An adjustable downhole ultrasonic lamb wave transducer strip and a measuring method thereof

Abstract

The application discloses a downhole adjustable ultrasonic Lamb wave transducer strip and a measuring method thereof, and belongs to the technical field of downhole ultrasonic measurement. The downhole adjustable ultrasonic Lamb wave transducer strip comprises a strip frame, an ultrasonic transducer assembly installed on the strip frame, a Lamb wave transducer group installed in an inclined mode and a pulse echo transducer installed in a vertical mode, an angle adjusting assembly connected with the Lamb wave transducer group and used for adjusting the emitting and receiving angles of the Lamb wave transducer group, a radial distance adjusting assembly connected with the pulse echo transducer and used for adjusting the radial position of the pulse echo transducer, a temperature sensor and a pressure sensor installed on the strip frame, and a main control circuit electrically connected with the temperature sensor, the pressure sensor, the ultrasonic transducer assembly, the angle adjusting assembly and the radial distance adjusting assembly respectively. The application realizes downhole dynamic adjustment of the Lamb wave angle and the pulse echo radial distance, and improves the quality of ultrasonic measurement signals.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic detection technology, and in particular to a downhole adjustable ultrasonic Lamb wave transducer strip and its measurement method. Background Technology

[0002] In the fields of oil and gas well cementing quality evaluation and casing integrity inspection, ultrasonic Lamb wave technology has attracted widespread attention due to its high sensitivity to defects such as casing wall thickness variations, corrosion, and microcracks. When Lamb waves propagate in thin-plate structures, their excitation efficiency and mode characteristics are highly dependent on the matching relationship between the incident angle and the excitation frequency. Especially in complex downhole environments, it is necessary to precisely control the transmission and reception angles of the transducer to effectively excite specific modes of Lamb waves, thereby achieving high-resolution imaging of the casing condition.

[0003] However, existing downhole ultrasonic Lamb wave logging probes generally suffer from the following technical defects: First, their structural design is mostly geared towards wireline logging modes, lacking adaptability to different drill string delivery methods, making them difficult to deploy in highly deviated wells, horizontal wells, or workover operations; second, the Lamb wave transducer is usually rigidly mounted on the probe body at a fixed angle. When the well fluid temperature and pressure change drastically with depth, the well fluid sound velocity changes significantly, and the optimal incident angle calculated according to Snell's law shifts accordingly. A fixed angle cannot dynamically track this change, resulting in a decrease in Lamb wave excitation efficiency and mode... Severe aliasing significantly impacts the signal-to-noise ratio and detection reliability. Furthermore, pulse echo transducers used to measure the distance between the instrument and the casing inner wall often employ a fixed radial position design. If the distance between the instrument and casing fluctuates due to wellbore irregularities or eccentricity, the echo amplitude will be affected by non-defect factors, leading to distorted cementation evaluation or misjudgment of casing damage. Finally, existing systems generally lack real-time sensing capabilities of the downhole temperature and pressure environment and fail to establish a closed-loop feedback control mechanism between temperature and pressure, sound velocity, incident angle, and radial distance, resulting in a lack of adaptability and robustness throughout the measurement process. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a downhole adjustable ultrasonic Lamb wave transducer strip and its measurement method, aiming to solve the problems of existing ultrasonic Lamb wave logging probes being unable to adapt to drill string delivery measurement methods, the inability to adjust the transducer angle and radial position leading to signal quality degradation and limited measurement accuracy, and the lack of an adaptive control mechanism for downhole temperature and pressure environments. The specific solution is as follows: In a first aspect, the present invention provides a downhole adjustable ultrasonic Lamb wave transducer strip, comprising: a strip frame; An ultrasonic transducer assembly, mounted on the strip frame, includes an inclined Lamb wave transducer group and a vertically mounted pulse echo transducer. An angle adjustment component, connected to the Lamb wave transducer group, is used to adjust the transmission and reception angles of the Lamb wave transducer group; A radial distance adjustment component, connected to the pulse echo transducer, is used to adjust the radial position of the pulse echo transducer; Temperature and pressure sensors are mounted on the strip frame; The main control circuit is electrically connected to the temperature sensor, pressure sensor, ultrasonic transducer assembly, angle adjustment assembly, and radial distance adjustment assembly, respectively. The main control circuit is configured to control the angle adjustment component based on the signals from the temperature sensor and the pressure sensor, and to control the radial distance adjustment component based on the echo signal from the pulse echo transducer.

