Acoustic scanning logging device and measurement method based on fiber optic acoustic sensor

Abstract

This invention provides a downhole acoustic scanning logging device based on a fiber optic acoustic sensor, replacing the monopole, dipole, or multipole piezoelectric crystal acoustic receiving transducer in conventional acoustic scanning logging devices. This instrument's downhole receiving sensor requires no electronic components, solving the problem that downhole receiving sensors and their associated amplifiers, analog-to-digital converters, data storage devices, and data transmission modules cannot operate for extended periods at high temperatures. Through an armored optoelectronic composite cable connected to the fiber optic acoustic scanning logging device, the backscattered Rayleigh light signal from the fiber optic acoustic sensor can be transmitted at high speed to a surface multi-channel DAS modulator / demodulator, overcoming the bottleneck problem of high-speed upward transmission of large amounts of data signals acquired by downhole acoustic scanning logging devices. This invention can significantly reduce the instrument manufacturing cost for downhole acoustic scanning data and achieve high-efficiency acquisition of ultra-high density or extremely high spatial resolution downhole acoustic scanning data.

Description

Technical Field

[0001] This invention relates to the field of geophysical logging technology, and in particular to an acoustic scanning logging device and its measurement method based on a fiber optic acoustic sensor. Background Technology

[0002] When sound waves propagate in different media, their acoustic properties, such as velocity, amplitude, and frequency, vary. Sonic logging is a logging method that utilizes these acoustic properties of rocks to study the geological profile of the well and assess the quality of cementing.

[0003] Sonic logging is a well logging method that determines the properties of rock formations by studying the propagation velocity of sound waves within the formation during borehole drilling. A typical array sonic velocity logging tool consists of a set of sonic generators (T) and two or more receivers (R0, R1). The recorded parameter is the time difference (Δt) between the arrival of the sound wave at the two receivers, i.e., the time required for the sound wave to propagate through the rock formation between the two receivers. In essence, it is a time measurement system. The speed at which sound waves propagate through the rock formation is determined by factors such as the rock's elasticity, density, and the properties of the fluids within the pores.

[0004] A controlled acoustic wave source is placed in the well. The sound waves emitted by the source cause vibrations in surrounding particles, generating body waves (P-waves and S-waves) in the formation and induced interface waves (pseudo-Rayleigh waves and Stoneley waves) at the wellbore-drilling fluid interface. These waves, acting as carriers of formation information, are received by a downhole receiver and recorded at the surface; this is acoustic logging. The receiver and sound source are collectively called the acoustic system. Based on the arrangement and size of the acoustic system, acoustic logging tools can be classified as compensated logging tools (BHC), long-spacing acoustic logging tools (LSS), and array acoustic logging tools. The propagation of sound waves within the formation is affected by changes in the composition, structure, and fluid composition of the formation rocks; the wave velocity, amplitude, and even frequency can vary. Acoustic logging is divided into velocity logging and amplitude logging. Logging that only records changes in sound wave velocity is called velocity logging (AC), while logging that records changes in sound amplitude is called amplitude logging. In acoustic velocity logging, short-source acoustic systems only record the propagation time difference of longitudinal waves (i.e., the first wave), while long-source acoustic systems can record the propagation time differences of various wave trains such as longitudinal waves, transverse waves, pseudo Rayleigh waves, and Stoneley waves. Therefore, it is also called full-wave acoustic logging. Array acoustic instruments, due to their complex acoustic systems, can record longitudinal wave velocity, full-wave train velocity, and acoustic amplitude.

[0005] Sonic logging measures the acoustic velocity of formations. Formation acoustic velocity is related to factors such as lithology, porosity, and pore fluid properties. Based on the propagation speed of acoustic waves in the formation, formation porosity, lithology, and pore fluid properties can be determined. Sonic logging can be used to classify lithology, determine the porosity of oil and gas reservoirs, and delineate gas layers. It can also provide velocity data necessary for seismic exploration.

[0006] Sonic velocity logging, or sonic logging for short, records the time required for a sound wave to travel through 1 meter of rock, measuring the time difference Δt (the reciprocal of the longitudinal wave velocity) of the formation's slip wave. It is primarily used to calculate formation porosity, analyze formation lithology, and identify gas-bearing reservoirs.

[0007] Compared to electromagnetic and nuclear logging instruments, acoustic instruments have a greater impact on well measurements when deployed. Acoustic scanning logging instruments are entirely different from other instruments; their design, materials, and components are specially designed to simulate their effects. This allows for accurate prediction of the instrument's influence in isotropic and homogeneous formations, enabling real-time correction at the well site.

[0008] The sonic scanning logging instrument has 13 axial receiver points on a 6-foot receiver array, with 8 circumferentially distributed receivers at each point, totaling 104 sensors. Three monopole transmitters can acquire long-spacing and short-spacing data for wellbore compensation at different exploration depths. Two orthogonal dipole transmitters can generate flexural waves to characterize the shear wave slowness of slow and anisotropic formations.

[0009] The transmitter-receiver (TR) geometry and functionality of the sonic scanning logging instrument are carefully designed to provide P-wave, S-wave, Stoneley wave, and flexural wave slowness measurements at various radial depths. The logging speed in these modes is 1800 feet per hour (549 meters per hour). For the typical case where formation P-wave and S-wave velocities increase with distance from the wellbore, the depth of detection is increased by extending the TR distance. The sonic scanning logging instrument combines this long source-to-source distance method with the wellbore-compensated short source-to-source distance method, and also incorporates circumferentially distributed receivers. The instrument has 13 axial receiver points on a 6-foot (1.8-meter) receiver array. Each receiver point has eight receivers placed around the instrument at 45° intervals, for a total of 104 sensors on the instrument. There is one monopole transmitter at each end of the receiver array, and another monopole transmitter and two orthogonally oriented dipole transmitters are located further down the instrument.

