A testing device and testing method for evaluating casing damage and cementing quality while drilling

Abstract

The application discloses a kind of while drilling casing damage and cementing quality evaluation testing device and testing method, improve the technical problem of low logging time, poor testing accuracy, difficult to realize cementing quality evaluation of cement sheath external interface.The device includes drill collar sub, ultrasonic probe and multiple ultrasonic transducers, the excitation frequency of ultrasonic probe can be adjusted by external control module;The center frequency of multiple ultrasonic transducers is different, and the center frequency increases in turn.The application can measure multiple thickness range casings, casing damage detection and cementing quality evaluation of internal and external interface of cement sheath can be realized in one logging, which can improve logging time and improve measurement accuracy.

Description

Technical Field

[0001] This invention belongs to the field of logging instrument technology, specifically relating to a testing device and method for evaluating casing damage and cementing quality while drilling. Background Technology

[0002] In offshore oil and gas resource development operations, casing damage detection and cementing quality evaluation have always played an important role in stabilizing and increasing oil and gas production. Currently, the ultrasonic pulse reflection method is usually used to detect casing wall thickness information, and by utilizing the attenuation of casing resonance waves, the cement acoustic impedance imaging curve of the inner interface of the cement sheath (the interface between the cement sheath and the casing) can also be obtained, thereby conducting cementing quality evaluation.

[0003] Currently, cable-mounted ultrasonic logging devices are widely used. They are lowered into the well via a cable, and then driven by a motor to rotate the logging device at high speed. At the same time, the ultrasonic probe is used to emit and receive ultrasonic signals to achieve casing damage detection and cementing quality evaluation.

[0004] However, current testing devices share a common characteristic: they are equipped with ultrasonic probes of a certain frequency, allowing evaluation of casing within a specific thickness range. However, if the casing thickness exceeds the coverage of this ultrasonic probe, a different matching probe must be used, and logging must be repeated. Therefore, the logging efficiency of such testing devices is relatively low.

[0005] In addition, for some severely corroded casings, the casing wall is very thin and the corresponding resonant frequency is very high. A single-frequency ultrasonic probe cannot cover a wide frequency range. Therefore, the accuracy of thickness measurement for severely corroded casings is relatively low.

[0006] Furthermore, to evaluate the outer interface of the cement sheath (the interface between the cement sheath and the formation), the excitation frequency of the ultrasonic probe must meet the resonant frequency of the casing so that the ultrasonic waves can penetrate the casing and enter the cement sheath. However, since the corrosion status of the casing cannot be determined, and the excitation frequency of the ultrasonic probe in related technologies is constant, a single well logging operation cannot evaluate the outer interface of the cement sheath.

[0007] It is evident that existing technologies suffer from drawbacks such as low logging efficiency, poor testing accuracy, and difficulty in evaluating the cementing quality at the outer interface of the cement sheath. Therefore, improving logging efficiency, enhancing testing accuracy, and achieving cementing quality evaluation at the outer interface of the cement sheath are of great significance for improving the exploration and development of oil and gas resources. Summary of the Invention

[0008] In order to solve all or some of the above problems, the purpose of this invention is to provide a testing device and method for evaluating casing damage and cementing quality while drilling, which can realize the evaluation of cementing quality at the outer interface of cement sheath, and also improve logging efficiency and testing accuracy.

[0009] In a first aspect, the present invention provides a testing apparatus for evaluating casing damage and cementing quality while drilling, comprising:

[0010] The drill collar short section is cylindrical in shape and is used for coaxial connection to the bottom end of the drill collar;

[0011] Multiple ultrasonic transducers are embedded on the outer surface of the drill collar subsection.

[0012] An ultrasonic probe is embedded on the outer surface of the drill collar subsection, and the excitation frequency of the ultrasonic probe can be adjusted by an external control module.

[0013] The ultrasonic probe and multiple ultrasonic transducers are evenly distributed along the circumference of the drill collar section, and the center frequencies of the multiple ultrasonic transducers are different and increase sequentially.

[0014] Optionally, the center frequency of the ultrasonic transducer is 50KHz to 650KHz, and the excitation frequency of the ultrasonic probe is 200KHz to 500KHz.

[0015] Optionally, a mud velocity probe is embedded on the inner surface of the drill collar sub, and the mud velocity probe is used to measure the speed of sound of ultrasonic waves propagating in the mud.

[0016] Optionally, the transmitting end of the mud acoustic velocity probe is an arc surface and flush with the inner surface of the drill collar sub, and the transmitting ends of both the ultrasonic transducer and the ultrasonic probe are planar.

[0017] Secondly, the present invention provides a testing method for evaluating casing damage and cementing quality while drilling, using the aforementioned testing apparatus, comprising the following steps:

[0018] S1, connect the testing device to the bottom of the drill collar, and bring the testing device into the wellbore through the drill collar;

[0019] S2 uses multiple ultrasonic transducers to transmit and receive their respective ultrasonic waves to achieve casing damage detection and cementing quality evaluation at the cement sheath interface.

[0020] S3 uses an ultrasonic probe to emit and receive its own ultrasonic waves to evaluate the cementing quality at the outer interface of the cement sheath.

[0021] S4, through the mud sound velocity probe, emits and receives its own ultrasonic waves to measure the speed of sound propagating in the mud.

[0022] S5, Measurement complete, retrieve the testing device.

[0023] Optionally, in S2, the multiple ultrasonic transducers are sequentially named A1, A2, A3 to A4. N And ultrasonic transducers A1 to A N The center frequencies increase sequentially, and the calculations are performed for ultrasonic transducers A1 to A2. N The maximum detectable thickness d of the casing max :

[0024] Ultrasonic transducers A1, A2, A3 to A4 were collected in a laboratory water tank. N The reflected echo spectrum curves were obtained, and then the ultrasonic transducers A1, A2, A3 to A3 were measured in the laboratory. N The frequency lower limit f1, f2, f3 to f, corresponding to a 50% decrease in the spectral amplitude value. N ;

[0025] According to the half-wave transmission formula d = c / 2f, where d is the sleeve thickness and c is the longitudinal wave velocity constant of the ultrasonic wave inside the sleeve, the ultrasonic transducers A1, A2, A3 to A... are obtained sequentially. N The maximum detectable casing thicknesses d1, d2, d3 to d N Based on the maximum detectable casing thickness of the ultrasonic transducer, it can be determined whether the ultrasonic transducer can be used for casing damage detection and cementing quality evaluation at the cement sheath interface.

