Frequency Adaptive System of Oil-Based Mud Electrical Imaging Logging Tool

Abstract

The present invention belongs to the field of formation exploration imaging technology. After the system is installed on the existing oil-based mud electrical imaging logging instrument, the oil-based mud electrical imaging logging instrument can weigh various factors to determine the optimal measurement signal frequency under different borehole environmental conditions according to field experimental data and adaptive algorithms, thereby obtaining better measurement results. The frequency adaptive system of the oil-based mud electrical imaging logging instrument includes: a control unit, the output end of the control unit is connected to a digital frequency synthesis circuit, the input end of the control unit is connected to a digital-to-analog conversion circuit; the digital frequency synthesis circuit is connected to a signal amplification circuit; the preamplification circuit is sequentially connected to a signal processing unit and a digital-to-analog conversion circuit.

Description

Technical Field

[0001] The invention belongs to the technical field of formation exploration imaging, and in particular relates to a frequency adaptive system of an oil-based mud electric imaging well logging instrument. Background Art

[0002] At present, there are no news reports that domestic oil-based mud electrical imaging technology has been maturely applied on site, and there are no patents or literature on frequency adaptation of oil-based mud electrical imaging.

[0003] When conducting electrical imaging logging of oil-based mud, from the perspective of penetration, the higher the signal frequency, the better. However, as the signal frequency increases, the influence of the formation dielectric constant also increases, which is undesirable. Therefore, in the process of developing the instrument, we can only weigh various influencing factors through a series of experimental data to determine a relatively ideal signal frequency that can meet the needs in most cases. For example, Halliburton's OMRI, Atlas' EARTH IMAGER, Schlumberger's OBMI, and NGI oil-based mud electrical imaging logging tools all select and use fixed signal frequencies. If you want to get better measurement results, you must use the most ideal signal frequency as much as possible. In fact, under different mud resistivity, mud dielectric constant, formation resistivity, and formation dielectric constant borehole environment conditions, this ideal frequency is not fixed. When using non-optimal frequencies for measurement, the measurement accuracy and error will increase, the signal-to-noise ratio will be reduced, and the actual formation information of the well wall will be buried in the noise, which is reflected in the imaging effect as an increase in noise and a decrease in clarity. The measurement effect cannot be guaranteed and cannot meet the needs of geophysical exploration. Summary of the invention

[0004] The present invention provides a frequency adaptive system for an oil-based mud electrical imaging logging instrument. The system can realize the oil-based mud electrical imaging logging instrument under different wellbore environmental conditions to determine the optimal measurement signal frequency according to field experimental data and an adaptive algorithm, thereby improving the measurement accuracy and signal-to-noise ratio, and thus obtaining better measurement results.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] Frequency adaptive system of oil-based mud electrical imaging logging tool, including:

[0007] A control unit, which controls the operation of other circuits in the frequency adaptive system of the oil-based mud electrical imaging logging instrument;

[0008] A digital frequency synthesis circuit receives a control word from the control unit and generates a corresponding frequency signal according to the content of the control word;

[0009] A power amplifier circuit, for amplifying the power of the frequency signal generated by the digital frequency synthesis circuit;

[0010] The preamplifier circuit receives and amplifies the small signal from the formation;

[0011] A signal processing unit further processes the signal from the preamplifier circuit into a signal suitable for digital-to-analog conversion;

[0012] an analog-to-digital conversion circuit, for performing analog-to-digital conversion on the signal from the signal processing unit;

[0013] Furthermore, it also includes:

[0014] A remote control center is installed with algorithms and software for implementing the adaptive strategy.

[0015] Preferably, the control unit is composed of hardware and embedded software for realizing control functions.

[0016] Preferably, the digital frequency synthesis circuit includes a direct digital frequency synthesis circuit and a low-pass filter circuit.

[0017] Preferably, the signal amplification circuit includes a current-voltage signal conversion circuit, an amplitude amplification circuit, a frequency mixing circuit and a power amplifier circuit.

[0018] Preferably, the signal processing unit includes a filtering circuit, a signal amplifying circuit, a phase difference measuring circuit, and an amplitude measuring circuit.

