Optical fiber sensor for acoustic wave detection based on elastic substrate supporting multi-directional detection

Abstract

The present application relates to the field of geophysical well logging, and discloses a fiber-optic sensing acoustic wave detector based on an elastic substrate for supporting multi-directional detection, which comprises a fiber-optic sensing acoustic wave detector body, a plurality of acoustic wave receivers arranged in an equicircular central angle form inside the fiber-optic sensing acoustic wave detector body, an elastic substrate and a fiber-optic cable arranged in each acoustic wave receiver, the elastic substrate is used for sensitization, a through hole is arranged between the central position of the top surface of the elastic substrate and the central position of the bottom surface of the elastic substrate, the fiber-optic cable is fixed on the elastic substrate and used for conducting a laser pulse signal, the fiber-optic cable passes through the through hole and extends to the inside of the elastic substrate, and a grating is engraved on the position where the fiber-optic cable is located inside the elastic substrate, the grating is used for reflecting the laser pulse signal. The circumferential direction receiving can be realized simultaneously, the fiber-optic cable winding is not needed, and defects such as serious optical attenuation and fiber-optic cable breakage caused by too small curvature radius of the fiber-optic cable winding can be avoided.

Description

Technical Field

[0001] This disclosure relates to the field of geophysical logging technology, and in particular to a fiber optic sensing acoustic detector based on an elastic substrate that supports multi-directional detection. Background Technology

[0002] Under current technology, the main methods of acoustic logging using fiber optic sensing include: external distributed fiber optic monitoring and in-well fiber optic acoustic sensing logging tools. Among these, fiber optic acoustic sensing logging tools are divided into two types based on whether they have azimuth resolution capability: azimuth detection and overall detection. Azimuth detection fiber optic acoustic sensing logging tools employ orthogonal dipole transmission and azimuth reception. Azimuth reception utilizes two technical solutions: independent reception with four circumferential fiber optic rings and three-component reception with a central fiber optic spiral winding.

[0003] The main steps of distributed fiber optic acoustic logging include: emitting a laser and outputting an optical pulse signal, the period of which is preset; responding to changes in the measurement signal by loading the measurement signal into the optical pulse signal to modulate it; and demodulating the modulated optical pulse signal to output the measurement signal. Distributed fiber optic acoustic logging mainly uses full-section measurement, thereby achieving full-time, full-space, wide-frequency large-volume signal acquisition, and significantly improving signal quality.

[0004] The fiber optic sensing orthogonal dipole acoustic logging system includes an in-well fiber optic sensing orthogonal dipole acoustic logging device, which comprises a cylindrical instrument housing and a fiber optic acoustic dipole sensor. A fiber optic gyroscope, a sound-insulating short section, and a dipole sound source generator are vertically mounted sequentially at the bottom of the fiber optic acoustic dipole sensor. The surface logging vehicle lowers and raises the in-well fiber optic sensing orthogonal dipole acoustic logging device, providing power to drive the dipole sound source generator to continuously and repeatedly emit dipole acoustic signals during operation. A surface DAS modulator / demodulator emits laser pulses into the fiber optic acoustic dipole sensor to collect the backscattered Rayleigh waves within the sensor. The fiber optic sensing orthogonal dipole acoustic logging system can operate for extended periods at high temperatures to achieve high-speed upward data transmission.

[0005] However, the technical solution of the distributed fiber optic acoustic logging method outside the well as described above uses monopole emission inside the well as the optical fiber sensing orthogonal dipole acoustic logging system described above uses multiple spiral tubes wound around the fiber optic cylindrical receivers to achieve azimuth reception. Due to the limitations of the radial dimensions of the wellbore and the instrument, the fiber curvature radius is small, making it easy to break and with large light attenuation. Summary of the Invention

[0006] The purpose of this invention is to provide at least one fiber optic acoustic wave detector and device, system, method, and computer program based on a flexible substrate supporting multi-directional detection. In the fiber optic acoustic wave detector based on a flexible substrate supporting multi-directional detection, a ring-shaped receiving array formed by multiple acoustic wave receivers is employed. Bragg gratings are arranged in the ring-shaped receiving array with equal central angles, and the sensitivity is enhanced by a flexible substrate. This enables circumferential detection under miniaturized receiver conditions, eliminating the need for fiber winding and avoiding defects such as severe optical attenuation and fiber breakage caused by excessively small curvature radius of the wound fiber.

[0007] To address the aforementioned technical problems, at least one embodiment of this application provides a fiber optic sensing acoustic detector based on an elastic substrate supporting multi-directional detection, comprising:

[0008] The main body of the fiber optic sensing acoustic wave detector;

[0009] Multiple acoustic wave receivers are arranged inside the fiber optic acoustic wave detector body at equal central angles, and each acoustic wave receiver contains a flexible substrate and an optical fiber; wherein:

[0010] The elastic substrate is used for sensitization, and a through hole is provided between the center position of the top surface of the elastic substrate and the center position of the bottom surface of the elastic substrate.

[0011] The optical fiber is fixed on the elastic substrate and is used to conduct laser pulse signals. The optical fiber passes through the through hole and extends into the interior of the elastic substrate. A grating is etched at the position of the optical fiber inside the elastic substrate. The grating is used to reflect the laser pulse signals.

[0012] At least one embodiment of this application also provides an optical fiber sensing acoustic wave detection device, comprising:

[0013] The main body of the fiber optic sensing acoustic wave detection device;

[0014] The remote transmission module is located inside the fiber optic sensing acoustic wave detection device and is used to receive external transmission commands. The transmission commands are used to control the transmission line to provide transmission drive signals to the transmitting acoustic system.

[0015] The transmitting line is located inside the fiber optic sensing acoustic wave detection device and connected to the remote transmission module, and is used to provide a transmission drive signal to the transmitting acoustic system in response to the transmission command.

[0016] The transmitting acoustic system is located inside the fiber optic sensing acoustic wave detection device and connected to the transmitting line. It is used to amplify the transmitting drive signal provided by the transmitting line and perform the operation of exciting acoustic waves.

[0017] A sound insulation body is disposed between the transmitting sound system and the receiving sound system to block the direct wave excited by the transmitting sound system and propagating along the outer shell of the fiber optic sensing acoustic wave detection device.

