A well wall ultrasonic imaging logging transducer and its measurement system

Abstract

The present invention provides a borehole ultrasonic imaging logging transducer, comprising a transmitting transducer (11) and a receiving transducer (12); wherein the transmitting transducer (11) comprises a piezoelectric material layer (102), an acoustically transparent matching layer (105), a backing layer (204) and an insulating sealing layer (101); the piezoelectric material layer (102) comprises a piezoelectric phase and a polymer phase, the piezoelectric phase is a short cylindrical piezoelectric material, and the upper and lower surfaces of the piezoelectric phase are respectively provided with a plurality of circular through holes of equal size, the aperture of the circular through hole being greater than the hole spacing of the circular through hole; the circular through hole contains a polymer phase of the same size as the internal space of the circular through hole, and the polymer phase is fixedly connected to the piezoelectric phase. The present invention improves the adaptability of the transducer in the harsh environment of ultra-high temperature and ultra-high pressure by means of a novel design of the piezoelectric material structure of the transducer; and reduces the volume of the transducer by means of an optimized design of the backing layer.

Description

Technical Field

[0001] The invention relates to the technical field of well wall ultrasonic imaging in drilling and logging construction, and in particular to a well wall ultrasonic imaging logging transducer and a measuring system thereof. Background Art

[0002] In recent years, with the rapid increase in global oil demand year by year, the exploration and development of unconventional oil and gas reservoirs such as shale gas and coalbed methane in oil exploration has become increasingly important, and drilling logging technology in highly deviated wells, especially horizontal wells, has also been very active. In order to find oil and gas reservoirs and improve the production capacity of single wells, it is necessary to clarify the characteristics of the cracks in the target layer, such as the inclination, orientation, density, and their distribution, formation anisotropy, and geostress distribution characteristics of the target layer, such as shale gas formations. Ultrasonic imaging logging technology can provide well wall image information, crack distribution characteristics, well diameter size, mud sound velocity, etc., which provides strong technical support for the exploration and development of oil and gas resources.

[0003] The working principle of borehole ultrasonic imaging logging technology is that in the borehole, the transmitting transducer of the measuring instrument generates azimuthal sound waves, which propagate to the borehole wall interface through the mud, generate reflected sound wave signals, and then are received by the receiving transducer. Due to the different wave impedances of different lithologies, the strength of the reflected signals generated is different, which can reflect the formation information. Since the downhole measuring tools (drilling tools or logging instruments, etc.) can rotate 360 ​​degrees, this method can be used to achieve 360-degree azimuthal sound wave imaging measurement around the well, recognize the borehole wall image, and understand the formation information. According to the arrival time of the first wave of the reflected sound wave signal, after signal processing and analysis, the mud sound velocity and well diameter information can be calculated.

[0004] The ultrasonic imaging logging transducer is mainly composed of a piezoelectric material layer, an acoustically transparent matching layer, a backing layer, and an insulating sealing layer. The transducer mainly utilizes the thickness vibration mode of the piezoelectric material, and the operating frequency mainly depends on the thickness of the piezoelectric material. Piezoelectric materials currently generally use piezoelectric ceramic materials and piezoelectric composite materials. While generating thickness mode vibrations, piezoelectric ceramic materials also generate vibrations such as radial modes and bending modes, which have a certain influence on the working frequency band of thickness mode vibrations. The acoustic impedance of commonly used piezoelectric ceramics is generally around 30 MRayl, which is greatly different from the acoustic impedance of the fluid in the borehole, making it difficult to match and having low acoustic wave radiation efficiency. Although piezoelectric ceramic materials have certain advantages in manufacturing and high pressure resistance, due to the disadvantages of limited working bandwidth, poor impedance matching, and low radiation efficiency, piezoelectric ceramic ultrasonic imaging logging transducers have certain limitations in formation adaptability. Piezoelectric composite materials use a combination of piezoelectric phase and polymer phase, which can effectively highlight the thickness vibration mode, suppress radial mode and bending mode, increase the working bandwidth, and broaden the scope of application of the formation. This makes this type of transducer have a good application prospect and become a development trend of downhole ultrasonic imaging logging transducers. However, piezoelectric composite ultrasonic transducers also have difficulties such as complex manufacturing process and low product consistency. At present, the most widely used piezoelectric composite materials for ultrasonic imaging logging transducers are types 1-3. Due to the ultra-high temperature (such as 250°C) and ultra-high pressure (such as 200MPa) underground, the electrode surface of the piezoelectric ceramic is easily dislocated and separated from the piezoelectric ceramic silver layer, resulting in a decrease in transducer performance, partial or even complete failure. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a well wall ultrasonic imaging logging transducer and a measuring system thereof.

