An ultrasonic transmitting transducer and an ultrasonic scanning imaging logging tool

Abstract

This invention discloses an ultrasonic transmitting transducer and an ultrasonic scanning imaging logging tool, applied in the field of oil well logging technology. The transducer includes: a backing layer; a piezoelectric layer located on one side surface of the backing layer; the backing layer and the piezoelectric layer forming a functional platform, the functional platform including at least a portion of the piezoelectric layer whose dimensions taper in the thickness direction from the backing layer to the piezoelectric layer; a concave surface with a preset focal length formed on the side surface of the piezoelectric layer away from the backing layer; a matching layer located on the side surface of the piezoelectric layer opposite to the backing layer; the matching layer covering the concave surface, the side surface of the matching layer away from the piezoelectric layer being planar. By setting the functional platform on a frustum-shaped functional platform with a tapered dimension in the thickness direction, and setting the piezoelectric layer to form a concave surface with a preset focal length, efficient acoustic energy focusing can be achieved, thereby achieving efficient natural acoustic energy focusing and improving the transmission response.

Description

Technical Field

[0001] This invention relates to the field of oil well logging technology, and in particular to an ultrasonic transmitting transducer and an ultrasonic scanning imaging logging instrument. Background Technology

[0002] Ultrasonic scanning imaging logging tools are widely used in oil exploration, primarily for cementing quality evaluation, casing damage scanning, wellbore calculation, and geological structure description. The transmitting transducer is one of the key components of this equipment, and its performance directly affects the imaging quality and depth of the logging. Traditional transmitting transducers have limited emission response, resulting in unsatisfactory imaging effects. Therefore, how to provide an ultrasonic transmitting transducer that can achieve efficient natural focusing of acoustic energy and improve emission response is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0003] The purpose of this invention is to provide an ultrasonic transmitting transducer that can achieve efficient acoustic energy natural focusing to improve the transmission response; another purpose of this invention is to provide an ultrasonic scanning imaging logging tool that can achieve efficient acoustic energy natural focusing to improve the transmission response.

[0004] To solve the above-mentioned technical problems, the present invention provides an ultrasonic transmitting transducer, comprising:

[0005] Backing layer;

[0006] A piezoelectric layer is located on one side surface of the backing layer; the backing layer and the piezoelectric layer form a functional platform, the functional platform including at least a portion of the piezoelectric layer that tapers in size in the thickness direction from the backing layer to the piezoelectric layer, and the piezoelectric layer has a concave surface with a preset focal length on the side surface away from the backing layer.

[0007] A matching layer is located on the surface of the piezoelectric layer facing away from the backing layer; the matching layer covers the concave surface, and the surface of the matching layer away from the piezoelectric layer is planar.

[0008] Optionally, the height difference of the concave surface can range from 1 mm to 3 mm.

[0009] Optionally, the piezoelectric layer includes multiple piezoelectric layers stacked along the thickness direction, and an electrode layer is disposed between adjacent piezoelectric layers;

[0010] The size of the piezoelectric layer gradually decreases in the direction from the side closest to the backing layer to the side furthest from the backing layer.

[0011] Optionally, the piezoelectric layer includes a substrate, a piezoelectric functional layer, and an electrode layer;

[0012] The substrate tapers in size from the side closest to the backing layer to the side furthest from the backing layer. The surface of the substrate furthest from the backing layer has a groove. The piezoelectric functional layer fills the groove. The electrode layer is disposed on the surface of the piezoelectric functional layer facing away from the backing layer.

[0013] Optionally, the piezoelectric layer includes a piezoelectric layer body and an electrode layer; the piezoelectric layer body is an integrally formed frustoconical piezoelectric layer, and the electrode layer is disposed on the surface of the piezoelectric layer body.

[0014] Optionally, the piezoelectric layer includes a piezoelectric layer body and an electrode layer; the backing layer has a gradually decreasing size in the direction from the side away from the piezoelectric layer to the side closer to the piezoelectric layer, the surface of the backing layer facing the piezoelectric layer has a concave surface, the piezoelectric layer body is adhered to the concave surface, and the electrode layer is disposed on the surface of the piezoelectric layer body.

[0015] Optionally, the matching layer includes a first matching sub-layer located on the surface of the piezoelectric layer away from the backing layer, and a second matching sub-layer located on the surface of the first matching sub-layer away from the backing layer. The first matching sub-layer covers the concave surface, and the surface of the second matching sub-layer away from the piezoelectric layer is planar. The acoustic impedance of the first matching sub-layer is closer to that of the piezoelectric layer than that of the second matching sub-layer.