[0018] The receiving acoustic system is located inside the main body of the fiber optic sensing acoustic wave detection device. It is used to conduct externally emitted laser pulse signals and to enhance the sensitivity of weak acoustic signals from the outside to cause disturbance in the optical fiber located inside the receiving acoustic system, thereby coupling the mechanical vibration caused by the weak acoustic signal into the reflected light signal of the laser pulse signal.

[0019] The receiving acoustic system includes a fiber optic sensing acoustic detector, as described above, which supports multi-directional detection based on an elastic substrate.

[0020] At least one embodiment of this application also provides an optical fiber sensing acoustic wave detection system, comprising:

[0021] The fiber optic sensing acoustic wave detection device described above;

[0022] The control system, connected to the remote transmission module of the fiber optic acoustic wave detection device, is used to control the transmitting acoustic system of the fiber optic acoustic wave detection device to perform the operation of exciting acoustic waves, and to perform the operation of transmitting laser pulses to the fiber optic acoustic wave detection device, and to generate acoustic logging data based on the reflected light signal of the laser pulse signal collected by the fiber optic acoustic wave detection device; wherein, the reflected light signal includes a first reflected light signal without acoustic wave disturbance and a second reflected light signal coupled with acoustic wave vibration.

[0023] At least one embodiment of this application also provides a fiber optic sensing acoustic wave detection method, based on the system described above, the method comprising:

[0024] Determine the current well depth at which the fiber optic sensing acoustic detection device is located in the well to be tested;

[0025] A laser pulse is emitted to the fiber optic sensing acoustic wave detection device, and the first reflected light signal reflected by each acoustic wave receiver in the fiber optic sensing acoustic wave detection device is acquired.

[0026] Send a transmission command to the fiber optic sensing acoustic wave detection device to control the transmission line to provide a transmission drive signal to the transmission acoustic system, so that the transmission acoustic system amplifies the transmission drive signal provided by the transmission line and performs the operation of exciting acoustic waves, and acquires the second reflected light signal coupled with acoustic wave vibration reflected by each acoustic wave receiver in the fiber optic sensing acoustic wave detection device under acoustic wave disturbance.

[0027] Based on the first and second reflected light signals reflected by each receiving acoustic system, the strain of the optical fiber in each acoustic receiver at the current well depth is determined by a preset strain determination method.

[0028] Based on the strain of the optical fiber in each acoustic receiver, waveform curves for each corresponding azimuth of the acoustic receiver are plotted, and the waveform curves for all azimuths are used as acoustic logging data for the well to be logged at the current well depth.

[0029] At least one embodiment of this application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the fiber optic sensing acoustic wave detection method as described above.

[0030] The fiber optic acoustic wave detector, fiber optic acoustic wave detection device, fiber optic acoustic wave detection system, fiber optic acoustic wave detection method, and computer program based on an elastic substrate and supporting multi-directional detection provided in the embodiments of this application, compared with the prior art, adopt a ring receiving array, which can realize circumferential directional reception under the condition of radial space limitation, without the need for fiber winding, and can avoid defects such as severe light attenuation and fiber breakage caused by excessively small curvature radius of fiber winding.

[0031] In addition, the optical fiber in the fiber optic sensing acoustic detector based on an elastic substrate that supports multi-directional detection is a single-mode optical fiber.

[0032] In addition, a boost unit and a transmitting transducer are provided in the transmitting acoustic system of the fiber optic sensing acoustic wave detection device; wherein:

[0033] The boost unit is used to amplify the transmission drive signal provided by the transmission line, thereby driving the transmission transducer to vibrate;

[0034] The transmitting transducer is used to convert electrical energy into mechanical energy according to the amplified transmitting drive signal, and then excite sound waves through vibration; wherein, the transmitting transducer includes:

[0035] One or more of the following: monopole emitter transducer, dipole emitter transducer, and quadrupole emitter transducer.

[0036] In addition, multiple fiber optic acoustic detectors based on elastic substrates supporting multi-directional detection are arranged at equal intervals along the axis of the fiber optic acoustic detection device body in the receiving acoustic system of the fiber optic acoustic detection device.

[0037] Furthermore, when the fiber optic sensing acoustic wave detection device is equipped with multiple fiber optic sensing acoustic wave detectors that support multi-directional detection based on elastic substrates, the gratings located inside different fiber optic sensing acoustic wave detectors that support multi-directional detection based on elastic substrates have different wavelengths.

[0038] In addition, the reflected light signal of the laser pulse signal in the optical fiber sensing acoustic wave detection device includes a first reflected light signal without acoustic wave disturbance and a second reflected light signal coupled with acoustic wave vibration.

[0039] In addition, the method further includes connecting the fiber optic sensing acoustic wave detection device via an optical-electric composite cable:

[0040] By controlling the optical fiber composite cable to perform lifting or lowering operations, the position of the optical fiber sensing acoustic wave detection device in the well to be tested can be controlled. Attached Figure Description

[0041] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0042] Figure 1 This is a schematic diagram of the structure of an optical fiber sensing acoustic wave detection device provided in an embodiment of the present disclosure;

[0043] Figure 2 A schematic diagram of another fiber optic sensing acoustic wave detection device provided in an embodiment of this disclosure;

[0044] Figure 3 A flowchart of an optical fiber sensing acoustic wave detection method provided in this embodiment of the disclosure;

[0045] Figure 4 A schematic diagram of the structure of a fiber optic sensing acoustic wave detector based on an elastic substrate supporting multi-directional detection, provided in an embodiment of this disclosure;

[0046] Figure 5 A side cross-sectional view of an optical fiber sensing acoustic wave detection device provided in an embodiment of this disclosure;

[0047] Figure 6 This is a cross-sectional view of an optical fiber sensing acoustic wave detection device provided in an embodiment of this disclosure.

