Movable core multi-frequency resistivity electromagnetic tomography system and method

Abstract

The invention discloses a movable core multi-frequency resistivity electromagnetic tomography system and method.The imaging system comprises an upper computer, a digital instrument based on an FPGA, a multi-channel sensor assembly and a measuring platform used for moving a core sample to be measured, and the multi-channel sensor assembly is arranged above the measuring platform; the multi-channel sensor assembly is used for measuring multi-frequency data of a core sample to be measured, the FPGA-based digital instrument is tightly connected with the multi-channel sensor assembly and the upper computer, an imaging subsystem is arranged in the upper computer in advance, and the imaging subsystem comprises a data receiving module, an inversion data imaging module and a parameter setting module. By adopting the system, the electrical and magnetic conductivity distribution condition of an object can be reconstructed according to the sensing voltage of the electromagnetic sensor in a measurement area and an inversion algorithm; and meanwhile, coupling distribution imaging of the electrical conductivity and the magnetic conductivity of the experimental sample under different frequencies can be realized.

Description

Technical Field

[0001] This invention relates to the field of rock measurement technology, and in particular to a portable core multi-frequency resistivity electromagnetic tomography system and method. Background Technology

[0002] In geophysics and rock physics research, rock resistivity is a crucial tool for understanding the electrical properties of rocks. Laboratory measurements often employ two-electrode or four-electrode methods to measure the volume resistivity of rocks, combining this with displacement techniques to obtain resistivity information under different saturation states, thereby constructing reservoir electrical parameters. However, laboratory measurements can lead to significant discrepancies between measured rock resistivity and the actual resistivity of the formation during mining operations due to the reduction of rock moisture during subsequent cold storage. Furthermore, rocks often exhibit strong heterogeneity, making it impossible for existing laboratory measurement methods to provide data on a specific rock profile. Summary of the Invention

[0003] The purpose of this invention is to provide a mobile core multi-frequency resistivity electromagnetic tomography system and method to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides a mobile core multi-frequency resistivity electromagnetic tomography system, comprising a host computer, an FPGA-based digital instrument, a multi-channel sensor assembly, and a measurement platform for moving the core sample to be tested. The multi-channel sensor assembly is disposed above the measurement platform, and the FPGA-based digital instrument is closely connected to the multi-channel sensor assembly and the host computer.

[0005] Preferably, the measuring platform includes a frame, with multiple casters below the frame, a placement platform above the frame, a drive mechanism and a moving mechanism connected to the drive mechanism on the placement platform, and a hopper above the moving mechanism; A tripod is provided on one side of the frame, and a platform is provided on the tripod. The platform abuts against the placement table, and the upper surface of the platform is flush with the upper surface of the placement table. Multiple sets of support mechanisms are provided on the platform.

[0006] Preferably, the multi-channel sensor assembly includes a sensor bracket, which is fixedly mounted on the side of the placement platform that abuts against the table by bolts. A three-axis fine-tuning connecting frame is provided on one side of the sensor bracket, a sensor connecting frame is provided below the three-axis fine-tuning connecting frame, a sensor fixing frame is provided below the sensor connecting frame, and a multi-channel sensor array is provided inside the sensor fixing frame.

[0007] Preferably, the multi-channel sensor array includes a sensor connector, which is circular and has a circular through hole at its center. Multiple sensors arranged in a ring are embedded in the sensor connector.

[0008] Preferably, the moving mechanism includes two sets of slide rails arranged along the length of the placement platform, each set of slide rails is provided with a slider, the two sliders are connected by a connecting frame, a hopper mounting base is provided above the connecting frame, and the other side of the hopper is fixedly connected to the hopper mounting base by bolts.

[0009] Preferably, the driving mechanism includes a servo motor, the driving end of the servo motor is provided with a lead screw, the lead screw is mounted on the placement platform through a lead screw fixing seat, and the lead screw is arranged along the length direction of the placement platform. A lead screw nut is provided on the lead screw, and the lead screw nut is fixedly connected to the connecting frame.

