Transmitting circuit and excitation method of micro-resistivity scanning imaging logging tool

Abstract

The present invention discloses a transmitting circuit of a micro-resistivity scanning imaging well logging instrument, comprising: an FPGA main control chip, a driving circuit, an H-bridge circuit, an LC filtering circuit, a transmitting transformer and a transmitting loop, wherein the FPGA main control chip, the driving circuit and the H-bridge circuit constitute a class D amplifier, the FPGA chip is connected to the driving circuit, and is used to generate a PWM sinusoidal modulation wave, and output the PWM sinusoidal modulation wave to the driving circuit to convert it into a high-frequency modulation square wave; the high-frequency modulation square wave output by the driving circuit is used to control the switching state of four MOSFETs in the H-bridge circuit, and output a high-frequency modulation square wave after power amplification; the LC filter is connected to the H-bridge circuit, and is used to filter the high-frequency modulation square wave after power amplification to obtain a sinusoidal wave transmitting signal after power amplification; the transmitting transformer is used to isolate and couple the sinusoidal wave transmitting signal after power amplification to the transmitting loop. This scheme can realize the frequency variability of the transmitting signal of the well logging instrument and the precise controllability of the transmitting power, and improve the logging accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum exploration, and in particular to a transmitting circuit of a micro-resistivity scanning imaging well logging instrument, a micro-resistivity scanning imaging well logging instrument and an excitation method thereof. Background Art

[0002] Microresistivity scanning imaging logging is a technology used for formation imaging. It obtains formation information such as formation structure and fracture distribution by measuring tiny resistivity changes on the wall of oil and gas wells. It is widely used in oil exploration and development. In order to reduce or avoid the risk of stuck drill caused by borehole shrinkage or collapse and improve drilling efficiency, drilling mud is increasingly using high-salinity mud. Due to the high conductivity of high-salinity mud, more of the emission current flows back through the mud channel, and less flows into the formation, thus affecting the quality of microresistivity scanning imaging logging data. Therefore, the emission circuit is one of the key factors affecting the quality of microresistivity scanning imaging measurement data.

[0003] For the transmitting circuit, the following problems need to be solved: First, the traditional LC oscillator will have large frequency fluctuations at high temperatures and is not suitable for ultra-high temperature measurement environments; second, the traditional power amplifier circuit has low conversion efficiency and severe self-heating. Summary of the invention

[0004] In order to solve the technical problems existing in the transmitting circuit in a high conductivity environment, this scheme proposes a transmitting circuit of a microresistivity scanning imaging logging instrument, a microresistivity scanning imaging logging instrument and an excitation method thereof, which can provide a higher power transmitting current and a variable transmitting frequency, so as to be suitable for microresistivity scanning imaging in a wellbore with high salinity mud.

[0005] According to a first aspect of the present invention, a transmitting circuit of a microresistivity scanning imaging logging instrument is provided, comprising: an FPGA main control chip, a drive circuit, an H-bridge circuit, an LC filter circuit, a transmitting transformer and a transmitting loop, wherein the FPGA main control chip, the drive circuit and the H-bridge circuit constitute a class D amplifier.

[0006] The FPGA chip is connected to the driving circuit to generate a PWM sinusoidal modulation wave, and the PWM sinusoidal modulation wave is output to the driving circuit to be converted into a high-frequency modulated square wave; the high-frequency modulated square wave output by the driving circuit is used to control the switching state of the four MOSFETs in the H-bridge circuit;

[0007] The LC filter is connected to the H-bridge circuit and is used to filter the high-frequency modulated square wave after power amplification to obtain the sinusoidal wave transmission signal after power amplification; the transmission transformer is used to isolate and couple the sinusoidal wave transmission signal after power amplification to the transmission circuit.

[0008] Optionally, in the transmitting circuit of the microresistivity scanning imaging logging instrument provided by the present invention, the FPGA main control chip is used to control the switching time of the MOSFET in the H-bridge circuit by changing the frequency and pulse width in the PWM sinusoidal modulation wave.

