Nonmetal pipeline health monitoring system and operation method

Abstract

The invention discloses a nonmetal pipeline health monitoring system and an operation method. The operation method comprises the following steps: a demodulation instrument respectively operates a BOTDA function and a DVS function; the temperature optical fiber is connected with the strain optical fiber, and the temperature optical fiber and the strain optical fiber are respectively connected with the BOTDA function module; one end of the vibration optical fiber is connected to the DVS function module; the BOTDA functional module outputs continuous laser and pulse laser, the two laser beams meet in the temperature optical fiber and the strain optical fiber and generate a Brillouin optical signal, the Brillouin optical signal is reversely transmitted back to the BOTDA functional module, and temperature and strain information along the pipeline is obtained based on Brillouin optical signal demodulation; the DVS function module outputs pulse laser, the pulse laser enters the vibration optical fiber and generates a Rayleigh optical signal, the Rayleigh optical signal is reversely transmitted back to the DVS function module, and a vibration signal along the pipeline is obtained based on Rayleigh optical signal demodulation. According to the invention, BOTDA and DVS monitoring technologies are fused, the defects that a single BOTDA technology cannot position an optical fiber breakpoint and a single DVS technology is high in false alarm rate are overcome, and the health state of the nonmetal pipeline is monitored.

Description

Technical Field

[0001] The invention belongs to the technical field of pipeline monitoring, and relates to a non-metallic pipeline health monitoring system and an operation method. Background Art

[0002] Non-metallic pipelines have been widely used in pressure pipelines for transporting oil, water and other media in oil fields, playing an important role in controlling the corrosion problem of traditional carbon steel pipelines. Although the application of non-metallic pipelines has become increasingly mature, due to their own weaknesses of low material strength and discontinuous joint positions, non-metallic pipelines have safety hazards such as excessive deformation, joint leakage, and even pipe body rupture. However, there is currently a general lack of online monitoring technology for in-service non-metallic pipelines in oil fields. First, the material properties and pipe body structure of non-metallic pipelines are significantly different from those of metal pipelines, which makes it impossible to directly apply mature monitoring and detection technologies for metal pipelines to non-metallic pipelines. Secondly, point sensors need to select a sensor for each parameter, which is not easy to integrate; and if the operating status of the pipeline is to be monitored, a large number of sensors need to be deployed, which will significantly increase the workload of installation and maintenance, resulting in high investment. Thirdly, although distributed optical fiber monitoring technology has been applied, the application effect is not ideal: generally only a single type of technology is used for pipeline leakage detection, and the operating parameters cannot be collected according to the service behavior characteristics of non-metallic pipelines; the monitoring optical fiber and pipeline are generally laid in the same trench, and the monitoring effect is greatly affected by the quality of optical fiber laying, and there are shortcomings such as missed reports / false reports. Therefore, the health status of non-metallic pipelines used in oil fields after service is generally in a "monitoring blind spot". Summary of the invention

[0003] The purpose of the present invention is to solve the problem that the metal pipeline monitoring technology in the prior art cannot be directly applied to non-metallic pipelines, and at the same time, the demand for point sensors is large, which increases the workload of installation and maintenance, and it is impossible to collect operating parameters for the service of non-metallic pipelines. A non-metallic pipeline health monitoring system and operation method are provided.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A non-metallic pipeline health monitoring system, comprising: a demodulator, a temperature optical fiber, a strain optical fiber and a vibration optical fiber;

[0006] The demodulator includes a BOTDA functional module and a DVS functional module; one end of the temperature optical fiber is connected to one end of the strain optical fiber, and the other end of the temperature optical fiber and the other end of the strain optical fiber are respectively connected to the BOTDA functional module of the demodulator; one end of the vibration optical fiber is connected to the DVS functional module of the demodulator; the temperature optical fiber, the strain optical fiber and the vibration optical fiber are all arranged on the outer side of the pipe wall of the non-metallic pipe; the BOTDA functional module outputs two laser beams; one is a pulsed laser, which enters the temperature optical fiber from the strain optical fiber; the other is a continuous laser, which enters the strain optical fiber from the temperature optical fiber; the two laser beams transmitted in opposite directions meet in the temperature optical fiber and the strain optical fiber and generate Brillouin optical signals, which are transmitted back along the optical fiber in the reverse direction and are received and processed by the BOTDA functional module; the DVS functional module outputs a pulsed laser beam that enters the vibration optical fiber and generates a Rayleigh optical signal, which is transmitted back along the optical fiber in the reverse direction and is received and processed by the DVS functional module.