[0010] Preferably, each set of support mechanisms includes a lifting base plate, a lifting rod, a lifting bracket, and support wheels. The support wheels are rotatably connected to the lifting bracket via a rotating shaft. The lifting base plate is positioned above the platform. One side of the lifting rod is connected to the lifting bracket, and the other side of the lifting rod passes through the lifting base plate and the platform, with a limit nut. The lifting rod is fixedly connected to the lifting base plate via a set bolt. Auxiliary rods are symmetrically arranged on both sides of the lifting rod. One side of the auxiliary rod is connected to the lifting bracket, and the other side passes through the lifting base plate and the platform. An auxiliary seat is provided between the lifting base and the auxiliary rod, and the auxiliary seat is fixedly connected to the lifting base plate.

[0011] Preferably, a controller and a host computer placement board are provided on the front side of the frame, and the controller is connected to the drive mechanism.

[0012] Preferably, the host computer is pre-configured with an imaging subsystem, which includes a data receiving module, an inversion data imaging module, and a parameter setting module. The parameter setting module is used to set the frequency, filtering parameters, sensitivity matrix, and pixel grid file; The data receiving module is used to receive core data measured by a multi-channel sensor array acquired by an FPGA-based digital instrument, and to transmit the acquired core data to the inversion data imaging module. The inversion data imaging module is used to receive core data transmitted by the data receiving module, filter and invert the received core data, and construct an image of the coupled distribution of electric and magnetic permeability of the internal structure of the core based on the inversion data.

[0013] This invention also provides a mobile core multi-frequency resistivity electromagnetic tomography method, the steps of which include: S1. Configure the frequency, filtering parameters, sensitivity matrix, and pixel grid file of the imaging system; S2. Place the rock sample to be tested in the hopper. Drive the servo motor through the controller. The servo motor drives the lead screw to rotate. The lead screw drives the lead screw nut to rotate. The lead screw nut drives the slider to move, thereby adjusting the horizontal position of the rock sample and moving it into the circular through hole of the multi-channel sensor array. S3. Continuously collect multi-frequency electromagnetic response data of rock samples. After data filtering and inversion, construct two-dimensional or three-dimensional images of the electrical and magnetic permeability distribution of the internal structure of the rock core based on the inversion data.

[0014] Therefore, the present invention employs the above-described mobile core multi-frequency resistivity electromagnetic tomography system and method, which has the following beneficial effects: (1) The present invention can reconstruct the electric and magnetic permeability coupling distribution of an object based on the sensing voltage of the electromagnetic sensor in the measurement area and the inversion algorithm; at the same time, it can realize the imaging of the electric and magnetic permeability coupling distribution of experimental samples at different frequencies. (2) Compared with laboratory measurement of rock resistivity, the present invention can directly measure the unprocessed rock extracted on site, preventing the rock resistivity measurement value from being significantly different from the actual rock resistivity due to the reduction of rock moisture during subsequent cold storage. The present invention can provide diverse data on rock resistivity and magnetic permeability. (3) The present invention can acquire multi-dimensional data of rocks and can provide data response for a certain cross section of rocks.

