WO2022126716A1 - 一种随钻测量***的同步方法 - Google Patents

一种随钻测量***的同步方法 Download PDF

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Publication number
WO2022126716A1
WO2022126716A1 PCT/CN2020/139834 CN2020139834W WO2022126716A1 WO 2022126716 A1 WO2022126716 A1 WO 2022126716A1 CN 2020139834 W CN2020139834 W CN 2020139834W WO 2022126716 A1 WO2022126716 A1 WO 2022126716A1
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Prior art keywords
synchronization
training sequence
waveform
uphole
modulated
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PCT/CN2020/139834
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English (en)
French (fr)
Inventor
欧晶
杜建生
洪林峰
何新振
李小龙
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中国科学院地质与地球物理研究所
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Priority to US18/035,294 priority Critical patent/US20230407742A1/en
Publication of WO2022126716A1 publication Critical patent/WO2022126716A1/zh

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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00—Survey of boreholes or wells
    • E21B47/12—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling
    • E21B47/14—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling using acoustic waves
    • E21B47/18—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling using acoustic waves through the well fluid, e.g. mud pressure pulse telemetry
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00—Survey of boreholes or wells
    • E21B47/12—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling
    • E21B47/14—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling using acoustic waves
    • E21B47/18—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling using acoustic waves through the well fluid, e.g. mud pressure pulse telemetry
    • E21B47/20—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling using acoustic waves through the well fluid, e.g. mud pressure pulse telemetry by modulation of mud waves, e.g. by continuous modulation
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00—Survey of boreholes or wells
    • E21B47/12—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling

Definitions

  • the invention relates to the technical field of measurement while drilling, in particular to a synchronization method of a measurement while drilling system.
  • the real-time logging information such as orientation, formation characteristics and drilling parameters required to be transmitted by the MWD (Measure While Drilling) system has shown an explosive growth.
  • the transmission rate has become a bottleneck restricting the development of MWD while drilling.
  • the technology of using shear valve to realize continuous wave of mud has appeared, which improves the data transmission rate of MWD system, and gradually becomes a very promising technology.
  • the MWD mud continuous wave system while drilling realizes the interception effect on the mud through the continuous motion of the motor rotor, forming a continuous pressure wave.
  • the swing frequency of the rotor of the motor rotary valve can reach 40Hz, and various modulation methods such as OOK, FSK, PSK are used for carrier modulation, so that the transmission rate can reach 40bps.
  • the MWD mud continuous wave system can better meet the growing demand for downhole data transmission. Further, downhole image transmission can be realized in combination with technologies such as compression coding.
  • the MWD mud continuous wave system is synchronized by inserting a fixed synchronization training code word at the beginning of the data frame at the downhole transmitting end, and finding the peak of the correlation result between the received waveform and the local waveform of the synchronization training sequence at the receiving end.
  • the purpose of the present invention is to provide a method for synchronizing a measurement while drilling system, so as to solve the above-mentioned problems in the prior art, and can improve the synchronization accuracy, thereby reducing the bit error rate.
  • the present invention provides a method for synchronizing a measurement while drilling system, comprising the following steps:
  • the synchronization position is found from the peak of the correlation curve.
  • the synchronization training sequence is determined based on the frame structure of the data sent downhole, which specifically includes:
  • the first modulated synchronization training sequence is sent through a shear valve.
  • the above-mentioned signal is collected by the pressure sensor uphole and correlated with the second modulated local waveform of the synchronization sequence to obtain a correlation curve.
  • the synchronization training codeword modulated by FSK is sent downhole, and the local waveform modulated by OOK is used uphole.
  • the synchronization training codeword modulated by OOK is sent downhole, and the local waveform modulated by FSK is used uphole.
  • the synchronization method of the measurement-while-drilling system as described above, wherein, preferably, the finding of the synchronization position according to the peak value of the correlation curve specifically includes:
  • the peak position in the correlation curve is taken as the synchronization output result.
  • the Methods also include:
  • the invention provides a synchronization method for a measurement while drilling system, constructs a synchronization training sequence, and proposes an improvement on the synchronization method of the FSK system based on the synchronization sequence; completes the uphole and downhole synchronization of the FSK system, so that the correlation peak value of the correlation curve increases, The gap between the main peak value and the secondary peak value increases; the present invention improves the synchronization accuracy and reliability of the MWD system without increasing the complexity of the motor control of the MWD system; at the same time, the synchronization training sequence can also be used as a fixed code for the equalizer to learn word usage.
  • FIG. 1 is a flowchart of an embodiment of a synchronization method for a measurement while drilling system provided by the present invention
  • Fig. 2 is the time domain waveform of the synchronous training sequence modulated by FSK, wherein, 10Hz represents the "0" codeword, and 20Hz represents the "1" codeword;
  • Figure 3 is a comparison of the correlation curves of the local synchronous training sequence waveforms of the OOK modulation system and the FSK modulation system with the same modulated local waveform when there is no noise;
  • Fig. 4 is the signal-to-noise ratio of 1dB
  • this synchronous training sequence waveform of OOK modulation system, FSK modulation system compares with the local waveform correlation curve through the same modulation;
  • Fig. 5 is the time domain waveform of the synchronous training sequence modulated by FSK, wherein, 20Hz represents the "0" codeword, and 10Hz represents the "1" codeword;
  • Fig. 6 is the curve comparison of the waveform of the training sequence modulated by FSK and the local waveform of the synchronous training sequence modulated by OOK and FSK when there is no noise;
  • Fig. 7 is the curve comparison between the waveform of the training sequence modulated by FSK and the local waveform of the synchronous training sequence modulated by OOK and FSK when the signal-to-noise ratio is 1dB.
