A method for calculating interwell electromagnetic wave amplitude and phase

Abstract

The application discloses a kind of interwell electromagnetic wave amplitude and phase calculation method, comprising: deployment electromagnetic transmitter and electromagnetic receiver;Under the control of transmission synchronization signal, electromagnetic transmission instruction containing fixed period serial number and transmission frequency information is received by transmitter downhole instrument to prepare transmission;When being ready to receive, electromagnetic wave signal of specified frequency is transmitted by transmitter downhole instrument;Under the control of reception synchronization signal, electromagnetic wave signal is received and collected, the initial amplitude and phase of electromagnetic wave signal are calculated, and it is uploaded to receiving ground machine, and the waveform data of the current electromagnetic wave signal collected is stored;Different fixed period electromagnetic wave waveform data is read by receiving ground machine, and spectrum analysis is carried out, and the initial amplitude and phase calculated by different fixed period are iteratively corrected using spectrum analysis result.The application has the characteristics of simple algorithm, accurate and reliable result, and is easy to implement.

Description

Technical Field

[0001] This invention relates to the field of mine geophysics, and in particular to a method for calculating the amplitude and phase of electromagnetic waves between wells. Background Technology

[0002] In inter-well electromagnetic logging, the electromagnetic transmitter emits electromagnetic waves downhole, which penetrate the metal casing, resulting in severe signal attenuation. After traveling a long distance through the formation to the electromagnetic receiver, the signal is further attenuated, becoming extremely weak and containing numerous interference signals. Often, these interference signals are far greater than the received useful signal. Therefore, accurately extracting the amplitude and phase of these electromagnetic wave signals that need to be effectively transmitted directly affects the accuracy of the measurement (inter-well electromagnetic logging).

[0003] Existing amplitude and phase extraction methods utilize cross-correlation algorithms downhole. Once extracted, this method is irreversible, regardless of its accuracy. Furthermore, due to limitations imposed by downhole high temperatures, confined spaces, and real-time measurement requirements, existing extraction methods rely on overly simplistic calculations, resulting in large errors and difficulty in guaranteeing precision and accuracy.

[0004] Therefore, existing technologies need to provide a new scheme for calculating the amplitude and phase of electromagnetic waves between wells in order to solve one or more of the above-mentioned technical problems. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for calculating the amplitude and phase of electromagnetic waves between wells, comprising: deploying an electromagnetic transmitter and an electromagnetic receiver, wherein the electromagnetic transmitter and the electromagnetic receiver communicate with each other via a synchronization signal at preset fixed time intervals; under the control of the transmission synchronization signal, the downhole transmitter receives an electromagnetic transmission command containing a fixed period number and transmission frequency information to prepare for transmission; when ready to receive, the downhole transmitter transmits an electromagnetic wave signal of a specified frequency; under the control of the reception synchronization signal, the electromagnetic wave signal is received and acquired, the initial amplitude and phase of the electromagnetic wave signal are calculated, and uploaded to the receiving ground unit, and the waveform data of the acquired current electromagnetic wave signal is stored; the receiving ground unit reads electromagnetic wave waveform data of different fixed periods, performs spectrum analysis, and uses the spectrum analysis results to iteratively correct the initial amplitude and phase calculated for different fixed periods.

[0006] Preferably, the step of receiving an electromagnetic transmission command containing a fixed period sequence number and transmission frequency information by the downhole instrument of the transmitter further includes: under the control of a transmission synchronization signal, the ground transmitter sends the electromagnetic transmission command to the downhole instrument of the transmitter; the ground transmitter sends a first notification of the current fixed period start to the ground receiver via a wireless communication network, wherein the first notification includes the electromagnetic transmission command; under the control of the reception synchronization signal, the downhole instrument of the receiver receives the first notification forwarded by the ground receiver, thereby preparing to receive.

[0007] Preferably, the process of calculating the initial amplitude and phase of the electromagnetic wave signal includes: sampling the electromagnetic wave signal M*N times, determining the corresponding sampling interval, and forming a first sampling sequence data, where M represents the sampling period and N represents the number of samples per unit sampling period; obtaining the second sampling sequence data corresponding to the received synchronization signal, and calculating the initial amplitude and phase based on the first sampling sequence data and the second sampling sequence data, using the cross-correlation relationship between the received signal and the received synchronization signal.