[0015] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0016] Figure 1 This is a structural diagram of the measurement platform according to an embodiment of the present invention; Figure 2 This is a structural diagram of the measurement platform according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the multi-channel sensor assembly structure according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the support component structure according to an embodiment of the present invention; Figure 5 This is a flowchart of the imaging method according to an embodiment of the present invention; Figure 6 This is a three-dimensional imaging image of a rock sample according to an embodiment of the present invention; Figure 7 This is a two-dimensional image of an iron rod sample according to an embodiment of the present invention; Figure Labels 1. Multi-channel sensor assembly; 101. Sensor bracket; 102. Three-axis fine-tuning connecting frame; 103. Sensor connecting frame; 104. Sensor mounting bracket one; 105. Sensor mounting bracket two; 106. Sensor connector; 107. Sensor; 2. Frame; 3. Casters; 4. Placement platform; 5. Drive mechanism; 501. Servo motor; 502. Lead screw; 503. Lead screw fixing seat; 504. Lead screw nut; 6. Moving mechanism; 601. 602. Slide rail; 603. Slider; 604. Connecting frame; 605. Hopper mounting base; 7. Hopper; 8. Protective cover; 9. Support mechanism; 901. Lifting base plate; 902. Lifting rod; 903. Lifting bracket; 904. Support wheel; 905. Limit nut; 906. Auxiliary rod; 907. Auxiliary seat; 908. Threaded hole; 10. Platform; 11. Tripod; 12. Upper computer placement plate; 13. Four-button controller; 14. Two-button controller. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. In the description of the present invention, it should be noted that the terms "upper," "lower," "inner," "outer," etc., indicating orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationships commonly used when the product of the invention is in use. They are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0018] Example 1 Reference Figures 1-4 This invention provides a portable core multi-frequency resistivity electromagnetic tomography system, comprising a host computer, an FPGA-based digital instrument, a multi-channel sensor assembly 1, and a measurement platform for moving the core sample to be tested. The multi-channel sensor assembly 1 is mounted above the measurement platform, and the FPGA-based digital instrument is tightly connected to both the multi-channel sensor assembly 1 and the host computer. The host computer is a computer, and the digital instrument is used to transmit and receive electronic signals from the sensors.

[0019] In this embodiment, the measuring platform includes a frame 2, with multiple casters 3 mounted below the frame 2. These casters 3 are movable and equipped with brakes to prevent the measuring platform from moving and affecting the measurement. A placement platform 4 is mounted above the frame 2, and a drive mechanism 5 and a moving mechanism 6 connected to the drive mechanism 5 are mounted on the placement platform 4. A hopper 7 is mounted above the moving mechanism 6, and a protective cover 8 is mounted on the outside of the drive mechanism. A tripod 11 is mounted on one side of the frame 2, and a platform 10 is mounted on the tripod 11. The platform 10 abuts against the placement platform 4, and its upper surface is flush with the upper surface of the placement platform 4. Multiple sets of support mechanisms 9 are mounted on the platform 10 to support the hopper 7 when it moves.

[0020] In this embodiment, the multi-channel sensor assembly 1 includes a sensor bracket 101, which is bolted to the side of the placement platform 4 that abuts against the platform 10. A three-axis fine-tuning connecting frame 102 is provided on one side of the sensor bracket 101 for adjusting the vertical, front-back, and horizontal positions of the multi-channel sensor array. A sensor connecting frame 103 is provided below the three-axis fine-tuning connecting frame 102, and a sensor fixing frame is provided below the sensor connecting frame 103. The multi-channel sensor array is disposed within the sensor fixing frame. The sensor fixing frame includes a first sensor fixing frame 104 and a second sensor fixing frame 105, which are bolted together to fix the multi-channel sensor array within the sensor fixing frame.

[0021] In this embodiment, the multi-channel sensor array includes a sensor connector 106, which is circular and has a circular through hole at its center. Multiple sensors 107 arranged in a ring are embedded in the sensor connector 106.

[0022] In this embodiment, the moving mechanism 6 includes two sets of slide rails 601 arranged along the length of the placement platform 4. Each set of slide rails 601 is provided with a slider 602. The two sliders 602 are connected by a connecting frame 603. A hopper mounting base 604 is provided above the connecting frame 603. One side of the hopper 7 is fixedly connected to the hopper mounting base 604 by bolts.

[0023] In this embodiment, the drive mechanism 5 includes a servo motor 501, and a lead screw 502 is provided at the drive end of the servo motor 501. The lead screw 502 is mounted on the placement platform 4 through a lead screw fixing seat 503, and the lead screw is arranged along the length direction of the placement platform 4. A lead screw nut 504 is provided on the lead screw 502, and the lead screw nut 504 is fixedly connected to the connecting frame 603.

