Fiber optic grating target flow meter

Abstract

The application discloses a fiber grating target type flowmeter. The application comprises a center fixed body, a plurality of cantilever beams and a folding mechanism; one end of the plurality of cantilever beams is hingedly connected to one end of the center fixed body at intervals, and the other end of the plurality of cantilever beams is provided with a target sheet; the folding mechanism is arranged on the center fixed body and is used for folding or opening the plurality of cantilever beams; the two side surfaces of the cantilever beam are correspondingly provided with fiber gratings, the fiber gratings are connected with one end of a conducting optical fiber, and the other end of the conducting optical fiber is connected with external demodulation equipment. The application effectively improves the range and measurement precision of multiphase flow detection in the oil exploitation process, eliminates the influence of temperature on flow detection and effectively solves the problem that the target type array structure is too crowded to be transported in a horizontal well.

Description

Technical Field

[0001] This invention relates to the field of flow meter technology, and more particularly to a fiber optic target flow meter. Background Technology

[0002] Flow meters are crucial monitoring instruments in oil and gas fields, playing a vital role in various stations and facilities. With the continuous development of oil and gas fields, most domestic oil and gas fields have entered the middle and late stages of development. Decreasing oil production leads to more complex wellbore flow patterns, with gas-water-oil three-phase mixing being a common phenomenon. Simultaneously, with the rapid expansion of horizontal and highly deviated well production technologies, the need for accurate flow measurement methods for multiphase flows in horizontal and highly deviated wells is increasingly urgent. In horizontal and highly deviated wells, gravity causes gravity-induced differentiation within the pipeline, making accurate measurement impossible with traditional flow meters and flow measurement methods.

[0003] Furthermore, due to the large angles of horizontal or highly deviated wells, the installation and transportation methods used for vertical well logging equipment cannot be directly applied. Crawler vehicles are often used to transport horizontal logging equipment, ensuring its smooth arrival at the designated logging location. However, due to the diameter of the horizontal well pipe, the logging equipment should not be too large to avoid collisions or jamming during transportation. The fundamental principle of a target flowmeter lies in the deformation of the grating caused by the force applied to the target plate. The size of the target plate directly affects the measurement accuracy of the target flowmeter. Therefore, developing a sensing device that can both ensure the smooth installation of the logging target sensor and guarantee measurement accuracy is particularly important.

[0004] Fiber Bragg gratings are a new type of passive optical device that has been used frequently in recent years. Among them, Bragg gratings have high sensitivity to temperature and strain. When affected by temperature or strain, the center wavelength of its reflected wave will drift significantly. By detecting the change in the center of the reflected wavelength, the influence of external temperature and stress can be quantified. They are often used in flow detection, object health monitoring and other fields. Due to their many advantages such as good flexibility, strong resistance to electromagnetic interference, small structure, convenient production and good explosion-proof properties, they have good development prospects and application space.

[0005] Current target-type fiber Bragg grating flow meters utilize the advantages of fiber Bragg gratings in accurate and stable velocity measurement to meet corresponding application requirements. However, they cannot accurately measure the velocity of multiphase flow in horizontal pipelines, nor can they complete the full well circumference flow detection. More importantly, the circular target plate of common target-type flow meters causes significant difficulties in the array structure during horizontal downhole transportation. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned shortcomings of the prior art by proposing a fiber optic grating target flow meter that effectively improves the range and measurement accuracy of multiphase flow detection in oil extraction processes, while eliminating the influence of temperature on flow detection and effectively solving the problem of overcrowded target array structures making horizontal well transport difficult.

[0007] The present invention discloses a fiber Bragg grating target flow meter, comprising a central fixed body, multiple cantilever beams, and a retraction mechanism; one end of each of the multiple cantilever beams is hinged at a distance from one end of the central fixed body, and the other end of each of the multiple cantilever beams is provided with a target plate; the retraction mechanism is disposed on the central fixed body and is used to retract or open the multiple cantilever beams; fiber Bragg gratings are correspondingly disposed on both sides of the cantilever beams, and each fiber Bragg grating is connected to one end of a conductive optical fiber, the other end of which is connected to an external demodulation device.

[0008] Furthermore, the retracting mechanism includes a slip ring, a horizontal pusher, and multiple support rods. The slip ring shell is slidably sleeved on the central fixed body. One end of each of the multiple support rods is hinged or slidably connected to the cantilever beam, and the other end of each of the multiple support rods is hinged to the slip ring. The horizontal pusher is disposed on the central fixed body, and its driving end is connected to the slip ring for transmission, so as to drive the slip ring to slide back and forth along the central fixed body.