[0019] The present invention provides a frequency adaptive system for an oil-based mud electric imaging logging instrument, wherein the frequency adaptive system includes structural units such as a remote control center, a control unit, a digital frequency synthesis circuit, a signal amplification circuit, a preamplification circuit, a signal processing unit, and a digital-to-analog conversion circuit. The frequency adaptive system for an oil-based mud electric imaging logging instrument having the above structure can realize the oil-based mud electric imaging logging instrument to determine the optimal measurement signal frequency according to field experimental data and an adaptive algorithm under different wellbore environmental conditions, thereby obtaining better measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the structure of a frequency adaptive system for an oil-based mud electrical imaging well logging tool provided by the present invention;

[0021] Figure 2 The present invention provides a structural schematic diagram of a digital frequency synthesis circuit in a frequency adaptive system of an oil-based mud electrical imaging well logging instrument. DETAILED DESCRIPTION

[0022] The present invention provides a frequency adaptive system for an oil-based mud electrical imaging logging instrument. The system can realize the oil-based mud electrical imaging logging instrument under different wellbore environmental conditions to determine the optimal measurement signal frequency according to field experimental data and an adaptive algorithm, thereby improving the measurement accuracy and signal-to-noise ratio, and thus obtaining better measurement results.

[0023] like Figure 1 As shown, the present invention provides a frequency adaptive system for an oil-based mud electric imaging logging instrument, wherein the frequency adaptive system for an oil-based mud electric imaging logging instrument comprises a control unit 1, the output end of the control unit 1 is connected to a digital frequency synthesis circuit 2, the output end of the digital frequency synthesis circuit 2 is connected to a signal amplification circuit 3; and a preamplifier circuit 4, the output end of the preamplifier circuit 4 is connected to a signal processing unit 5, the output end of the signal processing unit 5 is connected to a digital-to-analog conversion circuit 6, and the output end of the digital-to-analog conversion circuit 6 is connected to the input end of the control unit 1. In addition, as a more preferred embodiment of the present invention, the control unit 1 is also connected to a remote control center 7 for communication, and the remote control center 7 is installed with an algorithm and software for implementing an adaptive strategy, which is responsible for the implementation of the adaptive algorithm and adaptive strategy of the entire system.

[0024] In combination with the above structure, the working process of the frequency adaptive system of the oil-based mud electrical imaging logging instrument provided by the present invention is described as follows. Specifically, after the power-on of the system is completed, the control unit first determines the working signal frequency required for the oil-based mud electrical imaging instrument to work under the default conditions, and sends the control word for generating the working signal frequency to the digital frequency synthesis circuit. The digital frequency synthesis circuit receives the instruction control and continuously converts the waveform data into the corresponding frequency analog signal. Preferably, a direct digital frequency synthesis circuit based on field programmable gate array control (English: Field-ProgrammableGate Array; English abbreviation: FPGA) is used; the direct digital frequency synthesis circuit controlled by the field programmable gate array is further composed of structural units such as a phase accumulation unit, a waveform ROM, and a D / A conversion unit, and has the characteristics of high stability and accurate output waveform. It is worth noting that if the digital frequency synthesis circuit does not receive the control word of the control unit, for example: in the initial power-on state, the digital frequency synthesis circuit is initialized according to the specific parameters and timing set by its embedded hardware. Then the digital frequency synthesis circuit sends the dual-frequency or multi-frequency output signal to the digital frequency synthesis circuit, and the structure of the digital frequency synthesis circuit is preferably as follows Figure 2As shown, it is specifically composed of a direct digital frequency synthesis circuit and a low-pass filter circuit, wherein the low-pass filter circuit is connected to the output end of the oscillator, thereby achieving the effect of mixing and filtering out clutter; optionally, the control end of the direct digital frequency synthesis circuit is also connected to the oscillator. Then, the signal amplification circuit (the signal amplification circuit preferably includes a current-voltage signal conversion circuit, an amplitude amplification circuit, a frequency mixing circuit and a power amplifier circuit) amplifies the working signal generated after the frequency mixing and filtering, and penetrates the plate of the oil-based mud electrical imaging logging instrument into the oil-based mud in the wellbore to complete the measurement work.

