A system and method for receiving downhole wireless signals

Abstract

This invention discloses a downhole wireless signal receiving system and method, relating to the field of downhole signal transmission technology. The receiving system includes a detection module and a decoding module. The detection module detects the current resonant frequency of the receiving coil at preset time intervals or after each preset drilling distance. The decoding module enables the receiving coil to receive the analog signal transmitted by the transmitting coil according to the current resonant frequency, and decodes the received analog signal according to the current resonant frequency. The receiving system of this invention adapts the frequency of the received signal to the frequency of the transmitting coil and adaptively decodes according to changes in the current resonant frequency of the receiving coil, resulting in high decoding accuracy.

Description

Technical Field

[0001] This invention relates to the field of downhole signal transmission technology, and in particular to a downhole wireless signal receiving system and receiving method. Background Technology

[0002] Currently, under the circumstances of increasing exploration difficulty and reducing development costs, measurement while drilling technology has been widely used in the exploration and development of horizontal wells, highly deviated wells and complex formation environments. Conventional measurement while drilling instruments have a distance between the sensor measurement point and the bottom of the well. At the formation boundary, the construction efficiency will decrease due to the untimely transmission of measurement values.

[0003] Acquiring near-bit sensor data primarily relies on wireless short-pass transmission, currently employing three main technologies: acoustic transmission, mud pulse transmission, and electromagnetic wave transmission. Compared to the other two methods, electromagnetic wave transmission offers faster speeds and a larger carrier information capacity, making it the more commonly used method in practical applications. Electromagnetic wave wireless short-pass transmission transmits signals via magnetic field coupling, typically using coils as downhole transceivers. Existing wireless short-pass carrier frequencies are usually fixed values. During signal transmission, changes in resistivity at different formations during drilling lead to significant signal attenuation, and the operation of drilling equipment also causes power frequency interference to the transmitted signal.

[0004] To address signal attenuation during transmission caused by a fixed signal frequency, the transmitting system has been improved to detect the real-time resonant frequency of the transmitting coil in the ground layer and use this resonant frequency as the transmission frequency. Therefore, the existing receiving system also needs to be improved to accommodate the improved transmitting system; otherwise, forced decoding will result in a high bit error rate. Summary of the Invention

[0005] This invention provides a system and method for receiving downhole wireless signals to solve the technical problem of high bit error rate after decoding in existing receiving systems.

[0006] Firstly, a downhole wireless signal receiving system is provided, comprising:

[0007] The detection module is used to detect the current resonant frequency of the receiving coil at preset time intervals or at preset drilling distances.

[0008] The decoding module is used to enable the receiving coil to receive the analog signal sent by the transmitting coil according to the current resonant frequency, and to decode the received analog signal according to the current resonant frequency.

[0009] In some embodiments, the process by which the detection module detects the current resonant frequency of the receiving coil includes:

[0010] Step S101: Generate five signals of different frequencies according to the preset initial center frequency and the initial frequency selection step size;

[0011] Step S102: Generate corresponding AC voltage signals based on five different frequency signals and input them to the receiving coil;

[0012] Step S103: Convert the five AC voltage signals from the receiving coil into five DC voltage signals;

[0013] Step S104: Determine the frequency corresponding to the smallest digital value among the five DC voltage signals, and use this frequency as the center frequency to reduce the frequency selection step size, generating five new signals with different frequencies. Repeat steps 102 to 103 until the current frequency selection step size is not greater than the preset frequency selection step size. Use the frequency corresponding to the DC voltage signal with the current smallest voltage value as the current resonant frequency of the receiving coil.

[0014] In some embodiments, the decoding module is further configured to:

[0015] The analog signal received by the receiving coil is amplified, and then the amplified analog signal is converted into a digital signal.

[0016] In some embodiments, the decoding module is further configured to:

[0017] The converted digital signal is digitally bandpass filtered using the current resonant frequency of the receiving coil as the center frequency.

[0018] In some embodiments, the process by which the decoding module decodes the received analog signal according to the current resonant frequency includes:

[0019] The signal after digital bandpass filtering is compared with zero to generate a level signal. The current resonant frequency is used as the reference time, and the number of level signal transition edges in each reference time is counted.

[0020] Calculate the average total number of level signal transition edges over several reference time periods, and compare the number of level signal transition edges in each reference time period with the average total number.

[0021] The converted digital signal is decoded based on the comparison results.