[0005] Furthermore, the Lamb wave transducer group includes a transmitting transducer and at least one receiving transducer.

[0006] Furthermore, the angle adjustment component synchronously and in the opposite direction adjusts the angles of the transmitting transducer and the receiving transducer.

[0007] Furthermore, the number of receiving transducers is four.

[0008] Furthermore, the angle adjustment assembly includes a dual-axis motor and a first angle push rod and a second angle push rod driven by the dual-axis motor. The first angle push rod is connected to the transmitting transducer, and the second angle push rod is connected to the receiving transducer.

[0009] Furthermore, the radial distance adjustment assembly includes a push rod motor and an adjusting piston, wherein the push rod motor drives the adjusting piston to move, thereby changing the radial extension distance of the pulse echo transducer.

[0010] Furthermore, the strip also includes conduits for accommodating wires connecting the various electrical components.

[0011] Furthermore, the main control circuit is also configured to: calculate the current well fluid sound velocity based on the well fluid sound velocity mathematical model according to the real-time temperature and pressure collected by the temperature sensor and pressure sensor, calculate the optimal incident angle according to the law of sound wave refraction, and adjust the Lamb wave transducer group based on the optimal incident angle by controlling the angle adjustment component.

[0012] Furthermore, the main control circuit is also configured to: calculate the actual radial distance between the transducer and the inner wall of the sleeve based on the echo signal received by the pulse echo transducer, compare the actual radial distance with a preset initial distance to obtain a distance correction value, and control the radial distance adjustment component to adjust the radial position of the pulse echo transducer based on the correction value.

[0013] Secondly, the present invention provides a downhole adjustable ultrasonic Lamb wave measurement method, applied to a downhole adjustable ultrasonic Lamb wave transducer strip, comprising the following steps: Real-time downhole temperature and pressure are collected using temperature and pressure sensors; Calculate the current well fluid velocity based on the temperature and pressure, and calculate the optimal Lamb wave incident angle based on the well fluid velocity. Adjust the Lamb wave transducer group based on the optimal Lamb wave incident angle control angle adjustment component; The pulse echo transducer receives the pulse echo signal, and the actual radial distance between the transducer and the inner wall of the casing is calculated based on the echo signal. Based on the actual radial distance, the radial distance adjustment component is controlled to adjust the radial distance of the pulse echo transducer to a preset value.

[0014] This invention discloses a downhole adjustable ultrasonic Lamb wave transducer strip and its measurement method. The beneficial effects of this technical solution include at least the following: 1. This invention uses temperature and pressure sensors to collect downhole fluid temperature and pressure in real time. Combined with a pre-stored mathematical model of well fluid sound velocity and the law of sound wave refraction, the main control circuit calculates the optimal Lamb wave incident angle in real time and controls the angle adjustment component to synchronously and in reverse adjust the inclined transmitting and receiving transducers. Regardless of changes in downhole temperature and pressure, the Lamb wave transducer group always excites and receives specific mode Lamb waves at the optimal angle, further improving the signal-to-noise ratio and measurement reliability.

[0015] 2. This invention utilizes a pulse echo transducer to calculate the actual radial distance between itself and the inner wall of the casing in real time, and compares it with a preset initial distance. A pushrod motor drives an adjusting piston to change the transducer's extension, restoring the radial distance to the preset value. This solution effectively compensates for spacing changes caused by instrument eccentricity in highly deviated and horizontal wells, ensuring that pulse echo amplitude variations primarily originate from the casing's condition rather than non-casing damage, thus improving accuracy.

