Mounting type temperature and pressure measuring optical fiber sensor

Abstract

The mounting type temperature and pressure measuring optical fiber sensor belongs to the technical field of sensors. The optical fiber sensor integrated module integrates a temperature monitoring unit and a pressure monitoring unit, and is provided with dimethyl silicone oil in the optical fiber sensor, which can protect the optical fiber from damage, prevent the optical fiber from corrosion and effectively transmit the change of external pressure. Through the optimization design and combination of the optical fiber sensor on various sensing units, the efficient comprehensive monitoring of temperature and pressure can be realized, the temperature and pressure integrated monitoring can be realized, the complex temperature and pressure in the wellbore can be monitored in real time, the complex structure of the optical fiber sensor is simplified, and a convenient, reliable and efficient monitoring tool is provided for the practical engineering application of carbon dioxide storage.

Description

Technical Field

[0001] This invention relates to the field of oil and gas resource development and carbon dioxide geological storage monitoring, and particularly to a mounted fiber optic sensor for temperature and pressure measurement. Background Technology

[0002] With the continuous development of fiber optic sensing technology, it has been widely applied in fields such as carbon dioxide geological storage. This avoids the limitations of traditional sensors, allowing fiber optic sensors to operate in environments with difficult deployment, strong electromagnetic interference, and high corrosiveness. During geological storage, some of the carbon dioxide injected into the formation is fixed within the geological layer through physical and chemical processes. Another portion migrates laterally and vertically along the geological layer, while a small portion escapes along geological defects and well walls into the soil, atmosphere, and other areas, posing a potential leakage risk. Real-time monitoring is necessary to ensure the integrity of the wellbore. In actual engineering projects, the environmental conditions within the wellbore, such as temperature and pressure, are complex, making it difficult to effectively monitor the entire storage process. Furthermore, current fiber optic sensors used for wellbore integrity monitoring often require multiple sensors to be deployed separately, creating a cumbersome problem. Summary of the Invention

[0003] To overcome the problems existing in the prior art, this invention proposes a novel mounted temperature and pressure fiber optic sensor that optimizes the structure and improves the performance of the fiber optic sensor. This sensor enables integrated temperature and pressure measurement for wellbore monitoring, greatly simplifies the arrangement of sensors inside the wellbore, and provides a more reliable real-time monitoring solution for wellbore monitoring in practical engineering, so as to accurately grasp the complex environment inside the wellbore.

[0004] The technical solution adopted in this invention is: a mounted temperature and pressure fiber optic sensor, which includes a sensor sidewall, a sensor cavity, a pressure fiber optic grating and a temperature fiber optic grating, and a metal diaphragm supported by a metal diaphragm support frame is disposed above the sensor sidewall;

[0005] The sensor's inner cavity is equipped with a first fiber stage and a second fiber stage on its base; the pressure fiber grating is disposed between the first fiber stage and the second fiber stage, and the pressure fiber grating is connected to a metal diaphragm via a pressure connecting rod.

[0006] The temperature fiber grating is disposed between the first fiber stage and the sensor sidewall, and between the second fiber stage and the sensor sidewall.

[0007] Furthermore, the sensor cavity is filled with dimethyl silicone oil, and the pressure fiber grating and temperature fiber grating are impregnated in dimethyl silicone oil.

[0008] Furthermore, the temperature fiber grating is in a pre-stretched state, and the pressure fiber grating is in a taut state.

[0009] Furthermore, metal sleeves are installed on both sides of the fiber optic station to fix the fiber optic grating.

[0010] Furthermore, the optical fiber of the optical fiber sensor is threaded through a metal sleeve, and the optical fiber is provided with a pressure fiber grating and a temperature fiber grating connected in series.

[0011] Furthermore, pressure fiber gratings and temperature fiber gratings are collectively referred to as fiber gratings, and the outer layer of a fiber grating is provided with a cladding and a protective layer.

[0012] Furthermore, under external pressure, the metal diaphragm of the fiber optic sensor deforms, and the deformation is transmitted to the pressure fiber grating through the pressure sensing link, causing the pressure fiber grating to deform and resulting in a change in the grating pitch, which in turn causes a change in the wavelength of the reflected light. By measuring the change in the wavelength of the reflected light, the pressure can be measured.

[0013] Furthermore, the pressure fiber grating in the fiber optic sensor is affected by both temperature and pressure, while the temperature fiber grating is only affected by temperature. Within the linear range of the gratings, the wavelengths of the pressure and temperature fiber gratings are related to the changes in pressure and temperature as follows:

[0014]

[0015] Where: K P1 λ is the pressure coefficient of the pressure fiber grating, and P is the ambient pressure; where λ is proportional to P; when the value of λ is measured, the ambient pressure can be calculated.

