Scissor-type fiber bragg grating temperature and pressure sensor

Abstract

The present application relates to the technical field of oil and gas well detection. Provided is a scissor-type fiber Bragg grating temperature and pressure sensor. The scissor-type fiber Bragg grating temperature and pressure sensor comprises a sensor base, a support assembly and a detection assembly, wherein two second support members and a first support member located between the two second support members are provided on the sensor base; connectors are hinged to the second support members and correspond thereto on a one-to-one basis, and the two connectors are both hinged to the first support member; and a first grating and a second grating are provided on an optical fiber, a thermally conductive expansion portion is provided on one of the two connectors, and the two connectors are both connected to the optical fiber, such that the first grating is located between the two connectors and the second grating is located on the thermally conductive expansion portion. The scissor-type fiber Bragg grating temperature and pressure sensor provided in the present application has a simple structure, can realize simultaneous measurement of temperature and pressure, and has a high integration level. A scissor-type hinged structure is formed by means of the support assembly to amplify the deformation of the sensor base caused by pressure, so that the overall stability is good, thus making the sensitivity of pressure measurement higher.

Description

Scissor type fiber grating temperature and pressure sensor

[0001] The present application claims priority from the Chinese patent application No. 202411288974.4 filed on September 13, 2024, and entitled "Fiber grating temperature and pressure sensor", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of oil and gas well detection, and in particular to a scissor type fiber grating temperature and pressure sensor. BACKGROUND

[0003] In the process of oil field exploration and production, monitoring parameters such as downhole temperature, pressure, flow rate, etc. is an important means to improve the ultimate recovery of oil and gas fields and to develop oil and gas fields scientifically and rationally.

[0004] In the related art, a thermistor temperature sensor such as Pt10, Pt20, Pt100, Pt1000, etc. is usually used to detect temperature in the oil and gas downhole, and a 0.1‰ strain pressure sensor or a quartz pressure sensor is used to detect pressure.

[0005] However, the above temperature sensor and pressure sensor exist independently, have a large volume and a complex structure, are not conducive to the miniaturization design of the annulus production profile instrument in the oil and gas downhole, and the temperature resistance of the pressure sensor cannot meet the needs in the ultra-deep well, and the quartz pressure sensor is expensive. In addition, the existing fiber grating temperature and pressure sensor is independently packaged, and the sensitivity has not reached the level of the strain pressure sensor, which cannot meet the requirements of most monitoring indicators and cannot be applied on a large scale. SUMMARY

[0006] The present application provides a scissor type fiber grating temperature and pressure sensor to solve the problems in the related art.

[0007] The application provides a scissors type fiber grating temperature and pressure sensor, which comprises a sensor base, a supporting assembly and a detecting assembly; the sensor base is used for being connected with a pressure measuring hole of an oil and gas well, and an inlet pressure groove is formed in the sensor base; the supporting assembly comprises a first supporting piece, two second supporting pieces and two connecting pieces; the first supporting piece and the two second supporting pieces are arranged on the sensor base, and the first supporting piece is located between the two second supporting pieces; the connecting pieces and the second supporting pieces are hingedly connected one by one, and the two connecting pieces are hingedly connected with the first supporting piece; the detecting assembly comprises an optical fiber, a first grating and a second grating arranged on the optical fiber; the two connecting pieces are connected with the optical fiber; the first grating is located between the two connecting pieces; one of the two connecting pieces is provided with a heat conduction expansion part, and the second grating is located on the heat conduction expansion part; the sensor base is configured to be deformed when being pressed in the inlet pressure groove; when the sensor base is deformed, the two second supporting pieces are moved relative to the first supporting piece to drive the corresponding connecting pieces to rotate towards the sensor base, so that the two connecting pieces are moved reversely.

[0008] In a possible implementation, the scissors type fiber grating temperature and pressure sensor provided by the application is characterized in that the sensor base is in a cylindrical shape, the axis of the first supporting piece coincides with the axis of the sensor base, and the two second supporting pieces are symmetrically arranged on opposite sides of the first supporting piece; and the second supporting pieces correspond to the inlet pressure grooves one by one.

[0009] In a possible implementation, the scissors type fiber grating temperature and pressure sensor provided by the application is characterized in that the distance between the groove wall of the inlet pressure groove and the side wall of the adjacent sensor base is greater than or equal to the distance between the groove bottom of the inlet pressure groove and the side of the sensor base away from the groove opening of the inlet pressure groove; and the distance between the groove bottom of the inlet pressure groove and the side of the sensor base away from the groove opening of the inlet pressure groove is 1mm-3mm.

[0010] In a possible implementation, the scissors type fiber grating temperature and pressure sensor provided by the application is characterized in that the length of the second supporting piece along the axial direction of the sensor base is less than the length of the first supporting piece along the axial direction of the sensor base.

[0011] In a possible implementation, the scissors type fiber grating temperature and pressure sensor provided by the application is characterized in that the connecting piece comprises a connecting part, the connecting part is hingedly connected with the end of the corresponding second supporting piece away from the sensor base and the end of the first supporting piece away from the sensor base in sequence; the connecting part has a connecting surface, the optical fiber is connected with the connecting surface, the heat conduction expansion part is connected with the connecting part, and the side of the heat conduction expansion part away from the sensor base is flush with the connecting surface.

[0012] In a possible implementation, the scissors-type fiber grating temperature and pressure sensor provided by the embodiment of the present application further includes a first hinged piece, the first support piece is provided with a first insertion slot, and part of the connecting part is inserted into the first insertion slot; the connecting part is provided with a sliding hole, the slot wall of the first insertion slot is provided with two first insertion holes in communication with the first insertion slot, and the first hinged piece sequentially passes through one of the two first insertion holes, the sliding hole and the other of the two first insertion holes, so that the connecting part is hinged to the first support piece.