[0009] Optionally, in the transmitting circuit of the microresistivity scanning imaging logging instrument provided by the present invention, the transmitting circuit also includes a power supply monitoring module and a transmitting signal monitoring module. The transmitting signal monitoring module is used to measure the transmitting power in real time, and the power supply monitoring module is used to measure the power supply power of the power supply in real time. By comparing the transmitting power and the power supply power, the transmitting circuit is current limited when the transmitting power and the power supply power are greater than the set maximum power, so as to prevent the transmitting power from exceeding the maximum power supply of the logging instrument and causing system power supply abnormality.

[0010] Optionally, in the transmitting circuit of the microresistivity scanning imaging logging instrument provided by the present invention, the turns ratio of the primary coil to the secondary coil of the transmitting transformer is adjusted according to the transmitting power requirements required by different wellbore formation characteristics.

[0011] According to a second aspect of the present invention, a microresistivity scanning imaging logging instrument is provided, comprising: a power supply nipple, a main circuit nipple, a measuring probe, a transmitting circuit according to the first aspect of the present invention connected between the power supply nipple and the measuring probe, and one or more insulating nipples arranged between the power supply nipple and the main circuit nipple and / or between the upper end of the instrument and the power supply nipple and / or between the measuring probe and the lower end of the instrument.

[0012] Optionally, in the microresistivity scanning imaging logging instrument provided by the present invention, when the upper end of the instrument is only connected to a communication pup joint and no other measuring instruments are connected, an insulating pup joint is not installed between the power pup joint and the communication pup joint at the upper end of the instrument; when the lower end of the instrument is not connected to other logging instruments, an insulating pup joint is not installed at the lower end of the measuring probe; when the mud conductivity exceeds a preset threshold or the wellbore size exceeds a preset size, an insulating pup joint is not installed between the power pup joint and the main circuit pup joint, while the insulating pup joint installed between other logging instruments at the upper end of the instrument and the power pup joint is retained.

[0013] Optionally, in the microresistivity scanning imaging logging instrument provided by the present invention, part of the metal shell of the measuring probe and the metal shell of the main circuit short section are wrapped with fiberglass.

[0014] Optionally, in the microresistivity scanning imaging logging tool provided by the present invention, the microresistivity scanning imaging logging tool further includes rubber stabilizing rings arranged at the upper and lower ends of the measuring probe.

[0015] Optionally, in the microresistivity scanning imaging logging instrument provided by the present invention, the measuring probe includes multiple plates and an internal circuit. When performing microresistivity scanning imaging logging, the transmitting current generated by the transmitting circuit is injected into the formation through the main body of the measuring probe and the plate housing, and then reaches the power supply short section housing through the loop formed by the mud column in the wellbore and the surrounding formation; the internal circuit is used to record the current intensity of each plate button battery and the voltage applied to the plate.

[0016] According to a third aspect of the present invention, there is provided an excitation method for a microresistivity scanning imaging logging tool, which is implemented based on the microresistivity scanning imaging logging tool described in the second aspect of the present invention, and comprises:

[0017] The electrode plate of the measuring probe is placed close to the well wall, and the sinusoidal wave transmission signal generated by the transmitting circuit is injected into the formation through the main body of the measuring probe and the electrode plate shell, and reaches the outer shell of the power supply short section through the loop formed by the mud column in the wellbore and the surrounding formation;

[0018] The current intensity of each button electrode on the plate and the voltage applied to the button electrode are recorded by measuring the internal circuit of the probe, and the change in micro-resistivity around the well wall formation is obtained by calculating the ratio between voltage and current.

[0019] According to the transmitting circuit of the micro-resistivity scanning imaging logging instrument, the micro-resistivity scanning imaging logging instrument and the excitation method thereof provided by the present invention, a class D amplifier is formed by an FPGA main control chip, a driving circuit and an H-bridge circuit, which can achieve lower power consumption and better high temperature performance;

[0020] By adjusting the frequency and duty cycle of the generated PWM sinusoidal modulation wave in real time to adjust the frequency and amplitude of the output current of the transmitting circuit, it can provide a higher power transmitting current and a variable transmitting frequency, which is suitable for micro-resistivity scanning imaging in the borehole with high salinity mud, and is not affected by the temperature drift of inductance and capacitance, thus improving the logging measurement accuracy;

[0021] When conducting microresistivity scanning imaging logging excitation, the position and number of insulating short sections can be flexibly configured according to different logging instrument combinations and wellbore environments downhole, so that the emission current cannot flow back through the instrument's own metal shell, avoiding affecting the emission current loop.