[0016] Through the above technical solution, the present invention has the following beneficial effects:

[0017] This invention integrates temperature, pressure, and strain sensors with optical fibers, greatly simplifying the complex layout inside wellbores in practical engineering and reducing monitoring costs. It enables simultaneous overall evaluation and high-precision monitoring of temperature and pressure inside the wellbore, rather than monitoring them separately. It accurately and comprehensively explores the complex conditions inside the wellbore, providing a reliable evaluation method for actual CO2 sequestration. Attached Figure Description

[0018] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components. Those skilled in the art, guided by the teachings of this invention, can select various possible shapes and proportions to implement the invention according to specific circumstances.

[0019] Figure 1 This is a schematic diagram of the internal structure of the integrated component of the fiber optic sensor.

[0020] Figure 2 This is a schematic diagram of the optical fiber fixing sleeve.

[0021] In the figure: 1. Metal diaphragm, 2. Pressure fiber grating, 3. Temperature fiber grating, 4. Base, 5. Pressure sensing link, 6. Metal sleeve, 7. First fiber stage, 7a. Second fiber stage, 8. Fastening screw, 9. Metal diaphragm support frame, 10. Fiber grating, 11. Cladding, 12. Protective layer, 13. Dimethyl silicone oil, 14. Sensor sidewall, 15. Sensor inner cavity. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0023] like Figure 1 As shown, the present invention relates to a mounted temperature and pressure fiber optic sensor. The sensor contains a pressure fiber optic grating 2 and a temperature fiber optic grating 3. A pressure sensing rod 5 is connected to the pressure fiber optic grating, and the other end of the pressure sensing rod is connected to a metal diaphragm 1 to better measure pressure in response to external pressure changes. Metal sleeves 6 are provided at both ends of the fiber optic stage 7 to fix the fiber optic gratings.

[0024] A mountable fiber optic temperature and pressure sensor is provided, which integrates temperature and pressure monitoring units into a single module. The sensor includes a fiber Bragg pressure grating and a fiber Bragg temperature grating. It also contains dimethyl silicone oil 13, a base 4, a first fiber stage 7, a second fiber stage 7a, and fastening screws 8 for securing the sensor.

[0025] In the fiber optic sensor, metal sleeves 6 are provided at both ends of the fiber optic stage to fix the fiber optic gratings. The temperature and pressure fiber optic gratings are fixed in the metal sleeves 6 with adhesive, and a certain external force is applied to ensure that the temperature fiber optic grating is in a pre-stretched state and the pressure fiber optic grating is in a taut state.

[0026] In fiber optic sensors, the primary function of dimethyl silicone oil is to lubricate and protect the optical fiber, preventing mechanical damage and improving the sensor's stability and reliability. It also effectively prevents corrosion; its hydrophobic properties prevent moisture and humidity from damaging the fiber. Furthermore, dimethyl silicone oil exhibits excellent high and low temperature resistance, allowing for long-term use within a temperature range of -50℃ to +200℃, ensuring good performance even under extreme temperature conditions. In addition, due to its high compressibility and fluidity, dimethyl silicone oil can form a uniform medium between the metal diaphragm and the optical fiber. When the metal diaphragm is under pressure, the dimethyl silicone oil effectively transmits pressure, reducing stress concentration and localized deformation, thereby improving strain transfer efficiency.

[0027] In the fiber optic sensor, the pressure diaphragm is a metal diaphragm 1, which is fixed to the metal diaphragm support frame 9 by welding and connected to a pressure sensing link 5. When the fiber optic sensor is subjected to external pressure, the metal diaphragm 1 deforms. This deformation is transmitted to the pressure fiber optic grating 2 through the pressure sensing link 5, causing the pressure fiber optic grating 2 to deform as well. This results in a change in the grating pitch, which in turn causes a change in the wavelength of the reflected light. By measuring the change in the wavelength of the reflected light, the pressure can be measured.

[0028] In fiber optic sensors, the wavelength of the temperature-measuring fiber optic grating 3 is only affected by temperature changes. By monitoring the wavelength changes of the temperature-measuring fiber optic grating 3, information about temperature changes can be obtained.

[0029] During fiber Bragg grating installation, an external force is applied to and the temperature fiber Bragg grating is fixed in a pre-stretched state, while the pressure fiber Bragg grating is kept taut for better pressure measurement. During pressure measurement, when the metal diaphragm of the fiber optic sensor is subjected to external pressure changes, the diaphragm deforms under the pressure. This deformation is transmitted to the pressure fiber Bragg grating via a pressure sensing link, causing it to stretch and deform, resulting in a change in its wavelength. The pressure fiber Bragg grating in the sensor is affected by both temperature and pressure, while the temperature fiber Bragg grating is only affected by temperature. Therefore, within the linear range of the gratings, the wavelengths of the pressure and temperature gratings are related to pressure and temperature changes as follows:

[0030]

[0031] In the formula λ P and λ T The wavelengths, K, of the pressure fiber grating and the temperature fiber grating are respectively. P1 For the pressure coefficient of the pressure grating, K T1 and K T2 Let P and T be the temperature coefficients of the pressure fiber grating and the temperature fiber grating, respectively, and let P and T be the ambient pressure and temperature, respectively. Simplifying the above equation, we get:

[0032]

[0033] In the formula, λ is directly proportional to P. Once the value of λ is measured, the environmental pressure can be calculated.