[0026] Optionally, according to ultrasonic transducers A1, A2, A3 to A N The maximum detectable thickness of the casing is d1, d2, d3 to d N And the original thickness X of the sleeve, select the appropriate measurement mode:

[0027] Mode 1: If d2 < X ≤ d1, then ultrasonic transducers A1, A2, A3 to A N Working simultaneously;

[0028] Mode 2: If d3 < X ≤ d2, then ultrasonic transducers A2, A3 to A N Working simultaneously;

[0029] Mode 3: If d4 < X ≤ d3, then the ultrasonic transducers A3 to A N Working simultaneously;

[0030] And so on,

[0031] Pattern N: If d N+1 <X≤d N Then ultrasonic transducer A N Working alone.

[0032] Optionally, based on the selected measurement mode and the amplitude judgment criterion, a corresponding ultrasonic transducer can be selected for testing:

[0033] The amplitude judgment criterion is Amp_resonance is the amplitude of the resonant wave from the sheath, Amp_reflection is the amplitude of the reflected wave from the inner wall of the sheath, δ is the threshold parameter, and the ultrasonic transducers are A1, A2, A3 to A... N The calculation results are δ1, δ2, δ3 to δ N ;

[0034] If δ1 < δ, it proves that ultrasonic transducer A1 cannot meet the measurement requirements of sleeve thickness. In this case, ultrasonic transducer A2 is judged.

[0035] If δ2 < δ, it proves that ultrasonic transducer A2 cannot meet the measurement requirements of sleeve thickness. In this case, ultrasonic transducer A3 is judged.

[0036] And so on, until the δ of a certain ultrasonic transducer 某 When the value is greater than δ, the ultrasonic transducer is selected for testing, and the casing damage is detected and the cementing quality of the cement sheath interface is evaluated based on the test results of the ultrasonic transducer.

[0037] Optionally, in S3, the ultrasonic probe is B, and the minimum thickness dmin of the sleeve that the ultrasonic probe B can detect is calculated:

[0038] The reflected echo spectrum curve of ultrasonic probe B was obtained in a water tank in the laboratory. Then, the upper frequency limit f corresponding to a 50% decrease in the spectral amplitude value of ultrasonic probe B was measured in the laboratory. B Then, according to the half-wave transmission formula d = c / 2f, the minimum sleeve thickness d that the ultrasonic probe B can detect is obtained. B Based on the minimum detectable casing thickness of the ultrasonic probe, it can be determined whether the ultrasonic probe can perform cementing quality evaluation at the cement sheath outer interface.

[0039] Optionally, the excitation frequency of the ultrasonic probe B can be gradually adjusted by an external control module so that the excitation frequency of the ultrasonic probe B satisfies the average resonant frequency of the sleeve along the circumferential direction.

[0040] At the initial depth point, based on the sleeve thickness measured by the ultrasonic transducer at this depth point, the average sleeve thickness D_depth at the initial depth point is taken. 1 Then, based on the half-wave transmission formula d = c / 2f, calculate the sleeve resonant frequency F_depth corresponding to the average sleeve thickness. 1 At this point, the initial excitation frequency of the ultrasonic probe B is F_depth. 0And make the ultrasonic probe B measure at the initial depth point with the initial excitation frequency of F_depth0;

[0041] At the next depth point, based on the sleeve thickness measured by the ultrasonic transducer at this depth point, the average sleeve thickness D_depth at the current depth point is taken. 2 Then, based on the half-wave transmission formula d = c / 2f, calculate the sleeve resonant frequency F_depth corresponding to the average sleeve thickness. 2 At this point, the excitation frequency of the ultrasonic probe B at this depth point is adjusted to F_depth via the external control module. 1 And make the ultrasonic probe B at F_depth 1 The excitation frequency was measured at this depth point;

[0042] At the next depth point, based on the sleeve thickness measured by the ultrasonic transducer at this depth point, the average sleeve thickness D_depth at the current depth point is taken. 3 Then, based on the half-wave transmission formula d = c / 2f, calculate the sleeve resonant frequency F_depth corresponding to the average sleeve thickness. 3 At this point, the excitation frequency of the ultrasonic probe B at this depth point is adjusted to F_depth via the external control module. 2 And make the ultrasonic probe B at F_depth 2 The excitation frequency was measured at this depth point;

[0043] Similarly, the casing resonance frequency at the previous depth point is used as the excitation frequency of the ultrasonic probe B at the current depth point for testing, thereby evaluating the cementing quality at the outer interface of the cement sheath.

[0044] Optionally, the excitation frequency of the ultrasonic probe B can be dynamically adjusted in real time via an external control module, so that the excitation frequency of the ultrasonic probe B satisfies the resonant frequency at each position of the sleeve along the circumferential direction.

[0045] At the current depth point, based on the sleeve thickness measured by the ultrasonic transducer at this depth point, the sleeve thickness D_depth at each position of the current depth point is taken. i Then, based on the half-wave transmission formula d = c / 2f, calculate the sleeve resonant frequency F_depth corresponding to each position of the sleeve. i At this time, the excitation frequency F_depth of the ultrasonic probe B is adjusted in real time through the external control module, so that the excitation frequency F_depth of the ultrasonic probe B meets the requirements of the resonance frequency at each position of the sleeve.

[0046] At the next depth point, based on the sleeve thickness measured by the ultrasonic transducer at this depth point, the sleeve thickness D_depth at each position of the current depth point is taken. iThen, based on the half-wave transmission formula d = c / 2f, calculate the sleeve resonant frequency F_depth corresponding to each position of the sleeve. i At this time, the excitation frequency F_depth of the ultrasonic probe B is adjusted in real time through the external control module, so that the excitation frequency F_depth of the ultrasonic probe B meets the requirements of the resonance frequency at each position of the sleeve.

[0047] Similarly, based on the casing thickness D_depth at each location of the current depth point, the excitation frequency F_depth of the ultrasonic probe B is adjusted in real time through the external control module, and the ultrasonic probe B with the excitation frequency adjusted in real time is used for testing, thereby evaluating the cementing quality of the cement sheath outer interface.

[0048] Optionally, in S4, the ultrasonic velocity V in the mud is obtained based on the echo arrival time T1 of the mud sound velocity probe and the inner diameter L of the drill collar sub. Then, the distance S1 between the ultrasonic transducer and the inner wall of the casing can be obtained based on the echo arrival time T2 of the ultrasonic transducer and the ultrasonic velocity V. The inner diameter S2 of the casing is equal to the inner diameter L of the drill collar sub + the distance S1 between the ultrasonic transducer and the inner wall of the casing + the wall thickness of the drill collar sub.

[0049] When the test results of the casing damage detection show that the casing is corroded, if the inner diameter S2 of the casing is smaller than the original inner diameter X of the casing, it is determined that the inner surface of the casing is corroded. If the inner diameter S2 of the casing is not much different from the original inner diameter X of the casing, it is determined that the outer surface of the casing is corroded.

