentioned water-sealed tunnel oil and gas pipeline deformation monitoring system, after the optical cable leading out of the pipeline macro-deformation monitoring device and the optical cable leading out of the adjacent pipeline micro-deformation monitoring device are connected in series at the top of the pipeline, two single-core armored optical cables are used to weld the ends of the series-connected optical cables to the tunnel optical cable through an optical cable junction box. The single-core armored optical cable is protected by an optical cable protection tube, and sealant is poured into the optical cable junction box to prevent water from seeping in.

[0011] In the above-mentioned water-sealed tunnel oil and gas pipeline deformation monitoring system, a backup channel is designed when the single-core armored optical cable is connected to the tunnel optical cable. When a fault occurs in the series optical cable composed of the pipeline macro-deformation monitoring device and the pipeline micro-deformation monitoring device, part of the sensor data is measured forwardly by one end and the remaining sensor data is measured reversely by the other end to ensure that all sensor data are read normally.

[0012] In the above-mentioned water-sealed tunnel oil and gas pipeline deformation monitoring system, the fiber optic terminal box in the data acquisition and transmission subsystem is used to separate the various optical cables in the tunnel optical cable, so as to facilitate the use of jumpers to connect to each optical cable and read the monitoring data of each optical cable respectively; the fiber optic Bragg grating demodulator is connected to each optical cable through a jumper, and regularly emits a single-wavelength laser to each optical cable, and the emitted laser can vary within a larger wavelength range. At the same time, the return wavelength of the sensor in each optical cable is recorded and stored in the fiber optic Bragg grating demodulator; the data transmission module is used to transmit the monitoring data stored in the fiber optic Bragg grating demodulator to the designated server-side monitoring and early warning subsystem data center; the lightning protection device is used to prevent the integrated field monitoring station in the open field environment from being affected by lightning and causing damage to the on-site equipment and lines; the power supply device is used to power the grating demodulator and the data transmission module to ensure the normal operation of the equipment 24 hours a day.

[0013] In the above-mentioned water-sealed tunnel oil and gas pipeline deformation monitoring system, the monitoring and early warning subsystem, the data center receives the monitoring data and performs data screening, and the data screening is divided into two sub-steps: effective data screening and abnormal data screening; assuming that m data collection commands are issued each time data is collected, and n groups of data are successfully collected, then the n groups of data are sequentially screened for effective data screening and abnormal data screening; effective data screening is to perform preliminary screening on the above n groups of data according to the sensor range, and remove invalid data that exceeds the sensor range, leaving n2 groups of data; abnormal data screening is to take the detection level of the remaining n2 groups of data as 5% according to the Grubbs test method, define the critical value Gp(n2) of the Grubbs test, and calculate the mean of the remaining n2 groups of data in turn. Standard Deviation and the Grubbs test statistic for each group Select the maximum Grubbs test statistic value G among the remaining n2 groups of data k (Gk =max(G i )) for analysis, if G k >Gp(n2) indicates that the kth data is an abnormal value, and the kth data needs to be removed, and the above abnormal data screening process is repeated for the remaining n2=n2-1 groups of data until G k <Gp(n2), indicating that the remaining data are not abnormal values, the remaining data are retained and the average value of the remaining data is taken as the monitoring data after the measurement result value screening, and the data screening is ended at the same time;

[0014] The above-screened monitoring data enters the data analysis module to carry out pipeline displacement analysis and pipeline strain / stress analysis; the pipeline displacement is directly calculated using the monitoring data according to the wavelength and displacement calculation formula under the premise of considering the temperature wavelength; the pipeline strain value at any position of the monitoring section can be calculated based on the three sets of strain data on the monitoring section at the same time after eliminating the temperature effect. The specific calculation steps are as follows:

[0015] The pipeline strain is composed of film strain, y-direction bending strain and z-direction bending strain. Let the film strain of the monitoring section, the maximum y-direction bending strain and the maximum z-direction bending strain be ε m , According to the superposition principle, the strain at any point on the pipe cross section is:

