Optical fiber stress flow sensor

Abstract

The invention discloses an optical fiber stress flow sensor. A first cylinder and a second cylinder are arranged at the two ends of a hollow cavity respectively; the floater is arranged on the transmission rod; the floater is located in the center of the hollow cavity. One end of the supporting rod is arranged at the bottom of the first cylinder; the other end of the supporting rod is connected with one end of the rhombic device; the transmission rod is arranged at the other end of the rhombic device; the rhombic device is externally connected with a first spring; the other end of the first spring is arranged on the inner wall of the first cylinder; the fiber bragg grating is arranged in the rhombic device; the other end of the transmission rod is contacted with the arrow; one end of the arrow is arranged inside the second cylinder, and the other end of the arrow is arranged outside the second cylinder; the hollow cavity is provided with a channel; and the channel is used for communicating the hollow cavity with external gas. According to the invention, the interference problem possibly encountered by traditional electric signal measurement is reduced. The rhombus design not only simplifies the equipment structure, but also enhances the sensitivity to small flow velocity change.

Description

Technical Field

[0001] The present invention belongs to the technical field of downhole flow measurement and relates to an optical fiber stress flow sensor. Background Art

[0002] Traditional downhole flow sensors mainly rely on electrical signal technology, which means they convert flow information into electrical signals for reading. However, this method has obvious drawbacks in the high-temperature and high-pressure downhole environment, especially being vulnerable to electromagnetic interference. This interference may stem from other electrical equipment, metal components in ores, or other unstable factors in the well. To address these issues, traditional methods tend to perform special heat-resistant treatments on the circuits and sensors. This not only increases the size of the equipment, making it difficult to arrange and use, but also raises the manufacturing cost, further increasing the overall cost of oil and gas extraction.

[0003] Facing these problems, the industry has started actively seeking new technological alternatives. Optical fiber technology has gradually gained favor in the industry due to its unique properties and anti-interference ability. Compared with traditional electrical signal measurement, optical fiber sensors are characterized by small size, light weight, high sensitivity, and being almost immune to electromagnetic interference. This technology is based on the properties of light and is thus not easily interfered with by environmental factors such as temperature and pressure. However, how to perfectly combine optical fiber technology with flow measurement to meet the requirements of measurement accuracy and adapt to the downhole environment is a technical problem to be solved. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems in the prior art that traditional downhole flow sensors are vulnerable to electromagnetic interference in the high-temperature and high-pressure downhole environment. If special heat-resistant treatments are carried out, the size and manufacturing cost of the equipment will increase, further raising the overall cost of oil and gas extraction; and the combination of optical fiber technology and flow measurement is not yet mature, and to provide an optical fiber stress flow sensor.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] An optical fiber stress flow sensor, comprising: a first spring, a float, an optical fiber grating, a transmission rod, a rhombus device, a hollow chamber, a support rod, an arrow, a first cylinder, and a second cylinder;

[0007] The first cylinder and the second cylinder are respectively arranged at both ends of the hollow chamber; the float is arranged on the transmission rod; the float is located at the central position of the hollow chamber; one end of the support rod is arranged at the bottom of the first cylinder; the other end of the support rod is connected to one end of the rhombus device; the transmission rod is arranged at the other end of the rhombus device; the rhombus device is externally connected to the first spring; the other end of the first spring is arranged on the inner wall of the first cylinder; the fiber grating is arranged inside the rhombus device; the other end of the transmission rod contacts the arrow; one end of the arrow is arranged inside the second cylinder, and the other end of the arrow is arranged outside the second cylinder; the hollow chamber is provided with a channel; the channel is used for the hollow chamber to communicate with the external gas.

[0008] A further improvement of the present invention lies in:

[0009] Furthermore, there are several first springs; the first springs are in a freely extended state.

[0010] Furthermore, the hollow chamber is provided with a stainless steel filter screen at the channel for filtering debris; the channel is spiral.

[0011] Furthermore, the rhombus device is composed of four stainless steel sheets overlapping end to end in sequence, and the four vertices of the rhombus device are fixed by screw nuts, and a horizontal thrust or pull force causes the rhombus device to generate a quantitative strain.

