Back lining structure, transducer for ultra-deep well and manufacturing method of transducer

Abstract

The invention provides a backing structure which can be applied to a transducer. The backing structure includes a first backing layer and a second backing layer. The first backing layer is of a cylindrical conical structure, a first groove is formed in the center of the bottom of the first backing layer, and the first groove is used for containing the piezoelectric layer; the second backing layer is of a columnar structure, a second groove is formed in the center of the bottom of the second backing layer, and the first backing layer is stacked at the bottom of the second backing layer through the second groove. The acoustic impedance of the backing structure is gradually reduced in a gradient change manner from the bottom of the first backing layer to the top of the second backing layer; the two backing layers are both used for absorbing sound waves transmitted backwards by the piezoelectric layer, and the laminated surfaces of the two backing layers are used for promoting absorption of the sound waves transmitted backwards by the piezoelectric layer. Through the double-cone angle design of the backing layer and the acoustic impedance design of gradient change, the attenuation of sound waves in the backing layer can be improved, so that the thickness vibration mode of the transducer is prominent, the working frequency band is widened, and the signal-to-noise ratio of pulse echo signals is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of acoustic transducers and well logging, and in particular to a backing structure, a transducer for ultra-deep wells and a manufacturing method thereof. Background Art

[0002] Fractured oil and gas reservoirs are the most common unconventional oil and gas reservoirs, characterized by their generally deep burial depth, complex lithologic structures, and uneven spatial distribution. Therefore, accurate identification and detection of reservoir fractures and pores is extremely important during unconventional oil and gas exploration and development. Ultrasonic imaging logging technology uses the differences in physical properties of different geological features between strata to image the wellbore. This technology can intuitively display geological features such as pores and fractures, enabling reservoir feasibility assessment and identification of drilling fluid loss layers in fractured oil and gas exploration. However, the extreme conditions in ultra-deep wells make the acquisition and identification of geological features in wellbore images more difficult, placing higher demands on the resolution, temperature resistance, and pressure resistance of ultrasonic imaging logging instruments.

[0003] As a key component of ultrasonic imaging logging instruments, ultrasonic transducers must possess a wide bandwidth, a high signal-to-noise ratio, and high-temperature and high-pressure resistance when used in ultra-deep wells. The backing layer is a crucial structural component of the ultrasonic transducer. Placed on the back of the piezoelectric element, it is typically made of a high-attenuation, high-impedance material to reduce the tail length of the piezoelectric element's excitation vibration, thereby achieving the ultrasonic transducer's wide bandwidth and high signal-to-noise ratio.

[0004] The sidewall ultrasonic imaging logging transducer described in patent application publication number CN 108386186 A (publication date: August 10, 2018) utilizes a cylindrical-conical backing. Under high-temperature and high-pressure conditions, the backing layer is a tightly compressed entity, which weakens the absorption and attenuation of sound waves within the backing. Therefore, the backing structure and materials need to be optimized and improved to improve sound absorption and attenuation within the backing layer. The ultrasonic transmitter-receiver device for ultrasonic imaging logging described in patent application publication number CN 118292863 A (publication date: July 5, 2024) encapsulates the transducer within a housing. This packaging approach presents certain technical challenges in terms of high-pressure resistance. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a backing structure, a transducer for ultra-deep wells and a manufacturing method thereof.

[0006] First aspect: The present invention provides a backing structure, which includes a first backing layer and a second backing layer. The first backing layer is a cylindrical conical structure with a first groove provided at the center of the bottom, and the first groove is used to accommodate the piezoelectric layer. The second backing layer is a cylindrical conical structure with a second groove provided at the center of the bottom, and the first backing layer is stacked on the bottom of the second backing layer through the second groove. The first backing layer and the second backing layer are both used to absorb the sound waves propagating backward from the piezoelectric layer, and the stacking surface of the first backing layer and the second backing layer is used to promote the absorption of the sound waves propagating backward from the piezoelectric layer. In addition, the acoustic impedance of the first backing layer is greater than the acoustic impedance of the second backing layer.

