A distributed phased array ultrasonic casing inspection device and method for downhole drilling

Abstract

This invention relates to the field of oil and gas field development technology, specifically to a downhole distributed phased array ultrasonic casing inspection device and method. The downhole distributed phased array ultrasonic casing inspection device includes: a detection system and a control system connected thereto. The detection system includes a cylindrical sealed structure and a distributed transducer disposed inside the cylindrical sealed structure. The distributed transducer includes at least three phased array ultrasonic probes arranged rotatably along the inner circumferential surface of the cylindrical sealed structure, and each phased array ultrasonic probe is connected to a corresponding circuit section. Each phased array ultrasonic probe completes the transmission and reception of the sound beam through a time delay law, realizing imaging scanning and inspection of the inner circumferential surface of the casing. The circuit section is used to excite the phased array ultrasonic probes and acquire and process the detection data from the phased array ultrasonic probes. The control system is used to receive the detection data from the corresponding phased array ultrasonic probe processed by each circuit section and stitch together an image according to the casing size and structure.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, specifically to a downhole distributed phased array ultrasonic casing inspection device and method. Background Technology

[0002] Downhole casing, a crucial component of oil and gas extraction, plays a vital role in supporting the wellbore, preventing collapse, isolating the formation, and protecting the flow channels for oil and gas. However, due to long-term operation in extremely complex environments characterized by high temperature, high pressure, corrosion, and mechanical stress, casing is highly susceptible to problems such as wall thinning, corrosion, deformation, and breakage. This damage leads to decreased wellbore integrity, severely reducing oilfield stability. Mild damage can cause well leakage, affecting extraction efficiency, while severe damage can result in catastrophic consequences such as blowouts, reservoir contamination, and formation loss, leading to significant environmental pollution and economic losses. Therefore, regularly conducting non-destructive testing on downhole casing is of paramount importance to ensuring oil well safety and normal production.

[0003] Currently, the more mature applications of casing and other pipe inspection in oilfields include ultrasonic testing, electromagnetic testing, magnetic flux leakage testing, downhole television testing, and radioactive isotope testing. Although these methods can meet the needs of casing defect detection to a certain extent, they still have different limitations in application. Ultrasonic testing is highly sensitive to defects inside casing and can accurately measure changes in casing wall thickness. However, it can only send a unidirectional sound beam and cannot perform area-type detection, resulting in low detection efficiency. Electromagnetic testing can quickly detect defects such as corrosion, holes, and cracks in casing and has a good effect on detecting the overall condition of casing. However, it can only detect the approximate location and range of casing defects and is not precise enough in determining the specific shape and size of casing defects, lacking quantitative methods. Downhole television testing can visually display the location and extent of casing damage through clear images. However, it can only see within the computer's field of view, and the imaging quality is poor under conditions of insufficient light or turbid downhole media. It also cannot detect internal defects in casing. Radioactive isotope testing can detect tiny cracks in casing with high detection accuracy and is suitable for harsh downhole environments. However, this detection method has a certain degree of radioactivity, the operation process is complex, it poses certain risks to personnel and the environment, and the detection cost is high. Strict adherence to protective regulations is required. Phased array ultrasonic testing technology is a new technology developed based on conventional ultrasonic testing. It employs an array of ultrasonic sensors and a delayed focusing excitation method to achieve a detection surface within a certain range and angle. The focusing of the sound beam improves detection sensitivity, giving the technology higher accuracy in casing inspection. However, with the increasing demand for deep and ultra-deep well inspection, phased array ultrasonic technology suffers from low detection efficiency and slow speed when used for 360° omnidirectional casing inspection.