[0010] The three monopole transmitters of the sonic scanning logging instrument can generate stronger pressure pulses. These transmitters produce clear P-waves and S-waves, low-frequency Stoneley waves, and high-frequency energy required for cementing evaluation. The two dipole transmitters are vibrating devices consisting of electromagnetic motors mounted on a cylinder suspended from the instrument. This mechanism generates a high-voltage dipole signal without causing vibration of the instrument housing. The source can be driven in two modes: a conventional dipole source in pulse mode produces a deep "click" signal, while the sonic scanning logging instrument uses a sweep frequency to generate a linear frequency modulated (LFM) pulse signal. Compared to narrowband dipole sources, the LFM pulse mode maintains each frequency for a longer time, delivering more dipole energy to the formation. The two dipole sources are orthogonally oriented. One vibrates along the instrument's reference axis, and the other at 90° to the reference axis; these devices generate strong flexural waveforms. These flexural waveforms propagate up and down the wellbore, reaching different formation depths depending on the frequency. The two dipole sources are orthogonally oriented. One vibrates along the instrument's reference axis, while the other is at a 90° angle to the reference axis. These devices generate strong flexural waveforms. These flexural waveforms propagate up and down the wellbore, reaching different depths in the formation depending on their frequency.

[0011] With the study of the theory of sound wave propagation in wells, it is known that the sound pulses generated by the transmitter in the wellbore propagate through the mud and formation to the receiver. Recording these sound waves, which carry a wealth of formation information, and processing them digitally, yields waveform information and provides rock mechanical properties such as bulk modulus, Poisson's ratio, Young's modulus, yield strength, shear modulus, and compressive strength. This allows for research into formation elastic characteristics, fracture pressure, formation permeability, fractures, and hydrocarbon identification, which will benefit the expansion of the application of sound waves in petroleum exploration.

[0012] The propagation velocity, amplitude attenuation, principal frequency value, and waveform envelope of various component waves are all closely related to the reservoir and its properties. These parameters can be widely used for oil and gas evaluation and drilling and production parameter selection in heterogeneous and complex reservoirs. Acoustic scanning logging outputs information including P-wave and S-wave DT, full waveform, and cement bond quality waveform. It includes cross-dipole and monopole measurement results at various distances. In addition to axial and azimuth measurements, the instrument can also perform radial measurements, detecting the slowness of formations near the wellbore and far-field slowness at a depth 2-3 times the wellbore diameter. This new acoustic scanning logging platform can provide wellbore-compensated monopole, cross-dipole, and cement bond quality measurements at both long and short distances. The measurement results can be used to evaluate the drilling environment and reservoir information. This information is helpful in decisions regarding improving recovery rate and maximizing production.

[0013] The working modes of the orthogonal dipole acoustic logging tool include longitudinal and transverse wave mode, Stoneley wave mode, dipole transverse wave mode, and orthogonal dipole mode.

[0014] P-wave and S-wave methods: monopole, high-frequency sound source excitation, measuring full-wave information. Used to calculate porosity, identify lithology, identify gas layers, and calculate elastic mechanical parameters.

[0015] Stoneley wave method: A monopole, low-frequency sound source excitation, measures Stoneley wave information. Used to identify cracks and calculate permeability.

[0016] Dipole transverse wave mode: A dipole sound source emits sound, which is excited at a low frequency, and the transverse wave time difference is measured. It is used to calculate porosity, determine lithology, identify fractures, and evaluate formation anisotropy.

[0017] Orthogonal dipole method: Orthogonal dipole sound sources emit sound alternately, and the orthogonal dipole waveform is measured. It is used to calculate the slowness of P-waves and S-waves, and to evaluate formation permeability, anisotropy, and heterogeneity.

[0018] Current downhole acoustic logging instruments utilize monopole, dipole, or multipole piezoelectric crystal transducers to receive P-waves, S-waves, and low-frequency Stoneley wave signals from the formation surrounding the wellbore. These monopole, dipole, or multipole piezoelectric crystal transducers, along with their associated amplifiers, analog-to-digital converters, data storage devices, and downhole data transmission modules, cannot operate for extended periods in high-temperature environments (deep wells). Furthermore, since downhole acoustic logging instruments are currently electronic, their downhole data transmission modules cannot yet overcome the bottleneck of high-speed, real-time transmission of large amounts of data from the well to the control computer in the logging truck at the wellhead. Summary of the Invention

[0019] The purpose of this invention is to provide an acoustic scanning logging device based on a fiber optic acoustic sensor. This device primarily uses a fiber optic acoustic sensor installed between an upper monopole acoustic transmitter and a lower monopole acoustic transmitter within the downhole acoustic scanning logging device. This sensor replaces the currently widely used monopole, dipole, or multipole piezoelectric crystal acoustic receiver transducers, receiving longitudinal waves, transverse waves, and low-frequency Stoneley wave signals from the formation surrounding the wellbore, thereby achieving the purpose of downhole fiber optic acoustic scanning logging.

[0020] The technical solution of the present invention:

[0021] The acoustic scanning logging device based on fiber optic acoustic wave sensor includes an acoustic scanning logging device based on fiber optic acoustic wave sensor, a high-temperature resistant photoelectric composite logging cable, a surface wellhead logging vehicle, and a surface fiber optic acoustic wave sensor modulation and demodulation instrument.

[0022] The aforementioned acoustic wave scanning logging device based on fiber optic acoustic wave sensor includes a high-temperature resistant fiber optic acoustic wave sensor as an acoustic wave signal receiving unit in the well; three monopole acoustic wave transmitters, two dipole acoustic wave transmitters, an electronic short circuit for the acoustic wave transmitters, a sound insulation body, and a fiber optic gyroscope; the surface wellhead logging vehicle is connected to the acoustic wave scanning logging device based on the fiber optic acoustic wave sensor in the well via an armored photoelectric composite logging cable.