[0006] In the first aspect, the present invention provides a well wall ultrasonic imaging logging transducer, comprising: a piezoelectric material layer, a sound-transmitting matching layer, a backing layer and an insulating sealing layer; the piezoelectric material layer, the sound-transmitting matching layer and the backing layer are stacked in sequence, and the stacked parts are fixed and bonded by glue; the top surface of the piezoelectric material layer is bonded to the sound-transmitting matching layer; the bottom surface of the piezoelectric material layer is bonded to the backing layer; the piezoelectric material layer, the sound-transmitting matching layer and the backing layer are accommodated in the insulating sealing layer; the piezoelectric material layer is connected to the downhole circuit through a wire electrode; the piezoelectric material layer comprises a piezoelectric phase and a polymer phase, the piezoelectric phase is a short cylindrical piezoelectric material, and the upper and lower surfaces of the piezoelectric phase are respectively provided with a plurality of circular through holes of equal size, and the aperture of the circular through hole is larger than the hole spacing of the circular through hole; the circular through hole accommodates a polymer phase of the same size as the internal space of the circular through hole, and the polymer phase is fixedly connected to the piezoelectric phase.

[0007] Preferably, the material of the piezoelectric phase is a piezoelectric ceramic material or a piezoelectric single crystal material.

[0008] Preferably, the backing layer includes a cylindrical structure part and a conical structure part; the top surface of the cylindrical structure part and the bottom surface of the conical structure part are in the same plane; the height of the cylindrical structure part and the conical structure part are both half the wavelength, and the wavelength is the wavelength of the ultrasonic wave propagating in the backing layer; the material of the backing layer is specifically a mixture of heavy metal powder particles and polymer materials.

[0009] Preferably, the structure of the acoustically transparent matching layer is a short cylinder, and the upper and lower surfaces of the acoustically transparent matching layer are equal in size to the upper and lower surfaces of the piezoelectric material layer; the thickness of the acoustically transparent matching layer is a quarter of the wavelength, and the wavelength is the wavelength of the ultrasonic wave propagating in the matching layer.

[0010] Preferably, the insulating sealing layer is made of insulating sealing material by potting it in a special mold.

[0011] Preferably, the wire electrode includes a first electrode wire and a second electrode wire, the first electrode wire and the second electrode wire are independent of each other, one end of the first electrode wire is fixedly connected to the upper surface of the piezoelectric phase, one end of the second electrode wire is fixedly connected to the lower surface of the piezoelectric phase, and the other ends of the first electrode wire and the second electrode wire extend and are fixed on the surface of the insulating sealing layer.

[0012] In the second aspect, the present invention provides a measurement system for well wall ultrasonic imaging logging, comprising: a transducer;

[0013] Preferably, it also includes: a downhole circuit unit and a mechanical unit; wherein the transducer and the downhole circuit unit are fixed in the internal components of the mechanical unit and connected to external equipment through the mechanical unit; the transducer and the downhole circuit unit are interconnected through wire electrodes; the downhole circuit unit includes: a pulse transmitting circuit module, a receiving circuit module, an acquisition processing module and a storage and transmission module.