[0048] Figure label:

[0049] exist Figure 2 In the middle: 1-plug; 2-receiving acoustic system; 21-metal outer casing; 22-rubber bladder; 23-receiver; 24-optical fiber; 3-sound insulation body; 4-transmitting acoustic system; 41-quadrupole transmitting transducer; 42-dipole transmitting transducer; 43-monopolar transmitting transducer; 5-transmitting line; 6-well inclination azimuth logging instrument; 7-telescopic module; 8-horsehead; 9-optical composite cable. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been presented in the various embodiments of the present invention to enable the reader to better understand the present invention. However, the technical solutions claimed in the present invention can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0051] To facilitate understanding of the embodiments of this application, relevant content regarding the fiber optic sensing acoustic wave detection device will be introduced first.

[0052] Example 1

[0053] The embodiments of the present invention relate to an optical fiber sensing acoustic wave detector based on an elastic substrate that supports multi-directional detection.

[0054] Compared with the prior art, the embodiments of the present invention achieve circumferential detection by employing a circumferentially arranged Bragg grating and supplementing it with an elastic substrate for enhanced sensitivity.

[0055] The following is a detailed description of the implementation details of the fiber optic sensing acoustic detector based on an elastic substrate that supports multi-directional detection in this embodiment. The following content is only for the convenience of understanding and is not necessary for implementing this solution.

[0056] Figure 4 This is a schematic diagram of the structure of a fiber optic sensing acoustic wave detector based on an elastic substrate supporting multi-directional detection, as provided in an embodiment of this disclosure. Figure 4 As shown, the fiber optic sensing acoustic detector based on an elastic substrate supporting multi-directional detection provided in this embodiment includes:

[0057] The main body of the fiber optic sensing acoustic wave detector;

[0058] Multiple acoustic wave receivers are arranged at equal central angles inside the fiber optic acoustic wave detector body. Each acoustic wave receiver contains a flexible substrate and an optical fiber; wherein:

[0059] An elastic substrate for enhancing sensitivity, wherein a through hole is provided between the center position of the top surface of the elastic substrate and the center position of the bottom surface of the elastic substrate;

[0060] An optical fiber, fixed on an elastic substrate, is used to conduct laser pulse signals. The optical fiber passes through a through hole and extends into the interior of the elastic substrate. A grating is etched at the position of the optical fiber inside the elastic substrate. The grating is used to reflect the laser pulse signals. The elastic substrate and the grating deform synchronously under the disturbance of acoustic waves.

[0061] The fiber optic sensing acoustic detector body can be cylindrical, and fiber optic protective tail tubes are provided at both ends of the through hole of each elastic substrate to prevent the fiber optic cable from breaking at the end face of the substrate.

[0062] It is understandable that the elastic substrate is used for sensitivity enhancement. The optical fiber located inside the substrate is axially connected and fixed to the elastic substrate. An elastic substrate and the optical fiber fixed on the elastic substrate can form an acoustic wave receiver, and multiple acoustic wave receivers form a ring receiving array inside the optical fiber sensing acoustic wave detector body in the form of equal central angles.

[0063] In some embodiments, the optical fiber is a single-mode optical fiber.

[0064] Alternatively, single-mode optical fiber has advantages such as resistance to electromagnetic interference, high temperature resistance, large bandwidth, and long transmission distance.

[0065] In some embodiments, the grating is a Bragg grating.

[0066] The fiber optic sensing acoustic detector based on an elastic substrate that supports multi-directional detection provided in this embodiment can be applied to related acoustic logging instruments.

[0067] As an example, in the fiber optic sensing acoustic detector based on an elastic substrate that supports multi-directional detection provided in this embodiment, the optical fiber can be used to conduct externally emitted laser pulse signals; the elastic substrate can be used to sensitize weak acoustic signals from the outside to cause disturbance in the optical fiber fixedly connected to it, thereby coupling the mechanical vibration caused by the weak acoustic signal into the reflected light signal of the laser pulse signal.

[0068] The elastic substrate is used for sensitivity enhancement. Both the elastic substrate and the optical fiber fixed along its axis deform synchronously under acoustic wave disturbance. When used alone in a fiber-optic acoustic wave detector, the elastic substrate can be installed around a hollow cylindrical metal support with four grooves, with the upper and lower ends of the elastic substrate fixed to the sides of the support. When used in a related acoustic logging device, adjacent supports are spaced apart by a bracket made of low-density non-metallic material. This allows acoustic waves propagating along the support frame to be reflected at the interface between the metal support and the high-temperature resistant low-density non-metallic material, reducing the acoustic wave energy propagating along the frame formed by the support and bracket. A through-hole is provided near the outer surface of the substrate along the receiving acoustic axis. An optical fiber encased in a corrosion-resistant stainless steel shell and etched with a Bragg grating is placed within the through-hole. The grating, with a length of 8–12 mm, is located in the center of the elastic substrate, and the stainless steel encapsulation is tightly fitted to the inner wall of the through-hole. The grating within the elastic substrate deforms synchronously with the elastic substrate, effectively transmitting the small deformations of the elastic substrate. The elastic substrate serves two purposes: coupling acoustic waves and inducing changes in fiber length, and encapsulating the grating to protect the optical fiber.

[0069] It should be noted that in the fiber optic sensing acoustic wave detector based on an elastic substrate that supports multi-directional detection provided in this embodiment, the number of acoustic wave receivers can be set according to actual needs.

[0070] For example, if there are 4 sound wave receivers in the receiving array, equal intervals can be understood as the 4 positions / directions of 3 o'clock, 6 o'clock, 9 o'clock and 12 o'clock; that is, these 4 sound wave receivers are set at the 4 positions / directions of 3 o'clock, 6 o'clock, 9 o'clock and 12 o'clock.

[0071] The fiber optic acoustic wave detector based on an elastic substrate that supports multi-directional detection provided in the embodiments of this application has a simpler structure than the prior art, can simultaneously detect acoustic wave signals from multiple directions, and its working stability and reliability are also improved.

[0072] Example 2

[0073] Based on the foregoing embodiments, the present invention relates to an optical fiber sensing acoustic wave detection device.

[0074] Compared with the prior art, the embodiments of the present invention achieve circumferential detection under the condition of receiver miniaturization by using circumferentially arranged Bragg gratings and supplementing them with elastic substrate for sensitivity enhancement.

[0075] The following is a detailed description of the implementation details of the fiber optic sensing acoustic wave detection device in this embodiment. The following content is only for the convenience of understanding and is not necessary for implementing this solution.