[0023] The three monopole acoustic transmitters can acquire long-spacing and short-spacing data for wellbore compensation at different detection depths.

[0024] The two orthogonal dipole acoustic wave emitters can generate flexural waves to describe the transverse wave slowness of slow and anisotropic formations.

[0025] The surface wellhead logging vehicle controls the lowering and raising of the acoustic scanning logging device of the fiber optic acoustic wave sensor in the well through the photoelectric composite logging cable, and provides power to the acoustic scanning logging device of the fiber optic acoustic wave sensor in the well. The acoustic wave transmitter is electronically short-circuited to drive the monopole acoustic wave transmitter and the dipole acoustic wave transmitter to continuously and repeatedly transmit acoustic wave signals during operation.

[0026] The ground fiber optic acoustic wave sensor modulation and demodulation instrument installed at the wellhead is connected to the downhole acoustic wave scanning logging device via an armored optoelectronic composite logging cable. It is used to emit laser pulses into the fiber optic acoustic wave sensor and simultaneously collect the backscattered Rayleigh waves inside the fiber optic acoustic wave sensor.

[0027] The ground-based fiber optic acoustic modulation and demodulation instrument has a fiber optic acoustic sensor signal input port and a fiber optic gyroscope signal input port.

[0028] The acoustic sensor is either a fiber optic acoustic sensor or a fiber optic MEMS acoustic sensor. The acoustic scanning logging device contains a 2-meter-long fiber optic acoustic receiver array with 14 axial receiving points. Each receiving point has 12 fiber optic acoustic sensors placed at 30° intervals around the acoustic scanning logging device, for a total of 168 fiber optic acoustic sensors on the instrument. Since the formation P-wave and S-wave velocities increase with increasing distance from the wellbore, the acoustic scanning logging device combines this long source-spacing method with the wellbore-compensated short source-spacing method, and also adds circumferentially distributed receivers.

[0029] The fiber optic gyroscope is installed at the top of the acoustic scanning logging device in the well, and measures the azimuth, inclination and dip of the acoustic scanning logging device in real time through the photoelectric composite logging cable.

[0030] The electronic short circuit of the acoustic transmitter is placed at the upper end of the acoustic scanning logging device to drive the monopole and dipole acoustic transmitters within the device. The fiber optic gyroscope is positioned below the electronic short circuit of the acoustic transmitter.

[0031] The first monopole acoustic transmitter is positioned below the fiber optic gyroscope, followed by an array of 14 fiber optic acoustic sensors. Below the 2-meter-long fiber optic acoustic sensor array, a second monopole acoustic transmitter is positioned.

[0032] Below the second monopole acoustic wave transmitter, a set of sound insulation bodies is installed to block or prevent the volume wave energy of the dipole acoustic wave transmitter and the third monopole acoustic wave transmitter below the sound insulation body from being directly coupled to the fiber optic acoustic wave sensor array above the sound insulation body.

[0033] Below the sound insulation body, two mutually orthogonal dipole acoustic wave emitters and a third monopole acoustic wave emitter are sequentially installed. The two dipole acoustic wave emitters are orthogonally oriented. One vibrates along a reference axis parallel to the extension direction of the acoustic scanning logging device, while the other is at 90° to the reference axis. These devices generate a strong flexural waveform. The flexural waveform propagates up and down along the wellbore, and simultaneously reaches different formation depths depending on the frequency.

[0034] The first, second, and third monopole acoustic transmitters at the top are sequentially excited, and the fiber optic acoustic sensors on the fiber optic acoustic receiver array collect acoustic signals from different source distances from the formations surrounding the wellbore.

[0035] Subsequently, two mutually orthogonal dipole acoustic wave transmitters are excited, and the fiber optic acoustic wave sensor on the fiber optic acoustic wave receiver array collects dipole acoustic wave signals from the formation surrounding the wellbore.

[0036] The measurement method of the acoustic scanning logging device based on the fiber optic acoustic sensor is characterized by comprising the following steps:

[0037] S1: Connect the armored high-temperature resistant photoelectric composite logging cable on the surface wellhead logging truck winch to the in-well acoustic scanning logging device;

[0038] S2: The acoustic scanning logging device in the well is lowered to the bottom of the well using the armored high-temperature resistant photoelectric composite logging cable on the winch of the surface wellhead logging truck.

[0039] S3: The downhole acoustic scanning logging device is slowly lifted upwards by the armored high-temperature resistant photoelectric composite logging cable on the wellhead logging truck winch and the acoustic transmitter inside the downhole acoustic scanning logging device is electronically short-circuited and sent to drive the three monopole acoustic transmitters and two mutually orthogonal dipole acoustic transmitters to emit acoustic signals in sequence.

[0040] S4: Simultaneously activate the fiber optic gyroscope to measure and record in real time the azimuth, dip angle, and dip of the uplifting downhole acoustic scanning logging device along the well trajectory;

[0041] S5: Simultaneously activate the ground fiber optic acoustic sensor modulation and demodulation instrument, and transmit a high-power multi-frequency narrow pulse laser signal to the fiber optic acoustic sensor on the fiber optic acoustic receiver array in the downhole acoustic scanning logging device through the photoelectric composite logging cable, while simultaneously receiving the back Rayleigh scattering light signals from 168 fiber optic acoustic sensors.

[0042] S6: The ground fiber optic acoustic wave sensor modulation and demodulation instrument modulates and demodulates the back Rayleigh scattered light signal on each fiber optic acoustic wave sensor, and demodulates the fiber strain or strain rate data measured on each fiber optic acoustic wave sensor into the axial component acoustic wave data of the fiber optic acoustic wave sensor.