[0016] Optionally, the acoustic impedance of the backing layer gradually decreases in the direction from the side closer to the piezoelectric layer to the side farther away from the piezoelectric layer.

[0017] Optional, also includes:

[0018] A protective layer located on the surface of the matching layer facing away from the piezoelectric layer.

[0019] The present invention also provides an ultrasonic scanning imaging logging tool, including an ultrasonic transmitting transducer as described in any of the preceding claims.

[0020] The present invention provides an ultrasonic transducer comprising: a backing layer; a piezoelectric layer located on one side surface of the backing layer, wherein the backing layer and the piezoelectric layer form a functional platform, the functional platform including at least a portion of the piezoelectric layer having a gradually decreasing dimension in the thickness direction from the backing layer to the piezoelectric layer, and a concave surface with a preset focal length formed on the side surface of the piezoelectric layer away from the backing layer; a matching layer located on the side surface of the piezoelectric layer opposite to the backing layer; the matching layer covering the concave surface, and the side surface of the matching layer away from the piezoelectric layer being planar.

[0021] By setting the functional platform on a frustum-shaped functional platform with a gradually decreasing thickness, and setting a piezoelectric layer to form a concave surface with a preset focal length, efficient acoustic energy focusing can be achieved, thereby realizing efficient acoustic energy natural focusing and improving the emission response.

[0022] The present invention also provides an ultrasonic scanning imaging logging tool, which has the same beneficial effects as described above, and will not be described in detail here. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of an ultrasonic transmitting transducer provided in an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of a specific ultrasonic transducer provided in an embodiment of the present invention.

[0026] In the diagram: 1. Backing layer, 2. Piezoelectric layer, 3. Matching layer. Detailed Implementation

[0027] The core of this invention is to provide an ultrasonic transmitting transducer. In the prior art, ultrasonic transmitting transducers are generally sheet-like, which limits the transmitting transducer's emission response and results in unsatisfactory imaging effects.

[0028] The present invention provides an ultrasonic transducer comprising: a backing layer; a piezoelectric layer located on one side surface of the backing layer, wherein the backing layer and the piezoelectric layer form a functional platform, the functional platform including at least a portion of the piezoelectric layer having a gradually decreasing dimension in the thickness direction from the backing layer to the piezoelectric layer, and a concave surface with a preset focal length formed on the side surface of the piezoelectric layer away from the backing layer; a matching layer located on the side surface of the piezoelectric layer away from the backing layer; the matching layer covering the concave surface, and the side surface of the matching layer away from the piezoelectric layer being planar.

[0029] By setting the functional platform on a frustum-shaped functional platform with a gradually decreasing thickness, and setting a piezoelectric layer to form a concave surface with a preset focal length, efficient acoustic energy focusing can be achieved, thereby realizing efficient acoustic energy natural focusing and improving the emission response.

[0030] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of an ultrasonic transducer provided in an embodiment of the present invention.

[0032] See Figure 1 In this embodiment of the invention, the ultrasonic transducer includes: a backing layer 1; a piezoelectric layer 2 located on one side surface of the backing layer 1; the backing layer 1 and the piezoelectric layer 2 forming a functional platform, the functional platform including at least a portion of the piezoelectric layer 2 that tapers in size in the thickness direction along the direction from the backing layer 1 to the piezoelectric layer 2, the surface of the piezoelectric layer 2 away from the backing layer 1 having a concave surface with a preset focal length; a matching layer 3 located on the surface of the piezoelectric layer 2 away from the backing layer 1; the matching layer 3 covering the concave surface, the surface of the matching layer 3 away from the piezoelectric layer 2 being planar.

[0033] The piezoelectric layer 2 is mainly used to receive acoustic signals and convert them into electrical signals. The backing layer 1 mainly serves to support the piezoelectric layer 2. In ultrasonic transducers, the backing layer 1 is also required to absorb acoustic signals that have passed through the piezoelectric layer 2 and propagated to it, preventing the acoustic signals from being reflected back to the piezoelectric layer 2 and interfering with the measurement of the acoustic signals. The specific structure of the backing layer 1 will be described in detail later and will not be repeated here.