[0016]

[0017] The monitored strain values ​​at the top and left and right sides of the pipeline are U(0,r o ), Its m , The relationship is as follows:

[0018] Formula 2:

[0019] Formula 3:

[0020] Formula 4: The film strain of the monitoring section represented by the monitoring strain and the maximum bending in the y and z directions are obtained from Formula 2-Formula 4 respectively:

[0021] Formula 5:

[0022] Formula 6:

[0023] Formula 7:

[0024] Combining the bending strains in the y and z directions, the maximum bending strain of the cross section can be obtained as follows:

[0025]

[0026] The angle at which the maximum bending strain occurs is, Formula 9:

[0027]

[0028] Accordingly, the maximum and minimum axial strains of the monitoring section are as follows: Formula 10:

[0029]

[0030] The axial strain at any point in the pipe cross section represented by the monitored strain is, Formula 11:

[0031]

[0032] Similarly, the maximum axial strain at each angle of the monitoring section can be obtained from the above formula: Formula 12:

[0033]

[0034] The average axial strain of the monitoring section is, Formula 13:

[0035]

[0036] The bending strain of the monitored section is, Formula 14:

[0037]

[0038] According to the pipeline stress-strain relationship curve, the maximum axial stress, average axial stress, and bending stress values ​​at each angle of the monitoring section are obtained by formula 12-formula 14;

[0039] The monitoring and early warning module in the monitoring and early warning subsystem integrates the pipeline macro-displacement deformation and pipeline stress state, and issues early warning information with pipeline intrinsic safety monitoring and early warning as the core; when the pipeline axial additional tension and compressive stress values ​​reach or exceed 30% of the allowable values ​​of the axial additional tension and compressive stress, a blue early warning information is issued; when the pipeline axial additional tension and compressive stress values ​​reach or exceed 60% of the allowable values ​​of the axial additional tension and compressive stress, a yellow early warning information is issued; when the pipeline axial additional tension and compressive stress values ​​reach or exceed 90% of the allowable values ​​of the axial additional tension and compressive stress, a red early warning information is issued.

[0040] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: the displacement sensor and strain sensor used in the present invention are both passive sensors, and are waterproof and resistant to water pressure, and can be used for long-term underwater monitoring, and are particularly suitable for macro and micro deformation monitoring of oil and gas pipelines in water-sealed tunnels, and will not have adverse effects on underwater pipelines, and can realize real-time online monitoring of pipeline operation process, and the system is also suitable for pipeline deformation monitoring in non-water-sealed tunnels, and can be replaced with vibrating string sensors according to actual needs without adjusting the existing monitoring method, and has a wider range of applications. The present invention is based on the principle of controlling key and dangerous parts, and reasonably arranges monitoring sections, so that the monitoring layout is more scientific and reasonable, and the economy is outstanding. The monitoring and early warning system performs real-time analysis and solution and releases early warning information based on the monitoring results, and takes preventive measures in a timely manner, which helps to ensure the safety of pipeline operations. In addition, this monitoring system has no requirements for pipeline operating conditions during installation, does not require pressure reduction, and does not affect the normal operation of oil and gas pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0042] Figure 1 It is a schematic diagram of the overall structure of the pipeline deformation monitoring system of the present invention.

[0043] Figure 2 It is a schematic diagram of the pipeline macro deformation monitoring device of the present invention.

[0044] Figure 3 It is a schematic diagram of the pipeline micro-deformation monitoring device of the present invention. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Embodiment 1

[0047] In order to monitor the deformation of the oil and gas pipeline in the tunnel crossing section, especially the water-sealed tunnel crossing section, the embodiment of the present invention provides a water-sealed tunnel oil and gas pipeline deformation monitoring system, and is also applicable to the pipeline deformation monitoring of the non-water-sealed tunnel crossing section. The specific technical scheme is as follows:

[0048] like Figure 1As shown, a water-sealed tunnel oil and gas pipeline deformation monitoring system includes a pipeline deformation monitoring subsystem placed in the tunnel, a data acquisition and transmission subsystem placed outside the tunnel, and a monitoring and early warning subsystem located in a monitoring and early warning center.