[0043] S7: First, three monopole acoustic transmitters are sequentially excited, each generating a stronger pressure pulse. These monopole transmitters produce clear P-waves and S-waves, low-frequency Stoneley waves, and the high-frequency energy required for cementing evaluation. Fiber optic acoustic sensors on the fiber optic receiver array acquire acoustic signals from the formation surrounding the wellbore, including P-waves, S-waves, and low-frequency Stoneley waves.

[0044] S8: Then, two mutually orthogonal dipole acoustic transmitters are sequentially excited. Both dipole transmitters are vibrating devices composed of electromagnetic motors, which are mounted on a cylinder suspended from the instrument. This mechanism generates a high-voltage dipole signal without causing vibration of the instrument casing. The source can be driven in two modes: a conventional dipole source in pulse mode generates a deep "click" signal, while the acoustic scanning logging instrument uses a frequency sweep to generate a linear frequency modulated pulse signal. Compared to a narrowband dipole source, the linear frequency modulated pulse mode maintains each frequency for a longer time, providing more dipole energy to the formation. A fiber optic acoustic sensor mounted below the first monopole acoustic transmitter collects three-component acoustic signals from the formation surrounding the wellbore.

[0045] S9: Based on the direct acoustic travel time from the positions of the three monopole acoustic transmitters and two mutually orthogonal dipole acoustic transmitters in the downhole acoustic scanning logging device to each acoustic detector point on the fiber optic acoustic sensor in the downhole acoustic scanning logging device, and the distance from the positions of the downhole monopole acoustic transmitters and dipole acoustic transmitters to the known detector points, calculate the average acoustic velocity from the known monopole acoustic transmitters and dipole acoustic transmitters to each known acoustic detector point;

[0046] If the data processor picks up the travel time of the sound wave directly to the longitudinal wave, what is calculated is the average velocity of the longitudinal wave.

[0047] If the travel time of the sound wave directly to the transverse wave is collected, the calculated value is the average velocity of the transverse wave.

[0048] If the travel time of a low-frequency Stoneley wave is picked up, the calculated value is the average velocity of the low-frequency Stoneley wave.

[0049] S10: By recording multiple arrayed acoustic logging curves with different acoustic transmitters and different source distances (distance between the transmitter and receiver), correlation and superposition processing can effectively suppress interference and accurately extract various information of P-waves, S-waves, and low-frequency Stoneley waves. Since the receiver spacing can be very small, it can meet the needs of thin-layer research.

[0050] S11: Use long-spacing acoustic logging curves (over 3 meters) to extract P-wave, S-wave, and Stoneley wave information from open-hole formations; use short-spacing acoustic systems (1 meter) to perform cement bond logging (CBL) in casing wells, and use acoustic systems (1.5 meters) to perform variable density logging (VDL). These two measurement results can be used to check the cement consolidation quality of casing wells.

[0051] S12: By processing and analyzing the acoustic signals of formation P-waves, S-waves, and low-frequency Stoneley waves received by a total of 168 fiber optic acoustic sensors, with 12 fiber optic acoustic sensors placed at 30° intervals around the acoustic scanning logging device at each receiving point, it is possible to understand whether there is anisotropy in the velocities of formation P-waves, S-waves, and low-frequency Stoneley waves within a 360-degree range surrounding the acoustic scanning logging device, and whether there is anisotropy in the formation's elastic or viscoelastic parameters. This enables acoustic scanning logging of the formation around the wellbore. Further processing and interpretation of the scanning acoustic signals (data) of the formation around the wellbore reveals the elastic or viscoelastic parameter characteristics of the formation, as well as the lithology, porosity, permeability, type and saturation of fluids within the pores of the subsurface medium outside the wellbore, and the distribution patterns of different fluids in the downhole medium.

[0052] The beneficial effects of this invention are:

[0053] The downhole acoustic scanning logging device based on a fiber optic acoustic sensor provided by this invention replaces the monopole, dipole, or multipole piezoelectric crystal acoustic wave receiving transducer in conventional acoustic scanning logging devices with a fiber optic acoustic wave sensor. This instrument can collect acoustic wave scanning signals for extended periods in high-temperature deep wells. The downhole receiving sensor requires no electronic components or wiring, solving the problem that downhole monopole, dipole, or multipole piezoelectric crystal acoustic wave receiving transducers and their associated high-cost amplifiers, analog-to-digital converters, data storage devices, and downhole data transmission modules cannot operate for extended periods at high temperatures. Through an armored optoelectronic composite logging cable connected to the fiber optic acoustic scanning logging device, the backscattered Rayleigh light signal from the fiber optic acoustic wave sensor can be transmitted at high speed to a surface multi-channel DAS modulator / demodulator, overcoming the bottleneck problem of high-speed upward transmission of large amounts of data signals collected by downhole acoustic scanning logging devices.

[0054] This invention can significantly reduce the manufacturing cost of equipment and instruments for downhole acoustic scanning data acquisition, and achieve high-efficiency acquisition of downhole acoustic scanning data with ultra-high density or extremely high spatial resolution. Through processing and analysis, it is possible to understand the acoustic velocity, elastic parameter characteristics or viscoelastic parameter characteristics of the medium surrounding the wellbore, as well as the lithology, porosity, permeability, type and saturation of fluids within the pores of the underground medium surrounding the wellbore, and the distribution patterns of different fluids in the downhole medium. It can also obtain information on fractures and pores in the formation surrounding the wellbore, as well as the formation structure information around the well, thereby understanding the orientation, dip angle and distribution of fractures and pores in the formation, and realizing the widespread application of fiber optic acoustic scanning logging technology. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of the structural principle of the well acoustic scanning logging device based on fiber optic acoustic wave sensor of the present invention.