[0034] The aforementioned piezoelectric layer 2 must consist of at least one piezoelectric material layer and at least one electrode layer located on the surface of the piezoelectric material layer. The piezoelectric material layer primarily responds to acoustic signals, converting the received acoustic signals into electrical signals. The electrode layer primarily collects these electrical signals and transmits them out of the piezoelectric layer 2. Typically, the piezoelectric material layer has a specific polarization direction, and the electrode layer is usually located on the surface of the piezoelectric material layer along the polarization direction to collect current. The specific material of the piezoelectric layer 2 can be found in existing technologies and will not be elaborated upon here.

[0035] In this embodiment, the stacked structure of the piezoelectric layer 2 and the backing layer 1 is the most basic structure that enables the ultrasonic transducer to achieve its function. In this embodiment, this stacked structure is referred to as a functional platform. The portion of the functional platform that includes at least the piezoelectric layer 2 tapers in size along the thickness direction from the backing layer 1 to the piezoelectric layer 2. In this embodiment, the backing layer 1, the piezoelectric layer 2, and subsequent matching layer 3 are all stacked in the thickness direction. Therefore, the thickness direction of the functional platform is the stacking direction. At this time, in this embodiment, at least a portion of the functional platform will form a frustum-shaped platform, and the shape of the frustum is a structure that tapers in size along the thickness direction.

[0036] In this embodiment, the portion forming the frustum-shaped platform needs to include at least the piezoelectric layer 2. That is, the piezoelectric layer 2 itself forms a frustum-shaped structure, or the piezoelectric layer 2 and part of the backing layer 1 form a frustum-shaped structure, or the piezoelectric layer 2 combined with the backing layer 1 as a whole forms a frustum-shaped structure. Since the piezoelectric layer 2 is located on one side of the backing layer 1 in the thickness direction, the functional platform of the frustum-shaped structure is formed at least at one end of the entire functional platform, and the piezoelectric layer 2 is disposed at this end.

[0037] In this embodiment, the piezoelectric layer 2 may have one or more layers of piezoelectric material. However, the surface of the piezoelectric layer 2 away from the backing layer 1 needs to have a concave surface with a preset focal length. This concave surface is formed on the top of the frustum-shaped platform, thus forming an inwardly concave arc surface on the top of the frustum-shaped platform. The concave surface, in conjunction with the functional platform with the frustum-shaped structure, can form a structure similar to a dish-shaped antenna, thereby achieving natural focusing of sound energy and improving the transmission response of the ultrasonic transducer. Furthermore, the frustum-shaped platform can optimize the sound field distribution and improve mechanical strength, and it can precisely control the sound wave propagation path, thus facilitating the generation of high-quality electrical signals by the piezoelectric layer 2.

[0038] The selection of piezoelectric material in the piezoelectric layer 2 above needs to be based on the ambient temperature during use. For example, when the ambient temperature is greater than 200°C, modified piezoelectric ceramic PZT (lead zirconate titanate film) or bismuth titanate-based material with a high Curie temperature can be used. The specific composition of the piezoelectric material is not specifically limited in this embodiment, but depends on the specific situation.

[0039] Specifically, in this embodiment, the ultrasonic transducer is typically required to detect sound wave signals at a relatively long distance. Therefore, the radius of the concave surface is usually required to be large, which results in a smaller height difference between the concave surfaces. This height difference is the difference between the highest and lowest positions of the concave surface along its thickness direction. In this embodiment, the value range of the height difference of the concave surface is typically only 1mm to 3mm.

[0040] The aforementioned matching layer 3 is disposed on the surface of the piezoelectric layer 2 facing away from the backing layer 1, covering the concave surface. The function of this matching layer 3 is to improve acoustic energy transfer efficiency, primarily serving as a matching layer between the piezoelectric layer 2 and the external environment. Since the acoustic impedance of the piezoelectric layer 2 and the medium in the external environment are typically different, to reduce acoustic energy reflection between the piezoelectric layer 2 and the external environment medium and improve energy transfer efficiency, this embodiment can further provide one or more acoustic impedance matching layers 3 on the surface of the piezoelectric layer 2. The acoustic impedance of the material of this acoustic impedance matching layer 3 is typically different from the acoustic impedance of the piezoelectric layer 2 and the acoustic impedance of the external environment medium. Specifically, to make sound wave energy transfer more efficient, in this embodiment, the thickness h of the matching layer 3 is... 匹配层 It can be:

[0041] h 匹配层 =λ / 4;

[0042] Where λ is the wavelength corresponding to the center frequency of the ultrasonic transducer.