[0007] A further improvement of the present invention is:

[0008] Furthermore, the temperature optical fiber, strain optical fiber and vibration optical fiber are all single-mode optical fibers; the strain optical fiber is tightly wound on the outer wall of the pipe, the temperature optical fiber and the strain optical fiber are arranged side by side, the temperature optical fiber is wound on the outer wall of the pipe, and there is a gap between the temperature optical fiber and the outer wall of the pipe; the vibration optical fiber is wound on the outer wall of the pipe, and there is a gap between the vibration optical fiber and the outer wall of the pipe.

[0009] Furthermore, the temperature optical fiber and the strain optical fiber are arranged side by side, and the signal of the temperature optical fiber is used to correct the strain optical fiber; specifically: the temperature Brillouin frequency coefficient of the optical fiber is k1, and the strain Brillouin frequency coefficient of the optical fiber is k2; for a certain spatial position, the Brillouin frequency shift of the temperature optical fiber at this position is F1, and the temperature corresponding to the temperature optical fiber at this position is k1*F1; the Brillouin frequency shift of the strain optical fiber at this position is F2, and the strain corresponding to the strain optical fiber at this position is k2*(F2-F1).

[0010] Furthermore, the strain optical fiber, the temperature optical fiber and the vibration optical fiber are wound in parallel on the outside of the tube body.

[0011] Further, the BOTDA functional module includes a signal output unit, a microwave signal source, an electro-optic modulator, a variable optical attenuator, a polarization scrambler, a second optical circulator, an avalanche photodetector and a signal acquisition unit;

[0012] The signal output unit outputs the first energy beam and the second energy beam; the first energy beam enters the electro-optic modulator to load the microwave signal generated by the microwave signal source for frequency modulation, then passes through the variable optical attenuator and the polarization scrambler in sequence, and is finally output by the polarization scrambler to enter the temperature optical fiber and the strain optical fiber; the second energy beam is split again to obtain the third energy beam and the fourth energy beam; the third energy beam enters the second optical circulator and then inputs the temperature optical fiber and the strain optical fiber; the continuous laser and the pulse laser inputted in opposite directions by the polarization scrambler and the second optical circulator meet in the temperature optical fiber and the strain optical fiber and generate a Brillouin optical signal, and the Brillouin optical signal contains the temperature and strain information of the temperature optical fiber and the strain optical fiber; the Brillouin optical signal is input into the avalanche photodetector through another port of the second optical circulator and converted into a first electrical signal; the first electrical signal enters the signal acquisition unit; the fourth energy beam is used by the DVS functional module.

[0013] Furthermore, the signal output unit includes a laser, a polarization beam splitter, an acousto-optic modulator, a pulsed erbium-doped fiber amplifier, and a non-polarization-maintaining beam splitter; the signal acquisition unit includes a data acquisition card and an industrial computer; the laser outputs continuous laser light to the polarization beam splitter for energy splitting, which is divided into a first energy beam and a second energy beam; the second energy beam enters the acousto-optic modulator to form a nanosecond laser pulse, and then passes through the pulsed erbium-doped fiber amplifier and the non-polarization-maintaining beam splitter in sequence, and is again energy split at the non-polarization-maintaining beam splitter to be divided into a third energy beam and a fourth energy beam; the first electrical signal is transmitted to the industrial computer via the data acquisition card.

[0014] Furthermore, the DVS functional module includes a signal output unit, a first optical circulator, a pre-release erbium-doped fiber amplifier, a single-channel PIN photodetector and a signal acquisition unit; the fourth energy beam obtained based on the signal output unit enters the vibrating optical fiber via the first optical circulator and generates a Rayleigh light signal, and the Rayleigh light signal contains the vibration information of the vibrating optical fiber; the Rayleigh light signal passes through the first optical circulator, the pre-release erbium-doped fiber amplifier and the single-channel PIN photodetector in sequence; the single-channel PIN photodetector converts the Rayleigh light signal into a second electrical signal, and the second electrical signal enters the signal acquisition unit, that is, the second electrical signal enters the industrial computer via the data acquisition card.

[0015] Furthermore, the energy of the first energy beam is 10% of the laser energy output by the laser; the energy of the second energy beam is 90% of the laser energy output by the laser; the energy of the third energy beam and the energy of the fourth energy beam are respectively 50% of the energy of the second energy beam; the first energy beam and the third energy beam are respectively used to form frequency-modulated continuous laser and pulsed laser for inputting temperature optical fiber and strain optical fiber of the BOTDA functional module; the fourth energy beam is used to form pulsed laser for inputting vibration optical fiber of the DVS functional module.

