Oil and gas pipeline detecting and positioning device

Abstract

The utility model provides an oil and gas pipeline detecting and positioning device which is arranged on an oil and gas pipeline, an optical fiber is arranged above the oil and gas pipeline, and distributed optical fiber vibration sensors are linearly distributed on the optical fiber. And positioning is carried out by adopting a phi-OTDR technology. The phi-OTDR is different from a traditional OTDR, a coherent light source is adopted, the light source is required to have the characteristics of narrow linewidth and low frequency drift, and in order to improve the sensitivity and the positioning precision, the phi-OTDR adopts a fiber reinforced resin packaging optical cable as a sensing head, and adopts amplitude demodulation and phase demodulation in the aspect of signal demodulation. Based on the advantages, the distributed optical fiber vibration sensing technology can solve the problems that a traditional OTDR distributed optical fiber vibration sensing technology is low in positioning precision and low in sensitivity, oil and gas pipeline leakage positioning can be effectively achieved, oil leakage or oil stealing positions can be detected and positioned in time, and then economic losses and environmental pollution are reduced.

Description

Technical Field

[0001] The utility model relates to the field of oil and gas pipeline detection, and in particular to an oil and gas pipeline detection and positioning device. Background Art

[0002] An oil and gas pipeline proposed in Chinese utility model patent application No. CN200920221865.5 includes a steel pipe, a steel ring is coaxially fixed at each end of the steel pipe, a steel reinforcement skeleton is coaxially fixed between the two steel rings, concrete is coaxially fixed on the outer wall of the steel pipe, prestressed steel wire is wound around the outer wall of the concrete, and a protective layer is fixed on the outer wall of the concrete and the outer wall of the prestressed steel wire.

[0003] However, the existing oil and gas pipeline detection has some shortcomings in the process of use and still needs to be improved. First of all, the existing oil and gas pipelines may leak oil, steal oil and other major accidents during the transportation process. When oil leaks or oil thefts occur, it is impossible to detect and locate the leaks or thefts in time. This leads to relatively large economic losses and environmental pollution. Therefore, we make improvements to this and propose an oil and gas pipeline detection and positioning device. Utility Model Content

[0004] The purpose of the utility model is to address the problems raised by the existing background technology. In order to achieve the above-mentioned purpose of the utility model, the utility model provides the following technical solutions: an oil and gas pipeline detection and positioning device, which is arranged on the oil and gas pipeline, and an optical fiber is arranged above the oil and gas pipeline, and a distributed optical fiber vibration sensor is linearly arranged on the optical fiber, and the optical fiber is connected to the optical fiber host through an optical fiber connection port. The oil and gas pipeline connects the first gathering station with the second gathering station and the third gathering station, and the oil and gas pipeline is connected with an arc-shaped steering connecting pipe.

[0005] As a preferred technical solution of the utility model, the optical fiber host is arranged above the second gathering and transportation station.

[0006] As a preferred technical solution of the utility model, the oil and gas pipeline and the optical fiber are buried under the sandy soil.

[0007] As a preferred technical solution of the utility model, flanges are provided at the left and right ends of the oil and gas pipeline.

[0008] As a preferred technical solution of the present utility model, threaded holes are provided on the flange.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: In the scheme of the present invention: positioning is performed by adopting Φ-OTDR technology. Φ-OTDR is different from the traditional OTDR. It adopts a coherent light source and requires the light source to have narrow linewidth and low frequency drift characteristics. In order to improve the sensitivity and positioning accuracy, Φ-OTDR adopts a fiber-reinforced resin encapsulated optical cable as the sensor head, and amplitude demodulation and phase demodulation are used in signal demodulation. Based on these advantages, Φ-OTDR distributed optical fiber vibration sensing technology can solve the problems of low positioning accuracy and low sensitivity of traditional OTDR distributed optical fiber vibration sensing technology, and can effectively realize the positioning of oil and gas pipeline leaks, and timely detect and locate oil leaks or oil thefts, thereby reducing economic losses and environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A schematic diagram of the structure provided by the utility model;

[0011] Figure 2 This is a schematic diagram of the optical fiber structure provided by the utility model.

[0012] Indicated in the figure:

[0013] 1. Oil and gas pipeline; 101. Flange; 102. Threaded hole; 2. Optical fiber; 201. Distributed optical fiber vibration sensor; 3. Optical fiber host; 301. Optical fiber connection port; 4. First gathering and transportation station; 5. Second gathering and transportation station; 6. Third gathering and transportation station; 7. Desertified soil; 8. Arc-shaped steering connecting pipe. DETAILED DESCRIPTION

[0014] To make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution in the embodiment of the utility model will be described clearly and completely in conjunction with the accompanying drawings. Obviously, the described embodiment is a part of the embodiment of the utility model, not all of the embodiments.