[0043] The acoustic impedance Z of the aforementioned matching layer 3 match Should meet:

[0044]

[0045] Z match To match the acoustic impedance of layer 3, Z pzt Z represents the acoustic impedance of the piezoelectric material in piezoelectric layer 2. medium The acoustic impedance of the external environmental medium outside the matching layer 3.

[0046] In this embodiment, the matching layer 3 covers the concave surface, and the surface of the matching layer 3 away from the piezoelectric layer 2 is planar. To facilitate the placement of the matching layer 3, the surface of the matching layer 3 away from the piezoelectric layer 2, i.e., the outward-facing surface, is typically planar. It should be noted that because the height difference of the piezoelectric layer 2 in this embodiment is very small, typically within 3mm, the uneven thickness of the matching layer 3 caused by the curvature of the piezoelectric layer 2 has a minimal impact on the performance of the matching layer 3. That is, the uniform thickness of the matching layer 3 at different locations caused by the curvature of the piezoelectric layer 2 does not affect the performance of the matching layer 3.

[0047] The ultrasonic transducer provided in this embodiment achieves efficient acoustic energy focusing by setting the functional platform on a frustum-shaped functional platform with a gradually decreasing size in the thickness direction, and setting a piezoelectric layer 2 to form a concave surface with a preset focal length. This enables efficient acoustic energy focusing and improves the emission response.

[0048] The specific details of the ultrasonic transducer provided by this invention will be described in detail in the following embodiments.

[0049] Please refer to Figure 2 , Figure 2 This is a schematic diagram of a specific ultrasonic transducer provided in an embodiment of the present invention.

[0050] Unlike the embodiments described above, the embodiments of the present invention further define the structure of the ultrasonic transducer based on the aforementioned embodiments. The remaining details have been described in detail in the embodiments above and will not be repeated here.

[0051] See Figure 2In this embodiment of the invention, the matching layer 3 includes a first matching sub-layer located on the side of the piezoelectric layer 2 away from the backing layer 1, and a second matching sub-layer located on the side of the first matching sub-layer away from the backing layer 1. The first matching sub-layer covers the concave surface, and the side of the second matching sub-layer away from the piezoelectric layer 2 is planar. The acoustic impedance of the first matching sub-layer is closer to the acoustic impedance of the piezoelectric layer 2 than that of the second matching sub-layer.

[0052] The aforementioned matching layer 3 can be composed of multiple matching sublayers stacked together. Specifically, in this embodiment, a first matching sublayer and a second matching sublayer can be used to form the matching layer 3, where the first matching sublayer is located on the piezoelectric surface and the second matching sublayer is located on the surface of the first matching sublayer. In this embodiment, the materials of the first and second matching sublayers are usually different to better extend the bandwidth, improve the emission sensitivity, and improve the acoustic energy transfer efficiency. Specifically, compared to a single-layer matching layer 3, the thickness of a single-layer matching layer 3 usually needs to be one-quarter of a wavelength. However, for a matching layer 3 composed of multiple matching sublayers, such as two matching sublayers, the thickness of each matching sublayer is not required to be one-quarter of a wavelength. In this case, the thickness of each matching sublayer needs to be calculated through simulation to obtain the optimal thickness ratio, for example, the thickness of the first matching sublayer is 0.3 times the wavelength, and the thickness of the second matching sublayer is 0.2 times the wavelength, etc. It should be noted that the above wavelength refers to the wavelength corresponding to the center frequency of the ultrasonic transducer.

[0053] For the matching layer 3 formed by multiple matching sublayers, its materials are usually different. Taking a double-layer matching layer 3 structure composed of a first matching sublayer and a second matching sublayer as an example, the acoustic impedance of the first matching sublayer is closer to that of the piezoelectric layer 2 than that of the second matching sublayer, while the acoustic impedance of the second matching sublayer is closer to that of the external environmental medium than that of the first matching sublayer. This allows for a better gradual transition in acoustic impedance, resulting in a wider operating frequency band and improved transducer emission efficiency. The first matching sublayer is often made of epoxy resin mixed with alumina, zirconium oxide, and tungsten powder, while the second matching sublayer is often made of pure epoxy resin or low-impedance organic materials such as polyimide.