[0016] 3. This invention integrates all functional components onto a single frame, which can be embedded in the drill string body and transported with the drill string to high-angle wells, horizontal wells, and workover wells. This realizes the drill string transmission measurement method, overcoming the limitation that traditional cable logging instruments cannot be used for drill string transmission. At the same time, the modular design facilitates inspection and maintenance. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this specification, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the external structure of a downhole adjustable ultrasonic Lamb wave transducer strip provided as an embodiment of this specification.

[0019] Figure 2 This is a schematic diagram of a downhole adjustable ultrasonic Lamb wave transducer strip assembly provided as an embodiment of this specification.

[0020] Figure 3 This is a strip Lamb wave dispersion curve of an adjustable ultrasonic Lamb wave transducer provided as an embodiment of this specification.

[0021] Figure 4 This is a schematic diagram illustrating the frequency and angle of a downhole adjustable ultrasonic Lamb wave transducer strip excited in a specific mode, as provided in the embodiments of this specification.

[0022] Figure 5 This is a schematic diagram of a downhole adjustable ultrasonic Lamb wave transducer strip downhole measurement model provided as an embodiment of this specification.

[0023] Figure 6 This is a schematic flowchart of a downhole adjustable ultrasonic Lamb wave transducer strip measurement method provided as an embodiment of this specification.

[0024] Explanation of reference numerals in the attached diagram: 1. Strip frame; 2. Transmitting transducer; 3. Receiving transducer; 4. Pulse echo transducer; 5. Dual-axis motor; 6. First angle push rod; 7. Second angle push rod; 8. Push rod motor; 9. Adjusting piston; 10. Cable guide tube; 11. Main control circuit; 12. Temperature sensor; 13. Pressure sensor. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The terms "first," "second," "third," etc., in the specification, claims, and accompanying drawings are used to distinguish different objects, not to describe a specific order. In addition, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0026] In the following description, terms such as “inner,” “outer,” “upper,” “lower,” “left,” and “right” are used only to facilitate the description of the embodiments and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this specification.

[0027] Before introducing the technical solutions described in this manual, the application scenarios and related technologies of the technical solutions will be introduced.

[0028] Casing well logging is a logging operation performed after steel casing has been run into an oil well. It is mainly divided into reservoir evaluation and engineering inspection. Ultrasonic Lamb wave logging technology is one of the key technologies in the engineering inspection field, capable of evaluating cementing quality and detecting casing corrosion and deformation. Currently, mainstream ultrasonic Lamb wave logging primarily uses wireline logging instruments. The measurement probe employs a combination of one self-transmitting and self-receiving ultrasonic pulse echo transducer and one inclined transmitter and two inclined receiver ultrasonic Lamb wave transducers. The self-transmitting and self-receiving transducer receives the ultrasonic pulse echo signal returned from the casing, used for casing damage and backfill acoustic impedance calculations; while the ultrasonic Lamb wave transducers receive the Lamb wave signal returned from the casing, used for calculating the backfill Lamb wave attenuation rate and casing eccentricity. Existing ultrasonic Lamb wave measurement probes cannot meet the requirements of drill string delivery measurement methods, and the ultrasonic transducer is in a fixed state downhole for measurement, making it impossible to dynamically adjust the Lamb wave emission angle and pulse echo measurement distance downhole. Due to changes in the measurement depth of the instrument downhole, the temperature and pressure of the well fluid in the wellbore also change, leading to changes in the well fluid density and elastic modulus, which in turn alters the well fluid sound velocity. This makes it impossible to excite a specific Lamb wave mode in the casing under optimal conditions, thus affecting signal quality. At the same time, during high-angle and horizontal well operations, the instrument is often eccentric, causing changes in the distance between the ultrasonic pulse echo transducer and the inner wall of the casing, thereby affecting the pulse echo amplitude and resulting in echo amplitude variations caused by non-casing damage factors.

