Ultrasonic transducer capable of continuously and stably working in high-temperature and high-pressure extreme environment

Abstract

The invention aims to provide an ultrasonic transducer capable of continuously and stably working in a high-temperature and high-pressure extreme environment, and belongs to the technical field of ultrasonic nondestructive testing, the ultrasonic transducer comprises a packaging matching layer, a piezoelectric layer, an electrode layer and a backing layer, the packaging matching layer can have the effects of high temperature resistance, high pressure resistance and heat dissipation so as to match acoustic impedance, and the piezoelectric layer is arranged on the backing layer. Therefore, the acoustic performance of the transducer is improved. The piezoelectric layer can keep excellent piezoelectric performance in a high-temperature environment. The electrode layer and the back lining layer can achieve a good heat dissipation effect, and the service life is prolonged. The method has a wide application prospect in the field of ultrasonic nondestructive testing in an extreme environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultrasonic non-destructive testing, and in particular relates to an ultrasonic transducer that can operate continuously and stably under extreme conditions of high temperature and high pressure. Background Art

[0002] Oil and gas resources have long been essential natural resources for human survival, closely intertwined with human production and daily life. In recent decades, my country's rapid economic development and the gradual improvement of people's living standards have led to a growing demand for oil across all industries. Consequently, many oilfield companies are pursuing the goal of efficiently and cost-effectively extracting oil. Oil extraction is a complex process, requiring exploration before production and drilling, completion, and production during the production process. Well logging is a crucial technology throughout the oil extraction process. In the early stages of development, it is necessary to collect relevant information about openhole wells. In the mid-to-late stages of development, wellbore condition monitoring is essential to inform wellbore maintenance. Therefore, it is often desirable to visually observe the lithology, vug development, and cracks in the openhole wellbore wall, as well as to check casing deformation, corrosion, perforation placement, and cementing quality.

[0003] With the development of industrialization in my country, the demand for fossil fuels such as oil and natural gas has increased dramatically, leading to a surge in the exploration and development of these resources. However, the probes used in domestic logging-while-drilling (LWD) instruments are mostly imported, and the research and development (R&D) of these instruments is still in the R&D stage. While research has been conducted on LWD ultrasonic caliper gauges, mature LWD ultrasonic imaging logging instruments have yet to enter service. Therefore, it is imperative to break the monopoly of foreign oilfield service companies on LWD technology and independently develop LWD imaging logging instruments with Chinese intellectual property rights.

[0004] In oil well logging, ultrasonic transducers must stably acquire formation acoustic parameters (such as porosity, fracture distribution, and wellbore integrity) over long periods of time in extreme environments such as deep wells, high temperatures (>200°C), high pressures (>100MPa), hydrogen sulfide (H2S), and salt spray corrosion. Traditional piezoelectric ceramic transducers (such as PZT) have the following bottlenecks: Limited frequency band and sensitivity: The mechanical resonance characteristics of a single piezoelectric ceramic result in a narrow operating frequency band (typical bandwidth <15%), making it difficult to achieve both high-frequency resolution and low-frequency penetration. Furthermore, the acoustic impedance mismatch (Z≈30 MRayl) results in an acoustic energy transfer efficiency of less than 40%. Poor thermal stability: piezoelectric constant d at high temperature 33 Significant attenuation (>30% drop at 150°C), sharp increase in dielectric loss (tanδ), causing frequency drift (>5%) and signal distortion; Insufficient mechanical reliability: Ceramics fracture brittlely under high pressure and vibration impact, electrode plating (such as silver / nickel) is easily corroded and peeled off by H2S, and the average device life is less than 200 hours.