  • first”, “second”: and similar terms do not denote any order, quantity, or importance, but are merely used to distinguish the different parts.
  • “Comprising” or “comprising” and similar words mean that the element preceding the word covers the elements listed after the word, and does not exclude the possibility that other elements are also covered.
  • “Up”, “down”, etc. are only used to indicate the relative positional relationship, and when the absolute position of the described object changes, the relative positional relationship may also change accordingly.
  • the synchronization method of the measurement-while-drilling system specifically includes the following steps in the actual execution process:
  • Step S1 Determine a synchronization training sequence based on the frame structure of the data sent downhole.
  • the step S1 may specifically include:
  • Step S11 Determine the frame structure of the data sent downhole.
  • Step S12 Determine a synchronization training sequence according to the frame structure of the transmitted data.
  • the synchronization training sequence in order to meet the requirement of high synchronization accuracy, it is necessary to make the synchronization training sequence have good autocorrelation characteristics, that is, the correlation peak in the correlation curve is sharp, which reflects the high synchronization accuracy of the synchronization training sequence;
  • the requirement of strong interference capability requires that the secondary peak interference in the correlation curve of the synchronous training sequence is low, that is, the secondary peak amplitude is much smaller than the main peak and the distance from the main peak is far away. This characteristic reflects the strong anti-interference ability of the synchronous training sequence.
  • Step S13 Send the first modulated synchronization training sequence through the shear valve.
  • the synchronization training sequence may be specifically subjected to FSK (Frequency-shift keying, frequency shift keying) modulation, ASK (Amplitude-Shift Keying, amplitude shift keying) modulation or PSK (Phase-shift keying, phase shift keying) modulation.
  • FSK Frequency-shift keying, frequency shift keying
  • ASK Amplitude-Shift Keying, amplitude shift keying
  • PSK Phase shift keying
  • OOK On-OffKeying, on-off keying
  • commonly used synchronization training codewords include m-sequence, M-sequence and Gold sequence.
  • the time domain waveform of the synchronization training sequence designed by the present invention is FSK modulated as shown in Figure 2, wherein the carrier frequency is 10Hz and 20Hz, the sampling frequency is 1KHz, the data rate is 10bps, and the start position of the synchronization sequence is 1.5s (No. 1501). sampling points).
  • the synchronization training sequence is respectively calculated in the OOK modulation system and the FSK modulation system, and the first correlation curve (curve 1) and the second correlation curve (curve 2) are obtained respectively as shown in Figure 3 shown.
  • the FSK modulation system will be erroneously synchronized to the sub-peak value of the correlation curve, resulting in the system erroneously synchronizing 0.5 symbol period, resulting in an increase in the bit error rate of the entire data frame.
  • the synchronization performance of the synchronization training sequence in the OOK modulation system is better than that in the FSK modulation system: the correlation peak is sharper, that is, the synchronization performance of the synchronization training sequence in the OOK modulation system is better; The peak interference is low, that is, the anti-interference performance of the synchronization training sequence in the OOK modulation system is better.
  • white Gaussian noise is added to the OOK modulation system and the FSK modulation system.
  • the channel conditions are poor; at the same time, with the increase of the well depth, the attenuation of the mud continuous wave increases.
  • the above two factors cause the signal-to-noise ratio of the useful signal received on the ground to be very low, about 1dB.
  • the main peak value of the correlation curve of the synchronization training sequence in the OOK modulation system is still higher than the main peak value of the correlation curve in the FSK modulation system.
  • the synchronous sampling point output of the synchronous training sequence in the OOK modulation system is 1501
  • the synchronous sampling point output in the FSK modulation system is 1554
  • the errors are 0 sampling points and 53, ie, 0ms and 53ms, respectively.
  • the FSK modulation system will be erroneously synchronized to the sub-peak value of the correlation curve, resulting in the system erroneously synchronizing 0.5 symbol period, resulting in an increase in the bit error rate of the entire data frame.
  • the synchronization performance of the synchronization training sequence in the OOK modulation system is better than that in the FSK modulation system: the correlation peak is sharper, that is, the synchronization training sequence is in the OOK modulation system.
  • the synchronization performance is better; the secondary peak interference is low, that is, the anti-interference performance of the synchronization training sequence in the OOK modulation system is better.
  • Step S2 using the irrelevance of trigonometric functions to construct the correspondence between the waveform of the synchronous training sequence sent downhole and the local waveform of the synchronous training sequence uphole.
  • the present invention proposes to adopt OOK modulation in the MWD mud continuous wave system based on FSK modulation.
  • the training sequence is used as a transmit waveform or a locally synchronized waveform.
  • step S3 based on the orthogonality of the above trigonometric functions, there are two technical solutions in step S3.
  • the synchronization training codewords that have passed through the FSK modulation system are sent downhole, and the OOK modulation system is used uphole. local waveform.
  • the synchronous training codeword passed through the OOK modulation system is sent downhole, and the local waveform of the FSK modulation system is used uphole.