[0008] Preferably, the initial amplitude and phase are calculated according to the following expression:

[0009] r(n)=cos(2nπ / N)+jsin(2nπ / N)=r a (n)+r b (n), n = 0, 1, ..., MN-1,

[0010]

[0011]

[0012]

[0013] θ = -arctg(b / a)

[0014] Where r(n) represents the second sampled sequence data, n represents the sequence number, and s R (n) represents the first sampled sequence data, V represents the initial amplitude, and θ represents the initial phase.

[0015] Preferably, the step of calculating the initial amplitude and phase of the electromagnetic wave signal and uploading it to the receiving ground unit further includes: under the control of the transmission synchronization signal, the transmitting ground unit sends a notification to the transmitting downhole instrument to stop transmitting electromagnetic waves, and simultaneously sends a notification to the receiving ground unit to stop receiving electromagnetic waves, so that under the control of the receiving synchronization signal, the receiving ground unit sends the notification to stop receiving electromagnetic waves to the receiving downhole instrument.

[0016] Preferably, the depth count, transmission and reception ordinal numbers are also transmitted to the receiving ground unit along with the initial amplitude and phase.

[0017] Preferably, the stored waveform data of the electromagnetic wave signal includes control head information and electromagnetic wave data. The control head information includes transmission control and reception control. The transmission control includes, but is not limited to, the sequence number of the transmission synchronization signal, the sequence number of the transmission period, and the transmission depth count. The reception control includes, but is not limited to, the reception depth count, the oversampling count, and the number of samples. The electromagnetic wave data includes the digitized original waveform sequence data of the current electromagnetic wave signal.

[0018] Preferably, the process of reading electromagnetic wave waveform data with different fixed periods and performing spectrum analysis includes: determining the transmission main frequency band, main frequency, and power frequency and harmonic interference frequencies of the waveform data of each electromagnetic wave signal; performing adaptive notch filtering on the first sampling sequence data corresponding to the currently acquired electromagnetic wave signal based on the power frequency and harmonic interference frequencies, and performing phase-locked amplification on the current electromagnetic wave signal based on this and the main frequency; using the first sampling sequence data after phase-locked amplification as a new received signal, calculating the secondary amplitude and phase using the cross-correlation relationship between the received signal and the received synchronization signal; determining the error between the initial amplitude and phase and the secondary amplitude and phase, comparing the calculated error with a preset error threshold, further optimizing the secondary amplitude and phase based on the comparison result, and then replacing the initial amplitude and phase with the secondary amplitude and phase.

[0019] Preferably, when the calculation error is less than or equal to the error threshold, based on the start frequency and cutoff frequency corresponding to the waveform data of the current electromagnetic wave signal, the first sampled sequence data after phase-locked loop amplification is first subjected to a specified bandpass filter, and then the first sampled sequence data after bandpass filtering is used as a new received signal, so as to use the cross-correlation relationship between the received signal and the received synchronization signal to calculate the optimized final amplitude and phase.

[0020] Preferably, the fixed time interval corresponds to a period that is twice the period of the synchronization signal. n Both the electromagnetic transmitter and receiver are independently synchronized using a edge-controlled method.

[0021] Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects:

[0022] This invention discloses a method for calculating the amplitude and phase of electromagnetic waves in wellbore logging. The method utilizes the correlation between transmitted and received electromagnetic waves, combined with a synchronization signal, to initially calculate the initial amplitude and phase. Then, using real-time electromagnetic wave waveforms stored downhole on the surface, the waveform data undergoes phase-locked amplification and adaptive notch filtering iterative correction. Finally, a bandpass filter is used to obtain more accurate final amplitude and phase information. The amplitude and phase extraction scheme for inter-well electromagnetic logging described in this invention combines the advantages of simple algorithm, accurate and reliable results, ease of implementation, no hardware modification required, and complete adaptability to downhole scenarios involving high temperatures, confined spaces, and real-time measurements.

[0023] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0024] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0025] Figure 1 This is a step diagram illustrating the method for calculating the amplitude and phase of inter-well electromagnetic waves according to an embodiment of this application.

[0026] Figure 2 This is a schematic diagram illustrating the specific process of calculating the amplitude and phase of electromagnetic waves between wells according to an embodiment of this application.

[0027] Figure 3 This is a schematic diagram illustrating the process of calculating the initial amplitude and phase information in the method for calculating the amplitude and phase of electromagnetic waves between wells according to an embodiment of this application.