[0050] As can be seen from the above technical solution, the testing device and method for evaluating casing damage and cementing quality while drilling provided by the present invention have the following advantages:

[0051] This device employs multiple ultrasonic transducers with different center frequencies, expanding the detection range of the testing equipment. A single logging operation can acquire casing thickness and cement bond quality curves across the entire frequency domain, enabling casing damage detection and cement sheath interface cementing quality evaluation in a single operation, significantly improving logging efficiency. Simultaneously, by setting a dynamically adjustable ultrasonic probe, the excitation frequency can be adjusted to meet the casing resonance frequency requirements, allowing more ultrasonic energy to penetrate the cement sheath. This results in stronger reflected echoes from the outer interface of the cement sheath, enabling evaluation of the cement sheath bonding quality in a single logging operation, improving both logging efficiency and testing accuracy. Furthermore, this design incorporates the measurement of the ultrasonic velocity propagating in the mud. The casing inner diameter can be calculated based on the mud velocity, and by comparing the measured inner diameter with the original inner diameter, corrosion on the inner or outer surface of the casing can be determined. This convenient testing method significantly improves operational efficiency.

[0052] Other features and advantages of the present invention will be set forth in the following description. Attached Figure Description

[0053] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation on the technical solutions of the present invention.

[0054] Figure 1 This is a schematic diagram of the overall structure of Embodiment 1 of the present invention;

[0055] Figure 2 This is a cross-sectional view of the logging device in Embodiment 1 of the present invention;

[0056] Figure 3 This is a schematic diagram of the logging device entering the well in Embodiment 1 of the present invention;

[0057] Figure 4 This is a cross-sectional view of the drill collar subsection in Embodiment 1 of the present invention;

[0058] Figure 5 This is a schematic diagram of the mud sound velocity probe in Embodiment 1 of the present invention;

[0059] Figure 6 This is a cross-sectional view of the mud sound velocity probe in Embodiment 1 of the present invention;

[0060] Figure 7 This is a cross-sectional view of the ultrasonic transducer in Embodiment 1 of the present invention;

[0061] Figure 8 This is a schematic diagram of the well logging device during testing in Embodiment 2 of the present invention;

[0062] Figure 9 This is a schematic diagram of the excitation spectrum curve of the ultrasonic transducer in Embodiment 2 of the present invention;

[0063] Figure 10 This is a schematic diagram of the excitation spectrum curve of the ultrasonic probe in Embodiment 2 of the present invention;

[0064] Figure 11 The waveform and its spectrum curve measured by ultrasonic transducer A1 in Embodiment 2 of the present invention;

[0065] Figure 12 The waveform and its spectrum curve measured by ultrasonic transducer A2 in Embodiment 2 of the present invention;

[0066] Figure 13 The waveform and its spectrum curve measured by ultrasonic transducer A3 in Embodiment 2 of the present invention;

[0067] Figure 14This is a flowchart illustrating the determination process for Mode 1 in Embodiment 2 of the present invention.

[0068] Figure 15 This is a flowchart illustrating the determination of Mode 2 in Embodiment 2 of the present invention;

[0069] Figure 16 This is a flowchart of the judgment process for mode 3 in embodiment 2 of the present invention;

[0070] Figure 17 The image shows the excitation waveform and spectrum curve of the ultrasonic probe B in Embodiment 2 of the present invention.

[0071] Figure 18 This is a waveform diagram of the ultrasonic pulse reflection echo of ultrasonic probe B in Embodiment 2 of the present invention;

[0072] Figure 19 This is a waveform diagram of the ultrasonic pulse reflection echo of the mud sound velocity probe in Embodiment 2 of the present invention.

[0073] Explanation of reference numerals in the attached figures:

[0074] 1. Drill collar sub; 2. Ultrasonic probe; 3. Ultrasonic transducer; 4. Blockage; 5. Mud velocity probe;

[0075] 100. Testing device; 200. Water eye; 300. Casing; 400. Cement ring; 500. Inner interface of cement ring; 600. Outer interface of cement ring; 700. Formation. Detailed Implementation

[0076] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be arbitrarily combined with each other.

[0077] like Figures 1 to 7 The image shows Embodiment 1 of the present invention, which discloses a testing device for evaluating casing damage and cementing quality while drilling. The device includes a cylindrical drill collar sub 1, which is coaxially connected to the bottom end of the drill collar. The drill collar sub 1 can also be a part of the drill collar, that is, the drill collar sub 1 is integrally formed and connected with the drill collar. The purpose is to ensure that the testing device can rotate and move forward and backward in the wellbore along with the drill collar, thereby realizing logging while drilling operations.

[0078] In one embodiment, such as Figure 1 , Figure 2 , Figure 3As shown, an ultrasonic probe 2 and multiple ultrasonic transducers 3 are embedded on the outer surface of the drill collar section 1. The ultrasonic probe 2 and multiple ultrasonic transducers 3 are located on the same plane and are evenly distributed along the circumference of the drill collar section 1. The excitation frequency of the ultrasonic probe 2 can be adjusted by an external control module, and the center frequencies of the multiple ultrasonic transducers 3 are different and increase sequentially.

[0079] In this embodiment, only the state of three ultrasonic transducers 3 is shown, that is, the ultrasonic probe 2 and the three ultrasonic transducers 3 are distributed at 90° intervals on the drill collar sub 1. Of course, if the number of ultrasonic transducers 3 is five, then the ultrasonic probe 2 and the five ultrasonic transducers 3 are distributed at 60° intervals on the drill collar sub 1, but this will not be elaborated further here.

[0080] The testing device for evaluating casing damage and cementing quality in this embodiment employs multiple ultrasonic transducers 3 with different center frequencies, resulting in a wider detection range. A single logging operation can acquire casing thickness and cement bonding quality curves across the entire frequency domain, enabling casing damage detection and cement sheath interface 500 cementing quality evaluation in a single operation, significantly improving logging efficiency. Furthermore, the ultrasonic probe 2, with its dynamically adjustable excitation frequency, satisfies the casing resonance frequency requirement, allowing ultrasonic energy to penetrate the cement sheath 400 as completely as possible. This results in a strong reflected echo from the cement sheath outer interface 600, allowing for evaluation of the cement sheath bonding quality in a single logging operation. This improves both logging efficiency and testing accuracy.