[0004] Chinese invention patent application CN110672719A discloses a phased array ultrasonic testing device for in-pipe inspection. This device utilizes a combination of a phased array ultrasonic probe and front-end electronics, connected sequentially via coaxial cables, to achieve volumetric inspection of the pipe under test, effectively improving detection resolution and sensitivity. However, due to structural limitations, this phased array ultrasonic testing device is difficult to adapt to the complex high-temperature and high-pressure environment downhole, and the probe is prone to damage and failure, rendering it unusable for downhole operations. Furthermore, when applied to 360° circumferential inspection of downhole casing, this phased array ultrasonic testing device exhibits low efficiency and low detection accuracy. Summary of the Invention

[0005] The purpose of this invention is to provide a downhole distributed phased array ultrasonic casing inspection device to solve the problem that existing phased array ultrasonic inspection devices are difficult to adapt to complex working conditions such as high temperature and high pressure during downhole casing inspection, which leads to easy damage and failure of the ultrasonic probe.

[0006] To address the aforementioned problems, this invention proposes a downhole distributed phased array ultrasonic casing inspection device, the technical solution of which is as follows:

[0007] A downhole distributed phased array ultrasonic casing inspection device includes: an inspection system and a control system connected thereto. The inspection system includes a cylindrical sealed structure and a distributed transducer disposed inside the cylindrical sealed structure. The distributed transducer includes at least three phased array ultrasonic probes arranged rotatably along the inner circumferential surface of the cylindrical sealed structure, and each phased array ultrasonic probe is connected to a corresponding circuit section. Each phased array ultrasonic probe completes the transmission and reception of the sound beam through a time delay law, realizing imaging scanning and inspection of the inner circumferential surface of the casing. The circuit section is used to excite the phased array ultrasonic probes and to acquire and process the detection data of the phased array ultrasonic probes. The control system is used to receive the detection data of the corresponding phased array ultrasonic probe processed by each circuit section and to stitch together an image according to the size and structure of the casing.

[0008] Furthermore, the phased array ultrasonic probe includes 16 or 32 array elements, wherein the 16 or 32 array elements are convex arrays arranged uniformly in an arc shape.

[0009] Furthermore, the center frequency range of the phased array ultrasonic probe is 200kHz~5MHz, the length of the array element is 10mm, the spacing between adjacent array elements is 0.5~0.6mm, and the width of the array element is 0.3~0.4mm.

[0010] Furthermore, the phased array ultrasonic probe is evenly and uniformly arranged at equal intervals along the inner circumference of the cylindrical sealed structure.

[0011] Furthermore, the number of phased array ultrasonic probes is 3 to 4.

[0012] Furthermore, the cylindrical sealing structure includes a shell, the shell being made of a temperature- and pressure-resistant composite material, and a corrosion-resistant coating being provided on the outer circumferential surface of the shell.

[0013] Furthermore, the circuit section includes a phased array ultrasonic transmitting module, a receiving module, and a data acquisition module. The phased array ultrasonic transmitting module is connected to the receiving module and is used to excite the phased array ultrasonic probe to generate a sound beam. The sound beam interacts with the defect in the inner wall of the sleeve to generate an ultrasonic echo signal, which is then transmitted to the receiving module. The receiving module is connected to the data acquisition module and is used to receive the ultrasonic echo signal, convert it into an electrical signal, and transmit it to the data acquisition module. The data acquisition module is used to receive the electrical signal and use a parallel algorithm to sample and process the electrical signal in real time.

[0014] Furthermore, the detection system and the control system are connected via a photoelectric composite cable.

[0015] This invention also provides a downhole distributed phased array ultrasonic casing inspection method, based on the above-mentioned downhole distributed phased array ultrasonic casing inspection device, comprising the following steps:

[0016] Step S1: Place the cylindrical sealing structure coaxially inside the sleeve;

[0017] Step S2: The circuit short section excites the phased array ultrasonic probe. Each phased array ultrasonic probe completes the transmission and reception of the sound beam through the delay law, realizing the imaging scanning and detection of the inner circumferential surface of the sleeve.

[0018] Step S3: Each circuit segment acquires and processes the corresponding phased array ultrasonic probe detection data and transmits it to the control system;

[0019] In step S4, the control system receives the detection data of the corresponding phased array ultrasonic probe processed by each circuit segment and splices the images according to the size and structure of the sleeve to complete the detection.