[0016] A method for operating a non-metallic pipeline health monitoring system, comprising:

[0017] Step 1: Run the BOTDA function to collect the temperature and strain information of the temperature optical fiber and the strain optical fiber;

[0018] Step 2: Determine whether the strain at each location along the pipeline exceeds a preset strain threshold. If so, determine that the corresponding location of the pipeline is excessively deformed and issue an alarm; if not, continue to monitor the temperature and strain information along the pipeline;

[0019] Step 3: Determine whether the temperature at each location along the pipeline exceeds a preset temperature threshold. If so, proceed to step 4; if not, continue to monitor the temperature and strain information along the pipeline.

[0020] Step 4: Run the DVS function to collect and determine whether there is an abnormal vibration signal at the location of the pipeline with abnormal temperature; if so, it is determined that the pipeline is leaking and an alarm is issued; if not, it is determined that the temperature abnormality is caused by external factors or there is a slight leakage in the pipeline, and a safety inspection warning is issued. Run the BOTDA function to continue monitoring the temperature and strain information along the pipeline.

[0021] Furthermore, the conversion between the BOTDA functional module and the DVS functional module is automatically implemented by the demodulator according to the set operation mode.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention outputs a beam of continuous laser and a beam of pulsed laser through the BOTDA function module, which meet in the temperature optical fiber and the strain optical fiber and generate a Brillouin optical signal, which is transmitted back and received and processed by the BOTDA function module; the DVS function module outputs a beam of pulsed laser into the vibration optical fiber and generates a Rayleigh optical signal, which is transmitted back and received and processed by the DVS function module. The present invention integrates the BOTDA and DVS monitoring technologies, overcomes the shortcomings of the single BOTDA technology being unable to locate the optical fiber breakpoint and the single DVS technology having a high false alarm rate, and can also perform comprehensive monitoring of the health status of non-metallic pipelines based on the two technologies. Furthermore, the demodulator of the present invention integrates the BOTDA and DVS functions, simplifies the equipment structure, reduces the equipment cost, and supports multiple operating modes by sharing some original parts. At the same time, the system application mode is flexible, and the optical fiber laying scheme and monitoring target parameters can be designed in a targeted manner according to the service behavior characteristics of different non-metallic pipelines. The system and method proposed in the present invention can be extended to other pipeline monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 It is a structural schematic diagram of the non-metallic pipeline health monitoring system of the present invention;

[0026] Figure 2 A schematic diagram of the structure and working principle of a demodulator according to an embodiment of the present invention;

[0027] Figure 3 This is a workflow diagram of the collaborative mode of the monitoring system according to an embodiment of the present invention.

[0028] Among them, 1-demodulator; 2-temperature optical fiber; 3-strain optical fiber; 4-vibration optical fiber; 1-1--laser; 1-2--polarization beam splitter; 1-3--acousto-optic modulator; 1-4--pulsed erbium-doped fiber amplifier; 1-5--non-polarization-maintaining beam splitter; 1-6--first optical circulator; 1-7--microwave signal source; 1-8--electro-optic modulator; 1-9--variable optical attenuator; 1-10--polarization scrambler; 1-11--second optical circulator; 1-12--pre-release erbium-doped fiber amplifier; 1-13--industrial computer; 1-14--data acquisition card; 1-15--avalanche photodetector; 1-16--single-channel PIN photodetector. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0031] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0032] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0033] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0034] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0036] See also Figure 1 , the present invention discloses a non-metallic pipeline health monitoring system, comprising: a demodulator 1, a temperature optical fiber 2, a strain optical fiber 3 and a vibration optical fiber 4;

[0037] See also Figure 2The demodulator 1 includes a BOTDA functional module and a DVS functional module; one end of the temperature optical fiber 2 is connected to one end of the strain optical fiber 3, and the other end of the temperature optical fiber 2 and the other end of the strain optical fiber 3 are respectively connected to the BOTDA functional module of the demodulator 1; one end of the vibration optical fiber 4 is connected to the DVS functional module of the demodulator 1; the temperature optical fiber 2, the strain optical fiber 3 and the vibration optical fiber 4 are all arranged on the outer side of the pipe wall of the non-metallic pipe; the BOTDA functional module outputs two laser beams; one beam is a continuous pulse laser, which enters the temperature optical fiber 2 from the strain optical fiber 3; the other beam is a continuous laser, which enters the strain optical fiber 3 from the temperature optical fiber 2; the two laser beams transmitted in opposite directions meet in the temperature optical fiber 2 and the strain optical fiber 3 and generate a Brillouin optical signal, which is transmitted back in the reverse direction and received and processed by the BOTDA functional module; the DVS functional module outputs a pulse laser into the vibration optical fiber 4 and generates a Rayleigh optical signal, which is transmitted back in the reverse direction and received and processed by the DVS functional module.

