Three-dimensional vibration fiber grating sensor for logging-while-drilling engineering parameter pup joint

Abstract

The invention provides a three-dimensional vibration fiber bragg grating sensor for a logging-while-drilling engineering parameter short section, and belongs to the technical field of fiber bragg grating sensors. Comprising a hollow shell, the two ends, extending in the first preset direction, of the shell are provided with a fiber inlet port and a fiber outlet port respectively, the first preset direction is the length extending direction of the shell, and the shell is fixedly connected with an engineering parameter nipple; the three supporting assemblies are sequentially arranged in the shell at intervals in the first pre-checking direction, through caulking grooves are formed in the three supporting assemblies, and the normal directions of the end faces, provided with the caulking grooves, of the three supporting assemblies are different from one another; the bending insensitive optical fiber is arranged on the shell in a penetrating mode and sequentially passes through the fiber inlet port, the caulking grooves in the three supporting assemblies and the fiber outlet port, and gate regions are arranged on the portions, passing through the three supporting assemblies, of the bending insensitive optical fiber; wherein the grid region and the supporting assembly where the grid region is located jointly form a sensing body, and the sensing body is used for obtaining vibration signals in different axial directions in the process of logging while drilling.

Description

Technical Field

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

[0002] Fiber-optic communication while drilling is an advanced communication technology used in the oil and gas industry. This technology is based on the field of fiber-optic communication. Due to the high frequency of its light waves, fiber-optic communication has a larger capacity and wider bandwidth than ordinary cable communication, and is suitable for the transmission of high-speed and broadband information; the loss of optical fiber is very small, which can greatly increase the transmission distance without relays. Fiber-optic communication transmits optical signals, which almost do not radiate outward, and has superior confidentiality performance. At the same time, it will not cause crosstalk between optical fibers in the same optical cable, is not subject to electromagnetic interference, and will not generate electric sparks to cause safety hazards to oil wells. It has good explosion-proof performance; the raw material for making glass optical fiber is quartz stone, which is more abundant than copper and aluminum used to make cables, and optical fiber is environmentally friendly and has a long service life.

[0003] In the process of downhole measurement while drilling, the accurate measurement of three-dimensional vibration parameters near the drill bit is of great significance to the safety and efficiency of the drilling process. However, the downhole vibration sensors used in the existing measurement while drilling technology are mostly electrical sensors. In the harsh environment of high temperature, high pressure and strong electromagnetic interference in the well, the application cost of the corresponding electrical sensors is high. At the same time, if downhole electrical sensors are used in the fiber-optic measurement while drilling system, additional photoelectric conversion modules need to be designed, thereby increasing the risk of safe operation of the scheme. Fiber Bragg grating sensing technology has the advantages of high temperature and high pressure resistance and electromagnetic interference resistance, and has been widely used in the field of petroleum engineering monitoring. Fiber Bragg grating sensors can be directly connected to the fiber-optic measurement while drilling system to efficiently transmit the collected physical quantity information through optical signals. In the application of the fiber-optic measurement while drilling system, there is a large basic optical transmission loss, which is mainly caused by the following two reasons. First, the fiber-optic measurement while drilling system requires multiple fiber optic connectors to form a complete link. The fiber optic connectors required include downhole wet joints, wellhead wet joints and photoelectric slip rings. The cooperation of these connectors can solve the problem of difficult installation of optical cables, thereby simplifying the process and improving construction efficiency. However, the use of these connectors increases the basic optical transmission loss of the fiber optic measurement system while drilling. At the same time, the harsh working environment of high temperature and high pressure underground will accelerate the aging and deformation of the sealing ring, leading to the intrusion of moisture and pollutants, causing the risk of secondary increase in the optical transmission loss of the fiber optic communication system while drilling. Secondly, since the optical cable needs to be continuously released during the process of fiber optic measurement while drilling, the main line warehouse and the relay line warehouse need to store a length of optical cable in the line warehouse. The optical cable will be spirally wound on the wire rod in the line warehouse. The macrobending loss caused by this spiral winding method will further increase the basic loss of the fiber optic measurement system while drilling. On the other hand, in order to meet the requirements of high temperature and high pressure engineering operations, the design of the engineering parameter short section of the downhole drill pipe should try to ensure the use strength of the short section. Therefore, the size of the sensor installation area designed in the engineering parameter short section is generally small and flat. In summary, 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.

