Electric imaging measurement and acquisition method

Abstract

The invention relates to an electric imaging measurement and acquisition method, which comprises the following steps of: respectively connecting a matched resistor in series between each button electrode of a well logging device and a corresponding polar plate, so as to reduce the total resistance after the matched resistors and an equivalent slurry resistor are connected in parallel through the matched resistors; and logging by using the logging device, and collecting current flowing back to the upper electrode in the logging process so as to obtain a stratum image according to the current. Through the arrangement of the matched resistor, the total resistance after the matched resistor and the equivalent slurry resistor are connected in parallel is reduced, and the current-voltage conversion module of the operational amplifier part can work in an ideal high signal-to-noise ratio region under the condition of different slurry resistivity and formation resistivity; an operational amplifier of a subsequent circuit works in a relatively ideal interval; the thickness of a flushing zone between each button electrode and the stratum is reduced; the effective proportion of the measured target current passing through the stratum is improved, so that the signal-to-noise ratio of weak signals is improved, and the imaging quality is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of electrical imaging well logging, and in particular relates to an electrical imaging measurement and acquisition method. Background Art

[0002] Electrical imaging logging is an important logging technology that primarily involves performing array scanning measurements of the surrounding formations in openhole wells to generate images of the wellbore's strata's electrical conductivity. These images can intuitively display information such as bedding, fractures, holes, and faults within the wellbore's strata. Software processing also enables detailed evaluation of sandstone, shale, carbonate, igneous, and other complex lithologic formations.

[0003] With the advancement of oilfield exploration and development, logging operations are becoming increasingly deep, and high-resistance formations are becoming increasingly common. Current electrical imaging methods suffer from reduced signal-to-noise ratios and unclear imaging when measuring high-resistance formations (e.g., formations with resistivity above 1000Ω.m), saline water slurries, or formations with a ratio of formation resistivity (Rt) to mud resistivity (Rm) (Rt / Rm) greater than 10000. Furthermore, the useful signals in these formations are relatively weak, and logging equipment is unable to adequately collect these signals. Therefore, current electrical imaging logging methods cannot meet the logging needs of these formations. Summary of the Invention

[0004] In order to solve all or part of the above problems, the present invention aims to provide an electrical imaging measurement and acquisition method. The present invention reduces the total resistance of the matching resistor and the equivalent mud resistance in parallel by setting a matching resistor, so that the operational amplifier of the subsequent circuit operates in a relatively ideal range; reduces the thickness of the flushing zone between each button electrode and the formation; thereby improving the signal-to-noise ratio of weak signals during the logging process and improving the imaging effect.

[0005] According to one aspect of the present invention, there is provided an electrical imaging measurement acquisition method, comprising:

[0006] Connecting matching resistors in series between each button electrode and the corresponding electrode plate of the logging device, so as to reduce the total resistance of the matching resistors and the equivalent mud resistance in parallel by the matching resistors;

[0007] Increasing the plate force of each plate against the well wall during logging to reduce the thickness of the flushing zone between each button electrode and the formation;

[0008] The well logging device is used to log a well, and the current flowing back to the upper electrode during the logging process is collected to obtain a formation image based on the current.

[0009] Furthermore, the pad force of each pad against the well wall during the logging process is increased as follows:

[0010] During the logging process, the plate force of each plate against the well wall is increased to more than 200N.

[0011] Furthermore, before logging with the logging device and collecting the current flowing back to the upper electrode during the logging process, the method further includes: increasing the voltage applied to each of the button electrodes.

[0012] Furthermore, the voltage applied to each of the button electrodes is increased as follows:

[0013] The voltage applied to each of the button electrodes is increased to more than four times the voltage corresponding to the low-resistance formation.

[0014] Furthermore, the logging device is used to log a well, and the current flowing back to the upper electrode during the logging process is collected to obtain a formation image based on the current further includes:

[0015] Logging a well using the logging device, and collecting the current flowing back to the upper electrode during the logging process;

[0016] Convert each collected current signal into a voltage signal respectively;

[0017] Convert each voltage signal into a digital signal; and

[0018] Each channel of the digital signal is sent to a post-processing module, so that the post-processing module can obtain a formation image according to each channel of the digital signal.

