Three-dimensional vibration fiber Bragg grating sensor for logging while drilling engineering parameter sub

Abstract

The present invention proposes a three-dimensional vibration fiber grating sensor for a while-drilling logging engineering parameter pup joint, which belongs to the technical field of fiber grating sensors; it comprises a hollow shell, and the two ends of the shell extending along a first preset direction are respectively provided with a fiber input port and a fiber output port, the first preset direction is the length extension direction of the shell, and the shell is fixedly connected to the engineering parameter pup joint; three support components are sequentially arranged in the shell along the first preset direction, and the three support components are all provided with a through embedding groove, and the normal directions of the end faces of the three support components with the embedding grooves are different from each other; a bend-insensitive optical fiber is inserted into the shell and passes through the fiber input port, the embedding grooves on the three support components and the fiber output port in sequence, and the parts of the bend-insensitive optical fiber passing through the three support components are all provided with a grid area; wherein the grid area and the support component in which it is located together constitute a sensing body, and the sensing body is used to obtain vibration signals of different axes during the process of while-drilling logging.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber Bragg grating sensors, and in particular to a three-dimensional vibration optical fiber Bragg grating sensor for a logging while drilling engineering parameter pup joint. Background Art

[0002] Fiber-optic communication while drilling (FOD) is an advanced communications technology used in the oil and gas industry. This technology is based on fiber-optic communications. Due to its high frequency, fiber-optic communications boast greater capacity and wider bandwidth than conventional cable communications, making it suitable for high-speed, broadband information transmission. Fiber-optic communication also exhibits minimal loss, significantly increasing the distance of unrelayed transmission. Fiber-optic communication transmits optical signals, which radiate virtually no light, resulting in superior confidentiality. It also eliminates crosstalk between fibers within the same cable, is immune to electromagnetic interference, and avoids sparks that could pose a safety hazard to oil wells. It also offers excellent explosion-proof properties. Glass fiber is made from quartz, a more abundant material than copper and aluminum used in cables. Fiber-optic communication is also environmentally friendly and has a long service life.

[0003] In downhole measurement-while-drilling (MWD) systems, accurate measurement of three-dimensional vibration parameters near the drill bit is crucial for safe and efficient drilling. However, existing MWD technologies utilize electrical sensors, which are expensive to implement in the harsh downhole environment of high temperature, high pressure, and strong electromagnetic interference. Furthermore, the use of downhole electrical sensors in fiber-optic MWD systems requires the design of additional photoelectric conversion modules, increasing the risk of operational safety. Fiber Bragg grating (FBG) sensing technology, with its advantages of high temperature, high pressure resistance, and electromagnetic interference immunity, has gained widespread application in petroleum engineering monitoring. FBG sensors can be directly connected to MWD systems, efficiently transmitting collected physical quantity information via optical signals. In the application of downhole fiber-optic MWD systems, significant basic optical transmission loss is present, primarily due to two reasons. First, MWD systems require multiple fiber optic connectors to form a complete link. These connectors include downhole wet-joints, wellhead wet-joints, and optical slip rings. The integration of these connectors can alleviate the difficulty of optical cable installation, simplifying the process and improving construction efficiency. However, the use of these connectors increases the basic optical transmission loss of the fiber-optic measurement while drilling (MWD) system. Furthermore, the harsh downhole operating environment of high temperature and high pressure accelerates the aging and deformation of the seals, leading to the intrusion of moisture and contaminants, creating the risk of a secondary increase in the optical transmission loss of the MWD fiber-optic communication system. Secondly, since the fiber-optic cable must be continuously released during the MWD process, the main and trunk cable silos require storage of a certain length of optical cable. Within the silos, the optical cable is spirally wound around the rods. The macrobending loss caused by this spiral winding method further increases the basic loss of the MWD system. Furthermore, to meet the requirements of high-temperature and high-pressure engineering operations, the design of the downhole drill pipe engineering parameter stub must ensure maximum durability. Therefore, the sensor mounting area within the engineering parameter stub is typically small and flat. In summary, designing a low-loss fiber Bragg grating (FBG) 3D vibration sensor within a confined space is a major challenge in its application in downhole MWD fiber-optic measurement.