[0049] The pipeline deformation monitoring subsystem includes a pipeline macro deformation monitoring device and a pipeline micro deformation monitoring device. Before the monitoring is carried out, it is necessary to establish a three-dimensional direction map of the current pipeline in a local coordinate system based on the three-dimensional measurement results of the pipeline centerline on site, and establish a three-dimensional direction map of the pipeline at the time of completion in the same local coordinate system in combination with the pipeline completion drawings; use the finite element method to establish a three-dimensional analysis model of the pipeline at the time of completion and the current pipeline; combined with the on-site investigation, the pipeline constraints at different positions in the tunnel are converted into corresponding constraints and loaded on the three-dimensional analysis model of the pipeline at the time of completion, and internal pressure, external pressure and local loads are applied to the pipeline at the same time. After repeated calculations, the deformation state and stress state of the pipeline when the pipeline position at the time of completion is changed to the current pipeline position; according to the analysis results, select the parts with obvious pipeline deformation and concentrated stress to carry out pipeline macro deformation and micro deformation monitoring. Figure 2 As shown, when the pipeline macro deformation monitoring device is used, it is installed at the place where the displacement and deformation of the pipeline are more obvious. The pipeline micro deformation monitoring device is installed near the pipeline macro deformation monitoring device or at the concentrated stress position of the pipeline to comprehensively monitor the deformation and stress state of the pipeline. The pipeline macro deformation monitoring device includes a special stainless steel pipe clamp 101, a pipe clamp fixing bolt 105, an upper adjustment plate 106, a fiber Bragg grating displacement meter connecting rod 110, a fiber Bragg grating displacement meter 107, a lower adjustment plate 108, and a ground fixing bolt 109. The special stainless steel pipe clamp 101 is divided into two semicircles and is fastened to the pipeline surface by the pipe clamp fixing bolt 105; in order to prevent the special stainless steel pipe clamp 101 from damaging the pipeline 104 and the three-layer PE anti-corrosion layer 103, a 6mm thick rubber plate 102 is installed between the pipeline 104 and the stainless steel pipe clamp 101. On the side close to the tunnel step 113, the upper adjustment plate 106 is connected to the special stainless steel pipe clamp 101 through the pipe clamp fixing bolt 105. The lower adjustment plate 108 is fixed to the tunnel ground by ground fixing bolts 109. During installation, ensure that the center lines of the upper and lower adjustment plates coincide in the vertical direction. Install the fiber grating displacement meter 107 between the upper adjustment plate 106 and the lower adjustment plate 108, and fasten the connecting rods 110 at both ends of the grating displacement meter into the clamping holes of the upper and lower adjustment plates. The upper and lower adjustment plates are provided with different clamping hole positions, and the installation position can be adjusted according to the actual distance between the pipeline and the ground and the actual length of the sensor and the connecting rod. Figure 3As shown, the pipeline micro deformation monitoring device includes a fiber Bragg grating strain gauge 201, a fiber Bragg grating thermometer 202, a monitoring section protective layer 203, a single-core armored cable 204, an optical cable protection tube 205, a tunnel optical cable 111, and a tunnel optical cable junction box 206. At least three sets of fiber Bragg grating strain gauges 201 and one set of fiber Bragg grating thermometer 202 are installed at the possible pipeline stress concentration parts analyzed in the early stage. The fiber Bragg grating strain gauge 201 and the fiber Bragg grating thermometer 202 need to be installed on the surface of the pipeline steel body. During installation, the three-layer PE anti-corrosion layer 103 of the pipeline needs to be partially opened, and the fiber Bragg grating strain gauge 201 and the fiber Bragg grating thermometer 202 are welded to the pipeline surface using spot welding technology. In order to speed up the progress of on-site construction, the fiber Bragg grating strain sensor and fiber Bragg grating temperature sensor used in the same section can be customized and stringed in advance. Afterwards, the partially opened part of the three-layer PE anti-corrosion layer 103 is dried and anti-corroded with viscoelastic body to prevent residual water vapor from corroding the pipeline and the sensor. After the anti-corrosion is completed, a spark leak detector must be used to ensure complete anti-corrosion. The fiber optic Bragg grating strain gauge 201 and the fiber optic Bragg grating thermometer 202 lead-out optical cable must be coiled in an S shape on the pipe wall, leaving enough deformation to prevent the pipeline from deforming and pulling the cable to cause damage to the optical cable. The entire monitoring section is protected by a monitoring section protective layer 203.

