Rotary annulus high-precision electromagnetic tomography measuring device and working method

Abstract

The invention provides a rotary annulus high-precision electromagnetic tomography measuring device and a working method. The device is composed of an excitation source module, a rotary coil array module, a signal acquisition and processing module, a data fusion module and an image display module. Wherein the rotary coil array module comprises a track structure, an annular supporting frame and a middle-layer gear structure, the track structure is installed on the inner pipeline, the annular supporting frame is connected with a track, the middle-layer gear structure is installed on the annular supporting frame, the middle driving structure comprises a driving motor and a gear, the driving motor is installed on the outer wall of the pipeline, and the gear is connected with the driving motor. A gear is mounted on a shaft of the driving motor and meshed with the middle-layer gear structure, so that the annular supporting frame is driven to rotate around the inner pipeline along the track structure. High precision and measurement imaging of underground multiphase flow measurement are realized through rotary coil array design, mixed frequency excitation, high-frequency signal acquisition and an image fusion technology.

Description

Technical Field

[0001] The invention belongs to the technical field of downhole measuring devices, and in particular relates to a rotary annular space high-precision electromagnetic tomography measuring device and a working method. Background Art

[0002] In the measurement of multiphase flow in oil and gas wells, accurate and real-time detection of fluid composition and flow state in the well is crucial for oil and gas field development, production management, equipment maintenance, etc. At present, the mainstream downhole multiphase flow measurement devices are mostly based on electromagnetic tomography technology. Electromagnetic tomography technology arranges a series of electromagnetic coils to transmit electromagnetic waves to the target area and receive response signals generated by different substances to reconstruct the distribution and flow state of the fluid.

[0003] However, the underground environment is usually characterized by high temperature and pressure, multi-phase complex fluid media, high noise interference, etc. The existing electromagnetic tomography technology faces great challenges in terms of measurement accuracy, image resolution and real-time performance. In addition, the underground space is limited, and the coil design and layout of the existing technology often lead to insufficient signal acquisition, which in turn affects the accuracy of image reconstruction and the reliability of measurement results.

[0004] At present, the electromagnetic tomography technology used mostly adopts fixed coils, which is difficult to flexibly respond to the complex changes of multiphase flow, and the frequency and angle of signal acquisition are limited, resulting in poor real-time measurement results in high dynamic environments.

[0005] Technical solution of prior art 1 Fixed electromagnetic tomography is one of the technologies currently widely used in downhole multiphase flow measurement. This solution usually uses a ring-shaped electromagnetic coil to transmit and receive electromagnetic signals around the measurement area. Through the interaction between multiple coils, the electromagnetic field distribution is used to reconstruct the tomographic image of the fluid. The key to this technology is to capture the changes in the electromagnetic field through the arrangement of sensor coils and identify fluids in different phases through imaging algorithms.

[0006] Disadvantages of the prior art 1 The coil arrangement is single and the measurement accuracy is limited. This technology uses a fixed annular coil arrangement, with a limited number of sensors and a fixed arrangement, which makes it difficult to adapt to the dynamic distribution of complex fluids in the well. This will result in the inability to capture local changes in the fluid, affecting the fineness of the image and the overall measurement accuracy.

[0007] All-round measurement cannot be achieved. Since the coil is fixed at a specific angle, the device can only obtain electromagnetic signals from a limited angle, resulting in incomplete information in three-dimensional space. Especially in complex downhole multiphase flow environments, it is impossible to perform comprehensive dynamic measurements of fluid changes in different directions.

[0008] Single frequency excitation, poor fluid recognition ability. The device mostly uses a single frequency electromagnetic signal excitation, which makes it difficult to fully identify multiple fluid components, especially in multiphase flow where the electromagnetic response differences of different components are not obvious, resulting in a decrease in recognition accuracy.

[0009] Technical solution of prior art 2 The multi-frequency electromagnetic tomography device uses multi-frequency excitation technology to obtain fluid information of different phases by emitting electromagnetic signals of multiple frequencies. The coil can work at multiple frequencies, and the system analyzes and reconstructs the fluid components and flow state of multiphase flow by receiving electromagnetic signals at different frequencies. Multi-frequency excitation technology can improve the accuracy of fluid identification and is suitable for different types of downhole environments.