[0005] To overcome these shortcomings, 1-3 composite piezoelectric materials (piezoelectric ceramic pillars embedded in a polymer matrix) have emerged. Their structural design optimizes acoustic impedance matching (Z≈5-25 MRayl) and broadens the bandwidth to 20%-30%. However, they still face severe challenges in extreme environmental applications: High-temperature failure of the matrix material: Conventional epoxy resin matrix softens at temperatures above 150°C (elastic modulus decreases by >50%), causing the piezoelectric column to tilt or the interface to peel, resulting in a sharp degradation of acoustic performance; Electrode-ceramic interface degradation: At high temperatures, the coefficient of thermal expansion (CTE) of the metal electrode (such as NiCr) and the ceramic is mismatched (ΔCTE ≈ 10 ppm / °C), causing microcracks and a doubling of the contact resistance. Corrosion-resistant packaging defects: Existing packaging mostly uses a single metal shell, which makes it difficult to balance acoustic transmission (requires a low-impedance acoustic window) and resistance to hydrogen sulfide corrosion (requires an inert coating), and the long-term sealing is insufficient. Summary of the Invention

[0006] The purpose of the present invention is to provide an ultrasonic transducer that can continuously and stably operate in the extreme environment of high temperature and high pressure of oil logging, which can solve the problem in the technical background that the existing traditional single-element ultrasonic transducer cannot operate stably in high temperature, high pressure and highly corrosive environments.

[0007] To achieve the above object, the present invention adopts the following technical solutions: An ultrasonic transducer capable of sustained and stable operation in extreme high-temperature and high-pressure environments includes a packaged matching layer, the packaged matching layer comprising a housing, an acoustic window structure, and a matching layer. The acoustic window structure is located at the bottom of the housing, and the matching layer is located inside the acoustic window structure. From bottom to top, the matching layer includes a second matching layer and a first matching layer. A piezoelectric layer is provided on the matching layer, and a top electrode and a bottom electrode are provided at the upper and lower ends of the piezoelectric layer. A backing layer is provided above the piezoelectric layer. A spiral pressure channel is provided on the inner side of the shell, and the remaining space in the shell is filled with modified polyimide resin; the acoustic window structure is directly opposite to the radiation surface of the piezoelectric layer.

[0008] Furthermore, the shell is made of metal material, the acoustic window structure is made of ceramic composite material, and is embedded in the metal shell using brazing technology. The thickness of the acoustic window structure is 1 / 4 wavelength of the transducer operating frequency, and a diamond-like carbon film is provided on the outside of the acoustic window structure.

[0009] Furthermore, the metal material is brass, and the ceramic composite material is a silicon nitride polyimide composite material.

[0010] Furthermore, the matching layer is composed of a single material to form a single-layer structure, and is composed of different materials to form a gradient matching structure.

[0011] Furthermore, the first matching layer is a mixed material of silicon carbide and polyimide, with a thickness of 1.2 mm and an acoustic impedance of 8-18 MRayl; the second matching layer is a mixed material of aluminum nitride and silicone rubber, with a thickness of 0.8 mm and an acoustic impedance of 2.5-8 MRayl.

[0012] Furthermore, the first matching layer and the second matching layer are bonded and connected by spraying strontium titanate on the interface, and the first matching layer and the piezoelectric layer are bonded and connected by spraying strontium titanate on the interface.

[0013] Furthermore, the piezoelectric layer is a 1-3 piezoelectric composite material layer, including a piezoelectric material layer composed of PZT-5H32 material and a polymer matrix composed of a mixture of polyimide and boron nitride nanosheets.

[0014] Furthermore, the surface of the polymer matrix composed of the mixture of polyimide and boron nitride nanosheets is plasma treated to pre-deposit titanium as a transition layer.

[0015] Furthermore, the bottom electrode and the top electrode are sputtered on the surface of the piezoelectric layer using nickel-chromium alloy, the thickness of the bottom electrode and the top electrode are both 1 μm, and the surfaces of the bottom electrode and the top electrode are provided with gold as an electrode protection layer.

[0016] Furthermore, the backing layer is a composite material of tungsten powder, silicon carbide whiskers and liquid crystal polymer, wherein the mass proportion of tungsten powder is 70%, the mass proportion of silicon carbide whiskers is 5%, and the rest is liquid crystal polymer. The thickness of the backing layer is 5-8 mm.

[0017] Furthermore, an opening is provided at the top of the shell, a lead is passed through the opening, and one end of the lead passes through the backing layer and is connected to the top electrode.