[0056] Figure 2 This is a schematic diagram of the fiber optic acoustic wave sensor assembly structure on the fiber optic acoustic wave receiving sensor array of the present invention;

[0057] Figure 3 This is a schematic diagram of the structure of the fiber optic acoustic sensor on the cross-section of an acoustic scanning logging device.

[0058] Explanation of reference numerals in the attached drawings: 1- Acoustic scanning logging device, 2- Photoelectric composite logging cable, 3- Surface wellhead logging vehicle, 4- Surface fiber optic acoustic wave sensing modulation and demodulation instrument, 5- Fiber optic acoustic wave sensor, 6- Monopole acoustic wave transmitter, 7- Dipole acoustic wave transmitter, 8- Acoustic wave transmitter electronic short circuit, 9- Sound insulation body, 10- Fiber optic gyroscope. Detailed Implementation

[0059] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0060] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "longitudinal," "lateral," "horizontal," "inner," "outer," "front," "rear," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0061] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set up," "have," "install," "connect," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0062] The present invention will now be described in detail with reference to the accompanying drawings and embodiments:

[0063] like Figure 1 As shown, the acoustic scanning logging device based on fiber optic acoustic wave sensor includes an acoustic scanning logging device 1 based on fiber optic acoustic wave sensor, a high-temperature resistant photoelectric composite logging cable 2, a surface wellhead logging vehicle 3, and a surface fiber optic acoustic wave sensor modulation and demodulation instrument 4.

[0064] like Figure 2 As shown, the acoustic scanning logging device 1 based on fiber optic acoustic wave sensor includes a high-temperature resistant fiber optic acoustic wave sensor 5 as a receiving unit for acoustic wave signals in the well; three monopole acoustic wave transmitters 6, two dipole acoustic wave transmitters 7, an electronic short circuit for the acoustic wave transmitters 8, a sound insulation body 9, and a fiber optic gyroscope 10; the surface wellhead logging vehicle 3 is connected to the acoustic scanning logging device 1 based on fiber optic acoustic wave sensor in the well via an armored photoelectric composite logging cable 2.

[0065] The three monopole acoustic transmitters 6 can acquire long-spacing and short-spacing data for wellbore compensation at different detection depths.

[0066] The two orthogonal dipole acoustic wave emitters 7 can generate flexural waves to describe the transverse wave slowness of slow and anisotropic formations.

[0067] The surface wellhead logging vehicle 3 controls the descent and ascent of the acoustic scanning logging device 1 of the fiber optic acoustic sensor in the well through the photoelectric composite logging cable 2, and provides power to the acoustic scanning logging device 1 of the fiber optic acoustic sensor in the well. The acoustic transmitter electronic short circuit 8 drives the monopole acoustic transmitter 6 and the dipole acoustic transmitter 7 to continuously and repeatedly transmit acoustic signals during operation.

[0068] The ground fiber optic acoustic wave sensor modulation and demodulation instrument 4, installed at the wellhead, is connected to the downhole acoustic wave scanning logging device 1 via the armored photoelectric composite logging cable 2. It emits laser pulses into the fiber optic acoustic wave sensor 5 and simultaneously collects the backscattered Rayleigh waves inside the fiber optic acoustic wave sensor 5.

[0069] The ground-based fiber optic acoustic modulation and demodulation instrument 4 has a fiber optic acoustic sensor signal input port and a fiber optic gyroscope 10 signal input port.

[0070] like Figure 3 As shown, the acoustic sensor is either a fiber optic acoustic sensor 5 or a fiber optic MEMS acoustic sensor. The acoustic scanning logging device 1 contains a 2-meter-long fiber optic acoustic receiver array with 14 axial receiving points. Each receiving point has 12 fiber optic acoustic sensors 5 placed at 30° intervals around the acoustic scanning logging device 1, for a total of 168 fiber optic acoustic sensors on the instrument. Since the formation P-wave and S-wave velocities increase with increasing distance from the wellbore, the acoustic scanning logging device 1 combines this long source-spacing method with the wellbore compensation Tr short source-spacing method, and also adds circumferentially distributed receivers.

[0071] The fiber optic gyroscope 10 is installed at the top of the acoustic scanning logging device 1 in the well, and measures the azimuth, inclination and dip of the acoustic scanning logging device 1 in real time through the photoelectric composite logging cable 2.

[0072] The acoustic wave transmitter electronic shorting 8 is placed at the upper end of the acoustic wave scanning logging device 1 to drive the monopole acoustic wave transmitter 6 and the dipole acoustic wave transmitter 7 inside the acoustic wave scanning logging device 1. The fiber optic gyroscope 10 is located below the acoustic wave transmitter electronic shorting 8.

[0073] The first monopole acoustic transmitter 6 is positioned below the fiber optic gyroscope 10, followed by an array of 14 fiber optic acoustic sensors 5. Below the 2-meter-long array of fiber optic acoustic sensors 5, a second monopole acoustic transmitter 6 is positioned.

[0074] Below the second monopole acoustic wave transmitter 6, a set of sound insulation bodies 9 are installed to block or prevent the bulk wave energy of the dipole acoustic wave transmitter 7 and the third monopole acoustic wave transmitter 6 below the sound insulation body 9 from being directly coupled to the fiber optic acoustic wave sensor 5 array above the sound insulation body 9.

[0075] Below the sound insulation body 9, two mutually orthogonal dipole acoustic wave emitters 7 and a third lower monopole acoustic wave emitter 6 are sequentially installed. The two dipole acoustic wave emitters 7 are orthogonally oriented. One vibrates along the instrument reference axis, and the other is at 90° to the reference axis. These devices generate a strong flexural wave pattern. The flexural wave pattern propagates up and down along the wellbore and reaches different depths of the formation according to different frequencies.