[0050] After the optical cable leading out of the pipeline macro deformation monitoring device and the optical cable leading out of the adjacent pipeline micro deformation monitoring device are connected in series at the top of the pipeline, two single-core armored optical cables 204 are used to fuse the ends of the series optical cables to the tunnel optical cable 111 through the optical cable junction box 206, and sealant is poured into the optical cable junction box 206 to prevent water from seeping in. When the single-core armored optical cable 204 is connected to the tunnel optical cable, a spare channel is designed. When a fault occurs somewhere in the series optical cable composed of the pipeline macro deformation monitoring device and the pipeline micro deformation monitoring device, part of the sensor data can be measured forward from one end, and the remaining sensor data can be measured reversely from the other end to ensure that all sensor data are read normally. The single-core armored optical cable 204 is covered with a PVC optical cable protection tube 205. The tunnel optical cable 111 uses a standard loose tube layer-twisted steel wire armored optical cable that is waterproof, resistant to water pressure, resistant to hydrolysis, resistant to corrosion, and high in strength, and can operate stably and for a long time in an underwater environment. The tunnel optical cable is fixed in the optical cable box above the handrail 112 on the wall on one side of the step 113 in the tunnel, and a certain length of cable is reserved during the laying process. According to the actual situation of the tunnel, as well as the number and installation location of the pipeline macro deformation monitoring device and pipeline micro deformation monitoring device, the layout location of the data acquisition and transmission subsystem is comprehensively determined. The tunnel optical cable is led out of the tunnel from one side or both sides of the tunnel and connected to the data acquisition and transmission subsystem near the tunnel entrance.

[0051] The data acquisition and transmission subsystem outside the tunnel includes a fiber terminal box, a fiber Bragg grating demodulator, a data transmission module, a lightning protection device, and a power supply device. If there is no mains electricity available on site, a solar panel and a battery power supply system can be equipped to ensure 24-hour online monitoring and scheduled data transmission of the monitoring equipment.