[0015] Therefore, the following detailed description of the embodiments of the utility model is not intended to limit the scope of the utility model for which protection is sought, but merely represents some embodiments of the utility model. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model. It should be noted that the embodiments of the utility model and the features and technical solutions in the embodiments can be combined with each other without conflict. It should be noted that similar numbers and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0016] Example 1: Please refer to Figure 1-Figure 2, an oil and gas pipeline detection and positioning device is arranged on an oil and gas pipeline 1, an optical fiber 2 is arranged above the oil and gas pipeline 1, and distributed optical fiber vibration sensors 201 are linearly arranged on the optical fiber 2, and the optical fiber 2 is connected to the optical fiber host 3 through the optical fiber connection port 301. The oil and gas pipeline 1 connects the first gathering station 4 with the second gathering station 5 and the third gathering station 6. The optical fiber host 3 is arranged above the second gathering station 5. The oil and gas pipeline 1 and the optical fiber 2 are buried under the desertified soil 7. Flanges 101 are arranged at the left and right ends of the oil and gas pipeline 1. Threaded holes 102 are arranged on the flange 101. The oil and gas pipeline 1 is connected to an arc-shaped steering connecting pipe 8.

[0017] The distributed optical fiber vibration sensor 201 can be distributed linearly along the optical fiber 2 to achieve all-round and long-distance monitoring of the oil and gas pipeline 1. Due to the high sensitivity and high resolution of the Φ-OTDR technology, it can accurately detect tiny vibrations on the pipeline, thereby promptly discovering potential safety hazards such as leakage and illegal excavation.

[0018] The distributed optical fiber 2 vibration sensor can be connected to the optical fiber host 3 through the optical fiber connection port 301 to form a complete detection system. This connection method not only has a fast transmission speed, but also has a strong anti-interference ability, ensuring the accuracy and stability of the monitoring data.

[0019] The first gathering and transportation station 4, the second gathering and transportation station 5 and the third gathering and transportation station 6 are connected through the oil and gas pipeline 1, so as to realize the centralized management and efficient transportation of oil and gas resources. This layout is conducive to improving the utilization efficiency of oil and gas resources and reducing operating costs.

[0020] The optical fiber host 3 is arranged above the second gathering and transportation station 5, which can facilitate the processing and analysis of the monitoring data. At the same time, since the second gathering and transportation station 5 is located in the middle of the pipeline, this layout method also helps to achieve balanced monitoring and management of the entire pipeline system.

[0021] The oil and gas pipeline 1 and the optical fiber 2 are buried under the sandy soil 7, which can effectively protect them from interference and damage from the external environment. At the same time, the sandy soil 7 has good air permeability and water permeability, which is conducive to the long-term stable operation of the pipeline.

[0022] The oil and gas pipeline 1 can be conveniently connected and fixed through the flange 101 and the threaded hole 102 to ensure the sealing and stability of the pipeline system. This connection method is also convenient for the maintenance and replacement of the pipeline.

[0023] The arc-shaped turning connecting pipe 8 can realize the smooth transition of the oil and gas pipeline 1 between different directions, reduce the stress concentration and wear of the pipeline system. At the same time, this structure also helps to improve the overall stability and safety of the pipeline system.

[0024] During the use of the utility model, the optical fiber 2 is on the pipeline. The optical fiber 2 is laid in this way mainly for the consideration of being conducive to signal reception. The optical modem injects pulse light into the sensing optical fiber 2 to generate backward Rayleigh scattering, and separates the scattered light to obtain an optical signal superimposed and carrying vibration information. The optical signal is subjected to photoelectric conversion by the optical receiving module, and then amplified by the front stage, and enters the synchronous signal collector for analog-to-digital conversion. The coprocessor pre-processes and analyzes and calculates the digital signal, and finally the monitoring and analysis processing system transmits the collected information to the computer for further processing.

[0025] Positioning is performed by using Φ-OTDR technology. Φ-OTDR is different from traditional OTDR in that it uses a coherent light source and requires the light source to have narrow linewidth and low frequency drift characteristics. To improve sensitivity and positioning accuracy, Φ-OTDR uses fiber-reinforced resin encapsulated optical cables as sensor heads, and amplitude demodulation and phase demodulation are used for signal demodulation. Based on these advantages, Φ-OTDR distributed optical fiber 2 vibration sensing technology can solve the problems of low positioning accuracy and low sensitivity of traditional OTDR distributed optical fiber vibration sensing technology, so it can be used for oil and gas pipeline 1 leakage positioning;

[0026] Φ-OTDR uses a narrow linewidth pulse external modulation technology light source to inject strong coherent light into the optical fiber 2, generating backward Rayleigh scattered light in the sensing optical fiber 2. Therefore, the output of the system is the result obtained after the interference of the backward Rayleigh scattered light. When there is a disturbance in the outside world, the pressure acting on the optical fiber 2 changes the length of the optical fiber 2 and the refractive index in the optical fiber 2. Under the interference, the light phase changes and causes the light intensity to change. The position of the vibration signal is obtained by continuously subtracting the backward Rayleigh scattered signals before and after in real time.