[0004] Therefore, it is very necessary to provide a three-dimensional vibration fiber 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 grating sensor for a logging engineering parameter short section which has a compact structure, can be used to measure three axial vibration accelerations respectively, and is suitable for the logging engineering parameter short section application scenario and output while drilling.

[0006] The present invention provides a three-dimensional vibration fiber 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 respectively arranged at two ends of the shell extending along a first preset direction, the first preset direction being the length extension direction of the shell, and the shell being fixedly connected to the engineering parameter short section;

[0008] Three support components are sequentially arranged in the housing at intervals along the first pre-examination direction, and each of the three support components is provided with a through embedding groove, and the normal directions of the end surfaces of the three support components on which the embedding grooves are provided are different from each other;

[0009] The bend-insensitive optical fiber is inserted into the housing and sequentially passes through the fiber inlet port, the embedding grooves on the three support components and the fiber outlet port, and the portions where the bend-insensitive optical fiber passes through the three support components are all provided with grid areas;

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

[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 fixedly connected to the adjacent end faces of the mass block and the fixed seat respectively; the bend-insensitive optical fiber is fixedly connected to the embedding grooves on the mass block and the fixed seat respectively; 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 gate area on the three sensor bodies, causing the central wavelength of the reflected light in the gate area to change, and the vibration signal of the external drilling is obtained by demodulating the signal of the reflected light in the gate 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 bend-insensitive surface located at the 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] Further 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; introduce the influence of temperature T and pressure P on material parameters and geometric dimensions, and the corrected elastic modulus is E(T, P)=E0(1+βΔT)(1+γP), wherein 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 factor, 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 axis 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 a plurality of mounting blocks, the inner surface of the shell is provided with a plurality of placement grooves, and the plurality of 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 arranged at the end of the plurality of mounting blocks away from the inner surface of the shell, and is fixedly connected to the mounting blocks.

[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, it further includes a cover plate, the shell is provided with an opening, and the cover plate is covered at the opening.

[0020] The three-dimensional vibration fiber grating sensor for a logging while drilling engineering parameter short section provided by the present invention has the following beneficial effects compared with the prior art:

[0021] (1) The present invention is to set a separate bending-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, so as to measure the vibration signals of the three axial directions of the engineering parameter short section, reduce the bending loss of the sensor, and improve the reliability and transmission quality of the sensor measurement results;

[0022] (2) The supporting components include a fixed seat, a cantilevered mass block, and a cantilever beam connecting the fixed seat and the mass block. Under the influence of axial acceleration, the mass block will undergo a certain axial deformation relative to the fixed seat, thereby compressing or stretching the gate area, causing the center wavelength of the emitted light in the gate 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 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 drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

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

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

[0027] Figure 3 A three-dimensional diagram of the explosion state of a three-dimensional vibration fiber grating sensor for a logging while drilling engineering parameter short section according to the present invention after hiding the cover plate and the bending-insensitive optical fiber;

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

[0029] Figure 5 It is a front view of a three-dimensional vibration fiber grating sensor for a logging while drilling engineering parameter short section of the present invention after removing the mounting block;

[0030] Figure 6 A top view of a support assembly of a three-dimensional vibration fiber grating sensor for a logging while drilling engineering parameter short section according to the present invention;

[0031] Figure 7 It is a front view of a support assembly of a three-dimensional vibration fiber grating sensor for a logging while drilling engineering parameter short section 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 grating sensor for a logging while drilling engineering parameter pup joint.

[0033] Figure numerals: 1. Shell; 2. First supporting assembly; 3. Bend-insensitive optical fiber; 4. Second supporting assembly; 5. Third supporting 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 described embodiments 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 creative work 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 measurement while drilling. Conventional fiber winding methods and multi-fiber connector connection methods will cause macrobending loss and transmission loss. Figure 1 , Figure 2 and Figure 3 It can be seen that the present invention provides a three-dimensional vibration fiber grating sensor for a logging while drilling engineering parameter short section, comprising:

[0036] The hollow shell 1 has a fiber inlet port and a fiber outlet port 7 respectively arranged 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 shell 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 shell 1 are used for the passage of the optical fiber seal to prevent the inside of the shell 1 from being contaminated, and a bolt hole can be provided inside the shell 1 to be threadedly connected to the engineering parameter short section.