[0076] The first monopole acoustic wave transmitter 6, the second monopole acoustic wave transmitter 6 and the third monopole acoustic wave transmitter 6 at the top are excited in sequence, and the fiber optic acoustic wave sensor 5 on the fiber optic acoustic wave receiver array collects acoustic wave signals from the formation around the wellbore at different source distances.

[0077] Subsequently, two mutually orthogonal dipole acoustic wave transmitters 7 are excited, and the fiber optic acoustic wave sensor 5 on the fiber optic acoustic wave receiver array collects dipole acoustic wave signals from the formation surrounding the wellbore.

[0078] The measurement method of the acoustic scanning logging device based on fiber optic acoustic sensors includes the following steps:

[0079] S1: Connect the armored high-temperature resistant photoelectric composite logging cable 2 on the winch of the surface wellhead logging vehicle 3 to the acoustic scanning logging device 1 in the well.

[0080] S2: Use the armored high-temperature resistant photoelectric composite logging cable 2 on the winch of the surface wellhead logging vehicle 3 to lower the well acoustic scanning logging device 1 to the bottom of the well;

[0081] S3: The armored high-temperature resistant photoelectric composite logging cable 2 on the winch of the surface wellhead logging vehicle 3 slowly lifts the downhole acoustic scanning logging device 1 upward and sends a command to the acoustic transmitter electronic short circuit 8 in the downhole acoustic scanning logging device 1, thereby driving and exciting the three monopole acoustic transmitters 6 and the two mutually orthogonal dipole acoustic transmitters 7 to emit acoustic signals in sequence.

[0082] S4: Simultaneously activate the fiber optic gyroscope 10 to measure and record in real time the azimuth, dip angle and dip of the uplifting downhole acoustic scanning logging device 1 along the well trajectory;

[0083] S5: Simultaneously activate the ground fiber optic acoustic wave sensor modulation and demodulation instrument 4, and transmit a high-power multi-frequency narrow pulse laser signal to the fiber optic acoustic wave sensor 5 on the fiber optic acoustic wave receiver array in the downhole acoustic wave scanning logging device 1 through the photoelectric composite logging cable 2, while simultaneously receiving the back Rayleigh scattering light signals from 168 fiber optic acoustic wave sensors 5.

[0084] S6: Ground fiber optic acoustic wave sensor modulation and demodulation instrument 4 modulates and demodulates the back Rayleigh scattered light signal on each fiber optic acoustic wave sensor 5, and demodulates the fiber strain or strain rate data measured on each fiber optic acoustic wave sensor 5 into axial component acoustic wave data of fiber optic acoustic wave sensor 5.

[0085] S7: First, three monopole acoustic wave transmitters 6 are sequentially excited, each generating a stronger pressure pulse. These monopole acoustic wave transmitters 6 can generate clear P-waves and S-waves, low-frequency Stoneley waves, and high-frequency energy required for cementing evaluation. Fiber optic acoustic wave sensors 5 on the fiber optic acoustic wave receiver array collect acoustic wave signals such as P-waves, S-waves, and low-frequency Stoneley waves from the formation surrounding the wellbore.

[0086] S8: Then, two mutually orthogonal dipole acoustic transmitters 7 are sequentially excited. Both dipole transmitters are vibration devices composed of electromagnetic motors, which are mounted on a cylinder suspended from the instrument. This mechanism generates a high-voltage dipole signal without causing vibration of the instrument housing. The source can be driven in two modes: a conventional dipole source in pulse mode generates a deep "click" signal, while the acoustic scanning logging instrument uses a frequency sweep to generate a linear frequency modulated pulse signal. Compared to a narrowband dipole source, the linear frequency modulated pulse mode maintains each frequency for a longer time, providing more dipole energy to the formation. A fiber optic acoustic sensor 5, located below the first monopole acoustic transmitter 6, collects three-component acoustic signals from the formation surrounding the wellbore.

[0087] S9: Based on the direct acoustic travel time from the positions of the three monopole acoustic transmitters 6 and two mutually orthogonal dipole acoustic transmitters 7 in the downhole acoustic scanning logging device 1 to each acoustic detection point on the fiber optic acoustic sensor 5 in the downhole acoustic scanning logging device 1, and the distance from the positions of the downhole monopole acoustic transmitters 6 and dipole acoustic transmitters 7 to the known detection points, calculate the average acoustic velocity from the known monopole acoustic transmitters 6 and dipole acoustic transmitters 7 to each known acoustic detection point;

[0088] If the data processor picks up the travel time of the sound wave directly to the longitudinal wave, what is calculated is the average velocity of the longitudinal wave.

[0089] If the travel time of the sound wave directly to the transverse wave is collected, the calculated value is the average velocity of the transverse wave.

[0090] If the travel time of a low-frequency Stoneley wave is picked up, the calculated value is the average velocity of the low-frequency Stoneley wave.

[0091] S10: By recording multiple arrayed acoustic logging curves with different acoustic transmitters and different source distances (distance between the transmitter and receiver), correlation and superposition processing can effectively suppress interference and accurately extract various information of P-waves, S-waves, and low-frequency Stoneley waves. Since the receiver spacing can be very small, it can meet the needs of thin-layer research.

[0092] S11: Use long-spacing acoustic logging curves (over 3 meters) to extract P-wave, S-wave, and Stoneley wave information from open-hole formations; use short-spacing acoustic systems (1 meter) to perform cement bond logging (CBL) in casing wells, and use acoustic systems (1.5 meters) to perform variable density logging (VDL). These two measurement results can be used to check the cement consolidation quality of casing wells.

