Hanging type temperature and pressure measuring optical fiber sensor

Abstract

The invention discloses a mounting type temperature and pressure measuring optical fiber sensor, and belongs to the technical field of sensors. The optical fiber sensor integrated module integrates a temperature monitoring unit and a pressure monitoring unit, and meanwhile, dimethyl silicone oil is filled in the optical fiber sensor, so that the optical fiber sensor integrated module has the effects of protecting an optical fiber from being damaged, preventing the optical fiber from being corroded, effectively transmitting external pressure change and the like. Various sensing units are optimally designed and combined through the optical fiber sensor, efficient and comprehensive monitoring of temperature and pressure can be achieved, temperature and pressure integrated monitoring is achieved, complex temperature and pressure conditions in a shaft can be monitored in real time, the complex structure of the optical fiber sensor is simplified, and the cost is reduced. A convenient, reliable and efficient monitoring tool is provided for practical engineering application of carbon dioxide sequestration.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil and gas resource development and carbon dioxide geological storage monitoring, in particular to a hanging type temperature and pressure measuring optical fiber sensor. BACKGROUND

[0002] At present, with the continuous development of optical fiber sensing technology, it has been widely used in carbon dioxide geological storage and other fields, which can avoid the use of various traditional sensors being limited, and the optical fiber sensor can work in difficult to arrange, strong electromagnetic interference and strong corrosive environment. During the geological storage process, part of the carbon dioxide injected into the formation is fixed in the geological layer through physical and chemical action, another part migrates horizontally and vertically along the geological layer, and a small part leaks to the soil, atmosphere and other places along the geological defects, well wall and other parts, which may leak, and needs to be monitored in real time to ensure the integrity of the wellbore. In actual engineering, the temperature, pressure and other environmental conditions in the wellbore are complex, and the whole storage process cannot be well monitored. And the optical fiber sensors used for wellbore integrity monitoring at present are mostly monitored by using multiple sensors according to the monitoring needs, which causes the cumbersome problem of deploying different types of sensors respectively. SUMMARY

[0003] In order to overcome the problems existing in the prior art, the present application proposes a new hanging type temperature and pressure measuring optical fiber sensor for the structure optimization and performance improvement of the optical fiber sensor, which integrates temperature and pressure measurement for wellbore monitoring, greatly simplifies the arrangement of sensors in the wellbore, and provides a more reliable real-time monitoring scheme for the wellbore monitoring in actual engineering, so as to accurately master the complex environment in the wellbore.

[0004] The technical scheme adopted by the present application is: the hanging type temperature and pressure measuring optical fiber sensor comprises a sensor side wall, a sensor inner cavity, a pressure fiber grating and a temperature fiber grating, and a metal diaphragm supported by a metal diaphragm support frame is arranged above the sensor side wall.

[0005] A first optical fiber table and a second optical fiber table are arranged on the base in the sensor inner cavity; the pressure fiber grating is arranged between the first optical fiber table and the second optical fiber table, and the pressure fiber grating is connected to the metal diaphragm through a pressure connecting rod.

[0006] The temperature fiber grating is arranged between the first optical fiber table and the sensor side wall, and between the second optical fiber table and the sensor side wall.

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

[0008] Further, the temperature fiber grating is in a pre-stretch state, and the pressure fiber grating is in a tight state.

[0009] Further, metal sleeves are arranged on both sides of the fiber bench to fix the fiber gratings.

[0010] Further, the fiber of the fiber sensor is arranged through the metal sleeve, and the pressure fiber grating and the temperature fiber grating are connected in series on the fiber.

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

[0012] Further, under the action of external pressure, the metal diaphragm is deformed, and the deformation is transmitted to the pressure fiber grating through the pressure sensing connecting rod, so that the pressure fiber grating is deformed, the grating pitch is changed, and the wavelength of the reflected light is changed, and the pressure is measured by measuring the change of the wavelength of the reflected light.

[0013] Further, the pressure fiber grating in the fiber sensor is simultaneously affected by temperature and pressure, and the temperature fiber grating is only affected by temperature, and in the linear range of the grating, the wavelength of the pressure fiber grating and the temperature fiber grating and the pressure and temperature change have the following relationship:

[0014]

[0015] In the formula, K P1 is the pressure coefficient of the pressure fiber grating, and P is the pressure of the environment; wherein λ is proportional to P; when the value of λ is measured, the pressure of the environment can be calculated.

[0016] Through the above technical scheme, the present application has the following beneficial effects:

[0017] The present application integrates temperature, pressure and strain sensors with optical fibers, greatly simplifies the complex arrangement in the wellbore in actual engineering, reduces the monitoring cost, and can realize overall evaluation and high-precision monitoring of the temperature and pressure in the wellbore, instead of separate monitoring, accurately and comprehensively probes the complex conditions in the wellbore, and provides a reliable evaluation means for actual CO2 storage. BRIEF DESCRIPTION OF DRAWINGS

[0018] The drawings described herein are for illustrative purposes only, and are not intended to limit the scope of the present application in any way. In addition, the shapes and proportions of the components in the drawings are only illustrative, and are used to help understand the present application, and are not specific limitations on the shapes and proportions of the components of the present application. Those skilled in the art can select various possible shapes and proportions according to specific circumstances to implement the present application under the guidance of the present application.