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

[0038] Three support components are sequentially arranged in the housing 1 at intervals along the first pre-examination direction. The three support components are all provided with through embedding grooves 100. The normal directions of the end faces of the three support components with the embedding grooves 100 are different from each other. The embedding grooves 100 are used to place optical fibers. Figure 2 Combination Figure 8 As shown, the three support components are respectively referred to as the first support component 2, the second support component 4 and the third support component 5 for distinction. Figure 1 It can be seen that the end face of the first supporting component 2 with the embedded groove 100 is horizontally arranged, and the normal direction of the end face with the embedded groove 100 is vertically upward, and this direction is defined as the X-axis direction; the end face of the second supporting component 4 starting to embed the groove 100 is vertically arranged, and the normal direction of the end face with the embedded groove 100 is perpendicular to the plane and outward, and this direction is defined as the Y-axis direction; the end face of the third supporting component 5 with the embedded groove 100 is vertically arranged, and the normal direction of the end face with the embedded groove 100 is the opposite direction of the first preset direction, and this direction 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, and the parts where the bend-insensitive optical fiber 3 passes through the three supporting components are all provided with grating areas 200; the fiber grating is sensitive to parameters such as stress or acceleration, and the external force will cause the central wavelength of the reflected light of 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 a sensor body, and the sensor body is used to obtain vibration signals in different axial directions during the logging while drilling process. By setting three supporting assemblies 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, which is the working posture. According to the right-hand coordinate system rule, 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 is the end surface where the embedding groove 100 is opened, and the direction pointed by the middle finger is the normal direction of the end surface where the embedding groove 100 is opened for each supporting component. Similarly, the sensor bodies where the three supporting components are located are named the first sensor body, the second sensor body and the third sensor body according to the first preset direction.

[0041] In one embodiment, the measurement wavelengths of the three grid areas 200 inscribed on the completely insensitive optical fiber are different from each other. In order to avoid mutual interference of reflected light signals from different grid areas 200, the measurement wavelength ranges of different grid areas 200 do not overlap. For example, the upper limit of the measurement wavelength range of the gate 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 gate area 200 can be avoided during operation. The three grid areas 200 correspond to the vibration sensing detection on the X-axis, Y-axis and Z-axis respectively. Vibration perception measurement can be performed by only detecting the center wavelength drift of the measurement wavelength range of the corresponding gate area 200.

[0042] like Figure 6 , Figure 7 and Figure 8 As shown, the three support components all include a fixed seat 300, a cantilever beam 400 and a mass block 500. The fixed seat 300 is fixedly connected to the inner surface of the shell 1. The mass block 500 and the fixed seat 300 are spaced apart, and the embedding groove 100 runs through the mass block 500 and the fixed seat 300 of the same support component. The end surfaces of the mass block 500 and the fixed seat 300 where the embedding groove 100 is provided are flush. The cantilever beam 400 is disposed between the mass block 500 and the fixed seat 300, and is fixedly connected to the adjacent end surfaces of the mass block 500 and the fixed seat 300 respectively; the bend-insensitive optical fiber 3 is fixedly connected to the embedding grooves 100 on the mass block 500 and the fixed seat 300 respectively; the grating region 200 of the bend-insensitive optical fiber 3 is tensioned and suspended between the mass block 500 and the fixed seat 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 is not in contact with 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 stretching or compression by the corresponding fixed seat 300 and the mass block 500, so that the initial central wavelength of the reflected light of the gate area 200 drifts. 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 installation blocks. This arrangement is to reduce the bending loss caused by excessive bending of the optical fiber during installation, and sufficient installation margin is required.