[0007] In one example, the stacked surface of the first backing layer and the second backing layer has a planar structure or a concave-convex structure.

[0008] In one example, the taper angle of the second backing layer is greater than the taper angle of the second backing layer.

[0009] In one example, the first backing layer and the second backing layer are both formed by mixing three materials: tungsten powder, rubber powder and epoxy glue, and the mass ratio of the rubber powder is less than 5%.

[0010] In one example, the first backing layer and the second backing layer have different mixing ratios of constituent materials, wherein the first backing layer has a higher mass ratio of tungsten powder than the second backing layer, and the first backing layer has a lower mass ratio of rubber powder than the second backing layer.

[0011] In one example, the tungsten powder in the mixed material of the first backing layer and the second backing layer is a mixture of tungsten powders of various particle sizes, wherein the small particle size of the tungsten powder ranges from 8.47 μm to 12.70 μm, the medium particle size ranges from 25.40 μm to 31.80 μm, and the large particle size ranges from 425 μm to 847 μm.

[0012] In one example, the first backing layer has a larger proportion of large-particle tungsten powder than the second backing layer.

[0013] In a second aspect, the present invention further provides a transducer for ultra-deep wells, wherein the transducer includes the backing structure described in the first aspect.

[0014] In one example, the transducer further includes a piezoelectric layer, a matching layer, and a housing. The piezoelectric layer is configured to transmit and receive ultrasonic waves and is accommodated in a first groove of the first backing layer. The matching layer is configured to enhance the forward ultrasonic waves generated by the piezoelectric layer and is located at the bottom of the piezoelectric layer. The housing is configured to encapsulate and protect the backing structure and piezoelectric layer. The housing is integrally formed with the matching layer and is cylindrically clad around the backing structure and piezoelectric layer.

[0015] In the third aspect, the present invention also provides a method for manufacturing a transducer for ultra-deep wells, which is used to manufacture the transducer described in the second aspect, using a high-temperature pressing process and an integrated packaging technology. The method includes: selecting a piezoelectric material as the piezoelectric layer, high-temperature pressing the first backing layer, high-temperature pressing the second backing layer, leading out the negative electrode wire of the piezoelectric layer, applying high-temperature pressure to bond the piezoelectric layer and the first backing layer, leading out the positive electrode wire of the piezoelectric layer, and using a high-temperature packaging method for the backing structure and the piezoelectric layer packaging shell.

[0016] The present invention utilizes a dual-cone angle design and gradient-varied acoustic impedance within the backing layer to enhance acoustic wave attenuation within the backing layer, thereby emphasizing the transducer's thickness vibration mode, broadening the operating frequency band, and enhancing the pulse-echo signal-to-noise ratio. During actual transducer fabrication, the backing layer and piezoelectric layer are prepared using a high-temperature pressing process, and integrated packaging technology is employed to enhance the ultrasonic transducer's resistance to high temperatures and high voltages. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0018] Figure 1 A cross-sectional view of a transducer backing structure provided by an embodiment of the present invention;

[0019] Figure 2 A cross-sectional view of a second backing of a transducer provided by an embodiment of the present invention;

[0020] Figure 3 A cross-sectional view of a transducer provided by an embodiment of the present invention;

[0021] Figure 4 The present invention provides a flow chart of a method for manufacturing a transducer. DETAILED DESCRIPTION

[0022] In existing technologies, acoustic logging transducers are a key component of logging instruments used in geological exploration and reservoir development. They detect the physical properties of underground formations by transmitting and receiving acoustic waves. The backing layer is a crucial component in the design of acoustic logging transducers. Its primary function is to absorb acoustic waves reflected from the rear of the piezoelectric material (typically the core element of the transducer, responsible for generating acoustic waves), thereby reducing the interference of these reflected waves on the forward-propagating acoustic waves and improving measurement accuracy.