[0052] According to the settings, the fiber optic terminal box in the data acquisition and transmission subsystem is used to separate the optical cables in the main optical cable in the tunnel, so as to facilitate the use of jumpers to connect to each optical cable and read the monitoring data of each channel separately. The fiber optic Bragg grating demodulator is connected to each optical cable through a jumper, and emits a single-wavelength laser to each optical cable at a fixed time. The emitted laser can change back and forth within a large band. At the same time, the return wavelength of the sensor in each optical cable is recorded and stored in the fiber optic terminal box. The lightning protection device is used to prevent the integrated field monitoring station in the open field environment from being affected by lightning and causing damage to the on-site equipment and lines. The data acquisition and transmission subsystem collects monitoring data regularly or in real time, and uses a wireless communication network through the data transmission module to transmit the data to the physical server or cloud server of the monitoring and early warning center. The monitoring and early warning subsystem is located on the physical server or cloud server of the monitoring and early warning center, including a data center for receiving monitoring data and performing data screening, a data analysis module for conducting pipeline displacement analysis and pipeline strain / stress analysis, and a monitoring and early warning module that integrates pipeline macroscopic displacement deformation and pipeline stress state, and takes pipeline intrinsic safety monitoring and early warning as the core, and issues corresponding early warning information based on the calculated ratio of the maximum value of pipeline axial additional tension and compressive stress to the allowable value of axial additional tension and compressive stress. After receiving the monitoring data, the data center needs to undergo data screening. Data screening is divided into two sub-steps: valid data screening and abnormal data screening. Assume that m data collection commands are issued each time data is collected, and n groups of data are successfully collected, then valid data screening and abnormal data screening are performed on the n groups of data in turn. Valid data screening is to perform preliminary screening on the above n groups of data according to the sensor range, eliminate invalid data that exceeds the sensor range, and leave n2 groups of data. Abnormal data screening is to define the critical value Gp(n2) of the Grubbs test with a detection level of 5% for the remaining n2 groups of data according to the Grubbs test method, and calculate the mean of the remaining n2 groups of data in turn. Standard Deviation and the Grubbs test statistic for each group Select the maximum Grubbs test statistic value G among the remaining n2 groups of data k (G k =max(G i )) for analysis, if G k >Gp(n2) indicates that the kth data is an abnormal value, and the kth data needs to be removed, and the above abnormal data screening process is repeated for the remaining n2=n2-1 groups of data until G k<Gp(n2), indicating that the remaining data are not abnormal values, the remaining data are retained and the average value of the remaining data is taken as the monitoring data after the measurement result value is screened, and the data screening is ended at the same time.

[0053] The above-screened monitoring data can be used in the data analysis module to carry out pipeline displacement analysis and pipeline strain / stress analysis. Under the premise of considering the temperature wavelength, the pipeline displacement can be directly calculated using the monitoring data according to the wavelength and displacement calculation formula. Pipeline strain / stress analysis is relatively complex. Based on the plane section assumption and superposition principle in elastic theory, the pipeline strain value at any position of the monitoring section can be calculated based on the three sets of strain data on the monitoring section at the same time (three sets of strain data and one set of temperature data when using fiber Bragg grating strain monitoring sensors). The specific calculation steps are as follows:

[0054] The pipe strain consists of membrane strain, y-direction bending strain and z-direction bending strain. Suppose the membrane strain, maximum y-direction bending strain and maximum z-direction bending strain of the monitored section are ε m , According to the superposition principle, the strain at any point on the pipe cross section is:

[0055]

[0056] For the preferred axial strain sensor installation method mentioned in Example 1, the monitored strain values ​​at the top of the pipeline and on the left and right sides are U(0, r o ), Its m , The relationship is as follows:

[0057] Formula 2:

[0058] Formula 3:

[0059] Formula 4:

[0060] From Formula 2-Formula 4, the film strain of the monitoring section represented by the monitoring strain and the maximum bending in the y and z directions are obtained as follows:

[0061] Formula 5:

[0062] Formula 6:

[0063] Formula 7:

[0064] Combining the bending strains in the y and z directions, the maximum bending strain of the cross section can be obtained as follows:

[0065]

[0066] The angle at which the maximum bending strain occurs is, Formula 9:

[0067]

[0068] Accordingly, the maximum and minimum axial strains of the monitoring section are as follows: Formula 10:

[0069]

[0070] The axial strain at any point in the pipe cross section represented by the monitored strain is, Formula 11:

[0071]

[0072] Similarly, the maximum axial strain at each angle of the monitoring section can be obtained from the above formula: Formula 12:

[0073]

[0074] The average axial strain of the monitoring section is, Formula 13:

[0075]

[0076] The bending strain of the monitored section is, Formula 14:

[0077]

[0078] According to formula 12-14 and the pipeline stress-strain relationship curve, the maximum axial stress, average axial stress and bending stress values ​​at each angle of the monitored section can be obtained.

