A cement casing well cementing quality detection method based on a dual-mode SH guided wave

Abstract

The application provides a cement casing well cementing quality detection method based on a bimodal SH guided wave, and belongs to the technical field of electromagnetic ultrasonic nondestructive testing, and comprises the following steps: a cemented casing simulation test piece is prepared, an excitation transducer and two receiving transducers are arranged on the same horizontal plane in the cemented casing simulation test piece, an attenuation value generated by SH0 and SH1 modal guided waves propagating between the two receiving transducers is obtained, and attenuation curves of cement curing time and SH0 and SH1 modal guided wave attenuation values are respectively established; the attenuation threshold for judging the cementing quality is obtained according to the attenuation curves of SH0 and SH1 modal guided waves; the excitation transducer and the receiving transducer are arranged in the test piece according to the above operation, the attenuation value generated by SH0 and SH1 modal guided waves propagating between the two receiving transducers is obtained, the attenuation value is compared with the attenuation threshold, the cement casing well cementing quality detection is realized, and the problem of cementing quality detection of low-density cement is solved.

Description

Technical Field

[0001] This invention belongs to the field of non-destructive testing technology, specifically to a method for testing the cementing quality of cement casing wells based on dual-mode SH guided waves. Background Technology

[0002] After drilling, oil and gas wells require cement injection into the casing annulus for cementing. Cementing quality directly affects the well's lifespan, productivity, and overall exploration and development benefits. High-quality cementing leads to efficient and effective oil and gas exploration and development; poor quality cementing can cause inter-layer fluid cross-contamination, significantly increasing development costs and even damaging casings in regional oil and water wells, resulting in substantial economic losses for the oilfield. With the deepening of oil exploration and development, low-pressure and weak formations are increasingly encountered. To prevent cementing fluid loss and effectively protect oil and gas layers, low-density cement casing cementing is commonly used. Low-density cement slurry systems are gradually developing and improving to handle complex underground conditions and have become a primary technology for one-time backfill cementing in deep and ultra-deep wells. Cementing quality inspection is a crucial application area in sonic logging during oilfield development. Quasi-Lamb waves in the casing are typically used to evaluate the cement bonding quality. However, low-density cement usually requires the addition of weight-reducing agents, resulting in a density below 1.75 g / cm³. 3 Typically 1.30 g / cm³ 3 The acoustic impedance of cement stone is approximately 1.90 g / cm². 3 The acoustic impedance of low-density cement sheath is half that of conventional density cement sheath, which results in poorer acoustic coupling between the low-density cement sheath and the casing compared to conventional density cement sheath. This leads to deviations and even incorrect evaluations when using conventional density cement sheath well cementing quality evaluation standards. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a cementing quality inspection method for cement casing wells based on dual-mode SH guided waves. It relies on the acoustic energy loss between the casing and the cement bonded to the pipe to evaluate the cement-casing bonding quality, thereby solving the problem that acoustic impedance methods are difficult to use to detect the cementing quality of low-density cement that is similar to the acoustic impedance of mud.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for detecting cementing quality in cement-cased wells based on dual-mode SH guided waves, the specific steps of which are as follows:

[0005] S1. A cement-bonded sleeve simulation specimen was made. An excitation transducer and two receiving transducers were arranged on the same horizontal plane inside the cement-bonded sleeve simulation specimen. The attenuation value Att generated by the propagation of SH0 and SH1 mode guided waves between the two receiving transducers was obtained. Attenuation curves of cement curing time and attenuation value of SH0 and SH1 mode guided waves were established respectively.

[0006] S2 obtains the attenuation threshold for judging the cement bonding quality based on the attenuation curves of the SH0 and SH1 modal guided waves.

[0007] S3 arranges excitation transducers and receiving transducers in the test piece according to S1, and obtains the attenuation value Att generated by the propagation of SH0 and SH1 mode guided waves between the two receiving transducers. The attenuation value is compared with the attenuation threshold to realize the detection of cementing quality of cement casing wells.

[0008] Furthermore, in S1, a receiving transducer and an excitation transducer capable of exciting SH0 and SH1 mode guided waves are designed according to the size parameters of the test piece.