[0038] The temperature optical fiber 2, the strain optical fiber 3 and the vibration optical fiber 4 are all single-mode optical fibers. The strain optical fiber 3 is tightly wound on the outer wall of the pipeline, and the temperature optical fiber 2 and the strain optical fiber 3 are arranged side by side. The temperature optical fiber 2 is wound on the outer wall of the pipeline, and there is a gap between the temperature optical fiber 2 and the outer wall of the pipeline; the vibration optical fiber 4 is wound on the outer wall of the pipeline, and there is a gap between the vibration optical fiber 4 and the outer wall of the pipeline.

[0039] The temperature optical fiber 2 and the strain optical fiber 3 are arranged side by side, and the signal of the temperature optical fiber 2 corrects the strain optical fiber 3 at the same time; specifically: the temperature Brillouin frequency coefficient of the optical fiber is k1, and the strain Brillouin frequency coefficient of the optical fiber is k2; for a certain spatial position, the Brillouin frequency shift of the temperature optical fiber 2 at this position is F1, and the temperature corresponding to the temperature optical fiber 2 at this position is k1*F1; the Brillouin frequency shift of the strain optical fiber 3 at this position is F2, and the strain corresponding to the strain optical fiber 3 at this position is k2*(F2-F1). The strain optical fiber 3, the temperature optical fiber 2 and the vibration optical fiber 4 are wound in parallel on the outside of the tube body.

[0040] The BOTDA functional module includes a signal output unit, a microwave signal source 1-7, an electro-optic modulator 1-8, a variable optical attenuator 1-9, a polarization scrambler 1-10, a second optical circulator 1-11, an avalanche photodetector 1-15 and a signal acquisition unit;

[0041] The signal output unit outputs the first energy beam and the second energy beam; the first energy beam enters the electro-optical modulator 1-8 and is loaded with the microwave signal generated by the microwave signal source 1-7 for frequency modulation, and then passes through the variable optical attenuator 1-9 and the polarization scrambler 1-10 in sequence, and is finally output by the polarization scrambler 1-10 and enters the temperature optical fiber 2 and the strain optical fiber 3; the second energy beam is split again to obtain the third energy beam and the fourth energy beam; the third energy beam enters the second optical circulator 1-11 and is input into the temperature optical fiber 2 and the strain optical fiber 3; the continuous laser and the pulse laser inputted in opposite directions by the polarization scrambler 1-10 and the second optical circulator 1-11 meet in the temperature optical fiber 2 and the strain optical fiber 3 and generate a Brillouin optical signal, which contains the temperature and strain information of the temperature optical fiber 2 and the strain optical fiber 3; the Brillouin optical signal is input into the avalanche photodetector 1-15 through another port of the second optical circulator 1-11 and converted into a first electrical signal; the first electrical signal enters the signal acquisition unit; the fourth energy beam is used by the DVS functional module.

[0042] The signal output unit includes a laser 1-1, a polarization beam splitter 1-2, an acousto-optic modulator 1-3, a pulsed erbium-doped fiber amplifier 1-4, and a non-polarization-maintaining beam splitter 1-5; the signal acquisition unit includes a data acquisition card 1-14 and an industrial computer 1-13;

[0043] The laser 1-1 outputs a continuous laser to the polarization beam splitter 1-2 for energy splitting, and is divided into a first energy beam and a second energy beam; the second energy beam enters the acousto-optic modulator 1-3 to form a nanosecond laser pulse, and then passes through the pulsed erbium-doped fiber amplifier 1-4 and the non-polarization-maintaining beam splitter 1-5 in sequence, and is again split into a third energy beam and a fourth energy beam at the non-polarization-maintaining beam splitter 1-5; the first electrical signal is transmitted to the industrial computer 1-13 via the data acquisition card 1-14.