[0010] Disadvantages of the second prior art The coil is fixed and the angle coverage is insufficient. Although multi-frequency excitation improves the accuracy of fluid identification, the solution still relies on a fixed coil arrangement and cannot measure from multiple angles. This leads to insufficient spatial measurement coverage in the complex dynamic environment of multiphase flow underground, especially the low imaging accuracy in three-dimensional space, and it is impossible to obtain a full range of measurement results.

[0011] The data acquisition speed is limited. Although this technology obtains more information through multi-frequency excitation, the acquisition frequency is not high enough. In the fast-flowing multiphase flow environment underground, it is difficult to achieve real-time data acquisition and processing, resulting in a certain lag and error in the measurement results.

[0012] The signal fusion algorithm is complex and the processing efficiency is low. The multi-frequency signal fusion processing algorithm in this scheme is complex. Although it can improve the measurement accuracy in theory, in practical applications, the measurement real-time performance is insufficient due to the slow signal processing speed. Especially in high-dynamic scenarios with large data volumes, the efficiency of the algorithm processing is significantly reduced.

[0013] In summary, the existing electromagnetic tomography technology has the following problems: (1) Insufficient coil design and measurement accuracy: The coil design of existing fixed electromagnetic tomography devices is usually a fixed circular arrangement with a small number of coils, which makes it difficult to capture subtle local changes in the fluid, resulting in low spatial resolution and overall accuracy of the measurement.

[0014] (2) The measurement angle is limited and cannot fully cover the three-dimensional space: The fixed coils in the existing technology cannot transmit and receive electromagnetic signals from multiple angles and can only cover a limited angle, resulting in the inability to fully obtain the fluid changes in the three-dimensional space. Especially in a dynamic multiphase flow environment, the measurement results lack all-round three-dimensional information.

[0015] (3) Single frequency excitation leads to insufficient medium identification ability: Traditional electromagnetic tomography devices usually use single frequency electromagnetic waves for excitation, which makes it difficult to accurately image high conductivity materials (such as salt water, metals, etc.) and low conductivity materials (such as oil, gas, etc.) at the same time, resulting in weak identification ability of different media and reduced measurement accuracy.

[0016] (4) Insufficient image resolution and accuracy: Due to the use of single frequency excitation, the electromagnetic tomography images generated by existing devices have great limitations in resolution and accuracy, and cannot clearly present the complex fluid distribution in the downhole multiphase flow, resulting in insufficient image information and blurred imaging results.

[0017] (5) The data acquisition frequency is low and high-frequency signals cannot be collected efficiently: In the existing technology, due to the low data acquisition frequency, especially in the dynamic multiphase flow environment underground, high-frequency signals cannot be effectively captured, resulting in incomplete collected signals, which affects the accuracy and real-time performance of the overall measurement.

[0018] (6) Complex signal processing and poor real-time performance: In multi-frequency excitation devices, due to the complexity of the signal fusion processing algorithm, the existing technology has a slow processing speed and insufficient real-time performance when facing a large amount of data, making it difficult to quickly respond to the dynamic changes of downhole multiphase flow. Summary of the invention

[0019] The purpose of the present invention is to solve the defects of the above-mentioned prior art and provide a rotating annular high-precision electromagnetic tomography measurement device and a working method.

[0020] The present invention adopts the following technical solution: A rotating annulus high-precision electromagnetic tomography measuring device is composed of an excitation source module, a rotating coil array module, a signal acquisition and processing module, a data fusion module and an image display module. The excitation source module is connected to the coil array in the rotating coil array module, the rotating array module is connected to the signal acquisition and processing module, the signal acquisition and processing module is connected to the data fusion module, and the data fusion module is connected to the image display module;

[0021] Among them, the rotating coil array module includes a track structure, an annular support frame, and an intermediate gear structure. The track structure is installed on the inner pipe, the annular support frame is connected to the track, the intermediate gear structure is installed on the annular support frame, and the intermediate driving structure includes a driving motor and a gear. The driving motor is installed on the outer wall of the pipe, and the gear is installed on the driving motor shaft. The gear is meshed with the intermediate gear structure, thereby driving the annular support frame to rotate around the inner pipe along the track structure.

[0022] Furthermore, the coil array in the rotating coil array module is distributed along the circumference of the inner pipe, the central angle between two adjacent coils is 30°, and the center of each coil faces the inner pipe.

[0023] Furthermore, the rotating coil array module is composed of 12 coils, and the coils rotate at a center angle of 15° each time.

[0024] Furthermore, the track structure is an annular track fixedly mounted on the outside of the inner pipe and arranged around the inner pipe. There is an annular recessed track on the inner pipe corresponding to the annular track, and balls are installed in the annular track and the recessed track.