[0024] In this embodiment, each set of support mechanisms 9 includes a lifting base plate 901, a lifting rod 902, a lifting bracket 903, and a support wheel 904. The support wheel 904 is rotatably connected to the lifting bracket 903 via a rotating shaft. The lifting base plate 901 is set above the platform 10. One side of the lifting rod 902 is connected to the lifting bracket 903, and the other side of the lifting rod 902 passes through the lifting base plate 901 and the platform 10 and is provided with a limit nut 905. One side of the lifting base plate 901 is provided with a threaded hole 908. The lifting rod 902 is fixedly connected to the lifting base plate 901 via a set bolt. Auxiliary rods 906 are symmetrically arranged on both sides of the lifting rod 902. One side of the auxiliary rod 906 is connected to the lifting bracket 903, and the other side passes through the lifting base plate 901 and the platform 10. An auxiliary seat 907 is provided between the lifting base and the auxiliary rod 906, and the auxiliary seat 907 is fixedly connected to the lifting base plate 901. When adjusting the support wheel 904, tighten the set bolt to adjust the position of the lifting rod 902, and then adjust the position of the support wheel 904. After adjusting to the appropriate position, tighten the set bolt to fix it in place.

[0025] In this embodiment, a controller and a host computer placement board 12 are provided on the front side of the frame 2. The controller is connected to the drive mechanism 5, specifically controlling the servo motor 501. The controller is a four-button controller 13, including a forward movement start button, a reverse movement start button, an emergency stop button, and a reset button.

[0026] In this embodiment, the front side of the frame 2 also includes a two-button controller 14, which includes a sensor power start button and a system power start button.

[0027] In this embodiment, an imaging subsystem is pre-configured in the host computer. The imaging subsystem includes a data receiving module, an inversion data imaging module, and a parameter setting module. The parameter setting module is used to set the frequency, filtering parameters, sensitivity matrix, and pixel grid file; The data receiving module is used to receive core data measured by a multi-channel sensor array acquired by an FPGA-based digital instrument, and to transmit the acquired core data to the inversion data imaging module. The inversion data imaging module is used to receive core data transmitted by the data receiving module, filter and invert the received core data, and construct an image of the coupled distribution of electrical and magnetic permeability of the internal structure of the core based on the inversion data.

[0028] Example 2 Reference Figure 5 The present invention also provides a mobile core multi-frequency resistivity electromagnetic tomography method, the steps of which include: S1. Configure the frequency, filtering parameters, sensitivity matrix, and pixel grid file of the imaging system; S2. Adjust the position of the support wheel 904 in the sensor array and support mechanism 9, place the rock core sample to be tested in the hopper 7, drive the servo motor 501 through the controller, drive the lead screw to rotate, drive the lead screw 502 to rotate the lead screw nut 504, drive the slider 602 to move, thereby adjusting the horizontal position of the rock sample and moving it into the circular through hole of the multi-channel sensor array. S3. Continuously drive the servo motor 501 to make the hopper 7 move continuously, so that the rock sample passes through the multi-channel sensor array and continuously collects the multi-frequency electromagnetic response data of the rock sample. After data filtering and inversion, a two-dimensional or three-dimensional image of the coupled distribution of electric and magnetic permeability of the rock core is constructed based on the inversion data.

[0029] Example 3 A multi-item experiment was conducted using rock samples and iron rod samples with different degrees of mineralization. The experimental procedure is as follows.

[0030] (1) The rock samples were dried, saturated, and vacuumed to obtain rock samples with different mineralization.