[0044] The DVS functional module includes a signal output unit, a first optical circulator 1-6, a pre-amplifier erbium-doped fiber amplifier 1-12, a single-channel PIN photodetector 1-16 and a signal acquisition unit;

[0045] The fourth energy beam obtained based on the signal output unit enters the vibrating optical fiber 4 via the first optical circulator 1-6 and generates a Rayleigh optical signal, which contains the vibration information of the vibrating optical fiber 4; the Rayleigh optical signal passes through the first optical circulator 1-6, the pre-release erbium-doped fiber amplifier 1-12 and the single-channel PIN photodetector 1-16 in sequence; the single-channel PIN photodetector 1-16 converts the Rayleigh optical signal into a second electrical signal, and the second electrical signal enters the signal acquisition unit, that is, the second electrical signal enters the data acquisition card 1-14 and is transmitted to the industrial computer 1-13.

[0046] The energy of the first energy beam is 10% of the laser energy output by the laser 1-1; the energy of the second energy beam is 90% of the laser energy output by the laser 1-1; the energy of the third energy beam and the energy of the fourth energy beam are 50% of the energy of the second energy beam respectively. The first energy beam and the third energy beam are used to form the frequency modulated continuous laser and pulsed laser of the temperature optical fiber 2 and the strain optical fiber 3 input to the BOTDA functional module respectively; the fourth energy beam is used to form the pulsed laser of the vibration optical fiber 4 input to the DVS functional module.

[0047] See also Figure 3 The present invention discloses an operation method of a non-metallic pipeline health monitoring system, comprising:

[0048] Step 1: Run the BOTDA function to collect the temperature and strain information of temperature fiber 2 and strain fiber 3;

[0049] Step 2: Determine whether the strain at each position along the pipeline exceeds a preset threshold. If so, determine that the corresponding position of the pipeline is excessively deformed and issue an alarm; if not, continue to monitor the temperature and strain information along the pipeline;

[0050] Step 3: Determine whether the temperature at each location along the pipeline exceeds a preset threshold. If so, proceed to step 4; if not, continue to monitor the temperature and strain information along the pipeline.

[0051] Step 4: Run the DVS function to collect and determine whether there is an abnormal vibration signal at the location of the pipeline with abnormal temperature; if so, it is determined that the pipeline is leaking and an alarm is issued; if not, it is determined that the temperature abnormality is caused by external factors or there is a slight leakage in the pipeline, and a safety inspection warning is issued. Run the BOTDA function to monitor the temperature and strain information along the pipeline.

[0052] The laser 1-1 is a 1550nm narrow linewidth laser; the polarization beam splitter 1-2 is a 90 / 10 polarization beam splitter; the non-polarization-maintaining beam splitter 1-5 is a 50 / 50 non-polarization-maintaining beam splitter; and the microwave signal source 1-7 is an 8GHz to 12GHz microwave signal source. The demodulator has a DVS optical fiber interface connected to the vibration light 4 to output pulsed laser and receive the returned Rayleigh scattering signal, which is used for vibration signal demodulation; the demodulator has two BOTDA optical fiber interfaces, which are respectively connected to the temperature optical fiber 2 and the strain optical fiber 3, one of which is internally connected to the second optical circulator 1-11 to output pulsed laser and return Brillouin signal, and the other optical fiber interface is internally connected to the polarization scrambler 1-10 to output frequency-modulated continuous light.

[0053] The temperature and strain signal sensing principle of this system is based on the Brillouin scattering effect of laser. Since both temperature and strain will cause Brillouin signal frequency shift, it is necessary to separate the temperature and strain signals: the temperature optical fiber needs to be desensitized to strain, such as armoring; the strain optical fiber is sensitive to both strain and temperature; the strain optical fiber and the temperature optical fiber are laid together, and the signal of the accompanying temperature optical fiber is used to correct the strain optical fiber. The specific method is: the temperature Brillouin frequency coefficient of the optical fiber is k1, and the strain Brillouin frequency coefficient of the optical fiber is k2; for a certain spatial position, the system detects that the Brillouin frequency shift of the temperature optical fiber at this point is F1, and the corresponding temperature is k1*F1; the system detects that the Brillouin frequency shift of the strain optical fiber at this point is F2, and the corresponding strain is k2*(F2-F1).

[0054] The vibration signal sensing principle in this system is based on the Rayleigh scattering effect of laser. When a certain point on the vibrating optical fiber is disturbed by external vibration, the system will detect the change in signal intensity at the disturbed position.