[0019] Furthermore, before converting each of the voltage signals into digital signals, the method further includes:

[0020] performing bandpass filtering and amplification processing on each of the converted voltage signals to obtain a corresponding first-level voltage signal, and performing amplification processing on each of the first-level voltage signals to obtain a corresponding second-level voltage signal;

[0021] Converting each of the voltage signals into digital signals specifically includes converting each of the second-level voltage signals into digital signals.

[0022] Furthermore, converting each of the voltage signals into digital signals is specifically: using a multi-channel analog-to-digital conversion chip to simultaneously convert multiple voltage signals into corresponding digital signals, wherein the number of channels of the analog-to-digital conversion chip is greater than or equal to the number of the multiple voltage signals that it converts simultaneously.

[0023] Furthermore, each of the digital signals is sent to a post-processing module separately so that the post-processing module obtains a formation image based on each of the digital signals. Specifically, through feedback control, the phase of the digital signal sent at the analog-to-digital conversion chip is made the same as the phase of the preset transmission signal, or the phase of the digital signal sent at the analog-to-digital conversion chip and the phase of the preset transmission signal have the same phase difference.

[0024] Furthermore, the use of a multi-channel analog-to-digital conversion chip to simultaneously convert multiple voltage signals into corresponding digital signals specifically includes: using an eight-channel or greater analog-to-digital conversion chip to simultaneously convert eight voltage signals into corresponding digital signals.

[0025] From the above technical solution, it can be seen that the present invention provides an electrical imaging measurement and acquisition method, which has the following characteristics:

[0026] Beneficial effects:

[0027] The present invention reduces the total resistance of the matching resistor and the equivalent mud resistance in parallel by setting a matching resistor, so that the operational amplifier of the subsequent circuit operates in a relatively ideal range; reduces the thickness of the flushing zone between each button electrode and the formation; thereby improving the signal-to-noise ratio of weak signals during the logging process, which is conducive to improving the imaging effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the electrical imaging logging process;

[0029] Figure 2 Schematic diagram of the current flowing back to the electrode plate through the flushing zone between the formation and the electrode plate;

[0030] Figure 3 Schematic diagram of current flowing back to the upper electrode through the flushing zone and formation;

[0031] Figure 4 This is a flow chart of the electrical imaging measurement and acquisition method according to an embodiment of the present invention;

[0032] Figure 5 This is the equivalent circuit diagram during the logging process;

[0033] Figure 6 The block diagram of the conditioning circuit for conditioning the target current during the logging process. DETAILED DESCRIPTION

[0034] In order to better understand the purpose, structure and function of the present invention, the following further describes in detail an electrical imaging measurement and acquisition method of the present invention in conjunction with the accompanying drawings.

[0035] The schematic diagram of the electrical imaging logging process is as follows: Figure 1As shown in the figure, during the logging process, there is a flushing zone 1 (i.e., the gap between the button electrode and the formation 2) between the button electrode and the formation 2. The resistivity of the flushing zone 1 is approximately equal to the mud resistivity. In the case of high-resistance formations, the mud resistivity is lower than the formation resistivity. During the logging process, most of the electrode current flows back to the electrode plate through the flushing zone 1 between the formation 2 and the electrode plate. Figure 2 The current indicated by the arrow in the figure is relatively weak. Figure 3 The arrow in the middle indicates the current. The current flowing back through the formation and flushing zone 1 to the upper electrode is relatively weak. Therefore, the current flowing back through the formation detected by the logging device may be weak, or even completely undetectable. When the current being detected is weak and the signal-to-noise ratio of the current signal is low, unclear imaging may occur.

[0036] To this end, an embodiment of the present invention provides an electrical imaging measurement and acquisition method, such as Figure 4 Shown, including:

[0037] Step S01: connecting a matching resistor in series between each button electrode and the corresponding electrode plate of the logging device, so as to reduce the total resistance of the matching resistor and the equivalent mud resistance in parallel through the matching resistor;

[0038] Step S02: increasing the plate force of each plate against the well wall during the logging process to reduce the thickness of the flushing zone between each button electrode and the formation;

[0039] Step S03: logging the well using a logging device, collecting the current flowing back to the upper electrode during the logging process, and obtaining a formation image based on the current.