[0012] Furthermore, an upper support ring is arranged at the top of the first cylinder; a lower support ring is arranged at one end of the second cylinder; the transmission rod passes through the upper support ring and the lower support ring in sequence and contacts the arrow.

[0013] Furthermore, a second spring is arranged at the end of the transmission rod in contact with the arrow; the second spring is used to buffer the acting force of the transmission rod on the arrow.

[0014] Furthermore, there are several channels; the apertures of the channel openings are the same and are symmetrically arranged with respect to the center of the float.

[0015] Furthermore, the first springs are evenly arranged on both sides of the rhombus device.

[0016] Furthermore, a micro temperature sensing unit is arranged inside the first cylinder, and the micro temperature sensing unit is used for measuring the temperature inside the first cylinder.

[0017] Furthermore, a micro acceleration sensing unit is arranged at the bottom of the float; the micro acceleration sensing unit is used for measuring the gas flow rate passing through the through hole.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention uses a float as a fluid flow transmission component, uses a transmission rod to transmit the float displacement to the optical fiber strain sensor, monitors the central wavelength of the optical fiber Bragg grating in real time through ground demodulation equipment, and displays the downhole fluid flow rate through subsequent signal processing; the present invention reduces the interference problem that may be encountered in traditional electrical signal measurement.

[0020] Furthermore, the present invention has a simple structure and is easy to implement; the diamond design not only simplifies the device structure, but also enhances its sensitivity to small flow rate changes; and the high temperature resistant glue further enhances the stability in harsh environments. Brief Description of the Figures

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present invention and 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.

[0022] Figure 1 is a schematic diagram of the structure of the optical fiber stress flow sensor of the present invention;

[0023] Figure 2 This is a diagram showing the relationship between the force on the fiber Bragg grating and the deformation of the fiber.

[0024] Among them, 1-first spring; 2-fiber grating; 3-transmission rod; 4-upper supporting ring; 5-channel; 6-float; 7-lower supporting ring; 8-telescopic space; 9-arrow; 10-first cylinder; 11-second cylinder; 12-hollow chamber; 13-support rod; 14-second spring. Specific implementation method

[0025] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely 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 them. 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.

[0026] 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 claimed invention, 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.

[0027] It should be noted that like reference numerals and letters denote like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

[0028] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship in which the product of the invention is usually placed during use. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0029] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0030] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "connected" are used, they 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 directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0031] The present invention will be further described in detail below with reference to the accompanying drawings:

[0032] See Figure 1 , the present invention discloses an optical fiber stress flow sensor, including: a first cylinder 10 and a second cylinder 11 are respectively arranged at both ends of a hollow chamber 12; a float 6 is arranged on a transmission rod 3; the float 6 is located at the central position of the hollow chamber 12; one end of a support rod 13 is arranged at the bottom of the first cylinder 10; the other end of the support rod 13 is connected to one end of a rhombus device; the transmission rod 3 is arranged at the other end of the rhombus device; the rhombus device is externally connected to a first spring 1; the other end of the first spring 1 is arranged on the inner wall of the first cylinder 10; an optical fiber grating 2 is arranged inside the rhombus device; the other end of the transmission rod 3 contacts an arrow 9; one end of the arrow 9 is arranged inside the second cylinder 11, and the other end of the arrow 9 is arranged outside the second cylinder 11; the hollow chamber 12 is provided with a channel 5; the channel 5 is used for the hollow chamber 12 to communicate with the outside gas.

[0033] There are several first springs 1, and the first springs 1 are in a freely extended state. The hollow chamber 12 is provided with a stainless steel filter screen at the channel 5 for filtering debris; the channel 5 is spiral. The diamond-shaped device is composed of four stainless steel sheets overlapping end to end in sequence, and the four vertices of the diamond-shaped device are fixed by screw nuts, and a horizontal thrust or pull force causes the diamond-shaped device to generate a quantitative strain. The top of the first cylinder 10 is provided with an upper support ring 4; one end of the second cylinder 11 is provided with a lower support ring 7; the transmission rod 3 passes through the upper support ring 4 and the lower support ring 7 in sequence and contacts the arrow 9. One end of the transmission rod 3 in contact with the arrow 9 is provided with a second spring 14; the second spring 14 is used to buffer the acting force of the transmission rod 3 on the arrow 9. There are several channels 5; the apertures of the openings of the channels 5 are the same, and they are symmetrically arranged with respect to the center of the float 6. The first springs 1 are evenly arranged on both sides of the diamond-shaped device. A micro temperature sensing unit is arranged inside the first cylinder 10, and the micro temperature sensing unit is used to measure the temperature inside the first cylinder. A micro acceleration sensing unit is arranged at the bottom of the float 6; the micro acceleration sensing unit is used to measure the gas flow rate passing through the through hole 5.