[0009] Furthermore, one end of the support rod is slidably connected to the cantilever beam, and the cantilever beam has a groove on the side near the slip ring, and one end of the support rod is slidably disposed in the groove.

[0010] Furthermore, the target piece is integrally formed with the cantilever beam.

[0011] Furthermore, the target plate is pear-shaped, and the width of the end of the target plate away from the cantilever beam is greater than the width of the end of the target plate closer to the cantilever beam.

[0012] Furthermore, there are six cantilever beams, which are arranged at equal angular intervals on the central fixed body.

[0013] Furthermore, the other end of the central fixing body is also provided with a screw hole for connecting to external equipment.

[0014] Furthermore, the cantilever beam is a rectangular thin sheet.

[0015] Furthermore, the fiber grating is a high-temperature resistant fiber grating, which is fixed to the cantilever beam using a welding process.

[0016] The principle behind the fiber Bragg grating target flowmeter design of this invention lies in the fact that a pair of fiber Bragg gratings on a single cantilever beam are fixed to its outer surface. When the cantilever beam is subjected to stress and undergoes yielding deformation, or when the ambient temperature changes, the center wavelength of the fiber Bragg grating changes accordingly. The flowmeter target is impacted by the liquid and gas in the pipe, causing strain in the cantilever beam. The fiber Bragg gratings attached to the two surfaces of the cantilever beam undergo deformation under tension, and the change in the center wavelength of their reflected wave is linearly related to the magnitude of the tension. Because the fiber Bragg gratings fixed to the two surfaces of the cantilever beam are affected by the same temperature and opposite stress directions, external demodulation equipment can eliminate the influence of temperature on flow detection by processing the drift of the center wavelength of the reflected waves from the two fiber Bragg gratings, while simultaneously enhancing the sensitivity of the fiber Bragg gratings.

[0017] Compared with existing fiber Bragg grating technology, the fiber Bragg grating flowmeter designed in this paper has the following beneficial technical effects:

[0018] 1. Fiber Bragg gratings on different surfaces of a cantilever beam are located at the same position on the cantilever beam. When the target plate experiences strain due to fluid impact, the stress directions are opposite because the fiber Bragg gratings are on different surfaces of the cantilever beam. Therefore, by differentially processing the wavelength drift of the two gratings, the influence of temperature on the fiber Bragg gratings can be effectively eliminated while improving the sensitivity of the fiber Bragg gratings. The other ends of the two grating fibers are connected to an external demodulation device through a transmission fiber. The external demodulation device can calculate and analyze the flow rate of the pipeline fluid by demodulating the corresponding reflection wavelength drift. This can eliminate the influence of temperature on flow detection while doubling the sensitivity of the fiber Bragg grating flow meter, effectively improving the measurement accuracy.

[0019] 2. The target plate and cantilever beam can both be manufactured using an integrated processing technology. The resulting target flow meter with a special structure effectively reduces moving parts, improves the stability of the flow meter, and thus further improves the accuracy of flow detection.

[0020] 3. The flow meter adopts an "umbrella-shaped" structure, with the target plates fully distributed throughout the pipe. This allows for the detection of flow at various points in the horizontal pipe, reducing the impact of stratification caused by gravity and making the measurement of multiphase flow in the horizontal pipe more accurate.

[0021] 4. The target shape of the flow meter of the present invention is adapted to the special environment of the underground pipeline. It adopts a pear-shaped structure that is narrow at the front and wide at the back, which is more suitable for long straight horizontal underground pipelines compared with traditional circular target plates.

[0022] 5. During the process of lowering the flow meter into the well, the cantilever beam can be retracted by the retraction mechanism, thereby reducing the impact of size on the flow meter during transportation into the well, effectively solving the problem of difficult lowering of array flow meters into the well, making the overall transportation of the flow meter into the well more convenient, and having better applicability to long straight pipes with small diameter.

[0023] 6. The flow meter of the present invention is made of titanium alloy as a whole, and the target plate and cantilever beam can be processed in one piece, which has high tensile strength and hardness; at the same time, the fiber grating installed on the surface of the cantilever beam is a high temperature resistant fiber grating, which makes the entire flow meter highly adaptable to high temperature and high pressure environments.