[0029] Therefore, how to design a drill string-transmitting ultrasonic Lamb wave probe while simultaneously achieving synchronous adjustment of the downhole dynamic Lamb wave transmission and reception angles and the radial distance adjustment of the ultrasonic pulse echo is an urgent problem to be solved. Please refer to the appendix for details. Figure 1 and attached Figure 2 This embodiment provides a downhole adjustable ultrasonic Lamb wave transducer strip for mounting on the drill string body, enabling dynamic adjustment of the Lamb wave angle and pulse echo radial distance during casing well logging. The downhole adjustable ultrasonic Lamb wave transducer strip provided in this embodiment includes a strip frame 1, which serves as an integral support structure for fixing and integrating various functional components. The strip frame 1 is equipped with an ultrasonic transducer assembly, an angle adjustment assembly, a radial distance adjustment assembly, a temperature sensor 12, a pressure sensor 13, a main control circuit 11, and a conduit 10.

[0030] The ultrasonic transducer assembly includes an inclined Lamb wave transducer group and a vertically mounted pulse-echo transducer. The Lamb wave transducer group comprises an inclined transmitting transducer 2 and at least one inclined receiving transducer 3. In this embodiment, there are four receiving transducers 3, spaced apart along the length of the strip frame 1, used to receive Lamb wave signals from the sheath wall. The pulse-echo transducer is vertically mounted on the strip frame and is used to vertically transmit ultrasonic pulses towards the sheath wall and receive the reflected echoes. It should be noted that the pulse-echo transducer operates in a self-transmitting and self-receiving mode, meaning that the same transducer is used both to transmit ultrasonic pulses and to receive the reflected echoes returning from the sheath wall.

[0031] An angle adjustment assembly is connected to the Lamb wave transducer group and is used to synchronously and in reverse adjust the angles of the transmitting transducer and the receiving transducer. It should be noted that reverse adjustment means that when the transmitting transducer 2 rotates clockwise by a certain angle, the receiving transducer 3 rotates counterclockwise by the same angle, to ensure that the transmitted and received sound beams remain symmetrical with respect to the sleeve normal. In this embodiment, the angle adjustment assembly specifically includes a dual-axis motor 5 and a first angle push rod 6 and a second angle push rod 7 driven by the dual-axis motor 5. The first angle push rod 6 is connected to the receiving transducer 3, and the second angle push rod 7 is connected to the transmitting transducer 2. When the dual-axis motor 5 is running, it can synchronously and in reverse drive the two push rods, thereby synchronously and in reverse adjusting the tilt angles of the transmitting and receiving transducers, maintaining a symmetrical incident and received relationship between them.

[0032] The radial distance adjustment assembly is connected to the pulse echo transducer and is used to adjust the radial position of the pulse echo transducer, that is, the distance between it and the inner wall of the sleeve. In this embodiment, the radial distance adjustment assembly includes a push rod motor 8 and an adjusting piston 9. The push rod motor 8 drives the adjusting piston 9 to move radially, thereby changing the radial extension distance of the pulse echo transducer relative to the strip frame 1, and realizing the dynamic adjustment of its distance from the inner wall of the sleeve.

[0033] Temperature sensor 12 and pressure sensor 13 are both directly mounted on the strip frame 1, and are used to collect the well fluid temperature and pressure in the downhole environment in real time, respectively.