[0014] The present invention improves the adaptability of the transducer in harsh environments of ultra-high temperature and ultra-high pressure by designing a new type of transducer piezoelectric material structure; and reduces the volume of the transducer by optimizing the design of the backing layer. The measurement system can be used to obtain acoustic wave image information of the borehole wall, mud sound velocity and well diameter information of small borehole deep wells and ultra-deep wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a cross-sectional view of a transducer according to an embodiment of the present invention;

[0016] Figure 2 A cross-sectional view of a transducer using a backing layer with a novel structure according to an embodiment of the present invention;

[0017] Figure 3 A top view of a piezoelectric material layer of a transducer according to an embodiment of the present invention;

[0018] Figure 4It is a top view of the piezoelectric material layer of a common transducer;

[0019] Figure 5 The admittance performance of the piezoelectric material layer of the transducer of the present invention and the common piezoelectric material layer in a free state in the air;

[0020] Figure 6 A schematic diagram of a wellbore ultrasonic imaging logging measurement system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0022] Embodiment 1 is a well wall ultrasonic imaging logging transducer provided by the present invention, such as Figure 1 As shown, the transducer includes a piezoelectric material layer 102, an acoustically transparent matching layer 105, a backing layer 104 and an insulating sealing layer 101; the piezoelectric material layer 102, the acoustically transparent matching layer 105 and the backing layer 104 are stacked in sequence, and the stacked parts are fixed and bonded by glue; the top surface of the piezoelectric material layer 102 is bonded to the acoustically transparent matching layer 105; the bottom surface of the piezoelectric material layer 102 is bonded to the backing layer 104; the piezoelectric material layer 102, the acoustically transparent matching layer 105 and the backing layer 104 are accommodated in the insulating sealing layer 101; the piezoelectric material layer 102 is connected to the downhole circuit 40 through the wire electrode 103; as shown Figure 3 As shown, the present invention proposes the basic structure of a 3-1 type piezoelectric composite material, which is in the shape of a cylindrical piezoelectric ceramic material. A number of small holes are drilled in the cylinder, and the small holes are not connected to each other and are perpendicular to the surface of the cylinder. Then the small holes are filled with polymers, such as fluororubber, silicone rubber, epoxy resin, etc., to obtain a 3-1 type piezoelectric composite material. If a piezoelectric single crystal is used as the piezoelectric phase, the composite material has better high-temperature characteristics. The 3-1 type piezoelectric composite material is characterized in that the electrode surface is easy to weld, and there is no need to bond the electrode surface separately or sputter the electrode surface, which optimizes the manufacturing process. More importantly, the volume expansion difference between the polymer phase and the piezoelectric ceramic phase caused by high temperature and high pressure can be avoided, which causes the electrode surface to peel off and cause the transducer performance to decline.

[0023] Figure 3 In the figure, the structure of the 3-1 piezoelectric composite material is as follows: the structure is a short cylindrical piezoelectric phase with a diameter of 38 mm and a thickness of 5 mm. The circular through holes are evenly distributed on the upper and lower surfaces of the piezoelectric phase. The diameter of the circular through holes is 2 mm, and the center distance between the circular through holes is 3 mm. The polymer phase fills the internal space formed by each circular through hole. The relative volume ratio of the polymer to the entire piezoelectric material layer is about 33.5%. The piezoelectric material is PZT5 piezoelectric ceramic, and the polymer material is epoxy resin. In order to highlight the application advantages of the 3-1 piezoelectric composite transducer in the present invention in well logging, we analyzed the 3-1 piezoelectric composite layer of the same size (such as Figure 3 as shown) and a piezoelectric ceramic material layer of a conventional structure (such as Figure 4 (shown) is the admittance performance in the free state in air. Figure 5 The conductivity-frequency curve comparison of two piezoelectric materials in the frequency range of 200-400kHz. The dotted line in the figure represents the conductivity-frequency curve of the 3-1 piezoelectric composite material, and the solid line represents the conductivity-frequency curve of the piezoelectric ceramic material with a common structure. It can be seen from the figure that the 3-1 piezoelectric composite material has a wider frequency band and a higher conductivity peak. And similarly, the 3-1 piezoelectric composite material has a good effect on suppressing the bending mode of the piezoelectric material transducer.

