Temperature and pressure sensor based on fiber bragg grating

Abstract

The invention discloses a temperature and pressure sensor based on a fiber bragg grating, and relates to the technical field of oil well pressure testing, the temperature and pressure sensor based on the fiber bragg grating comprises a tail plug, a special optical fiber and a temperature and pressure testing structure, the temperature and pressure testing structure comprises a sensing shell, a comb-shaped inductor, a first axial fixator, a second axial fixator and a temperature grating, a comb-shaped inductor is arranged on the special optical fiber, the comb-shaped inductor is in contact with the sensing shell, the special optical fiber is arranged in the sensing shell, the first axial fixator and the second axial fixator are arranged at the two ends of the comb-shaped inductor, and a temperature grating used for data compensation is further arranged on the special optical fiber. The hydrogen loss protection sleeve is installed in the sensing shell, the hydrogen loss protection tube is arranged outside the special optical fiber, and compared with a traditional sensor, the sensor is smaller in size and better in sealing performance and can detect more places at the same time, so that the problem that the structure of the sensor is large is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of engineering elements and components, and in particular to a temperature and pressure sensor based on optical fiber grating. Background Art

[0002] The traditional oil well pressure detection method is to use one sensor to correspond to one optical cable. If you want to detect the pressure in many places, you need multiple pressure sensors and multiple optical cables. If the number of optical cables increases, the size of the entire equipment will increase, and the annulus of the oil well for installing auxiliary detection equipment is limited, which makes it impossible to install it in the oil well. More importantly, installing multiple optical cables on the equipment will greatly increase the difficulty of sealing the oil wellhead. The more optical cables there are, the more sealing points there are. Oil leakage at any sealing point will be a safety accident. The main goal of the present invention is to solve the problem of how to use a temperature and pressure sensor that only requires one optical fiber to accurately and real-time measure the temperature and pressure data of multiple places in a high temperature and high pressure environment or in an environment with high anti-interference ability. The temperature and pressure sensor is small in size and easy to install in an oil well. Summary of the invention

[0003] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a temperature and pressure sensor based on fiber gratings, which can solve the above-mentioned problem.

[0004] To achieve the above object, the present invention provides the following technical solutions: a temperature and pressure sensor based on fiber grating, comprising a tail plug, a special optical fiber, a test adapter and a temperature and pressure test structure, wherein the temperature and pressure test structure comprises a sensing housing, a comb-shaped sensing body, an axial fixer 1 and an axial fixer 2, the special optical fiber is arranged on the comb-shaped sensing body, the comb-shaped sensing body is in contact with the sensing housing, the special optical fiber is inside the sensing housing, and a grating is arranged on the special optical fiber;

[0005] The axial fixer 1 and the axial fixer 2 are arranged at two ends of the comb-shaped inductor, and the axial fixer 1 and the axial fixer 2 are used to fix the comb-shaped inductor;

[0006] The grating is in contact with the comb-shaped sensing body;

[0007] The special optical fiber is also equipped with a temperature grating for data compensation; a hydrogen loss protection sleeve is installed inside the sensor housing;

[0008] A hydrogen damage protection tube is provided on the outside of the special optical fiber.

[0009] Preferably, the prestress of the special optical fiber during installation is greater than 0.5 nm, and the welding tension is greater than 20N.

[0010] Preferably, the prestress of the comb-shaped inductor is greater than 0.5 nm.

[0011] Preferably, the temperature and pressure test structure is configured as a tubular structure.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] Compared with traditional sensors, this fiber Bragg grating-based temperature and pressure sensor realizes series connection of multiple sensor structures on one optical fiber through the conversion of comb-shaped sensing bodies. It has better sealing performance and avoids the problem of large sensor structure. It is easy to install in oil wells, reduces the accident rate and improves safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention is further described below in conjunction with the accompanying drawings and embodiments:

[0015] Figure 1 This is a schematic diagram of a temperature and pressure sensor based on fiber grating of the present invention.

[0016] Figure numerals: 1. tail plug; 2. sensor housing; 3. special optical fiber; 4. axial holder 2; 5. test adapter; 6. axial holder 1; 7. hydrogen loss protection sleeve; 8. comb-shaped sensor; 9. hydrogen loss protection tube; 10. temperature grating; 11. grating. DETAILED DESCRIPTION

[0017] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0018] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do 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 should not be understood as a limitation on the present invention.