[0034] The main control circuit is electrically connected to temperature sensor 12, pressure sensor 13, ultrasonic transducer assembly, angle adjustment assembly, and radial distance adjustment assembly, respectively, and is responsible for coordinating the operation of the entire system. Based on the real-time temperature and pressure data collected by temperature sensor 12 and pressure sensor 13, the main control circuit 11 calls a pre-established well fluid sound velocity mathematical model to calculate the current well fluid sound velocity. Combining this with the propagation speed of the Lamb wave in the casing, it calculates the optimal incident angle required to excite a specific mode of Lamb wave according to the law of sound wave refraction, and then generates an angle correction command. This command controls the dual-axis motor to drive two angle push rods, causing the transmitting and receiving transducers to synchronously and in reverse adjust to the optimal angle. The well fluid sound velocity mathematical model can be established based on laboratory calibration data of the actual well fluid system. For example, for water-based drilling fluids, the sound velocity is approximately negatively correlated with temperature and positively correlated with pressure; for oil-based drilling fluids, the sound velocity variation is different. The main control circuit 11 has pre-stored model parameters for the current well fluid system, enabling real-time sound velocity calculation. It should be noted that the Lamb wave is an elastic guided wave propagating in a plate-like structure. Its dispersion characteristics are closely related to the plate thickness d and the operating frequency f. Given the plate thickness d0, the dispersion curve is calculated. Please refer to the appendix for the dispersion curve. Figure 3 The propagation speed of different modes of Lamb waves (A0, S0, A1, S1 and S2) changes with frequency. Since the propagation speed of the A0 mode Lamb wave changes more gradually in the operating frequency range of 100-500kHz, a specific A0 mode Lamb wave is selected for measurement.

[0035] According to the law of refraction of sound waves, the following relationship holds: In the formula: This indicates the angle of incidence between the ultrasonic wave and the plate. Indicates the sound velocity of the well fluid. This represents the propagation speed of the Lamb wave in the plate. According to the law of refraction of sound waves, changes in the sound velocity of the well fluid will alter the optimal incident angle. Therefore, in order to ensure the excitation and reception of a specific mode of Lamb wave, it is necessary to adjust the transducer's emission and reception angles.

[0036] Given the thickness d0 of the plate, the attached Figure 4 The diagram illustrates the relationship between Lamb wave frequency and angle. It shows that different modes of Lamb waves can be excited by varying the operating frequency and incident angle. Therefore, to ensure a relatively pure A0 mode Lamb wave, the angle adjustment of the oblique transmitter / receiver transducer needs to be limited to a suitable range. Inside.

[0037] In this embodiment, an adjustable ultrasonic Lamb wave transducer strip is embedded in the drill string body. The measuring device operates in the well fluid, which includes a metal casing, back cement, and formation. During measurement, the inclined transducer transmits and receives signals... An angled incident signal is received by the ultrasonic Lamb wave signal from the sheath, while a self-generating and self-receiving transducer is perpendicularly incident on the sheath to receive the ultrasonic pulse echo signal from the sheath. Simultaneously, with the aid of an auxiliary... Figure 2 The temperature and pressure sensor 13 shown obtains the real-time downhole fluid sound velocity. Through numerous temperature and pressure experiments with different well fluid systems, the sound velocity of well fluids was established. With temperature ,pressure Mathematical relationship model between them: The model is usually a nonlinear function that can accurately reflect the influence of temperature and pressure on sound velocity. It can be pre-calibrated according to the actual well fluid system and stored in the main control circuit 11.

[0038] Appendix Figure 5 The image shows a measurement model. Before the measurement device is lowered into the well, the workers set the initial Lamb wave transmission and reception angles at the wellhead according to the casing specifications and operating frequency. 0 and the initial distance between the self-generating and self-receiving transducer and the inner wall of the casing. 0. During downhole operation, temperature sensor 12 and pressure sensor 13 collect real-time temperature data of the downhole fluid. and pressure According to the sound velocity of well fluid With temperature ,pressure The mathematical relationship model can obtain the real-time sound velocity of the well fluid downhole. Based on the working frequency and thickness, by Figure 3 The speed of the Lamb wave can be known The optimal angle of incidence can be calculated using the law of refraction of sound waves. The angle correction value is obtained by comparing the initial transmit and receive angles. The correction value is input into the main control circuit, which controls the dual-axis motor to rotate and drive the angle push rod to move, so that the angled transmitter and receiver transducers can be synchronously and in reverse adjusted to the same angle to the optimal incident angle. This allows for the acquisition of the optimal specific mode Lamb wave; for self-generating and self-receiving transducers, the distance between the transducer and the casing inner wall is calculated based on the acquired downhole pulse echoes. The distance correction value is obtained by comparing the initial spacing. The correction value is input into the main control circuit, which controls the push rod motor to adjust the piston distance, thereby changing the oil volume of the self-generating and self-receiving transducer and achieving radial distance adjustment. 0, thus obtaining the optimal ultrasonic pulse echo.