[0093] S12: By processing and analyzing the acoustic signals of formation P-waves, S-waves, and low-frequency Stoneley waves received by a total of 168 fiber optic acoustic sensors 5, with 12 sensors at each receiving point placed at 30° intervals around the acoustic scanning logging device 1, it is possible to understand whether there is anisotropy in the velocities of formation P-waves, S-waves, and low-frequency Stoneley waves within a 360-degree range around the acoustic scanning logging device 1, and whether there is anisotropy in the formation's elastic or viscoelastic parameters. This enables acoustic scanning logging of the formation around the wellbore. Further processing and interpretation of the scanning acoustic signals (data) of the formation around the wellbore reveals the elastic or viscoelastic parameter characteristics of the formation, as well as the lithology, porosity, permeability, type and saturation of fluids within the pores of the subsurface medium outside the wellbore, and the distribution patterns of different fluids in the downhole medium.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Based on the technical essence of the present invention, any simple modifications, equivalent substitutions, and improvements made to the above embodiments within the spirit and principles of the present invention shall still fall within the protection scope of the present invention.

Claims

1. An acoustic scanning logging device based on a fiber optic acoustic sensor, characterized in that, The system includes an acoustic scanning logging device based on a fiber optic acoustic sensor (1), a high-temperature resistant photoelectric composite logging cable (2), a surface wellhead logging vehicle (3), and a surface fiber optic acoustic sensor modulation and demodulation instrument (4). The acoustic wave scanning logging device (1) based on the optical fiber acoustic wave sensor includes a high temperature resistant optical fiber acoustic wave sensor (5) as an acoustic wave signal receiving unit in the well. Three monopole acoustic wave transmitters (6), two dipole acoustic wave transmitters (7), acoustic wave transmitter electronic short circuit (8), sound insulation body (9), fiber optic gyroscope (10); the surface wellhead logging vehicle (3) is connected to the acoustic wave scanning logging device (1) of the fiber optic acoustic wave sensor in the well through armored photoelectric composite logging cable (2). The acoustic transmitter electronic short circuit (8) is placed at the upper end of the acoustic scanning logging device (1) to drive the monopole acoustic transmitter (6) and dipole acoustic transmitter (7) in the acoustic scanning logging device (1). The fiber optic gyroscope (10) is placed below the acoustic transmitter electronic short circuit (8). Three monopole acoustic transmitters (6) can acquire long-spacing and short-spacing data for wellbore compensation at different detection depths; the first monopole acoustic transmitter (6) is placed below the fiber optic gyroscope (10), followed by the fiber optic acoustic sensor (5) array, and below the fiber optic acoustic sensor (5) array, the second monopole acoustic transmitter (6) is placed. Below the second monopole sound wave transmitter (6), a set of sound insulation bodies (9) are installed. Two orthogonal dipole acoustic emitters (7) can generate flexural waves to describe the transverse wave slowness of slow and anisotropic formations. The ground wellhead logging vehicle (3) controls the downhole and uphole of the acoustic scanning logging device (1) of the fiber optic acoustic sensor in the well through the photoelectric composite logging cable (2), and provides power to the acoustic scanning logging device (1) of the fiber optic acoustic sensor in the well. The acoustic transmitter electronic short circuit (8) drives the monopole acoustic transmitter (6) and the dipole acoustic transmitter (7) to continuously and repeatedly transmit acoustic signals during operation. The ground fiber optic acoustic wave sensor modulation and demodulation instrument (4) installed at the wellhead is connected to the downhole acoustic wave scanning logging device (1) through the armored photoelectric composite logging cable (2) to emit laser pulses into the fiber optic acoustic wave sensor (5) and simultaneously collect the backscattered Rayleigh waves in the fiber optic acoustic wave sensor (5).

2. The acoustic scanning logging device based on a fiber optic acoustic sensor according to claim 1, characterized in that, The ground fiber optic acoustic sensor modulation and demodulation instrument (4) has a fiber optic acoustic sensor signal input port and a fiber optic gyroscope (10) signal input port.

3. The acoustic scanning logging device based on a fiber optic acoustic sensor according to claim 1, characterized in that, The optical fiber acoustic receiver array inside the acoustic scanning logging device (1) has multiple axial receiving points, and each receiving point has at least three optical fiber acoustic sensors (5) arranged in a ring with uniform intervals around the acoustic scanning logging device (1).

4. The acoustic scanning logging device based on a fiber optic acoustic sensor according to claim 1, characterized in that, The fiber optic gyroscope (10) is installed at the top of the acoustic scanning logging device (1) in the well, and measures the azimuth, dip angle and inclination of the acoustic scanning logging device (1) in real time through the photoelectric composite logging cable (2).

5. The acoustic scanning logging device based on a fiber optic acoustic sensor according to claim 1, characterized in that, Below the sound insulation body (9), two mutually orthogonal dipole sound wave emitters (7) and a third monopole sound wave emitter (6) are arranged in sequence.

6. The acoustic scanning logging device based on a fiber optic acoustic sensor according to claim 1, characterized in that, The two dipole acoustic transmitters (7) are orthogonally oriented, one vibrating along a reference axis parallel to the extension direction of the acoustic scanning logging device (1), and the other at 90° to the reference axis.