[0028] Figure 4 This is a schematic flowchart illustrating the optimization of initial amplitude and phase in the method for calculating the amplitude and phase of inter-well electromagnetic waves according to an embodiment of this application. Detailed Implementation

[0029] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that, as long as there is no conflict, the various embodiments and features in the various embodiments of the present invention can be combined with each other, and the resulting technical solutions are all within the protection scope of the present invention.

[0030] Furthermore, the steps illustrated in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Also, although a logical order is shown in the flowcharts, in some cases the steps shown or described may be performed in a different order than that shown here.

[0031] In inter-well electromagnetic logging, the electromagnetic transmitter emits electromagnetic waves downhole, which penetrate the metal casing, resulting in severe signal attenuation. After traveling a long distance through the formation to the electromagnetic receiver, the signal is further attenuated, becoming extremely weak and containing numerous interference signals. Often, these interference signals are far greater than the received useful signal. Therefore, accurately extracting the amplitude and phase of these electromagnetic wave signals that need to be effectively transmitted directly affects the accuracy of the measurement (inter-well electromagnetic logging).

[0032] Existing amplitude and phase extraction methods utilize cross-correlation algorithms downhole. Once extracted, this method is irreversible, regardless of its accuracy. Furthermore, due to limitations imposed by downhole high temperatures, confined spaces, and real-time measurement requirements, existing extraction methods rely on overly simplistic calculations, resulting in large errors and difficulty in guaranteeing precision and accuracy.

[0033] Therefore, to solve the above-mentioned technical problems, this application proposes a method for calculating the amplitude and phase of electromagnetic waves between wells. The method includes: after a transmitter downhole instrument emits an electromagnetic wave signal for a current fixed period, a receiver downhole instrument receives the current electromagnetic wave signal; based on the current electromagnetic wave signal and combined with the receiving synchronization signal transmitted between the receiver downhole instrument and the ground receiving instrument in real-time communication, the initial amplitude and phase information of the current electromagnetic wave signal is extracted, and the real-time waveform data of the current electromagnetic wave signal is stored; finally, the ground receiving instrument optimizes and corrects the initial amplitude and phase information based on real-time waveform data for different fixed periods, thereby obtaining accurate amplitude and phase information of the original transmitted electromagnetic wave signal. Thus, the calculation method disclosed in this invention can not only calculate the required accurate amplitude and phase characteristic information, but also facilitates the recovery of the transmitted original signal.

[0034] Figure 1 This is a step diagram illustrating the method for calculating the amplitude and phase of inter-well electromagnetic waves according to an embodiment of this application. Figure 2 This is a schematic diagram illustrating the specific process of calculating the amplitude and phase of inter-well electromagnetic waves according to an embodiment of this application. The following is in conjunction with... Figure 1 and Figure 2 The method for calculating the amplitude and phase of inter-well electromagnetic waves (hereinafter referred to as the "amplitude and phase calculation method") described in the embodiments of the present invention will be explained.

[0035] Step S110 deploys the electromagnetic transmitter and electromagnetic receiver required for the application scenario of the amplitude and phase calculation method described in this embodiment of the invention. In this embodiment, the electromagnetic transmitter is the starting point of the control core. The electromagnetic transmitter and electromagnetic receiver can be located at different depths in the same well or in two separate wells. The electromagnetic transmitter includes a (electromagnetic) ground transmitter and a downhole transmitter instrument located underground. The electromagnetic receiver includes a (electromagnetic) ground receiver and a downhole receiver instrument located underground. The ground transmitter and ground receiver perform periodic calibration through a synchronization mechanism. One calibration cycle is recorded as a fixed cycle, ensuring that the error between the synchronization signals of the transmitter and receiver is less than 50 ns. Communication between the ground transmitter and ground receiver is achieved by exchanging synchronization signals at preset fixed time intervals. Furthermore, the period corresponding to the fixed time interval is twice the period of the synchronization signal. n Furthermore, both the electromagnetic transmitter and receiver employ independent synchronization via a controlled-path approach. Specifically, the transmitting ground unit, under the control of the transmitting synchronization signal, will wirelessly communicate with the receiving ground unit to transmit relevant data, information, and / or commands. Similarly, the receiving ground unit, under the control of the receiving synchronization signal, will wirelessly communicate with the transmitting ground unit to transmit relevant data, information, and / or commands.

[0036] Furthermore, the ground transmitter and the downhole transmitter in the electromagnetic transmitter communicate by exchanging transmission synchronization signals, and the ground receiver and the downhole receiver in the electromagnetic receiver communicate by exchanging reception synchronization signals, thus enabling internal communication under the synchronization control of transmission and reception respectively.