[0076] Figure 1 This is a schematic diagram of the structure of an optical fiber sensing acoustic wave detection device provided in an embodiment of this disclosure, as shown below. Figure 1 As shown, the fiber optic sensing acoustic wave detection device provided in this embodiment includes:

[0077] The main body of the fiber optic sensing acoustic wave detection device;

[0078] The remote transmission module is located inside the fiber optic sensing acoustic wave detection device and is used to receive external transmission commands. The transmission commands are used to control the transmission line to provide transmission drive signals to the transmitting acoustic system.

[0079] The transmitting line is located inside the fiber optic sensing acoustic wave detection device and connected to the remote transmission module, and is used to provide a transmission drive signal to the transmitting acoustic system in response to the transmission command.

[0080] The transmitting acoustic system is located inside the fiber optic sensing acoustic wave detection device and connected to the transmitting line. It is used to amplify the transmitting drive signal provided by the transmitting line and perform the operation of exciting acoustic waves.

[0081] A sound insulation body is disposed between the transmitting sound system and the receiving sound system to block the direct wave excited by the transmitting sound system and propagating along the outer shell of the fiber optic sensing acoustic wave detection device.

[0082] The receiving acoustic system is located inside the main body of the fiber optic sensing acoustic wave detection device. It is used to conduct externally emitted laser pulse signals and to enhance the sensitivity of weak acoustic signals from the outside to cause disturbance in the optical fiber located inside the receiving acoustic system, thereby coupling the mechanical vibration caused by the weak acoustic signal into the reflected light signal of the laser pulse signal.

[0083] The receiving acoustic system includes a fiber optic sensing acoustic detector based on an elastic substrate that supports multi-directional detection, as described in the aforementioned embodiment.

[0084] The shape of the fiber optic sensing acoustic wave detection device can be cylindrical.

[0085] It is understood that in the receiving acoustic system of the fiber optic sensing acoustic wave detection device disclosed in this embodiment, a ring receiving array is provided, and multiple acoustic wave receivers are arranged in the ring receiving array in the form of equal central angles.

[0086] Specifically, the remote transmission module, transmitting line, transmitting acoustic system, sound insulation body, and receiving acoustic system are all housed inside the fiber optic sensing acoustic wave detection device. The specific connection methods between the modules in this fiber optic sensing acoustic wave detection device can be communication connections, electrical connections, or hard connections, etc., and can also include both communication and hard connections, or electrical and hard connections simultaneously, depending on actual needs.

[0087] The remote transmission module is used for bidirectional communication with external devices or systems. It can be used to receive control commands (such as transmission commands) sent by external devices or systems and forward the control commands to the corresponding transmission system.

[0088] According to the launch command, the launch line provides a launch drive signal to the launch acoustic system to drive the launch acoustic system to excite sound wave signals;

[0089] The transmitting acoustic system is used to amplify the transmitting drive signal provided by the transmitting line and perform the operation of exciting acoustic waves (for example, exciting the acoustic transducer to vibrate, thereby exciting the acoustic signal); the sound insulation body is used to block the direct wave excited by the transmitting acoustic system and propagating along the outer shell of the fiber optic sensing acoustic wave detection device; that is, the sound insulation body can be used to block the acoustic signal generated by the transmitting acoustic system from propagating along the outer shell of the fiber optic sensing acoustic wave detection device in the form of a direct wave.

[0090] An external device or system can send a laser pulse signal to the fiber optic sensing acoustic detection device, while the receiving acoustic system can be used to conduct the externally emitted laser pulse signal and to sensitize weak acoustic signals from the outside (e.g., wellbore and / or formation) to cause disturbance in the optical fiber located inside the receiving acoustic system, thereby coupling the mechanical vibration caused by the weak acoustic signal into the reflected light signal of the laser pulse signal.

[0091] The fiber optic sensing acoustic wave detection device provided in this embodiment can achieve circumferential detection under the condition of receiver miniaturization by using a ring receiving array in a fiber optic sensing acoustic wave detector based on an elastic substrate that supports multi-directional detection; it does not require fiber winding and can avoid defects such as severe light attenuation and fiber breakage caused by excessively small fiber winding curvature radius.

[0092] Example 3

[0093] The embodiments of the present invention are a detailed description of the above-described fiber optic sensing acoustic wave detection device.

[0094] In some embodiments, a boost unit and a transmitting transducer are provided in the transmitting acoustic system of the above-described fiber optic sensing acoustic wave detection device; wherein:

[0095] The boost unit is used to amplify the transmission drive signal provided by the transmission line, thereby driving the transmission transducer to vibrate;

[0096] The transmitting transducer is used to convert electrical energy into mechanical energy according to the amplified transmitting drive signal, and then excite sound waves through vibration; wherein, the transmitting transducer includes:

[0097] One or more of the following: monopole emitter transducer, dipole emitter transducer, and quadrupole emitter transducer.

[0098] It is understood that the transmitting transducer may include any one or a combination of monopole transmitting transducers, dipole transmitting transducers and quadrupole transmitting transducers.

[0099] Optionally, the transmitting line of the fiber optic sensing acoustic wave detection device drives the transmitting transducer to excite monopole, dipole, or quadrupole vibrations according to a specific timing sequence provided by the instructions issued by the ground system.

[0100] In some embodiments, in the receiving acoustic system of the fiber optic sensing acoustic wave detection device described above, a plurality of fiber optic sensing acoustic wave detectors based on elastic substrates supporting multi-directional detection are arranged at equal intervals along the axis of the fiber optic sensing acoustic wave detection device body.

[0101] For example, in the receiving acoustic system, eight sets of fiber optic acoustic wave detectors supporting multi-directional detection based on elastic substrates are arranged at equal intervals along the axis of the fiber optic sensing acoustic wave detection device. Each fiber optic acoustic wave detector supporting multi-directional detection based on elastic substrates can be equipped with four acoustic wave receivers. The specific number of fiber optic acoustic wave detectors supporting multi-directional detection based on elastic substrates and the number of acoustic wave receivers set in the fiber optic sensor receiving array supporting multi-directional detection based on elastic substrates can be set according to actual needs.