[0025] Furthermore, the annular support frame is composed of a vertical support column and an annular structure. One end of the vertical support column is connected to the track structure, and the other end of the vertical support column is connected to the annular structure, and the installation positions of the vertical support column are evenly distributed along the circumference.

[0026] Furthermore, 12 electromagnetic coil mounting points are installed on the annular structure.

[0027] Furthermore, the middle layer gear structure is installed in the middle of the vertical support column of the annular support frame, and the middle layer gear structure is an annular structure of a certain thickness with gears.

[0028] Furthermore, the angle control sensor is installed on the electromagnetic coil installation point of the annular structure of the annular support frame.

[0029] A working method of a rotating annular high-precision electromagnetic tomography measuring device, comprising: Step 1. First, the excitation source module transmits high-frequency 10MHz and low-frequency 100KHz electromagnetic signals.

[0030] Step 2. The rotating coil array module uses a multi-channel switching circuit to enable one excitation coil and 11 detection coils to work simultaneously at the same time. The rotating coil array module will transmit signals to the annular multiphase flow area. After the excitation signal is transmitted, the signal acquisition and processing module begins to collect response signals from different angles.

[0031] Step 3. For the collected high-frequency signal, the signal acquisition and processing module uses a filter to remove noise, measures the cycle of the collected signal in real time, and dynamically adjusts the delay. When the high-frequency signal passes through the zero point, the zero point detection circuit triggers the delay circuit, which triggers the microcontroller to collect the peak-to-peak signal after a delay of one quarter of the signal cycle. Multiple sampling is performed within one cycle, and the sampling accuracy is improved by the averaging method.

[0032] Step 4. The host computer generates a preliminary tomographic image based on the signal response at each angle, that is, the data collected at each angle is reconstructed through the signal acquisition and processing module to generate an image at a single angle.

[0033] Furthermore, in step 2, the driving motor drives the rotating coil array module to rotate the central angle 15° each time, ensuring that the entire target area is covered during the entire measurement process and capturing a more comprehensive electromagnetic response signal.

[0034] Furthermore, in step 3, the low-frequency signal is also directly obtained through a conventional sampling circuit to obtain an electromagnetic signal, and the digital quantity after analog-to-digital conversion by the signal acquisition circuit needs to be transmitted to the host computer through the single-chip microcomputer.

[0035] Furthermore, step 4 also includes: the host computer processes the multi-resolution fusion algorithm of the data fusion module to merge the images generated at different angles and frequencies. The high-frequency and low-frequency images are decomposed into different resolution layers through multi-scale decomposition, and the stronger high conductivity features in the low-frequency image and the more delicate low conductivity features in the high-frequency image are fused according to the response of the high-frequency signal and the low-frequency signal. The images at different resolutions are fused and then reconstructed into a complete image.

[0036] Beneficial effects of the present invention: 1. Through the optimized rotating coil array module, the present invention adopts multi-angle electromagnetic signal acquisition to achieve full coverage of the underground multiphase flow space. Compared with the fixed coil in the prior art, the present invention acquires data from multiple angles through the dynamic rotation of the coil, which significantly improves the spatial resolution. The electromagnetic signals at various angles are comprehensively processed to provide more accurate image reconstruction, thereby significantly improving the accuracy of multiphase flow measurement.

[0037] The rotating coil array captures electromagnetic signals from different angles, and combined with different rotation angle calculations, it can cover the multiphase flow state of the entire space, thus avoiding the blind spot problem caused by the limited angle of the fixed coil. This all-round acquisition method ensures higher image accuracy and resolution.

[0038] 2. The present invention uses an innovative design of mixed frequency excitation to simultaneously use high-frequency and low-frequency signals to respectively excite high-conductivity and low-conductivity materials in multiphase flow. Low-frequency signals have better penetration capabilities for high-conductivity materials (such as salt water, metals, etc.), while high-frequency signals are more sensitive to low-conductivity materials (such as oil and gas, etc.). By combining frequencies and imaging the response characteristics of different materials, the present invention greatly improves the accuracy of identifying complex fluids.

[0039] High conductivity materials and low conductivity materials respond differently in electromagnetic fields, and a single frequency excitation can usually only effectively capture the signal of one type of material. By mixing high-frequency and low-frequency excitation, the present invention can simultaneously identify high-conductivity and low-conductivity materials, overcoming the limitations of single-frequency excitation in multiphase fluid identification in the prior art.