[0079] The monitoring and early warning module in the monitoring and early warning subsystem integrates the pipeline macroscopic displacement deformation and pipeline stress state, and issues early warning information with pipeline intrinsic safety monitoring and early warning as the core; when the pipeline axial additional tension and compressive stress values ​​reach or exceed 30% of the allowable value of axial additional tension and compressive stress, a blue early warning message is issued; when the pipeline axial additional tension and compressive stress values ​​reach or exceed 60% of the allowable value of axial additional tension and compressive stress, a yellow early warning message is issued; when the pipeline axial additional tension and compressive stress values ​​reach or exceed 90% of the allowable value of axial additional tension and compressive stress, a red early warning message is issued. The monitoring and early warning module of the monitoring and early warning subsystem integrates the pipeline macroscopic displacement deformation and pipeline stress state, and issues early warning information with pipeline intrinsic safety monitoring and early warning as the core, and issues corresponding early warning information based on the calculated ratio of the maximum value of pipeline axial additional tension and compressive stress to the allowable value of axial additional tension and compressive stress, and automatically pushes it to the designated user's mobile phone in the form of SMS, as follows:

[0080] When the pipeline axial additional tensile and compressive stress values ​​reach or exceed 30% of the allowable values ​​of axial additional tensile and compressive stress, the monitoring and early warning subsystem issues a blue warning message;

[0081] When the additional axial tensile and compressive stress values ​​of the pipeline reach or exceed 60% of the allowable values ​​of the additional axial tensile and compressive stress, the monitoring and early warning subsystem will issue a yellow early warning message;

[0082] When the additional axial tensile and compressive stress values ​​of the pipeline reach or exceed 90% of the allowable values ​​of the additional axial tensile and compressive stresses, the monitoring and early warning subsystem will issue a red warning message.

[0083] The displacement sensor and strain sensor selected by the present invention are both passive sensors, and are waterproof and resistant to water pressure. They can be used for underwater long-term monitoring, and are particularly suitable for macro and micro deformation monitoring of oil and gas pipelines in water-sealed tunnels. They will not have adverse effects on underwater pipelines, and can realize real-time online monitoring of pipeline operation. The system is also suitable for pipeline deformation monitoring in non-water-sealed tunnels, and can be replaced with vibrating string sensors according to actual needs without adjusting the existing monitoring method, so the scope of application is wider. According to the results of on-site investigations, pipeline completion drawings, measured three-dimensional coordinates of pipelines, and finite element analysis results, the present invention reasonably arranges monitoring sections based on the principle of controlling key and dangerous parts, and the monitoring layout is more scientific and reasonable, with outstanding economic efficiency. By monitoring the macro deformation and micro deformation of the pipeline, the in-situ state and stress conditions of the pipeline can be grasped in real time, and early warning information can be issued in time when abnormalities are found. The monitoring and early warning system performs real-time analysis and solution and early warning information release according to the monitoring results, and takes preventive measures in time, which helps to ensure the safety of pipeline operation. In addition, this monitoring system has no requirements for pipeline operating conditions during installation, does not require pressure reduction, and does not affect the normal operation of oil and gas pipelines.