  • the present invention needs to design the carrier frequency of the "1" codeword modulated by FSK downhole and the carrier frequency of the "1" codeword of local synchronization training by OOK modulation uphole, or the "0" codeword is in The carrier frequency of downhole and uphole is the same.
  • the present invention adopts the function of The synchronization training codeword waveform modulated by FSK is sent downhole, and the local waveform modulated by OOK is used uphole for synchronization.
  • Step S3 Perform correlation calculation between the first modulated synchronous training codeword waveform received uphole and the second modulated synchronous training sequence waveform to obtain a correlation curve.
  • correlation calculation is performed on the wellbore between the received first modulated signal waveform and the second modulated local waveform of the synchronous training sequence to obtain a correlation curve.
  • the present invention greatly improves the synchronization precision of the FSK modulation-based MWD system while drilling, thereby solving the problem of the increase of the bit error rate caused by synchronization in the original system.
  • the present invention greatly improves the synchronization accuracy of the FSK modulation-based MWD system while drilling, thereby solving the problem of increasing the bit error rate caused by synchronization in the original system.
  • Step S4 Find the synchronization position according to the peak value of the correlation curve.
  • the peak position in the correlation curve is used as the synchronization output result.
  • the sampling point corresponding to the maximum amplitude value of the curve 1 in Figure 3 is calculated as the synchronization point when no noise; the sampling point corresponding to the maximum amplitude value of the curve 3 in Figure 4 is calculated as the synchronization point when the signal-to-noise ratio is 1dB. .
  • the generation of new waveforms should be avoided as much as possible, so as not to increase the difficulty of motor control of the MWD system while drilling.
  • the synchronization training codewords through the OOK modulation system are sent downhole, and the local waveforms of the FSK modulation system are used uphole; or the synchronization training code words through the FSK modulation system are sent downhole
  • the training codewords use the local waveform of the OOK modulation system in the well.
  • the present invention also uses the synchronization training sequence as a fixed code learned by the equalizer. word usage.
  • the shear valve Downhole, the shear valve sends an FSK-modulated synchronous training sequence waveform.
  • the local waveform of the synchronous training sequence modulated by OOK is used to perform the correlation operation on the received waveform of the synchronous training sequence modulated by FSK.
  • the present invention still retains the excellent synchronization performance of the synchronization training sequence under local OOK modulation, that is, the correlation peak is sharp and the secondary peak interference is low.
  • the invention improves the synchronization precision and the synchronization anti-interference performance.
  • the synchronization method of the MWD system improves the synchronization accuracy and the synchronization anti-interference performance, and solves the error caused by the poor synchronization accuracy of the MWD mud continuous wave FSK modulation system.
  • the invention supports the function of synchronous training sequence as a fixed code word learned by the equalizer, which saves the transmission resources of the MWD mud continuous wave system;
  • the synchronization training sequence is suitable for both OOK and FSK modulation systems.
  • the method further includes the steps of downhole coding and modulation, attenuation and interference of useful signals by mud continuous wave channel, uphole denoising, and uphole matched filtering performed in sequence.
  • the MWD mud continuous wave system is mainly composed of continuous wave generator, motor drive circuit, attitude measurement probe, downhole central control unit and power supply; It is composed of modules such as code unit and control unit.
  • the downhole part controls the mud (drilling fluid) pressure to generate the expected waveform, and the waveform is transmitted to the uphole through the mud.
  • the waveform received by the sensor is processed, decoded and restored to the data on the wellbore. This process can be simplified as the MWD mud continuous wave system while drilling. communication model.
  • the downhole part of the MWD mud continuous wave system will control the motor to rotate the rotor according to the coding method, frame structure, modulation method, data rate, etc.
  • the mud flow rate changes regularly, and finally reflects the change of the mud pressure wave.
  • the synchronization training codeword in the frame structure can adopt FSK modulation or OOK modulation.
  • the synchronization training codeword based on FSK modulation is sent downhole.
  • the attenuation of the useful signal amplitude increases, and the fading belongs to frequency selective fading.
  • the channel fading is related to the elastic properties of the drill pipe, the friction between particles in the mud, and the compressibility of the mud. Affected by channel fading, the useful signal received by the pressure sensor on the well will be distorted, which needs to be eliminated by means of equalization on the well.
  • the MWD system while drilling is mainly affected by the interference of pump noise, drill bit reflection, motor noise, etc. It is necessary to perform digital signal processing on the well to reduce the influence of the interference on the decoding of the useful signal, so that the downhole data can be obtained correctly.
  • the MWD system uses the data signal processing technology to process the mud pressure wave signal collected by the sensor to eliminate the influence of pump noise and motor noise on the system.
  • a noise canceling method is adopted in which an analog pump noise waveform is generated by learning the pump noise period by the pump impulse sensor, and the analog pump noise waveform is subtracted from the received waveform.
  • the matched filtering is divided into two channels.
  • the first channel processes the data according to the waveform of the first local carrier frequency 1
  • the second channel processes the data according to the waveform of the second local carrier frequency. After processing, the output waveforms are superimposed to obtain the final result.
  • the step of uphole synchronization is performed, and the de-noised data is subjected to correlation processing through the local waveform of the synchronization training sequence (refer to the foregoing steps S1 to S3 for details).
  • the synchronization training codeword using FSK modulation Inoue adopts the local waveform of the synchronization training sequence modulated by OOK; when sending the synchronization training codeword using OOK modulation, Inoue adopts the local waveform of the synchronization training sequence modulated by FSK waveform.