[0023] In order to attenuate as much sound wave energy as possible within a limited space, the backing layer is usually designed in a cylindrical or cylindrical cone shape. This design increases the distance that sound waves propagate within the backing material, allowing more sound wave energy to be absorbed before reaching the boundary of the backing layer. This can improve sound wave attenuation under conditions of limited thickness and reduce possible interference of reflected echoes on the signal. The backing material is generally made of tungsten powder-epoxy composite material, which has a high acoustic impedance that matches the piezoelectric material, allowing the sound waves excited by the piezoelectric material to smoothly enter the backing layer. Although the tungsten powder-epoxy composite material itself already has good sound wave absorption properties, sometimes in order to further enhance its sound absorption effect, hollow glass microspheres are added to the tungsten powder-epoxy material to improve the sound wave absorption in the backing layer. However, the backing containing hollow glass microspheres is fragile in a high-pressure environment, causing changes in the performance of the ultrasonic transducer.

[0024] Figure 1 This is a schematic diagram of a backing structure provided in an embodiment of the present application. Figure 1 As shown, the backing structure 110 includes a first backing layer 111 and a second backing layer 112 . The first backing layer 111 is stacked on the bottom of the second backing layer 112 . The backing structure 110 is used to absorb the sound waves propagating backward from the piezoelectric layer.

[0025] Specifically, refer to Figure 1 The first backing layer 111 may be a cylindrical-conical structure. Geometrically, the cylindrical-conical structure may be considered to be composed of a cylindrical structure portion and a conical structure portion, wherein the top surface of the cylindrical structure portion and the bottom surface of the conical structure portion are in the same plane.

[0026] A first groove 113 may be provided at the bottom center of the first backing layer 111 , and the first groove 113 may be used to accommodate the piezoelectric layer.

[0027] Combine Figure 2 The second backing layer 112 also has a cylindrical-conical structure. A second groove 118 is provided at the center of the bottom of the second backing layer 112. The second groove 118 allows the first backing layer 111 to be laminated onto the bottom of the second backing layer 112. It is easy to understand that a laminated surface exists between the first backing layer 111 and the second backing layer 112.

[0028] The acoustic impedance of the backing structure 110 decreases gradually from the bottom of the first backing layer 111 to the top of the second backing layer 112. Furthermore, the acoustic impedance range of the first backing layer is preferably 1.0×10 7 to 2.3×10 7 Pa·s / m, and its acoustic impedance decreases from the first groove 113 to the cone tip. The acoustic impedance range of the second backing layer 112 is preferably 0.3×10 7 to 1.0×10 7Pa·s / m, and the acoustic impedance decreases from the second groove 118 toward the cone tip and from the center toward the outer diameter.

[0029] It should be further understood that the sound waves excited by the piezoelectric layer mainly propagate along the axial direction of the transducer, in the direction away from the backing structure 110 (forward propagation), but also propagate along the axial direction of the transducer, in the direction toward the backing structure 110 (backward propagation). The sound waves propagating backward may be reflected back by objects such as the transducer housing, thereby interfering with the sound waves propagating forward, so the sound waves propagating backward can be absorbed by the first backing layer 111 and the second backing layer 112. In addition, the backward propagating sound waves can also be reflected and transmitted through the stacking surface between the first backing layer 111 and the second backing layer 112, which can increase the reflection path and cause the reflected waves to repeatedly attenuate in the two backing layers to promote the absorption of the backward propagating sound waves.

[0030] As can be seen from this example, by stacking two cylindrical-conical backing layers of different acoustic impedances, progressive impedance matching is used to maximize acoustic wave absorption efficiency. The stacked surface between the two backing layers can increase the interfacial reflection path of the sound wave at the stacked surface, enhancing the attenuation and absorption of the sound wave within the backing layer, preventing it from being reflected back to the piezoelectric element and superimposed on the forward sound wave, thereby reducing noise interference and improving the signal-to-noise ratio of the transducer. The tapered, non-uniform thickness structure of the backing structure 110 can avoid standing waves excited by uniform thickness backings, effectively achieving acoustic attenuation, and also expanding bandwidth through multiple resonances of different thicknesses.