[0081] In one embodiment, such as Figure 2 , Figure 3 As shown, the center frequency of ultrasonic transducer 3 is 50kHz to 650kHz, and the excitation frequency of ultrasonic probe 2 is 200kHz to 500kHz. In this embodiment, the center frequencies of the three ultrasonic transducers 3 are 200kHz, 350kHz, and 500kHz, respectively, with a -6dB relative bandwidth of approximately 80%. The initial excitation frequency of ultrasonic probe 2 is 350kHz, and its -6dB relative bandwidth is approximately 120%. Therefore, the bandwidth of ultrasonic probe 2 is wider than that of ultrasonic transducer 3, which is beneficial for the ultrasonic energy emitted by ultrasonic probe 2 to completely penetrate the cement sheath 400, thereby improving the accuracy of the cementing quality evaluation of the outer interface 600 of the cement sheath.

[0082] In other embodiments, the center frequency of the ultrasonic transducer 3 and the excitation frequency of the ultrasonic probe 2 may be other ranges and other values, which can be adjusted according to the thickness of the sleeve 300 or the actual working needs, and will not be listed in detail here.

[0083] In one embodiment, such as Figure 1 , Figure 4 As shown, a mud velocity probe 5 is embedded on the inner surface of the drill collar sub 1, and the mud velocity probe 5 is used to measure the speed of sound of ultrasonic waves propagating in the mud. By measuring the speed of sound of the ultrasonic waves, the distance between the ultrasonic transducer 3 and the inner wall of the casing 300 can be calculated, and the inner diameter of the casing 300 can be calculated from this distance. If the casing damage detection shows that the casing 300 is corroded, by comparing the measured inner diameter of the casing with the original inner diameter of the casing, it can be determined whether the inner or outer wall of the casing 300 is corroded. The specific testing method is described in detail in Example 2.

[0084] In one embodiment, such as Figure 1 , Figure 4 As shown, the mud velocity probe 5 and the ultrasonic transducer 3 are not in the same plane, and the mud velocity probe 5 is located between two adjacent ultrasonic transducers 3, or between the ultrasonic probe 2 and the adjacent ultrasonic transducer 3.

[0085] In one embodiment, such as Figure 5 , Figure 6 , Figure 7 As shown, the transmitting end of the mud acoustic velocity probe 5 is an arc surface and flush with the inner surface of the drill collar sub 1. This ensures that the transmitting end of the mud acoustic velocity probe 5 is less susceptible to erosion when the mud flows in the water hole 200 inside the drill collar sub 1. Meanwhile, the transmitting ends of both the ultrasonic transducer 3 and the ultrasonic probe 2 are planar, which facilitates the transmission of ultrasonic energy through the sleeve 300 and the cement sheath 400.

[0086] In one embodiment, such as Figure 1 , Figure 4 As shown, the mud velocity probe 5 can be installed by drilling a hole in the drill collar sub 1, embedding the mud velocity probe 5 into one end of the hole, and installing a plug 4 at the other end of the hole to prevent mud from entering the borehole. In other embodiments, a groove can be directly cut into the inner wall of the drill collar sub 1, and then the mud velocity probe 5 can be embedded in the groove. The excitation frequency of the mud velocity probe 5 is determined according to the inner diameter of the drill collar sub 1 (that is, the inner diameter of the water eye 200). If the inner diameter of the drill collar sub 1 is relatively large, a low-frequency mud velocity probe 5 is selected; conversely, a high-frequency mud velocity probe 5 is selected to improve the measurement accuracy of ultrasonic velocity.

[0087] As described above, the testing device in this embodiment can obtain the casing thickness and cement bond quality curves in the full frequency domain in a single logging operation. This allows for casing damage detection and cement sheath inner and outer interface cementing quality evaluation in a single logging operation, significantly improving logging efficiency and measurement accuracy. Furthermore, this design also includes the measurement of the sound velocity of ultrasonic waves propagating in the mud. Based on the mud sound velocity, the inner diameter of the casing 300 can be calculated. By comparing the measured inner diameter with the original inner diameter, corrosion on the inner or outer surface of the casing 300 can be determined. This convenient testing method greatly improves operational efficiency.

[0088] like Figures 8-19 The following is Embodiment 2 of the present invention, which discloses a testing method for evaluating casing damage and cementing quality while drilling. Using the testing apparatus 100 from Embodiment 1, the method includes the following steps:

[0089] S1, connect the test device 100 to the bottom of the drill collar, and bring the test device 100 into the wellbore through the drill collar. Then, drive the test device 100 to move synchronously by rotating and moving the drill collar forward and backward.

[0090] S2, through multiple ultrasonic transducers 3, transmits and receives their respective ultrasonic waves to realize casing damage detection and cement sheath interface 500 cementing quality evaluation.

[0091] S3, through ultrasonic probe 2, emits and receives its own ultrasonic waves to achieve 600 cementing quality evaluation at the outer interface of the cement annulus;

[0092] S4, through the mud sound velocity probe 5, emits and receives its own ultrasonic waves to realize the measurement of the sound velocity of ultrasonic waves propagating in mud.

[0093] S5, Measurement complete, test device 100 retrieved.

[0094] In one embodiment, such as Figure 9 As shown, in S2, the multiple ultrasonic transducers 3 are sequentially named A1, A2, A3 to A4. N And ultrasonic transducers A1 to A N The center frequencies increase sequentially, and the calculations are performed for ultrasonic transducers A1 to A2. N The maximum detectable thickness d of the casing max Based on the maximum casing thickness detectable by ultrasonic transducer 3, the following calculation method is used to determine whether ultrasonic transducer 3 can perform casing damage detection and cement sheath interface 500mm cementing quality evaluation:

[0095] First, ultrasonic transducers A1, A2, A3 to A4 were sampled in a water tank in the laboratory. NThe reflected echo spectrum curve is obtained, and the lower limit of frequency f1 corresponding to a 50% decrease in the spectrum amplitude value of ultrasonic transducer A1 is calculated. According to the half-wave transmission formula d = c / 2f, where d is the sleeve thickness and c is the longitudinal wave velocity constant of ultrasonic waves in the sleeve, the maximum sleeve thickness d1 that ultrasonic transducer A1 can detect is obtained.

[0096] Then, obtain the frequency f2 corresponding to the intersection of the reflected echo spectrum curves of ultrasonic transducer A1 and ultrasonic transducer A2, and use the half-wave transmission formula d=c / 2f to calculate the maximum sleeve thickness d2 that ultrasonic transducer A2 can detect.

[0097] Subsequently, the frequency f3 corresponding to the intersection of the reflected echo spectrum curves of ultrasonic transducers A2 and A3 is obtained. The maximum sleeve thickness d3 that ultrasonic transducer A3 can detect is obtained by using the half-wave transmission formula d = c / 2f.

[0098] By analogy, the ultrasonic transducer A is obtained. N-1 With ultrasonic transducer A N The frequency f corresponding to the intersection of the reflected echo spectrum curves N Using the half-wave transmission formula d = c / 2f, the ultrasonic transducer A is calculated. N Maximum detectable casing thickness d N At this point, based on the maximum detectable casing thickness of the ultrasonic transducer 3, it can be determined whether the ultrasonic transducer 3 can perform casing damage detection and cement sheath interface 500mm cementing quality evaluation.