[0004] Therefore, it is very necessary to provide a three-dimensional vibration fiber Bragg grating sensor for a short section of logging while drilling engineering parameters, which adopts a linear separation arrangement, places the three-dimensional sensing units on the same straight line, and uses the vibrations in three axial directions on a single-mode optical fiber to achieve while-drilling output with a compact structure. Summary of the Invention

[0005] In view of this, the present invention proposes a three-dimensional vibration fiber Bragg grating sensor for a logging engineering parameter short section with a compact structure, which can be used to measure three axial vibration accelerations respectively and is suitable for the logging engineering parameter short section application scenario.

[0006] The present invention provides a three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter short section, comprising:

[0007] A hollow shell, with a fiber inlet port and a fiber outlet port provided at both ends of the shell extending along a first preset direction, wherein the first preset direction is the length extension direction of the shell, and the shell is fixedly connected to the engineering parameter short section;

[0008] Three support assemblies are sequentially arranged in the housing at intervals along the first pre-examination direction. The three support assemblies are all provided with through embedding grooves. The normal directions of the end surfaces of the three support assemblies on which the embedding grooves are provided are different from each other.

[0009] The bend-insensitive optical fiber is passed through the housing and sequentially passes through the fiber inlet port, the embedded grooves on the three support components, and the fiber outlet port. The portions of the bend-insensitive optical fiber passing through the three support components are all provided with grid areas.

[0010] The grid area and the supporting assembly together constitute a sensor body, which is used to obtain vibration signals in different axial directions during the logging while drilling process.

[0011] On the basis of the above technical scheme, preferably, the three supporting components all include a fixed seat, a cantilever beam and a mass block, the fixed seat is fixedly connected to the inner surface of the shell, the mass block and the fixed seat are spaced apart, and the embedding groove runs through the mass block and the fixed seat of the same supporting component, the end faces of the mass block and the fixed seat with the embedding groove are flush, the cantilever beam is arranged between the mass block and the fixed seat, and is respectively fixedly connected to the adjacent end faces of the mass block and the fixed seat; the bend-insensitive optical fiber is respectively fixedly connected to the embedding grooves on the mass block and the fixed seat; the grating area of ​​the bend-insensitive optical fiber is tensioned and suspended between the mass block and the fixed seat, and is set with a gap from the cantilever beam; the mass block and the cantilever beam are set with a gap from the inner surface of the shell.

[0012] Preferably, the thickness of the cantilever beam along the radial direction of the bend-insensitive optical fiber is smaller than the thickness of the fixing seat or the mass block along the radial direction of the bend-insensitive optical fiber, and the mass of the cantilever beam is smaller than the mass of the mass block.

[0013] Further preferably, when the vibration signal of external drilling acts on the three sensor bodies, under the action of inertia, the end of the cantilever beam away from the fixed seat is axially offset from the mass block, compressing or stretching the grid area on the three sensor bodies, causing the central wavelength of the reflected light of the grid area to change, and the vibration signal of the external drilling is obtained by demodulating the signal of the reflected light of the grid area; the axial offset of the mass block is the rotation of the end face of the fixing seat of the sensor body where it is located.

[0014] More preferably, the surface of the bend-insensitive optical fiber is bonded to the inner surface of the embedding groove, or a metal coating is provided on the surface of the bend-insensitive sensor body, and the metal coating is welded and fixed to the inner surface of the embedding groove; the depth of the embedding groove is greater than the diameter of the bend-insensitive optical fiber, and the width of the embedding groove is equal to the diameter of the bend-insensitive optical fiber.