[0034] Furthermore, the wavelength of the temperature-sensing fiber is only affected by temperature changes. By monitoring the wavelength changes of the temperature-sensing fiber grating, temperature change information can be obtained, thereby enabling temperature measurement.

[0035] The fiber optic sensor also contains dimethyl silicone oil, which lubricates and protects the optical fiber, preventing mechanical damage and improving the sensor's stability and reliability. It effectively prevents corrosion, and its hydrophobic nature prevents moisture and humidity from damaging the fiber. Furthermore, it can be used long-term over a wide temperature range, allowing the fiber to maintain good performance even under extreme temperature conditions. More importantly, due to its high compressibility and fluidity, dimethyl silicone oil can form a uniform medium between the metal diaphragm and the fiber grating. When the metal diaphragm is under pressure, the dimethyl silicone oil can effectively transmit pressure, reducing stress concentration and localized deformation, thereby improving strain transfer efficiency.

[0036] like Figure 2 As shown, the fiber optic sensor has a cladding 11 and a protective layer 12 around the fiber optic grating 10 to protect the fiber optic grating, extend its service life, and prevent it from being damaged by external forces.

[0037] Compared with the prior art, this invention has the advantages of simple structure, convenient installation, high pressure sensitivity, accurate temperature measurement, integrated temperature and pressure monitoring, durable fiber optic sensor, and effective pressure transmission by dimethyl silicone oil.

[0038] When the above-mentioned device is in operation,

[0039] (1) The fiber optic sensor integrated module, i.e. the core monitoring section, is fixed inside the well shaft using common clamps in the well. Other equipment such as power supply equipment, data acquisition and processing system are placed stably in an open area around the well.

[0040] (2) Connect the detection section equipment in step 1 in series with optical fiber, and connect the detection section equipment and power supply equipment in sequence, and perform continuity test.

[0041] (3) The temperature fiber grating and pressure fiber grating in the sensor integration module are used for monitoring respectively, and the corresponding relevant data information is obtained. After analysis and processing, the temperature and pressure information is output.

Claims

1. A mounted fiber optic sensor for temperature and pressure measurement, characterized in that: The sensor includes a sensor sidewall (14), a sensor cavity (15), a pressure fiber grating (2) and a temperature fiber grating (3), and a metal diaphragm (1) supported by a metal diaphragm support frame (9) is disposed above the sensor sidewall (14). The sensor cavity (15) has a first fiber stage (7) and a second fiber stage (7a) on the base (4); the pressure fiber grating (2) is located between the first fiber stage (7) and the second fiber stage (7a), and the pressure fiber grating (2) is connected to the metal diaphragm (1) through the pressure sensing link (5). There are two temperature fiber optic gratings (3), the first of which is set between the first fiber stage (7) and the sensor sidewall (14), and the second is set between the second fiber stage (7a) and the sensor sidewall (14). The sensor cavity (15) is filled with dimethyl silicone oil (13), and the pressure fiber grating (2) and temperature fiber grating (3) are immersed in dimethyl silicone oil (13); The temperature fiber grating (3) is in a pre-stretched state, and the pressure fiber grating (2) is in a taut state; Both sides of the first fiber stage (7) and the second fiber stage (7a) are fitted with metal sleeves (6) for fixing fiber optic gratings; the fiber optic sensor is threaded through the metal sleeves (6), and the fiber optic is provided with a pressure fiber grating (2) and a temperature fiber grating (3) connected in series.

2. The mounted temperature and pressure fiber optic sensor according to claim 1, characterized in that: The pressure fiber grating (2) and the temperature fiber grating (3) are collectively referred to as fiber grating (10). The outer layer of the fiber grating (10) is provided with a cladding (11) and a protective layer (12).

3. The mounted temperature and pressure fiber optic sensor according to claim 1, characterized in that: Under external pressure, the metal diaphragm (1) of the fiber optic sensor deforms. The deformation is transmitted to the pressure fiber grating (2) through the pressure sensing link (5), causing the pressure fiber grating (2) to deform and resulting in a change in the grating pitch, which in turn causes a change in the wavelength of the reflected light. By measuring the change in the wavelength of the reflected light, the pressure can be measured.

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