[0102] In some embodiments, when the above-described fiber optic sensing acoustic wave detection device is provided with multiple fiber optic sensing acoustic wave detectors that support multi-directional detection based on elastic substrates, the gratings located inside different fiber optic sensing acoustic wave detectors that support multi-directional detection based on elastic substrates have different wavelengths.

[0103] For example, along the axis of the fiber optic sensing acoustic wave detection device, multiple sensors based on elastic substrates that support multi-directional detection are numbered as: sensor 1, sensor 2, sensor 3, etc.; then, the gratings set inside each sensor, such as sensor 1, sensor 2, and sensor 3, have different wavelengths.

[0104] It should be noted that for acoustic receivers located in the same fiber optic sensing acoustic detector supporting multi-directional detection based on an elastic substrate, the gratings inside different acoustic receivers can have the same wavelength or different wavelengths; for example, for acoustic receiver No. 1 in sensor No. 1 and acoustic receiver No. 2 in sensor No. 1, the gratings set on their internal optical fibers can have the same wavelength or different wavelengths. However, for acoustic receivers located in different sets of receiver arrays, the gratings inside different acoustic receivers have different wavelengths; for example, for acoustic receiver No. 1 in sensor No. 1 and acoustic receiver No. 1 in sensor No. 2, the gratings set on their internal optical fibers have different wavelengths.

[0105] In some embodiments, the reflected light signal of the laser pulse signal includes a first reflected light signal without acoustic wave disturbance and a second reflected light signal coupled with acoustic wave vibration.

[0106] In this embodiment, a Bragg grating arranged in an equal central angle manner is used in a fiber optic sensing acoustic detector based on an elastic substrate to support multi-directional detection, and the elastic substrate is used to enhance the sensitivity, thereby realizing circumferential detection under the condition of receiver miniaturization, without the need for fiber winding, and avoiding defects such as severe light attenuation and fiber breakage caused by excessively small curvature radius of fiber winding.

[0107] Example 4

[0108] Based on the above embodiments, this embodiment provides a specific application example.

[0109] In this embodiment, the application of the fiber optic sensing acoustic wave detection device in well logging is used as an example for illustration.

[0110] Please refer to Figure 2 , Figure 2 This is a schematic diagram of another fiber optic sensing acoustic wave detection device provided in an embodiment of this disclosure.

[0111] The well logging surface system is connected to the optical modulation and demodulation module, depth module, tension module, recording module, and photoelectric composite cable. The well logging surface system provides time for the optical modulation and demodulation module and the remote transmission module. The depth module is used to record the cumulative length of the photoelectric composite cable passing through the photoelectric encoder to reflect the depth of the fiber optic well logging device.

[0112] The winch system lowers the fiber optic composite cable, placing the distributed fiber optic logging downhole device at a specific location within the well to begin detection. During the measurement process, the downhole device can be raised, lowered, or suspended. The fiber optic composite cable consists of a cable and single-mode optical fiber, which can be one or more strands.

[0113] The ground system can communicate with the fiber optic sensing acoustic detection device through the remote transmission module. After a specific time interval, the remote transmission module synchronizes with the ground system to provide time to the transmission line. The remote transmission module forwards the transmission command issued by the ground system to the transmission line. The transmission line drives the transmitting transducer to excite monopole, dipole, or quadrupole vibrations according to the specific timing provided by the command issued by the ground system.

[0114] The optical modulation and demodulation module emits laser pulses of a specific frequency according to the specific timing of the ground system command, demodulates and records the reflected light signal of the Bragg grating. The vibration generated by the transmitting transducer in the wellbore acts on the wellbore fluid and is transmitted to the formation. After being emitted through the geological anomaly, it returns to the wellbore. The reflected wave acts on the receiving sound systems at both ends of the transmitting sound system (the receiving sound system can be set above the transmitting sound system, below the transmitting sound system, or two receiving sound systems can be set at both the upper and lower parts of the transmitting sound system at the same time), causing strain in the position of the Bragg grating and causing disturbance in the reflected light signal.

[0115] The fiber optic sensing acoustic wave detection device can be connected in the following order from near the wellhead to the far end: connector, remote transmission module, azimuth connector, transmitting line, transmitting acoustic system, sound insulation body, receiving acoustic system, and a perforated metal bracket with 4 or 8 elastic base plates arranged at equal central angles along the bracket's axis. The connector is used to connect the optoelectronic composite cable to the fiber optic sensing acoustic wave detection device.

[0116] In this fiber optic acoustic wave detector based on a flexible substrate supporting multi-directional detection, the upper and lower ends of the flexible substrate are limited and fixed to a metal bracket using multiple high-temperature resistant, low-density non-metallic materials. The grating is connected to the single-mode fiber of the optoelectronic composite cable. Eight fiber optic acoustic wave detectors based on a flexible substrate supporting multi-directional detection are distributed axially in the receiving acoustic system, with a distance of 0.5 feet between adjacent detectors. The metal bracket is used to fix the flexible substrate in the detector. A connecting component made of high-temperature, high-pressure resistant PEEK material is used between the metal brackets of adjacent detectors. This connecting component both fixes the detector and blocks sound waves from propagating along the frame of the receiving acoustic system. Different groups of receivers in the same axial direction are connected by single-mode fiber. In the same fiber optic acoustic wave detector based on a flexible substrate that supports multi-directional detection, the grating wavelengths in different directions are the same. However, in different fiber optic acoustic wave detectors based on a flexible substrate that support multi-directional detection, the grating wavelengths of the receivers are slightly different. For example, each receiving array is numbered from bottom to top according to 1-8, the midpoint of the grating is located in the center of the flexible substrate, and each grating segment is set to the same length.

[0117] It should be noted that the center wavelength of the reflected light from a uniform periodic Bragg grating follows the grating equation:

[0118] λ B =2n eff Λ

[0119] Where, n eff Λ represents the effective refractive index of the optical fiber, and Λ represents the grating period.