[0099] In S2, based on the original thickness X of the sleeve 300 and the ultrasonic transducers A1, A2, A3 to A... N The maximum thickness of the detectable sleeve 300 is d1, d2, d3 to d N Select the appropriate measurement mode. The specific measurement modes are as follows:

[0100] Mode 1: If d2 < X ≤ d1, then ultrasonic transducers A1, A2, A3 to A N They need to work simultaneously;

[0101] Mode 2: If d3 < X ≤ d2, then ultrasonic transducers A2, A3 to A N They need to work simultaneously;

[0102] Mode 3: If d4 < X ≤ d3, then the ultrasonic transducers A3 to A N They need to work simultaneously;

[0103] And so on,

[0104] Pattern N: If d N+1 <X≤d NThen only ultrasonic transducer A is needed. N You can work alone.

[0105] Based on the original thickness of the casing 300, a suitable measurement mode is used to measure the casing 300, resulting in more accurate test data. This avoids subsequent work such as filtering out unnecessary data, which can improve both logging efficiency and test accuracy.

[0106] In one embodiment, such as Figure 14 , Figure 15 , Figure 16 As shown, in S2, based on the selected measurement mode and the amplitude judgment criterion, the corresponding ultrasonic transducer 3 is selected for testing. The specific judgment criterion is as follows:

[0107] The amplitude judgment criterion is Amp_resonance is the amplitude of the resonant wave from the sheath, Amp_reflection is the amplitude of the reflected wave from the inner wall of the sheath, and δ is a threshold parameter, typically 0.01. Calculate the amplitudes of ultrasonic transducers A1, A2, A3 to A... N The results are δ1, δ2, δ3 to δ N ;

[0108] If δ1 < δ, it proves that ultrasonic transducer A1 cannot meet the measurement requirements of sleeve thickness. In this case, ultrasonic transducer A2 is judged.

[0109] If δ2 < δ, it proves that ultrasonic transducer A2 cannot meet the measurement requirements of sleeve thickness. In this case, ultrasonic transducer A3 is judged.

[0110] And so on, until the δ of a certain ultrasonic transducer 3 某 When the value is greater than δ, the ultrasonic transducer 3 is selected for testing. Based on the test results of the ultrasonic transducer 3, the casing damage is detected and the quality of the cement ring inner interface 500 is evaluated. If all ultrasonic transducers 3 fail to meet the requirements, it is determined that the test cannot be performed.

[0111] When the ultrasonic transducer 3 is working, an ultrasonic pulse signal is first excited to the ultrasonic transducer 3. The sound pulse signal propagates in the fluid and then enters the inner wall of the sleeve 300. At this time, most of the sound wave energy is reflected back and received by the ultrasonic transducer 3. The first wave is the reflected waveform of the ultrasonic wave on the inner wall of the sleeve 300. The amplitude of the reflected wave can be used to detect the corrosion of the inner surface of the sleeve 300.

[0112] The residual acoustic energy after the ultrasound wave is reflected by the inner wall of the casing 300 enters the casing 300. The acoustic pulse signal undergoes multiple reflections between the casing 300 and the cement ring 400 (inner interface 500 of the cement ring) and between the cement ring 400 and the surface of the formation 700 (outer interface 600 of the cement ring). At each surface, some energy is reflected and some energy propagates out; the magnitude of the energy is determined by the difference in acoustic impedance between the two materials.

[0113] Since the acoustic impedance of the sleeve 300 and the fluid are constant, the signal inside the sleeve 300 attenuates at a certain rate, and the magnitude of the signal depends on the acoustic impedance of the material outside the sleeve 300. The greater the acoustic impedance of the material outside the sleeve 300, the smaller the amplitude of the resonant wave inside the sleeve 300; conversely, the smaller the acoustic impedance of the material outside the sleeve 300, the greater the amplitude of the resonant wave inside the sleeve 300.

[0114] Therefore, the intensity of the resonant wave amplitude of the sleeve can be used to evaluate the acoustic impedance of the material outside the sleeve 300, and thus evaluate the cement bonding quality of the sleeve 300 (cement ring inner interface 500). Simultaneously, the thickness of the sleeve 300 can be evaluated using the sleeve resonant wave and the longitudinal wave propagation velocity of the sound wave within the sleeve.

[0115] In one embodiment, such as Figure 10 As shown in Figure S3, ultrasonic probe 2 is designated as B. The minimum casing thickness dmin that ultrasonic probe B can detect is calculated to determine whether ultrasonic probe 2 can perform cementing quality evaluation at the 600mm cement sheath interface. The specific calculation method is as follows:

[0116] First, the reflected echo spectrum curve of ultrasonic probe B was obtained in a water tank in the laboratory. Then, the upper frequency limit f corresponding to a 50% decrease in the spectral amplitude value of ultrasonic probe B was measured in the laboratory. B Then, according to the half-wave transmission formula d = c / 2f, the minimum sleeve thickness d that the ultrasonic probe B can detect is obtained. B Based on the minimum detectable casing thickness of ultrasonic probe 2, it can be determined whether ultrasonic probe 2 can perform cementing quality evaluation at the cement sheath outer interface of 600 mm.

[0117] There are two evaluation models for the cement sheath outer interface 600 cementing quality: one is the average value measurement method, and the other is the dynamic value measurement method, as detailed below:

[0118] (1) Average value measurement method

[0119] The excitation frequency of ultrasonic probe B is gradually adjusted by an external control module so that it satisfies the average resonant frequency of the casing 300 along the circumferential direction. In other words, as the drill collar rotates at a certain depth, the excitation frequency of ultrasonic probe B is adjusted according to the average resonant frequency of the casing 300 at that circumferential position, as detailed below:

[0120] At the initial depth point, based on all sleeve thicknesses measured by the ultrasonic transducer 3 at this depth point, the average sleeve thickness D_depth at the initial depth point is taken. 1 Then, based on the half-wave transmission formula d = c / 2f, calculate the sleeve resonant frequency F_depth corresponding to the average sleeve thickness. 1 At this point, the initial excitation frequency of the ultrasonic probe B is F_depth. 0 And make the ultrasonic probe B measure at the initial depth point with the initial excitation frequency of F_depth0;

[0121] At the next depth point, based on all the sleeve thicknesses measured by the ultrasonic transducer 3 at this depth point, the average sleeve thickness D_depth at the current depth point is taken. 2 Then, based on the half-wave transmission formula d = c / 2f, calculate the sleeve resonant frequency F_depth corresponding to the average sleeve thickness. 2 At this point, the excitation frequency of the ultrasonic probe B at this depth point is adjusted to F_depth via the external control module. 1 And make the ultrasonic probe B at F_depth 1 The excitation frequency was measured at this depth point;