[0009] Furthermore, in S1, both the excitation transducer and the receiving transducer consist of a PPM array and a racetrack-shaped coil. The racetrack-shaped coil of the excitation transducer has a wire diameter of 0.2 mm and 80 turns; the racetrack-shaped coil of the receiving transducer has a wire diameter of 0.14 mm and 110 turns. The PPM array consists of magnet units with a width of 15 mm and two rows and two columns.

[0010] Furthermore, in S1, the excitation transducer and the receiving transducer are arranged circumferentially on the same horizontal plane inside the cement-bonded sleeve simulation specimen, and the angles between the two receiving transducers and the excitation transducer are 60° and 120°, respectively.

[0011] Furthermore, in S1, the cement-bonded sleeve consists of a sleeve, a clamp, and cement poured into the annulus between the sleeve and the clamp.

[0012] Furthermore, in S1, the formula for calculating the attenuation value Att is:

[0013]

[0014]

[0015] In the formula, A n and A f These are the envelope peak values ​​of the forward direct waves of the signals obtained from the two receiving transducers; L is the propagation distance between the 60° and 120° receiving points; D1 and D2 are the outer and inner diameters of the sleeve, respectively; rad is the radian difference between the 60° and 120° receiving points.

[0016] Furthermore, in S2, the cement curing time is divided into three periods: the cement slurry period, the cement gradually curing period, and the cement fully curing period, which correspond to three cases of cement bonding quality: no bonding, weak bonding, and good bonding, respectively.

[0017] Furthermore, in S2, the attenuation value ranges of the SH0 and SH1 modes corresponding to the cement slurry time period, the cement gradually solidifying time period, and the cement fully solidifying time period are obtained from the attenuation curve, thus obtaining the attenuation thresholds corresponding to the cement bonding quality.

[0018] Furthermore, in S2, the period from 0 to 3.5 hours is the cement slurry period, which is detected using SH0 or SH1 modal guided waves; the period from 4.5 hours to 8.5 hours is the cement gradually solidifying period, which is detected using SH1 modal guided waves; and the period after 16 hours is the cement fully solidifying period, which is detected using SH0 modal guided waves.

[0019] Furthermore, in S3, the excitation transducer and receiving transducer arranged in the test piece are moved to detect the attenuation value Att generated by the propagation of the SH0 and SH1 mode guided waves at different positions in the test piece between the two receiving transducers. The attenuation value is compared with the attenuation threshold to realize the detection of the cementing quality of the entire cement casing well.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] This invention provides a cementing quality inspection method for cemented casing wells based on dual-mode SH guided waves, which is used for cementing quality inspection in wells with low-density cemented casing, and has the following advantages:

[0022] 1. By installing excitation transducers and receiving transducers inside the casing, the excitation and reception of SH0 and SH1 mode guided waves can be performed directly inside the casing, solving the problem of large attenuation of acoustic waves in drilling fluid in the pulse echo detection method;

[0023] 2. By calculating the acoustic attenuation caused by the radiation of energy from SH0 and SH1 mode guided waves into the cement during propagation in the casing, attenuation curves of cement curing time and attenuation values ​​of SH0 and SH1 mode guided waves were established. Based on the correlation between cement curing time and cement bonding quality, cementing quality detection was realized, solving the problem that conventional acoustic impedance detection methods are difficult to detect cementing quality in low-density cement casing wells.

[0024] 3. This invention flexibly employs SH0 and SH1 dual-mode guided waves to determine the cement bonding quality, ensuring both accuracy and sensitivity in the detection. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the electromagnetic ultrasonic transducer structure described in this invention;

[0026] Figure 2 This is a schematic diagram of a simulated specimen of the cement-bonded sleeve described in this invention;

[0027] Figure 3This is a schematic diagram of the transducer arrangement scheme described in this invention;

[0028] Figure 4 This is a schematic diagram of the electromagnetic ultrasonic testing system described in this invention;

[0029] Figure 5 This is a wave train diagram of SHO mode guided wave signals received at different times at a 60° position as described in this invention;

[0030] Figure 6 This is a wave train diagram of SHO mode guided wave signals received at different times at the 120° position as described in this invention;

[0031] Figure 7 This is a wave train diagram of the SH1 mode guided wave signals received at different times at the 60° position as described in this invention;

[0032] Figure 8 This is a wave train diagram of SH1 mode guided wave signals received at different times at the 120° position as described in this invention;

[0033] Figure 9 This is a graph showing the attenuation curve of the SHO mode guided wave signal as described in this invention over time.