[0054] In this embodiment, the acoustic impedance of the backing layer 1 gradually decreases from the side closer to the piezoelectric layer 2 towards the side farther away from the piezoelectric layer 2. In this embodiment alone, the backing layer 1 can be further configured as a gradient backing layer 1, specifically, its acoustic impedance gradually decreases from the side closer to the piezoelectric layer 2 towards the side farther away from the piezoelectric layer 2. This configuration can improve the absorption efficiency of the backing layer 1 for sound energy, reduce back reflection, and improve the bandwidth characteristics of the transducer. The gradual change in the acoustic impedance of the backing layer 1 can be linear or nonlinear, but in the lateral direction, i.e., the horizontal direction, the acoustic impedance of each layer of the backing layer 1 should generally be kept consistent.

[0055] Specifically, to achieve the aforementioned gradient backing layer 1, this embodiment can specifically set the backing layer 1 as a multi-layer composite structure, thereby achieving a gradual change in acoustic impedance along the direction from the side closer to the piezoelectric layer 2 to the side farther away from the piezoelectric layer 2. Each layer of the aforementioned multi-layer composite structure can use different materials or different proportions of materials to achieve the structure where the acoustic impedance of the backing layer 1 gradually changes along the direction from the side closer to the piezoelectric layer 2 to the side farther away from the piezoelectric layer 2. For example, in this embodiment, a four-layer composite structure is used to form the backing layer 1, wherein the first layer is a tungsten powder / epoxy resin mixture with 80% tungsten powder, the second layer is a tungsten powder / epoxy resin mixture with 60% tungsten powder, the third layer is a tungsten powder / epoxy resin mixture with 40% tungsten powder, and the fourth layer is pure epoxy resin or a mixture of it with a low content of tungsten powder. The first layer of the aforementioned four-layer composite structure is usually the material layer closest to the piezoelectric layer 2. Of course, in this embodiment, the specific structure of the backing layer 1 is not specifically limited, but depends on the specific circumstances.

[0056] Specifically, the backing layer 1 of the aforementioned multi-layer composite structure can be formed using a centrifugal molding process, where the natural gradient is achieved by controlling the sedimentation of fillers such as tungsten powder in a base material such as epoxy resin. Alternatively, the various material layers can be prepared first, and then stacked to form the multi-layer composite structure. The specific preparation process can be set according to the actual situation and is not specifically limited here. Using a centrifugal molding process to prepare the backing layer 1 by controlling the sedimentation of tungsten powder in epoxy resin to achieve a natural gradient has advantages beyond reducing back reflection, improving forward emission efficiency, broadening the operating bandwidth, improving resolution, and improving pulse response characteristics. It also avoids interface reflection caused by abrupt changes in acoustic impedance, improves material bonding strength, reduces interface stress under high-temperature conditions, improves the signal-to-noise ratio, improves logging data quality, and extends the transducer's service life.

[0057] In this embodiment, the material of the backing layer 1 can be a high-temperature polymer composite material modified with polyimide (PI) or a polyether ether ketone (PEEK) based composite material, or a high-temperature elastomer composite material with fluorosilicone rubber or perfluororubber based composite material, or a porous metal composite material with porous tungsten or molybdenum and a high-temperature resin, or a nanocomposite aerogel with nano silica based aerogel composite material, etc.

[0058] Furthermore, in this embodiment, the ultrasonic transducer also includes a protective layer located on the surface of the matching layer 3 facing away from the piezoelectric layer 2. This protective layer primarily serves to isolate and protect the remaining structures of the ultrasonic transducer, preventing corrosion and oxidation of each layer. The specific material of the protective layer can be determined according to actual conditions and is not specifically limited here. In this embodiment, a heat-shielding layer, such as a gold-plated surface, can be further added to the outer layer of the matching layer 3 to improve the performance of the ultrasonic transducer.

[0059] This embodiment specifically provides four different functional platform structures, all of which can achieve efficient acoustic energy natural focusing and improve transmission response.

[0060] In the first case, the piezoelectric layer 2 comprises multiple piezoelectric layers stacked along the thickness direction, with an electrode layer disposed between adjacent piezoelectric layers; the size of the piezoelectric layer gradually decreases along the direction from the side near the backing layer 1 to the side away from the backing layer 1.