[0015] More preferably, let the length of the cantilever beam be L, the cross-sectional area of ​​the cantilever beam be A=wh, w is the current width of the cantilever beam, h is the current thickness of the cantilever beam, w0 is the initial width of the cantilever beam, h0 is the initial thickness of the cantilever beam, the distance between the center of the mass block and the end of the fixed seat close to the cantilever beam is L2, the length of the mass block along the axial direction of the bend-insensitive optical fiber is d, the thickness of the mass block along the radial direction of the bend-insensitive optical fiber is e, the total mass of the mass block and the cantilever beam is M, E is the elastic modulus of the cantilever beam, and I is the section moment of inertia of the cantilever beam; introducing the influence of temperature T and pressure P on material parameters and geometric dimensions, the corrected elastic modulus is E(T, P)=E0(1+βΔT)(1+γP), where E0 is the initial value of the elastic modulus, β is the temperature coefficient of the elastic modulus, γ is the pressure coefficient of the elastic modulus, ΔT is the temperature change, and P is the current pressure; the corrected cantilever beam length L(T, p)=L0(1+α T ΔT)(1-δP), L0 is the initial length of the cantilever beam, α T is the thermal expansion coefficient of the cantilever beam, δ is the compression coefficient of the cantilever beam; the distance between the center of the corrected mass block and the end of the fixed seat close to the cantilever beam is L2(T, P) = L 20 (1+α T ΔT)(1-δP), L 20 is the initial length from the center of the mass block to the nearest end of the fixed seat; the corrected section inertia moment is I(T, P) = I0(1+α T ΔT-δ w P)(1+α T ΔT-δ h P) 3 , δ w is the width compression coefficient, δ h is the height compression coefficient; the thickness of the corrected mass block along the radial direction of the bend-insensitive optical fiber is e(T, P)=e0(1+α e ΔT)(1-δ e P), e0 is the initial height of the mass block, α e is the thermal expansion coefficient of the mass block, δ e is the compression coefficient of the mass block; the corrected grating reflection wavelength λ B (T, P) = λ B0 [1+(α λ +ξΔT)+(1-P e )F P],λ B0 is the initial center wavelength of the grating region, α λ is the thermal expansion coefficient of optical fiber, ξ is the thermal-optical coefficient of optical fiber, P e is the elastic-optical coefficient, F P is the axial strain of the optical fiber caused by pressure; it satisfies the following relationship: the first axial sensitivity is The second axial sensitivity is The third axial sensitivity is Among them I x (T, P) = I x0 (1+α T ΔT-δ w P)(1+α T ΔT-δ h P) 3 , is the first initial moment of inertia, I y (T, P) = I y0 (1+α T ΔT-δ w P)(1+α T ΔT-δh P ) 3 , is the second initial moment of inertia.

[0016] More preferably, the measurement wavelength ranges of different grating regions do not overlap with each other.

[0017] Preferably, it also includes several mounting blocks, the inner surface of the shell is provided with several placement grooves, and the several placement grooves are arranged at intervals along the first preset direction; one end of the mounting block is embedded in the placement groove, and the other end extends out of the placement groove and extends toward the inside of the shell; the fixing seat is provided at the end of the several mounting blocks away from the inner surface of the shell, and is fixedly connected to the mounting block.

[0018] Further preferably, the spacing between different fixing seats is greater than the spacing between corresponding mounting blocks.

[0019] On the basis of the above technical solution, preferably, a cover plate is further included, an opening is provided on the shell, and the cover plate is provided at the opening.

[0020] The present invention provides a three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter sub, which has the following advantages over the prior art:

[0021] (1) The present invention is to set a separate bend-insensitive optical fiber inside a compact housing, set three gratings on the optical fiber, and combine three supporting components to form three different sensing bodies, thereby measuring the three axial vibration signals of the engineering parameter short section, reducing the bending loss of the sensor and improving the reliability and transmission quality of the sensor measurement results;

[0022] (2) The supporting components include a fixed base, a cantilevered mass block, and a cantilever beam connecting the fixed base and the mass block. Under the influence of axial acceleration, the mass block will undergo a certain axial deformation relative to the fixed base, thereby causing the grid area to be compressed or stretched, resulting in the center wavelength of the emitted light in the grid area to drift. By demodulating the optical signal, the change in the center wavelength and the actual size of the current cantilever beam can be obtained, and the rotation angle of the cantilever beam can be obtained by reverse calculation;

[0023] (3) When calculating the axial sensitivity, the influence of the temperature and pressure of the working environment of the engineering parameter short section is taken into account, so that the sensitivity of each axis is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is a front view of a three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter short sub according to the present invention, with the cover hidden;