[0040] Specifically, the equivalent circuit in the logging process is as follows: Figure 5 As shown, Rmud represents the equivalent mud resistance. In the present application, a matching resistor R1 is connected between the button electrode 4 and the corresponding electrode plate 3, so that when the equivalent mud resistance Rmud is relatively high, the total resistance of the equivalent mud resistance Rmud and the matching resistor R1 in parallel is relatively low; when the equivalent mud resistance Rmud is not too high, the total resistance of the equivalent mud resistance Rmud and the matching resistor R1 in parallel is correspondingly reduced, thereby making the current flowing through the operational amplifier of the subsequent circuit relatively stable.

[0041] Again, reference Figure 5 , the total current I during the logging process is equal to the current I mud (corresponding to Figure 2 The current in the middle path) and the sum of the current I1 and the target current I2 (corresponding to Figure 3Since different muds have different mud resistivities, that is, different muds have different equivalent mud resistance Rmud values, the configuration of this embodiment ensures that both resistor R2 and the operational amplifier can operate in a relatively ideal high signal-to-noise ratio region for formations with different mud resistivities. This increases the effective proportion of the measured target current I2 passing through the formation, thereby improving the signal-to-noise ratio of weak signals and enhancing imaging quality.

[0042] Recombination Figure 1 Since the detection depth of the logging device is limited (the detection depth of the logging device is about 4 inches), the plate force of different plates against the well wall affects the thickness of the flushing zone 1 in the effective detection depth (which can be understood as noise information). The greater the plate force, the smaller the thickness of the flushing zone 1 in the effective detection depth. When the detection depth of the logging device is constant, the thickness of the formation 2 is thicker (which can be understood as effective information). Again, the greater the thickness of the flushing zone 1, the smaller the equivalent mud resistance, corresponding to Figure 2 and Figure 3 The currents in the two paths, Figure 2 The more current the path, Figure 3 The less the current passing through the formation in the middle path, the smaller the target current I2 will be.

[0043] Therefore, in this embodiment, the plate force of each plate against the well wall during logging is increased, thereby reducing the thickness of the flushing zone, alleviating the impact of the mud cake on the flushing zone during sliding logging of the logging device, and reducing the situation where most of the electric button emission current flows back through the mud cake due to the focusing effect. Most of the electric button emission current flows back through the mud cake, which will result in less effective formation information being measured, resulting in blurred images. In other words, the setting of this embodiment reduces Figure 2 The current corresponding to the path.

[0044] Step S02 of increasing the plate force of each plate against the well wall during the logging process specifically includes increasing the plate force of each plate against the well wall to more than 200N during the logging process.

[0045] In a specific embodiment, before performing well logging using a logging device in step S03 and collecting the current flowing back to the upper electrode during the logging process, the electrical imaging measurement collection method further includes: increasing the voltage applied to each button electrode.

[0046] Specifically, in cement slurry logging systems, the equivalent mud column resistance is low. Increasing the voltage applied to each button electrode increases the effective voltage applied to the loading formation. For different high-resistance formations, increasing the effective voltage applied to the loading formation effectively increases the measurable resistivity range while maintaining the same weak signal detection capability. For formations with the same resistivity, increasing the effective voltage applied to the loading formation is equivalent to increasing the target current, thereby amplifying the original weak signal.

[0047] In a specific implementation, increasing the voltage applied to each button electrode specifically includes increasing the voltage applied to each button electrode to more than 4 times the voltage corresponding to the low-resistance formation.

[0048] In a specific embodiment, step S03 of logging with a logging device and collecting the current flowing back to the upper electrode during the logging process to obtain a formation image based on the current further includes:

[0049] Use the logging device to log the well and collect the current flowing back to the upper electrode during the logging process;

[0050] Convert each collected current signal into a voltage signal respectively;

[0051] Convert each voltage signal into a digital signal; and

[0052] Each channel of digital signal is sent to a post-processing module respectively, so that the post-processing module can obtain a formation image according to each channel of digital signal.