7. A measurement method for an acoustic scanning logging device based on a fiber optic acoustic sensor, applied in the acoustic scanning logging device based on a fiber optic acoustic sensor as described in any one of claims 1-6, characterized in that, Includes the following steps: S1: Connect the armored high-temperature resistant photoelectric composite logging cable (2) on the winch of the surface wellhead logging vehicle (3) to the acoustic scanning logging device (1) in the well. S2: Using the armored high-temperature photoelectric composite logging cable (2) on the winch of the surface wellhead logging vehicle (3), the acoustic scanning logging device (1) in the well is lowered to the bottom of the well; S3: The armored high-temperature photoelectric composite logging cable (2) on the winch of the wellhead logging vehicle (3) slowly lifts the downhole acoustic scanning logging device (1) and sends a command to the acoustic transmitter electronic short circuit (8) in the downhole acoustic scanning logging device (1), thereby driving and exciting three monopole acoustic transmitters (6) and two mutually orthogonal dipole acoustic transmitters (7) to emit acoustic signals. S4: Simultaneously activate the fiber optic gyroscope (10) to measure and record in real time the azimuth, dip angle and dip of the uplifting downhole acoustic scanning logging device (1) along the well trajectory; S5: Simultaneously start the ground fiber optic acoustic sensor modulation and demodulation instrument (4), and transmit a high-power multi-frequency narrow pulse laser signal to the fiber optic acoustic sensor (5) on the fiber optic acoustic receiver array in the downhole acoustic scanning logging device (1) through the photoelectric composite logging cable (2), and simultaneously receive the back Rayleigh scattering light signals from 168 fiber optic acoustic sensors (5). S6: Ground fiber optic acoustic wave sensor modulation and demodulation instrument (4) modulates and demodulates the back Rayleigh scattered light signal on each fiber optic acoustic wave sensor (5) and demodulates the fiber strain or strain rate data measured on each fiber optic acoustic wave sensor (5) into axial component acoustic wave data of fiber optic acoustic wave sensor (5). S7: First, the first monopole acoustic transmitter (6), the second monopole acoustic transmitter (6) and the third monopole acoustic transmitter (6) at the top are excited in sequence. The fiber optic acoustic sensor (5) on the fiber optic acoustic receiver array collects acoustic signals from different source distances of the formation around the wellbore. These three monopole acoustic transmitters (6) can generate stronger pressure pulses. These monopole acoustic transmitters (6) can generate clear longitudinal and transverse waves, low-frequency Stoneley waves and high-frequency energy required for cementing evaluation. The fiber optic acoustic sensor (5) on the fiber optic acoustic receiver array collects longitudinal and transverse waves, low-frequency Stoneley wave acoustic signals from the formation around the wellbore. S8: Then, two mutually orthogonal dipole acoustic wave transmitters (7) are excited in sequence. The fiber optic acoustic wave sensor (5) on the fiber optic acoustic wave receiver array collects dipole acoustic wave signals from the formation around the wellbore. Both dipole transmitters are a kind of vibration device composed of electromagnetic motors. The electromagnetic motors are installed on a cylinder suspended on the instrument. This mechanism generates a high-voltage dipole signal without causing the instrument shell to vibrate. The source can be driven in two modes: the traditional dipole source in pulse mode generates a very deep "click" signal. The acoustic wave scanning logging instrument uses frequency sweeping to generate a linear frequency modulated pulse signal. Compared with the narrowband dipole source, the linear frequency modulated pulse mode maintains each frequency for a longer time and can provide more dipole energy to the formation. The fiber optic acoustic wave sensor (5) installed under the first monopole acoustic wave transmitter (6) collects three-component acoustic wave signals from the formation around the wellbore. S9: Based on the direct acoustic travel time from the positions of the three monopole acoustic transmitters (6) and two mutually orthogonal dipole acoustic transmitters (7) in the downhole acoustic scanning logging device (1) to each acoustic detector point on the fiber optic acoustic sensor (5) in the downhole acoustic scanning logging device (1) and the distance from the positions of the downhole monopole acoustic transmitters (6) and dipole acoustic transmitters (7) to the known detector points, calculate the average acoustic velocity from the known monopole acoustic transmitters (6) and dipole acoustic transmitters (7) to each known acoustic detector point; If the data processor picks up the travel time of the sound wave directly to the longitudinal wave, what is calculated is the average velocity of the longitudinal wave. If the travel time of the sound wave directly to the transverse wave is collected, the calculated value is the average velocity of the transverse wave. If the travel time of a low-frequency Stoneley wave is picked up, the calculated value is the average velocity of the low-frequency Stoneley wave. S10: By recording multiple array acoustic logging curves with different acoustic transmitters and different source distances, correlation and superposition processing are performed. The source distance is the distance between the transmitter and the receiver. Interference can be effectively suppressed and various information of longitudinal waves, transverse waves and low-frequency Stoneley waves can be accurately extracted. Since the distance between the receivers can be very small, it can meet the needs of thin-layer research. S11: Use long-spacing acoustic logging curves with a source distance of more than 3 meters to extract P-wave, S-wave, and Stoneley wave information of open-hole formations; use a short-spacing acoustic system with a source distance of 1 meter to perform cement bond logging (CBL) in casing wells, and use an acoustic system with a source distance of 1.5 meters to perform variable density logging (VDL). These two measurement results can be used to check the cement consolidation quality of casing wells. S12: By processing and analyzing the acoustic signals of formation longitudinal waves, transverse waves and low-frequency Stoneley waves received by a total of 168 fiber optic acoustic sensors (5), 12 fiber optic acoustic sensors (5) placed at 30° intervals around the acoustic scanning logging device (1) at each receiving point, we can understand whether there is anisotropy of formation longitudinal waves, transverse waves and low-frequency Stoneley waves within the 360-degree range around the acoustic scanning logging device (1), whether there is anisotropy of formation elastic parameters or viscoelastic parameters, and realize acoustic scanning logging of the formation around the wellbore. Through further processing and interpretation of the scanning acoustic signal data of the formation around the wellbore, we can understand the elastic parameter characteristics or viscoelastic parameter characteristics of the formation around the wellbore, as well as the lithology, porosity, permeability, type and saturation of fluids in the underground medium outside the wellbore, and the distribution law of different fluids in the downhole medium.

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