[0040] 3. The image fusion technology of the present invention can generate images with higher precision than single frequency by fusing images generated at high frequency and low frequency. Through multi-resolution fusion technology, high-frequency signals provide more details for low-conductivity materials, and low-frequency signals respond more significantly to high-conductivity materials. The combination of the two can more comprehensively display the overall structure and distribution state of multiphase flow.

[0041] In the image fusion process, the image information generated under different angles and frequency excitations is organically combined by using multi-resolution decomposition and fusion, which effectively improves the image detail retention and contrast. This fusion method ensures that the generated comprehensive image is superior to the traditional single image in terms of resolution and accuracy, providing a solid foundation for the accurate measurement of multiphase flow.

[0042] 4. The present invention adopts a new high-frequency signal acquisition method, so that in the process of high-frequency signal acquisition, the peak-to-peak value of the signal can be accurately acquired through the zero-point detection circuit. This method reduces the dependence on high sampling frequency, so that the system can still effectively obtain key information of high-frequency signals at a lower sampling frequency, ensuring the real-time measurement and data processing efficiency.

[0043] High-frequency signal acquisition often requires an extremely high sampling frequency. The present invention can acquire signals at peak times by combining zero-crossing detection with delayed acquisition, reducing the pressure of large-scale acquisition and processing of high-frequency data while maintaining signal integrity and accuracy. Compared with the high-frequency signal acquisition method in the prior art, the present invention significantly improves efficiency without reducing acquisition quality.

[0044] 5. Due to the use of high-frequency signal acquisition, the present invention can perform efficient signal acquisition under the premise of low power consumption. Compared with traditional high-frequency sampling, the present invention is more energy-efficient and efficient in data processing and signal acquisition, so that it can show better stability and sustainability in a long-term underground operation environment.

[0045] Low power consumption design is crucial for downhole measurement equipment. The present invention greatly reduces the power consumption of the system by reducing the frequency and computational complexity of high-frequency signal acquisition, so that it can work for a long time in a harsh downhole environment without sacrificing the real-time performance and accuracy of signal acquisition. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a module diagram of the present invention; Figure 2 It is a top view of the structure of the present invention; Figure 3 It is a horizontal structure diagram of the present invention; Figure 4 is a cross-sectional view of the present invention; Figure 5 This is a flow chart of mixed frequency excitation and image fusion of the present invention; Figure 6 This is a flow chart of the signal acquisition and processing module of the present invention; Figure 7 It is a flow chart of the measurement process and system operation of the present invention; Figure 8 is the original experimental bubble chart; Fig. 9 Generate annular cross-section images containing bubbles for conventional 8-coil; Fig.10 An image of a cross section of an annulus containing bubbles generated for the present invention; Fig.11 Generate cross-sectional images of the annulus containing bubbles for 16 coils.

[0047] In the figure: 100 - excitation source module, 110 - rotating coil array module, 120 - signal acquisition and processing module, 130 - data fusion module, 140 - image display module, 210 - track structure, 220 - annular support frame, 230 - middle layer gear structure, 240 - angle control sensor. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] The present invention realizes high-precision downhole multiphase flow measurement and measurement imaging through rotating coil array design, mixed frequency excitation, high-frequency signal acquisition and image fusion technology.

[0050] like Figure 1 As shown, a rotary annulus high-precision electromagnetic tomography measuring device of the present invention is composed of an excitation source module 100, a rotary coil array module 110, a signal acquisition and processing module 120, a data fusion module 130 and an image display module 140. The excitation source module 100 is connected to the coil array in the rotary coil array module 110 to realize signal excitation, the rotary array module 110 is connected to the signal acquisition and processing module 120 to realize the acquisition and preliminary processing of feedback signals, the signal acquisition and processing module 120 is connected to the data fusion module 130 to realize the deep processing of signals, and the data fusion module 130 is connected to the image display module 140 to realize the reproduction of images.

[0051] like Figure 2 , Figure 3 , Figure 4 As shown, the rotating coil array module 110 includes a track structure 210, an annular support frame 220, an intermediate gear structure 230, and an angle control sensor 240. The track structure 210 is installed on the inner pipe, the annular support frame 220 is connected to the track, the intermediate gear structure 230 is installed on the annular support frame 220, and the intermediate drive structure includes a drive motor and a gear. The drive motor is installed on the outer wall of the pipe, and the gear is installed on the drive motor shaft. The gear is meshed with the intermediate gear structure 230, thereby driving the annular support frame 220 to rotate around the inner pipe along the track structure 210. The coil array is distributed along the circumference of the inner pipe, and the central angle between two adjacent coils is 30°, and the center of each coil is facing the inner pipe. In order to realize the signal acquisition of the entire annular cross section, the coil array needs to be rotated within a certain angle to obtain multi-angle measurement data, thereby enhancing the spatial resolution of the image and improving the imaging accuracy.