[0045] like Figure 1 Combination Figure 8 As shown, before installing the sensor in the housing 1, the three support components need to be pre-fixed with 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 the optical fiber being broken due to the torsional shear force during the installation process. In this way, three sensor bodies located on the same bend-insensitive optical fiber 3 can be packaged. It should be noted that Figure 1 When the second sensor and the third sensor 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, in order to ensure that each sensor body does not directly contact the inner surface of the housing 1, a plurality of mounting blocks 6 are further arranged in the housing 1, and a plurality of placement grooves are arranged on the inner surface of the housing 1, and the plurality of placement grooves are arranged at intervals along the first preset direction; one end of the mounting block 6 is embedded in the placement groove, and the other end extends out of the placement groove and extends toward the inside of the housing 1; the fixing seat 300 is arranged at the end of the plurality of mounting blocks 6 away from the inner surface of the housing 1, and is fixedly connected to the mounting block 6. The fixing seat 300 and the mounting block 6 can be fixed by threaded connection or welding. The mounting block 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 sensor bodies, under the action of inertia, the end of the cantilever beam 400 away from the fixed seat 300 is axially offset from the mass block 500, and the gate area 200 on the three sensor bodies is compressed or stretched, so that the central wavelength of the reflected light of the gate area 200 changes, and the vibration signal of the external drilling is obtained by demodulating the signal of the reflected light of the gate area 200; the axial offset of the mass block 500 is a rotation relative to the end face of the fixed seat 300 where the embedding groove 100 is provided, that is, the mass block 500 is rotated clockwise or counterclockwise by a certain angle relative to the end face of the fixed seat 300 where 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 seat 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, I is the section inertia moment of the cantilever beam 400, if the external acceleration is a, it can be known from the material mechanics analysis that the rotation angle θ(L) of the cantilever beam 400 at the end away from the fixed seat 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 seat 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 moment of inertia of the section 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 factor, δ h is the height compression coefficient; the thickness of the corrected 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 factor 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 grating 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 axis 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. The parameters L and L2, E and I in the rotation angle formula are replaced with the corrected L(T, p), L2(T, P), E(T, P) and I(T, P) respectively. The rotation angle θ(L, T, P) of the cantilever beam 400 at the end away from the fixing seat 300 after temperature and pressure correction can be obtained.

[0050] In one embodiment, the surface of the bend-insensitive optical fiber 3 and the embedding groove 100 are fixed by bonding the surface of the bend-insensitive optical fiber 3 to the inner surface of the embedding groove 100, or providing a metal coating on the surface of the bend-insensitive sensor body, and welding and fixing 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 has a larger surface bonding area for the bend-insensitive optical fiber 3.

[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 protection scope of the present invention.

Claims

1. A three-dimensional vibration fiber 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 respectively arranged at two ends of the shell extending along a first preset direction, the first preset direction being the length extension direction of the shell, and the shell being fixedly connected to the engineering parameter short section; Three support components are sequentially arranged in the housing at intervals along the first pre-examination direction, and each of the three support components is provided with a through embedding groove, and the normal directions of the end surfaces of the three support components on which the embedding grooves are provided are different from each other; The bend-insensitive optical fiber is inserted into the housing and sequentially passes through the fiber inlet port, the embedding grooves on the three support components and the fiber outlet port, and the portions where the bend-insensitive optical fiber passes through the three support components are all provided with grid areas; The grid area and the supporting assembly together constitute a sensor body, and the sensor body is used to obtain vibration signals in different axial directions during logging while drilling.

2. A three-dimensional vibration fiber grating sensor for a logging while drilling engineering parameter short section according to claim 1, characterized in that: The three support 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 support 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 spaced apart from the cantilever beam; the mass block and the cantilever beam are spaced apart from the inner surface of the shell.

3. A three-dimensional vibration fiber grating sensor for a logging while drilling engineering parameter short section 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. A three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter short section according to claim 3, characterized in that: 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 and the mass block are axially offset, compressing or stretching the grid area on the three sensor bodies, so that the central wavelength of the reflected light in the grid area changes, and the vibration signal of the external drilling is obtained by demodulating the signal of the reflected light in the grid area; the axial offset of the mass block is the rotation of the end face of the fixed seat of the sensor body where it is located.

5. A three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter short section 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 optical fiber located at the 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. A three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter short section according to claim 4, characterized in that: Assume that the length of the cantilever beam is L, the cross-sectional area of ​​the cantilever beam is 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 inertia moment of the cantilever beam; introduce the influence of temperature T and pressure P on material parameters and geometric dimensions, and 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 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 factor, 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 the optical fiber, ξ is the thermal-optical coefficient of the 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 axis 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.

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

8. The three-dimensional vibration fiber grating sensor for a logging while drilling engineering parameter short section according to claim 2, characterized in that: It also includes a plurality of mounting blocks, wherein the inner surface of the shell is provided with a plurality of placement grooves, and the plurality of 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; a fixing seat is arranged at the end of the plurality of mounting blocks away from the inner surface of the shell, and is fixedly connected to the mounting blocks.

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

10. The three-dimensional vibration fiber Bragg grating sensor for a logging while drilling engineering parameter short section according to claim 1, characterized in that: The housing also includes a cover plate. An opening is arranged on the housing, and the cover plate is arranged at the opening.

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