[0031] In one example, the first backing layer 111 and the second backing layer 112 can be made of a mixture of tungsten powder, rubber powder and epoxy glue, with the weight ratio of the rubber powder being less than 5%. The rubber powder is high temperature resistant rubber powder, and the epoxy glue is high temperature resistant encapsulation glue.

[0032] It's worth noting that rubber is relatively soft and easily deforms under high pressure. Therefore, a relatively low mass ratio is set for the rubber powder, allowing it to more easily enter the gaps between the tungsten powder and the tungsten powder. The relatively hard tungsten powder protects the rubber powder, preventing deformation and further improving the high-pressure resistance of the backing structure 110. Otherwise, the significant mismatch in thermal expansion coefficients at high temperatures could cause internal stress failure. If the rubber powder is compacted or damaged under high temperature and high pressure, it could reduce the absorption of backward sound waves in the backing layer.

[0033] Based on the above example, the first backing layer 111 and the second backing layer 112 may have different mixing ratios of constituent materials. Specifically, the first backing layer 111 may have a higher mass ratio of tungsten powder than the second backing layer 112. Furthermore, the first backing layer 111 may have a lower mass ratio of rubber powder than the second backing layer 112.

[0034] Preferably, the mass ratio of tungsten powder, rubber powder, and epoxy adhesive in the first backing layer 111 is 40:1:6, and the mass ratio of tungsten powder, rubber powder, and epoxy adhesive in the second backing layer 112 is 30:1:3.

[0035] In this embodiment, due to the high density of tungsten powder and the low density of rubber powder, increasing the mass ratio of tungsten powder and decreasing the mass ratio of rubber powder can improve the acoustic impedance of the backing layer. The first backing layer 111 is in direct contact with the piezoelectric layer, and its acoustic impedance is designed to be the same as or slightly lower than that of the piezoelectric layer, facilitating smooth entry of backward sound waves into the first backing layer 111. The second backing layer 112 has a lower tungsten powder ratio and an increased rubber powder ratio, resulting in a lower acoustic impedance than the first backing layer 111. Sound waves are reflected and transmitted at the stacked surface. Reflected sound waves can be reflected multiple times within the first backing layer 111, while transmitted sound waves experience increased absorption and attenuation within the second backing layer 112, which contains a higher concentration of rubber powder.

[0036] In one example, the tungsten powder in the mixed material of the first backing layer 111 and the second backing layer 112 is a mixture of tungsten powders of various particle sizes. Preferably, the tungsten powder has a small particle size range of 8.47 μm-12.70 μm, a medium particle size range of 25.40 μm-31.80 μm, and a large particle size range of 425 μm-847 μm.

[0037] Based on the above example, the proportion of large-particle tungsten powder in the first backing layer 111 can be greater than that in the second backing layer 112. Preferably, in the first backing layer 111, the mass ratio of small particle size: medium particle size: large particle size is 1:2:3, and in the second backing layer 112, the mass ratio of small particle size: medium particle size: large particle size is 3:2:1.

[0038] In this embodiment, the excitation electrical signal applied to a typical acoustic logging transducer during operation is a broadband signal. The addition of tungsten powder of various particle sizes to the backing layer achieves acoustic attenuation across a wide frequency band. Given a fixed backing layer design size and volume, smaller tungsten powder particle sizes increase specific surface area. Therefore, a higher proportion of large-size tungsten powder in the first backing layer 111 results in a higher density and higher acoustic impedance. A lower proportion of large-size tungsten powder in the second backing layer 112 results in a lower density and lower acoustic impedance.

[0039] In one example, the epoxy glue is a high-temperature resistant packaging glue, such as high-temperature resistant epoxy glue, high-temperature resistant polyimide glue, etc. In this example, high-temperature resistant epoxy glue is preferred.

[0040] In one example, the rubber powder is a high-temperature resistant rubber powder. In this example, the rubber powder is preferably a high-temperature resistant fluororubber powder with a particle size of 8.47 μm to 12.70 μm.