[0034] Figure 10 This is a graph showing the attenuation curve of the SH1 mode guided wave signal as described in this invention over time.

[0035] Figure 11 This is a flowchart of a cement casing well cementing quality inspection method based on dual-mode SH guided wave according to the present invention;

[0036] In the diagram: 1-PPM array, 2-racetrack-shaped coil, 3-clamp, 4-cement, 5-sleeve, 6-receiving transducer, 7-excitation transducer, 8-computer, 9-oscilloscope, 10-high-power pulse transmitter / receiver, 11-impedance matching network, 12-test device. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0038] like Figure 11 As shown, this invention provides a method for inspecting the cementing quality of cemented casing wells based on dual-mode SH guided waves, mainly including the following steps:

[0039] Step 1: Design and fabricate an electromagnetic ultrasonic transducer capable of exciting SH0 and SH1 mode guided waves according to the dimensional parameters of the test piece 12.

[0040] The electromagnetic ultrasonic transducer mainly consists of a PPM array 1 and a racetrack-shaped coil 2. The excitation transducer coil has a wire diameter of 0.2 mm and 80 turns; the receiving transducer coil has a wire diameter of 0.14 mm and 110 turns; the PPM array 1 is a periodic permanent magnet array, which consists of 2 rows and 2 columns of magnet units with a width of 15 mm.

[0041] In addition, it also includes accessories such as RF connectors, SMA to BNC interfaces, RF cables, and aluminum alloy housings.

[0042] Step 2: Prepare low-density cement according to the ratio and make a cement-bonded sleeve simulation specimen, which mainly consists of sleeve 5 and clamp 3. Then, slowly pour the prepared cement 4 into the annular space between sleeve 5 and clamp 3 to form a cement ring.

[0043] Step 3: Deploy the excitation and receiving transducers.

[0044] The electromagnetic ultrasonic transducer includes one excitation transducer 7 and two receiving transducers 6, forming a one-transmitter-two-receiver configuration. The excitation transducer 7 and the receiving transducers 6 are arranged circumferentially on the same horizontal plane inside the sleeve. The two receiving transducers 6 are arranged along one side of the excitation transducer 7, and the angles between the two receiving transducers 6 and the excitation transducer 7 are 60° and 120°, respectively.

[0045] Step 4: Conduct a curing monitoring experiment on low-density cement and measure the decay values ​​of SH0 and SH1 modes.

[0046] First, a high-power pulse transmitter / receiver 10 generates and amplifies four-cycle sinusoidal pulse signals with center frequencies of 100kHz and 230kHz, which are then transmitted to the excitation transducer 7 via the excitation end impedance matching network 11 to excite the SH0 and SH1 mode guided waves respectively.

[0047] Subsequently, the guided wave signal propagating along the sleeve wall is received by two receiving transducers 6, and after passing through the receiver impedance matching network 11, it is amplified by the internal amplifier of the high-power pulse transmitter / receiver 10, and further transmitted to the oscilloscope 9 and the computer 8 to complete the data acquisition.

[0048] Finally, the envelope peak values ​​of the forward direct wave signals received by the two receiving transducers 6 are extracted respectively, and the attenuation value Att generated when different modes of SH waves propagate between the two receiving transducers 6 is calculated using the following formula.

[0049]

[0050]

[0051] In the formula, A nand A f , respectively, are the envelope peak values ​​of the forward direct waves of the signals obtained from the two receiving transducers 6; L is the propagation distance between the 60° and 120° receiving points; D1 and D2 are the outer and inner diameters of the sleeve, respectively; rad is the radian difference between the 60° and 120° receiving points.

[0052] For cementing quality inspection in low-density cement-cased wells, the SH1 mode guided wave has a larger attenuation dynamic range than the SH0 mode, allowing for more detailed assessments of cementing quality. However, due to the larger attenuation of the SH1 mode, it may suffer from an unusable signal-to-noise ratio during inspection. In contrast, while the SH0 mode has a smaller attenuation dynamic range, the signal packet is consistently and clearly observable throughout the inspection process. Furthermore, the SH0 mode exhibits almost no dispersion, reducing the difficulty of signal analysis. Therefore, in practice, both modes of SH guided waves should be considered comprehensively for inspection.