[0013] In a possible implementation, the scissors-type fiber grating temperature and pressure sensor provided by the embodiment of the present application further includes two second hinged pieces, the second hinged pieces correspond to the connecting parts one by one, the second support piece is provided with a second insertion slot, and part of the connecting part is inserted into the second insertion slot; the connecting part is provided with a connecting hole, the slot wall of the second insertion slot is provided with two second insertion holes in communication with the second insertion slot, and the second hinged piece sequentially passes through one of the two second insertion holes, the connecting hole and the other of the two second insertion holes, so that the connecting part is hinged to the second support piece.

[0014] In a possible implementation, the scissors-type fiber grating temperature and pressure sensor provided by the embodiment of the present application, the connecting part includes a first insertion section, a first support section, a second insertion section and a second support section connected in sequence; the connecting hole is located on the first insertion section, the sliding hole is located on the second insertion section, and the second support section has a connecting surface; the distance between the center of the connecting hole and the center of the sliding hole is less than the distance between the center of the sliding hole and the connecting surface.

[0015] In a possible implementation, the scissors-type fiber grating temperature and pressure sensor provided by the embodiment of the present application, the optical fiber is a single-mode optical fiber, the single-mode optical fiber has a polyimide coating layer, and the first grating and the second grating are written by a femtosecond laser without stripping the polyimide coating layer of the single-mode optical fiber.

[0016] In a possible implementation, the scissors-type fiber grating temperature and pressure sensor provided by the embodiment of the present application, the grating region length of the first grating is 1mm-5mm, the grating region length of the second grating is equal to the grating region length of the first grating; and the difference between the center wavelength of the first grating and the center wavelength of the second grating is greater than or equal to 3nm.

[0017] The scissor type fiber grating temperature and pressure sensor provided by the application has the advantages that the sensor base is connected to the pressure measuring hole of the oil and gas well, the pressure inlet groove is formed on the sensor base, when the liquid or gas enters the pressure inlet groove, the pressure inlet groove is deformed under pressure, the two second supporting pieces move relative to the first supporting piece under the action of deformation to drive the corresponding connecting pieces to rotate towards the sensor base, the two connecting pieces are reversely moved to make the first grating be pulled to realize the detection of pressure, in addition, the second grating on the heat conduction expansion part can realize the detection of temperature under the influence of the temperature of the oil and gas well, the scissor type fiber grating temperature and pressure sensor provided by the application has the advantages of simple structure, temperature and pressure measurement, high integration, the supporting assembly forms the scissor type hinged structure to amplify the deformation of the sensor base caused by pressure, the overall stability is good, and the sensitivity of pressure measurement is higher. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate embodiments consistent with the present application and, together with the description, further serve to explain the principles of the application.

[0019] FIG. 1 is a structural schematic view of the scissor type fiber grating temperature and pressure sensor provided by the embodiment of the application;

[0020] FIG. 2 is a connection diagram one of the sensor base, the first supporting piece and the second supporting piece provided by the embodiment of the application;

[0021] FIG. 3 is a connection diagram two of the sensor base, the first supporting piece and the second supporting piece provided by the embodiment of the application;

[0022] FIG. 4 is a sectional view of FIG. 1;

[0023] FIG. 5 is another structural sectional view of the scissor type fiber grating temperature and pressure sensor provided by the embodiment of the application;

[0024] FIG. 6 is a structural schematic view of the first hinged piece in the scissor type fiber grating temperature and pressure sensor provided by the embodiment of the application;

[0025] FIG. 7 is a structural schematic view of the first supporting piece in the scissor type fiber grating temperature and pressure sensor provided by the embodiment of the application;

[0026] Fig. 8 is a structural schematic diagram of a second support in a scissor-type fiber grating temperature and pressure sensor according to an embodiment of the present application;

[0027] Fig. 9 is a structural schematic diagram of a connecting piece in a scissor-type fiber grating temperature and pressure sensor according to an embodiment of the present application.

[0028] Legend: 100 - sensor base; 101 - base body; 102 - pressure sensitive piece; 110 - pressure inlet groove; 120 - threaded interface; 200 - support assembly; 210 - first support; 220 - second support; 230 - connecting piece; 211 - first insertion groove; 212 - first insertion hole; 221 - second insertion groove; 222 - second insertion hole; 231 - thermal conduction expansion part; 232 - connecting part; 233 - connecting surface; 2321 - first insertion section; 2322 - first support section; 2323 - second insertion section; 2324 - second support section; 2325 - sliding hole; 2326 - connecting hole; 300 - detection assembly; 310 - optical fiber; 320 - first grating; 330 - second grating; 400 - first hinged piece; 500 - second hinged piece; 410 - contact part; 420 - hinged part. DETAILED DESCRIPTION

[0029] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below with reference to the drawings of the preferred embodiments of the present application. In the drawings, the same or similar notations represent the same or similar components or components with the same or similar functions throughout. The described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application. The embodiments of the present application will be described in detail below with reference to the drawings.

[0030] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be understood in a broad sense, for example, it can be fixedly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0031] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0032] The terms "first", "second", "third", "fourth" and the like in the specification and claims of the present application and the above drawings are used to distinguish similar objects, and are not necessarily used to describe a particular order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein, for example, can be implemented in an order other than those illustrated or described herein.

[0033] In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0034] As mentioned in the background, in the related art, a thermistor temperature sensor such as Pt10, Pt20, Pt100, Pt1000, etc. is generally used to detect temperature, and a 0.1 ‰ strain pressure sensor is used to detect pressure.

[0035] However, the above-mentioned temperature sensor and pressure sensor exist independently, have a large volume and a complex structure, are not conducive to the miniaturization design of the annulus fluid production profile instrument in the oil and gas downhole, and the temperature resistance of the pressure sensor cannot meet the demand in the ultra-deep well, and the quartz pressure sensor is expensive. In addition, the existing fiber Bragg grating temperature and pressure sensors are independently packaged, and the sensitivity has not reached the level of the strain pressure sensor, which cannot meet the requirements of most monitoring indicators and cannot be applied on a large scale.