[0018] The innovation of the present invention lies in: Matrix material innovation: Using a liquid crystal polymer (LCP) matrix reinforced with nano-ceramic particles, the temperature resistance is increased to 250°C and the interface bonding strength is increased by 2 times; Integrated packaging technology: Develop a metal-ceramic composite shell with an embedded pressure balance channel to ensure that the transducer does not deform under a pressure of 100MPa.

[0019] Multi-level matching layer technology: Using modified materials, a transition layer is added between the matching layer and the adjacent medium to alleviate the CTE mismatch problem.

[0020] The beneficial effects of the present invention are as follows: 1. The ultrasonic transducer of the present invention can stably transmit and receive ultrasonic waves in extreme environments and can work continuously for more than 24 hours.

[0021] 2. The brass housing provides high-temperature, high-pressure, and corrosion resistance in environments exceeding 250°C, 100 MPa, and severe corrosion. The tensile strength exceeds 250 MPa in these environments. A pressure channel embedded in the brass housing balances external pressure through static pressure differentials. The brass housing and the element are secured with a modified polyimide resin (a mixture of polyimide (90 wt%) and boron nitride nanosheets (10 wt%)). This modified polyimide resin resists deformation at high temperatures and provides thermal stress compensation. These two structures ensure minimal deformation of the brass housing in high-temperature, high-pressure environments, reducing stress on the transducer element and extending its operating life. The backing layer absorbs clutter, increases bandwidth, and provides mechanical support to withstand the high-pressure environment downhole. A thermal expansion coefficient matching that of the piezoelectric material ensures the ultrasonic transducer's acoustic performance at high temperatures.

[0022] 3. When emitting ultrasonic waves, the acoustic impedance optimization design of the gradient matching layer and the acoustic window structure significantly reduces the acoustic wave reflection loss at the transducer-mud interface. 3 In a slurry medium with an acoustic impedance of approximately 5 MRayl, acoustic energy transmission efficiency is increased to over 70% (compared to 55% for conventional structures). This design effectively reduces the reactive heat loss of the transducer, thereby lowering the risk of piezoelectric material depolarization and significantly extending the device's service life.

[0023] 4. When receiving ultrasound, the gradient matching layer and acoustic window structure increase the transmittance of ultrasound, allowing more ultrasound energy to be received by the piezoelectric layer, improving the sensitivity of receiving high-frequency ultrasound energy. The backing layer absorbs the back-directed sound waves, increasing the bandwidth of the ultrasonic transducer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of the ultrasonic transducer of the present invention; Figure 2 Modeling of the piezoelectric material of the ultrasonic transducer of the present invention in a high temperature environment; Figure 3 This is an impedance simulation diagram of the ultrasonic transducer of the present invention in a high temperature environment.

[0025] Among them: 1-diamond-like carbon film; 2-acoustic window structure; 3-second matching layer; 4-first matching layer; 5-bottom electrode; 6-piezoelectric material layer; 7-polymer matrix; 8-top electrode; 9-backing layer; 10-pressure channel; 11-modified polyimide resin; 12-housing; 13-lead. DETAILED DESCRIPTION

[0026] The present invention will be further described with reference to the accompanying drawings.

[0027] like Figure 1 As shown, an ultrasonic transducer that can continuously and stably operate in an extreme environment of high temperature and high pressure includes a packaging matching layer. The packaging matching layer includes a shell 12, an acoustic window structure 2 and a matching layer, which is used for heat dissipation, matching acoustic impedance, and providing resistance to high temperature, high pressure and corrosion.

[0028] The shell 12 is made of metal material (brass), and the acoustic window structure 2 is made of ceramic composite material (silicon nitride (40v%) polyimide (60v%) composite material). The acoustic window structure 2 is embedded in the shell using brazing technology to reduce the impact of thermal stress.

[0029] The acoustic window structure 2, located at the bottom of the housing 12, protects the ultrasonic transducer's core components and matches acoustic impedance. A layer of diamond-like carbon (DLC) is coated on its surface to protect it from erosion by mud. Positioned directly opposite the radiating surface of the piezoelectric layer, the acoustic window structure 2 is constructed of modified materials and welded with local reinforcements to ensure operational stability in extreme high-temperature and high-pressure environments.