[0026] Figure 2 This is a stereoscopic diagram of a three-dimensional vibration fiber Bragg grating sensor for a parameter sub for logging while drilling engineering according to the present invention, with the cover plate and the bend-insensitive optical fiber hidden;

[0027] Figure 3 This is a stereoscopic diagram of the explosion state of a three-dimensional vibration fiber Bragg grating sensor for a parameter short section of a logging while drilling engineering according to the present invention, with the cover plate and the bend-insensitive optical fiber hidden;

[0028] Figure 4 This is a front view of the matching state of the mounting block of a three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter short sub and the placement groove of the housing of the present invention;

[0029] Figure 5 This is a front view of a three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter sub with the mounting block removed;

[0030] Figure 6 This is a top view of a support assembly of a three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter sub in accordance with the present invention;

[0031] Figure 7 This is a front view of a support assembly of a three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter pup joint according to the present invention;

[0032] Figure 8 The present invention is a schematic diagram of the relative positions of a bending-insensitive optical fiber, three supporting components and a housing before assembly of a three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter pup joint.

[0033] Figure numerals: 1. Shell; 2. First support assembly; 3. Bend-insensitive optical fiber; 4. Second support assembly; 5. Third support assembly; 6. Mounting block; 7. Fiber outlet port; 100. Embedded groove; 200. Grid area; 300. Fixed seat; 400. Cantilever beam; 500. Mass block. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] Designing a low-loss fiber Bragg grating three-dimensional vibration sensor in a confined space is a major difficulty in its application in downhole fiber-optic measurement while drilling. Conventional fiber winding methods and multi-fiber connector connection methods will cause macrobending loss and transmission loss. In view of this, combined with Figure 1 、 Figure 2 and Figure 3 It can be seen that the present invention provides a three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter short section, comprising:

[0036] The hollow shell 1 is provided with a fiber inlet port and a fiber outlet port 7 at both ends of the shell 1 extending along a first preset direction. The first preset direction is the length extension direction of the shell 1, that is, Figure 1 The horizontal extension direction is shown; the housing 1 is fixedly connected to the engineering parameter short section; the fiber inlet port and the fiber outlet port 7 provided at both ends of the housing 1 are used for passing through the optical fiber seal to prevent the interior of the housing 1 from being contaminated, and a bolt hole can be provided inside the housing 1, thereby being threadedly connected to the engineering parameter short section.

[0037] In one embodiment, a cover plate is further provided on the housing 1. An opening is provided on the end face of the housing 1 away from the engineering parameter nipple, and the cover plate is provided to cover the opening. The cover plate is not shown in the drawings.

[0038] Three supporting components are sequentially arranged in the housing 1 along the first pre-examination direction. Each of the three supporting components is provided with a through embedding groove 100. The normal directions of the end faces of the three supporting components with the embedding groove 100 are different from each other. The embedding groove 100 is used to place the optical fiber. Figure 2 Combine Figure 8 As shown, the three support assemblies are respectively designated as the first support assembly 2, the second support assembly 4 and the third support assembly 5 for distinction. Figure 1 It can be seen that the end face of the first supporting component 2 where the embedding groove 100 is provided is horizontally arranged, and the normal direction of the end face where the embedding groove 100 is provided is vertically upward, which is defined as the X-axis direction; the end face of the second supporting component 4 where the embedding groove 100 is provided is vertically arranged, and the normal direction of the end face where the embedding groove 100 is provided is perpendicular to the plane and outward, which is defined as the Y-axis direction; the end face of the third supporting component 5 where the embedding groove 100 is provided is vertically arranged, and the normal direction of the end face where the embedding groove 100 is provided is the opposite direction of the first preset direction, which is defined as the Z-axis direction.

[0039] The bend-insensitive optical fiber 3 is inserted into the housing 1 and passes through the fiber input port, the embedded grooves 100 on the three supporting components and the fiber output port 7 in sequence. The portions where the bend-insensitive optical fiber 3 passes through the three supporting components are all provided with grating areas 200. The optical fiber Bragg grating is sensitive to parameters such as stress or acceleration. External forces may cause the central wavelength of the reflected light from the grating area 200 to drift. By demodulating the wavelength drift of the reflected light signal, the size of the physical quantity to be measured loaded on the grating area 200 can be inversely calculated.