[0036] Therefore, the present application provides a scissors-type fiber Bragg grating temperature and pressure sensor, which is characterized in that a first support and two second supports are arranged on the sensor base, the first support is located between the two second supports, a connecting piece is hingedly connected to each second support, and the two connecting pieces are hingedly connected to the first support; a first grating and a second grating are arranged on the optical fiber, and a heat-conducting expansion part is arranged on one of the two connecting pieces; the two connecting pieces are connected to the optical fiber, so that the first grating is located between the two connecting pieces and the second grating is located on the heat-conducting expansion part.

[0037] Therefore, when detecting the pressure under the oil and gas well, the sensor base is connected to the pressure measuring hole of the oil and gas well, and a pressure inlet groove is formed on the sensor base, so that when the liquid or gas enters the pressure inlet groove, the pressure inlet groove is deformed under pressure, the two second supporting members are moved relative to the first supporting member under the action of deformation to drive the corresponding connecting members to rotate towards the sensor base, and then the two connecting members are reversely moved to make the first grating be pulled to realize the detection of the pressure. In addition, the second grating located on the heat conduction expansion part can realize the detection of the temperature under the influence of the temperature of the oil and gas well. The scissor-type fiber grating temperature and pressure sensor provided by the application has the advantages of simple structure, temperature and pressure measurement, high integration, scissor-type hinged structure formed by the supporting assembly to amplify the deformation of the sensor base caused by pressure, good overall stability, and higher sensitivity of pressure measurement.

[0038] Hereinafter, the application will be described in detail in combination with the drawings and specific embodiments.

[0039] Referring to FIGS. 1-3, the scissor-type fiber grating temperature and pressure sensor provided by the embodiments of the application includes a sensor base 100, a supporting assembly 200 and a detection assembly 300. The sensor base 100 is used to be connected to the pressure measuring hole of the oil and gas well, and a pressure inlet groove 110 is formed on the sensor base 100. The supporting assembly 200 includes a first supporting member 210, two second supporting members 220 and two connecting members 230. The first supporting member 210 and the two second supporting members 220 are both arranged on the sensor base 100, and the first supporting member 210 is located between the two second supporting members 220. The connecting member 230 and the second supporting member 220 are hinged one by one, and the two connecting members 230 are both hinged with the first supporting member 210.

[0040] The detection assembly 300 includes an optical fiber 310 and a first grating 320 and a second grating 330 arranged on the optical fiber 310. The two connecting members 230 are both connected with the optical fiber 310. The first grating 320 is located between the two connecting members 230. One of the two connecting members 230 is provided with a heat conduction expansion part 231, and the second grating 330 is located on the heat conduction expansion part 231. The sensor base 100 is configured to be deformed when the pressure inlet groove 110 is pressed. The two second supporting members 220 are used to move relative to the first supporting member 210 when the sensor base 100 is deformed, so as to drive the corresponding connecting member 230 to rotate towards the sensor base 100, and reversely move the two connecting members 230.

[0041] Specifically, the sensor base 100 serves as the basis of the entire scissor-type fiber grating temperature and pressure sensor, and is used to be connected to the pressure measuring hole of the oil and gas well to ensure the positioning and stability during the detection process.

[0042] Exemplarily, by opening the pressure inlet groove 110 on the sensor base 100, the pressure inlet groove 110 serves as an opening or passage on the sensor base 100 for external pressure such as liquid or gas to enter, so that the sensor base 100 is deformed; when the well pressure changes, the sensor base 100 is deformed due to pressure and affects the first support 210 arranged thereon, so that the first support 210 is displaced. In specific implementation, the sensor base 100 can include a pressure sensitive member 102 and a base body 101 arranged in sequence, the support assembly 200 is arranged on the pressure sensitive member 102, and the base body 101 is used to connect with the pressure measuring hole. Wherein, the base body 101 can be made of high-strength, corrosion-resistant materials such as stainless steel or titanium alloy to adapt to the oil and gas well environment.

[0043] In order to realize the movement of the second support 220 relative to the first support 210 when the pressure inlet groove 110 is pressed, the pressure sensitive member 102 which is deformed can be adaptively designed in structure according to the arrangement mode of the pressure inlet groove 110 and the first support 210 and the second support 220 connected thereon.

[0044] Specifically, in combination with FIG. 2, the pressure sensitive member 102 and the base body 101 are arranged from top to bottom along the Z direction shown in the figure, the base body 101 is opened with a pressure inlet groove 110 extending to the pressure sensitive member 102, the first support 210 and the second support 220 on the pressure sensitive member 102 are opposite to the pressure inlet groove 110, at this time, the pressure sensitive member 102 in the region of the two second supports 220 can be made of corrosion-resistant, elastic and stress-strain characteristic materials such as elastic diaphragm or carbon fiber, while the pressure sensitive member 102 in the region of the first support 210 is made of materials with small elasticity and large rigidity, in this way, when the liquid or gas in the oil and gas well enters the pressure inlet groove 110 from the slot of the pressure inlet groove 110 and flows upward along the Z direction to impact the pressure sensitive member 102, because the pressure sensitive member 102 has different elastic modulus in different regions, only the pressure sensitive member 102 in the region of the two second supports 220 is deformed, so that the two second supports 220 move upward along the Z direction relative to the first support 210.

[0045] Of course, the number of the pressure inlet grooves 110 formed on the base body 101 can also be two as shown in FIG. 3, wherein the pressure sensitive member 102 and the base body 101 are arranged from top to bottom along the Z direction shown in the figure, and both of the pressure inlet grooves 110 are formed on the base body 101 and the pressure sensitive member 102, that is, the pressure inlet grooves 110 penetrate the base body 101 and further extend to the pressure sensitive member 102, so that part of the structure of the pressure inlet grooves 110 is located on the pressure sensitive member 102. Overall, one of the second supports 220, one of the pressure inlet grooves 110, the first support 210, the other of the pressure inlet grooves 110, and the other of the second supports 220 are arranged from left to right along the X direction shown in the figure.