[0052] After experiments and analysis, the rotation angle of the coil is an important factor affecting the image fusion imaging effect. After considering the limited size of the coil and the rotation space, after many experiments, when the angle of each rotation of the coil is too small or too large, the change amplitude of the electromagnetic signal is too small, which will lead to insufficient amount of collected data, and cannot effectively improve the resolution of the image or significantly improve the image quality. Therefore, too small a rotation angle does not bring practical technical improvements. After experimental verification, a rotation angle of 15° can provide the best electromagnetic signal change range under the existing coil size and space limitations, and will not increase too much redundant data. This angle of rotation can not only effectively improve the imaging accuracy after image fusion, but also ensure the stability and efficiency of the system. The entire rotating coil array module consists of 12 coils, which rotate at a fixed angle of 15°. The rotation is achieved by precisely controlling the drive motor (stepping motor) of the rotating mechanism. Whenever the rotation is completed, the rotating coil array module 110 feedbacks the current angle position through its angle control sensor 240 and sends a signal to the single-chip microcomputer for electromagnetic data collection.

[0053] The track structure 210 is a circular track fixedly mounted on the outside of the inner pipe, arranged around the inner pipe, and an annular recessed track is also designed on the inner pipe corresponding to the circular track. Balls are installed in the circular track and the recessed track for the track structure 210 to rotate freely. The track structure 210 is used to provide rotation support for the annular support frame 220. The track structure 210 is made of high-strength, high-temperature resistant materials to adapt to the complex high-temperature and high-pressure environment underground. The smooth surface design of the track structure 210 reduces the friction force when the annular support frame 220 rotates, while ensuring the stable movement of the annular support frame 220.

[0054] The annular support frame 220 is composed of a vertical support column and an annular structure. One end of the vertical support column is connected to the track structure 210, so that the annular support frame 220 can rotate smoothly relative to the track. The other end of the vertical support column is connected to the annular structure, and the installation positions of the vertical support columns are evenly distributed along the circumference to ensure the force balance and rotation stability of the annular support frame 220. There are 12 electromagnetic coil installation points installed on the annular structure, and the center angle of two adjacent coils is 30° to ensure that the coil array can cover the complete cross-section of the inner pipe. The center of the electromagnetic coil faces the inner pipe and is aligned with the target area. The material of the annular support frame 220 is a lightweight and high-strength alloy to reduce the overall weight of the device and ensure rigidity and stability during rotation.

[0055] The middle gear structure 230 is installed in the middle of the vertical support column of the annular support frame 220 . The middle gear structure 230 is an annular structure of a certain thickness with gears, and is located between the annular structure of the annular support frame 220 and the track structure 210 .

[0056] The intermediate drive structure provides a power source to realize the rotation of the rotary coil array module. The intermediate drive mechanism includes a drive motor and a gear. The drive motor meshes with the teeth of the intermediate gear structure 230 through the gear to form a rotation similar to a planetary gear. The teeth of the intermediate gear structure 230 are processed with high precision to ensure the smoothness and efficiency of the meshing. The drive motor adopts a precise stepping motor, and its output angle is set by the control unit (single-chip microcomputer) as required, which can realize precise rotation stepping and rotate at intervals of 15°. The transmission ratio of the gear transmission is optimized to ensure high efficiency and precision.

[0057] Angle control sensor 240, in order to ensure that the annular support frame 220 can accurately stay at the predetermined angle position during the rotation process, it is necessary to equip it with an angle control sensor 240, which is used to monitor the rotation angle in real time and feed back to the control unit. The angle control sensor 240 is installed on the mounting point of the electromagnetic coil of the annular structure to feed back the rotation angle in real time. When rotated to the preset angle of 15°, the angle control sensor 240 will send a signal to the control unit (single-chip microcomputer) to instruct the drive motor (stepper motor) to stop rotating and trigger signal acquisition. The control unit will control the stepper motor to fine-tune the angle according to the feedback information from the angle control sensor 240 to ensure that the position of each stop is accurate. Through the closed-loop control system, the stepper motor can adjust the rotation position according to the real-time angle feedback to ensure that signal acquisition can be performed at a precise angle.