[0040] In this embodiment, the grid area 200 and the supporting assembly in which it is located together constitute the sensor body, which is used to obtain vibration signals in different axial directions during the logging while drilling process. By setting three supporting assemblies continuously and in different directions in the housing 1, the posture of the sensor body is limited, thereby reducing the overall length of the bend-insensitive optical fiber 3, which is beneficial to reducing the bending loss of the optical fiber and improving the transmission quality of the optical signal detected by the sensor. In actual use, it is necessary to Figure 1 The housing 1 shown is rotated 90° clockwise and placed vertically for operation. According to the right-hand coordinate system, the thumb, index finger, and middle finger are pointed in different directions and are perpendicular to each other. The surface where the thumb and index finger are located represents the end surface where the embedding groove 100 is provided. The direction pointed by the middle finger represents the normal direction of the end surface where the embedding groove 100 is provided for each support component. Similarly, the sensor bodies where the three support components are located are named the first sensor body, the second sensor body, and the third sensor body according to the first predetermined orientation.

[0041] In one embodiment, the measurement wavelengths of the three grating areas 200 inscribed on the completely insensitive optical fiber are different from each other. In order to avoid mutual interference of the reflected light signals of different grating areas 200, the measurement wavelength ranges of different grating areas 200 do not overlap. For example, the upper limit of the measurement wavelength range of the grating area 200 of the first sensor body differs from the lower limit of the measurement wavelength range of the second sensor body by at least 5nm; the upper limit of the measurement wavelength range of the second sensor body differs from the lower limit of the measurement wavelength range of the third sensor body by at least 5nm. In this way, the phenomenon of wavelength overlap due to the small wavelength interval of the grating area 200 can be avoided during operation. The three grating areas 200 correspond to the vibration sensing detection on the X-axis, Y-axis and Z-axis respectively. Vibration sensing measurement can be performed by simply detecting the center wavelength drift of the measurement wavelength range of the corresponding grating area 200.

[0042] like Figure 6 、 Figure 7 and Figure 8 As shown, the three support assemblies all include a fixed base 300, a cantilever beam 400 and a mass block 500. The fixed base 300 is fixedly connected to the inner surface of the shell 1. The mass block 500 and the fixed base 300 are spaced apart, and the embedding groove 100 passes through the mass block 500 and the fixed base 300 of the same support assembly. The end faces of the mass block 500 and the fixed base 300 where the embedding groove 100 is provided are flush. The cantilever beam 400 is provided between the mass block 500 and the fixed base 300 and is respectively fixedly connected to the adjacent end faces of the mass block 500 and the fixed base 300; the bend-insensitive optical fiber 3 is respectively fixedly connected to the embedding grooves 100 on the mass block 500 and the fixed base 300; the grating region 200 of the bend-insensitive optical fiber 3 is tensioned and suspended between the mass block 500 and the fixed base 300 and is spaced apart from the cantilever beam 400; the mass block 500 and the cantilever beam 400 are spaced apart from the inner surface of the shell 1. The cantilever beam 400 does not contact the gate area 200. Under the action of axial vibration, the two ends of the gate area 200 on different sensor bodies are respectively subjected to axial tension or compression by the corresponding fixed seat 300 and the mass block 500, causing the gate area 200 to drift the initial center wavelength of the reflected light. By demodulating the drifted reflected light signal, sensitive measurement of vibration is achieved.

[0043] In one embodiment, the thickness of the cantilever beam 400 along the radial direction of the bend-insensitive optical fiber 3 is smaller than the thickness of the fixing seat 300 or the mass block 500 along the radial direction of the bend-insensitive optical fiber 3, and the mass of the cantilever beam 400 is smaller than the mass of the mass block 500. If the mass of the cantilever beam 400 is much smaller than the mass of the mass block 500, the cantilever beam 400 and the mass block 500 can be regarded as a whole.