[0046] It should be noted that the part of the pressure sensitive member 102 located between the two pressure inlet grooves 110, that is, the area opposite to the first support 210, can be made of a material with small elasticity and large rigidity as mentioned above, and the rest of the pressure sensitive member 102 is made of an elastic diaphragm or other materials with good elasticity and stress-strain characteristics and corrosion resistance; or the pressure sensitive member 102 can be a single elastic diaphragm, and the distance between the two pressure inlet grooves 110 is greater than the distance between the pressure inlet grooves 110 and the side walls of the adjacent base body 101. It can be understood that the elastic diaphragm is usually made of a polymer and has good elasticity and stress-strain characteristics. When subjected to pressure, the diaphragm will deform.

[0047] In this way, when the liquid or gas in the oil and gas well enters the pressure inlet grooves 110 through the openings of the pressure inlet grooves 110 and flows upward along the Z direction to impact the pressure sensitive member 102, it can be ensured that the fluid in the left pressure inlet groove 110 will generate a larger impact force on the pressure sensitive member 102 towards the left, and the fluid in the right pressure inlet groove 110 will generate a larger impact force on the pressure sensitive member 102 towards the right. Since the pressure sensitive member 102 at the two positions is prone to deformation, the left second support 220 will move to the left relative to the first support 210 to adapt to the deformation of the left pressure sensitive member 102; similarly, the right second support 220 will move to the right relative to the first support 210 to adapt to the deformation of the right pressure sensitive member 102.

[0048] In a specific implementation, the connecting members 230 are hingedly connected to the second supports 220 one by one, and both of the connecting members 230 are hingedly connected to the first support 210; the first grating 320 and the second grating 330 are arranged on the optical fiber 310, and the heat-conducting expansion part 231 is arranged on one of the two connecting members 230, so that the first grating 320 is located between the two connecting members 230 and the second grating 330 is located on the heat-conducting expansion part 231 by connecting both of the connecting members 230 to the optical fiber 310.

[0049] Overall, when detecting the pressure and temperature of the oil and gas well, the liquid or gas enters the pressure tank 110 to pressurize the pressure tank 110, and the pressure tank 110 is deformed to move the two second supports 220 relative to the first support 210 to drive the corresponding connecting pieces 230 to rotate towards the sensor base 100, and then the two connecting pieces 230 are reversely moved to make the first grating 320 be pulled to realize the detection of the pressure; in addition, the thermal conduction expansion part 231 is affected by the temperature of the oil and gas well, so that the second grating 330 located thereon can realize the detection of the temperature; the scissors-type fiber grating temperature and pressure sensor provided by the application has the advantages of simple structure, can realize temperature and pressure measurement, high integration, good overall stability, and the like; and the overall stability is good, the deformation of the sensor base 100 caused by the pressure is amplified through the scissors-type hinged structure of the support assembly 200, the overall stability is good, and the sensitivity of the pressure measurement is higher.

[0050] Here, as mentioned before, it can be understood that the two second supports 220 move relative to the first support 210 under the action of deformation, that is, the two second supports 220 can move upward relative to the first support 210, or the two second supports 220 can move reversely, that is, move towards the direction away from the first support 210. Overall, since the support assembly 200 forms a movable structure through the hinged mode, the first grating 320 on the fiber 310 can be driven to change the position by the connecting piece 230. In this way, the change of pressure is converted into the change of the grating position of the fiber 310, and then the reflection wavelength of the first grating 320 is changed, realizing the conversion of the pressure signal to the optical signal, and at the same time, the linkage of the mechanical structure ensures the reliability and stability of the conversion process.

[0051] Exemplarily, the first grating 320 of the embodiment of the application is a fiber 310 Bragg grating FBG. For the fiber 310 Bragg grating FBG, there is λ B = 2n eff Λ (1)

[0052] Here λ B is often called the Bragg wavelength, also known as the initial resonance wavelength; n eff is the effective refractive index of the fiber 310 core; and Λ is the period of the uniform fiber 310 grating.

[0053] The FBG sensing technology is to apply the feature that the Bragg wavelength changes with the change of the external environment, and further, when the FBG is affected by the temperature and strain, the wavelength shift is Δλ B =(α+ξ)λ B ΔT+(1-p e )λ Bε (2)

[0054] In the formula, a is the thermal expansion coefficient of the optical fiber 310 material, ξ is the thermo-optic coefficient of the optical fiber 310 material, ΔT is the change in the ambient temperature, P is the effective photoelastic coefficient of the optical fiber 310, and ε is the strain of the optical fiber 310 in the axial direction. e

[0055] When the scissors-type fiber Bragg grating temperature and pressure sensor is placed in a high-temperature and high-pressure environment, liquid or gas enters the pressure tank 110, and the sensor base 100 is deformed, as previously described, the first grating 320 is stretched, and the center wavelength increases.

[0056] The ambient temperature also affects the first grating 320, if the temperature increases, the wavelength of the first grating 320 also increases, if the temperature decreases, the wavelength of the first grating 320 also decreases. Finally, the wavelength of the first grating 320 is the result of the combined action of pressure and temperature. The wavelength change can be represented as Δλ 11 = [(ξ + a) + (1 - P eff )ε T ]·ΔT·λ 11 +(1-P eff )ε P ·λ 11 (3)

[0057] In the formula, λ 11 is the Bragg wavelength of the first grating 320, ε T is the strain of the first grating 320 caused by the thermal expansion of the sensor structure, and ε P is the strain of the first grating 320 caused by pressure.