[0061] In this structure, only the piezoelectric layer 2 is configured as a frustum-shaped cone, wherein each piezoelectric layer is the aforementioned piezoelectric material layer, and an electrode layer is disposed between at least adjacent piezoelectric layers to extract electrical signals. The aforementioned concave surface is specifically prepared by fabricating each piezoelectric layer with a concave surface, and the electrode layer usually has a certain degree of ductility so that after final stacking and bonding, a frustum-shaped piezoelectric layer 2 with a concave surface is formed.

[0062] Specifically, this structure first requires selecting multiple thin piezoelectric layers, typically made of piezoelectric ceramic, each with a thickness of 0.5 mm to 1 mm. Then, thin electrode layers, such as silver or gold films, are added between each piezoelectric layer. Next, precision cutting techniques are used to cut each layer into slightly different sizes to form a frustum-shaped structure. These material layers are then stacked and bonded in descending order of size to form a conical platform. Finally, a matching layer 3 and a protective layer are added to the outermost layer.

[0063] The second type includes a piezoelectric layer 2 comprising a substrate, a piezoelectric functional layer, and an electrode layer; the substrate gradually decreases in size from the side near the backing layer 1 to the side away from the backing layer 1, the surface of the substrate away from the backing layer 1 has a groove, the piezoelectric functional layer fills the groove, and the electrode layer is disposed on the surface of the piezoelectric functional layer away from the backing layer 1.

[0064] In this structure, a frustum-shaped substrate needs to be prepared first. The substrate gradually decreases in size from the side closest to the backing layer 1 to the side furthest from the backing layer 1. The surface of the substrate furthest from the backing layer 1 has grooves. The piezoelectric functional layer, which is a functional layer formed of piezoelectric material, is filled in the grooves. Finally, an electrode layer is formed on the surface of the piezoelectric layer 2 to form the frustum-shaped piezoelectric layer 2.

[0065] The substrate of the aforementioned structure can be made of lightweight metal, such as titanium alloy or special ceramic material. Grooves are formed on the surface of the substrate, which can form a mesh structure, etc., and the mesh structure of the grooves can further optimize the sound field. Then, piezoelectric ceramic material is filled into these grooves to form a piezoelectric functional layer. Finally, an electrode layer is coated on the surface of the piezoelectric functional layer to form piezoelectric layer 2. Specifically, the grooves can be tapered in size from the side closer to the backing layer 1 to the side farther away from the backing layer 1, so that the piezoelectric functional layer can also be tapered in size from the side closer to the backing layer 1 to the side farther away from the backing layer 1, in order to control the sound propagation path.

[0066] The third type involves a piezoelectric layer 2 comprising a piezoelectric layer body and an electrode layer. The piezoelectric layer body is an integrally formed frustum-shaped piezoelectric layer 2, and the electrode layer is disposed on the surface of the piezoelectric layer body. In this structure, a special mold can be used to directly form the required frustum-shaped concave structure during the piezoelectric material powder molding stage, and the formed green blank is sintered to form the piezoelectric layer body. Then, electrodes are coated on the surface of the piezoelectric layer body to form an electrode layer, polarization treatment is performed, and a backing material, a matching layer 3, and a protective layer are added to complete the fabrication of the ultrasonic transducer.

[0067] Fourthly, the piezoelectric layer 2 includes a piezoelectric layer body and an electrode layer; the backing layer 1 gradually decreases in size from the side away from the piezoelectric layer 2 to the side closer to the piezoelectric layer 2, the surface of the backing layer 1 facing the piezoelectric layer 2 has a concave surface, the piezoelectric layer body is attached to the concave surface, and the electrode layer is disposed on the surface of the piezoelectric layer body.

[0068] In this structure, the backing layer 1 is specifically prepared as the base material in the second structure described above. Specifically, a frustum-shaped concave backing layer 1 is first fabricated, using a metal such as a tungsten alloy or a special polymer. Then, a relatively thin planar piezoelectric ceramic layer is adhered to the concave surface of the backing layer 1 to form the piezoelectric layer body. Afterwards, electrodes can be coated onto the surface of the piezoelectric layer body to form an electrode layer, and a matching layer 3 and a protective layer are added to complete the fabrication of the ultrasonic transducer.

[0069] In this embodiment, the formula for calculating the cone angle θ of the frustum-shaped functional platform is as follows:

[0070] tanθ = D / (2f);

[0071] The cone height H is:

[0072] H = D / 2tan(θ);

[0073] Where D is the diameter of the ultrasonic transducer and f is its focal length.