[0053] Specifically, Figure 6 This is a block diagram of the conditioning circuit that conditions the target current during the logging process. During the logging process, each target current I2 is first converted into a voltage signal by the current-voltage conversion circuit. The voltage signal is then converted into a digital signal and sent to the post-processing module through the communication interface, thereby facilitating the post-processing module to obtain a formation image based on each digital signal.

[0054] The current-to-voltage conversion circuit includes an operational amplifier, a resistor R2, and a capacitor C2. The target current I2 is input to the inverting input of the operational amplifier, the non-inverting input of the operational amplifier is grounded, and the resistor R2 is connected in parallel between the inverting input and the output of the operational amplifier. The capacitor C2 is also connected in parallel between the inverting input and the output of the operational amplifier. The voltage signal is output through the output of the operational amplifier. In specific implementations, an operational amplifier with low voltage noise density and high gain-bandwidth product should be selected.

[0055] Before converting each voltage signal into a digital signal, the method further includes:

[0056] Performing bandpass filtering and amplification processing on each converted voltage signal to obtain a corresponding first-level voltage signal, and performing amplification processing on each first-level voltage signal to obtain a corresponding second-level voltage signal;

[0057] Converting each voltage signal into a digital signal specifically includes: converting each second-level voltage signal into a digital signal.

[0058] Specifically, after the target current is converted into a voltage signal by the current-voltage conversion circuit, the voltage signal needs to be filtered to obtain a high-gain second-level voltage signal after filtering out the noise signal, and then the high-gain second-level voltage signal is converted into a corresponding digital signal.

[0059] In this embodiment, the signal is amplified twice. During the amplification process, the basic noise in the amplification and conditioning process is reduced by selecting a high-precision, low-noise operational amplifier and a reasonable PCB board layout.

[0060] Among them, the filtering processing includes bandpass filtering and amplification processing. Each voltage signal is subjected to bandpass filtering and amplification processing respectively to obtain a first-level voltage signal after filtering out the noise signal of a specific frequency; the first-level voltage signal is subjected to amplification processing respectively to obtain a high-gain second-level voltage signal.

[0061] Among them, converting each voltage signal into a digital signal specifically includes: using a multi-channel analog-to-digital conversion chip to simultaneously convert multiple voltage signals into corresponding digital signals, wherein the number of channels of the analog-to-digital conversion chip is greater than or equal to the number of multiple voltage signals it converts simultaneously.

[0062] In this embodiment, a multi-channel analog-to-digital conversion chip is used to convert each voltage signal into a digital signal, thereby enabling parallel processing of high-gain second-stage voltage signals. In the prior art, multiple voltage signals must be converted into analog signals one by one through the switching of analog switches. The use of a multi-channel analog-to-digital conversion chip in this embodiment reduces signal switching noise and improves the signal-to-noise ratio.

[0063] Again, the analog-to-digital conversion chip of this embodiment is a high-precision analog-to-digital conversion chip, which can reduce quantization errors and effectively improve the weak signal resolution capability.

[0064] During implementation, a multi-channel analog-to-digital conversion chip is used to simultaneously convert multiple voltage signals into corresponding digital signals. Specifically, an eight-channel or greater analog-to-digital conversion chip is used to simultaneously convert eight voltage signals into corresponding digital signals.

[0065] Among them, each digital signal is sent to the post-processing module separately, so that the post-processing module obtains the formation image according to each digital signal. Specifically, through feedback control, the phase of the digital signal sent at the analog-to-digital conversion chip is made the same as the phase of the preset transmission signal, or the phase of the digital signal sent at the analog-to-digital conversion chip and the phase of the preset transmission signal have the same phase difference.

[0066] Specifically, such as Figure 6 As shown, the transmission signal is sent to the SOC processor after shaping processing, so that the SOC processor controls the analog-to-digital conversion chip according to the phase feedback of the transmission signal, so that the phase of the digital signal sent by the analog-to-digital conversion chip is the same as the phase of the preset transmission signal, thereby avoiding low-frequency noise caused by the frequency difference or phase difference between the transmission and acquisition.

[0067] The signal measured by the analog-to-digital conversion chip completes digital phase-sensitive detection and Fourier operations in the SOC processor, improves the high-precision acquisition of signal processing, completes the normalization scale coefficient correction of each electric buckle channel, completes signal correlation operations, and improves the consistency of the monitoring current of each electric buckle.