[0034] Downhole fluid enters a precisely designed hollow chamber 12, and there is a float 6 inside the chamber, which is stably supported by a transmission rod horizontally passing through its center. The transmission rod 3 is connected to both sides of the hollow chamber 12 to ensure that the float 6 is always perpendicular to the bottom of the chamber and located at its central position. To regulate the fluid flow, evenly distributed channels 5 are provided around the hollow chamber 12, allowing the fluid to flow in from one side and out from the other side.

[0035] When the fluid flows through at a certain speed, its flow will cause the float 6 to have a horizontal displacement. To accurately monitor this displacement and convert it into flow rate data, a diamond-shaped device is connected to the left side of the transmission rod 3. Inside the diamond-shaped device, there is a highly sensitive fiber grating 2, whose main task is to detect the horizontal displacement of the float 6 and the transmission rod 3 caused by the fluid flow rate. To ensure its stability, the diamond-shaped device is fixed to the inner side of the first cylinder 10 by six first springs 1 of the same specification. During the test, the diamond-shaped device is vertically placed in the well and always maintains a vertical central position.

[0036] The diamond-shaped device strain device is composed of four stainless steel bars, which are spliced with each other to form a diamond-shaped telescopic structure, and the four corners are fixed by screw nuts. By adjusting the screw nuts, when the transmission rod 3 is subjected to a vertical acting force, the diamond-shaped device will correspondingly undergo a slight deformation, and this slight deformation is detected by the fiber grating 2 bonded at the diagonal of the diamond.

[0037] The first cylinder 10 protects the rhombic device structure, which can cope with the high temperature and high pressure environment underground. When the first cylinder 10 is placed vertically, a weight is fixed at the bottom, so that the sensor always remains vertically stable. The float 6 is made of special ceramics, which has strong stability and durability and can meet the use requirements of the sensor under high temperature and high pressure conditions.

[0038] The inner wall of the hollow chamber 12 is coated with a special coating with anti-corrosion and high-temperature resistance characteristics, which helps to extend the life of the sensor device. To monitor the vibration condition underground in real time, a micro acceleration sensing unit is added to the bottom of the float 6, and the micro acceleration sensing unit is used to measure the gas flow rate through the through hole 5.

[0039] The rhombic fiber optic strain sensing structure is fixed to the middle of the first cylinder 10 through six fixing points in the vertical direction and the same number of first springs 1. The fiber Bragg grating 2 is fixed to two points in the horizontal direction of the rhombic structure through high-temperature resistant glue. One end of the rhombic structure is connected to the transmission rod 3, and the transmission rod 3 passes through the upper support ring 4, the float 6 and the lower support ring 7 respectively; the float 6 is located inside the entire hollow chamber 12, and four rectangular channels 5 are respectively dug around the hollow chamber 12 for fluid inlet and outlet, and stainless steel filters are nested in the 4 channels to filter out debris. The other end of the transmission rod 3 is fixed to the second spring 14 in the telescopic space 8, and the tail of the structure is the load 9.

[0040] The inner diameter of the fiber Bragg grating is 9μm, the outer diameter is 125μm, the length of the fiber Bragg grating is 2cm, and the central wavelength is 1550nm, which is used to monitor stress.

[0041] Embodiment: One end of the fiber Bragg grating 2 is inserted from the installation hole on the left side of the sensor, and the fiber Bragg grating 2 is fixed at both ends in the horizontal direction of the rhombic structure by casting glue. One end of the support rod 13 is arranged at the bottom of the first cylinder 10; the other end of the support rod 13 is connected to the left end of the rhombic device, and the right side of the rhombic device is connected to the transmission rod 3; when a prestress is applied in the horizontal direction, the upper and lower first springs 1 are in a stretched state. The transmission rod 3 passes through the upper support ring 4, the float 6 and the lower support ring 7 in sequence, and there is a telescopic space 8 at the right end of the transmission rod 3, and the float 6 is in the middle of the hollow chamber 12 to transfer the fluid flow rate.