[0074] The radius of curvature R of the concave surface described above is:

[0075] R=(D 2 +4f 2 ) / (8f);

[0076] The corresponding focal length f can be estimated using the following formula:

[0077] F=R 2 / (2H).

[0078] To optimize focusing, the ratio of the cone height H to the radius of curvature R can be adjusted. Generally, a ratio of H / R between 0.1 and 0.3 yields good results.

[0079] In this embodiment, the bandwidth BW of piezoelectric layer 2 can be estimated using the following formula:

[0080] BW≈2kt 2 / π

[0081] Where kt is the thickness mode motor coupling coefficient, and λ is the wavelength.

[0082] For the concave surface described above, if a parabolic concave surface is used, its equation can be expressed as:

[0083] (r)=h(1-(r / R) 2 );

[0084] Where h is the maximum depth, R is the radius of the parabola, and r is the distance from the midpoint of the concave surface to the center.

[0085] The operating frequency f of ultrasonic transducers used in general well logging is between 100 kHz and 1 MHz, therefore the thickness h of the piezoelectric ceramic sheet in piezoelectric layer 2 is... 压电陶瓷 Relationship with frequency:

[0086] h 压电陶瓷 =c / 2f;

[0087] Where c is the velocity of sound in the material, and generally, a thicker design is required for lower operating frequencies.

[0088] For backing layer 1, the sound attenuation is mainly due to two factors: one is the scattering attenuation caused by the filler, which is commonly prepared by mixing metal powders (such as tungsten, lead, and zinc), hollow microspheres, and epoxy resin; the other factor is the viscosity of the backing material, which can be improved by increasing the flexibility of the base material, as shown in the following formula:

[0089] I absorbed =α·I incident

[0090] Among them, I absorbed The sound energy absorbed by the backing material, I incident Where α is the incident energy and α is the absorption coefficient, a backing material with a high absorption coefficient can effectively absorb excess sound energy and reduce reflection interference.

[0091] The sound energy absorption coefficient α mentioned above is:

[0092] α=1-|R 反射 |²

[0093] Where R 反射 It is the sound reflection coefficient.

[0094] To maximize the acoustic energy absorption of the backing layer 1, a material with α close to 1 can be selected. This means that the acoustic impedance Z2 of the backing material should be close to the acoustic impedance Z1 of the piezoelectric material, but slightly lower, and its acoustic reflection coefficient R... 反射 for:.

[0095] R 反射 =(Z2-Z1) / (Z2+Z1);

[0096] Where Z1 is the acoustic impedance of the piezoelectric material and Z2 is the acoustic impedance of the backing material.

[0097] The acoustic impedance Z is as follows:

[0098] Z = ρc;

[0099] Where ρ is the material density and c is the speed of sound.

[0100] To optimize acoustic impedance matching, ideally Z2≈0.9Z1. This can be achieved by adjusting the density and elastic modulus of the composite material.

[0101] The sound attenuation coefficient β of the backing material is:

[0102] I=I0e (-βx)

[0103] Where I is the sound intensity after the sound wave passes through a material of thickness x, and I0 is the incident sound intensity.

[0104] Materials with larger β values ​​are chosen to maximize sound attenuation. Generally, porous materials or materials with high internal friction have larger β values.

[0105] The speed of sound c mentioned above is:

[0106] c = √(E / ρ);

[0107] Where E is Young's modulus and ρ is the material density.

[0108] The thermal expansion matching of the backing material is:

[0109] Δl / l = α·ΔT;

[0110] Where α is the linear coefficient of thermal expansion, ΔT is the temperature change, and Δl / l is the rate of change of length. Choosing a backing material with an α value close to that of the piezoelectric material for thermal expansion matching can minimize thermal stress.

[0111] The acoustic energy loss factor tanδ of the backing material is:

[0112] tanδ = E" / E';

[0113] Where E" is the loss modulus and E' is the storage modulus. Choosing a high tanδ value for high acoustic energy loss materials usually means better acoustic energy absorption performance.

[0114] Furthermore, in this embodiment, periodic microtextures, such as periodic grooves or mesh structures, can be added to the surface of the functional platform to further optimize the sound field. The texture depth is typically in the range of a fraction to a tenth of the wavelength. The texture shape and size need to be determined through simulation and experimental optimization. The texture period d should satisfy:

[0115] d<λ / 2;

[0116] Where λ is the operating wavelength.