[0122] At the next depth point, based on all the sleeve thicknesses measured by the ultrasonic transducer 3 at this depth point, the average sleeve thickness D_depth at the current depth point is taken. 3 Then, based on the half-wave transmission formula d = c / 2f, calculate the sleeve resonant frequency F_depth corresponding to the average sleeve thickness. 3 At this point, the excitation frequency of the ultrasonic probe B at this depth point is adjusted to F_depth via the external control module. 2 And make the ultrasonic probe B at F_depth 2 The excitation frequency was measured at this depth point;

[0123] Similarly, the casing resonance frequency at the previous depth point is used as the excitation frequency of the ultrasonic probe B at the current depth point for testing, thereby evaluating the cementing quality of the 600mm cement sheath outer interface. Because the drill collar travels a relatively short distance each time, the variation range of the inner wall thickness of the casing 300mm is also relatively small. Therefore, the casing thickness at the next depth point can be approximately equal to the thickness at the current depth point, and the variation of the casing resonance frequency is also relatively small. Thus, using the casing resonance frequency at the previous depth point as the excitation frequency of the ultrasonic probe B at the current depth point can ensure that more ultrasonic waves penetrate the casing 300mm, thereby enabling the evaluation of the cementing quality of the 600mm cement sheath outer interface.

[0124] (2) Dynamic value measurement method

[0125] The excitation frequency of the ultrasonic probe B is dynamically adjusted in real time by an external control module, so that the excitation frequency of the ultrasonic probe B meets the resonant frequency of the casing 300 at each position along the circumferential direction. That is, as the drill collar rotates at a certain depth point, the excitation frequency of the ultrasonic probe B is dynamically adjusted in real time according to the resonant frequency of the casing 300 at each point along this circumference, as follows:

[0126] At the current depth point, based on the sleeve thickness measured by the ultrasonic transducer 3 at this depth point, the sleeve thickness D_depth at each position of the current depth point is taken. i Then, based on the half-wave transmission formula d = c / 2f, calculate the sleeve resonant frequency F_depth corresponding to each position of the sleeve 300. i At this time, the excitation frequency F_depth of the ultrasonic probe B is adjusted in real time through the external control module, so that the excitation frequency F_depth of the ultrasonic probe B meets the requirements of the resonance frequency at each position of the sleeve.

[0127] At the next depth point, based on the sleeve thickness measured by the ultrasonic transducer 3 at this depth point, the sleeve thickness D_depth at each position of the current depth point is taken. i Then, based on the half-wave transmission formula d = c / 2f, calculate the sleeve resonant frequency F_depth corresponding to each position of the sleeve 300. i At this time, the excitation frequency F_depth of the ultrasonic probe B is adjusted in real time through the external control module, so that the excitation frequency F_depth of the ultrasonic probe B meets the requirements of the resonance frequency at each position of the sleeve.

[0128] Similarly, based on the casing thickness D_depth at each location at the current depth point, the excitation frequency F_depth of the ultrasonic probe B is adjusted in real time via an external control module. Tests are then conducted using the ultrasonic probe B with its frequency adjusted in real time, thereby evaluating the cement sheath outer interface cementing quality at 600mm. Because the excitation frequency of the ultrasonic probe B can be dynamically adjusted, it ensures that all ultrasonic waves can penetrate the casing 300mm, thus improving the accuracy of the cement sheath outer interface cementing quality evaluation at 600mm.

[0129] like Figures 9-18 As shown, in order to clearly explain this embodiment, the following are detailed examples of this embodiment:

[0130] like Figure 9 , Figure 10 As shown, there are three ultrasonic transducers 3, namely ultrasonic transducers A1, A2, and A3. The corresponding frequencies of ultrasonic transducers A1, A2, and A3 are 200kHz, 350kHz, and 500kHz, respectively. The initial excitation frequency of ultrasonic probe B is 350kHz.

[0131] Therefore, the lower frequency limit f1 corresponding to a 50% decrease in the spectral amplitude value of ultrasonic transducer A1 is 119kHz. According to the half-wave transmission principle of ultrasound in the sleeve, the maximum sleeve thickness that ultrasonic transducer A1 can detect is d1 = 23.9mm, obtained from the half-wave transmission formula d = c / 2f.

[0132] The frequency f2 = 254.5 kHz corresponding to the intersection of the reflected echo spectrum curves of ultrasonic transducer A1 and ultrasonic transducer A2 is obtained. Using the same formula, the maximum sleeve thickness that ultrasonic transducer A2 can detect is d2 = 11.2 mm.

[0133] The frequency f3 = 411kHz corresponding to the intersection of the reflected echo spectrum curves of ultrasonic transducers A2 and A3 is obtained. Using the same formula, the maximum sleeve thickness that ultrasonic transducer A3 can detect is d3 = 6.9mm.

[0134] Calculate the upper frequency limit f corresponding to a 50% decrease in the amplitude of the ultrasonic probe B spectrum. B =705kHz, using the same formula, the minimum sleeve thickness d that the ultrasonic probe B can detect is obtained. B =4.0mm, therefore this case uses a 3-in-3 combination measurement mode with three ultrasonic transducers, which can cover casing thicknesses between 4.0-23.9mm in a single well run.

[0135] like Figure 11 , Figure 12 , Figure 13 , Figure 14As shown, if the actual thickness of the sleeve 300 to be measured is X = 13mm, but the actual thickness of the sleeve 300 has been severely corroded and has become 4mm, firstly determine that d2 < X ≤ d1, and mode 1 needs to be used for measurement, that is, the ultrasonic transducers A1, A2 and A3 work simultaneously.

[0136] According to the amplitude judgment criterion, Ultrasonic transducer A1 is Since δ1 < δ, ultrasonic transducer A1 cannot obtain the correct sleeve thickness. In this case, ultrasonic transducer A2 is evaluated.

[0137] Ultrasonic transducer A2 is Since δ2 < δ, ultrasonic transducer A2 cannot obtain the correct sleeve thickness. In this case, ultrasonic transducer A3 is evaluated.

[0138] Ultrasonic transducer A3 is Since δ3 > δ, ultrasonic transducer A3 can obtain the correct casing thickness. Therefore, casing damage detection and cement sheath inner interface 500 cementing quality evaluation are carried out based on the test results of ultrasonic transducer A3.