[0042] In the application environment, the strain of the fiber Bragg grating 2 is mainly caused by the micro strain between the diagonals in the horizontal direction of the rhombus. By obtaining the relationship between the fluid flow rate and the horizontal micro strain of the rhombus through experiments, and establishing an expression relationship between the wavelength change amount Δλ and the fluid flow rate Δx, the corresponding flow rate value of the environment can be obtained. Therefore, to verify the effectiveness of this invention, the following structural simulations are to be carried out: such as Figure 2As shown, when a tensile force of about 10 N is applied to the right end of the fiber Bragg grating 2, the deformation of the fiber Bragg grating 2 is about 0.0052 mm. Therefore, by applying this strain structure, a mathematical model between the offset of the grating center wavelength and the displacement of the float can be established, so as to realize the implementation monitoring of the downhole fluid flow rate.

[0043] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An optical fiber stress flow sensor, characterized in that: include: A first spring (1), a float (6), a fiber grating (2), a transmission rod (3), a diamond-shaped device, a hollow chamber (12), a support rod (13), an arrow (9), a first cylinder (10) and a second cylinder (11); The first cylinder (10) and the second cylinder (11) are respectively arranged at two ends of the hollow chamber (12); the float (6) is arranged on the transmission rod (3); the float (6) is located at the center of the hollow chamber (12); one end of the support rod (13) is arranged at the bottom of the first cylinder (10); the other end of the support rod (13) is connected to one end of the diamond-shaped device; the transmission rod (3) is arranged at the other end of the diamond-shaped device; the diamond-shaped device is externally connected to a first spring (1); The other end of the first spring (1) is arranged on the inner wall of the first cylinder (10); the optical fiber grating (2) is arranged inside the rhombus device; the other end of the transmission rod (3) is in contact with the arrow (9); one end of the arrow (9) is arranged inside the second cylinder (11), and the other end of the arrow (9) is arranged outside the second cylinder (11); the hollow chamber (12) is provided with a channel (5); the channel (5) is used for the hollow chamber (12) to communicate with the external gas.

2. The optical fiber stress flow sensor according to claim 1, characterized in that: There are a plurality of first springs (1); the first springs (1) are in a freely extended state.

3. The optical fiber stress flow sensor according to claim 2, characterized in that: The hollow chamber (12) is provided with a stainless steel filter at the channel (5) for filtering out debris; the channel (5) is spiral.

4. The optical fiber stress flow sensor according to claim 3, characterized in that: The diamond device is composed of four stainless steel sheets overlapped end to end in sequence. The four vertices of the diamond device are fixed by screw nuts. Horizontal thrust or tension causes the diamond device to produce quantitative strain.

5. The optical fiber stress flow sensor according to claim 4, characterized in that: An upper supporting ring (4) is arranged at the top of the first cylinder (10); a lower supporting ring (7) is arranged at one end of the second cylinder (11); the transmission rod (3) passes through the upper supporting ring (4) and the lower supporting ring (7) in sequence and contacts with the arrow (9).

6. The optical fiber stress flow sensor according to claim 5, characterized in that: A second spring (14) is provided at one end of the transmission rod (3) that contacts the arrow (9); the second spring (14) is used to buffer the force of the transmission rod (3) on the arrow (9).

7. The optical fiber stress flow sensor according to claim 6, characterized in that: There are a plurality of channels (5); the opening diameters of the channels (5) are consistent and are opened symmetrically relative to the center of the float (6).

8. The optical fiber stress flow sensor according to claim 7, characterized in that: The first springs (1) are evenly arranged on both sides of the diamond-shaped device.

9. The optical fiber stress flow sensor according to claim 8, characterized in that: A micro temperature sensing unit is arranged inside the first cylinder (10), and the micro temperature sensing unit is used to measure the temperature inside the first cylinder.

10. The optical fiber stress flow sensor according to claim 9, characterized in that: A micro acceleration sensor unit is arranged at the bottom of the float (6); the micro acceleration sensor unit is used to measure the flow rate of the gas passing through the through hole (5).

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