[0037] Therefore, after the deployment of the electromagnetic transmitter and receiver is completed, the process proceeds to step S120. (Reference) Figure 1 In step S120, under the control of the transmission synchronization signal, the transmitter downhole instrument receives an electromagnetic transmission command containing a fixed period sequence number and transmission frequency information, so that the transmitter downhole instrument is ready to launch.

[0038] In step S120, refer to Figure 2First, at the start of the current fixed cycle, under the control of the transmission synchronization signal, the ground transmitter sends an electromagnetic transmission command to the downhole transmitter. This electromagnetic transmission command includes at least the following information: the current fixed cycle number, the (specified) transmission frequency of the electromagnetic wave signal to be transmitted, the data sequence corresponding to the transmission synchronization signal, and the sequence number of the transmission cycle (the cycle corresponding to the transmission frequency of the electromagnetic wave signal). Simultaneously with sending the electromagnetic transmission command to the downhole transmitter, the ground transmitter also sends a first notification of the start of the current fixed cycle to the ground receiver via a wireless communication network, and forwards this first notification to both the receiver and the downhole transmitter. This first notification contains the electromagnetic transmission command information.

[0039] Subsequently, under the control of the transmission synchronization signal, the transmitter downhole instrument receives the electromagnetic transmission command from the transmitter ground unit and obtains the current electromagnetic transmission command and its internal information, so that the transmitter downhole instrument prepares to transmit electromagnetic waves. At the same time, under the control of the reception synchronization signal, the receiver downhole instrument receives the first notification from the receiver ground unit and obtains the current electromagnetic transmission command and its internal information, thereby preparing to receive the electromagnetic wave signal transmitted from the transmitter downhole instrument.

[0040] Therefore, after both the downhole instruments at the transmitting and receiving ends are ready for downhole transmission, the process proceeds to step S130. In step S130, when the necessary transmission and reception for downhole transmission are ready, the downhole transmitter emits an electromagnetic wave signal at a specified transmission frequency. In step S130, under the control of the transmission synchronization signal, the downhole transmitter emits an electromagnetic wave signal at the specified transmission frequency, causing the emitted electromagnetic waveform to enter the formation or pass through the casing into the formation, so that the current electromagnetic wave signal is received by the downhole receiver, thus proceeding to step S140. The waveform of the electromagnetic wave (transmission) signal emitted by the downhole transmitter is represented by the following expression:

[0041] s(t)=Vcos(ω0t) (1)

[0042] Where s(t) represents the electromagnetic wave signal required for inter-well electromagnetic measurement (where s T (t) represents the electromagnetic wave signal emitted by the downhole transmitter, s R (t) represents the electromagnetic wave signal received by the downhole receiver, t represents the current time of the electromagnetic wave signal, V represents the real-time amplitude of the current electromagnetic wave signal (which is also the amplitude to be recovered that the downhole receiver needs to calculate, i.e., the initial amplitude), and ω0 represents the specified transmission frequency.

[0043] In step S140, under the control of the receiving synchronization signal, the receiver downhole instrument receives and collects the electromagnetic wave signal emitted by the transmitter downhole instrument, calculates the initial amplitude and initial phase of the current electromagnetic wave signal, and in step S150, uploads the currently calculated initial amplitude and initial phase to the receiver ground instrument. At the same time as calculating the initial amplitude and initial phase, step S160 also stores the waveform data of the electromagnetic wave signal (for the current fixed period) collected in real time by the receiver downhole instrument.

[0044] Figure 3 This is a schematic flowchart illustrating the calculation of the initial amplitude and phase information in the method for calculating the amplitude and phase of inter-well electromagnetic waves according to an embodiment of this application. In step S140, combined with... Figure 2 and Figure 3 First, under the control of the receiving synchronization signal, the downhole receiver receives and acquires electromagnetic wave signals. Supported by a theoretical model, the waveform of the received electromagnetic wave signal is represented by the following expression:

[0045] s R (t)=Vcos(ω0t+θ)+Noise (2)

[0046] Where θ represents the initial phase, and Noise represents the interference signal (noise signal) during downhole signal transmission. Furthermore, the waveform of the receiving synchronization signal received in real time by the downhole receiver is represented by the following expression:

[0047] r(t)=cos(ω0t)+jsin(ω0t) (3)

[0048] Where j represents the imaginary number sign. In practical applications, since the noise signal is uncorrelated with the measured received signal s(t), but the cross-correlation function between the measured received signal and the received synchronization signal is: Therefore, the in-phase component a is defined as: The orthogonal component b is:

[0049] Then, the receiver downhole instrument digitizes the electromagnetic wave signals emitted from the transmitter downhole instrument, which are collected in real time. Specifically, the current electromagnetic wave signal is sampled M*N times to determine the corresponding sampling interval t. s This forms the first sampling sequence data. Additionally, the downhole receiver directly acquires the sequence data corresponding to the received synchronization signal (i.e., the transmitter signal) received during communication with the ground receiver via communication and synchronization between the transmitter and receiver; this is the second sampling sequence data. Here, M represents the sampling period, and N represents the number of samples per sampling period.

[0050] Next, the first and second sampling sequence data are acquired. Based on the digitized real-time acquired electromagnetic wave signal, the initial amplitude and initial phase of the electromagnetic wave signal acquired in real-time at the current fixed period are calculated using the cross-correlation relationship between the received signal and the receiving synchronization signal. The first and second sampling sequence data are represented by the following expressions:

[0051] s R (n)=Vcos(2nπ / N+θ) (4)

[0052] r(n)=cos(2nπ / N)+jsin(2nπ / N)=r a (n)+r b (n) (5)

[0053] Among them, s R (n) represents the first sampled sequence data, r(n) represents the second sampled sequence data, and n represents the sequence number. Further, based on the above expressions (4) and (5), using the cross-correlation relationship between the received signal and the received synchronization signal, the initial amplitude and initial phase are calculated using the following expressions:

[0054]

[0055]

[0056]

[0057] θ=-arctg(b / a) (9)

[0058] Thus, in this embodiment of the invention, the amplitude and phase of the electromagnetic wave signal transmitted downhole are calculated using the above expressions (4) to (9) for the current fixed period, and the initial amplitude and initial phase are obtained, thereby obtaining the initial amplitude and phase for calculation, and then proceeding to step S150.

[0059] In step S150, refer to Figure 2 Under the control of the transmission synchronization signal, the transmitting ground unit sends a (second) notification to the transmitting downhole instrument to stop transmitting electromagnetic wave signals, and at the same time sends a (third) notification to the receiving ground unit to stop receiving electromagnetic waves, so that the receiving ground unit can send the current third notification to the receiving downhole instrument under the control of the receiving synchronization signal.

[0060] Then, the transmitting ground unit continues to send a (fourth) notification, representing the initial amplitude and phase transmitted by the receiving ground unit, to the receiving ground unit via a wireless network. After the receiving ground unit receives the current fourth notification, it sends the current fourth notification to the receiving downhole instrument under the control of the receiving synchronization signal.

[0061] Subsequently, upon receiving the fourth notification, the downhole receiver transmits the calculated initial amplitude and initial phase for the current fixed period to the ground receiver. In addition to uploading the initial amplitude and phase, the downhole receiver also transmits basic characteristic information, including at least the depth count (depth statistics during the transmission and reception of the electromagnetic wave signal) and the transmission and reception sequence numbers (the sequence numbers of the transmission and sampling periods), along with the initial amplitude and phase, to the ground receiver. After receiving the initial amplitude and phase for the current fixed period, as well as the basic characteristic information, the ground receiver stores the received information and, under the control of the receiving synchronization signal, feeds back the currently received information to the transmitting ground receiver. At this point, under the control of the transmitting synchronization signal, the transmitting ground receiver receives and stores the initial amplitude and phase for the current fixed period fed back from the ground receiver.

[0062] In addition, while the receiver downhole instrument calculates the initial amplitude and initial phase of the current fixed period (step S140), in step S160, under the control of the receiving synchronization signal, after receiving and acquiring the electromagnetic wave signal in real time, the receiver downhole instrument also stores the waveform data of the electromagnetic wave signal obtained in real time into its internal serial memory. In this embodiment of the invention, the stored waveform data of the electromagnetic wave signal includes: control header information and electromagnetic wave data. The control header information includes: transmission control and reception control. Transmission control includes, but is not limited to: the sequence number of the transmission synchronization signal, the sequence number of the transmission period, and the transmission depth count (depth statistics when transmitting the electromagnetic wave signal). Reception control includes, but is not limited to: the reception depth count (depth statistics when receiving the electromagnetic wave signal), the oversampling count (the sequence number of the sampling period), and the number of samples (the total number of sampled data points). The electromagnetic wave data is the digitized sequence data of the original waveform of the current electromagnetic wave signal (i.e., the first sampling sequence data).