[0120] The specific principle of using this fiber optic sensing acoustic wave detection device for well logging is as follows: First, without excitation of the transmitting module, the laser emitted from the ground is received by the well logging system, and the wavelength change of the reflected wave from the j-th grating at the i-th position relative to the incident wave is analyzed as Δλ. B1 (i, j):

[0121] Δλ B1 (i, j) = (α + ξ)λ B (i)ΔT(i,j)+(1-p ∈ )λ B Δε(i,j)

[0122] Where, Δλ B1 (i, j) represents the incident wavelength variation of receiver group j at azimuth i, Δλ B(i) represents the specific wavelength laser emitted from the ground via the fiber in direction i; ΔT(i,j) represents the temperature at the location of receiver group j in direction i; Δε represents the strain change; α and ξ are the thermal expansion coefficient and thermo-optic coefficient of the fiber, respectively, both being material-related constants; p ∈ is the effective elastic-optic coefficient of the optical fiber.

[0123] Since the wavelength offset of a Bragg grating is affected by both temperature and strain, temperature compensation is required to accurately measure the strain at the grating's location. Specifically, two methods can be used in the excitation and acquisition timing design: 1. First, the transmitting acoustic system is not excited, and the receiving acoustic system acquires data once. In this case, the wavelength offset of the Bragg grating is only affected by temperature. Then, with the transmitting acoustic system excited, the receiving acoustic system acquires data again. The latter acquisition is differentially processed with the former to eliminate the temperature effect; 2. The transmitting acoustic system is excited once with a positive pulse, and then excited once with a negative pulse. The former and the latter differentially cancel out the temperature term and can superimpose the strain term, eliminating some random noise and improving the signal-to-noise ratio.

[0124] The temperature ΔT of each receiver group is calculated using the formula and used for subsequent temperature compensation. Then, the transmitting module is excited, and at the same time, a laser of a specific wavelength is emitted from the ground. The reflected wave is received, and the wavelength change of the reflected wave relative to the incident wave is analyzed. After eliminating the influence of the well temperature at the measurement point on the wavelength change of the incident wave through temperature compensation, the strain of the optical fiber can be obtained.

[0125] The optical modulation and demodulation module and the acoustic wave transmission control module of the ground system are synchronized. The acoustic wave transmission control module excites the downhole acoustic transducer to emit acoustic signals, while the optical modulation and demodulation module emits laser pulses of a specific wavelength and continuously records the reflected light signals. The wavelength changes of the reflected light signals are analyzed, and temperature compensation is introduced for each transmitter. The strain values ​​of each receiver group at different azimuths are output and displayed.

[0126] It should be noted that when measurements are required in n directions, the optoelectronic composite cable needs at least n single-mode optical fibers. The ground requires n sets of pulsed laser emitters, optical demodulators, couplers, and beam splitters. Each single-mode optical fiber can connect to eight acoustic receivers located in the same direction within a fiber optic sensing acoustic detector based on an elastic substrate supporting multi-directional detection. (For example, in a fiber optic sensing acoustic detector with six acoustic receivers, the directions can be understood as: 2 o'clock, 4 o'clock, 6 o'clock, 8 o'clock, 10 o'clock, and 12 o'clock; in a detector with four acoustic receivers, the directions can be understood as: 3 o'clock, 6 o'clock, 9 o'clock, and 12 o'clock.)

[0127] For a better understanding of the technical solution of this application, please refer to... Figure 5 and Figure 6 .in, Figure 5This is a side cross-sectional view of an optical fiber sensing acoustic wave detection device provided in an embodiment of this disclosure. Figure 6 This is a cross-sectional view of an optical fiber sensing acoustic wave detection device provided in an embodiment of this disclosure.

[0128] Example 5

[0129] Based on the above embodiments, this embodiment provides an optical fiber sensing acoustic wave detection system. The optical fiber sensing acoustic wave detection system provided in this embodiment includes:

[0130] The fiber optic sensing acoustic wave detection device described above;

[0131] The control system, connected to the remote transmission module of the fiber optic acoustic wave detection device, is used to control the transmitting acoustic system of the fiber optic acoustic wave detection device to perform the operation of exciting acoustic waves, and to perform the operation of transmitting laser pulses to the fiber optic acoustic wave detection device, and to generate acoustic logging data based on the reflected light signal of the laser pulse signal collected by the fiber optic acoustic wave detection device; wherein, the reflected light signal includes a first reflected light signal without acoustic wave disturbance and a second reflected light signal coupled with acoustic wave vibration.

[0132] The specific connection method between this fiber optic sensing acoustic wave detection device and the control system can be a communication connection, an electrical connection, or a hard connection, etc. Of course, it can also include both communication connections and hard connections, or electrical connections and hard connections at the same time. The specific method can be selected according to actual needs.

[0133] It should be noted that the control system of this fiber optic sensing acoustic wave detection system can be a ground system; for example, a well logging ground system.

[0134] The control system can be located on the ground. It sends laser emission commands and simultaneously sends emission commands to the downhole acoustic system according to a specific timing sequence. The emitted laser is reflected at the grating, propagates along the optical fiber towards the ground, and is sent to the ground demodulation module to acquire grating deformation information at the grating location. This data is then processed and converted into a waveform curve.

[0135] This fiber optic sensing acoustic wave detection system can generate acoustic logging data based on the first reflected light signal without acoustic disturbance and the second reflected light signal under acoustic disturbance, collected by the fiber optic sensing acoustic wave detection device. The specific implementation steps can be found in the description of the foregoing embodiments, and will not be repeated here.

[0136] Example 6

[0137] Based on the above embodiments, this embodiment provides a fiber optic sensing acoustic wave detection method based on the fiber optic sensing acoustic wave detection system described above.

[0138] Please refer to Figure 3 , Figure 3 A flowchart illustrating a fiber optic sensing acoustic wave detection method provided in this embodiment. The fiber optic sensing acoustic wave detection method provided in this embodiment includes the following steps:

[0139] Step 310: Determine the current well depth at the location of the fiber optic sensing acoustic detection device in the well to be tested.

[0140] Optionally, the movable end of the optoelectronic composite cable is mechanically and electrically connected to the downhole equipment using a screwdriver, while the fixed end is connected to the surface system and the optical modulation / demodulation module via slip rings. The cable core of the optoelectronic composite cable is connected to the surface system, and the optical fiber is connected to the optical modulation / demodulation module. The optoelectronic composite cable is lowered using a winch system, and the fiber optic sensing acoustic wave detection device is placed at a specific location within the well to begin detection. During the measurement process, the fiber optic sensing acoustic wave detection device can be raised, lowered, or suspended. The current well depth of the fiber optic sensing acoustic wave detection device within the well to be measured can be determined based on the length of the lowered optoelectronic composite cable.