  • the method further includes: performing uphole equalization and uphole solution sequentially. Tuning and decoding steps.
  • the equalizer is trained by using the fixed codeword, and the equalization coefficients are obtained, which are used for decoding the data frame.
  • the equalizer can be implemented by using a filter, and by adjusting the parameters of the filter, the characteristics (including but not limited to time domain characteristics, frequency domain characteristics, etc.) generated by the channel are corrected and compensated, thereby reducing inter-symbol crosstalk.
  • a linear equalizer or a nonlinear equalizer can be used.
  • This embodiment is implemented by a decision feedback equalizer, and the coefficients of the decision feedback equalizer are adjusted by an RLS (Recursive Least Squares, recursive least squares) or LMS (Least Mean Squares, least mean squares) algorithm to achieve adaptive equalization.
  • RLS Recursive Least Squares, recursive least squares
  • LMS Least Mean Squares, least mean squares
  • the synchronous training code word can be used for equalizer training.
  • the FSK synchronous training code word needs to be sent downhole, and the local waveform of the OOK modulation synchronization training sequence is used uphole for synchronization.
  • the synchronization method of the MWD system constructs a synchronization training sequence, and based on the synchronization sequence, a synchronization method that is compatible with the modulation process of the FSK system and the OOK system is proposed;
  • the corresponding relationship between the waveform of the synchronization training sequence sent downhole and the local waveform of the synchronization training sequence uphole, completes the uphole and downhole synchronization of the FSK system, so that the correlation peak value of the synchronization training sequence is increased, and the gap between the main peak and the sub-peak value is increased;
  • the present invention does not increase the Under the premise of the complexity of the motor control of the MWD system, the synchronization accuracy and reliability of the MWD system are improved; at the same time, the synchronization training sequence can also be used for the equalizer training of the MWD mud continuous wave system, thereby saving the transmission resources of the system.

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Abstract