[0041] In one example, the stacked surface of the first backing layer 111 and the second backing layer 112 has a planar structure or a concave-convex structure.

[0042] The stacked surface of the concave-convex structure can increase the reflection and refraction paths of sound waves and increase the attenuation effect of sound waves in the backing layer.

[0043] In one example, the cone angle of the second backing layer 112 is greater than that of the first backing layer 111. Specifically, the cone angle of the first backing layer 111 may be 30° to 120°, and the cone angle of the second backing layer 112 may be 120° to 160°.

[0044] In this embodiment, the two backing layers have slightly different taper angles, which increases the reflection path of sound waves at the interface and prevents vertically incident sound waves from directly transmitting through the first and second backing layers to the housing. The smaller taper angle of the first backing layer 111 increases the area of ​​the stacking surface between the two backing layers, thereby increasing the attenuation of sound waves on this stacking surface.

[0045] In one example, the height of the second backing layer 112 is less than the height of the first backing layer 111. The height of the first backing layer may be an integer multiple of a quarter wavelength, which refers to the wavelength of the ultrasonic wave propagating in the first backing layer 111. The height of the second backing layer 112 may also be an integer multiple of a quarter wavelength, which refers to the wavelength of the ultrasonic wave propagating in the second backing layer 112.

[0046] In one example, returning to Figure 1 The backing structure 110 further includes a positive lead hole 114 and a negative lead hole 115. Preferably, the positive lead hole 114 and the negative lead hole 115 can be located at a 180° angle to the side of the backing structure 110. The two holes are used to pass the positive and negative lead wires drawn from the piezoelectric layer. The positive lead hole 114 and the negative lead hole 115 can be circular or semicircular in shape, and the size of the holes is slightly larger than the wire diameter.

[0047] In one example, continue with reference Figure 1 A connection point accommodating groove 116 can be provided at the bottom of the first groove 113. The connection point accommodating groove 116 is used to accommodate the connection point of the wire on the surface of the piezoelectric layer. Preferably, the diameter of the connection point accommodating groove 116 can be set to 1mm to 3mm, and the depth can be set to 0.5mm to 2mm.

[0048] like Figure 3 As shown, an embodiment of the present application provides a transducer 10 for ultra-deep wells, and the transducer 10 includes the backing structure 110 described in any of the above examples.

[0049] In one example, reference Figure 3The transducer 10 may further include a piezoelectric layer 101, a matching layer 102, and a housing 103. The piezoelectric layer 101 is located at the first groove 113, the matching layer 102 is located at the bottom of the piezoelectric layer 101, and the housing 103 is covered on the outside of the backing structure 110.

[0050] Specifically, continue to refer to Figure 3 The piezoelectric layer 101 is accommodated in the first groove 113 of the first backing layer 111, and the size of the piezoelectric layer 101 can be adapted to the first groove 113. The piezoelectric layer 101 can be used to transmit and receive ultrasonic waves.

[0051] Continue to refer Figure 3 The matching layer 102 may be a cylindrical structure and is disposed at the bottom of the piezoelectric layer 101. The matching layer 102 may be used to strengthen the forward ultrasonic wave generated by the piezoelectric layer 101.

[0052] Continue to refer Figure 3 The housing 103 and the matching layer 102 can be integrally formed and cylindrically covered on the outside of the backing structure 110 and the piezoelectric layer 101. The housing 103 is used to encapsulate and protect the backing structure 110 and the piezoelectric layer 101.

[0053] It is easy to understand that the integral molding of the housing 103 and the matching layer 102 can enhance the packaging and protection effects of the backing structure 110 .

[0054] The integrally formed housing 103 and the matching layer 102 have no secondary sealing interface, which can prevent the mud in the well from penetrating into the transducer due to interface cracking under high temperature and high pressure, otherwise there is a risk of short circuit between the positive and negative electrodes.