[0039] The strip frame also features internal conduits to accommodate and protect the wires connecting various electrical components, improving the overall wiring neatness and reliability. The strip employs a modular design, facilitating integration into drill string conveyor measuring instruments while ensuring structural strength and transducer positional straightness, making it suitable for high-precision casing inspection under complex downhole conditions.

[0040] In this embodiment, the dynamic radial distance adjustment mechanism of the self-generating and self-receiving transducer ensures that the variation in ultrasonic pulse echo amplitude mainly originates from changes in the state of the sleeve itself, rather than signal attenuation differences caused by fluctuations in the distance between the transducer and the sleeve. Furthermore, the synchronous reverse adjustment mechanism of the angle adjustment component ensures that the transmission and reception paths meet the acoustic refraction conditions, effectively exciting and receiving the Lamb wave of the target mode, and improving the detection signal-to-noise ratio and mode purity.

[0041] This embodiment also provides a downhole adjustable ultrasonic Lamb wave measurement method, applied to the aforementioned downhole adjustable ultrasonic Lamb wave transducer strip. Please refer to the appendix. Figure 6 The method includes the following steps: Step S1: Collect real-time downhole temperature and pressure using temperature and pressure sensors mounted on the strip frame; Step S2: Calculate the current well fluid sound velocity and optimal incident angle: Based on the collected temperature and pressure, the main control circuit calls the nonlinear well fluid sound velocity mathematical model established based on temperature and pressure experiments of different well fluid systems to calculate the current well fluid sound velocity. Then, combining the casing thickness and the propagation speed of the A0 mode Lamb wave at the operating frequency, it calculates the optimal Lamb wave incident angle required to excite this mode according to the law of sound wave refraction. For details, please refer to the appendix. Figure 3 and attached Figure 4 That is, given the center frequency f0 of the Lamb wave transducer, the velocity of sound of the corresponding A0 mode Lamb wave can be obtained. and the best Lamb wave angle of incidence Specifically, in casing wells, since the density of the fluid and cement inside the well is less than that of the steel casing, when ultrasonic waves are obliquely incident on the casing interface, the dispersion characteristics of the various modes of waves excited are quite similar to those of Lamb waves in free solid plates. Therefore, the analysis is based on the relevant theories of Lamb waves in free solid plates.

[0042] The dispersion curve solution method is based on the fundamental principles and characteristics of Lamb waves in a free solid plate. It analyzes the Rayleigh-Lamb equation and provides the expression for the symmetric mode: The expression for antisymmetric mode: , , In the formula, The wave number is along the horizontal direction of the plate. It is 1 / 2 plate thickness. Angular frequency, , The longitudinal wave velocity (constant) is given. This represents the transverse wave velocity (constant). Phase velocity. The frequency varies, and this is reflected in the phase velocity-frequency thickness plane as a series of curves, which are the phase velocity dispersion curves of the Lamb wave. According to... and By solving the Rayleigh-Lamb equation piecewise using numerical methods, the phase velocity curve of the Lamb wave is obtained. Using a wedge probe to excite the Lamb wave, the excitation curves of Lamb waves at different angles can be calculated from the phase velocity curves.

[0043] It should be noted that in establishing the nonlinear well fluid sound velocity mathematical model, since the well fluid sound velocity is related to temperature and pressure, different well fluid samples used in actual well workover operations can be selected and temperature and pressure experiments can be conducted in the laboratory to obtain the sound velocity at different temperatures and pressures. This allows the establishment of a functional relationship with temperature T and pressure P as independent variables and well fluid sound velocity V as the dependent variable. Using this functional relationship, the well fluid velocity can be determined under different downhole temperatures and pressures.