[0024] The backing layer 104 is bonded to the bottom of the piezoelectric material 102. The backing layer 104 is generally made of heavy metal powder particles and polymer materials mixed in a certain proportion. The heavy metal material includes metal tungsten powder, and the polymer materials include but are not limited to epoxy resin, fluororubber, polyurethane, etc. Different proportions of the backing layer 104 have different absorption and attenuation of sound waves. Generally speaking, the higher the proportion of metal particles and the more uniform the mixing, the greater the sound attenuation. Since the diameter of metal particles has different absorption and attenuation of sound waves of different frequencies, the diameter of the metal particles in the backing layer of the piezoelectric crystal is also different for different resonant frequencies. Generally, the higher the frequency value, the smaller the diameter value of the metal particles. In addition, the shape of the backing layer 104 is also an important factor affecting sound attenuation. The backing layer 104 is generally cylindrical.

[0025] Among them, preferably; the present invention proposes a backing layer 204 that combines a cylindrical and conical shape, see Figure 2 The diameter of the cylinder is slightly larger than the diameter of the piezoelectric material layer, and the height is half a wavelength. The diameter of the bottom surface of the cone is the same as the diameter of the cylinder, and the height is half a wavelength, which is the wavelength of the ultrasonic wave propagated by the backing layer. This non-uniform thickness structure can avoid standing waves excited by equal thickness backings, effectively achieve sound attenuation, and can also achieve bandwidth expansion through multi-resonance of different thicknesses. It can also save precious metal materials (such as tungsten powder). More importantly, it can reduce the height and volume of the backing layer 104, which is conducive to the assembly of the transmitting transducer 10 on a measuring device with a smaller diameter, and adapt to the downhole acoustic measurement of small-diameter detection instruments.

[0026] The top surface of the piezoelectric material 102 is bonded to the sound-transmitting layer 105 , so that the sound waves can be effectively transmitted through the sound-transmitting layer 105 to the radiation medium (such as mud), thereby reducing the energy loss during the transmission process.

[0027] Preferably, the structure of the acoustically transparent matching layer 105 is a short cylinder, and the upper and lower surfaces of the acoustically transparent matching layer 105 are equal in size to the upper and lower surfaces of the piezoelectric material layer 102; the thickness of the acoustically transparent matching layer is a quarter wavelength, which is the wavelength of the ultrasonic wave propagating in the matching layer. Generally, the wave impedance of the acoustically transparent matching layer 105 material is between the piezoelectric material layer 102 and the radiation medium (such as mud, water), and can be a mixture of epoxy resin, polyurethane, fluororubber and other adhesives and powder materials. By adjusting the ratio of adhesive to powder, the density of powder, etc., the optimal acoustic impedance can be obtained.

[0028] The insulating sealing layer 101 mainly plays the role of insulating and sealing.

[0029] Preferably, the insulating sealing layer 101 can be designed in a corresponding shape according to the specific structural features of the external device, or can be implemented by encapsulating the insulating sealing material in a special mold. The insulating sealing material is generally epoxy resin, silicone rubber, polyetheretherketone, etc., but is not limited to such materials.

[0030] The wire electrode 103 includes a first electrode wire and a second electrode wire, the first electrode wire and the second electrode wire are independent of each other, one end of the first electrode wire is fixedly connected to the upper surface of the piezoelectric phase, one end of the second electrode wire is fixedly connected to the lower surface of the piezoelectric phase, and the other ends of the first electrode wire and the second electrode wire extend and are fixed on the surface of the insulating sealing layer 101.

[0031] Embodiment 2 is a wellbore ultrasonic imaging logging measurement system provided by the present invention, such as Figure 6 As shown, the measuring system 40 is placed in a borehole 50 filled with mud, and the well wall is 51. The measuring device 40 mainly consists of three parts. The first part is the transducer unit 10, which mainly includes a transmitting transducer 11 and a receiving transducer 12. The second part is the downhole circuit unit 20, which includes a pulse transmitting circuit module, a receiving circuit module, a collection and processing module, and a storage and transmission module. The third part is the mechanical unit 30, which is mainly the installation framework of the transducer combination and the downhole circuit. Through the mechanical unit 30, it can be connected with other downhole instruments.