[0053] Step 5: Monitor the curing process of low-density cement in the cement-bonded sleeve simulation specimen, and plot the SH guided wave attenuation curves of different modes to determine the curing state of the cement.

[0054] Repeat step four at regular intervals until the cement is completely cured. Finally, by fitting the attenuation curve of cement curing time versus attenuation value of SH guided wave in different modes, the curing state of cement in different time periods can be determined by analyzing the trend of the attenuation curve.

[0055] Since cement undergoes a process of shear modulus change from zero to high during its curing process, and SH guided waves only propagate in media with shear modulus, the change in the leakage attenuation value of SH guided waves in the sleeve can be directly reflected by analyzing the change in the shear modulus of low-density cement in the sleeve, thereby determining the curing state of the cement.

[0056] The cement curing process can generally be divided into three stages: cement slurry, cement gradually curing, and cement fully curing. The changing trends of the SH guided wave attenuation curve for each stage are as follows:

[0057] (1) First stage (slurry cement): The cement in this stage is mainly in slurry state and does not have shear modulus. Therefore, the energy of the SH guided wave does not leak into the cement. Its attenuation is mainly due to the natural attenuation of the guided wave propagating in the sleeve. The attenuation value of the SH guided wave in this stage is small and in a stable state.

[0058] (2) Second stage (cement gradually solidifies): During this stage, the shear modulus of the cement increases gradually from zero to something, which can support the propagation of SH guided waves in the cement; at the same time, the acoustic impedance difference between the cement and the sleeve gradually decreases, so the energy of the SH guided waves leaking into the cement in the received signal gradually increases, and the attenuation value of different modes of SH guided waves is on the trend of gradually increasing.

[0059] (3) Third stage (complete cement curing): During this stage, the shear modulus of cement basically reaches its maximum value, the acoustic impedance difference between cement and sleeve is the smallest, so the energy leaked into cement by SH waveguide is the most at this time, and the attenuation value of SH waveguide of different modes basically reaches its maximum value and tends to stabilize again.

[0060] Step 6: Determine the attenuation threshold for judging the quality of cement bonding.

[0061] The bonding quality between the cement ring and the outer wall of the casing can generally be measured by three conditions: no bonding, weak bonding, and good bonding. As seen in the cement curing process described in step five, the changes in cement properties during the process of slurry-gradual-complete curing correspond to the gradual improvement in the bonding quality between the cement and the casing. Therefore, the threshold ranges for determining whether low-density cement is unbonded, weakly bonded, or well-bonded can be defined by the ranges of SH guided wave attenuation values ​​corresponding to the three cement curing states determined in step five.

[0062] Step 7: Conduct cementing quality inspection on low-density cement-cased wells. Measure the attenuation value of the SH guided wave according to Steps 1, 3, and 4, and compare it with the threshold values ​​corresponding to different cementing conditions determined in Step 6 to determine the cementing quality of the casing at that location. Then, change the transducer position for scanning to complete the cementing quality inspection of the low-density cement-cased well.

[0063] This invention generates horizontal shear (SH) guided waves in SH0 and SH1 modes that propagate circumferentially within the casing by exciting transducer 7. During the circumferential propagation of the SH guided waves, energy is radiated to the cement outside the casing, and the amplitude is attenuated. The attenuated signal is received by the transducer, sampled and recorded by an oscilloscope, and then recorded in a computer. The magnitude of the signal amplitude attenuation is calculated, and the depth position of the transducer is changed to continue detection. Finally, the cement bonding condition of the cement outside the casing is evaluated by the attenuation values ​​at different depths.

[0064] The use of SH0 and SH1 dual-mode guided waves ensures detection accuracy and sensitivity; electromagnetic ultrasound replaces traditional piezoelectric methods to excite the ultrasonic guided waves in the sleeve, avoiding the use of coupling agents and making detection more flexible.

[0065] Preferably, the high-power pulse transmitter / receiver 10 can generate pulse signals, and the width, frequency and energy of the pulse signals are controllable. The center frequencies of the pulse signals are 100kHz and 230kHz, corresponding to the SH0 mode and SH1 mode, respectively. The high-power pulse transmitter / receiver can filter and amplify the echo signals.