[0025] On the other hand, the three parts of the preamplifier circuit, the signal processing unit and the digital-to-analog conversion circuit form a receiving and processing unit for the return signal. The preamplifier circuit is responsible for collecting the tiny return signal received by the receiving electrode of the plate of the oil-based mud electrical imaging instrument and transmitting it to the signal processing unit. The signal processing unit further processes the received information. Its structure preferably specifically includes a filter circuit, a signal amplifier circuit, a phase difference measurement circuit, and an amplitude measurement circuit. Then the digital-to-analog conversion circuit completes the analog-to-digital conversion of each return signal and uploads it to the control unit in a centralized manner. At this point, the collection process of the return signal is completed. The control unit can continue to adjust the digital frequency synthesis circuit to generate a new working signal frequency and working mode according to the control strategy pre-set into the embedded hardware / software, and repeatedly test the return signal again until a large amount of sweep frequency data is obtained, and the test working signal frequency most suitable for the target is determined in combination with the test algorithm and the experience of the staff, and then the oil-based mud electrical imaging logging instrument enters the logging state with the test working signal frequency most suitable for the target, starts the logging work, and finally obtains a better measurement effect.

[0026] The present invention provides a frequency adaptive system for an oil-based mud electric imaging logging instrument, wherein the frequency adaptive system includes structural units such as a remote control center, a control unit, a digital frequency synthesis circuit, a signal amplification circuit, a preamplification circuit, a signal processing unit, and a digital-to-analog conversion circuit. The frequency adaptive system for an oil-based mud electric imaging logging instrument having the above structure can realize the oil-based mud electric imaging logging instrument to determine the optimal measurement signal frequency according to field experimental data and an adaptive algorithm under different wellbore environmental conditions, thereby obtaining better measurement results.

[0027] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. Frequency adaptive system of oil-based mud electrical imaging logging instrument, characterized in that: include: A control unit, which controls the operation of other circuits in the frequency adaptive system of the oil-based mud electrical imaging logging tool; A digital frequency synthesis circuit receives a control word from the control unit and generates a corresponding frequency signal according to the content of the control word; The signal amplification circuit performs power amplification on the frequency signal generated by the digital frequency synthesis circuit to generate an amplified working signal, and the amplified working signal penetrates the plate of the oil-based mud electrical imaging logging instrument into the oil-based mud in the wellbore to complete the measurement work; The preamplifier circuit receives and amplifies the tiny return signal from the formation received by the plate of the oil-based mud electrical imaging logging instrument; A signal processing unit further processes the signal from the preamplifier circuit into a signal suitable for digital-to-analog conversion; The analog-to-digital conversion circuit performs analog-to-digital conversion on the return signal from the signal processing unit and uploads it to the control unit, wherein: The control unit first determines the working signal frequency required for the oil-based mud electrical imaging instrument to work under default conditions, and sends the control word for generating the working signal frequency to the digital frequency synthesis circuit, so that the digital frequency synthesis circuit receives the current instruction control and continuously converts the waveform data into the corresponding frequency analog signal, and, The control unit also continues to adjust the digital frequency synthesis circuit to generate a new working signal frequency and working mode according to the collected feedback signal and the adaptive control strategy pre-set in the embedded hardware / software, and repeatedly tests the feedback signal until a large amount of sweep frequency data is obtained, thereby determining the most suitable test working signal frequency for the target site, so that the oil-based mud electrical imaging logging instrument enters the logging state with the most suitable test working signal frequency for the target site, starts the logging work, and finally obtains a better measurement effect.

2. The frequency adaptive system of oil-based mud electrical imaging logging instrument according to claim 1, characterized in that: Also includes: A remote control center is installed with algorithms and software for implementing the adaptive strategy.

3. The frequency adaptive system of oil-based mud electrical imaging logging instrument according to claim 1, characterized in that: The control unit is composed of hardware and embedded software for realizing control functions.

4. The frequency adaptive system of oil-based mud electrical imaging logging instrument according to claim 1, characterized in that: The digital frequency synthesis circuit comprises a direct digital frequency synthesis circuit and a low-pass filter circuit.

5. The frequency adaptive system of oil-based mud electrical imaging logging instrument according to claim 1, characterized in that: The signal amplifying circuit comprises a current-voltage signal conversion circuit, an amplitude amplifying circuit, a frequency mixing circuit and a power amplifier circuit.

6. The frequency adaptive system of oil-based mud electrical imaging logging instrument according to claim 1, characterized in that: The signal processing unit includes a filtering circuit, a signal amplifying circuit, a phase difference measuring circuit, and an amplitude measuring circuit.

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