[0032] The present invention proposes a new type of piezoelectric composite ultrasonic transducer, which aims to make it more adaptable to harsh environments such as ultra-high temperature and ultra-high pressure underground through the new structural design of the piezoelectric phase and the polymer phase; through the new structural design of the backing layer, the height and volume of the transducer can be reduced, making it more suitable for ultrasonic measurement of the wellbore wall of small boreholes in ultra-deep wells. 360-degree ultrasonic imaging scanning can obtain the azimuthal formation image information of the wellbore wall, the wellbore diameter value and mud sound velocity of different well depths. The transducer has the characteristics of high temperature resistance, high pressure resistance, wide bandwidth, high resolution, and small size. The above advantages are more conducive to the detection of unconventional oil and gas reservoirs in deep, ultra-deep and long horizontal sections of highly deviated wells, and can further expand the engineering application function of ultrasonic imaging logging technology.

[0033] The above specific implementation methods further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific implementation methods of the present invention and are 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 well wall ultrasonic imaging logging transducer, comprising a wire electrode (103), a transmitting transducer (11) and a receiving transducer (12); wherein: The transmitting transducer (11) comprises a piezoelectric material layer (102), an acoustically transparent matching layer (105), a backing layer (204) and an insulating sealing layer (101); characterized in that the piezoelectric material layer (102) comprises a piezoelectric phase and a polymer phase, the piezoelectric phase is a short cylindrical piezoelectric material, and the upper and lower surfaces of the piezoelectric phase are respectively provided with a plurality of circular through holes of equal size, and the aperture of the circular through holes is greater than the hole pitch of the circular through holes; the circular through holes contain the polymer phase of the same size as the internal space of the circular through holes, and the polymer phase is fixedly connected to the piezoelectric phase; the backing layer (204) comprises a cylindrical structure part and a conical structure part; the top surface of the cylindrical structure part and the bottom surface of the conical structure part are in the same plane; the height of the cylindrical structure part and the conical structure part are both half a wavelength, and the wavelength is the backing layer (204). The material of the backing layer (204) is specifically a mixture of heavy metal powder particles and polymer materials; the structure of the acoustically transparent matching layer (105) is a short cylinder, and the upper and lower surfaces of the acoustically transparent matching layer (105) are equal in size to the upper and lower surfaces of the piezoelectric material layer (102); the thickness of the acoustically transparent matching layer is one quarter of a wavelength, and the wavelength is the wavelength of the ultrasonic wave propagating in the acoustically transparent matching layer; the wire electrode (103) comprises a first electrode wire and a second electrode wire, the first electrode wire and the second electrode wire are independent of each other, one end of the first electrode wire is fixedly connected to the upper surface of the piezoelectric phase, one end of the second electrode wire is fixedly connected to the lower surface of the piezoelectric phase, and the other ends of the first electrode wire and the second electrode wire extend and are fixed to the surface of the insulating sealing layer (101).

2. The transducer according to claim 1, characterized in that The material of the piezoelectric phase is a piezoelectric ceramic material or a piezoelectric single crystal material.

3. The transducer according to claim 1, characterized in that The insulating sealing layer (101) is made by encapsulating the insulating sealing material in a special mold.

4. A measurement system for well wall ultrasonic imaging logging, characterized in that: include: The transducer (10) as claimed in claim 1.

5. The measuring system according to claim 4, characterized in that It also includes a downhole circuit unit (20) and a mechanical unit (30); the transducer (10) and the downhole circuit unit (20) are fixed in the internal components of the mechanical unit (30), and are connected to external equipment through the mechanical unit (30); the transducer (10) and the downhole circuit unit (20) are connected to each other through the wire electrode (103); the downhole circuit unit (20) includes: a pulse transmission circuit module, a receiving circuit module, a collection processing module and a storage and transmission module.

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