[0019] In the description of the present invention, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0020] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0021] See also Figure 1 The present invention provides a technical solution: a temperature and pressure sensor based on fiber grating, the temperature and pressure sensor based on fiber grating can be changed in quantity according to demand when in use, a temperature and pressure sensor based on fiber grating, comprising a tail plug 1, a special optical fiber 3, a test adapter 5 and a temperature and pressure test structure, and a grating 11 is arranged on the special optical fiber 3;

[0022] The grating 11 is a notch on the special optical fiber 3. When the temperature or external force changes, the spacing of the grating 11 will change, and the wavelength of the demodulator will change;

[0023] The temperature and pressure test structure includes a sensing housing 2, a comb-shaped sensing body 8, an axial fixer 1 6 and an axial fixer 2 4, a special optical fiber 3 is arranged on the comb-shaped sensing body 8, the comb-shaped sensing body 8 is in contact with the sensing housing 2, and the special optical fiber 3 is inside the sensing housing 2;

[0024] The axial fixer 1 6 and the axial fixer 2 4 are arranged at both ends of the comb-shaped inductor 8, and the axial fixer 1 6 and the axial fixer 2 4 are used to fix the comb-shaped inductor 8;

[0025] The grating 11 is in contact with the comb-shaped induction body 8;

[0026] The special optical fiber 3 is also provided with a temperature grating 10 for data compensation; a hydrogen loss protection sleeve 7 is installed inside the sensing housing 2;

[0027] A hydrogen damage protection tube 9 is provided outside the special optical fiber 3;

[0028] If there are multiple fiber Bragg grating based temperature and pressure sensors in use, both ends of the fiber Bragg grating based temperature and pressure sensor in the middle are connected using a test adapter 5;

[0029] If a plurality of fiber Bragg grating-based temperature and pressure sensors are used, the plurality of fiber Bragg grating-based temperature and pressure sensors are connected in series with the special optical fiber 3 .

[0030] Among them, the prestress of the special optical fiber 3 during installation is greater than 0.5nm, and the welding tension is greater than 20N.

[0031] The prestress of the comb-shaped induction body 8 is greater than 0.5 nm.

[0032] Among them, the temperature and pressure test structure is set as a tubular structure.

[0033] The sensor housing 2 is made of corrosion-resistant metal.

[0034] Compared with traditional sensors, this temperature and pressure sensor based on fiber grating is smaller in size and has better sealing. It can also detect more places, thereby reducing costs. This solution can connect multiple sensors in series on one optical fiber through the conversion of comb-shaped sensors, thus avoiding the problem of large sensor structure and the problem of poor sealing caused by multiple optical fibers, reducing the accident rate and improving safety.

[0035] Working principle: The sensor is installed in the oil well. The sensor generates micro-strain through the pressure on the strain areas on both sides. The comb-shaped sensing body is squeezed by the sensing shell. The comb-shaped sensing body transmits the micro-strain to the fiber grating and converts it into the axial variation of the fiber grating, thereby generating a change in the optical signal. By obtaining the central wavelength of the comb-shaped sensing body and the central wavelength of the temperature grating, combined with the temperature compensation of the temperature grating, the specific pressure value corresponding to the micro-strain is demodulated.

[0036] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present invention.

Claims

1. A temperature and pressure sensor based on fiber Bragg grating, comprising a tail plug (1), a special optical fiber (3), a test adapter (5) and a temperature and pressure test structure, characterized in that: The temperature and pressure test structure comprises a sensing housing (2), a comb-shaped sensing body (8), an axial fixer 1 (6) and an axial fixer 2 (4); the special optical fiber (3) is arranged on the comb-shaped sensing body (8), the comb-shaped sensing body (8) is in contact with the sensing housing (2), the special optical fiber (3) is inside the sensing housing (2), and a grating (11) is arranged on the special optical fiber (3); Axial fixer 1 (6) and axial fixer 2 (4) are arranged at two ends of the comb-shaped induction body (8); The grating (11) is in contact with the comb-shaped induction body (8) A temperature grating (10) for data compensation is also provided on the special optical fiber (3); a hydrogen damage protection sleeve (7) is installed inside the sensor housing (2); A hydrogen damage protection tube (9) is provided outside the special optical fiber (3).

2. The fiber Bragg grating-based temperature and pressure sensor according to claim 1, characterized in that: The prestress of the special optical fiber (3) during installation is greater than 0.5 nm, and the welding tension is greater than 20 N.

3. The fiber Bragg grating-based temperature and pressure sensor according to claim 1, characterized in that: The prestress of the comb-shaped induction body (8) is greater than 0.5 nm.

4. The temperature and pressure sensor based on fiber Bragg grating according to claim 1, characterized in that: The temperature and pressure test structure is configured as a tubular structure.

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