[0063] After completing the calculation and uploading of the initial amplitude and phase data for the current fixed period, and completing the local storage of the real-time acquired information, the current fixed period ends, thus completing the measurement task of the initial amplitude and phase information for the current fixed period. After the electromagnetic transmitter and electromagnetic receiver synchronize for time synchronization, the next fixed period begins (initiating the measurement task of the initial amplitude and phase information for the next fixed period). Thus, steps S120 to S160 are repeated continuously. After completing the measurement of the initial amplitude and phase information for all fixed periods, the process proceeds to step S170.

[0064] In step S170, the ground receiver reads electromagnetic wave waveform data (waveform data of electromagnetic wave signals) for different fixed periods and performs spectrum analysis. The initial amplitude and initial phase information calculated for different fixed periods are iteratively corrected using the spectrum analysis results, so that the corresponding (accurate) final amplitude and final phase information are obtained for each fixed period.

[0065] Continue to refer to Figure 2 In step S170, the receiver ground unit reads the waveform data of electromagnetic wave signals corresponding to different fixed periods stored in real time by the receiver downhole instrument. Based on the basic characteristic information stored by the receiver ground unit and the control head information in the waveform data of the electromagnetic wave signals, the receiver ground unit associates the initial amplitude and phase information for different fixed periods with the electromagnetic wave data in the waveform data of the electromagnetic wave signals according to the sequence number of the fixed period, thereby reading out the electromagnetic wave data (first sampling sequence data) corresponding to different fixed periods.

[0066] Then, spectral analysis is performed on the first sampled sequence data of each fixed period to determine the corresponding spectral analysis characteristics (spectral analysis results) for each fixed period. These spectral analysis characteristics include at least: the main transmission frequency band, the main frequency, and the power frequency and harmonic interference frequencies. Finally, based on the spectral analysis results of each fixed period, the initial amplitude and phase information of the corresponding fixed period are optimized and corrected to obtain the corresponding final amplitude and final phase information.

[0067] Since the calculation process for the final amplitude and phase of each fixed period is the same, this embodiment of the invention only uses the calculation process of one fixed period as an example to illustrate the optimization and correction process of the initial amplitude and phase. Figure 4 This is a schematic flowchart illustrating the optimization of initial amplitude and phase in the method for calculating the amplitude and phase of inter-well electromagnetic waves according to an embodiment of this application.

[0068] refer to Figure 4 First, the error threshold required for the correction and optimization process is set. Then, based on the power frequency and harmonic interference frequencies in the current fixed-period spectrum analysis results, adaptive notch filtering is performed on the first sampling sequence data corresponding to the currently acquired electromagnetic wave signal. The adaptive notch filtering is performed using the following expression:

[0069] S'(T)=NotchFilter(s(t), F n ') (10)

[0070] In expression (10), s(t) represents the first sampled sequence data input, F n' represents the power frequency and harmonic interference frequency, and S'(T) represents the first sampled sequence data after adaptive notch filtering. Then, continue to refer to... Figure 4 Based on the first sampled sequence data after adaptive notch filtering, and combined with the dominant frequency in the current fixed-period spectral analysis results, the first sampled sequence data after adaptive notch filtering is subjected to phase-locked amplification. The phase-locked amplification is performed using the following expression:

[0071] S"(T)=LockinFiIter(S'(T), f0') (11)

[0072] Where f0' represents the main frequency, and S(T) represents the first sampled sequence data after being output and amplified by lock-in.

[0073] During the instrument signal reception process, there is a 50Hz (received) signal in both the power supply and space of the downhole receiving instrument. This signal has large harmonics and uneven distribution. Adaptive notch filtering is required to extract the few power frequency interferences that contribute the most (e.g., 50Hz, 100Hz, 150Hz, 200Hz, etc.) and then perform frequency limiting suppression. However, while suppressing power frequency interference, the useful signal will also be suppressed to some extent. The phase-locked amplification here is to compensate for the amplification of the specified frequency (useful signal). In general, it is to continuously suppress power frequency interference while amplifying the useful signal.

[0074] Then, the first sampled sequence data after phase-locked amplification is used as the new received signal, and the secondary amplitude and phase are calculated using the cross-correlation relationship between the received signal and the received synchronization signal. Specifically, the first sampled sequence data after phase-locked amplification is substituted into the s in the above expressions (4) to (9). R In the (n) parameters, the second amplitude V' and the second phase θ' are calculated by utilizing the cross-correlation relationship between the received signal and the received synchronization signal.