[0022] Secondly, a method for receiving downhole wireless signals is provided, comprising the following steps:

[0023] The current resonant frequency of the receiving coil is detected at preset intervals or after each preset drilling distance.

[0024] The receiving coil receives the analog signal sent by the transmitting coil according to the current resonant frequency, and decodes the received analog signal according to the current resonant frequency.

[0025] In some embodiments, the step of detecting the current resonant frequency of the receiving coil includes:

[0026] Step S101: Generate five signals of different frequencies according to the preset initial center frequency and the initial frequency selection step size;

[0027] Step S102: Generate corresponding AC voltage signals based on five different frequency signals and input them to the receiving coil;

[0028] Step S103: Convert the five AC voltage signals from the receiving coil into five DC voltage signals;

[0029] Step S104: Determine the frequency corresponding to the smallest digital value among the five DC voltage signals, and use this frequency as the center frequency to reduce the frequency selection step size, generating five new signals with different frequencies. Repeat steps S102 to S103 until the current frequency selection step size is not greater than the preset frequency selection step size. Use the frequency corresponding to the DC voltage signal with the current smallest voltage value as the current resonant frequency of the receiving coil.

[0030] In some embodiments, prior to the step of decoding the received analog signal according to the current resonant frequency, the following steps are included:

[0031] The analog signal received by the receiving coil is amplified, and then the amplified analog signal is converted into a digital signal.

[0032] In some embodiments, after the step of converting the amplified analog signal into a digital signal, the method includes:

[0033] The converted digital signal is digitally bandpass filtered using the current resonant frequency of the receiving coil as the center frequency.

[0034] In some embodiments, the step of decoding the received analog signal according to the current resonant frequency includes:

[0035] The signal after digital bandpass filtering is compared with zero to generate a level signal. The current resonant frequency is used as the reference time, and the number of level signal transition edges in each reference time is counted.

[0036] Calculate the average total number of level signal transition edges over several reference time periods, and compare the number of level signal transition edges in each reference time period with the average total number.

[0037] The converted digital signal is decoded based on the comparison results.

[0038] The beneficial effects of the technical solution provided by this invention include:

[0039] This invention provides a downhole wireless signal receiving system and method. The receiving system includes a detection module and a decoding module. The detection module detects the current resonant frequency of the receiving coil, and the decoding module enables the receiving coil to receive the analog signal transmitted by the transmitting coil according to the current resonant frequency. The received analog signal is decoded according to the current resonant frequency. The frequency of the received signal is adapted to the frequency of the transmitting coil, and the decoding is adaptively performed according to the change of the current resonant frequency of the receiving coil, resulting in high decoding accuracy. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 A schematic diagram of a downhole wireless signal receiving system provided in an embodiment of the present invention;

[0042] Figure 2 This is a schematic diagram illustrating the process of the detection module detecting the current resonant frequency of the receiving coil according to an embodiment of the present invention.

[0043] Figure 3 This is a schematic diagram illustrating the process of decoding the received analog signal by the decoding module provided in an embodiment of the present invention;

[0044] Figure 4 This is a flowchart illustrating a method for receiving downhole wireless signals according to an embodiment of the present invention. Detailed Implementation

[0045] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] This invention provides a downhole wireless signal receiving system that solves the technical problem of high bit error rate after decoding in existing receiving systems.

[0047] See Figure 1 As shown, this embodiment of the invention provides a downhole wireless signal receiving system, including a detection module and a decoding module.

[0048] The detection module is used to detect the current resonant frequency of the receiving coil at preset time intervals or after each preset drilling distance. The decoding module is used to enable the receiving coil to receive the analog signal sent by the transmitting coil according to the current resonant frequency, and to decode the received analog signal according to the current resonant frequency.

[0049] The downhole wireless signal receiving system in this embodiment of the invention includes a detection module and a decoding module. The detection module detects the current resonant frequency of the receiving coil, and the decoding module enables the receiving coil to receive the analog signal transmitted by the transmitting coil according to the current resonant frequency, and decodes the received analog signal according to the current resonant frequency. The frequency of the received signal is adapted to the frequency of the transmitting coil, and the system adaptively decodes according to changes in the current resonant frequency of the receiving coil, resulting in high decoding accuracy.