[0141] Step 320: Emit a laser pulse to the fiber optic sensing acoustic wave detection device and acquire the first reflected light signal reflected by each acoustic wave receiver in the fiber optic sensing acoustic wave detection device.

[0142] Optionally, communication with the ground system is achieved via a remote transmission module, and time is synchronized with the ground system at specific time intervals to provide time to the transmission line. The measurement process can be divided into two stages:

[0143] Phase 1: The laser pulse is transmitted downhole through the optical modulation and demodulation module, and the optical signal reflected by the grating in each acoustic receiver is demodulated and recorded. At this time, the transmission line is not working.

[0144] Step 330: Send a transmission command to the fiber optic sensing acoustic wave detection device to control the transmission line to provide a transmission drive signal to the transmitting acoustic system, so that the transmitting acoustic system amplifies the transmission drive signal provided by the transmission line and performs the excitation of acoustic waves, and acquires the second reflected light signal coupled with acoustic wave vibration reflected by each acoustic wave receiver in the fiber optic sensing acoustic wave detection device under acoustic wave disturbance.

[0145] The second stage: The remote transmission module forwards the transmission command from the ground system to the transmitting acoustic system. The transmitting line drives the transmitting transducer to generate monopole, dipole, or quadrupole vibrations according to the specific timing provided by the ground system (which can be a relatively large time interval, with at least one excitation at each measurement location, and the time interval between two excitations can be 1 minute, 2 minutes, etc.). The vibration is transmitted to the formation through the wellbore fluid, emitted through the geological anomaly, and returns to the wellbore. The reflected wave acts on the receiving acoustic systems at both ends of the transmitting acoustic system, causing deformation of the gratings in the receiving acoustic systems. The optical modulation and demodulation module transmits laser pulses of a specific frequency according to the specific timing of the command sent from the ground system to the remote transmission module, demodulates, and records the optical signals reflected from the gratings in each acoustic receiver.

[0146] Step 340: Based on the first and second reflected light signals reflected by each receiving acoustic system, determine the strain of the optical fiber in each acoustic receiver at the current well depth using a preset strain determination method.

[0147] The methods for determining the pre-defined strain can include time-domain positioning and frequency-domain analysis methods.

[0148] Furthermore, time-domain positioning and frequency-domain analysis methods can be used to obtain the strain of the optical fiber at one or more depth locations in the receiving acoustic system.

[0149] Step 350: Based on the strain of the optical fiber in each acoustic receiver, generate waveform curves for each acoustic receiver at the corresponding azimuth, and use the waveform curves of all azimuths as acoustic logging data of the well to be logged at the current well depth.

[0150] Optionally, steps 310 to 340 are repeated at different depths within the wellbore. The optical signal under no excitation conditions can acquire well temperature information. The optical signal collected when the acoustic system is working, combined with the above-mentioned well temperature information, can eliminate the influence of temperature and thus obtain acoustic logging data.

[0151] Among them, the waveform curve is the curve of amplitude changing with time, and the origin of the coordinate system can be regarded as the excitation start time.

[0152] In some embodiments, the fiber optic sensing acoustic wave detection device is connected via an optical-electric composite cable, and the method further includes:

[0153] By controlling the optical fiber composite cable to perform lifting or lowering operations, the position of the optical fiber sensing acoustic wave detection device in the well to be tested can be controlled.

[0154] Specifically, by lifting or lowering the optical fiber composite cable, the position of the optical fiber sensing acoustic wave detection device in the well to be tested can be changed. After reaching the predetermined position, the optical fiber sensing acoustic wave detection device can be suspended at the current position.

[0155] Example 7

[0156] Based on the above embodiments, this embodiment provides a computer device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method described in the above embodiments.

[0157] In some embodiments of this example, a computer-readable storage medium is provided, on which a computer program is stored, which, when executed by a processor, implements the steps of the method described in the above embodiments.

[0158] In some embodiments of this example, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps of the method described in the above embodiments.

[0159] The processor may include, but is not limited to, one or more processors or microprocessors. Each processor may be implemented as an Application Specific Integrated Circuit (ASIC), Digital Signal Processor (DSP), Digital Signal Processing Device (DSPD), Programmable Logic Device (PLD), Field Programmable Gate Array (FPGA), controller, microcontroller, microprocessor, or other electronic component, for executing the methods in the above embodiments.

[0160] Computer-readable storage media can be implemented by any type of volatile or non-volatile storage device or a combination thereof. Computer-readable storage media may include, but are not limited to, random access memory (RAM), read-only memory (ROM), flash memory, EPROM memory, EEPROM memory, registers, computer storage media (e.g., hard disk, floppy disk, solid-state drive, removable disk, CD-ROM, DVD-ROM, Blu-ray disc, etc.).

[0161] Computer-readable storage media may also store at least one computer-executable program, such as computer-readable instructions. Computer-readable storage media include, but are not limited to, volatile memory and / or non-volatile memory. Volatile memory may include, for example, random access memory (RAM) and / or cache memory. Computer-readable storage media may include, for example, read-only memory (ROM), hard disk, flash memory, etc. For example, a non-transitory computer-readable storage medium may be connected to a computing device such as a computer, and then, when the computing device executes the computer-readable instructions stored on the computer-readable storage medium, the various methods described above can be performed.

[0162] In addition, the computer device may include (but is not limited to) a data bus, an input / output (I / O) bus, a display, and input / output devices (e.g., keyboard, mouse, speakers, etc.).

[0163] The processor can communicate with external devices via the I / O bus through wired or wireless networks.

[0164] In one embodiment, the at least one computer-executable instruction may also be compiled into or comprise a software product / computer program product, wherein one or more computer-executable instructions are executed by a processor to perform the steps of the various functions and / or methods in the embodiments described herein.

[0165] It should be understood that the terms "mechanism," "device," "component," etc., used in this application are merely one method of distinguishing different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they can be replaced by other expressions.