[0044] In another embodiment, the spacing between different fixing seats 300 is greater than the spacing between corresponding mounting blocks. This arrangement is to reduce bending loss caused by excessive bending of the optical fiber during installation, while leaving sufficient installation margin.

[0045] like Figure 1 Combine Figure 8 As shown, before installing the sensor in the housing 1, it is necessary to pre-fix the three supporting components to the bend-insensitive optical fiber 3 in the direction shown in the figure. The change in the arrangement direction of the sensor body can effectively avoid the accident of fiber breakage caused by torsional shear force during the installation process. In this way, three sensor bodies located on the same bend-insensitive optical fiber 3 can be encapsulated. It should be noted that Figure 1 When the second and third sensors are installed on the housing 1, it is necessary to ensure that the curvature radius formed by the installation is greater than the minimum bending radius of the optical fiber. This is also to reduce the bending loss caused by excessive bending of the optical fiber during installation. At the same time, it is also necessary to leave sufficient installation margin for the three sensors in the housing 1.

[0046] like Figure 3 、 Figure 4 and Figure 5 As shown, to ensure that the sensors do not directly contact the inner surface of the housing 1, several mounting blocks 6 are further disposed within the housing 1. The inner surface of the housing 1 is provided with several placement grooves, which are spaced apart along a first predetermined direction. One end of the mounting block 6 is embedded in the placement groove, while the other end extends out of the placement groove and toward the interior of the housing 1. A fixing seat 300 is disposed at the end of the mounting blocks 6 away from the inner surface of the housing 1 and is fixedly connected to the mounting blocks 6. The fixing seat 300 and the mounting blocks 6 can be fixed by threaded connection or welding. The mounting blocks 6 and the housing 1 can be fixedly connected by welding.

[0047] In one embodiment, when the vibration signal of external drilling acts on the three sensing bodies, under the action of inertia, the end of the cantilever beam 400 away from the fixed base 300 and the mass block 500 are axially offset, compressing or stretching the gate area 200 on the three sensing bodies, causing the central wavelength of the reflected light from the gate area 200 to change. By demodulating the signal of the reflected light from the gate area 200, the vibration signal of the external drilling is obtained; the axial offset of the mass block 500 is caused by rotation relative to the end face of the fixed base 300 of the sensor body in which the embedding groove 100 is provided, that is, the mass block 500 rotates clockwise or counterclockwise by a certain angle relative to the end face of the fixed base 300 in which the embedding groove 100 is provided.

[0048] Assume that the length of the cantilever beam 400 is L, the cross-sectional area of ​​the cantilever beam 400 is A=wh, w is the current width of the cantilever beam 400, h is the current thickness of the cantilever beam 400, w0 is the initial width of the cantilever beam 400, h0 is the initial thickness of the cantilever beam 400, the distance between the center of the mass block 500 and the end of the fixed base 300 close to the cantilever beam 400 is L2, the length of the mass block 500 along the axial direction of the bend-insensitive optical fiber 3 is d, the thickness of the mass block 500 along the radial direction of the bend-insensitive optical fiber 3 is e, the total mass of the mass block 500 and the cantilever beam 400 is M, E is the elastic modulus of the cantilever beam 400, and I is the section moment of inertia of the cantilever beam 400. If the cantilever beam is subjected to an external acceleration of a, it can be seen from material mechanics analysis that the rotation angle θ(L) of the cantilever beam 400 at the end away from the fixed base 300 is This formula is the angle under ideal conditions.