[0058] Since the second grating 330 is located at both ends of the heat-conducting expansion part 231, it is not affected by the strain caused by the change in pressure, but only by the ambient temperature, and has good monotonicity. The heat-conducting expansion part 231 can be made of a metal material with good heat conduction performance and has the characteristics of thermal expansion and contraction. When the ambient temperature rises, the volume of the heat-conducting expansion part 231 will expand, pulling the second grating 330 located on it to stretch, at this time, the period Λ of the second grating 330 becomes larger, and the center wavelength increases. The ambient temperature and the stretching amount of the second grating 330 correspond to each other, and have a good monotonic relationship. The wavelength change can be represented as Δλ 12 =(ξ + a)λ 12 ΔT (4)

[0059] In the formula, λ 12 is the Bragg wavelength of the second grating 330.​

[0060] In this way, the change amount ΔT of the ambient temperature can be accurately measured through the wavelength change of the second grating 330. Then, ΔT is substituted into equation (3), so that the influence of the ambient temperature on the first grating 320 is eliminated, and only the influence of the pressure on the first grating 320 is left, thereby realizing the pressure measurement by using the correspondence between the wavelength of the first grating 320 and the pressure.

[0061] In a specific implementation, the circumferential edge of the sensor base 100 can be provided with a sealing structure to ensure that no leakage occurs in the high-pressure environment under the oil and gas well.

[0062] In addition, the circumferential side of the sensor base 100 is provided with a connecting interface, such as a threaded interface 120 or a flange, which matches the pressure measuring hole of the oil and gas well, so as to facilitate the installation and disassembly of the scissors-type fiber grating temperature and pressure sensor.

[0063] Referring to FIGS. 1 and 4, in some embodiments, the sensor base 100 is in a cylindrical shape, the axis of the first support 210 coincides with the axis of the sensor base 100, and the two second supports 220 are symmetrically arranged on opposite sides of the first support 210, and the second supports 220 correspond one-to-one to the pressure inlet grooves 110.

[0064] Specifically, the cylindrical sensor base 100 and the symmetrical arrangement of the second supports 220 can ensure balanced stress of the sensor base 100 when under pressure, reduce the risk of local overload, and facilitate to improve the accuracy and repeatability of the measurement; in addition, the sensor base 100 and the pressure measuring hole of the oil and gas well can be connected, and the stability and reliability of the overall structure can be improved.

[0065] By setting the axis of the first support 210 to coincide with the axis of the base, and making the second supports 220 correspond one-to-one to the pressure inlet grooves 110, the pressure change can be accurately converted into the displacement of the second supports 220, so that the pressure change can be more efficiently converted into the position change of the first grating 320. Overall, the mechanical linkage structure formed by the support assembly 200 and the response characteristics of the measurement assembly are optimized, and the measurement accuracy and dynamic performance are improved.

[0066] Here, as mentioned above, the sensor base 100 comprises the pressure sensitive member 102 and the base body 101 arranged in sequence, through the above arrangement, the pressure sensitive member 102 can be arranged as a single elastic diaphragm, so as to optimize the structure of the sensor base 100, so that the structure of the sensor base 100 is more simple. Exemplarily, in combination with FIG. 4, when the liquid or gas in the oil and gas well enters the pressure inlet groove 110 through the slot of the pressure inlet groove 110 and flows upward along the Z direction to impact the pressure sensitive member 102, due to the one-to-one correspondence between the second support 220 on the pressure sensitive member 102 and the pressure inlet groove 110, the two second supports 220 can be directly affected by the deformation of the pressure sensitive member 102 due to pressure, so as to move relative to the first support 210 in the direction away from the sensor base 100 under the action of the impact force, thereby causing the corresponding hinged connecting member 230 to rotate towards the sensor base 100, and the reverse movement of the two connecting members 230 will cause the first grating 320 to be pulled, realizing the detection of pressure.

[0067] Referring to FIG. 4, in some examples, the distance between the groove wall of the pressure inlet groove 110 and the adjacent side wall of the sensor base 100 is greater than or equal to the distance between the groove bottom of the pressure inlet groove 110 and the side of the sensor base 100 away from the slot of the pressure inlet groove 110; wherein the distance between the groove bottom of the pressure inlet groove 110 and the side of the sensor base 100 away from the slot of the pressure inlet groove 110 is 1mm-3mm.

[0068] In this way, during the process that the liquid or gas in the oil and gas well flows into the pressure inlet groove 110 through the slot of the pressure inlet groove 110, it can be ensured that the pressure generated by the liquid or gas can be effectively transmitted from the slot to the groove bottom, reducing the loss in the process of pressure transmission.

[0069] It can be understood that, since the second support 220 is one-to-one corresponding to the pressure inlet groove 110, when the groove bottom of the pressure inlet groove 110 is deformed after being pressed, it will push the corresponding second support 220 to move, by reflecting the pressure signal more completely on the deformation of the groove bottom of the pressure inlet groove 110, the response speed and signal fidelity of the scissors-type fiber grating temperature and pressure sensor are enhanced.

[0070] The distance between the groove bottom of the pressure inlet groove 110 and the side of the sensor base 100 away from the slot of the pressure inlet groove 110 is 1mm-3mm, so as to balance the stability of the structure and the sensitivity of pressure sensing, and ensure that the sensor can still maintain good response characteristics when bearing high pressure.

[0071] Exemplarily, when implemented, the distance can be set to 3mm. By setting in this way, while ensuring the sensitivity of pressure sensing, the rigidity of the structure of the pressure inlet groove 110 can be ensured to prevent structural failure caused by excessive deformation, which is conducive to providing the structural stability and durability of the sensor base 100, and prolonging the service life of the sensor.

[0072] It should be noted that by designing the distance between the bottom of the pressure inlet groove 110 and the side of the sensor base 100 away from the groove opening of the pressure inlet groove 110, the linear relationship between deformation and pressure can be ensured, and the accurate measurement of pressure and temperature can be facilitated.

[0073] Referring to FIGS. 1-4, in a specific example, the length of the second support 220 along the axial direction of the sensor base 100 is less than the length of the first support 210 along the axial direction of the sensor base 100.

[0074] In this way, after the connection piece 230 and the second support 220 are hingedly connected one by one, and each connection piece 230 is hingedly connected to the first support 210, the two connection pieces 230 can cross to form an X-shaped structure, facilitating the rotation of the connection piece 230 towards the sensor base 100, making the action of the connection piece 230 more smooth, and overall ensuring that the support assembly 200 is configured as a scissors-type hinged structure.