[0024] 7. This invention, through an array of multiple cantilever beams, enables the flow meter to measure the flow rate around the entire well in harsh environments with high temperature and high pressure, while also providing high accuracy for measuring three-phase flow in horizontal and steeply inclined pipes. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the fiber optic target flowmeter of the present invention;

[0026] Figure 2 for Figure 1 Another perspective of the diagram;

[0027] Figure 3 for Figure 1 Another schematic diagram for the disclosure;

[0028] Figure 4 This is a schematic diagram of the structure of a fiber Bragg grating target flowmeter according to another embodiment of the present invention.

[0029] 1. Central fixed body; 2. Cantilever beam; 21. Slide groove; 3. Retraction mechanism; 31. Slip ring; 32. Horizontal thruster; 33. Support rod; 4. Target plate; 5. Fiber grating; 6. Conducting fiber; 7. Screw joint. Detailed Implementation

[0030] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0031] like Figure 1-3As shown, a fiber Bragg grating target flowmeter of the present invention includes a central fixed body 1, multiple cantilever beams 2, and a retraction mechanism 3; one end of each of the multiple cantilever beams 2 is hinged at a distance from one end of the central fixed body 1, and the other end of each of the multiple cantilever beams 2 is provided with a target plate 4; the retraction mechanism 3 is disposed on the central fixed body 1 and is used to retract or open the multiple cantilever beams 2; fiber Bragg gratings 5 ​​are correspondingly disposed on both sides of the cantilever beams 2, and each fiber Bragg grating 5 is connected to one end of a transmission fiber 6, and the other end of the transmission fiber 6 is connected to an external demodulation device.

[0032] In this invention, the fiber gratings 5 ​​on different surfaces of the cantilever beam 2 are located at the same position on the cantilever beam 2. When the target plate 4 experiences strain due to the impact of the fluid, since the two fiber gratings 5 ​​are located at approximately the same position, the temperature effect on the two fiber gratings 5 ​​can be considered the same. Since the fiber gratings 5 ​​are located on different surfaces of the cantilever beam 2, the stress directions are opposite. Therefore, by differentially processing the wavelength drift of the two gratings, the influence of temperature on the fiber gratings 5 ​​can be effectively eliminated, while improving the sensitivity of the fiber gratings 5. The other ends of the two grating fibers are connected to an external demodulation device through a transmission fiber 6. The external demodulation device can calculate and analyze the flow rate of the pipeline fluid by demodulating the corresponding reflection wavelength drift. This can eliminate the influence of temperature on flow detection and double the sensitivity of the fiber grating 5 flow meter, effectively improving the measurement accuracy.

[0033] The flow meter adopts an "umbrella-shaped" structure, with the target plate 4 fully distributed throughout the pipe. This allows for the detection of flow at various points in the horizontal pipe, reducing the impact of stratification caused by gravity and making the measurement of multiphase flow in the horizontal pipe more accurate.

[0034] During the process of lowering the flow meter into the well, the cantilever beam 2 can be retracted by the retraction mechanism 3, thereby reducing the impact of the size of the flow meter during the transportation process in the well, effectively solving the problem of the difficulty of lowering the array flow meter into the well, making the overall transportation of the flow meter in the well more convenient, and having better applicability to long straight pipes with small diameter.

[0035] The structure of the retracting mechanism 3 can vary, and is not limited here. In feasible implementations, the retracting mechanism 3 may include a slip ring 31, a horizontal pusher 32, and multiple support rods 33. The slip ring 31 is slidably sleeved on the central fixed body 1, and one end of each of the multiple support rods 33 is hinged to the cantilever beam 2 (e.g., ...). Figure 1As shown, the other ends of multiple support rods 33 are hinged to slip rings 31. A horizontal pusher 32 is set in the central fixed body 1, and its driving end is connected to the slip ring 31 to drive the slip ring 31 to slide back and forth along the central fixed body 1. The flow meter is transported to the preset position of the pipeline in a retracted state. When it is transported to the preset position, the horizontal pusher 32 pushes the slip ring 31 to move toward the cantilever beam 2, the support rods 33 open, and push the cantilever beam 2 to unfold, similar to the opening of an umbrella.

[0036] like Figure 4 As shown, in another possible implementation, the retracting mechanism 3 may include a slip ring 31, a horizontal pusher 32 and multiple support rods 33. The slip ring 31 is slidably sleeved on the central fixed body 1, and one end of the support rod 33 is slidably connected to the cantilever beam 2 in a one-to-one correspondence. Specifically, the cantilever beam 2 has a groove 21 on the side near the slip ring 31, and one end of the support rod 33 is slidably disposed in the groove 21.