[0139] If the thickness of the sleeve 300 is 8.1 mm, then applying a Gaussian-modulated sine wave with a center frequency of 350 kHz and 11 cycles to the ultrasonic probe B will... Figure 17 As can be seen, the excitation signal has a very narrow bandwidth, thus the ultrasonic energy is highly concentrated and can penetrate the cement ring at a frequency of 400°. Figure 18 It can be seen that the wave with the strongest signal amplitude arrives first as the reflected wave from the inner wall of the casing, followed by the casing resonance wave, and finally the reflected wave from the interface between the cement sheath 400 and the formation 700 (the outer interface of the cement sheath 600). The cement sheath outer interface 600 can be used to evaluate the bonding quality of the cement sheath outer interface 600.

[0140] In one embodiment, such as Figure 19 As shown, in S4, the ultrasonic velocity V in the mud is calculated based on the echo arrival time T1 of the mud acoustic velocity probe 5 and the inner diameter L of the drill collar sub 1. Since the inner diameter L of the drill collar sub 1 is known, after the mud acoustic velocity probe 5 emits an ultrasonic signal to the other side of the water eye 200, the ultrasonic wave will be reflected on the inner wall of the water eye 200 on the other side, and then reflected again after hitting the surface of the mud acoustic velocity probe 5. Therefore, the ultrasonic signal will be reflected back and forth in the water eye 200. At this time, the propagation speed V of the ultrasonic wave in the mud can be calculated by using the peak arrival time T1 of any two reflected waves.

[0141] Similarly, the echo arrival time T2 of the ultrasonic transducer 3 is calculated, and then the distance S1 between the ultrasonic transducer 3 and the inner wall of the casing 300 can be obtained based on the echo arrival time T2 and the ultrasonic velocity V. Subsequently, the inner diameter L of the drill collar sub 1, the distance S1 between the ultrasonic transducer 3 and the inner wall of the casing 300, and the wall thickness of the drill collar sub 1 are superimposed to obtain the inner diameter S2 of the casing 300.

[0142] When the test results of the casing damage detection show that the casing 300 is corroded, if the inner diameter S2 of the casing is smaller than the original inner diameter X of the casing, it is determined that the inner surface of the casing 300 is corroded; if the inner diameter S2 of the casing is not much different from the original inner diameter X of the casing, it is determined that the outer surface of the casing 300 is corroded.

[0143] As described above, this testing method enables rapid and accurate measurement of casing thickness, thereby improving the precision of casing damage detection and the evaluation of the quality of the inner and outer interfaces of the cement sheath. Furthermore, the inner diameter of the casing (300mm) can be calculated based on the mud sound velocity. By comparing the measured inner diameter with the original inner diameter, it is possible to determine whether the corrosion is on the inner or outer surface of the casing. This convenient testing method significantly improves operational efficiency.

[0144] It should be noted that, unless otherwise stated, the technical or scientific terms used in this invention should have the ordinary meaning as understood by one of ordinary skill in the art.

[0145] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A testing method for evaluating casing damage and cementing quality while drilling, using a testing device, characterized in that, The testing apparatus includes: The drill collar short section (1) is cylindrical and is used for coaxial connection to the bottom end of the drill collar; Multiple ultrasonic transducers (3) are embedded on the outer surface of the drill collar section (1); An ultrasonic probe (2) is embedded on the outer surface of the drill collar section (1), and the excitation frequency of the ultrasonic probe (2) can be adjusted by an external control module. The ultrasonic probe (2) and multiple ultrasonic transducers (3) are evenly distributed along the circumference of the drill collar section (1), and the center frequencies of the multiple ultrasonic transducers (3) are different and increase sequentially. The center frequency of the ultrasonic transducer (3) is 50KHz~650KHz, and the excitation frequency of the ultrasonic probe (2) is 200KHz~500KHz. The inner surface of the drill collar short section (1) is embedded with a mud sound velocity probe (5), and the mud sound velocity probe (5) is used to measure the sound velocity of ultrasonic waves propagating in mud. The transmitting end of the mud sound velocity probe (5) is an arc surface and is flush with the inner surface of the drill collar short section (1). The transmitting ends of the ultrasonic transducer (3) and the ultrasonic probe (2) are both planar. The testing method includes the following steps: S1, connect the test device (100) to the bottom of the drill collar, and bring the test device (100) into the wellbore through the drill collar; S2, through multiple ultrasonic transducers (3) to transmit and receive their respective ultrasonic waves, realize casing damage detection and cementing quality evaluation of the cement sheath interface (500); S3, by transmitting and receiving its own ultrasonic waves through the ultrasonic probe (2), the cementing quality evaluation of the cement annulus outer interface (600) is realized; S4, by transmitting and receiving its own ultrasonic waves through the mud sound velocity probe (5), the speed of sound propagation of ultrasonic waves in mud is measured. S5, Measurement complete, test device (100) retrieved; In S2, multiple ultrasonic transducers (3) are sequentially named A1, A2, A3 to A4. N And ultrasonic transducers A1 to A N The center frequencies increase sequentially, and the calculations are performed for ultrasonic transducers A1 to A2. N The maximum detectable thickness d of the casing max : Ultrasonic transducers A1, A2, A3 to A4 were collected in a laboratory water tank. N The reflected echo spectrum curves were obtained, and then the ultrasonic transducers A1, A2, A3 to A3 were measured in the laboratory. N The frequency lower limit f1, f2, f3 to f, corresponding to a 50% decrease in the spectral amplitude value. N ; According to the half-wave transmission formula d=c / (2f), where d is the thickness of the sleeve (300) and c is the longitudinal wave velocity constant of the ultrasonic wave inside the sleeve (300), the ultrasonic transducers A1, A2, A3 to A are obtained sequentially. N Detectable sleeve (300) maximum thickness d1, d2, d3 to d N Based on the maximum detectable casing thickness of the ultrasonic transducer (3), it is determined whether the ultrasonic transducer (3) can perform casing damage detection and cementing quality evaluation of the cement sheath interface (500). In S3, the ultrasonic probe (2) is B. Calculate the minimum thickness dmin of the sleeve that the ultrasonic probe B can detect. In S3, the excitation frequency of the ultrasonic probe B is gradually adjusted by the external control module so that the excitation frequency of the ultrasonic probe B meets the average resonant frequency of the sleeve along the circumferential direction; or the excitation frequency of the ultrasonic probe B is dynamically adjusted in real time by the external control module so that the excitation frequency of the ultrasonic probe B meets the resonant frequency of each position of the sleeve along the circumferential direction.

2. The test method according to claim 1, characterized in that, According to ultrasonic transducers A1, A2, A3 to A N The maximum detectable thickness of the casing is d1, d2, d3 to d N And the original thickness X of the sleeve (300), select the appropriate measurement mode: Mode 1: If d2 < X ≤ d1, then ultrasonic transducers A1, A2, A3 to A N Working simultaneously; Mode 2: If d3 < X ≤ d2, then ultrasonic transducers A2, A3 to A N Working simultaneously; Mode 3: If d4 < X ≤ d3, then the ultrasonic transducers A3 to A N Working simultaneously; And so on, Pattern N: If d N+1 <X≤d N Then ultrasonic transducer A N Working alone.