[0019] Figure 1 The schematic diagram of the internal structure of the fiber sensor integrated component.

[0020] Figure 2 The schematic diagram of the structure of the fiber fixing sleeve.

[0021] In the figure: 1, metal diaphragm, 2, pressure fiber grating, 3, temperature fiber grating, 4, base, 5, pressure sensing connecting rod, 6, metal sleeve, 7, first fiber platform, 7a, second fiber platform, 8, fastening screw, 9, metal diaphragm support frame, 10, fiber grating, 11, cladding, 12, protective layer, 13, dimethyl silicone oil, 14, sensor side wall, 15, sensor inner cavity. DETAILED DESCRIPTION

[0022] In order to make the person skilled in the art better understand the scheme of the present application, the technical scheme in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application.

[0023] As Figure 1 shown, the present application is a mounted temperature and pressure measuring fiber sensor, which is provided with a pressure fiber grating 2 and a temperature fiber grating 3, and a pressure sensing connecting rod 5 is connected to the pressure fiber grating, and the other end of the pressure sensing connecting rod is connected to a metal diaphragm 1, so as to better measure the pressure change of the outside world. At the same time, metal sleeves 6 are arranged at both ends of the fiber platform 7, which play a role in fixing the fiber grating.

[0024] The mounted temperature and pressure measuring fiber sensor integrates a temperature monitoring and a pressure monitoring unit. In the fiber sensor, a fiber Bragg pressure grating and a fiber Bragg temperature grating are arranged. At the same time, the fiber sensor is provided with dimethyl silicone oil 13, a base 4, a first fiber platform 7, a second fiber platform 7a and a fastening screw 8 for fixing the sensor.

[0025] In the fiber sensor, metal sleeves 6 are arranged at both ends of the fiber platform to fix the fiber grating, and the temperature and pressure fiber gratings are fixed in the metal sleeves 6 through an adhesive, and a certain external force is applied to ensure that the temperature fiber grating is in a pre-stretching state and the pressure fiber grating 2 is in a taut state.

[0026] In the optical fiber sensor, the main role of the dimethyl silicone oil is to protect the optical fiber in the optical fiber sensor from mechanical damage, help to improve the stability and reliability of the sensor, and effectively prevent corrosion. Its hydrophobicity can prevent water and moisture from invading and damaging the optical fiber, and its excellent high and low temperature resistance can be used for a long time in the temperature range of-50℃ to +200℃, so that the optical fiber can maintain good performance under extreme temperature conditions. In addition, due to the high compressibility and strong flowability of dimethyl silicone oil, a uniform medium layer can be formed between the metal diaphragm and the optical fiber. When the metal diaphragm is pressed, the dimethyl silicone oil can effectively transmit the pressure and reduce stress concentration and local deformation, thereby improving the efficiency of strain transmission.

[0027] In the optical fiber sensor, the pressure diaphragm is a metal diaphragm 1 which is fixed on the metal diaphragm support frame 9 by welding and connected with the pressure sensing connecting rod 5. When the optical fiber sensor is subjected to external pressure, the metal diaphragm 1 will deform, and this deformation will be transmitted to the pressure fiber Bragg grating 2 through the pressure sensing connecting rod 5, causing the pressure fiber Bragg grating 2 to deform and change the grating pitch, thereby causing the change of the reflected light wavelength. By measuring the change of the reflected light wavelength, the pressure measurement can be realized.

[0028] In the optical fiber sensor, the wavelength of the temperature fiber Bragg grating 3 is only affected by temperature changes, and the temperature change information can be obtained by monitoring the wavelength change of the temperature fiber Bragg grating 3.

[0029] When installing the fiber Bragg grating, external force is applied to the temperature fiber Bragg grating and fixed to keep it in a pre-stretched state, and the pressure fiber Bragg grating is in a tight state to better measure the pressure. In the process of pressure measurement, when the metal diaphragm of the optical fiber sensor is subjected to external pressure changes, the metal diaphragm will deform under the action of external pressure, and the pressure will be transmitted to the pressure fiber Bragg grating through the pressure sensing connecting rod. The pressure fiber Bragg grating will be stretched and deformed, and its wavelength will change. 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 grating, the wavelengths of the pressure grating and the temperature grating and the changes of pressure and temperature have the following relationships:

[0030]

[0031] where λ P and λ T are the wavelengths of the pressure fiber Bragg grating and the temperature fiber Bragg grating, K P1 is the pressure coefficient of the pressure grating, K T1 and K T2 are the temperature coefficients of the pressure fiber Bragg grating and the temperature fiber Bragg grating, P and T are the pressure and temperature of the environment respectively. After simplifying the above formula, we get:

[0032]

[0033] In the formula, lambda is proportional to P. When the value of lambda is measured, the pressure of the environment can be calculated.