[0055] In one example, the piezoelectric layer 101 can be made of a piezoelectric material that is resistant to high temperature and high voltage, such as lead titanate piezoelectric ceramics, lead niobate piezoelectric ceramics, bismuth scandate-lead titanate piezoelectric ceramics, lead zirconate titanate piezoelectric ceramics, or 1-3 type, 1-1 type, 0-3 type piezoelectric composite materials based on the above piezoelectric ceramics. The thickness of the piezoelectric layer 101 can be adjusted according to the target center frequency f c Set (l = c / 2f c ), if the center frequency range is set to 200kHz to 1MHz, the thickness range of the 1-3 type piezoelectric composite material in this example is approximately 1.5mm to 7.0mm.

[0056] In one example, the matching layer 102 can be made of a high-temperature resistant polymer material, such as high-temperature epoxy, high-temperature bismaleimide, high-temperature polyimide, etc. In this example, the matching layer 102 and the shell 103 can be made of high-temperature resistant epoxy glue that has been modified in a certain manner and then packaged and cured at high temperature.

[0057] In addition, the acoustic impedance of the matching layer 102 can be calculated according to the MASON model theory. The acoustic impedance value Z of a single matching layer is m =(Z p Z l 2 ) 1 / 3 Design, where Z p is the acoustic impedance of the piezoelectric layer, Z l is the acoustic impedance of the load medium.

[0058] The load medium can be clean water, silicone oil, mud, etc. In this example, the load medium is silicone oil, and the acoustic impedance of silicone oil is about 0.97×10 6 Pa·s / m. The piezoelectric layer 101 is made of a high-temperature 1-3 type piezoelectric composite material with an acoustic impedance of approximately 2.3×10 7 Pa·s / m. The optimal acoustic impedance of the matching layer 102 is about 2.79×10 6 Pa·s / m, the thickness of the matching layer 102 is preferably a quarter wavelength, which is the wavelength of the ultrasonic wave propagating in the matching layer 102. In this example, if the center frequency range of the transducer 10 is 200kHz to 1MHz, the longitudinal wave speed of the matching layer is 2200m / s, and the formula λ=c / f c The calculated quarter wavelength range is 0.55 mm to 2.75 mm.

[0059] In one example, continue with reference Figure 3 The transducer 10 further includes a positive wire 104 and a negative wire 105. Preferably, the positive wire 104 and the negative wire 105 are high temperature resistant wires with a maximum temperature resistance of ≥ 260°C.

[0060] The present invention also provides a method for manufacturing an ultra-deep well transducer, which can be used to manufacture the transducer 10 described in the above example.

[0061] Before describing the method for manufacturing the ultra-deep well transducer 10 proposed by the present invention, it is necessary to first describe its advantages over the prior art.

[0062] The conventional manufacturing process for acoustic logging transducers follows the following process: fabricating a backing layer; fabricating a matching layer; extracting positive and negative electrodes from the piezoelectric layer; bonding the sample (backing layer + piezoelectric layer + matching layer); positioning the bonded sample within the housing; and encapsulating with adhesive. Transducers made using this process, where the housing and the bonded sample are connected by encapsulating adhesive, struggle to meet the requirements for high-temperature and high-voltage resistance.

[0063] In order to solve the above technical problems and improve the high temperature and high pressure resistance of ultrasonic transducers, the present invention proposes a method for manufacturing an ultra-deep well transducer 10, which adopts a high temperature pressing process and an integrated packaging technology. Figure 4 The specific technical process flow of the manufacturing method is as follows: select piezoelectric material as the piezoelectric layer 101; press the first backing layer 111 at high temperature; press the second backing layer 112 at high temperature; lead out the negative electrode wire 105 of the piezoelectric layer 101; apply high temperature pressure to bond the piezoelectric layer 101 and the first backing layer 111; lead out the positive electrode wire 104 of the piezoelectric layer 101; and use a high-temperature packaging method to package the backing structure 110 and the piezoelectric layer 101 into a shell 103.