[0075] In specific implementation, the first support 210 and the second support 220 can each be configured as a rod-shaped structure as shown in FIG. 1, wherein the first support 210 and the second support 220 can each be configured as a column or a rod with a square cross section, as long as the structure of the first support 210 and the second support 220 is regular to facilitate manufacturing and processing, which is not limited in the present application.

[0076] Referring to FIGS. 4 and 5, in some embodiments, the connection piece 230 includes a connection portion 232, which is hingedly connected to the end of the corresponding second support 220 away from the sensor base 100 and the end of the first support 210 away from the sensor base 100 in sequence; the connection portion 232 has a connection surface 233, the optical fiber 310 is connected to the connection surface 233, a heat-conducting expansion portion 231 is connected to the connection portion 232, and the side of the heat-conducting expansion portion 231 away from the sensor base 100 is flush with the connection surface 233.

[0077] Specifically, by hingedly connecting the connection portion 232 to the end of the corresponding second support 220 away from the sensor base 100 and the end of the first support 210 away from the sensor base 100 in sequence, the displacement of the second support 220 relative to the first support 210 can be smoothly transmitted to the connection portion 232, causing the two connection portions 232 to move in opposite directions, ensuring that the change in pressure can be accurately converted into a change in the position of the first grating 320, and improving the sensitivity and measurement accuracy of detection.

[0078] The connecting surface 233 is used to provide a connecting point and support for the optical fiber 310. By connecting the optical fiber 310 with the connecting surface 233, the optical fiber 310 can be bonded on the two connecting surfaces 233 in specific implementation, so as to ensure that the optical fiber 310 can be stably fixed on the connecting piece 230, and avoid unnecessary movement or vibration of the optical fiber 310. In this way, the noise in the signal transmission process can be reduced, and the stability of detection can be improved.

[0079] By setting the side of the heat-conducting expansion part 231 away from the sensor base 100 flush with the connecting surface 233, when the optical fiber 310 is bonded on the connecting surface 233, the second optical grating 330 can be in direct contact with the heat-conducting expansion part 231. In this way, when the heat-conducting expansion part 231 expands in volume due to temperature rise, the second optical grating 330 can be timely pulled to stretch, which is beneficial to improve the response speed and accuracy of temperature measurement, and ensure the performance stability of the sensor in a temperature changing environment.

[0080] It should be noted that, in specific implementation, as shown in FIG. 5, one of the two connecting pieces 230 is provided with the heat-conducting expansion part 231, and the second optical fiber 310 is correspondingly arranged on the heat-conducting expansion part 231. The heat-conducting expansion part 231 is arranged on the right side of the connecting part 232 along the X direction shown in the drawing, and the included angle between them is an acute angle. Of course, the heat-conducting expansion part 231 can also be arranged on the left side of the connecting part 232 along the X direction shown in the drawing, and the included angle between them is an obtuse angle. In addition, in order to make the scissors-type fiber grating temperature and pressure sensor have better structural symmetry, as shown in FIG. 4, the two connecting pieces 230 can be provided with heat-conducting expansion parts 231, and the two heat-conducting expansion parts 231 are oppositely arranged. At this time, the second optical grating 330 can be located on one of the two heat-conducting expansion parts 231.

[0081] Referring to FIGS. 1, 6 and 7, in some embodiments, the scissors-type fiber grating temperature and pressure sensor further comprises a first hinged piece 400. The first support piece 210 is provided with a first plug-in slot 211, and part of the connecting part 232 is inserted into the first plug-in slot 211. The connecting part 232 is provided with a sliding hole 2325, and the slot wall of the first plug-in slot 211 is provided with two first insertion holes 212 which are in communication with the first plug-in slot 211. The first hinged piece 400 passes through one of the two first insertion holes 212, the sliding hole 2325 and the other of the two first insertion holes 212 in sequence, so as to hinge the connecting part 232 with the first support piece 210.

[0082] In this way, the connection part 232 can be quickly assembled or disassembled with the first support 210 without using complex tools, which is conducive to reducing production and maintenance costs. By providing the first insertion slot 211 on the first support 210, inserting part of the connection part 232 into the first insertion slot 211, and precisely connecting the connection part 232 and the first support 210 through the first hinge 400, the structural strength between the connection part 232 and the first support 210 is enhanced.

[0083] By providing the sliding hole 2325 on the connection part 232, the connection part 232 has a certain displacement range in the first insertion slot 211, which ensures that the connection part 232 can adapt to the deformation degree of the sensor base 100 under different pressures, i.e., the displacement range can adapt to the deformation under different pressures, thereby facilitating the matching of the motion trajectory of the connection part 232 and the deformation of the sensor base 100, and improving the response speed and measurement accuracy of the sensor.

[0084] In a specific implementation, the first hinge 400 can be a pin, which includes a contact part 410 and a hinge part 420 arranged in sequence. The contact part 410 and the hinge part 420 are both cylindrical, the diameter of the contact part 410 is greater than the diameter of the hinge part 420 and the first insertion hole 212, and the diameter of the hinge part 420 is less than the diameter of the first insertion hole 212. The hinge part 420 is sequentially fitted into one of the two first insertion holes 212, the sliding hole 2325, and the other of the two first insertion holes 212, and the contact part 410 is in contact with the first support 210, thereby completing the connection between the connection part 230 and the first support 210.

[0085] Referring to FIGS. 1, 4, and 8, in some embodiments, the scissors-type fiber grating temperature and pressure sensor further includes two second hinges 500, the second hinge 500 corresponds to the connection part 232 one by one, the second support 220 is provided with a second insertion slot 221, and part of the connection part 232 is inserted into the second insertion slot 221. A connection hole 2326 is provided on the connection part 232, a slot wall of the second insertion slot 221 is provided with two second insertion holes 222 connected with the second insertion slot 221, and the second hinge 500 sequentially passes through one of the two second insertion holes 222, the connection hole 2326, and the other of the two second insertion holes 222, so as to connect the connection part 232 and the second support 220.