[0020] Furthermore, each phased array ultrasonic probe completes the transmission and reception of the sound beam through a time delay law, realizing imaging scanning and detection of the inner circumferential surface of the sleeve, specifically including:

[0021] Using the axis of each phased array ultrasonic probe element as the 0° dividing line, the acoustic beam is controlled to scan the set angle range to the left and right of the dividing line, so that all phased array ultrasonic probes cover the 360° range of the inner circumference of the tube, completing a scan of the inner circumference of the tube.

[0022] Compared with the prior art, this application has the following beneficial effects:

[0023] This invention is an improved version, providing a downhole distributed phased array ultrasonic casing inspection device. It employs multiple phased array ultrasonic probes integrated into a cylindrical sealed structure to form a distributed transducer. Its closed cylindrical shape enables high inspection speed and meets the requirements for rapid, wide-area downhole inspection. Simultaneously, each phased array ultrasonic probe completes sound beam transmission and reception through a time-delay law, completing imaging scanning of the inner circumferential surface of the casing. This achieves wide-area sound field coverage, significantly improving the inspection range and efficiency. Furthermore, it exhibits high efficiency and accuracy during 360° full casing inspection, enabling early detection of internal casing defects, extending casing lifespan, and preventing downhole accidents. Moreover, this inspection device can adapt to the complex high-temperature and high-pressure environment of downhole operations, preventing interference from the complex downhole environment and electromagnetic fields, ensuring inspection accuracy, improving inspection speed, and enhancing the safety of oilfield operations.

[0024] The downhole distributed phased array ultrasonic casing inspection device of the present invention adopts a distributed transducer design. By rationally configuring multiple phased array ultrasonic probes, it achieves full circumferential coverage of the sound beam on the inner circumference of the casing. Simultaneously, each phased array ultrasonic probe is connected to a corresponding circuit section, which is used to excite the phased array ultrasonic probe and acquire and process the detection data. This allows each phased array ultrasonic probe to transmit data independently, significantly improving detection efficiency and accuracy. Furthermore, the downhole distributed phased array ultrasonic casing inspection device of the present invention employs a precision-machined cylindrical sealing structure, enabling stable operation in complex downhole environments and performing casing damage detection, thus improving the reliability of the inspection device.

[0025] The phased array ultrasonic probe has a center frequency range of 200kHz to 5MHz, an element length of 10mm, a spacing between adjacent elements of 0.5 to 0.6mm, and an element width of 0.3 to 0.4mm. This ensures the sensitivity and lateral resolution of the phased array ultrasonic probe elements and improves the detection capability of the phased array ultrasonic probe.

[0026] The phased array ultrasonic probe is evenly rotated and arranged at equal intervals along the inner circumference of the cylindrical sealing structure, which facilitates simple and effective scanning and detection of the inner circumference of the sleeve.

[0027] The phased array ultrasonic probes consist of 3 to 4 units, have a simple structure and small size, can be placed inside narrow downhole casings, and can ensure scanning and detection of the entire inner circumference of the casing.

[0028] The cylindrical sealing structure includes an outer shell made of a temperature- and pressure-resistant composite material. The outer circumferential surface of the outer shell is provided with a corrosion-resistant coating to prevent it from being affected by the complex downhole environment and electromagnetic interference, thereby improving detection accuracy.

[0029] The detection system and control system are connected by a photoelectric composite cable, enabling the device to operate stably in complex downhole environments and perform casing damage detection, thereby improving system reliability. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the downhole distributed phased array ultrasonic casing inspection device of this application;

[0031] Figure 2 This is a schematic diagram of the detection system in the downhole distributed phased array ultrasonic casing detection device of this application;

[0032] Figure 3 This is a schematic diagram of the distributed transducer in the downhole distributed phased array ultrasonic casing inspection device of this application.

[0033] Figure 4 This is a schematic diagram of the array element distribution structure of a phased array ultrasonic probe in the downhole distributed phased array ultrasonic casing inspection device of this application.