[0050] As an optional implementation, in one embodiment of the invention, see [link to relevant documentation]. Figure 2 As shown, the process by which the detection module detects the current resonant frequency of the receiving coil includes:

[0051] Step S101: Generate five signals of different frequencies based on a preset initial center frequency and an initial frequency selection step size. Optionally, a parameter control unit can be set up to input the initial center frequency and the initial frequency selection step size to generate five signals of different frequencies. Each frequency signal includes a frequency control word and a phase control word. For example, the resonant frequency of the actual receiving coil on the ground is determined in advance, and then five signals of different frequencies are generated by adding or subtracting 10kHz and 20kHz from this frequency as the center. For example, with a center frequency of 100kHz, the five different frequency signals are 80kHz, 90kHz, 100kHz, 110kHz, and 120kHz, which is equivalent to an initial frequency selection step size of 10kHz.

[0052] Step S102: Generate corresponding AC voltage signals based on five different frequency signals and input them to the receiving coil. Optionally, the above function can be achieved using a DDS chip. The function of the DDS chip is to generate a sinusoidal signal of a certain frequency. Its inputs are a frequency control word and a phase control word, and its output is the sinusoidal signal corresponding to the frequency control word and the phase control word. The frequency control word and the phase control word come from the parameter control unit. Further, since the DDS chip generates a bias sinusoidal signal, a bias circuit can be set. The function of the bias circuit is to convert the bias sinusoidal signal generated by the DDS chip into a standard sinusoidal signal. For example, if the amplitude range of the sinusoidal signal generated by the DDS chip is 0 to 0.6V, the bias circuit can convert the 0 to 0.6V sinusoidal signal into a -0.3 to 0.3V sinusoidal signal through its subtraction function. Further, since the power of the sinusoidal signal generated by the DDS chip is limited, a power amplifier circuit can be set. The function of the power amplifier circuit is to amplify the power of the sinusoidal signal generated by the DDS chip before inputting it to the receiving coil.

[0053] Step S103 converts the five AC voltage signals from the receiving coil into five DC voltage signals. Optionally, an AC-to-DC circuit can be provided, which includes a resistor connected in series with the receiving coil. This resistor converts the AC signal into a DC signal suitable for AD conversion. The design of the AC-to-DC circuit needs to balance the magnitude of its DC ripple and its response speed. The smaller the DC ripple, the more accurate the AD value; the faster the DC response, the more accurate the AD value. DC ripple and DC response are highly correlated with the circuit's capacitance. The larger the capacitance, the smaller the DC ripple, but the slower the DC response; the smaller the capacitance, the larger the DC ripple, but the faster the DC response.

[0054] Step S104: Determine the frequency corresponding to the smallest digital value among the five DC voltage signals, and use this frequency as the center frequency to reduce the frequency selection step size, generating five new signals with different frequencies. Repeat steps S102 to S103 until the current frequency selection step size is not greater than the preset frequency selection step size. Use the frequency corresponding to the DC voltage signal with the current smallest voltage value as the current resonant frequency of the receiving coil.

[0055] Optionally, an analog-to-digital (AD) converter chip can be included to convert the DC physical analog signal output from the AC-to-DC circuit into a digital signal, facilitating subsequent determination of which DC voltage value among multiple DC voltage signals has the smallest value. Further, an iterative calculation unit can be included. This unit determines the frequency corresponding to the smallest DC voltage value among the five DC voltage signals, and using this frequency as the center frequency, reduces the frequency selection step size to generate five new signals of different frequencies. This process continues until the current frequency selection step size is no greater than a preset frequency selection step size. The frequency corresponding to the DC voltage signal with the current smallest voltage value is then used as the current resonant frequency of the receiving coil. The preset frequency selection step size can be 1 kHz or 0.1 kHz.

[0056] It should be noted that the detection module can be equipped with a microcontroller unit (MCU), and the above steps can be executed by the microcontroller unit (MCU) controlling the parameter control unit, DDS chip, AC to DC circuit, analog to digital conversion chip, iterative calculation unit, etc.

[0057] As an optional implementation, in one embodiment of the invention, see [link to relevant documentation]. Figure 3 As shown, the decoding module is also used to: amplify the analog signal received by the receiving coil, and then convert the amplified analog signal into a digital signal.

[0058] Specifically, the decoding module can be equipped with a constant amplitude amplification unit and an analog-to-digital conversion unit to amplify the small analog signal received by the receiving coil with a constant amplitude. The peak-to-peak value of the amplified analog signal is constant, which is beneficial for subsequent signal processing. The analog-to-digital conversion unit converts the amplified analog signal into a digital signal.