[0055] The temperature optical fiber 2, the strain optical fiber 3, and the vibration optical fiber 4 are all arranged on the outside of the pipe wall of the non-metallic pipe; the strain optical fiber 3 is tightly fitted on the outer wall of the pipe, and the strain data of the pipe is collected based on the strain optical fiber 3 to monitor the deformation of the pipe; the temperature optical fiber 2 and the strain optical fiber 3 are arranged together, but the temperature optical fiber 2 is not tightly fitted with the pipe, that is, the signal of the temperature optical fiber 2 is not affected by the deformation of the pipe, and the temperature data of the area near the pipe is collected based on the temperature optical fiber 2 to monitor the leakage of the pipe; the vibration optical fiber 4 is not tightly fitted with the pipe, and the vibration signal of the area near the pipe is collected based on the vibration optical fiber 4 to monitor the leakage of the pipe.

[0056] The positioning of monitoring events by this system is based on the mapping relationship of "optical fiber length-pipeline position". The mapping relationship can be established by field calibration or digital model alone or in combination: 1) Field calibration: After the actual fiber is laid, it is connected to the demodulator 1, and a representative position on the fiber is selected for "excitation", such as changing the ambient temperature of the selected position of the temperature fiber 2, or applying a large deformation to the selected position of the strain fiber 3, or knocking the selected position of the vibration fiber 4, etc. The fiber length corresponding to the excitation point is determined through the response signal detected by the system; by calibrating multiple positions, it is assumed that the fiber length between two adjacent calibration points is evenly distributed on the corresponding pipeline length. 2) Digital model: Based on the monitored pipeline length, fiber length, fiber laying method, etc., the corresponding relationship between fiber length and pipeline position is established through mathematical calculation.

[0057] This system can run BOTDA function or DVS function independently. Figure 3The collaborative mode shown is as follows: 1) The system runs the BOTDA function by default. 2) When the strain (or change in strain) at a certain position of the pipeline exceeds the preset threshold, it is judged as excessive deformation and an alarm is activated. 3) When the temperature (or temperature change) at a certain position of the pipeline exceeds the preset threshold and maintains an abnormal state, this position is marked and switched to the DVS function. If an abnormal vibration signal is found at this position or in the vicinity, it is judged as a pipeline leak and an alarm is activated; if no abnormal vibration signal is found, it is judged that the temperature change is caused by external factors or that the pipeline has a slow leak, and it is switched to the BOTDA function, but at the same time a safety reminder is issued: "It is recommended to conduct an on-site investigation of the event location."

[0058] The DVS function of this system has the function of locating the optical fiber breakpoint. Therefore, if a serious accident occurs, causing all the optical fibers at the accident point to break, although the BOTDA function cannot be run at this time, the DVS function can still be run to locate the failure point.

[0059] The present invention will be further described below in conjunction with specific embodiments.

[0060] 1) Monitoring object and purpose: Health monitoring of a newly built high-pressure flexible continuous oil pipeline in an oil field. The total length of the oil pipeline is 300m. The pipeline is connected by 15 20m long high-pressure flexible continuous pipes. The transmission medium is 65℃ crude oil. The pipeline is buried 1.5m deep. It is required to monitor the axial bending deformation and pipeline leakage of the pipeline.

[0061] 2) Test device: Using the demodulator of the present invention, such as Figure 2 As shown in the figure, temperature optical fiber, tight-sleeved strain optical fiber, and loose-sleeved vibration optical fiber are encapsulated in stainless steel capillaries. During the pipeline laying process, the three optical fibers are synchronously and parallelly wound around the outside of the pipe body, and the winding angle relative to the pipeline axis is 60°. The strain optical fiber is adhered to the outer wall of the pipeline with waterproof tape, and the temperature optical fiber and vibration optical fiber are fixed to the pipeline with bundling tape.

[0062] 3) Establishing a mapping relationship; after the pipeline pressure test is completed and before the joint position is backfilled, the temperature optical fiber 2 and the strain optical fiber 3 are fused, and the temperature optical fiber 2, the strain optical fiber 3 and the vibration optical fiber 4 are respectively connected to the corresponding interfaces of the demodulator 1.

[0063] First, a digital model is used to calculate the fiber length (L 光纤 ) corresponds to the pipe length (L 管道 ), L 管道 =L 光纤 *cos60°=0.5L 光纤Subsequently, the "joint", the key monitoring location for leakage, was calibrated on site, the DVS function of the system was run, the vibration optical fiber at each joint position was tapped in turn, and the digital model was corrected according to the vibration event location displayed by the system and the on-site pipeline location.