[0058] The driving motor drives the gears to drive the middle gear structure 230 to rotate along the track structure 210. Ensure that the rotation is stable. The angle control sensor 240 and the control unit accurately control the rotation angle to ensure that the coil array stays at the preset angle for signal collection every time it rotates 15°.

[0059] like Figure 5 As shown, the excitation source module 100 uses high-frequency and low-frequency signal excitation, which can capture different response signals of various conductivity materials. The present invention uses a DDS frequency synthesis chip AD9854 to output a sinusoidal excitation signal with a frequency of 100kHz. Its maximum output frequency is 150MHz and the frequency resolution is 48 bits, which can meet the excitation requirements of the rotating coil array module 110. Among them, the 100kHz low-frequency excitation is suitable for high-conductivity materials, such as metals and salt water, and the 10MHz high-frequency excitation is suitable for low-conductivity materials, such as oil and gas. The high-frequency and low-frequency signals generated by the mixed frequency excitation are respectively emitted by the coil array, the signal acquisition and processing module 120 receives the multi-frequency response signal, and the data fusion module 130 generates a preliminary tomographic image.

[0060] The image fusion algorithm used by the data fusion module 130 is used to fuse high-frequency and low-frequency images at different angles to generate a more accurate image. The present invention adopts a multi-resolution fusion algorithm to decompose high-frequency and low-frequency images into different resolution layers through multi-scale decomposition, and then fuses the images at different resolutions and reconstructs them into a complete image. Specifically, the images of different resolutions are fused layer by layer by wavelet transform. For the images obtained by high-frequency and low-frequency excitation, wavelet transform is used to decompose the images into different resolution levels. Each image will generate a series of sub-images, which contain the details and feature information of the original image at different frequencies. The image under high-frequency excitation retains the details of the low-conductivity part in the fluid, and the image under low-frequency excitation is more suitable for the high-conductivity component and provides different feature information. In the sub-images of each layer obtained by multi-resolution decomposition, different fusion strategies are used to select and fuse the feature information of each layer. Through weighted averaging, different weights are given to high-frequency and low-frequency images according to the feature strength of each layer of sub-images, and each layer is weighted averaged. After image fusion, the generated comprehensive image can better present the distribution and characteristics of different materials in multiphase flow, especially for multiple fluid components in complex downhole environments, with better resolution and accuracy.

[0061] High-frequency images may be clearer at higher resolution levels, while low-frequency images have stronger penetration at lower resolution levels. Set different weights according to actual conditions. Through the fusion sub-images of each level, the images of each level are re-synthesized into a complete comprehensive fusion image using inverse wavelet transform. This image contains all the characteristic information under high-frequency and low-frequency excitation, retaining the details while taking into account the overall distribution of high-conductivity and low-conductivity materials.

[0062] like Figure 6As shown, the signal acquisition and processing module 120 can use a filter to remove noise before the signal enters the zero point detection circuit to ensure the accuracy of zero point detection. In order to adapt to possible frequency drift, the period of the acquisition signal is measured in real time on the basis of zero point detection, and the delay is dynamically adjusted to ensure that the sampling is at the accurate peak point. When the acquisition signal passes through the zero point, the zero point detection circuit triggers the delay circuit, and the delay circuit triggers the single-chip microcomputer to collect the peak-to-peak signal after a delay of one quarter of the signal period. Multiple sampling is performed within a cycle, and the sampling accuracy is improved by an averaging method. The present invention is controlled by a zero point detection circuit and a single-chip microcomputer, and can effectively collect the peak-to-peak value of a high-frequency signal at a low sampling frequency, and can obtain key data of a high-frequency signal at a lower sampling frequency.

[0063] like Figure 7 As shown, a working method of a rotating annular high-precision electromagnetic tomography measuring device comprises: Step 1. First, the excitation source module 100 transmits high-frequency 10 MHz and low-frequency 100 KHz electromagnetic signals.

[0064] Step 2. The rotating coil array module 110 can realize the simultaneous operation of 1 excitation coil and 11 detection coils at the same time through a multi-channel switching circuit. High-frequency signals are used to detect low-conductivity materials (such as oil and gas), and low-frequency signals are used to detect high-conductivity materials (such as salt water and metals). The rotating coil array module 110 will transmit signals to the annular multiphase flow area to ensure that multiple media in the measurement area respond simultaneously. After the excitation signal is transmitted, the signal acquisition and processing module begins to collect response signals from different angles.