[0117] The following describes an ultrasonic scanning imaging logging tool provided by an embodiment of the present invention. The ultrasonic scanning imaging logging tool described below can be referred to in correspondence with the ultrasonic transmitting transducer described above.

[0118] In this embodiment, the ultrasonic scanning imaging logging tool includes an ultrasonic transmitting transducer provided in any of the above embodiments of the invention. This ultrasonic scanning imaging logging tool typically has multiple ultrasonic transmitting transducers. The specific structure of the ultrasonic transmitting transducer has been described in detail in the above embodiments of the invention and will not be repeated here. Other structures of the multipole acoustic wave receiving device, such as the housing, can be referred to in the prior art and will not be repeated here.

[0119] Since the ultrasonic scanning imaging logging tool provided in this embodiment specifically uses the ultrasonic transmitting transducer provided in the above embodiment, the ultrasonic scanning imaging logging tool can achieve efficient acoustic energy natural focusing to improve the transmission response, thereby having superior performance.

[0120] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0121] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0122] The ultrasonic transmitting transducer and ultrasonic scanning imaging logging tool provided by this invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make several improvements and modifications to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. An ultrasonic transmitting transducer, characterized in that, include: Backing layer; A piezoelectric layer located on one side surface of the backing layer; The backing layer and the piezoelectric layer form a functional platform. The functional platform includes at least a portion of the piezoelectric layer that tapers in size in the thickness direction from the backing layer to the piezoelectric layer. The surface of the piezoelectric layer away from the backing layer has a concave surface with a preset focal length. A matching layer is located on the surface of the piezoelectric layer facing away from the backing layer; the matching layer covers the concave surface, and the surface of the matching layer away from the piezoelectric layer is planar.

2. The ultrasonic transducer according to claim 1, characterized in that, The height difference of the concave surface ranges from 1 mm to 3 mm.

3. The ultrasonic transducer according to claim 1, characterized in that, The piezoelectric layer includes multiple piezoelectric layers stacked along the thickness direction, and an electrode layer is disposed between adjacent piezoelectric layers; The size of the piezoelectric layer gradually decreases in the direction from the side closest to the backing layer to the side furthest from the backing layer.

4. The ultrasonic transducer according to claim 1, characterized in that, The piezoelectric layer includes a substrate, a piezoelectric functional layer, and an electrode layer; The substrate tapers in size from the side closest to the backing layer to the side furthest from the backing layer. The surface of the substrate furthest from the backing layer has a groove. The piezoelectric functional layer fills the groove. The electrode layer is disposed on the surface of the piezoelectric functional layer facing away from the backing layer.

5. The ultrasonic transducer according to claim 1, characterized in that, The piezoelectric layer includes a piezoelectric layer body and an electrode layer; the piezoelectric layer body is an integrally formed frustoconical piezoelectric layer, and the electrode layer is disposed on the surface of the piezoelectric layer body.

6. The ultrasonic transducer according to claim 1, characterized in that, The piezoelectric layer includes a piezoelectric layer body and an electrode layer; the backing layer gradually decreases in size along the direction from the side away from the piezoelectric layer to the side closer to the piezoelectric layer, the surface of the backing layer facing the piezoelectric layer is formed with a concave surface, the piezoelectric layer body is adhered to the concave surface, and the electrode layer is disposed on the surface of the piezoelectric layer body.

7. The ultrasonic transducer according to claim 1, characterized in that, The matching layer includes a first matching sub-layer located on the surface of the piezoelectric layer away from the backing layer, and a second matching sub-layer located on the surface of the first matching sub-layer away from the backing layer. The first matching sub-layer covers the concave surface, and the surface of the second matching sub-layer away from the piezoelectric layer is planar. The acoustic impedance of the first matching sub-layer is closer to that of the piezoelectric layer than that of the second matching sub-layer.

8. The ultrasonic transducer according to claim 1, characterized in that, The acoustic impedance of the backing layer gradually decreases from the side closer to the piezoelectric layer to the side farther away from the piezoelectric layer.

9. The ultrasonic transducer according to claim 1, characterized in that, Also includes: A protective layer located on the surface of the matching layer facing away from the piezoelectric layer.

10. An ultrasonic scanning imaging logging tool, characterized in that, Includes the ultrasonic transmitting transducer as described in any one of claims 1 to 9.

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