[0064] Step S401: Select a piezoelectric material as the piezoelectric layer 101. A high-temperature and high-pressure resistant piezoelectric ceramic, piezoelectric single crystal, or piezoelectric composite material with thickness vibration as the main vibration mode can be selected. The size parameters are determined according to the requirements of acoustic logging and the parameters of the selected material.

[0065] Step S401: High-temperature pressing of the first backing layer 111. The first backing layer 111 is pressed into a predetermined shape using a high-temperature press. After the first backing layer 111 is solidified and formed, the pressed mold is removed.

[0066] Step S402: High-temperature pressing of the second backing layer 112. Based on the formed first backing layer 111, a high-temperature press is used to press the second backing layer 112 into a predetermined shape. After the second backing layer 112 is solidified, the pressing mold is removed and the pressed integrated backing structure 110 is removed.

[0067] It is worth noting that the pressing of the first backing layer 111 and the second backing layer 112 can each include two pressing steps: first, placing the backing layer in a normal temperature press and applying a pressure of 5 to 10 MPa for 0.5 to 1 hour for pre-forming; then, releasing the pressure, placing the backing layer in a high temperature press and applying a pressure of 0.1 to 0.5 MPa, and then maintaining the pressure at 180°C to 210°C for 1 to 2 hours for curing. Since the backing layer material is a tungsten powder-rubber powder-epoxy composite material, the amount of rubber powder and epoxy is extremely small, and each tungsten powder particle is coated with a very thin layer of a rubber mixture of rubber powder and epoxy. In this state, the tungsten powder-rubber powder-epoxy composite material can be added to the pressing mold in layers and pressed at different pressures. The pressure applied during pressing decreases from the bottom of the cone to the tip. The greater the pressure, the greater the density of the pressed backing layer and the correspondingly greater acoustic impedance.

[0068] Step S404: Lead out the negative lead 105 of the piezoelectric layer 101. The negative lead 105 can be connected to the silver layer on the negative surface of the piezoelectric layer 101 by soldering or bonding with a conductive adhesive. Soldering can use high-temperature solder, with a melting point of 295°C to 305°C. The conductive adhesive bonding method can use a high-temperature conductive adhesive. In this example, the curing temperature can be 160°C to 200°C, the applied pressure can be 0.05 to 0.1 MPa, and the curing time can be 1 to 2 hours.

[0069] Step S405: High-temperature pressure is applied to bond the piezoelectric layer 101 and the first backing layer 111. Specifically, the surface of the first groove 113 of the first backing layer 111 and the negative electrode surface of the piezoelectric layer 101 can be connected together using an adhesive. The piezoelectric layer 101 is then placed in a high-temperature press, and a specific pressure and temperature program is set to cure the press. In this example, the curing temperature can be set to 180°C to 210°C, the applied pressure can be 0.05 to 0.5 MPa, and the curing time can be 1 to 2 hours.

[0070] Step S406: Leading out the positive lead 104 of the piezoelectric layer 101. The method for leading out the positive lead 104 of the piezoelectric layer 101 in this step may be the same as that in step S404, and will not be repeated here.

[0071] In step S407, the backing structure 110 and the piezoelectric layer 101 are packaged in the housing 103 using a high-temperature packaging method. Specifically, the bonded body of the piezoelectric layer 101 and the backing structure 110 is positioned in a packaging mold. The high-temperature epoxy adhesive is mixed evenly and vacuum-defoamed. The mold is then poured and placed in a vacuum high-temperature oven for curing. In this example, the curing temperature can be set between 180°C and 210°C, and the curing time can be 1 to 2 hours.

[0072] When bonding the transducer, a high-temperature resistant adhesive is used. The curing process is high temperature and a certain amount of pressure. The advantages of this process are: applying a certain amount of pressure helps control the thickness of the adhesive bond line, and high-temperature curing can improve the high-temperature resistance of the bonding interface.

[0073] The advantage of the integrated packaging technology is that the matching layer 102 and the shell 103 are formed in one step, and the process is simplified. The matching layer 102 and the shell 103 are made of the same homogeneous material. The integrated packaging has no secondary packaging interface, which prevents the risk of cracking due to high temperature and high pressure.