[0065] Step 3. For the collected high-frequency signal, the signal acquisition and processing module uses a filter to remove noise and ensure the accuracy of zero-point detection. The cycle of the collected signal is measured in real time, and the delay is adjusted dynamically to ensure that the sampling is at the exact peak point. When the high-frequency signal passes through the zero point, the zero-point detection circuit triggers the delay circuit, which triggers the microcontroller to collect the peak-to-peak signal after a delay of one-quarter of the signal cycle. And multiple sampling is performed within one cycle, and the sampling accuracy is improved by the averaging method. Thereby reducing the frequency of data acquisition and ensuring the integrity of the high-frequency signal. At the same time, the acquisition of low-frequency signals does not require zero-point detection, and electromagnetic signals can be directly obtained through conventional sampling circuits. The digital quantity after analog-to-digital conversion of the signal acquisition circuit needs to be transmitted to the host computer through the microcontroller.

[0066] The present invention is based on the USB bus signal transmission mode and adopts USB3300 as an external HS PHY chip to realize high-speed data transmission. When collecting data from the electromagnetic tomography coil array, the host computer first connects to the lower computer measurement device, then reads the data sent by the lower computer and converts it into a voltage value through calculation, and finally stores the detection signal of the electromagnetic tomography coil array.

[0067] Step 4. The host computer generates a preliminary tomographic image according to the signal response at each angle, that is, the data collected at each angle is reconstructed through the signal acquisition and processing module 120 to generate an image at a single angle.

[0068] The subsequent host computer will process the data through the multi-resolution fusion algorithm of the data fusion module 130 to merge the images generated at different angles and frequencies. Through multi-scale decomposition, the high-frequency and low-frequency images are decomposed into different resolution layers, and the stronger high conductivity features in the low-frequency image and the more delicate low conductivity features in the high-frequency image are fused according to the response of the high-frequency signal and the low-frequency signal. The images at different resolutions are fused and then reconstructed into a complete image. The fused image will contain complete information from different frequencies and different angles, ensuring that the final generated image is significantly improved in resolution and accuracy.

[0069] Furthermore, in step 2, in the coil array of the rotating coil array module 110, the center angle between two adjacent coils is 30°, the rotation angle is 15°, and the driving motor drives the rotating coil array module 110 to rotate, ensuring that the entire target area is covered during the entire measurement process and capturing a more comprehensive electromagnetic response signal.

[0070] In order to extract the detection data and multiphase flow parameter signals as accurately and completely as possible, the present invention uses LabVIEW and MATLAB software for joint programming to realize image reconstruction design. The software first completes image reconstruction and preprocessing of the reconstructed image through the MATLAB program, and then displays and outputs it with the help of LabVIEW software. The displayed image can accurately show the distribution and flow state of different media in the downhole multiphase flow, helping users analyze complex multiphase fluid conditions.

[0071] Example The electromagnetic sensor array 1-12 coils in the rotating coil array module 110, the channel switching switch controls one coil as the input coil and the other coils as the output coils. Based on the simulation software, the output signals of 144 groups of coils with bubble sections excited at 10MHz are calculated as shown in Table 1, and then these original output signals are pre-processed and input into the image display module 140 to generate an annular cross-section image containing bubbles, as shown in Table 1. Figure 8-Figure 11 shown.

[0072] Table 1 Output signal of 144 coils with bubble cross section at 10MHz excitation The 144 sets of data in the above table show that the electromagnetic response signal of the bubble cross section shows obvious differences as the combination of the input coil and the output coil changes. This shows that the present invention can sensitively capture the differences in electromagnetic properties between different media (such as bubbles and liquids), proving the detection sensitivity and resolution of the coil array. Under 10 MHz excitation conditions, the table data shows the response characteristics of different coil combinations to high-frequency signals, indicating that the present invention can efficiently capture changes in high-frequency signals.