[0084] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A water-sealed tunnel oil and gas pipeline deformation monitoring system, characterized in that: It includes a pipeline deformation monitoring subsystem placed in the tunnel, a data acquisition and transmission subsystem placed outside the tunnel, and a monitoring and early warning subsystem located in the monitoring and early warning center; the pipeline deformation monitoring subsystem includes a pipeline macro deformation monitoring device and a pipeline micro deformation monitoring device; the data acquisition and transmission subsystem includes an optical fiber terminal box, an optical fiber Bragg grating demodulator, a data transmission module, a lightning protection device, and a power supply device. The monitoring and early warning subsystem is located at the physical server or cloud server end of the monitoring and early warning center; it includes a data center for receiving monitoring data and screening data, a data analysis module for carrying out pipeline displacement analysis and pipeline strain / stress analysis, and a monitoring and early warning module that integrates pipeline macro displacement deformation and pipeline stress state, and takes pipeline intrinsic safety monitoring and early warning as the core, and issues corresponding early warning information according to the calculated ratio of the maximum values ​​of pipeline axial additional tension and compressive stress to the allowable values ​​of axial additional tension and compressive stress; The pipeline macro deformation monitoring device comprises a special stainless steel pipe clamp, a pipe clamp fixing bolt, an upper adjustment plate, a fiber Bragg grating displacement meter connecting rod, a fiber Bragg grating displacement meter, a lower adjustment plate, and a ground fixing bolt; the special stainless steel pipe clamp is divided into two semicircles and is fastened to the pipeline surface by the pipe clamp fixing bolt; in order to prevent the special stainless steel pipe clamp from damaging the pipeline and the three-layer PE anti-corrosion layer, a 6mm thick rubber plate is installed between the pipeline and the stainless steel pipe clamp; on the side close to the tunnel step, the upper adjustment plate is connected to the special stainless steel pipe clamp by the pipe clamp fixing bolt; the lower adjustment plate is fixed to the tunnel ground by the ground fixing bolt, and during installation, it is ensured that the center lines of the upper adjustment plate and the lower adjustment plate coincide in the vertical direction; the fiber Bragg grating displacement meter is installed between the upper adjustment plate and the lower adjustment plate, and the connecting rods at both ends of the grating displacement meter are fastened to the clamping holes of the upper adjustment plate and the lower adjustment plate; different clamping hole positions are provided on the upper and lower adjustment plates, and the installation position can be adjusted according to the actual distance between the pipeline and the ground and the actual length of the sensor and the connecting rod; The pipeline micro-deformation monitoring device includes a fiber grating strain gauge, a fiber grating thermometer, a monitoring section protective layer, a single-core armored optical cable, an optical cable protection tube, a tunnel optical cable, and a tunnel optical cable junction box; the fiber grating strain gauge and the fiber grating thermometer are both installed on the surface of the pipeline steel body. During installation, the three-layer PE anti-corrosion layer of the pipeline needs to be partially opened, and the fiber grating strain gauge and the fiber grating thermometer are fused to the pipeline surface using spot welding technology.

2. The water-sealed tunnel oil and gas pipeline deformation monitoring system according to claim 1, characterized in that: After the optical cable leading out of the pipeline macro-deformation monitoring device and the optical cable leading out of the adjacent pipeline micro-deformation monitoring device are connected in series at the top of the pipeline, two single-core armored optical cables are used to fuse the ends of the series optical cables with the tunnel optical cable through an optical cable junction box. The single-core armored optical cable is protected by an optical cable protection tube, and sealant is poured into the optical cable junction box to prevent water from seeping in.

3. The water-sealed tunnel oil and gas pipeline deformation monitoring system according to claim 1, characterized in that: The fiber optic terminal box in the data acquisition and transmission subsystem is used to separate the optical cables in the tunnel optical cable, so as to facilitate the use of jumpers to connect to the optical cables and read the monitoring data of each optical cable respectively; the fiber optic Bragg grating demodulator is connected to each optical cable through jumpers, and emits a single-wavelength laser to each optical cable at a fixed time, and the emitted laser can vary within a larger wavelength range, and at the same time, the return wavelength of the sensor in each optical cable is recorded and stored in the fiber optic Bragg grating demodulator; The data transmission module is used to transmit the monitoring data stored in the fiber grating demodulator to the designated server-side monitoring and early warning subsystem data center; the lightning protection device is used to prevent the integrated field monitoring station in the open wild environment from being affected by lightning and causing damage to the on-site equipment and lines; the power supply device is used to supply power to the grating demodulator and data transmission module to ensure the normal operation of the equipment 24 hours a day.