本发明公开了一种随钻测量***的同步方法，所述方法包括：基于井下发送数据的帧结构，确定同步训练序列；利用三角函数的不相关性，构造井下发送同步训练序列波形和井上同步训练序列本地波形的对应关系；将井上接收到的经过第一调制的同步训练码字波形与经过第二调制的所述同步训练序列本地波形进行相关计算，得到相关曲线并通过相关曲线找到同步位置。本发明提供的随钻测量***的同步方法，构造了同步训练序列，基于该同步序列提出了对FSK***同步方法的改进；完成对FSK***的井上、井下同步，使得相关曲线相关峰值增高、主峰值和次峰值差距增大；在不增加MWD***电机控制复杂性的前提下，提高了MWD***的同步精度和可靠性。

Description

一种随钻测量***的同步方法 技术领域
本发明涉及随钻测量技术领域，尤其涉及一种随钻测量***的同步方法。
背景技术
近年来，为了进一步提高钻井效率，MWD(Measure While Drilling，随钻测量)***所需传输的定向、地层特性和钻井参数等实时测井信息呈现***式增长，传统正、负脉冲传输***的低传输速率已成为制约随钻MWD发展的瓶颈问题。为了满足日益增加的信息量的需求，出现了利用剪切阀实现泥浆连续波的技术，提高了MWD***的数据传输速率，并逐渐成为一种很有前景的技术。
随钻MWD泥浆连续波***通过电机转子的连续运动实现对泥浆的截流效果，形成连续压力波。电机旋转阀转子的摆动频率可以达到40Hz，并运用OOK、FSK、PSK等各种调制方式进行载波调制，从而可实现传输速率达到40bps。相比于正、负脉冲传输***的最大传输速率5bps，MWD泥浆连续波***更能满足日益增长的井下数据传输需求。进一步地，可结合压缩编码等技术实现井下图像传输。
在MWD泥浆连续波***中，如何精确同步是保障该***高速传输的重要技术之一。目前，MWD泥浆连续波***在井下发送端，通过在数据帧的开头处***固定的同步训练码字，并在接收端寻找接收波形和同步训练序列本地波形相关结果峰值实现同步。
在实际应用中，由于FSK调制的同步训练码字相关性差，从而导致了***的同步精度差、误码率高、抗噪能力差、传输深度浅等问题，上述缺点制约了基于FSK调制的随钻MWD泥浆连续波***的使用和发展。目前，该问题尚未有有效的解决方法。
因此，亟需一种随钻测量***的同步方法。
发明内容
本发明的目的是提供一种随钻测量***的同步方法，以解决上述现有技术中的问题，能够提高同步精度，从而降低误码率。
本发明提供了一种随钻测量***的同步方法，其中，包括以下步骤：
基于井下发送数据的帧结构，确定同步训练序列；
利用三角函数的不相关性，构造井下发送同步训练序列波形和井上同步训练序列本地波形的对应关系；
在井上将接收到的第一调制信号波形与经过第二调制的所述同步训练序列本地波形进行相关计算，得到相关曲线；
根据所述相关曲线的峰值找到同步位置。
如上所述的随钻测量***的同步方法，其中，优选的是，所述基于井下发送数据的帧结构，确定同步训练序列，具体包括：
确定井下发送数据的帧结构；
根据所述发送数据的帧结构确定同步训练序列；
通过剪切阀发送经过第一调制的所述同步训练序列。
如上所述的随钻测量***的同步方法，其中，优选的是，所述在井上将接收到的经过第一调制信号波形与经过第二调制的所述同步训练序列本地波形进行相关计算，得到相关曲线，具体包括：
通过剪切阀发送经过第一调制的所述同步序列；
井上通过压力传感器采集上述信号并将其与第二调制的所述同步序列本地波形进行相关计算，得到相关曲线。
如上所述的随钻测量***的同步方法，其中，优选的是，所述利用三角函数的不相关性，构造井下发送同步训练序列波形和井上同步训练序列本地波形的对应关系，具体包括：
在井下发送经过FSK调制的同步训练码字，在井上采用OOK调制的本地波形。
如上所述的随钻测量***的同步方法，其中，优选的是，所述利用三角函数的不相关性，构造井下发送同步训练序列波形和井上同步训练序列本地波形的对应关系，具体包括：
在井下发送经过OOK调制的同步训练码字，在井上采用FSK调制的本地波形。
如上所述的随钻测量***的同步方法，其中，优选的是，所述根据所述相关曲线的峰值找到同步位置，具体包括：
将所述相关曲线中的峰值位置作为同步输出结果。
如上所述的随钻测量***的同步方法，其中，优选的是，在同步之前，所述方法还包括：
依次实施的井下编码与调制、泥浆连续波信道对有用信号产生衰减和干扰、井上消噪、井上匹配滤波的步骤。
如上所述的随钻测量***的同步方法，其中，优选的是，在所述利用三角函数的不相关性，构造井下发送同步训练序列波形和井上同步训练序列本地波形的对应关系之后，所述方法还包括：
依次实施的井上均衡、井上解调与解码的步骤。
本发明提供一种随钻测量***的同步方法，构造了同步训练序列，基于该同步序列提出了对FSK***同步方法的改进；完成对FSK***的井上、井下同步，使得相关曲线相关峰值增高、主峰值和次峰值差距增大；本发明在不增加MWD***电机控制复杂性的前提下，提高了MWD***的同步精度和可靠性；同时所述同步训练序列还可作为均衡器学习的固定码字使用。
附图说明
为使本发明的目的、技术方案和优点更加清楚，下面将结合附图对本发明作进一步描述，其中：
图1为本发明提供的随钻测量***的同步方法的实施例的流程图；
图2为经FSK调制的同步训练序列时域波形，其中，10Hz代表“0”码字，20Hz代表“1”码字；
图3为无噪声时，OOK调制***、FSK调制***的本同步训练序列波形与经相同调制的本地波形相关曲线比较；
图4为信噪比1dB时，OOK调制***、FSK调制***的本同步训练序 列波形与经相同调制的本地波形相关曲线比较；
图5为经FSK调制的同步训练序列的时域波形，其中，20Hz代表“0”码字，10Hz代表“1”码字；