[0073] The present invention proposes a downhole annulus rotating high-precision electromagnetic tomography measurement device and working method, which overcomes the technical difficulties of insufficient measurement accuracy, image resolution and accuracy in electromagnetic tomography by optimizing the rotating coil array structure, mixed frequency excitation technology, and high-frequency signal acquisition and image fusion processing methods. It realizes high-precision non-contact detection and rapid imaging of gas-liquid two-phase flow and multi-phase flow in the downhole annulus flow channel, significantly improves the ability to identify the composition and distribution of complex fluids in the downhole, and provides a reliable technical means for dynamic monitoring and precise measurement of multi-phase flow.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A rotating annulus high-precision electromagnetic tomography measuring device, characterized in that: It consists of an excitation source module, a rotating coil array module, a signal acquisition and processing module, a data fusion module and an image display module. The excitation source module is connected to the coil array in the rotating coil array module, the rotating array module is connected to the signal acquisition and processing module, the signal acquisition and processing module is connected to the data fusion module, and the data fusion module is connected to the image display module. Among them, the rotating coil array module includes a track structure, an annular support frame and an intermediate gear structure. The track structure is installed on the inner pipe, the annular support frame is connected to the track, the intermediate gear structure is installed on the annular support frame, and the intermediate drive structure includes a drive motor and gears. The drive motor is installed on the outer wall of the pipe, and the gear is installed on the drive motor shaft. The gear is meshed with the intermediate gear structure, thereby driving the annular support frame to rotate around the inner pipe along the track structure.

2. The device according to claim 1, characterized in that The rotating coil array module consists of 12 coils. The coil array in the rotating coil array module is distributed along the circumference of the inner pipe. The center angle between two adjacent coils is 30°. The center of each coil faces the inner pipe. The coil rotates at a center angle of 15° each time it moves.

3. The device according to claim 1, characterized in that The track structure is an annular track fixedly installed on the outside of the inner pipe and arranged around the inner pipe. There is an annular recessed track on the inner pipe corresponding to the track structure, and balls are installed in the track structure and the recessed track.

4. The device according to claim 1, characterized in that The annular support frame consists of a vertical support column and an annular structure. One end of the vertical support column is connected to the track structure, and the other end of the vertical support column is connected to the annular structure. The installation positions of the vertical support columns are evenly distributed along the circumference, and 12 electromagnetic coil installation points are installed on the annular structure.

5. The device according to claim 1, characterized in that The middle layer gear structure is installed in the middle of the vertical support column of the annular support frame, and the middle layer gear structure is an annular structure with a certain thickness and gears.

6. The device according to claim 1, characterized in that The rotating coil array module also includes an angle control sensor mounted on an electromagnetic coil mounting point of the ring-shaped structure of the ring-shaped support frame.

7. A working method of a rotating annulus high-precision electromagnetic tomography measuring device, characterized in that: include: Step 1. First, the excitation source module emits high-frequency 10MHz and low-frequency 100KHz electromagnetic signals; Step 2. The rotating coil array module uses a multi-channel switching circuit to enable one excitation coil and 11 detection coils to work simultaneously at the same time. The rotating coil array module transmits a signal to the annular multiphase flow area. After the excitation signal is transmitted, the signal acquisition and processing module starts to collect response signals from different angles. Step 3. For the collected high-frequency signal, the signal acquisition and processing module uses a filter to remove noise, measures the period of the collected signal in real time, and dynamically adjusts the delay; Among them, when the high-frequency signal passes through the zero point, the zero point detection circuit will trigger the delay circuit. After the delay circuit is delayed according to one quarter of the signal cycle, it triggers the microcontroller to collect the peak-to-peak signal and samples multiple times in one cycle, and improves the sampling accuracy through the averaging method; Step 4. The host computer generates a preliminary tomographic image based on the signal response at each angle, that is, the data collected at each angle is reconstructed through the signal acquisition and processing module to generate an image at a single angle.

8. The method according to claim 7, characterized in that In step 2, the driving motor drives the rotating coil array module to rotate the central angle 15° each time to ensure that the entire target area is covered during the entire measurement process and a more comprehensive electromagnetic response signal is captured.

9. The method according to claim 7, characterized in that: In step 3, the low-frequency signal is also directly obtained through a conventional sampling circuit to obtain an electromagnetic signal, and the digital quantity after analog-to-digital conversion by the signal acquisition circuit needs to be transmitted to the host computer through the single-chip microcomputer.

10. The method according to claim 7, characterized in that Step 4 also includes: the host computer processes the data through the multi-resolution fusion algorithm of the data fusion module: merges the images generated at different angles and frequencies, decomposes the high-frequency and low-frequency images into different resolution layers through multi-scale decomposition, and fuses the stronger high conductivity features in the low-frequency image and the more delicate low conductivity features in the high-frequency image according to the response of the high-frequency signal and the low-frequency signal, fuses the images at different resolutions, and reconstructs them into a complete image.

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