[0059] As an optional implementation, in one embodiment of the invention, see [link to relevant documentation]. Figure 3 As shown, the decoding module is also used to: perform digital bandpass filtering on the converted digital signal using the current resonant frequency of the receiving coil as the center frequency.

[0060] Specifically, the decoding module can be equipped with a digital bandpass filter unit, which determines the start and cutoff frequencies of the digital bandpass filter based on the current resonant frequency of the receiving coil as the center frequency, performs digital bandpass filtering on the converted digital signal, allows a certain range of frequencies to pass through, filters out other frequencies, and ensures the accuracy of the signal.

[0061] As an optional implementation, in one embodiment of the invention, the process by which the decoding module decodes the received analog signal according to the current resonant frequency includes:

[0062] The signal after digital bandpass filtering is compared with zero to generate a level signal. The current resonant frequency is used as the reference time, and the number of level signal transition edges in each reference time is counted.

[0063] Calculate the average total number of level signal transition edges over several reference time periods, and compare the number of level signal transition edges in each reference time period with the average total number.

[0064] The converted digital signal is decoded based on the comparison results.

[0065] Specifically, the decoding module can be configured with a decoding unit. Assuming the transmitting coil sends an analog signal of the decimal number 2, and the current resonant frequency of the receiving coil is 10kHz, the specific process is explained below:

[0066] The analog signal of the decimal number 2, after amplification, digital conversion, and digital bandpass filtering, is theoretically 8 bits of binary data 00000010 (8 bits as a data byte).

[0067] Determine if the filtered value is greater than zero. If the value is greater than zero, output a zero-crossing comparison value of 1 (indicating a high level); if the value is less than or equal to zero, output a zero-crossing comparison value of 0 (indicating a low level).

[0068] The system determines whether the zero-crossing comparison values ​​of adjacent sampling points are the same. If the zero-crossing comparison values ​​are the same, it indicates that there is no rising edge, and the value is marked as 0. If the zero-crossing comparison values ​​are different, it indicates that there is a rising edge, and the value is marked as 1. The sampling frequency is greater than the current resonant frequency, which is 10kHz. The sampling frequency can be 100kHz. The reciprocal of the current resonant frequency is used as the sampling time for one bit, i.e., the reference time. Ten points can be sampled within each reference time.

[0069] Calculate the average number of transition edges with a value of 1 at the 8 reference time outputs, which is the average total number of transition edges within the 8-bit binary data time. Compare the actual value of each data bit's transition edge within a reference time with the average number of transition edges; if the actual value is less than the average, set the data bit to 1; if the actual value is greater than or equal to the average, set the data bit to 0.

[0070] Convert each data bit to decimal data, and the decoding of a single 8-bit binary data is complete.

[0071] See Figure 4 As shown, this embodiment of the invention provides a method for receiving downhole wireless signals, including the following steps:

[0072] Step S10: Detect the current resonant frequency of the receiving coil at preset time intervals or at preset drilling distances.

[0073] Step S20: The receiving coil receives the analog signal sent by the transmitting coil according to the current resonant frequency, and decodes the received analog signal according to the current resonant frequency.

[0074] As an optional implementation, in one embodiment of the invention, the step of detecting the current resonant frequency of the receiving coil includes:

[0075] Step S101: Generate five signals of different frequencies according to the preset initial center frequency and the initial frequency selection step size;

[0076] Step S102: Generate corresponding AC voltage signals based on five different frequency signals and input them to the receiving coil;

[0077] Step S103: Convert the five AC voltage signals from the receiving coil into five DC voltage signals;

[0078] Step S104: Determine the frequency corresponding to the smallest digital value among the five DC voltage signals, and use this frequency as the center frequency to reduce the frequency selection step size, generating five new signals with different frequencies. Repeat steps S102 to S103 until the current frequency selection step size is not greater than the preset frequency selection step size. Use the frequency corresponding to the DC voltage signal with the current smallest voltage value as the current resonant frequency of the receiving coil.

[0079] As an optional implementation, in one embodiment of the invention, before the step of decoding the received analog signal according to the current resonant frequency, the following steps are included:

[0080] The analog signal received by the receiving coil is amplified, and then the amplified analog signal is converted into a digital signal.

[0081] As an optional implementation, in one embodiment of the invention, after the step of converting the amplified analog signal into a digital signal, the method further includes:

[0082] The converted digital signal is digitally bandpass filtered using the current resonant frequency of the receiving coil as the center frequency.