[0075] Next, after obtaining the secondary amplitude V' and secondary phase θ', the calculation error between the initial amplitude and phase and the secondary amplitude and phase is further determined, and the calculated error is compared with the preset error threshold. Based on the comparison result, the secondary amplitude V' and secondary phase θ' are further optimized. Then, the calculated secondary amplitude V' and secondary phase θ' are used to replace the initial amplitude and initial phase.

[0076] In one embodiment, if the calculation error is less than or equal to the error threshold, then based on the start frequency and cutoff frequency of the first sampling sequence data corresponding to the currently acquired electromagnetic wave signal, the first sampling sequence data after phase-locked amplification is first subjected to a specified bandpass filter, and then the first sampling sequence data after bandpass filtering is used as a new received signal, so as to use the cross-correlation relationship between the received signal and the received synchronization signal to calculate the optimized final amplitude and phase.

[0077] Specifically, the aforementioned start frequency and cutoff frequency need to be used as the passband frequency range for the current bandpass filtering, so as to utilize the specified passband frequency range to process the first sampled sequence data after lock-in amplification. The specified bandpass filtering is performed according to the following expression:

[0078] S”'(T)=BandPassFiIter(S”(T),FreqS,FreqE) (12)

[0079] Where S”'(T) represents the first sampled sequence data after bandpass filtering, BandPassFiIter is the function used for bandpass filtering, FreqS represents the above-mentioned starting frequency, and FreqE represents the above-mentioned cutoff frequency.

[0080] Finally, refer to Figure 4 The first sampled sequence data after bandpass filtering is used as the new received signal. The final amplitude and phase are calculated using the cross-correlation relationship between the received signal and the received synchronization signal. Specifically, the first sampled sequence data after bandpass filtering is substituted into the s in the above expressions (4) to (9). R In the (n) parameter, the final amplitude V” and the final phase θ” are calculated by utilizing the cross-correlation relationship between the received signal and the received synchronization signal.

[0081] When performing bandpass filtering on the quantized waveform sequence acquired in real time, the bandpass filtering process, based on the previously determined amplitude and phase, performs filtering on the electromagnetic wave waveform with a specified bandwidth to further suppress irrelevant interference and useless signals outside the frequency band.

[0082] In another embodiment, if the calculation error is greater than a preset error threshold, the system automatically enters the adaptive notch filter process, using the above expression (12) to calculate the final amplitude and final phase. This solves the problem that during instrument signal reception, there is a 50Hz signal in the instrument power supply and space, and the harmonics of this signal are large and unevenly distributed, requiring adaptive notch filtering to extract the most contributing power frequency interferences for suppression.

[0083] This invention discloses a method for calculating the amplitude and phase of electromagnetic waves in wellbore logging. The method utilizes the correlation between transmitted and received electromagnetic waves, combined with a synchronization signal, to initially calculate the initial amplitude and phase. Then, using real-time electromagnetic wave waveforms stored downhole on the surface, the waveform data undergoes phase-locked amplification and adaptive notch filtering iterative correction. Finally, a bandpass filter is used to obtain more accurate final amplitude and phase information. The amplitude and phase extraction scheme for inter-well electromagnetic logging described in this invention combines the advantages of simple algorithm, accurate and reliable results, ease of implementation, no hardware modification required, and complete adaptability to downhole scenarios involving high temperatures, confined spaces, and real-time measurements.