图6为无噪声时，FSK调制的训练序列波形分别与经OOK调制、FSK调制的同步训练序列本地波形相关的曲线比较；
图7为信噪比1dB时，FSK调制的训练序列波形分别与经OOK调制、FSK调制的同步训练序列本地波形相关的曲线比较。
具体实施方式
现在将参照附图来详细描述本公开的各种示例性实施例。对示例性实施例的描述仅仅是说明性的，决不作为对本公开及其应用或使用的任何限制。本公开可以以许多不同的形式实现，不限于这里所述的实施例。提供这些实施例是为了使本公开透彻且完整，并且向本领域技术人员充分表达本公开的范围。应注意到：除非另外具体说明，否则在这些实施例中阐述的部件和步骤的相对布置、材料的组分、数字表达式和数值应被解释为仅仅是示例性的，而不是作为限制。
本公开中使用的“第一”、“第二”：以及类似的词语并不表示任何顺序、数量或者重要性，而只是用来区分不同的部分。“包括”或者“包含”等类似的词语意指在该词前的要素涵盖在该词后列举的要素，并不排除也涵盖其他要素的可能。“上”、“下”等仅用于表示相对位置关系，当被描述对象的绝对位置改变后，则该相对位置关系也可能相应地改变。
本公开使用的所有术语(包括技术术语或者科学术语)与本公开所属领域的普通技术人员理解的含义相同，除非另外特别定义。还应当理解，在诸如通用字典中定义的术语应当被解释为具有与它们在相关技术的上下文中的含义相一致的含义，而不应用理想化或极度形式化的意义来解释，除非这里明确地这样定义。
对于相关领域普通技术人员已知的技术、方法和设备可能不作详细讨论，但在适当情况下，技术、方法和设备应当被视为说明书的一部分。
如图1所示，本实施例提供的随钻测量***的同步方法在实际执行过 程中，具体包括如下步骤：
步骤S1、基于井下发送数据的帧结构，确定同步训练序列。
其中，基于井下发送数据的帧结构，确定经过第一调制的同步训练序列。在本发明的随钻测量***的同步方法的一种实施方式中，所述步骤S1具体可以包括：
步骤S11、确定井下发送数据的帧结构。
步骤S12、根据所述发送数据的帧结构确定同步训练序列。
具体地，为了满足同步精度高的要求，需要使同步训练序列具有良好的自相关特性，即相关曲线中的相关峰值尖锐，该特性反应了同步训练序列的同步精度高；进一步地，为了满足抗干扰能力强的要求，需要使同步训练序列的相关曲线中的副峰值干扰低，即副峰值幅值远小于主峰值且距主峰值距离远，该特性反应了同步训练序列的抗干扰能力强。
步骤S13、通过剪切阀发送经过第一调制的所述同步训练序列。
同步训练序列具体可以经过FSK(Frequency-shift keying，频移键控)调制或ASK(Amplitude-Shift Keying，幅移键控)调制或PSK(Phase-shift keying，相移键控)调制。目前，由于在石油钻井领域中，信号传输距离长，信号幅度衰减大，ASK调制普遍采用OOK(On-OffKeying，开关键控)调制。目前，常用的同步训练码字有m序列、M序列和Gold序列等。但现***字在基于FSK调制的MWD***中的同步性能差：在信噪比低时易发生误同步，从而导致解码失败。本发明设计的同步训练序列经FSK调制的时域波形见图2所示，其中载波频率为10Hz和20Hz，采样频率为1KHz，数据速率为10bps，同步序列起始位置为1.5s处(第1501个采样点)。
具体地，在没有噪声时，在OOK调制***和FSK调制***中分别对所述同步训练序列进行相关计算，分别得到第一相关曲线(曲线1)和第二相关曲线(曲线2)如图3所示。
从图3中可知，当没有噪声时，所述同步训练序列在OOK调制***中的相关曲线主峰值比在FSK调制***中的相关曲线峰值高了约4.9dB，同时次峰值与主峰值幅值相差更大、距离更远。此时，所述同步训练序列在OOK调制***中的同步采样点输出为1501，在FSK调制***中的的同步 采样点输出为1552，误差分别为0个采样点和51个，即0ms和51ms。此时，FSK调制***会误同步到相关曲线的次峰值上，导致***误同步0.5个码元周期，从而导致整个数据帧误码率提高。
综上，所述同步训练序列在OOK调制***中的同步性能优于在FSK调制***中的同步性能：相关峰值更加尖锐，即所述同步训练序列在OOK调制***中的同步性能更好；副峰值干扰低，即所述同步训练序列在OOK调制***中的抗干扰性能更好。
进一步地，对所述OOK调制***和FSK调制***加入高斯白噪声。
由于泥浆信道受到泵噪、马达噪声、振动噪声等影响，信道条件恶劣；同时，随着井深的增加，泥浆连续波的衰减增大。上述两种因素导致地面接收到的有用信号信噪比很低，约为1dB左右。
对所述OOK调制***和FSK调制***加入高斯白噪声，并分别对所述同步训练序列进行相关计算，得到第三相关曲线(曲线4)和第四相关曲线(曲线5)如图4所示。
从图4可知，所述同步训练序列在OOK调制***中的相关曲线的主峰值依旧高于在FSK调制***中的相关曲线主峰值。所述同步训练序列在OOK调制***中的同步采样点输出为1501，在FSK调制***中的同步采样点输出为1554，误差分别为0个采样点和53个，即0ms和53ms。此时，FSK调制***会误同步到相关曲线的次峰值上，导致***误同步0.5个码元周期，从而导致整个数据帧误码率提高。
综上，信噪比为1dB时，所述同步训练序列在OOK调制***中的同步性能优于在FSK调制***中的同步性能：相关峰值更加尖锐，即所述同步训练序列在OOK调制***中的同步性能更好；副峰值干扰低，即所述同步训练序列在OOK调制***中的抗干扰性能更好。
步骤S2、利用三角函数的不相关性，构造井下发送同步训练序列波形和井上同步训练序列本地波形的对应关系。
为了解决FSK调制***中同步训练序列同步精度差导致的误码率高、抗噪能力差、传输深度浅等问题，本发明提出在基于FSK调制的MWD泥浆连续波***中，采用OOK调制的同步训练序列作为发送波形或者本地同 步波形。