[0083] As an optional implementation, in one embodiment of the invention, the step of decoding the received analog signal according to the current resonant frequency includes:

[0084] The signal after digital bandpass filtering is compared with zero to generate a level signal. The current resonant frequency is used as the reference time, and the number of level signal transition edges in each reference time is counted.

[0085] Calculate the average total number of level signal transition edges over several reference time periods, and compare the number of level signal transition edges in each reference time period with the average total number.

[0086] The converted digital signal is decoded based on the comparison results.

[0087] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0088] It should be noted that in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0089] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A system for receiving a wireless signal downhole, the system comprising: The method comprises the following steps: detecting the current resonant frequency of the receiving coil every preset time interval or every preset drilling distance; decoding the analog signal received by the receiving coil according to the current resonant frequency, and decoding the received analog signal according to the current resonant frequency. The process that the detection module detects the current resonant frequency of the receiving coil every preset time interval or every preset drilling distance comprises the following steps: Step S101: generating five signals with different frequencies according to a preset initial center frequency and an initial frequency selection step; Step S102: generating corresponding alternating voltage signals according to the five signals with different frequencies and inputting the alternating voltage signals into the receiving coil; Step S103: converting the five alternating voltage signals of the receiving coil into five direct current voltage signals; Step S104: determining the frequency corresponding to the minimum digital quantity in the five direct current voltage signals, taking the frequency as a center frequency, reducing the frequency selection step, generating five new signals with different frequencies, repeating steps S102-S103 until the current frequency selection step is not greater than the preset frequency selection step, and taking the frequency corresponding to the direct current voltage signal with the current minimum voltage value as the current resonant frequency of the receiving coil. The process that the decoding module decodes the received analog signal according to the current resonant frequency comprises the following steps: generating a level signal by performing zero-crossing comparison on the digital band-pass filtered signal, taking the current resonant frequency as a reference time, and counting the number of level signal transition edges in each reference time; comparing the number of level signal transition edges in each reference time with the total number average; decoding the converted digital signal according to the comparison result.

2. The system for receiving a wireless signal downhole as defined in claim 1, wherein, The decoding module is further configured to: amplify the analog signal received by the receiving coil; convert the amplified analog signal into a digital signal.

3. The system for receiving a wireless signal downhole as defined in claim 2, wherein, The decoding module is further configured to: perform digital band-pass filtering on the converted digital signal by taking the current resonant frequency of the receiving coil as a center frequency.

4. A method of receiving a wireless signal downhole, the method comprising: The method comprises the following steps: detecting the current resonant frequency of the receiving coil every preset time interval or every preset drilling distance; decoding the analog signal received by the receiving coil according to the current resonant frequency, and decoding the received analog signal according to the current resonant frequency. The step of detecting the current resonant frequency of the receiving coil every preset time interval or every preset drilling distance comprises the following steps: Step S101: generating five signals with different frequencies according to a preset initial center frequency and an initial frequency selection step; Step S102: generating corresponding alternating voltage signals according to the five signals with different frequencies and inputting the alternating voltage signals into the receiving coil; Step S103: converting the five alternating voltage signals of the receiving coil into five direct current voltage signals; Step S104: determining the frequency corresponding to the minimum digital quantity in the five direct current voltage signals, taking the frequency as a center frequency, reducing the frequency selection step, generating five new signals with different frequencies, repeating steps S102-S103 until the current frequency selection step is not greater than the preset frequency selection step, and taking the frequency corresponding to the direct current voltage signal with the current minimum voltage value as the current resonant frequency of the receiving coil. The step of decoding the received analog signal according to the current resonant frequency comprises: Zero-crossing comparison is performed on the digital band-pass filtered signal to generate a level signal, and the current resonant frequency is used as a reference time, and the number of level signal transition edges in each reference time is counted; The average number of level signal transition edges in a plurality of reference times is calculated, and the number of level signal transition edges in each reference time is compared with the average number; The converted digital signal is decoded according to the comparison result.

5. The method of claim 4, wherein, Before the step of decoding the received analog signal according to the current resonant frequency, the step of: The received analog signal received by the receiving coil is amplified, and then the amplified analog signal is converted into a digital signal.

6. The method of receiving a wireless signal downhole as defined in claim 5, wherein, After the step of converting the amplified analog signal into a digital signal, the step of: The converted digital signal is digitally band-pass filtered with the current resonant frequency of the receiving coil as the center frequency.

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