[0068] The measurement and acquisition method of this embodiment greatly improves the detection capability of weak signals. The detection capability of weak target current signals reaches nA level, and the dynamic range reaches 120dB. It significantly enhances the measurement capability in high-resistance formations, and can also obtain relatively clear images in high-resistance formations.

[0069] It should be noted that, unless otherwise specified, the technical or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0070] In addition, the terms "one", "two", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. In the description of the present invention, the meaning of "multiple" is more than two, unless otherwise clearly and specifically limited.

[0071] In this application, unless otherwise expressly specified or limited, terms such as "mounted," "connected," "connect," and "fixed" should be understood in a broad sense. For example, they may refer to fixed or detachable connections, or integration; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0072] 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 them. 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 or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. An electrical imaging measurement and acquisition method, characterized in that: include Connecting matching resistors in series between each button electrode and the corresponding electrode plate of the logging device, so as to reduce the total resistance of the matching resistors and the equivalent mud resistance in parallel by the matching resistors; Increasing the plate force of each plate against the well wall during logging to reduce the thickness of the flushing zone between each button electrode and the formation; The well logging device is used to log a well, and the current flowing back to the upper electrode during the logging process is collected to obtain a formation image based on the current.

2. The electrical imaging measurement and acquisition method according to claim 1, characterized in that: The pad force of each pad against the well wall during the logging process is specifically: During the logging process, the plate force of each plate against the well wall is increased to more than 200N.

3. The electrical imaging measurement and acquisition method according to claim 1, characterized in that: Before logging with the logging device and collecting the current flowing back to the upper electrode during the logging process, the method further includes: increasing the voltage applied to each of the button electrodes.

4. The electrical imaging measurement and acquisition method according to claim 3, characterized in that: The voltage applied to each of the button electrodes is increased as follows: The voltage applied to each of the button electrodes is increased to more than four times the voltage corresponding to the low-resistance formation.

5. The electrical imaging measurement and acquisition method according to claim 1, characterized in that: The method of logging with the logging device and collecting the current flowing back to the upper electrode during the logging process to obtain a formation image based on the current further includes: Logging a well using the logging device, and collecting the current flowing back to the upper electrode during the logging process; Convert each collected current signal into a voltage signal respectively; Convert each voltage signal into a digital signal; and Each channel of the digital signal is sent to a post-processing module, so that the post-processing module can obtain a formation image according to each channel of the digital signal.

6. The electrical imaging measurement and acquisition method according to claim 5, characterized in that: Before converting each of the voltage signals into digital signals, the method further includes: Each of the converted voltage signals is subjected to bandpass filtering and amplification processing to obtain a corresponding first-level voltage signal, and each of the first-level voltage signals is subjected to amplification processing to obtain a corresponding second-level voltage signal.

7. The electrical imaging measurement and acquisition method according to claim 6, characterized in that: Converting each of the voltage signals into digital signals specifically includes converting each of the second-level voltage signals into digital signals.

8. The electrical imaging measurement and acquisition method according to claim 5, characterized in that: The converting of each voltage signal into a digital signal is specifically as follows: using a multi-channel analog-to-digital conversion chip to simultaneously convert multiple voltage signals into corresponding digital signals, wherein the number of channels of the analog-to-digital conversion chip is greater than or equal to the number of the multiple voltage signals that it converts simultaneously.

9. The electrical imaging measurement and acquisition method according to claim 8, characterized in that: The method of sending each of the digital signals to the post-processing module separately so that the post-processing module can obtain the formation image according to each of the digital signals is specifically as follows: through feedback control, the phase of the digital signal sent at the analog-to-digital conversion chip is made the same as the phase of the preset transmission signal, or the phase of the digital signal sent at the analog-to-digital conversion chip and the phase of the preset transmission signal have the same phase difference.

10. The electrical imaging measurement and acquisition method according to claim 8, characterized in that: The use of a multi-channel analog-to-digital conversion chip to simultaneously convert multiple voltage signals into corresponding digital signals specifically includes: using an eight-channel or greater analog-to-digital conversion chip to simultaneously convert eight voltage signals into corresponding digital signals.

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