[0030] The matching layer is located inside the acoustic window structure 2 . The matching layer is composed of a single-layer structure made of a single material and a gradient matching structure made of different materials. From bottom to top, it includes a second matching layer 3 and a first matching layer 4 .

[0031] The matching layer is provided with a piezoelectric layer, which plays a role in adapting shallow-layer high-resolution imaging and deep-layer penetration detection, and is used to generate or receive medium-frequency ultrasonic waves.

[0032] The upper and lower ends of the piezoelectric layer are provided with a top electrode 8 and a bottom electrode 5 for dissipating the heat generated during operation.

[0033] A backing layer 9 is provided above the piezoelectric layer; the backing layer 9 structure is used to dissipate heat, absorb reflected ultrasonic waves, isolate the piezoelectric element from the external environment, and provide temperature, pressure and corrosion resistance.

[0034] A spiral pressure channel 10 is provided inside the housing 12 to disperse external loads using hydrostatic pressure.

[0035] The remaining space within the housing 12 is filled with a modified polyimide resin 11 (a mixture of polyimide (90 wt %) and boron nitride nanosheets (10 wt %)) to disperse pressure, attenuate back-directed acoustic waves, provide a certain degree of thermal stress compensation, and prevent the medium from penetrating into sensitive components.

[0036] The backing layer 9 absorbs reflected noise and provides a temperature-resistant, pressure-resistant and corrosion-resistant environment. It uses modified tungsten material and is formed by hot pressing and laser welding to absorb back sound waves, provide mechanical support and match the thermal expansion coefficient with the piezoelectric material.

[0037] The first matching layer is a mixed material of silicon carbide (35v%) and polyimide (65v%), with a thickness of 1.2mm and an acoustic impedance of 8-18MRayl. The second matching layer is a mixed material of aluminum nitride (20v%) and silicone rubber (80v%), with a thickness of 0.8mm and an acoustic impedance of 2.5-8MRyal. When the first and second matching layers are gradiently superimposed, a transition layer (50 nm) needs to be sprayed on the interface to enhance the bonding strength; Adding a strontium titanate buffer layer between the first matching layer and the piezoelectric layer can effectively alleviate the CTE mismatch problem PZT-CTE≈4 ppm / ℃, first matching layer-CTE≈6 ppm / ℃.

[0038] The piezoelectric layer is composed of 1-3 piezoelectric composite material layers. The piezoelectric material uses PZT-5H32 material, and the polymer matrix material uses a mixture of polyimide (90wt%) and boron nitride (10wt%) nanosheets. The thermal conductivity coefficient is increased to 1.5-2.0W / (m·K), and the compressive strength is increased to more than 100Mpa.

[0039] The surface of the polymer matrix 7 composed of a mixture of polyimide and boron nitride nanosheets is treated in a plasma mixture of oxygen and argon, titanium is pre-deposited as a transition layer to improve the adsorption force of the electrode, and a gradient process is used to relieve thermal stress.

[0040] The bottom electrode 5 and top electrode 8 are sputtered onto the surface of the piezoelectric layer using a nickel-chromium alloy. The thickness of each electrode is 1 μm, and a gold protective layer is applied to the surface of the bottom electrode 5 and the top electrode 8. If the thickness of the bottom electrode 5 and the top electrode 8 is too thin, the resistance increases and the electrode is prone to breakage. If the thickness is too thick, the mechanical load increases, thereby reducing the Q value of the transducer. The gold protective layer is 0.2 μm thick and prevents the electrode from breaking in extreme environments when the CTE mismatch with the piezoelectric material occurs.

[0041] The backing layer 9 is made of a composite material of tungsten powder, silicon carbide whiskers, and liquid crystal polymer (W-LCP), with tungsten powder accounting for 70% by weight and silicon carbide whiskers accounting for 5%. The addition of silicon carbide whiskers increases the overall compressive strength of the material to over 200 MPa. The overall composite material has an attenuation coefficient of approximately 5 dB / mm.

[0042] The thickness of the backing layer 9 needs to be sufficient to completely attenuate the sound wave by at least 20 dB, and the thickness range is 5-8 mm.

[0043] The spiral pressure channel 10 is machined using CNC machining. After the transducer element is fixed, the gap between the element and the brass shell is filled with modified polyimide resin. The brass shell is then machined using CNC machining and the surface is spray-coated.