[0027] The wave theory of light is needed to explain the interference principle of Φ-OTDR. Assume that the laser output is a continuous sine wave, A and B represent the positions of the end and the front of two sine modulated signals respectively. The laser generates sine signals at B and A successively, and the time interval is τ, then τ=(d+s) * n / c, where n is the refractive index of the fiber 2 core and c is the speed of light.

[0028] If the vibration equations at A and B are:

[0029] f A = cos(ω A t)1

[0030] f B = cos(ω B t)2

[0031] At the detector, the Rayleigh backscattering generated at A reaches the detector first compared to that at B. The detector detects the sine wave at A and reaches C, which is generated at the same time as the Rayleigh backscattering generated at B, thus generating coherent interference. When d = s, the Rayleigh backscattering light vibration equations are respectively,

[0032]

[0033]

[0034] Where K represents the backscattering light intensity coefficient, φ represents the additional phase of backscattering, and the interference equation is:

[0035]

[0036] Formula 5 A =ω B , then there is,

[0037]

[0038] That is, the detected power can be expressed as,

[0039] w=∫f 2 dt=2K 2 7

[0040] In actual situations, the laser frequency shift cannot be ignored. If it is a linear drift, and α is used to represent the drift rate, then,

[0041] f A =f B +ατ (8)

[0042] ω A =2πf A

[0043] ω B =2πf B

[0044] Substituting into equation 6, when ατ< <f B Under the condition of , we get

[0045] f(t)=2Kcos[π(2f B +ατ)t+φ]cos(πατ*t)

[0046] ≈2Kcos[π(2f B t)+φ]cos(πατ*t) 9

[0047] If ατ is small enough, then equation 6 is the same as equation 9. When the laser frequency shift rate α=1MHz, τ=1μs, we have:

[0048] f(t)≈2Kcos[2πf B t+φ]cos(πt)10

[0049] In order to avoid too fast changes in optical power in the experiment, a laser with a lower frequency drift rate, that is, a narrow linewidth, high-power fiber 2 laser, should be used.

[0050] The entire Φ-OTDR system reflects distance information through time. When the refractive index n is known, the time difference between the backscattered light and the Φ-OTDR output pulse is calculated, and the time domain signal is converted into information related to the distance: The vibration point on the sensing optical fiber 2 line can be accurately calculated and determined.

[0051] The positioning accuracy Δz of the Φ-OTDR system is related to the refractive index and the width parameters of the detection pulse, and Δz=cT p / 2n g , n g is the group refractive index, T p Indicates the width of the detection pulse, so the Φ-OTDR system uses a light source with high-power narrow-linewidth pulse characteristics, which has obvious interference effect and greatly improves the system sensitivity and positioning accuracy.

[0052] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Although the present invention has been described in detail with reference to the above embodiments, the present invention is not limited to the above specific implementation methods. Therefore, any modification or replacement of the present invention; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention are included in the scope of the claims of the present invention.

Claims

1. An oil and gas pipeline detection and positioning device, arranged on an oil and gas pipeline (1), characterized in that: An optical fiber (2) is arranged above the oil and gas pipeline (1), and distributed optical fiber vibration sensors (201) are linearly arranged on the optical fiber (2). The optical fiber (2) is connected to the optical fiber host (3) through an optical fiber connection port (301). The oil and gas pipeline (1) connects the first gathering station (4) with the second gathering station (5) and the third gathering station (6). The oil and gas pipeline (1) is connected to an arc-shaped steering connection pipe (8).

2. The oil and gas pipeline detection and positioning device according to claim 1, characterized in that: The optical fiber host (3) is arranged above the second gathering and transportation station (5).

3. The oil and gas pipeline detection and positioning device according to claim 2, characterized in that: The oil and gas pipeline (1) and the optical fiber (2) are buried under the sandy soil (7).

4. The oil and gas pipeline detection and positioning device according to claim 3, characterized in that: Flange plates (101) are provided at the left and right ends of the oil and gas pipeline (1).

5. The oil and gas pipeline detection and positioning device according to claim 4, characterized in that: The flange (101) is provided with a threaded hole (102).

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