[0044] Since the actual instrument adds a mud sound velocity transducer to the non-strip section to measure the sound velocity of well fluid under different downhole temperatures and pressures, this patent innovatively proposes to add temperature and pressure sensors to distinguish it from previous patents.

[0045] Step S3: Adjust the angle of the Lamb wave transducer group: The main control circuit generates an angle correction command, controls the dual-axis motor to drive the first angle push rod and the second angle push rod, so that the transmitting transducer and the four receiving transducers are synchronously and in reverse adjusted to the optimal incident angle, ensuring that the Lamb wave is efficiently excited and effectively received in the set mode.

[0046] It should be noted that the speed of sound of a Lamb wave According to the law of refraction of sound waves, the following relationship is satisfied: The optimal Lamb wave incident angle can then be calculated. In the formula: This indicates the angle of incidence between the ultrasonic wave and the plate. Indicates the sound velocity of the well fluid. This represents the propagation speed of the Lamb wave in the plate.

[0047] Based on the real-time sound velocity of the well fluid under different downhole temperatures and pressures, the Lamb wave incident angle corresponding to the actual well fluid sound velocity is calculated at the wellhead. If the well fluid sound velocity increases after entering the well, the Lamb wave incident angle also needs to be increased; if the well fluid sound velocity decreases, the Lamb wave incident angle also needs to be decreased. A correction command activation threshold can be set, that is, when the relative error is greater than δ, the downhole transducer is dynamically corrected to the actual required Lamb wave incident angle.

[0048] Step S4: Receive pulse echo and calculate actual radial distance: The pulse echo transducer emits ultrasonic pulses vertically toward the inner wall of the sleeve and receives the echo signal. The main control circuit processes the echo signal and calculates the actual radial distance between the transducer and the inner wall of the sleeve. Step S5: Adjust the radial distance of the pulse echo transducer: Compare the actual radial distance with the preset initial distance to obtain the distance correction value. Based on this, the main control circuit controls the push rod motor to drive the adjusting piston to move radially, adjust the extension position of the pulse echo transducer, and restore its radial distance to the preset value, thereby ensuring that the amplitude of the echo signal mainly reflects the sleeve condition rather than the attenuation difference caused by the spacing fluctuation.

[0049] The above steps can be repeatedly performed in real time and dynamically during downhole measurements, ensuring that the Lamb wave transducer assembly always operates at the optimal incident angle and the pulse echo transducer always maintains the optimal distance from the casing inner wall under any depth, temperature, and pressure conditions, thereby obtaining high-quality measurement signals. Through the combination of the above structures and methods, this embodiment achieves the following technical effects: First, by sensing temperature and pressure and dynamically adjusting the angle, the problem of reduced Lamb wave excitation efficiency caused by changes in well fluid sound velocity is solved; second, by dynamically adjusting pulse echo ranging and radial distance, the interference of instrument eccentricity on echo amplitude is eliminated; and third, by using modular strip design, drill string delivery measurement is realized, expanding the applicability of ultrasonic Lamb wave logging technology.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. In other embodiments, the number of Lamb wave receiving transducers may be one, two, or more, not limited to four; the angle adjustment component may also employ other forms of motor or hydraulic drive mechanisms; the radial distance adjustment component may also employ other forms of telescopic mechanisms. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0051] This embodiment utilizes a strip-type modular design, facilitating embedded installation within the drill string body and adapting to drill string delivery measurement methods. Through the coordinated operation of temperature and pressure sensors and the main control circuit, dynamic adjustment of the downhole Lamb wave angle is achieved, resolving the issue of Lamb wave signal quality degradation caused by changes in well fluid sound velocity. Real-time pulse echo ranging and radial distance adjustment eliminate the influence of instrument eccentricity on echo amplitude. Overall, this invention significantly improves the adaptability and measurement accuracy of ultrasonic Lamb wave logging.