[0064] 4) System operation: After the pipeline is in operation, the operation monitoring system is used. Figure 3 The collaborative mode shown: the BOTDA function is used as a regular monitoring state; the temperature change threshold is set to ΔT=5°C, and the duration is set to 1h, that is, when the temperature at a certain position rises by more than 5°C relative to the temperature at the adjacent position, and the over-temperature holding time is greater than 1h, it is switched to the DVS function and subsequent vibration signal testing and judgment are performed; the strain change threshold is set to Δε=0.5%, that is, when the strain at a certain position rises by more than 0.5% relative to the initial strain of the operation, it is judged as excessive deformation and an alarm is issued.

[0065] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. 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 non-metallic pipeline health monitoring system, characterized in that: include: A demodulator (1), a temperature optical fiber (2), a strain optical fiber (3) and a vibration optical fiber (4); The demodulator (1) comprises a BOTDA functional module and a DVS functional module; one end of the temperature optical fiber (2) is connected to one end of the strain optical fiber (3), and the other end of the temperature optical fiber (2) and the other end of the strain optical fiber (3) are respectively connected to the BOTDA functional module of the demodulator (1); one end of the vibration optical fiber (4) is connected to the DVS functional module of the demodulator (1); the temperature optical fiber (2), the strain optical fiber (3) and the vibration optical fiber (4) are all arranged on the outer side of the pipe wall of the non-metallic pipe; The BOTDA functional module outputs two laser beams; one is a pulsed laser beam that enters the temperature optical fiber (2) from the strain optical fiber (3); the other is a continuous laser beam that enters the strain optical fiber (3) from the temperature optical fiber (2); the two laser beams that are transmitted in opposite directions meet in the temperature optical fiber (2) and the strain optical fiber (3) and generate a Brillouin optical signal, which is transmitted back along the optical fiber and received and processed by the BOTDA functional module; the DVS functional module outputs a pulsed laser beam that enters the vibration optical fiber (4) and generates a Rayleigh optical signal, which is transmitted back along the optical fiber and received and processed by the DVS functional module.

2. The non-metallic pipeline health monitoring system according to claim 1, characterized in that: The temperature optical fiber (2), strain optical fiber (3) and vibration optical fiber (4) are all single-mode optical fibers; the strain optical fiber (3) is tightly wound on the outer wall of the pipeline, the temperature optical fiber (2) and the strain optical fiber (3) are arranged side by side, the temperature optical fiber (2) is wound on the outer wall of the pipeline, and a gap exists between the temperature optical fiber (2) and the outer wall of the pipeline; the vibration optical fiber (4) is wound on the outer wall of the pipeline, and a gap exists between the vibration optical fiber (4) and the outer wall of the pipeline.

3. The non-metallic pipeline health monitoring system according to claim 2, characterized in that: The temperature optical fiber (2) and the strain optical fiber (3) are arranged side by side, and the signal of the temperature optical fiber (2) is used to correct the strain optical fiber (3); specifically, the temperature Brillouin frequency coefficient of the optical fiber is k1, and the strain Brillouin frequency coefficient of the optical fiber is k2; for a certain spatial position, the Brillouin frequency shift of the temperature optical fiber (2) at this position is F1, and the temperature corresponding to the temperature optical fiber (2) at this position is k1*F1; the Brillouin frequency shift of the strain optical fiber (3) at this position is F2, and the strain corresponding to the strain optical fiber (3) at this position is k2*(F2-F1).

4. The non-metallic pipeline health monitoring system according to claim 3, characterized in that: The strain optical fiber (3), the temperature optical fiber (2) and the vibration optical fiber (4) are wound in parallel on the outside of the tube body.

5. The non-metallic pipeline health monitoring system according to claim 4, characterized in that: The BOTDA functional module comprises a signal output unit, a microwave signal source (1-7), an electro-optic modulator (1-8), a variable optical attenuator (1-9), a polarization scrambler (1-10), a second optical circulator (1-11), an avalanche photodetector (1-15) and a signal acquisition unit; The signal output unit outputs a first energy beam and a second energy beam; the first energy beam enters an electro-optical modulator (1-8) to load a microwave signal generated by a microwave signal source (1-7) for frequency modulation, then passes through a variable optical attenuator (1-9) and a polarization scrambler (1-10) in sequence, and finally is output by the polarization scrambler (1-10) to enter a temperature optical fiber (2) and a strain optical fiber (3); the second energy beam is split again to obtain a third energy beam and a fourth energy beam; the third energy beam enters a second optical circulator (1-11) and then is input into the temperature optical fiber (2) and the strain optical fiber (3) (3); the continuous laser and the pulse laser inputted in opposite directions by the polarization scrambler (1-10) and the second optical circulator (1-11) meet in the temperature optical fiber (2) and the strain optical fiber (3) and generate a Brillouin optical signal, wherein the Brillouin optical signal contains the temperature and strain information of the temperature optical fiber (2) and the strain optical fiber (3); the Brillouin optical signal is inputted into the avalanche photodetector (1-15) via another port of the second optical circulator (1-11) and converted into a first electrical signal; the first electrical signal enters the signal acquisition unit; the fourth energy beam is used by the DVS function module.