[0074] In one example, after the backing structure 110 and the piezoelectric layer 101 are packaged in a housing, the transducer 10 may be post-processed.

[0075] Specifically, the surface of the packaged transducer 10 may be treated to remove the overflowed glue, and a number may be etched using a laser marking machine.

[0076] In one example, after the transducer 10 is post-processed, the transducer 10 may be subjected to a high-temperature aging process.

[0077] Specifically, the transducer 10 can be placed in a high-temperature oven and kept at the target operating temperature for 1.5-3 hours. Referring to the temperature in an ultra-deep well, the temperature of the high-temperature aging treatment in this example is ≥210°C.

[0078] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A backing structure, characterized in that: include: The first backing layer has a cylindrical conical structure and a first groove is provided at the center of the bottom, wherein the first groove is used to accommodate the piezoelectric layer; The second backing layer is a column-cone structure with a second groove at the center of the bottom, through which the first backing layer is stacked on the bottom of the second backing layer; Among them, the acoustic impedance of the backing structure decreases gradually from the bottom of the first backing layer to the top of the second backing layer; the first backing layer and the second backing layer are both used to absorb the sound waves propagating backward of the piezoelectric layer, and the stacking surface of the first backing layer and the second backing layer is used to promote the absorption of the sound waves propagating backward of the piezoelectric layer.

2. The backing structure according to claim 1, characterized in that The stacked surface of the first backing layer and the second backing layer has a planar structure or a concave-convex structure.

3. The backing structure according to claim 1, characterized in that The taper angle of the second backing layer is greater than the taper angle of the second backing layer.

4. The backing structure according to claim 1, characterized in that The first backing layer and the second backing layer are both formed by mixing three materials: tungsten powder, rubber powder and epoxy glue, and the mass ratio of the rubber powder is less than 5%.

5. The backing structure according to claim 4, characterized in that The first backing layer and the second backing layer have different mixing ratios of constituent materials; wherein, The mass ratio of tungsten powder in the first backing layer is higher than that in the second backing layer; The first backing layer has a smaller rubber powder mass ratio than the second backing layer.

6. The backing structure according to claim 4, characterized in that The tungsten powder in the mixed material of the first backing layer and the second backing layer is a mixture of tungsten powders with multiple particle sizes, wherein the small particle size ranges from 8.47 μm to 12.70 μm, the medium particle size ranges from 25.40 μm to 31.80 μm, and the large particle size ranges from 425 μm to 847 μm.

7. The backing structure according to claim 6, characterized in that The first backing layer has a larger proportion of large-particle tungsten powder than the second backing layer.

8. A transducer for ultra-deep wells, characterized in that: The backing structure comprises the backing structure according to any one of claims 1 to 7.

9. The transducer according to claim 8, characterized in that The transducer also includes: A piezoelectric layer, used for transmitting and receiving ultrasonic waves; the piezoelectric layer is accommodated in the first groove of the first backing layer; a matching layer, used to strengthen the forward ultrasonic wave generated by the piezoelectric layer; The matching layer is located at the bottom of the piezoelectric layer; The shell is used to encapsulate and protect the backing structure and the piezoelectric layer. The shell and the matching layer are integrally formed and are cylindrically coated on the outside of the backing structure and the piezoelectric layer.

10. A method for manufacturing an ultra-deep well transducer, characterized in that: For manufacturing the transducer according to any one of claims 8 to 9, a high-temperature pressing process and an integrated packaging technology are used, the method comprising: Selecting piezoelectric material as the piezoelectric layer; High temperature pressing of the first backing layer; High temperature pressing of the second backing layer; Lead out the negative electrode wire of the piezoelectric layer; Bonding the piezoelectric layer and the first backing layer under high temperature and pressure; Lead out the positive electrode wire of the piezoelectric layer; A high-temperature packaging method is used to package the backing structure and the piezoelectric layer into a housing.

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