[0034] In the diagram, 1. Wellbore, 2. Annulus, 3. Casing, 4. Detection system, 5. Photoelectric composite cable, 6. Computer, 7. Circuit subsection, 8. Distributed transducer, 9. Phased array ultrasonic probe, 10. Array element. Detailed Implementation

[0035] As cited in the background section, existing phased array ultrasonic testing devices are difficult to adapt to complex working conditions such as high temperature and high pressure during downhole casing testing, which makes the ultrasonic probes very easy to be damaged and fail. Therefore, the present invention provides a downhole distributed phased array ultrasonic casing inspection device, comprising: an inspection system 4 and a control system connected thereto. The inspection system 4 is used to inspect the inner circumferential surface of the casing 3, and the control system is used to control the inspection system 4 to perform inspection and integrate the inspection data. The inspection system 4 includes a cylindrical sealing structure and a distributed transducer 8 disposed inside the cylindrical sealing structure. The distributed transducer 8 includes at least three phased array ultrasonic probes 9 arranged rotatably along the inner circumferential surface of the cylindrical sealing structure, and each phased array ultrasonic probe 9 is connected to a corresponding circuit section 7. Each phased array ultrasonic probe 9 completes the transmission and reception of the sound beam through a time delay law, realizing the change of focusing depth and sound beam orientation, so that all phased array ultrasonic probes 9 complete the imaging scan and inspection of the inner circumferential surface of the casing 3. The circuit section 7 is used to excite the phased array ultrasonic probes 9 and to collect and process the detection data of the phased array ultrasonic probes 9. The control system is used to receive the detection data of the corresponding phased array ultrasonic probe 9 processed by each circuit section 7 and to stitch together the images according to the size and structure of the casing 3. The downhole distributed phased array ultrasonic casing inspection device of the present invention adopts a distributed transducer 8 design. By rationally configuring multiple phased array ultrasonic probes 9, it achieves full circumferential coverage of the inner circumferential surface of the casing 3 through sound wave focusing and sound beam deflection. At the same time, each phased array ultrasonic probe 9 is connected to a corresponding circuit section 7. The circuit section 7 is used to excite the phased array ultrasonic probe 9 and to collect and process the detection data of the phased array ultrasonic probe 9, so that each phased array ultrasonic probe 9 can transmit data independently, which significantly improves the detection efficiency and accuracy. In addition, the downhole distributed phased array ultrasonic casing inspection device of the present invention adopts a precision-machined cylindrical sealing structure, which can operate stably in complex downhole environments and perform casing damage detection, thereby improving the reliability of the inspection device.

[0036] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0037] Specific embodiment 1 of the downhole distributed phased array ultrasonic casing inspection device of the present invention:

[0038] In this embodiment, as Figure 1 , 2 As shown in Figures 3 and 4, the downhole distributed phased array ultrasonic casing inspection device includes: an inspection system 4 and a control system connected thereto, which are connected via a photoelectric composite cable 5. The inspection system 4 includes a cylindrical sealed structure and a distributed transducer 8 disposed inside the cylindrical sealed structure. The distributed transducer 8 includes four phased array ultrasonic probes 9 arranged rotatably along the inner circumference of the cylindrical sealed structure. Each phased array ultrasonic probe 9 corresponds to independent signal transmission data, and each phased array ultrasonic probe 9 is connected to a circuit section 7. The circuit section 7 is connected to the phased array ultrasonic probe 9 via the photoelectric composite cable 5 and is also connected to the control system via the photoelectric composite cable 5. The photoelectric composite cable 5 is provided with a buffer layer and a protective layer to ensure the stability of data transmission.

[0039] Each phased array ultrasonic probe 9 transmits and receives sound beams using a time-delay rule, achieving imaging scanning and detection of the inner circumferential surface of the sleeve 3. Specifically, the control system controls the phased array ultrasonic probe 9 to change the deflection direction of the sound beam using a time-delay rule, controlling the sound beam to be incident on the inner wall of the sleeve 3 at different angles, completing a 360° circumferential coverage scan; simultaneously, it changes the focusing depth to detect deep defects inside the sleeve 3. Circuit section 7 is used to excite the phased array ultrasonic probe 9 and to acquire and process the detection data from the phased array ultrasonic probe 9; the control system is used to receive the detection data from the corresponding phased array ultrasonic probe 9 processed by each circuit section 7 and to stitch together images according to the size and structure of the sleeve 3. Here, the control system is a computer 6. During use, there is an annular space 2 between the casing 3 and the well wall 1. A cylindrical sealing structure is placed inside the downhole casing 3, so that the center of the cylindrical sealing structure coincides with the axial centerline of the casing 3. This ensures that the acoustic beam of each phased array ultrasonic probe 9 of the distributed transducer 8 is perpendicularly incident into the casing 3. The cylindrical sealing structure can further prevent the annular space 2 from damaging the phased array ultrasonic probe 9. At the same time, the diameter of the detection system 4 cannot exceed the inner diameter of the casing 3. Since it is necessary to detect downhole casings 3 with various inner diameters, in this embodiment, the diameter of the detection system 4 is ultimately selected to be 80 mm.