[0052] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A downhole adjustable ultrasonic Lamb wave transducer strip, characterized in that, include Strip frame (1); An ultrasonic transducer assembly, mounted on the strip frame (1), includes an inclined Lamb wave transducer group and a vertically mounted pulse echo transducer. An angle adjustment component, connected to the Lamb wave transducer group, is used to adjust the transmission and reception angles of the Lamb wave transducer group; A radial distance adjustment component, connected to the pulse echo transducer, is used to adjust the radial position of the pulse echo transducer; Temperature sensor (12) and pressure sensor (13) are mounted on the strip frame (1); The main control circuit (11) is electrically connected to the temperature sensor (12), the pressure sensor (13), the ultrasonic transducer assembly, the angle adjustment assembly and the radial distance adjustment assembly, respectively; The main control circuit (11) is configured to control the angle adjustment component according to the signals of the temperature sensor (12) and the pressure sensor (13), and to control the radial distance adjustment component according to the echo signal of the pulse echo transducer.

2. The downhole adjustable ultrasonic Lamb wave transducer strip according to claim 1, characterized in that, The Lamb wave transducer group includes a transmitting transducer (2) and at least one receiving transducer (3).

3. The downhole adjustable ultrasonic Lamb wave transducer strip according to claim 2, characterized in that, The angle adjustment component synchronously and in the opposite direction adjusts the angles of the transmitting transducer (2) and the receiving transducer (3).

4. The downhole adjustable ultrasonic Lamb wave transducer strip according to claim 2, characterized in that, The number of receiving transducers (3) is four.

5. A downhole adjustable ultrasonic Lamb wave transducer strip according to claim 2, characterized in that, The angle adjustment assembly includes a dual-axis motor (5) and a first angle push rod (6) and a second angle push rod (7) driven by the dual-axis motor (5). The first angle push rod (6) is connected to the receiving transducer (3), and the second angle push rod (7) is connected to the transmitting transducer (2).

6. A downhole adjustable ultrasonic Lamb wave transducer strip according to claim 1, characterized in that, The radial distance adjustment assembly includes a push rod motor (8) and an adjusting piston (9), wherein the push rod motor (8) drives the adjusting piston (9) to move in order to change the radial extension distance of the pulse echo transducer.

7. The downhole adjustable ultrasonic Lamb wave transducer strip according to claim 1, characterized in that, The strip also includes a conduit (10) for accommodating wires connecting the various electrical components.

8. A downhole adjustable ultrasonic Lamb wave transducer strip according to claim 1, characterized in that, The main control circuit is also configured to: calculate the current well fluid velocity based on the well fluid velocity mathematical model according to the real-time temperature and pressure collected by the temperature sensor (12) and pressure sensor (13), calculate the optimal incident angle according to the law of sound wave refraction, and adjust the Lamb wave transducer group based on the optimal incident angle by controlling the angle adjustment component.

9. A downhole adjustable ultrasonic Lamb wave transducer strip according to claim 1, characterized in that, The main control circuit (11) is further configured to: calculate the actual radial distance between the transducer and the inner wall of the sleeve based on the echo signal received by the pulse echo transducer, compare the actual radial distance with the preset initial distance to obtain a distance correction value, and control the radial distance adjustment component to adjust the radial position of the pulse echo transducer based on the correction value.

10. A downhole adjustable ultrasonic Lamb wave measurement method, applied to the transducer strip according to any one of claims 1-9, characterized in that, Includes the following steps: Real-time downhole temperature and pressure are collected using temperature and pressure sensors; Calculate the current well fluid velocity based on the temperature and pressure, and calculate the optimal Lamb wave incident angle based on the well fluid velocity. Adjust the Lamb wave transducer group based on the optimal Lamb wave incident angle control angle adjustment component; The pulse echo transducer receives the pulse echo signal, and the actual radial distance between the transducer and the inner wall of the casing is calculated based on the echo signal. Based on the actual radial distance, the radial distance adjustment component is controlled to adjust the radial distance of the pulse echo transducer to a preset value.

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