[0044] The top of the housing 12 is provided with an opening, and a lead 13 is passed through the opening. One end of the lead 13 passes through the backing layer and is connected to the top electrode 8 .

[0045] 1. The calculation of the ultrasonic transducer of the present invention for sustainable and stable operation under high pressure environment is as follows: The maximum stress in each component of the transducer needs to be lower than the yield strength of the material.

[0046] The hoop stress calculation formula of the shell is as follows: θ =PD / 2t, where P is the external pressure (100MPa); D is the inner diameter of the shell (27mm); and t is the shell wall thickness (8mm). Substituting this into the above formula, the hoop stress is calculated as: 100×27÷2÷8≈168.75MPa. The yield strength of brass is approximately 300MPa. The hoop stress of the shell (168.75MPa) is less than the yield strength of brass (300MPa), so it is safe.

[0047] The yield strength of ceramic composite materials is around 200 MPa, and their actual application scenario is an environment above 100 MPa, so the transducer can continue to operate stably under high-pressure environments. The same applies to the back of the transducer.

[0048] 2. The simulation process of the ultrasonic transducer of the present invention to achieve sustainable and stable operation in a high-temperature environment is as follows: Simulation process: First, model the piezoelectric material.

[0049] When the high-temperature steady state is reached, the temperature of the piezoelectric ceramic will be basically consistent with the outside world. The final simulation model can be simplified to the change of a single piezoelectric composite material. To simplify the calculation process, use Figure 2 Model shown.

[0050] The elastic parameters of piezoelectric materials are shown in Table 1.

[0051] Table 1 Elastic parameters of piezoelectric materials Add parameters to the material, add solid mechanics and electrostatic fields, perform frequency domain simulation, and add temperature parameter sweep in the frequency domain simulation with a step of 50°C.

[0052] Depend on Figure 3 It can be seen that under this solution, in a high temperature environment of 300°C, the resonance peak is still obvious, and the frequency drift is 100KHz, which has little impact on applications in extreme high temperature environments.

[0053] 3. The transmission efficiency of the ultrasonic transducer of the present invention is calculated as follows: (1) When a sound wave is incident vertically on the interface between two media, the reflection coefficient R is determined by the difference in acoustic impedance: R = (Z2-Z1) / (Z2+Z1), where Z1 and Z2 are the acoustic impedances (Rayl) of the two media.

[0054] (2) The transmission coefficient T is calculated as follows: T = 2Z2 / (Z2+Z1).

[0055] (3) The sound energy transmission efficiency η is the ratio of the transmitted sound power to the incident sound power: η=[4Z1Z2 / (Z1+Z2) 2 ]×100%.

[0056] At this time, the theoretical maximum transmission efficiency is η max =[4Z1Z2 / (Z1+Z2) 2 ]×100%.

[0057] The complete sound wave transmission path of the ultrasonic transducer of the present invention is: 1-3 piezoelectric composite material layers - first matching layer - second matching layer - acoustic window structure - mud medium: From Z1=18 to Z2=15: η 1，2 =4×18×15 / (18+15) 2 =1080 / 33 2 =1080 / 1089≈0.991; From Z2=15 to Z3=8: η 2，3 =4×15×8 / (15+8) 2 =480 / 23 2 =480 / 529≈0.907; From Z3=8 to Z4=12: η 3，4 =4×8×12 / (8+12) 2 =384 / 20 2 =384 / 400=0.96; From Z4=12 to Z5=5: η 4，5 =4×12×5 / (12+5) 2 =240 / 17 2 =240 / 289≈0.831.

[0058] η 总 =η 1，2 ×η 2，3 ×η 3，4 ×η 4，5 , substituting the numerical value, the maximum transmission efficiency is calculated to be approximately 71.71%.

[0059] If the traditional piezoelectric ultrasonic transducer does not have a matching layer, then η1 is 25 and η2 is 5, and the maximum transmission efficiency is calculated to be about 55.56%.