[0066] To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to explain the solution.

[0067] Example 1

[0068] The experimental sleeve used is made of J55 steel, 800mm long, with an outer diameter of 220mm and an inner diameter of 200mm. The specific application process is as follows:

[0069] Step 1: Design and fabricate an electromagnetic ultrasonic transducer capable of exciting SH0 and SH1 mode guided waves based on the dimensional parameters of the sleeve being tested. It mainly consists of a racetrack-shaped coil and a periodic permanent magnet array, such as... Figure 1 As shown. The excitation transducer coil has a wire diameter of 0.2 mm and 80 turns; the receiving transducer coil has a wire diameter of 0.14 mm and 110 turns. The periodic permanent magnet array consists of magnet units arranged in two rows and two columns, each 15 mm wide.

[0070] Step Two: Prepare low-density cement according to the specified ratio and fabricate a cement-bonded sleeve simulation specimen. This specimen mainly consists of a sleeve and clamps. Low-density cement slurry (density 1.3 g / cm³) is prepared under the ambient temperature and pressure conditions in a laboratory. 3 Then, the prepared cement grout is slowly poured into the annulus between the sleeve and the clamp. During filling, the grout is slowly stirred to remove a large amount of residual air in the gap. The completed simulated specimen is shown below. Figure 2 As shown.

[0071] Step 3: Deploy the excitation and receiving transducers. Use three electromagnetic ultrasonic transducers (T, R1, R2) to form a one-transmitter, two-receiver configuration. Arrange the probes circumferentially on the same horizontal plane inside the casing. The two receiving probes (R1, R2) are positioned along one side of the excitation probe (T), with angles of 60° and 120° between them and the excitation probe (T), respectively. (See details...) Figure 3 As shown.

[0072] Step 4: Conduct a curing monitoring experiment on low-density cement and measure the attenuation values ​​of SH0 and SH1 modes. First, a high-power pulse transmitter / receiver generates and amplifies four-cycle sinusoidal pulse signals with center frequencies of 100kHz and 230kHz. These signals are transmitted to the excitation transducer (T) via an impedance matching network at the excitation end to excite the SH0 and SH1 mode guided waves, respectively. Then, the guided wave signals propagating along the sleeve wall are received by R1 and R2, and after passing through the receiver impedance matching network, they are amplified by the amplifier inside the high-power pulse transmitter / receiver. The data is then further transmitted to an oscilloscope and a computer for data acquisition. A schematic diagram of the experimental system is shown below. Figure 4 As shown; finally, the envelope peak values ​​of the forward direct wave signals received by R1 and R2 are extracted respectively, and the attenuation A produced by different modes of SH waves propagating between R1 and R2 is calculated using the following formula. tt .

[0073] Step 5: Monitor the curing process of low-density cement in the cement-bonded sleeve simulation specimen, and plot the SH guided wave attenuation curves of different modes to determine the curing state of the cement. Figures 5-8 These are the guided wave signals of modes SH0 and SH1 at different times within the cement-bonded steel pipe at 60° and 120° positions, obtained during the experiment. Figure 5 The SH0 mode guided wave signals received at different times at a 60° position. Figure 6 The SH0 mode guided wave signals received at different times at a 120° position are shown. Due to the influence of cement bonding, the signal amplitude received by the transducer is relatively strong from 0 to 8.5 hours; after 16 hours, the signal amplitude is significantly reduced compared to before, and only the positive guided wave signal can be clearly observed.

[0074] Figure 7 The SH1 mode guided wave signals received at different times at a 60° position. Figure 8 The SH1 mode guided wave signal received at the 120° position at different times. Similar to the SH0 mode, the amplitude of the SH1 mode signal decays less in the first 0-8.5 hours, but after 16 hours, the signal amplitude decays drastically, and it becomes difficult to observe a clear SH1 guided wave signal at the 120° position, resulting in a poor signal-to-noise ratio. After that, the signal amplitude remains basically unchanged.

[0075] The decay curves of the SH0 and SH1 modes of the steel pipe during the cementation process are as follows: Figure 9 , Figure 10 As shown, based on the changing trend of the decay curve, the entire process can be divided into three stages:

[0076] (1) Within 0-3.5h, the signal amplitudes of SH0 and SH1 mode guided waves are relatively large, the attenuation values ​​are relatively small, and they are both in a relatively stable state. This indicates that the attenuation characteristics of SH0 and SH1 mode guided waves are relatively consistent during this period, so they can both be used to determine the cement solidification state.