[0022] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0024] Figure 1 A schematic diagram of the structure of a transmitting circuit of a microresistivity scanning imaging well logging tool according to an embodiment of the present invention is shown;

[0025] Figure 2 A schematic structural diagram of a microresistivity scanning imaging logging tool according to an embodiment of the present invention is shown;

[0026] Figure 3 A schematic diagram of a waveform of a PWM sinusoidal modulation signal generated by a PFGA main control chip after power amplification according to an embodiment of the present invention is shown;

[0027] Figure 4 The figure shows a waveform diagram of a transmitting signal output by a transmitting circuit at a temperature of 175° C. according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0029] Figure 1 FIG. 2 shows a schematic diagram of the structure of a transmitting circuit of a microresistivity scanning imaging logging tool according to an embodiment of the present invention. Figure 1 As shown, the transmitting circuit includes an FPGA main control chip, a driving circuit, an H-bridge circuit, an LC filter circuit, a transmitting transformer and a transmitting loop. The FPGA main control chip, the driving circuit and the H-bridge circuit constitute a class D amplifier. The H-bridge circuit includes a bridge arm composed of four MOSFETs.

[0030] Among them, the FPGA main control chip is powered by the power supply after power input conversion (5V is converted to 3.3V, and then converted to 1.5V), and can transmit data with the main control system of the logging instrument through the communication module.

[0031] The FPGA master chip is connected to the drive circuit to generate a PWM sinusoidal modulated wave and output the PWM sinusoidal modulated wave to the drive circuit. The drive circuit can convert and amplify the PWM sinusoidal modulated wave generated by the FPGA master chip into a high-frequency modulated square wave to drive the H-bridge circuit. It has functions such as level conversion, isolation, and protection to ensure that the PWM sinusoidal modulated wave can effectively drive the H-bridge circuit. The H-bridge circuit is the core part of the Class D amplifier. The high-frequency modulated square wave output by the drive circuit is used to control the switching state of the four MOSFETs in the H-bridge circuit to achieve power amplification of the high-frequency modulated square wave.

[0032] The LC filter is connected to the H-bridge circuit and is used to filter the output signal of the H-bridge circuit to remove high-frequency noise in the MOSFET switching process and obtain a smooth sinusoidal wave transmission signal.

[0033] The transmitting transformer is used to isolate and couple the power-amplified sinusoidal transmitting signal to the transmitting circuit, thereby injecting the sinusoidal transmitting signal into the borehole formation. The turns ratio of the primary coil to the secondary coil of the transmitting transformer can be adaptively adjusted according to the transmitting power requirements required by different borehole formation characteristics.

[0034] It can be seen that this solution uses a Class D amplifier to amplify the modulated PWM signal and then restore it to an analog sinusoidal signal output. Since traditional Class A, Class B or Class AB amplifiers amplify input signals through linear amplification, which will cause energy loss and heat generation, Class D amplifiers use the working principle of switching devices. Within the cycle of the input signal, there are only two states, on and off, thereby reducing power loss and heat generation. The frequency of the sinusoidal transmission signal is accurate and stable, and is not affected by the temperature drift of the inductor and capacitor, which is conducive to improving the accuracy of well logging measurements.

[0035] FPGA is a flexible programmable logic device that can realize functions such as digital signal processing, logic control and timing synchronization, and can communicate with the main control system of the logging instrument through RS485 or RS232 communication modules. In one embodiment of the present invention, the FPGA main control chip can be used to control the switching time of the MOSFET in the H-bridge circuit by changing the frequency and pulse width (duty cycle) in the PWM sinusoidal modulation wave, thereby adjusting the frequency and amplitude of the sinusoidal wave transmission signal output by the transmission circuit, which facilitates the real-time configuration of the transmission waveform frequency by the main control chip.