利用三角函数
Figure PCTCN2020139834-appb-000001
的正交性可得：
∫cos(2πlf ct)×cos(2πmf ct)dt＝0,l≠m,l∈N,m∈N    (1)
其中，f c表示载波频率，特别地，当l＝0时，
∫1×cos(2πmf ct)dt＝0,m∈N +     (2)
由三角函数的上述性质可知，以正弦波作为载波信号时，载波频率f c的各个倍频是不相关的。因此，在相关算法中，频率等于0和频率等于n×f c,n≠1是等价的，都与频率等于f c的信号互不相关。同时频率等于0和频率等于n×f c,n≠1的信号互不相关。
具体而言，基于上述三角函数的正交性，步骤S3有两种技术方案，本发明在一种实现方式中，在井下发送经过FSK调制***的同步训练码字，在井上采用OOK调制***的本地波形。本发明在另一种实现方式中，在井下发送经过OOK调制***的同步训练码字，在井上采用FSK调制***的本地波形。
为了满足正交性，本发明需要设计井下经FSK调制的“1”码字的载波频率和井上经OOK调制的本地同步训练的“1”码字的载波频率相同，或者“0”码字在井下、井上的载波频率相同。
具体而言，以前者为例，井下发生FSK调制波形时，用20Hz代表“0”码字，10Hz代表“1”码字，见图5所示。井上经OOK调制的同步训练序列用0Hz代表“0”码字，10Hz代表“1”码字。此时井上、井下的“1”码字波形相同，而“0”码字与“1”码字都正交，同时彼此正交。
在具体实现中，为解决FSK***同步训练码字同步性能差的问题，同时保证不增加电机控制复杂度和所述同步训练序列可作为均衡器学习的固定码字使用的功能，本发明采用在井下发送经过FSK调制的同步训练码字波形、在井上使用OOK调制的本地波形进行同步。
步骤S3、将井上接收到的经过第一调制的同步训练码字波形与经过第二调制的所述同步训练序列波形进行相关计算，得到相关曲线。
在具体实现中，在井上将接收的第一调制信号波形与经过第二调制的所述同步训练序列本地波形进行相关计算，得到相关曲线。
从图6中可知，当没有噪声、井下发送FSK调制的同步训练序列波形时，井上采用OOK调制波形作为本地波形时的相关曲线(曲线5)的主峰值比井上采用FSK调制波形作为本地波形时的相关曲线(曲线6)高了约5.9dB。此时，前者的同步采样点输出为1501，后者的同步采样点输出为1650，误差分别为0个采样点和149个，即0ms和149ms。此时，采用FSK调制的同步训练序列本地波形会误同步到相关曲线的次峰值上，导致同步误差为1.5个码元周期，从而导致整个数据帧误码率增加。因此本发明大幅提高了基于FSK调制的随钻MWD***的同步精度，从而解决了原***中因同步导致的误码率升高的问题。
从图7中可知，对井下发送的FSK调制的同步训练序列波形加入高斯白噪声，信噪比为1dB时，井上采用OOK调制波形作为本地波形时的相关曲线(曲线7)的主峰值尖锐，而井上采用FSK调制波形作为本地波形时的相关曲线(曲线8)无明显峰值。此时，前者的同步采样点输出为1503，后者的同步采样点输出为1457，误差分别为2个采样点和44个采样点，即2ms和43ms。此时，采用FSK调制的同步训练序列本地波形会误同步到相关曲线的次峰值上，导致同步误差为0.5个码元周期，从而导致整个数据帧误码率增加。因此，在实际应用中，本发明大幅提高了基于FSK调制的随钻MWD***的同步精度，从而解决了原***中因同步导致的误码率升高的问题。
步骤S4、根据所述相关曲线的峰值找到同步位置。
具体地，将所述相关曲线中的峰值位置作为同步输出结果。在具体实现中，计算图3中曲线1的幅度最大值对应的采样点作为无噪声时的同步点；计算图4中曲线3的幅度最大值对应的采样点作为信噪比1dB时的同步点。
进一步地，考虑到井下工况复杂，应尽量避免产生新的波形，以免增加随钻MWD***电机控制难度。本发明在具体实现中，为了避免产生新的波形，在井下均发送经过OOK调制***的同步训练码字，在井上均采用FSK调制***的本地波形；或者在井下均发送经过FSK调制***的同步训练码字，在井上均采用OOK调制***的本地波形。
更进一步地，在随钻MWD泥浆连续波***中，由于数据传输速率低(最大数据速率为40bps，常采用12bps)，为了节约传输资源，本发明将同步训练序列也作为均衡器学习的固定码字使用。
为了满足上述降低电机控制难度以及节约传输资源的两个需求，采用发送FSK调制的同步训练码字、同步采用OOK调制的本地波形的效果更佳，即在井下发送经过FSK调制的同步训练码字波形，在井上采用OOK调制的本地波形进行同步。
在井下，剪切阀发送经过FSK调制的同步训练序列波形。在井上，采用经OOK调制的同步训练序列本地波形对接收到的经FSK调制的同步训练序列波形进行相关运算。根据三角函数的正交性可知，本发明依旧保留了本地OOK调制下同步训练序列优异的同步性能即：相关峰值尖锐；副峰值干扰低。对比于原有FSK调制***，本发明提高了同步精度和同步抗干扰性能。
本发明实施例提供的随钻测量***的同步方法，与原有FSK调制***相比，提高了同步精度和同步抗干扰性能，解决了MWD泥浆连续波FSK调制***因同步精度差而导致的误码问题；此外，不会增加井下电机控制难度；同时，本发明支持同步训练序列作为均衡器学习的固定码字这一功能，节约了MWD泥浆连续波***的传输资源；而且，本发明所涉及的同步训练序列同时适用于OOK和FSK两种调制***，当发送同步训练码字采用FSK调制时，井上采用经OOK调制的同步训练码字本地波形；当发送同步训练码字采用OOK调制时，井上采用经FSK调制的同步训练序列本地波形。