4. The water-sealed tunnel oil and gas pipeline deformation monitoring system according to claim 3, characterized in that: The monitoring and early warning subsystem, the data center receives monitoring data and screens data, and the data screening is divided into two sub-steps: effective data screening and abnormal data screening; Assume that m data collection commands are issued each time data is collected, and n sets of data are successfully collected. Then, valid data screening and abnormal data screening are performed on the n sets of data in turn. Valid data screening is to conduct preliminary screening of the above n groups of data according to the sensor range, remove invalid data that exceeds the sensor range, and the remaining n2 groups of data; abnormal data screening is to take the detection level of 5% for the remaining n2 groups of data according to the Grubbs test method, and define the critical value G of the Grubbs test p (n2), and calculate the mean of the remaining n2 groups of data in turn Standard Deviation and the Grubbs test statistic for each group Select the remaining n2 groups of data and select the maximum value of the Grubbs test statistic G k (G k =max(G i )) for analysis, if G k >G p (n2) indicates that the kth data is an abnormal value, and the kth data needs to be removed, and the above abnormal data screening process is repeated for the remaining n2=n2-1 groups of data until G k <G p (n2), indicating that the remaining data are not abnormal values, the remaining data are retained and the average value of the remaining data is taken as the monitoring data after the value screening of this measurement result, and the data screening is ended at the same time; The above-screened monitoring data enters the data analysis module to carry out pipeline displacement analysis and pipeline strain / stress analysis; the pipeline displacement is directly calculated using the monitoring data according to the wavelength and displacement calculation formula under the premise of considering the temperature wavelength; the pipeline strain value at any position of the monitoring section can be calculated based on the three sets of strain data on the monitoring section at the same time after eliminating the temperature effect. The specific calculation steps are as follows: The pipeline strain is composed of film strain, y-direction bending strain and z-direction bending strain. Let the film strain of the monitoring section, the maximum y-direction bending strain and the maximum z-direction bending strain be ε m , According to the superposition principle, the strain at any point on the pipe cross section is: The monitored strain values ​​at the top and left and right sides of the pipeline are U(0,r o ), Its m , The relationship is as follows: Formula 2: Formula 3: Formula 4: The film strain of the monitoring section represented by the monitoring strain and the maximum bending in the y and z directions are obtained from Formula 2-Formula 4 respectively: Formula 5: Formula 6: Formula 7: Combining the bending strains in the y and z directions, the maximum bending strain of the cross section can be obtained as follows: The angle at which the maximum bending strain occurs is, Formula 9: Accordingly, the maximum and minimum axial strains of the monitoring section are as follows: Formula 10: The axial strain at any point in the pipe cross section represented by the monitored strain is, Formula 11: Similarly, the maximum axial strain at each angle of the monitoring section can be obtained from the above formula: Formula 12: The average axial strain of the monitoring section is, Formula 13: The bending strain of the monitored section is, Formula 14: According to the pipeline stress-strain relationship curve, the maximum axial stress, average axial stress, and bending stress values ​​at each angle of the monitoring section are obtained by formula 12-formula 14; The monitoring and early warning module in the monitoring and early warning subsystem integrates the pipeline macro-displacement deformation and pipeline stress state, and issues early warning information with pipeline intrinsic safety monitoring and early warning as the core; when the pipeline axial additional tension and compressive stress values ​​reach or exceed 30% of the allowable values ​​of the axial additional tension and compressive stress, a blue early warning information is issued; when the pipeline axial additional tension and compressive stress values ​​reach or exceed 60% of the allowable values ​​of the axial additional tension and compressive stress, a yellow early warning information is issued; when the pipeline axial additional tension and compressive stress values ​​reach or exceed 90% of the allowable values ​​of the axial additional tension and compressive stress, a red early warning information is issued.

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