[0040] When inspecting the downhole casing 3, the more array elements 10 of the phased array ultrasonic probe 9, the stronger the focusing ability of the sound beam and the higher the lateral resolution. However, the size of the phased array ultrasonic probe 9 will also increase accordingly. Due to the limited space downhole, in this embodiment, the number of array elements 10 of the phased array ultrasonic probe 9 is ultimately selected as 16 or 32 array elements 10, and the 16 or 32 array elements 10 are arranged in a uniform arc-shaped convex array. Because debris in the annulus 2 will affect the sound waves, high-frequency probes are not suitable. Therefore, the center frequency range of the phased array ultrasonic probe 9 is 200kHz~5MHz, the length of the array element 10 is 10mm, the spacing between adjacent array elements 10 is 0.5~0.6mm, and the width of the array element 10 is 0.3~0.4mm. Here, each phased array ultrasonic probe 9 completes the transmission and reception of the sound beam through a time delay law. Specifically, each phased array ultrasonic probe 9 controls the time delay of the excitation and reception pulses of each array element 10 to change the phase relationship of the sound waves transmitted (or received) by the array element 10 reaching (or originating from) a certain point inside the casing 3. Among them, the material of the array element 10 of the phased array ultrasonic probe 9 is a modified piezoelectric composite material. This composite material can optimize the acoustic impedance through proportioning, reduce sound energy reflection, and is suitable for high-precision detection and multi-angle scanning required in downhole casing 3 inspection.

[0041] During testing, a large sector scanning angle is usually required to cover a sufficiently large area of ​​the inner wall of the sleeve 3. However, an excessively large angle will lead to a decrease in detection resolution. Therefore, in this embodiment, the axis of the array element 10 of the phased array ultrasonic probe 9 is used as the 0° dividing line. The acoustic beam is controlled to scan 50° to the left and right of the dividing line. Each phased array ultrasonic probe 9 can scan and cover a range of 100°. Four phased array ultrasonic probes 9 can cover a range of 360° and complete the scanning of the inner circumference of the sleeve 3.

[0042] In other embodiments, the distributed transducer 8 includes three phased array ultrasonic probes 9 arranged rotatably along the inner circumferential surface of the cylindrical sealed structure. During testing, the axis of the array element 10 of the phased array ultrasonic probe 9 is used as the 0° dividing line, and the sound beam is controlled to scan a range of 65° to the left and right of the dividing line. Each phased array ultrasonic probe 9 can scan and cover 130°, and the three phased array ultrasonic probes 9 can cover a range of 360° to complete the scan of the sleeve 3.

[0043] Specific embodiment 2 of the downhole distributed phased array ultrasonic casing inspection device of the present invention:

[0044] Based on the above-described technical concept of the present invention, or based on the specific embodiments of the present invention described above, another embodiment is provided below.

[0045] The phased array ultrasonic probes 9 can be uniformly rotated and arranged at unequal distances along the inner circumference of the cylindrical sealed structure. However, when the spacing between some adjacent phased array ultrasonic probes 9 is too large, it will cause some individual phased array ultrasonic probes 9 to have undetected areas. Conversely, when the spacing between some adjacent phased array ultrasonic probes 9 is too small, there will be a large number of repeated scanning areas. Therefore, in this embodiment, preferably, as... Figure 3 As shown, the phased array ultrasonic probe 9 is evenly and uniformly arranged at equal intervals along the inner circumference of the cylindrical sealing structure, which facilitates simple and effective scanning and detection of the inner circumference of the sleeve 3.