[0086] In this way, the connection part 232 can be quickly assembled or disassembled with the second support 220 without using complex tools, which is conducive to reducing production and maintenance costs.

[0087] In a specific implementation, the second hinge 500 can be a pin as in the foregoing embodiments, where the diameter of the second insertion hole 222 and the diameter of the connecting hole 2326 are equal, the diameter of the contact portion 410 of the pin is greater than the diameter of the hinge portion 420 of the pin and the diameter of the connecting hole 2326, and the diameter of the hinge portion 420 is less than the diameter of the connecting hole 2326; the hinge portion 420 is sequentially fitted into one of the two second insertion holes 222, the connecting hole 2326, and the other of the two second insertion holes 222, and the contact portion 410 is in contact with the second support 220, so that the connecting member 230 is hinged to the second support 220.

[0088] Referring to FIG. 9, in some examples, the connecting portion 232 includes a first insertion segment 2321, a first support segment 2322, a second insertion segment 2323, and a second support segment 2324 connected in sequence; the connecting hole 2326 is located on the first insertion segment 2321, the sliding hole 2325 is located on the second insertion segment 2323, and the second support segment 2324 has a connecting surface 233; the distance between the center of the connecting hole 2326 and the center of the sliding hole 2325 is less than the distance between the center of the sliding hole 2325 and the connecting surface 233.

[0089] In this way, the reverse movement of the two connecting members 230 can amplify the deformation of the sensor base 100 caused by the pressure, so that the sensitivity and resolution of the pressure measurement are more accurate.

[0090] It can be understood that, on the basis of ensuring that the distance between the center of the connecting hole 2326 and the center of the sliding hole 2325 is less than the distance between the center of the sliding hole 2325 and the connecting surface 233, the positions and angles of the hinge points can be optimized and adjusted to further improve the conversion effect from mechanical displacement to change in the grating position of the optical fiber 310, reduce signal distortion, and improve the response speed and measurement accuracy of the scissors-type fiber Bragg grating temperature and pressure sensor.

[0091] In a specific implementation, the thickness of the first insertion segment 2321 is less than the thickness of the first support segment 2322, and the thickness of the second insertion segment 2323 is less than the thickness of the first insertion segment 2321, so that the sizes of the first insertion slot 211 and the second insertion slot 221 can be optimized, and the structure of the first support 210 and the second support hinged to the connecting member 230 is compact; at the same time, the connecting portion 232 can have good structural strength, and the connection stability of the connecting portion 232 and the first support 210 and the connection stability of the connecting portion 232 and the second support 220 can be ensured.

[0092] In a specific example, the optical fiber 310 is a single-mode optical fiber, and the single-mode optical fiber has a polyimide coating layer.

[0093] Thus, the single-mode optical fiber has low loss and high bandwidth characteristics, and can support high-precision grating reflection wavelength measurement, making the scissors-type fiber grating temperature and pressure sensor more accurate in temperature and pressure measurement.

[0094] The low attenuation characteristics of the single-mode optical fiber are beneficial to maintaining good signal quality during long-distance transmission, so it can be applied to deep well areas or remote monitoring occasions of oil and gas wells without the need for relay amplification, reducing the complexity and cost of detection.

[0095] By providing a polyimide coating layer on the single-mode optical fiber, the polyimide coating layer has excellent chemical stability and corrosion resistance. It can protect the single-mode optical fiber from being eroded by acidic and alkaline fluids in the oil and gas well, prolonging the service life of the single-mode optical fiber and the sensor; during use, the polyimide coating layer can enhance the adaptability of the single-mode optical fiber to environmental changes, so that the scissors-type fiber grating temperature and pressure sensor can work in a wider temperature and pressure range, expanding its application range.

[0096] In addition, polyimide has good thermal stability and can maintain structural integrity at high temperatures, ensuring stable performance of the single-mode optical fiber in high-temperature oil and gas wells and avoiding measurement errors caused by temperature changes.

[0097] Further, the coating layer provides additional mechanical strength to the single-mode optical fiber, protecting it from physical damage and reducing the risk of failure due to accidental impact or wear, improving the durability and reliability of the scissors-type fiber grating temperature and pressure sensor.

[0098] In specific implementation, the first grating 320 and the second grating 330 provided on the optical fiber 310 can be directly written on the optical fiber 310 without stripping the polyimide coating layer by a femtosecond laser. In this way, the first grating 320 and the second grating 330 are written by a femtosecond laser on the single-mode optical fiber without stripping the polyimide coating layer to ensure that the first grating 320 and the second grating 330 have strong tensile strength. The femtosecond laser has extremely high pulse energy density and extremely short pulse width, and can achieve high-precision grating writing.

[0099] In some embodiments, the grating length of the first grating 320 is 1mm-5mm, and the grating length of the second grating 330 is equal to the grating length of the first grating 320; the difference between the center wavelength of the first grating 320 and the center wavelength of the second grating 330 is ≥3nm.

[0100] Specifically, the choice of grating length affects the resolution and signal-to-noise ratio of the grating, and a longer grating length can provide higher measurement accuracy.

[0101] Exemplarily, the grating region length of the first grating 320 is 1mm-5mm, for example, the grating region length of the first grating 320 can be set to 1mm, so that the resolution of the first grating 320 is ensured, and good signal quality and strong reflection intensity are maintained, and the measurement accuracy of the pressure is improved.

[0102] The grating length is related to the sensitivity and bandwidth of the sensor, and appropriate length can balance the two. The grating region length is selected in the range of 1mm-5mm, which ensures high sensitivity to temperature and pressure changes, and avoids too narrow bandwidth limitation, so that the sensor can cope with rapidly changing environment.

[0103] The grating region length is set in the range of 1mm-5mm, which is beneficial to guarantee the economy and feasibility of manufacturing, and avoid the cost increase or performance degradation caused by too long or too short grating region.