3. The test method according to claim 2, characterized in that, Based on the selected measurement mode and the amplitude judgment criterion, the corresponding ultrasonic transducer (3) is selected for testing: The amplitude judgment criterion is <δ, where Amp_resonance is the amplitude of the resonant wave from the sheath, Amp_reflection is the amplitude of the reflected wave from the inner wall of the sheath, and δ is the threshold parameter. Ultrasonic transducers A1, A2, A3 to A... N The calculation results are δ1, δ2, δ3 to δ N ; If δ1 < δ, it proves that ultrasonic transducer A1 cannot meet the measurement requirements of sleeve thickness. In this case, ultrasonic transducer A2 is judged. If δ2 < δ, it proves that ultrasonic transducer A2 cannot meet the measurement requirements of sleeve thickness. In this case, ultrasonic transducer A3 is judged. And so on, until the δ of a certain ultrasonic transducer (3) 某 When the value is greater than δ, the ultrasonic transducer (3) is selected for testing, and the casing damage detection and cementing quality evaluation of the cement sheath interface (500) are carried out based on the test results of the ultrasonic transducer (3).

4. The test method according to claim 1, characterized in that, In S3, the minimum thickness dmin of the sleeve that the ultrasonic probe B can detect is calculated: the reflected echo spectrum curve of the ultrasonic probe B is obtained in a water tank in the laboratory, and then the upper frequency f corresponding to a 50% decrease in the spectral amplitude value of the ultrasonic probe B is measured in the laboratory. B Then, according to the half-wave transmission formula d=c / (2f), the minimum sleeve thickness d that the ultrasonic probe B can detect is obtained. B Based on the minimum detectable casing thickness of the ultrasonic probe (2), it is determined whether the ultrasonic probe (2) can perform cementing quality evaluation at the cement sheath outer interface (600).

5. The test method according to claim 4, characterized in that, The excitation frequency of ultrasonic probe B is gradually adjusted by an external control module so that the excitation frequency of ultrasonic probe B satisfies the average resonant frequency of the sleeve along the circumferential direction. At the initial depth point, based on the sleeve thickness measured by the ultrasonic transducer (3) at this depth point, the average sleeve thickness D_depth at the initial depth point is taken. 1 Then, based on the half-wave transmission formula d=c / (2f), the sleeve resonant frequency F_depth corresponding to the average thickness of the sleeve (300) is calculated. 1 At this point, the initial excitation frequency of the ultrasonic probe B is F_depth. 0 And make the ultrasonic probe B at F_depth 0 The initial excitation frequency is measured at the initial depth point; At the next depth point, based on the sleeve thickness measured by the ultrasonic transducer (3) at this depth point, the average sleeve thickness D_depth at the current depth point is taken. 2 Then, based on the half-wave transmission formula d=c / (2f), the sleeve resonant frequency F_depth corresponding to the average thickness of the sleeve (300) is calculated. 2 At this point, the excitation frequency of the ultrasonic probe B at this depth point is adjusted to F_depth via the external control module. 1 And make the ultrasonic probe B at F_depth 1 The excitation frequency was measured at this depth point; At the next depth point, based on the sleeve thickness measured by the ultrasonic transducer (3) at this depth point, the average sleeve thickness D_depth at the current depth point is taken. 3 Then, based on the half-wave transmission formula d=c / (2f), the sleeve resonant frequency F_depth corresponding to the average thickness of the sleeve (300) is calculated. 3 At this point, the excitation frequency of the ultrasonic probe B at this depth point is adjusted to F_depth via the external control module. 2 And make the ultrasonic probe B at F_depth 2 The excitation frequency was measured at this depth point; Similarly, the casing resonance frequency at the previous depth point is used as the excitation frequency of the ultrasonic probe B at the current depth point for testing, thereby evaluating the cementing quality of the cement sheath outer interface (600).

6. The test method according to claim 4, characterized in that, The excitation frequency of the ultrasonic probe B is dynamically adjusted in real time by an external control module, so that the excitation frequency of the ultrasonic probe B satisfies the resonant frequency at each position along the circumferential direction of the sleeve: At the current depth point, based on the sleeve thickness measured by the ultrasonic transducer (3) at this depth point, the sleeve thickness D_depth at each position of the current depth point is taken. i Then, based on the half-wave transmission formula d=c / (2f), calculate the sleeve resonant frequency F_depth corresponding to each position of the sleeve (300). i At this time, the excitation frequency F_depth of the ultrasonic probe B is adjusted in real time through the external control module, so that the excitation frequency F_depth of the ultrasonic probe B meets the requirements of the resonance frequency at each position of the sleeve. At the next depth point, based on the sleeve thickness measured by the ultrasonic transducer (3) at this depth point, the sleeve thickness D_depth at each position of the current depth point is taken. i Then, based on the half-wave transmission formula d=c / (2f), calculate the sleeve resonant frequency F_depth corresponding to each position of the sleeve (300). i At this time, the excitation frequency F_depth of the ultrasonic probe B is adjusted in real time through the external control module, so that the excitation frequency F_depth of the ultrasonic probe B meets the requirements of the resonance frequency at each position of the sleeve. Similarly, based on the casing thickness D_depth at each position of the current depth point, the excitation frequency F_depth of the ultrasonic probe B is adjusted in real time through the external control module, and the ultrasonic probe B with the excitation frequency adjusted in real time is used for testing, thereby evaluating the cementing quality of the cement sheath outer interface (600).

7. The test method according to claim 1, characterized in that, In S4, the ultrasonic velocity V in the mud is obtained based on the echo arrival time T1 of the mud sound velocity probe (5) and the inner diameter L of the drill collar short section (1). Then, the distance S1 between the ultrasonic transducer (3) and the inner wall of the casing (300) can be obtained based on the echo arrival time T2 of the ultrasonic transducer (3) and the ultrasonic velocity V. The inner diameter S2 of the casing (300) = the inner diameter L of the drill collar short section (1) + the distance S1 between the ultrasonic transducer (3) and the inner wall of the casing (300) + the wall thickness of the drill collar short section (1). When the test results of the casing damage detection show that the casing (300) is corroded, if the inner diameter S2 of the casing is smaller than the original inner diameter of the casing, it is determined that the inner surface of the casing (300) is corroded. If the inner diameter S2 of the casing is not much different from the original inner diameter of the casing, it is determined that the outer surface of the casing (300) is corroded.

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