[0084] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0085] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0086] The phrase "an embodiment" or "an embodiment" used in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" or "an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0087] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method of calculating interwell electromagnetic wave amplitude and phase, characterized by, The method comprises the following steps: deploying an electromagnetic transmitter and an electromagnetic receiver, and the electromagnetic transmitter and the electromagnetic receiver communicate with each other through a synchronization signal intercommunication mode at a preset fixed time interval; under the control of the transmission synchronization signal, the electromagnetic transmitter receives an electromagnetic transmission instruction containing a fixed cycle number and a transmission frequency information from the transmitter downhole instrument to prepare for transmission; under the control of the transmission synchronization signal, the electromagnetic transmitter transmits an electromagnetic wave signal of a specified frequency; under the control of the reception synchronization signal, the electromagnetic receiver receives and collects the electromagnetic wave signal, calculates the initial amplitude and phase of the electromagnetic wave signal, and uploads them to the receiving ground machine, and stores the waveform data of the collected current electromagnetic wave signal; the receiving ground machine reads the electromagnetic wave waveform data of different fixed cycles and performs spectrum analysis, and iteratively corrects the initial amplitude and phase calculated for different fixed cycles using the spectrum analysis results, wherein, in the process of calculating the initial amplitude and phase of the electromagnetic wave signal, it comprises: sampling the electromagnetic wave signal M*N times to determine the corresponding sampling interval and form a first sampling sequence data, wherein M represents the sampling period and N represents the number of samples per unit sampling period; obtaining the second sampling sequence data corresponding to the receiving synchronization signal, and calculating the initial amplitude and phase using the cross-correlation relationship between the receiving signal and the receiving synchronization signal according to the first sampling sequence data and the second sampling sequence data; wherein, in the process of reading the electromagnetic wave waveform data of different fixed cycles and performing spectrum analysis, it comprises: determining the main frequency band, main frequency and power frequency and harmonic interference frequency of the waveform data of each electromagnetic wave signal; based on the power frequency and harmonic interference frequency, performing adaptive notch filtering processing on the first sampling sequence data corresponding to the current collected electromagnetic wave signal, and based on this, performing phase-locked amplification processing on the current electromagnetic wave signal in combination with the main frequency; the first sampling sequence data after completing the phase-locked amplification processing is used as a new receiving signal, and the twice amplitude and phase are calculated using the cross-correlation relationship between the receiving signal and the receiving synchronization signal; determining the error between the initial amplitude and phase and the twice amplitude and phase, and comparing the calculation error with a preset error threshold, further optimizing the twice amplitude and phase according to the comparison result, and then replacing the initial amplitude and phase with the twice amplitude and phase, which comprises: when the calculation error is less than or equal to the error threshold, according to the start frequency and end frequency corresponding to the waveform data of the current electromagnetic wave signal, first performing specified band-pass filtering processing on the first sampling sequence data after phase-locked amplification, and then using the first sampling sequence data after band-pass filtering as a new receiving signal to calculate the final amplitude and phase after optimization using the cross-correlation relationship between the receiving signal and the receiving synchronization signal.

2. The computational method of claim 1, wherein, In the step of receiving an electromagnetic transmission instruction containing a fixed cycle number and a transmission frequency information by the transmitter downhole instrument, it further comprises: under the control of the transmission synchronization signal, the electromagnetic transmitter transmits the electromagnetic transmission instruction to the transmitter downhole instrument by the transmission ground machine. The transmitting ground machine sends a first notification of the current fixed cycle start to the receiving ground machine through the wireless communication network, wherein the first notification contains the electromagnetic emission instruction; Under the control of the receiving synchronization signal, the receiver downhole instrument receives the first notification forwarded by the receiving ground machine, thereby preparing for receiving.

3. The computational method of claim 1, wherein, The initial amplitude and phase are calculated according to the following expression: wherein, r(n) represents the second sample sequence data, n represents a sequence number, represents the first sample sequence data, V represents an initial amplitude, represents an initial phase.

4. The calculation method according to any one of claims 1 to 3, characterized in that, In the step of calculating the initial amplitude and phase of the electromagnetic wave signal and uploading it to the receiving ground machine, it further includes: Under the control of the transmitting synchronization signal, the transmitting ground machine sends a notification to stop transmitting electromagnetic waves to the transmitter downhole instrument, and sends a notification to stop receiving electromagnetic waves to the receiving ground machine, so that under the control of the receiving synchronization signal, the receiving ground machine sends the notification to stop receiving electromagnetic waves to the receiver downhole instrument.

5. The calculation method according to any one of claims 1 to 3, characterized in that, At the same time of uploading the initial amplitude and phase, the depth count, the transmitting and receiving sequence number are also transmitted to the receiving ground machine.

6. The calculation method according to any one of claims 1-3, characterized in that, The stored waveform data of the electromagnetic wave signal includes control header information and electromagnetic wave data, wherein the control header information includes transmission control and reception control, the transmission control includes but is not limited to the sequence number of the transmission synchronization signal, the sequence number of the transmission cycle and the transmission depth count, the reception control includes but is not limited to the reception depth count, the oversampling count and the sampling number, and the electromagnetic wave data includes the original waveform sequence data of the digitized current electromagnetic wave signal.

7. The calculation method according to any one of claims 1 to 3, characterized in that, The fixed time interval corresponds to 2 n times the synchronization signal period, both the electromagnetic transmitter and the electromagnetic receiver select the slave mode for independent synchronization.

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