[0034] In addition, the wavelength of the temperature measuring fiber is only affected by temperature changes, and by monitoring the wavelength changes of the temperature measuring fiber grating, temperature change information can be obtained, thereby realizing temperature measurement.

[0035] The optical fiber sensor also contains dimethyl silicone oil, which has a lubricating and protective effect on the optical fiber in the optical fiber sensor, protects the optical fiber from mechanical damage, helps to improve the stability and reliability of the sensor, and can effectively prevent corrosion. Its hydrophobicity can prevent water and moisture from invading and damaging the optical fiber, and it can be used for a long time in a wide temperature range, so that the optical fiber can maintain good performance under extreme temperature conditions. More importantly, because the dimethyl silicone oil has high compressibility and strong fluidity, it can form a uniform medium between the metal diaphragm and the optical fiber grating. When the metal diaphragm is pressed, the dimethyl silicone oil can effectively transmit the pressure and reduce stress concentration and local deformation, thereby improving the efficiency of strain transmission.

[0036] As shown in Figure 2 The optical fiber grating 10 in the optical fiber sensor is surrounded by a cladding layer 11 and a protective layer 12 to protect the optical fiber grating and prolong its service life, preventing it from being damaged by external forces.

[0037] Compared with the prior art, the present application has the advantages of simple structure, easy installation, high pressure sensitivity, accurate temperature measurement, integrated temperature and pressure monitoring, durable optical fiber sensor, and effective pressure transmission of dimethyl silicone oil.

[0038] When the above device is working,

[0039] (1) The optical fiber sensor integrated module, i.e. the monitoring core section, is fixed in the wellbore by using a commonly used clamp in the well, and other equipment such as power supply equipment, data acquisition and processing system is placed stably in the empty area around the well.

[0040] (2) The detection section equipment in step 1 is connected in sequence through optical fibers, and the sequential connection of the detection section equipment and the power supply equipment is continuously checked.

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

Claims

1. Mounted temperature and pressure optical fiber sensor, characterized by: The sensor comprises a sensor side wall (14), a sensor inner cavity (15), a pressure fiber grating (2) and a temperature fiber grating (3); a metal diaphragm (1) supported by a metal diaphragm support frame (9) is provided above the sensor side wall (14); A first optical fiber stand (7) and a second optical fiber stand (7a) are provided on a base (4) in the inner cavity (15) of the sensor; the pressure optical fiber grating (2) is provided between the first optical fiber stand (7) and the second optical fiber stand (7a); the pressure optical fiber grating (2) is connected to the metal diaphragm (1) via a pressure connecting rod (5); The temperature fiber grating (3) is arranged between the first fiber stage (7) and the sensor side wall (14), and between the second fiber stage (7a) and the sensor side wall (14).

2. The mountable temperature and pressure measuring optical fiber sensor according to claim 1, characterized in that: The sensor cavity (15) is filled with dimethyl silicone oil (13), and the pressure fiber grating (2) and the temperature fiber grating (3) are immersed in the dimethyl silicone oil (13).

3. The mountable temperature and pressure measuring optical fiber sensor according to claim 1, characterized in that: The temperature optical fiber Bragg grating (3) is in a pre-stretched state, and the pressure optical fiber Bragg grating (2) is in a taut state.

4. The mountable temperature and pressure measuring optical fiber sensor according to claim 1, characterized in that: Metal sleeves (6) are installed on both sides of the optical fiber platform to fix the optical fiber grating.

5. The mountable temperature and pressure measuring optical fiber sensor according to claim 1, characterized in that: The optical fiber of the optical fiber sensor is passed through a metal sleeve (6), and a pressure optical fiber grating (2) and a temperature optical fiber grating (3) are provided on the optical fiber.

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

7. The mountable temperature and pressure measuring optical fiber sensor according to claim 1, characterized in that: Under the action of external pressure, the metal diaphragm (1) of the optical fiber sensor is deformed, and the deformation is transmitted to the pressure optical fiber Bragg grating (2) through the pressure sensing connecting rod (5), causing the pressure optical fiber Bragg grating (2) to deform, resulting in a change in the grating pitch, thereby causing a change in the wavelength of the reflected light. By measuring the change in the wavelength of the reflected light, pressure measurement is achieved.

8. The mountable temperature and pressure measuring optical fiber sensor according to claim 7, characterized in that: The pressure fiber Bragg grating in the optical fiber sensor is affected by both temperature and pressure, while the temperature fiber Bragg grating is only affected by temperature. Within the linear range of the grating, the wavelength of the pressure fiber Bragg grating and the temperature fiber Bragg grating have the following relationship with the pressure and temperature changes: ； Where: K P1 The pressure coefficient P of the pressure fiber Bragg grating is the pressure of the environment; λ is proportional to P; when the value of λ is measured, the pressure of the environment can be calculated.

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