[0036] You can choose ACTEL's A3P series devices based on non-volatile flash technology. This device uses anti-fuse technology and has the characteristics of radiation resistance, high and low temperature resistance, low power consumption, etc. The clock frequency can be multiplied up to 350 MHz, which meets the high-speed computing requirements of the frequency synthesis control circuit.

[0037] like Figure 1As shown, the transmitting circuit also provides a power supply monitoring module and a transmitting signal monitoring module. The transmitting signal monitoring module is used to measure the transmitting power in real time, and the power supply monitoring module is used to measure the power supply power of the power supply in real time. By comparing the transmitting power and the power supply power, the transmitting circuit is current-limited when the transmitting power and the power supply power are greater than the set maximum power, so as to prevent the transmitting power from exceeding the maximum power supply of the logging instrument and causing abnormal power supply to the system.

[0038] The present invention also provides a microresistivity scanning imaging logging instrument, comprising: a power supply nipple, a main circuit nipple, a measuring probe, the transmitting circuit as described above connected between the power supply nipple and the measuring probe, and one or more insulating nipple arranged between the power supply nipple and the main circuit nipple and / or between the upper end of the instrument and the power supply nipple and / or between the measuring probe and the lower end of the instrument.

[0039] That is to say, the configuration position of the insulating short joint can be flexibly adjusted according to different logging instrument combinations and wellbore environments downhole.

[0040] Figure 2 FIG. 2 shows a schematic diagram of the structure of a microresistivity scanning imaging logging tool according to an embodiment of the present invention. Figure 2 As shown, the microresistivity scanning imaging logging tool includes, from top to bottom, an insulating nipple 1, a power nipple, an insulating nipple 2, a main circuit nipple, a rubber straightening ring 1, a measuring probe, a rubber straightening ring 2, an insulating nipple 3, and two ends (TX-L, TX-H) of a transmitting circuit connected between the outer shell of the power nipple and the outer shell of the measuring probe through the internal line of the instrument.

[0041] By using three insulating short sections, the metal shells between the upper end of the instrument and the power short section, the power short section and the main circuit short section, and the measuring probe and the lower end of the instrument are insulated from each other, and the emission current cannot flow back through the metal shell of the instrument itself.

[0042] According to different logging instrument combinations and wellbore environments, Figure 2 The configuration positions of the three insulating short sections can be flexibly adjusted:

[0043] 1) When the upper end of the instrument is only connected to the communication nipple and no other measuring instruments are connected, the insulating nipple (insulating nipple 1) does not need to be installed;

[0044] 2) When the lower end of the instrument is vacant and not connected to other logging instruments, the insulating sub 3 does not need to be installed;

[0045] 3) When the mud conductivity is very high and exceeds the preset threshold, or the borehole size is relatively large and exceeds the preset size, in order to reduce the leakage effect of the mud column on the transmission current loop, the insulating short section 2 can be installed without installing the metal shell of the power short section, and the metal shell of the power short section is wrapped with fiberglass, and the TX-H of the transmission loop needs to be connected to the metal shell of other instruments at the upper end of the instrument through an internal line.

[0046] The metal shell of the measuring probe and the metal shell of the main circuit short section are wrapped with fiberglass to insulate the shell from the borehole mud. The rubber centering rings at the upper and lower ends of the measuring probe are mainly used to keep the instrument centered during the lowering or lifting of the instrument, and to reduce the wear between the electrode shell of the measuring probe and the well wall. Since it is made of high-temperature resistant rubber material, it will not affect the transmitting circuit.

[0047] The measuring probe includes multiple plates and internal circuits. When performing micro-resistivity scanning imaging logging, the transmitting current generated by the transmitting circuit is injected into the formation through the main body of the measuring probe and the plate shell, and then reaches the power supply short-section shell through the loop formed by the mud column in the wellbore and the surrounding formation. The internal circuit is used to record the current intensity of each plate button battery and the voltage applied to the plate, so as to calculate the micro-resistivity changes around the well wall formation.