Claims

1. An ultrasonic transducer capable of continuous and stable operation in extreme environments of high temperature and high pressure, characterized by: The invention comprises a package matching layer, wherein the package matching layer comprises a shell (12), an acoustic window structure (2) and a matching layer, wherein the acoustic window structure (2) is located at the bottom of the shell (12); the matching layer is located on the inner side of the acoustic window structure (2), and comprises a second matching layer (3) and a first matching layer (4) from bottom to top; a piezoelectric layer is provided on the matching layer, and a top electrode (8) and a bottom electrode (5) are provided at the upper and lower ends of the piezoelectric layer, and a backing layer (9) is provided above the piezoelectric layer; A spiral pressure channel (10) is provided on the inner side of the shell (12), and the remaining space in the shell (12) is filled with a modified polyimide resin (11); the acoustic window structure (2) is directly opposite to the radiation surface of the piezoelectric layer.

2. The ultrasonic transducer capable of continuous and stable operation in extreme high-temperature and high-pressure environments according to claim 1, characterized in that: The shell (12) is made of metal material, and the acoustic window structure (2) is made of ceramic composite material and is embedded in the metal shell (12) using brazing technology. The thickness of the acoustic window structure (2) is 1 / 4 wavelength of the transducer operating frequency, and a diamond-like carbon film (1) is provided on the outer side of the acoustic window structure (2).

3. The ultrasonic transducer capable of continuous and stable operation in extreme high-temperature and high-pressure environments according to claim 2, characterized in that: The metal material is brass, and the ceramic composite material is a silicon nitride polyimide composite material.

4. The ultrasonic transducer capable of continuous and stable operation in extreme high-temperature and high-pressure environments according to claim 1, characterized in that: The matching layer is composed of a single material to form a single-layer structure, and is composed of different materials to form a gradient matching structure.

5. The ultrasonic transducer capable of continuous and stable operation in extreme high-temperature and high-pressure environments according to claim 4, characterized in that: The first matching layer (4) is a mixed material of silicon carbide and polyimide, with a thickness of 1.2 mm and an acoustic impedance of 8-18 MRayl; the second matching layer (3) is a mixed material of aluminum nitride and silicone rubber, with a thickness of 0.8 mm and an acoustic impedance of 2.5-8 MRayl; The first matching layer (4) and the second matching layer (3) are bonded and connected by spraying strontium titanate at the interface, and the first matching layer (4) and the piezoelectric layer are bonded and connected by spraying strontium titanate at the interface.

6. The ultrasonic transducer capable of continuous and stable operation in extreme high-temperature and high-pressure environments according to claim 1, characterized in that: The piezoelectric layer is a 1-3 piezoelectric composite material layer, comprising a piezoelectric material layer (6) composed of a PZT-5H32 material and a polymer matrix (7) composed of a mixture of polyimide and boron nitride nanosheets.

7. The ultrasonic transducer capable of continuous and stable operation in extreme high-temperature and high-pressure environments according to claim 6, characterized in that: The surface of the polymer matrix (7) composed of a mixture of polyimide and boron nitride nanosheets is plasma treated to pre-deposit titanium as a transition layer.

8. The ultrasonic transducer capable of continuous and stable operation in extreme high-temperature and high-pressure environments according to claim 1, characterized in that: The bottom electrode (5) and the top electrode (8) are sputtered on the surface of the piezoelectric layer using nickel-chromium alloy, the thickness of the bottom electrode (5) and the top electrode (8) are both 1 μm, and the surfaces of the bottom electrode (5) and the top electrode (8) are provided with gold as an electrode protection layer.

9. The ultrasonic transducer capable of continuous and stable operation in extreme high-temperature and high-pressure environments according to claim 1, characterized in that: The backing layer (9) is a composite material of tungsten powder, silicon carbide whiskers and liquid crystal polymer, wherein the mass proportion of tungsten powder is 70%, the mass proportion of silicon carbide whiskers is 5%, and the rest is liquid crystal polymer. The thickness of the backing layer (9) is 5-8 mm.

10. The ultrasonic transducer capable of continuous and stable operation in extreme high-temperature and high-pressure environments according to claim 1, characterized in that: An opening is provided at the top of the shell (12), a lead wire (13) is passed through the opening, and one end of the lead wire (13) passes through the backing layer and is connected to the top electrode (8).

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