[0046] In this embodiment, the cylindrical sealing structure includes a shell made of a temperature- and pressure-resistant material, and a corrosion-resistant coating is provided on the outer circumferential surface of the shell. Due to the complex downhole environment, in order to protect the phased array ultrasonic probe 9, the shell is made of a pressure- and temperature-resistant material and is precision-machined to achieve a sealed installation.

[0047] Specific embodiment 3 of the downhole distributed phased array ultrasonic casing inspection device of the present invention:

[0048] Based on the above-described technical concept of the present invention, or based on the specific embodiments of the present invention described above, another embodiment is provided below.

[0049] In this embodiment, circuit section 7 includes a phased array ultrasonic transmitting module, a receiving module, and a data acquisition module. The phased array ultrasonic transmitting module is connected to the receiving module and is used to excite the phased array ultrasonic probe 9 to generate a sound beam. The sound beam interacts with the inner wall of the sleeve 3 to generate an ultrasonic echo signal, which is then transmitted to the receiving module. The receiving module is connected to the data acquisition module and is used to receive the ultrasonic echo signal, convert it into an electrical signal, and transmit it to the data acquisition module. The data acquisition module is used to receive the electrical signal and use a parallel algorithm to sample and process the electrical signal in real time. Finally, the processed electrical signal is transmitted to the computer 6 via the optoelectronic composite cable 5 to complete signal analysis, splicing, and data processing.

[0050] Specific embodiment 1 of the downhole distributed phased array ultrasonic casing inspection method of the present invention:

[0051] This application also provides a downhole distributed phased array ultrasonic casing inspection method, based on the above-mentioned downhole distributed phased array ultrasonic casing inspection device, including the following steps:

[0052] First, the cylindrical sealing structure is placed coaxially inside the sleeve 3;

[0053] Secondly, the circuit section 7 excites the phased array ultrasonic probe 9. Each phased array ultrasonic probe 9 completes the transmission and reception of the sound beam through the delay law, realizing the imaging scanning and detection of the inner circumferential surface of the sleeve 3.

[0054] Then, circuit section 7 acquires and processes the detection data from the phased array ultrasonic probe 9 and transmits it to the control system;

[0055] Finally, the control system receives the detection data of each phased array ultrasonic probe 9 processed by the receiving circuit section 7 and stitches the images according to the size and structure of the sleeve 3 to complete the detection.

[0056] Each phased array ultrasonic probe 9 completes the transmission and reception of the sound beam through a time delay law, realizing imaging scanning and detection of the inner circumferential surface of the sleeve 3, specifically including:

[0057] Using the axis of the central array element 10 of each phased array ultrasonic probe 9 as the 0° dividing line, the acoustic beam is controlled to scan the set angle range to the left and right of the dividing line so that all phased array ultrasonic probes 9 cover the 360° range of the inner circumference of the sleeve 3, completing the scan of the inner circumference of the sleeve 3.

[0058] Specifically, a method for downhole distributed phased array ultrasonic casing inspection includes the following steps:

[0059] First, place the cylindrical sealing structure inside the sleeve 3, so that the center of the cylindrical sealing structure coincides with the central axis of the sleeve 3;

[0060] Secondly, the computer 6 control circuit section 7 excites the phased array ultrasonic probe 9 through the phased array ultrasonic transmission module. Each phased array ultrasonic probe 9 uses the delay law to complete the transmission and reception of the sound beam, realizing the imaging scanning and detection of the inner circumferential surface of the sleeve 3.