6. The non-metallic pipeline health monitoring system according to claim 5, characterized in that: The signal output unit comprises a laser (1-1), a polarization beam splitter (1-2), an acousto-optic modulator (1-3), a pulsed erbium-doped fiber amplifier (1-4), and a non-polarization-maintaining beam splitter (1-5); the signal acquisition unit comprises a data acquisition card (1-14) and an industrial computer (1-13); The laser (1-1) outputs continuous laser light to a polarization beam splitter (1-2) for energy splitting, and the energy beam is split into a first energy beam and a second energy beam; the second energy beam enters an acousto-optic modulator (1-3) to form a nanosecond laser pulse, and then passes through a pulsed erbium-doped fiber amplifier (1-4) and a non-polarization-maintaining beam splitter (1-5) in sequence, and is again split into a third energy beam and a fourth energy beam at the non-polarization-maintaining beam splitter (1-5); the first electrical signal is transmitted to an industrial computer (1-13) via a data acquisition card (1-14).

7. The non-metallic pipeline health monitoring system according to claim 6, characterized in that: The DVS functional module comprises a signal output unit, a first optical circulator (1-6), a pre-amplifier erbium-doped fiber amplifier (1-12), a single-channel PIN photodetector (1-16) and a signal acquisition unit; The fourth energy beam obtained based on the signal output unit enters the vibrating optical fiber (4) via the first optical circulator (1-6) and generates a Rayleigh optical signal, wherein the Rayleigh optical signal contains vibration information of the vibrating optical fiber (4); the Rayleigh optical signal passes through the first optical circulator (1-6), the pre-release erbium-doped optical fiber amplifier (1-12) and the single-channel PIN photodetector (1-16) in sequence; the single-channel PIN photodetector (1-16) converts the Rayleigh optical signal into a second electrical signal, and the second electrical signal enters the signal acquisition unit, that is, the second electrical signal enters the data acquisition card (1-14) and is transmitted to the industrial computer (1-13).

8. The non-metallic pipeline health monitoring system according to claim 7, characterized in that: The energy of the first energy beam is 10% of the laser energy output by the laser (1-1); the energy of the second energy beam is 90% of the laser energy output by the laser (1-1); the energy of the third energy beam and the energy of the fourth energy beam are respectively 50% of the energy of the second energy beam; The first energy beam and the third energy beam are used to form frequency modulated continuous laser and pulse laser of the BOTDA function module input temperature optical fiber (2) and strain optical fiber (3) respectively; the fourth energy beam is used to form pulse laser of the DVS function module input vibration optical fiber (4).

9. A method for operating a non-metallic pipeline health monitoring system according to claim 7, characterized in that: include: Step 1: Run the BOTDA function to collect temperature and strain information of the temperature optical fiber (2) and the strain optical fiber (3); Step 2: Determine whether the strain at each position along the pipeline exceeds a preset strain threshold. If so, determine that the corresponding position of the pipeline is excessively deformed and issue an alarm; if not, continue to monitor the temperature and strain information along the pipeline; Step 3: Determine whether the temperature at each location along the pipeline exceeds a preset temperature threshold. If so, proceed to step 4. If it is not exceeded, continue to monitor the temperature and strain information along the pipeline; Step 4: Run the DVS function to collect and determine whether there is an abnormal vibration signal at the location of the pipeline with abnormal temperature; if so, it is determined that the pipeline is leaking and an alarm is issued; if not, it is determined that the temperature abnormality is caused by external factors or there is a slight leakage in the pipeline, and a safety inspection warning is issued. Run the BOTDA function to continue monitoring the temperature and strain information along the pipeline.

10. The operating method of the non-metallic pipeline health monitoring system according to claim 9, characterized in that: The conversion between the BOTDA function module and the DVS function module is automatically implemented by the demodulator (1) according to the set operation mode.

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