[0037] The target plate 4 and the cantilever beam 2 can be integrally molded, which effectively reduces the number of moving parts, improves the stability of the flow meter, and thus further improves the accuracy of flow detection.

[0038] The target plate 4 is designed to adapt to the special environment of the downhole pipeline. The target plate 4 can be pear-shaped. The width of the end of the target plate 4 away from the cantilever beam 2 is greater than that of the end closer to the cantilever beam 2. The pear-shaped structure described above is more suitable for long straight horizontal pipelines in downholes compared with the traditional circular target plate 4.

[0039] The number of cantilever beams 2 can vary. In this embodiment, there are six cantilever beams 2, which are arranged at equal angular intervals on the central fixed body 1, forming a circular array around the fixed end with a 60-degree interval between each other. This array of six cantilever beams 2 enables the flow meter to measure the flow rate around the entire well circumference under harsh high-temperature and high-pressure conditions, while also providing high accuracy for measuring three-phase flow in horizontal and steeply inclined pipes.

[0040] Both cantilever beams can adopt a rectangular sheet structure.

[0041] The other end of the central fixing body 1 may also be provided with a screw port 7 for connecting to external equipment, so as to facilitate connection with external equipment.

[0042] The fiber grating 5 fixed to the surface of the cantilever beam 2 is a high-temperature resistant fiber grating 5. It is first encapsulated and then fixed by welding process, and has high high temperature and high pressure resistance.

[0043] For any points not covered above, existing technologies shall apply.

[0044] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A fiber optic target flow meter, characterized in that, It includes a central fixed body (1), multiple cantilever beams (2) and a retracting mechanism (3); one end of each of the multiple cantilever beams (2) is hinged at a distance to one end of the central fixed body (1), and the other end of each of the multiple cantilever beams (2) is provided with a target plate (4). The retracting mechanism (3) is set on the central fixed body (1) and is used to retract or open the multiple cantilever beams (2); fiber optic gratings (5) are correspondingly provided on both sides of the cantilever beams (2), and each fiber optic grating (5) is connected to one end of a transmission fiber (6), and the other end of the transmission fiber (6) is connected to an external demodulation device.

2. The fiber optic target flowmeter as described in claim 1, characterized in that, The retraction mechanism (3) includes a slip ring (31), a horizontal pusher (32), and multiple support rods (33). The slip ring (31) is slidably sleeved on the central fixed body (1). One end of each of the multiple support rods (33) is hinged or slidably connected to the cantilever beam (2) in a one-to-one correspondence. The other end of each of the multiple support rods (33) is hinged to the slip ring (31). The horizontal pusher (32) is located on the central fixed body (1), and its driving end is connected to the slip ring (31) in a transmission connection to drive the slip ring (31) to slide back and forth along the central fixed body (1).

3. The fiber optic target flowmeter as described in claim 2, characterized in that, One end of the support rod (33) is slidably connected to the cantilever beam (2). The cantilever beam (2) has a groove (21) on the side near the slip ring (31). One end of the support rod (33) is slidably disposed in the groove (21).

4. The fiber optic target flowmeter as described in claim 1, characterized in that, The target piece (4) is integrally formed with the cantilever beam (2).

5. A fiber optic target flowmeter as described in claim 1, characterized in that, The target piece (4) is pear-shaped, and the width of the end of the target piece (4) away from the cantilever beam (2) is greater than the width of the end of the target piece (4) close to the cantilever beam (2).

6. The fiber optic target flowmeter as described in claim 1, characterized in that, The number of cantilever beams (2) is six, and the six cantilever beams (2) are arranged at equal angular intervals on the central fixing body (1).

7. A fiber optic target flow meter as described in claim 1, characterized in that, The other end of the central fixing body (1) is also provided with a screw hole (7) for connecting to external equipment.

8. A fiber optic target flowmeter as described in claim 1, characterized in that, The fiber optic target flowmeter is made of titanium alloy.

9. A fiber optic target flowmeter as described in claim 1, characterized in that, The cantilever beam (2) is a rectangular thin sheet.

10. A fiber optic target flowmeter as described in claim 1, characterized in that, The fiber grating (5) is a high-temperature resistant fiber grating (5) and is fixed to the cantilever beam (2) by welding.

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