[0048] Based on the above-mentioned micro-resistivity scanning imaging logging instrument, an embodiment of the present invention further provides an excitation method for the micro-resistivity scanning imaging logging instrument, comprising: placing the electrode plate of the measuring probe close to the well wall, injecting the sinusoidal wave transmission signal generated by the transmitting circuit into the formation through the main body of the measuring probe and the electrode plate housing, and reaching the outer body of the power supply short section through the loop formed by the mud column in the wellbore and the surrounding formation;

[0049] The current intensity of each button electrode on the plate and the voltage applied to the button electrode are recorded by measuring the internal circuit of the probe, and the change in micro-resistivity around the well wall formation is obtained by calculating the ratio between voltage and current.

[0050] Figure 3 FIG. 1 is a schematic diagram showing a waveform of a PWM sinusoidal modulation signal generated by a PFGA main control chip after power amplification according to an embodiment of the present invention. Figure 3 As shown, the microresistivity scanning imaging logging instrument is connected to a power resistor as a formation simulation load, the PFGA main control chip outputs a PWM modulation wave with a base frequency of 128KHz, and the test outputs a digitally synthesized 4KHz sinusoidal excitation signal.

[0051] Figure 4 FIG. 2 shows a schematic diagram of a transmission signal waveform output by a transmission circuit at a temperature of 175° C. according to an embodiment of the present invention. Figure 4As shown, the transmitting circuit outputs a 4KHz sinusoidal power excitation signal, the conversion efficiency of the transmitting power is higher than 85%, and the frequency error of the transmitting signal is less than 1Hz@175℃.

[0052] According to the transmitting circuit of the micro-resistivity scanning imaging logging instrument, the micro-resistivity scanning imaging logging instrument and the excitation method thereof provided by the present invention, a class D amplifier is formed by an FPGA main control chip, a driving circuit and an H-bridge circuit, which can achieve lower power consumption and better high temperature performance;

[0053] By adjusting the frequency and duty cycle of the generated PWM sinusoidal modulation wave in real time to adjust the frequency and amplitude of the output current of the transmitting circuit, it can provide a higher power transmitting current and a variable transmitting frequency, which is suitable for micro-resistivity scanning imaging in the borehole with high salinity mud, and is not affected by the temperature drift of inductance and capacitance, thus improving the logging measurement accuracy;

[0054] When conducting microresistivity scanning imaging logging excitation, the position and number of insulating short sections can be flexibly configured according to different logging instrument combinations and wellbore environments downhole, so that the emission current cannot flow back through the instrument's own metal shell, avoiding affecting the emission current loop.

[0055] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0056] Those skilled in the art will appreciate that the modules or units or components of the devices in the examples disclosed herein may be arranged in the devices described in the embodiment, or alternatively may be located in one or more devices different from the devices in the examples. The modules in the foregoing examples may be combined into one module or may be divided into multiple submodules.

[0057] Those skilled in the art will appreciate that the modules in the devices in the embodiments may be adaptively changed and arranged in one or more devices different from the embodiments. The modules or units or components in the embodiments may be combined into one module or unit or component, and furthermore may be divided into a plurality of submodules or subunits or subcomponents.

[0058] Furthermore, those skilled in the art will appreciate that although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features from different embodiments is meant to be within the scope of the present invention and to form different embodiments.

[0059] As used herein, unless otherwise specified, the use of ordinal numbers "first," "second," "third," etc. to describe common objects merely indicates that different instances of similar objects are involved, and is not intended to imply that the objects so described must have a given order in time, space, order, or in any other manner.

[0060] Although the present invention has been described according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments may be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification is selected primarily for readability and teaching purposes, rather than for explaining or defining the subject matter of the present invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the present invention is illustrative and not restrictive with respect to the scope of the present invention, and the scope of the present invention is defined by the appended claims.