[0077] (2) Starting from 4.5h, the attenuation curve begins to show an increasing trend, and the attenuation value increases sharply during the period from 4.5h to 8.5h. Among them, the dynamic range of attenuation produced by the SH1 mode is larger than that of the SH0 mode, indicating that the SH1 mode guided wave is more sensitive to the change of cement shear modulus. This point is beneficial for making a more detailed judgment on the cement bonding quality of low-density cement. Therefore, the SH1 mode is mainly used to judge the cement curing state during this period.

[0078] (3) After 16 hours, the attenuation value basically reaches its maximum and the curve stabilizes again. Among them, the SH1 mode has the problem of being difficult to obtain due to excessive attenuation, and additional signal processing methods are required to increase the signal-to-noise ratio, thus increasing the difficulty of signal analysis. For the SH0 mode guided wave, although its attenuation value is small, the direct wave packet of the SH0 mode signal can still be clearly observed, and the SH0 mode has almost no dispersion, which can reduce the difficulty of signal analysis. Therefore, the SH0 mode is mainly used to determine the cement solidification state during this period.

[0079] Through the above analysis, the attenuation characteristics of the SH0 and SH1 mode guided waves can be comprehensively considered to reflect the changes in characteristic parameters during the cement curing process, thereby determining its curing state. Corresponding to the different time periods mentioned above, the cement curing process in the monitoring experiment can be divided into the following three stages:

[0080] (1) First stage (slurry cement): During the period of 0-3.5h, the energy of the SH0 or SH1 mode guided waves does not leak into the cement. Their respective attenuation is mainly due to the natural attenuation of the guided waves propagating in the steel pipe. At this time, the cement is mainly in the slurry state and there is no shear modulus.

[0081] (2) Second stage (start of curing - cement gradually curing): At 4.5h, the cement begins to cure and bond with the pipe, and the solid frame begins to connect, thus supporting the propagation of SH wave in the cement; between 4.5h and 8.5h, the cement gradually cures, the shear modulus gradually increases, the leakage energy of SH1 mode guided wave gradually increases, resulting in a gradual decrease in signal amplitude and a gradual increase in attenuation.

[0082] (3) Third stage (complete curing): After 16 hours, the amplitude of the SH0 mode guided wave drops to the minimum, and its attenuation value basically reaches the maximum value and both tend to stabilize again. This indicates that the energy leaked into the cement by the SH0 mode guided wave no longer increases, and the cement is completely cured.

[0083] Step Six: Determine the attenuation threshold for judging the quality of cementing. The bonding quality between the cement sheath and the casing outer wall can generally be measured by three main conditions: no bonding, weak bonding, and good bonding. As can be seen from the cement curing process described in Step Five, the changes in cement properties during the process of cement going through the slurry state - gradual curing - complete curing are equivalent to the process of the bonding quality between cement and casing gradually improving. Therefore, the threshold range for whether low-density cement is no bonding, weak bonding, or good bonding can be defined by the range of SH guided wave attenuation values ​​corresponding to the three cement curing states determined in Step Five. The range of SH guided wave attenuation values ​​corresponding to different bonding qualities is shown in Table 1.

[0084] Table 1. Range of SH waveguide attenuation values ​​corresponding to different bonding qualities.

[0085]

[0086] As shown in Table 1, in the actual process of low-density cement casing cementing quality inspection, SH0 mode guided waves can be used to detect and calculate the attenuation value at each inspection location. Based on the distribution range of the attenuation value, the following three situations can be identified:

[0087] (1) If the attenuation value of the SH0 mode is ≤100dB / m, it can be determined that the cement here is unbonded.

[0088] (2) If the attenuation value of the SH0 mode is ≥200dB / m, it can be determined that the cement is well bonded here;

[0089] (3) If the attenuation value of the SH0 mode is 100dB / m-200dB / m, the SH1 mode needs to be used again for testing and further judgment should be made on the type of weak cement bonding.