[0166] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention. In practical applications, the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification, and various changes can be made to them in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A fiber optic sensing acoustic wave detector based on an elastic substrate supporting multi-directional detection, characterized in that, include: The main body of the fiber optic sensing acoustic wave detector; Multiple acoustic wave receivers are arranged inside the fiber optic acoustic wave detector body at equal central angles, and each acoustic wave receiver contains a flexible substrate and an optical fiber; wherein: The elastic substrate is used for sensitization, and a through hole is provided between the center position of the top surface of the elastic substrate and the center position of the bottom surface of the elastic substrate. The optical fiber is fixed on the elastic substrate and is used to conduct laser pulse signals. The optical fiber passes through the through hole and extends into the interior of the elastic substrate. A grating is etched at the position of the optical fiber inside the elastic substrate. The grating is used to reflect the laser pulse signals.

2. The fiber optic sensing acoustic detector based on an elastic substrate supporting multi-directional detection according to claim 1, characterized in that, The optical fiber is a single-mode optical fiber.

3. A fiber optic sensing acoustic wave detection device, characterized in that, include: The main body of the fiber optic sensing acoustic wave detection device; The remote transmission module is located inside the fiber optic sensing acoustic wave detection device and is used to receive external transmission commands. The transmission commands are used to control the transmission line to provide transmission drive signals to the transmitting acoustic system. The transmitting line is located inside the fiber optic sensing acoustic wave detection device and connected to the remote transmission module, and is used to provide a transmission drive signal to the transmitting acoustic system in response to the transmission command. The transmitting acoustic system is located inside the fiber optic sensing acoustic wave detection device and connected to the transmitting line. It is used to amplify the transmitting drive signal provided by the transmitting line and perform the operation of exciting acoustic waves. A sound insulation body is disposed between the transmitting sound system and the receiving sound system to block the direct wave excited by the transmitting sound system and propagating along the outer shell of the fiber optic sensing acoustic wave detection device. A receiving acoustic system, disposed inside the main body of the fiber optic sensing acoustic wave detection device, is used to conduct externally emitted laser pulse signals and to enhance the sensitivity of weak acoustic signals from the outside to cause disturbance in the optical fiber located inside the receiving acoustic system, thereby coupling the mechanical vibration caused by the weak acoustic signal into the reflected light signal of the laser pulse signal; wherein, the receiving acoustic system is provided with the fiber optic sensing acoustic wave detector based on an elastic substrate supporting multi-directional detection as described in claim 1 or 2.

4. The apparatus according to claim 3, characterized in that, The transmitting acoustic system includes a boost unit and a transmitting transducer; wherein: The boost unit is used to amplify the transmission drive signal provided by the transmission line, thereby driving the transmission transducer to vibrate; The transmitting transducer is used to convert electrical energy into mechanical energy according to the amplified transmitting drive signal, and then excite sound waves through vibration; wherein, the transmitting transducer includes: One or more of the following: monopole emitter transducer, dipole emitter transducer, and quadrupole emitter transducer.

5. The apparatus according to claim 3, characterized in that, In the receiving acoustic system, multiple fiber optic sensing acoustic detectors based on elastic substrates supporting multi-directional detection are arranged at equal intervals along the axis of the fiber optic sensing acoustic wave detection device body.

6. The apparatus according to claim 3, characterized in that, In the case of multiple fiber optic acoustic wave detectors based on elastic substrates supporting multi-directional detection, the gratings located inside different fiber optic acoustic wave detectors based on elastic substrates supporting multi-directional detection have different wavelengths.

7. The apparatus according to claim 3, characterized in that, The reflected light signal includes a first reflected light signal without acoustic wave disturbance and a second reflected light signal coupled with acoustic wave vibration.

8. A fiber optic sensing acoustic wave detection system, characterized in that, include: The fiber optic sensing acoustic wave detection device according to any one of claims 3 to 7; The control system, connected to the remote transmission module of the fiber optic acoustic wave detection device, is used to control the transmitting acoustic system of the fiber optic acoustic wave detection device to perform the operation of exciting acoustic waves, and to perform the operation of transmitting laser pulses to the fiber optic acoustic wave detection device, and to generate acoustic logging data based on the reflected light signal of the laser pulse signal collected by the fiber optic acoustic wave detection device; wherein, the reflected light signal includes a first reflected light signal without acoustic wave disturbance and a second reflected light signal coupled with acoustic wave vibration.

9. A fiber optic sensing method for acoustic wave detection, characterized in that, Based on the system implementation of claim 8, the method includes: Determine the current well depth at which the fiber optic sensing acoustic detection device is located in the well to be tested; A laser pulse is emitted to the fiber optic sensing acoustic wave detection device, and the first reflected light signal reflected by each fiber optic sensing acoustic wave detector based on an elastic substrate supporting multi-directional detection is acquired. Send a transmission command to the fiber optic sensing acoustic wave detection device to control the transmission line to provide a transmission drive signal to the transmission acoustic system, so that the transmission acoustic system amplifies the transmission drive signal provided by the transmission line and performs the excitation of acoustic waves, and acquires the second reflected light signal coupled with acoustic wave vibration reflected by each fiber optic sensing acoustic wave detector based on an elastic substrate supporting multi-directional detection in the fiber optic sensing acoustic wave detection device under acoustic wave disturbance. Based on the first and second reflected light signals from each receiving acoustic system, the strain of the optical fiber in each fiber optic sensing acoustic detector supporting multi-directional detection based on an elastic substrate is determined using a preset strain determination method at the current well depth. Based on the strain of the optical fiber in each fiber optic acoustic detector that supports multi-directional detection on an elastic substrate, waveform curves for each corresponding azimuth of the fiber optic acoustic detector that supports multi-directional detection on an elastic substrate are plotted, and the waveform curves for all azimuths are used as acoustic logging data for the well to be logged at the current well depth.

10. The method according to claim 9, characterized in that, The method further includes connecting the fiber optic sensing acoustic wave detection device via an optical-electric composite cable: By controlling the optical fiber composite cable to perform lifting or lowering operations, the position of the optical fiber sensing acoustic wave detection device in the well to be tested can be controlled.

11. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method of claim 9 or 10.

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