[0031] (2) Set the frequency, filtering parameters, sensitivity matrix, and pixel grid file, and measure the rock sample and iron rod sample respectively. The diameter of the rock is 8.5 cm and the diameter of the iron rod is 1.5 cm. During measurement, place the sample on the hopper 7 and adjust the position of the sample on the hopper 7 by driving the servo motor 501 so that it is in the middle of the multi-channel sensor array. Generally speaking, samples with high conductivity are selected with low frequency signals, and vice versa, samples with low conductivity are selected with high frequency signals. In this experiment, the iron rod is sampled at a frequency of 30 kHz and the rock sample at a frequency of 10 MHz. The electromagnetic response data of the rock core is collected by controlling the signal transmission and reception through the FPGA-based digital instrument. The environment should be kept stable during the data acquisition process to avoid external electromagnetic interference. During the acquisition process, the background data (empty field signal) needs to be stored first. The subsequent relative change percentage of the signal will be calculated based on the real-time signal and the empty field signal, as shown in the following formula: ; In the formula, represents the percentage of relative change in the signal, in %, represents the voltage of the sensor receiving the empty field signal, in V, and represents the measured voltage of the sample placed in the sensor, in V.

[0032] The signal in the empty field generally corresponds to the "noise level". When the sample is placed in the sensor array, the real-time graph of the relative percentage of the signal will show the relative change data caused by the placement of the sample.

[0033] (3) The acquired data is filtered, inverted, and imaged using the inversion data imaging module to obtain the coupled distribution of electrical and magnetic permeability of the core structure. The main process of image construction is as follows: first, the data is loaded, and the real and imaginary parts of the signal are processed. Then, the data is sorted, and frame slices are created in chronological order. The inversion algorithm is used to form a two-dimensional or three-dimensional stack image from the frame slices. In the two-dimensional and three-dimensional imaging images, the color depth represents the electrical conductivity; the darker the color, the greater the electrical conductivity, and vice versa. Figure 6 The image shown is a three-dimensional image of a rock sample. Observation reveals a certain color deviation in one area compared to other areas, but the overall distribution is uniform, which illustrates the anisotropy of the rock. For two-dimensional inversion images, both real and imaginary parts are presented. Generally, at lower signal frequencies, the inversion image is derived from the real part; at higher frequencies, it is derived from the imaginary part. This can be determined based on the magnitudes of the real and imaginary parts obtained during the experiment. For iron rods, the material is relatively homogeneous, such as... Figure 7 According to the two-dimensional real part image, the imaging distribution pattern is basically consistent with it, and the darker color indicates high electrical conductivity. Therefore, the color distribution of the two-dimensional imaging is more uniform than that of the rock.

[0034] Therefore, the present invention employs the above-mentioned mobile core multi-frequency resistivity electromagnetic tomography system and method, which can reconstruct the electrical and magnetic permeability distribution of an object based on the sensing voltage of the electromagnetic sensor in the measurement area and the inversion algorithm; at the same time, it can realize the coupled distribution imaging of electrical and magnetic permeability of experimental samples at different frequencies, which has guiding significance for judging the resistivity of the experimental samples.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A portable core multi-frequency resistivity electromagnetic tomography system, characterized in that: It includes a host computer, an FPGA-based digital instrument, a multi-channel sensor assembly, and a measurement platform for moving the core sample to be tested. The multi-channel sensor assembly is located above the measurement platform, and the FPGA-based digital instrument is closely connected to the multi-channel sensor assembly and the host computer.

2. The mobile core multi-frequency resistivity electromagnetic tomography system according to claim 1, characterized in that: The measuring platform includes a frame, with multiple casters below the frame and a placement platform above the frame. A drive mechanism and a moving mechanism connected to the drive mechanism are mounted on the placement platform, and a hopper is mounted above the moving mechanism. A tripod is provided on one side of the frame, and a platform is provided on the tripod. The platform abuts against the placement table, and the upper surface of the platform is flush with the upper surface of the placement table. Multiple sets of support mechanisms are provided on the platform.