[0090] The technical features of this invention not described can be implemented by or using existing technology, and will not be repeated here. Of course, the above description is not a limitation of this invention, and this invention is not limited to the examples above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this invention should also be within the protection scope of this invention.

Claims

1. A method for detecting cementing quality in cement-cased wells based on dual-mode SH guided waves, characterized in that, The specific steps are as follows: S1. Prepare a cement-bonded sleeve simulation specimen. Place an excitation transducer (7) and two receiving transducers (6) on the same horizontal plane inside the cement-bonded sleeve simulation specimen. Obtain the attenuation value Att generated by the propagation of SH0 and SH1 mode guided waves between the two receiving transducers (6). Establish attenuation curves of cement curing time and attenuation value of SH0 and SH1 mode guided waves respectively. S2 obtains the attenuation threshold for judging the cement bonding quality based on the attenuation curves of the SH0 and SH1 modal guided waves. S3 arranges an excitation transducer (7) and a receiving transducer (6) in the test piece (12) according to S1, detects the attenuation value Att generated by the propagation of the SH0 and SH1 mode guided waves at different positions in the test piece between the two receiving transducers (6), compares the attenuation value with the attenuation threshold, and realizes the detection of the cementing quality of the entire cement casing well. In S1, the formula for calculating the attenuation value Att is: In the formula, A n and A f These are the envelope peak values ​​of the forward direct waves of the signals obtained from the two receiving transducers (6), respectively; L It is the propagation distance between the receiving points at 60° and 120°; D 1 and D 2 represents the outer diameter and inner diameter of the casing, respectively; rad The difference in radians between the 60° and 120° receiving points.

2. The method for detecting cementing quality in cement-cased wells based on dual-mode SH guided waves according to claim 1, characterized in that, In S1, a receiving transducer (6) and an excitation transducer (7) capable of exciting SH0 and SH1 mode guides are designed according to the size parameters of the test piece (12).

3. The method for detecting cementing quality in cement-cased wells based on dual-mode SH guided waves according to claim 1, characterized in that, In S1, both the excitation transducer (7) and the receiving transducer (6) are composed of a PPM array (1) and a racetrack-shaped coil (2). The racetrack-shaped coil (2) of the excitation transducer (7) has a wire diameter of 0.2 mm and 80 turns. The racetrack-shaped coil (2) of the receiving transducer (6) has a wire diameter of 0.14 mm and 110 turns. The PPM array (1) is composed of 2 rows and 2 columns of magnet units with a width of 15 mm.

4. The method for detecting cementing quality in cement-cased wells based on dual-mode SH guided waves according to claim 1, characterized in that, In S1, the excitation transducer (7) and the receiving transducer (6) are arranged circumferentially on the same horizontal plane inside the cement-bonded sleeve simulation specimen. The angles between the two receiving transducers (6) and the excitation transducer (7) are 60° and 120°, respectively.

5. The method for detecting cementing quality in cement-cased wells based on dual-mode SH guided waves according to claim 1, characterized in that, In S1, the cement-bonded sleeve consists of a sleeve (5), a clamp (3), and cement (4) poured into the annular space between the sleeve (5) and the clamp (3).

6. The method for detecting cementing quality in cement-cased wells based on dual-mode SH guided waves according to claim 1, characterized in that, In S2, the cement curing time is divided into three periods: the cement slurry period, the cement gradually curing period, and the cement fully curing period, which correspond to three cases of cement bonding quality: no bonding, weak bonding, and good bonding, respectively.

7. The method for detecting cementing quality in cement-cased wells based on dual-mode SH guided waves according to claim 6, characterized in that, In S2, the attenuation ranges of SH0 and SH1 mode guided waves corresponding to the cement slurry time period, the cement gradually solidifying time period, and the cement fully solidifying time period are obtained from the attenuation curve, which gives the attenuation threshold corresponding to the cement bonding quality.

8. The method for detecting cementing quality in cement-cased wells based on dual-mode SH guided waves according to claim 6, characterized in that, In S2, the period from 0 to 3.5 hours is the cement slurry period, which is detected using SH0 or SH1 modal guided waves; the period from 4.5 hours to 8.5 hours is the cement gradually solidifying period, which is detected using SH1 modal guided waves; and the period after 16 hours is the cement fully solidifying period, which is detected using SH0 modal guided waves.

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