[0049] Further introducing the influence of temperature T and pressure P on material parameters and geometric dimensions, the modified elastic modulus is E(T, P) = E0(1+βΔT)(1+γP), where E0 is the initial value of the elastic modulus, β is the temperature coefficient of the elastic modulus, γ is the pressure coefficient of the elastic modulus, ΔT is the temperature change, and P is the current pressure; the modified cantilever beam 400 length L(T, P) = L0(1+α T ΔT)(1-δP), L0 is the initial length of the cantilever beam 400, α T is the thermal expansion coefficient of the cantilever beam 400, δ is the compression coefficient of the cantilever beam 400; the distance L2(T, P) between the center of the corrected mass block 500 and the end of the fixed base 300 close to the cantilever beam 400 is L 20 (1+α T ΔT)(1-δP), L 20 is the initial length from the center of the mass block 500 to the nearest end of the fixed seat 300; the corrected section moment of inertia is I(T, P) = I0[1+α T ΔT-δ w P)(1+α T ΔT-δ h P) 3 , δ w is the width compression coefficient, δ h is the height compression coefficient; the thickness of the modified mass block 500 along the radial direction of the bend-insensitive optical fiber 3 is e(T, P)=e0(1+α e ΔT)(1-δ e P), e0 is the initial height of mass block 500, α e is the thermal expansion coefficient of mass 500, δ e is the compression coefficient of mass block 500; the corrected grating reflection wavelength λ B (T, P) = λ B0[1+(α λ +ξΔT)+(1-P e )F P ],λ B0 is the initial center wavelength of the gate region 200, α λ is the thermal expansion coefficient of optical fiber, ξ is the thermal-optical coefficient of optical fiber, P e is the elastic-optical coefficient, F P is the axial strain of the optical fiber caused by pressure; it satisfies the following relationship: the first axial sensitivity is The second axial sensitivity is The third axial sensitivity is Among them I x (T, P) = I x0 (1+α T ΔT-δ w P)(1+α T ΔT-δ h P) 3 , is the first initial moment of inertia, I y (T, P) = I y0 (1+α T ΔT-δ w P)(1+α T ΔT-δ h P) 3 , is the second initial moment of inertia. Replace the parameters L and L2, E, and I in the rotation angle formula with the corrected L(T, p), L2(T, P), E(T, P), and I(T, P), respectively. This yields the temperature- and pressure-corrected rotation angle θ(L, T, P) of the cantilever beam 400 at the end away from the fixing base 300.

[0050] In one embodiment, the surface of the bend-insensitive optical fiber 3 and the embedding groove 100 can be fixed by bonding the surface of the bend-insensitive optical fiber 3 to the inner surface of the embedding groove 100, or by providing a metal coating on the surface of the bend-insensitive sensor body and welding the metal coating to the inner surface of the embedding groove 100. The depth of the embedding groove 100 is greater than the diameter of the bend-insensitive optical fiber 3, and the width of the embedding groove 100 is equal to the diameter of the bend-insensitive optical fiber 3. This combination provides a larger surface area for the bend-insensitive optical fiber 3 to be attached.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter short section, characterized in that: include: A hollow shell, with a fiber inlet port and a fiber outlet port provided at both ends of the shell extending along a first preset direction, wherein the first preset direction is the length extension direction of the shell, and the shell is fixedly connected to the engineering parameter short section; Three support assemblies are sequentially arranged in the housing at intervals along the first pre-examination direction. The three support assemblies are all provided with through embedding grooves. The normal directions of the end surfaces of the three support assemblies on which the embedding grooves are provided are different from each other. The bend-insensitive optical fiber is passed through the housing and sequentially passes through the fiber inlet port, the embedded grooves on the three support components, and the fiber outlet port. The portions of the bend-insensitive optical fiber passing through the three support components are all provided with grid areas. The grid area and the supporting assembly together constitute a sensor body, which is used to obtain vibration signals in different axial directions during the logging while drilling process; The three supporting assemblies all include a fixed seat, a cantilever beam and a mass block; Let the length of the cantilever beam be L, the cross-sectional area of ​​the cantilever beam be A=wh, w is the current width of the cantilever beam, h is the current thickness of the cantilever beam, w0 is the initial width of the cantilever beam, h0 is the initial thickness of the cantilever beam, the distance between the center of the mass block and the end of the fixed seat close to the cantilever beam is L2, the length of the mass block along the axial direction of the bend-insensitive optical fiber is d, the thickness of the mass block along the radial direction of the bend-insensitive optical fiber is e, the total mass of the mass block and the cantilever beam is M, E is the elastic modulus of the cantilever beam, and I is the section moment of inertia of the cantilever beam; introducing the influence of temperature T and pressure P on material parameters and geometric dimensions, the corrected elastic modulus is ,in is the initial value of the elastic modulus, is the temperature coefficient of elastic modulus, is the pressure coefficient of the elastic modulus, is the temperature change, is the current pressure; the corrected cantilever beam length , is the initial length of the cantilever beam, is the thermal expansion coefficient of the cantilever beam, is the compression coefficient of the cantilever beam; the distance between the center of the corrected mass block and the end of the fixed seat close to the cantilever beam , is the initial length from the center of the mass block to the nearest end of the fixed seat; the corrected section moment of inertia is , is the width compression factor, is the height compressibility factor; the thickness of the corrected mass block along the radial direction of the bend-insensitive optical fiber , is the initial height of the mass block, is the thermal expansion coefficient of the mass block, is the compression coefficient of the mass block; the corrected grating reflection wavelength , is the initial center wavelength of the grating region, is the thermal expansion coefficient of the optical fiber, is the optical fiber thermo-optic coefficient, is the elastic-optical coefficient, is the axial strain of the optical fiber caused by pressure; it satisfies the following relationship: the first axial sensitivity is ; The second axial sensitivity is ; The third axial sensitivity is ,in , is the first initial moment of inertia, , is the second initial moment of inertia.