[0104] By setting the center wavelength difference between the first grating 320 and the second grating 330, the independent demodulation of temperature and pressure signals is ensured, and the accuracy and reliability of measurement are improved.

[0105] In specific implementation, the center wavelength difference between the two is at least 3nm, so that the cross interference of the reflection signals of the two in demodulation can be avoided, which is helpful to maintain the stability of temperature and pressure measurement, reduce the influence between them, and ensure the reliability of long-term measurement; at the same time, the signal demodulation algorithm can be simplified, the difficulty of data processing is reduced, and the practicability and response speed of the sensor are improved.

[0106] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A shear type fiber grating temperature and pressure sensor, characterized by, The sensor base (100), the support assembly (200) and the detection assembly (300) are included. The sensor base (100) is used for connecting with a pressure measuring hole of an oil and gas well, and an inlet pressure groove (110) is formed in the sensor base (100). The support assembly (200) includes a first support (210), two second supports (220) and two connecting pieces (230). The first support (210) and the two second supports (220) are arranged on the sensor base (100), and the first support (210) is located between the two second supports (220). The connecting pieces (230) and the second supports (220) are hingedly connected one by one, and the two connecting pieces (230) are hingedly connected with the first support (210). The detection assembly (300) includes an optical fiber (310), a first grating (320) and a second grating (330) arranged on the optical fiber (310). The two connecting pieces (230) are connected with the optical fiber (310), the first grating (320) is located between the two connecting pieces (230), and one of the two connecting pieces (230) is provided with a heat-conducting expansion part (231). The second grating (330) is located on the heat-conducting expansion part (231). The sensor base (100) is configured to deform when subjected to pressure in the inlet pressure groove (110). When the sensor base (100) deforms, the two second supports (220) move relative to the first support (210) to drive the corresponding connecting pieces (230) to rotate towards the sensor base (100), so that the two connecting pieces (230) move in opposite directions.

2. The FBG temperature and pressure sensor according to claim 1, wherein, The sensor base (100) is in a cylindrical shape, the axis of the first support (210) coincides with the axis of the sensor base (100), and the two second supports (220) are symmetrically arranged on opposite sides of the first support (210). The second support (220) corresponds to the inlet pressure groove (110) one by one.

3. The FBG temperature and pressure sensor according to claim 2, wherein, The distance between the groove wall of the inlet pressure groove (110) and the adjacent side wall of the sensor base (100) is greater than or equal to the distance between the groove bottom of the inlet pressure groove (110) and the side of the sensor base (100) away from the groove opening of the inlet pressure groove (110). The distance between the groove bottom of the inlet pressure groove (110) and the side of the sensor base (100) away from the groove opening of the inlet pressure groove (110) is 1mm-3mm.

4. The FBG temperature and pressure sensor according to any one of claims 1 to 3, wherein, The length of the second support (220) along the axis of the sensor base (100) is less than the length of the first support (210) along the axis of the sensor base (100).

5. The FBG temperature and pressure sensor according to claim 4, wherein, The connecting piece (230) comprises a connecting part (232) which is hingedly connected with the end of the corresponding second support piece (220) away from the sensor base (100) and the end of the first support piece (210) away from the sensor base (100) in sequence; The connecting part (232) is provided with a connecting surface (233), the optical fiber (310) is connected with the connecting surface (233), the heat-conducting expansion part (231) is connected with the connecting part (232), and the side of the heat-conducting expansion part (231) away from the sensor base (100) is flush with the connecting surface (233).

6. The FBG temperature-pressure sensor according to claim 5, wherein, A first hinge piece (400) is further included, the first support piece (210) is provided with a first plug-in slot (211), and part of the connecting part (232) is inserted into the first plug-in slot (211); The connecting part (232) is provided with a sliding hole (2325), the slot wall of the first plug-in slot (211) is provided with two first plug-in holes (212) which are in communication with the first plug-in slot (211), and the first hinge piece (400) passes through one of the two first plug-in holes (212), the sliding hole (2325) and the other of the two first plug-in holes (212) in sequence, so that the connecting part (232) is hingedly connected with the first support piece (210).

7. The FBG temperature-pressure sensor according to claim 6, wherein, Two second hinge pieces (500) are further included, the second hinge pieces (500) correspond to the connecting parts (232) in one-to-one manner, the second support piece (220) is provided with a second plug-in slot (221), and part of the connecting part (232) is inserted into the second plug-in slot (221); The connecting part (232) is provided with a connecting hole (2326), the slot wall of the second plug-in slot (221) is provided with two second plug-in holes (222) which are in communication with the second plug-in slot (221), and the second hinge piece (500) passes through one of the two second plug-in holes (222), the connecting hole (2326) and the other of the two second plug-in holes (222) in sequence, so that the connecting part (232) is hingedly connected with the second support piece (220).

8. The FBG temperature-pressure sensor according to claim 7, wherein, The connecting part (232) comprises a first plug-in section (2321), a first support section (2322), a second plug-in section (2323) and a second support section (2324) which are connected in sequence; the connecting hole (2326) is located on the first plug-in section (2321), the sliding hole (2325) is located on the second plug-in section (2323), and the second support section (2324) is provided with the connecting surface (233); The distance between the center of the connecting hole (2326) and the center of the sliding hole (2325) is smaller than the distance between the center of the sliding hole (2325) and the connecting surface (233).

9. The FBG temperature and pressure sensor according to any one of claims 1 to 3, wherein, The optical fiber (310) is a single-mode optical fiber having a polyimide coating layer, and the first grating (320) and the second grating (330) are inscribed by a femtosecond laser under the condition that the single-mode optical fiber does not strip the polyimide coating layer.

10. The FBG temperature and pressure sensor according to any one of claims 1 to 3, wherein, The grating region length of the first grating (320) is 1mm-5mm, and the grating region length of the second grating (330) is equal to the grating region length of the first grating (320). The difference between the center wavelength of the first grating (320) and the center wavelength of the second grating (330) is greater than or equal to 3nm.

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