3. The mobile core multi-frequency resistivity electromagnetic tomography system according to claim 2, characterized in that: The multi-channel sensor assembly includes a sensor bracket, which is fixedly mounted on the side of the placement platform that abuts against the table by bolts. A three-axis fine-tuning connecting frame is provided on one side of the sensor bracket, a sensor connecting frame is provided below the three-axis fine-tuning connecting frame, and a sensor fixing frame is provided below the sensor connecting frame. A multi-channel sensor array is provided inside the sensor fixing frame.

4. The mobile core multi-frequency resistivity electromagnetic tomography system according to claim 3, characterized in that: The multi-channel sensor array includes a sensor connector, which is circular and has a circular through hole at its center. Multiple sensors arranged in a ring are embedded in the sensor connector.

5. A mobile core multi-frequency resistivity electromagnetic tomography system according to claim 4, characterized in that: The moving mechanism includes two sets of slide rails arranged along the length of the placement platform. Each set of slide rails is equipped with a slider. The two sliders are connected by a connecting frame. A hopper mounting base is provided above the connecting frame. One side of the hopper is fixedly connected to the hopper mounting base by bolts.

6. A portable core multi-frequency resistivity electromagnetic tomography system according to claim 5, characterized in that: The driving mechanism includes a servo motor, and the driving end of the servo motor is provided with a lead screw. The lead screw is mounted on the placement platform through a lead screw fixing seat, and the lead screw is arranged along the length direction of the placement platform. A lead screw nut is provided on the lead screw, and the lead screw nut is fixedly connected to the connecting frame.

7. A mobile core multi-frequency resistivity electromagnetic tomography system according to claim 2, characterized in that: Each set of support mechanisms includes a lifting base plate, a lifting rod, a lifting bracket, and support wheels. The support wheels are rotatably connected to the lifting bracket via a rotating shaft. The lifting base plate is positioned above the platform. One side of the lifting rod is connected to the lifting bracket, and the other side of the lifting rod passes through the lifting base plate and the platform, with a limit nut. The lifting rod is fixedly connected to the lifting base plate via a set bolt. Auxiliary rods are symmetrically arranged on both sides of the lifting rod. One side of the auxiliary rod is connected to the lifting bracket, and the other side passes through the lifting base plate and the platform. An auxiliary seat is provided between the lifting base and the auxiliary rod, and the auxiliary seat is fixedly connected to the lifting base plate.

8. A portable core multi-frequency resistivity electromagnetic tomography system according to claim 2, characterized in that: The front side of the frame is equipped with a controller and a host computer placement board, and the controller is connected to the drive mechanism.

9. A mobile core multi-frequency resistivity electromagnetic tomography system according to claim 1, characterized in that: The host computer is pre-configured with an imaging subsystem, which includes a data receiving module, an inversion data imaging module, and a parameter setting module. The parameter setting module is used to set the frequency, filtering parameters, sensitivity matrix, and pixel grid file; The data receiving module is used to receive core data measured by a multi-channel sensor array acquired by an FPGA-based digital instrument, and to transmit the acquired core data to the inversion data imaging module. The inversion data imaging module is used to receive core data transmitted by the data receiving module, filter and invert the received core data, and construct an image of the coupled distribution of electric and magnetic permeability of the internal structure of the core based on the inversion data.

10. A portable core multi-frequency resistivity electromagnetic tomography method, using the portable core multi-frequency resistivity electromagnetic tomography system according to any one of claims 1-9, characterized in that the steps... include: S1. Configure the frequency, filtering parameters, sensitivity matrix, and pixel grid file of the imaging system; S2. Place the rock sample to be tested in the hopper. Drive the servo motor through the controller. The servo motor drives the lead screw to rotate. The lead screw drives the lead screw nut to rotate. The lead screw nut drives the slider to move, thereby adjusting the horizontal position of the rock sample and moving it into the circular through hole of the multi-channel sensor array. S3. Continuously collect multi-frequency electromagnetic response data of rock samples. After data filtering and inversion, construct two-dimensional or three-dimensional images of the electrical and magnetic permeability distribution of the internal structure of the rock core based on the inversion data.

Images