[0061] Then, circuit section 7 acquires and processes the detection data from the phased array ultrasonic probe 9 through the receiving module and data acquisition module, and transmits it to the computer 6;

[0062] Finally, the computer 6 receives the detection data of each phased array ultrasonic probe 9 processed by the circuit section 7 and stitches the images according to the size and structure of the sleeve 3 to complete the detection of the sleeve 3.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A downhole distributed phased array ultrasonic casing inspection device, characterized in that, Downhole casing for variable diameter in deep and ultra-deep wells includes: a detection system (4) and a control system connected thereto. The detection system (4) includes a cylindrical sealing structure and a distributed transducer (8) disposed inside the cylindrical sealing structure. The distributed transducer (8) includes at least three phased array ultrasonic probes (9) arranged in a rotating manner along the inner circumference of the cylindrical sealing structure, and each phased array ultrasonic probe (9) is connected to a corresponding circuit section (7). Each phased array ultrasonic probe (9) completes the transmission and reception of the sound beam through a time delay law, realizing the change of focusing depth and sound beam orientation. To enable all phased array ultrasonic probes (9) to complete imaging scanning and detection of the inner circumferential surface of the sleeve; the circuit section (7) is used to excite the phased array ultrasonic probes (9) and collect and process the detection data of the phased array ultrasonic probes (9); the control system is used to receive the detection data of the corresponding phased array ultrasonic probes (9) processed by each circuit section (7) and splice the images according to the size and structure of the sleeve (3); the phased array ultrasonic probes (9) include 16 array elements (10) or 32 array elements (10), and the 16 array elements (10) or 32 array elements (10) are convex arrays arranged uniformly in an arc shape; The phased array ultrasonic probes (9) are evenly and uniformly arranged at equal intervals along the inner circumference of the cylindrical sealed structure; the number of phased array ultrasonic probes (9) is 3 to 4. The cylindrical sealing structure includes a shell, the shell being made of a temperature and pressure resistant material, and a corrosion resistant coating being provided on the outer circumference of the shell; the center frequency range of the phased array ultrasonic probe (9) is 200kHz~5MHz, the length of the array element (10) is 10mm, the spacing between adjacent array elements (10) is 0.5~0.6mm, and the width of the array element (10) is 0.3~0.4mm; the circuit section (7) includes a phased array ultrasonic transmitting module, a receiving module, and a data acquisition module; the phased array ultrasonic transmitting module is connected to the receiving module and is used to excite the phased array ultrasonic probe (9) to generate a sound beam, the sound beam interacts with the inner wall of the sleeve (3) to generate an ultrasonic echo signal, and transmits the ultrasonic echo signal to the receiving module; the receiving module is connected to the data acquisition module and is used to receive the ultrasonic echo signal, convert the ultrasonic echo signal into an electrical signal, and transmit it to the data acquisition module; the data acquisition module is used to receive the electrical signal and use a parallel algorithm to sample and process the electrical signal in real time.

2. The downhole distributed phased array ultrasonic casing inspection device according to claim 1, characterized in that, The detection system (4) and the control system are connected by a photoelectric composite cable (5).

3. A method for downhole distributed phased array ultrasonic casing inspection, characterized in that, Based on the downhole distributed phased array ultrasonic casing inspection device as described in claim 1 or 2, the following steps are included: Step S1: Place the cylindrical sealing structure coaxially inside the sleeve (3); Step S2, the circuit short section (7) excites the phased array ultrasonic probe (9), and each phased array ultrasonic probe (9) completes the transmission and reception of the sound beam through the delay law, realizing the imaging scanning and detection of the inner circumferential surface of the sleeve (3); In step S3, each circuit segment (7) acquires and processes the detection data of the corresponding phased array ultrasonic probe (9) and transmits it to the control system; In step S4, the control system receives the detection data of the corresponding phased array ultrasonic probe (9) processed by each circuit segment (7) and performs splicing imaging according to the size and structure of the sleeve (3) to complete the detection.

4. The downhole distributed phased array ultrasonic casing inspection method according to claim 3, characterized in that, Each phased array ultrasonic probe (9) completes the transmission and reception of the sound beam through the delay law, realizing the imaging scanning and detection of the inner circumferential surface of the sleeve (3), specifically including: Using the axis of the array element (10) of each phased array ultrasonic probe (9) as the 0° dividing line, the acoustic beam is controlled to scan the set angle range to the left and right of the dividing line so that all phased array ultrasonic probes (9) cover the 360° range of the inner circumference of the sleeve (3) and complete the scanning of the inner circumference of the sleeve (3).

Images