2. A three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter sub according to claim 1, characterized in that: The fixing seat is fixedly connected to the inner surface of the shell, the mass block and the fixing seat are arranged at intervals, and the embedding groove penetrates the mass block and the fixing seat of the same supporting assembly, the end faces of the mass block and the fixing seat where the embedding groove is opened are flush, the cantilever beam is arranged between the mass block and the fixing seat, and is respectively fixedly connected to the adjacent end faces of the mass block and the fixing seat; the bend-insensitive optical fiber is respectively fixedly connected to the embedding grooves on the mass block and the fixing seat; the grating area of ​​the bend-insensitive optical fiber is tensioned and suspended between the mass block and the fixing seat, and a gap is set with the cantilever beam; the mass block and the cantilever beam are set with a gap with the inner surface of the shell.

3. The three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter sub according to claim 2, characterized in that: The thickness of the cantilever beam along the radial direction of the bend-insensitive optical fiber is smaller than the thickness of the fixing seat or the mass block along the radial direction of the bend-insensitive optical fiber, and the mass of the cantilever beam is smaller than the mass of the mass block.

4. The three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter sub according to claim 3, characterized in that: When the vibration signal from external drilling acts on the three sensing bodies, the end of the cantilever beam away from the fixed seat undergoes axial displacement from the mass block due to inertia, compressing or stretching the grid areas on the three sensing bodies, causing the central wavelength of the reflected light from the grid areas to change. By demodulating the signal reflected from the grid areas, the vibration signal from external drilling is obtained. The axial displacement of the mass block occurs when the end face of the fixed seat of the sensor body on which it is located rotates relative to the grooved end face.

5. The three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter sub according to claim 4, characterized in that: The surface of the bend-insensitive optical fiber is bonded to the inner surface of the embedding groove, or a metal coating is provided on the surface of the bend-insensitive sensor body, and the metal coating is welded and fixed to the inner surface of the embedding groove; the depth of the embedding groove is greater than the diameter of the bend-insensitive optical fiber, and the width of the embedding groove is equal to the diameter of the bend-insensitive optical fiber.

6. The three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter sub according to claim 4, characterized in that: The measurement wavelength ranges of different grating areas do not overlap.

7. The three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter sub according to claim 2, characterized in that: It also includes several mounting blocks, the inner surface of the shell is provided with several placement grooves, and the several placement grooves are arranged at intervals along a first preset direction; one end of the mounting block is embedded in the placement groove, and the other end extends out of the placement groove and extends toward the inside of the shell; the fixing seat is provided at the end of the several mounting blocks away from the inner surface of the shell, and is fixedly connected to the mounting block.

8. The three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter sub according to claim 7, characterized in that: The spacing between different fixing seats is greater than the spacing between corresponding mounting blocks.

9. The three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter sub according to claim 1, characterized in that: The housing further comprises a cover plate. An opening is provided on the housing, and the cover plate is arranged at the opening.

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