Claims

1. A transmitting circuit of a microresistivity scanning imaging logging tool, characterized in that: It includes: an FPGA main control chip, a drive circuit, an H-bridge circuit, an LC filter circuit, a transmitting transformer, a transmitting loop, a power supply monitoring module, and a transmitting signal monitoring module. The FPGA main control chip, the drive circuit, and the H-bridge circuit constitute a class D amplifier. The turns ratio of the primary coil and the secondary coil of the transmitting transformer is adjusted according to the transmitting power requirements required by different wellbore formation characteristics. The transmitting signal monitoring module is used to measure the transmitting power in real time. The power supply monitoring module is used to measure the power supply power of the power supply in real time. By comparing the transmitting power and the power supply power, when the transmitting power and the power supply power are greater than the set maximum power, the transmitting circuit is protected by current limiting to prevent the transmitting power from exceeding the maximum power supply power of the logging instrument and causing abnormal power supply to the system. The FPGA main control chip is connected to the drive circuit, and is used to generate a PWM sinusoidal modulation wave, and output the PWM sinusoidal modulation wave to the drive circuit to convert it into a high-frequency modulation square wave; the high-frequency modulation square wave output by the drive circuit is used to control the switching state of the four MOSFETs in the H-bridge circuit to obtain a high-frequency modulation square wave after power amplification, and the FPGA main control chip is used to control the switching time of the MOSFET in the H-bridge circuit by changing the frequency and pulse width in the PWM sinusoidal modulation wave; The LC filter circuit is connected to the H-bridge circuit, and is used to filter the high-frequency modulated square wave after power amplification to obtain a sinusoidal wave transmission signal after power amplification, wherein the LC filter circuit is used to filter the output signal of the H-bridge circuit to remove high-frequency noise during the MOSFET switching process; the transmitting transformer is used to isolate and couple the sinusoidal wave transmission signal after power amplification to the transmitting circuit.

2. A microresistivity scanning imaging logging tool, characterized in that: include: A power supply short section, a main circuit short section, a measuring probe, a transmitting circuit as claimed in claim 1 connected between the power supply short section and the measuring probe, and one or more insulating short sections arranged between the power supply short section and the main circuit short section and / or between the upper end of the instrument and the power supply short section and / or between the measuring probe and the lower end of the instrument. When the upper end of the instrument is only connected to the communication short section and no other measuring instruments are connected, no insulating short section is installed between the power supply short section and the communication short section at the upper end of the instrument; when the lower end of the instrument is not connected to other logging instruments, no insulating short section is installed at the lower end of the measuring probe; when the mud conductivity exceeds a preset threshold or the borehole size exceeds a preset size, no insulating short section is installed between the power supply short section and the main circuit short section, while the insulating short section installed between other logging instruments at the upper end of the instrument and the power supply short section is retained. Through the insulating short section, the metal shells between the upper end of the instrument and the power supply short section, the power supply short section and the main circuit short section, and the measuring probe and the lower end of the instrument are insulated from each other, and the transmitting current cannot flow back through the metal shell of the instrument itself, thereby avoiding affecting the transmitting current loop.

3. The microresistivity scanning imaging logging tool according to claim 2, characterized in that: A portion of the metal shell of the measuring probe and the metal shell of the main circuit short section are wrapped with glass fiber reinforced plastic.

4. The microresistivity scanning imaging logging tool according to claim 2, characterized in that: The microresistivity scanning imaging logging tool also includes rubber stabilizing rings arranged at the upper and lower ends of the measuring probe.

5. The microresistivity scanning imaging logging tool according to claim 2, characterized in that: The measuring probe includes multiple plates and an internal circuit. When performing micro-resistivity scanning imaging logging, the transmitting current generated by the transmitting circuit is injected into the formation through the main body of the measuring probe and the plate housing, and then reaches the power short section housing through the loop formed by the mud column in the wellbore and the surrounding formation; the internal circuit is used to record the current intensity of each plate button battery and the voltage applied to the plate.

6. An excitation method for a microresistivity scanning imaging logging tool, characterized in that: The method is implemented based on the microresistivity scanning imaging logging tool as claimed in any one of claims 2 to 5, comprising: The electrode plate of the measuring probe is placed close to the well wall, and the sine wave transmission signal generated by the transmitting circuit is injected into the formation through the main body of the measuring probe and the electrode plate shell, and reaches the outer shell of the power supply short section through the loop formed by the mud column in the wellbore and the surrounding formation; The current intensity of each button electrode on the plate and the voltage applied to the button electrode are recorded by measuring the internal circuit of the probe, and the change in micro-resistivity around the well wall formation is obtained by calculating the ratio between voltage and current.

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