进一步地，在同步之前，所述方法还包括：依次实施的井下编码与调制、泥浆连续波信道对有用信号进行衰减和干扰、井上消噪、井上匹配滤波的步骤。
在井下，MWD泥浆连续波***主要由连续波发生器、电机驱动电路、姿态测量探管、井下中控单元和电源等模块组成；在井上，该***主要由地面传感器、地面数据处理单元、译码单元和控制单元等模块组成。井下部分控制泥浆(钻井液)压力生成预期波形，该波形通过泥浆传输至井上， 井上对传感器收到的波形进行数据处理、译码还原至数据，该过程可简化为随钻MWD泥浆连续波***通信模型。
具体地，在井下编码与调制过程中，MWD泥浆连续波***的井下部分会按照协议的编码方式、帧结构、调制方式、数据速率等约定控制电机使转子进行旋转，从而在转子和定子之间的泥浆流量产生规律变化，最终反应到泥浆压力波的变化。在本发明中，帧结构中的同步训练码字可采用FSK调制，也可采用OOK调制。在本实施例中，采用井下发送基于FSK调制的同步训练码字。
在泥浆连续波信道对有用信号进行衰减和干扰的过程中，在随钻MWD***中，随着井深的增加，有用信号幅度的衰减增大，该衰落属于频率选择性衰落。信道衰落和钻杆的弹性性质、泥浆中颗粒间的摩擦、泥浆的压缩系数等有关。受到信道衰落的影响，井上压力传感器收到的有用信号会产生畸变，需要在井上通过均衡等手段消除。随钻MWD***主要受到泵噪、钻头反射、马达噪声等干扰的影响，需要在井上进行数字信号处理以降低干扰对有用信号译码的影响，从而正确得到井下数据。
在井上消噪的过程中，在井上，MWD***采用数据信号处理的技术对传感器采集的泥浆压力波信号进行处理，以消除泵噪和马达噪声对***的影响。在本实施例中，采用通过泵冲传感器学习泵噪周期生成模拟泵噪波形并在接收波形减去该模拟泵噪波形的消噪方式。
在井上匹配滤波的过程中，匹配滤波分为两个通道进行，第一个通道按照第一本地载波频率1的波形对数据进行处理，第二个通道按照第二本地载波频率的波形对数据进行处理，再将输出波形进行叠加，得到最终结果。
在井上匹配滤波的步骤之后，执行井上同步步骤，将消噪后的数据通同步训练序列本地波形进行相关处理(具体参照前文步骤S1-步骤S3)。在本实施例中，当发送同步训练码字采用FSK调制时，井上采用经OOK调制的同步训练序列本地波形；当发送同步训练码字采用OOK调制时，井上采用经FSK调制的同步训练序列本地波形。
更进一步地，在所述利用三角函数的不相关性，构造井下发送同步训 练序列波形和井上同步训练序列本地波形的对应关系并同步之后，所述方法还包括：依次实施的井上均衡、井上解调与解码的步骤。
在井上均衡的过程中，利用固定码字对均衡器进行训练，得到均衡系数，供数据帧解码使用。均衡器可采用滤波器来实现，通过调整滤波器的参数，对信道产生的特性(包括但不限于时域特性、频域特性等)进行校正和补偿，从而减少码间串扰。具体可采用线性均衡器或非线性均衡器实现。本实施例采用判决反馈均衡器实现，并通过RLS(Recursive Least Squares,递推最小二乘)或LMS(Least Mean Squares，最小均方)算法调整判决反馈均衡器系数以实现自适应均衡。进一步地，为了提高随钻MWD***数据传输效率，可利用同步训练码字进行均衡器训练，此时，需要井下发送FSK同步训练码字，井上利用OOK调制同步训练序列本地波形进行同步。
在井上解调与解码的过程中，进行相干解调或非相干解调等方式解调，然后通过判决得到01码字，再按照协议约定的编码方式(例如可以包括：纠错编码、加校验位等)、帧结构组成得到对应的参数数值。本实施例采用相干解调、硬判决的译码方式。
本发明实施例提供的随钻测量***的同步方法，构造了同步训练序列，基于该同步序列提出了对FSK***和OOK***的调制过程进行兼容的同步方法；利用三角函数的不相关性，构造井下发送同步训练列波形和井上同步训练序列本地波形的对应关系，完成对FSK***的井上、井下同步，使得同步训练序列的相关峰值增高、主峰值和次峰值差距增大；本发明在不增加MWD***电机控制复杂性的前提下，提高了MWD***的同步精度和可靠性；同时，该同步训练序列也可用于MWD泥浆连续波***的均衡器训练，从而节约***的传输资源。
至此，已经详细描述了本公开的各实施例。为了避免遮蔽本公开的构思，没有描述本领域所公知的一些细节。本领域技术人员根据上面的描述，完全可以明白如何实施这里公开的技术方案。
虽然已经通过示例对本公开的一些特定实施例进行了详细说明，但是本领域的技术人员应该理解，以上示例仅是为了进行说明，而不是为了限 制本公开的范围。本领域的技术人员应该理解，可在不脱离本公开的范围和精神的情况下，对以上实施例进行修改或者对部分技术特征进行等同替换。本公开的范围由所附权利要求来限定。

Claims (8)

  1. 一种随钻测量***的同步方法，其特征在于，包括如下步骤：
    基于井下发送数据的帧结构，确定同步训练序列；
    利用三角函数的不相关性，构造井下发送同步训练序列波形和井上同步训练序列本地波形的对应关系；
    在井上将接收到的第一调制信号波形与经过第二调制的所述同步训练序列本地波形进行相关计算，得到相关曲线；
    根据所述相关曲线的峰值找到同步位置。
  2. 根据权利要求1所述的随钻测量***的同步方法，其特征在于，所述基于井下发送数据的帧结构，确定同步训练序列，具体包括：
    确定井下发送数据的帧结构；
    根据所述发送数据的帧结构确定同步训练序列；
    通过剪切阀发送经过第一调制的所述同步训练序列。
  3. 根据权利要求1所述的随钻测量***的同步方法，其特征在于，所述在井上将接收到的经过第一调制信号波形与经过第二调制的所述同步训练序列本地波形进行相关计算，得到相关曲线，具体包括：
    通过剪切阀发送经过第一调制的所述同步序列；
    井上通过压力传感器采集上述信号并将其与第二调制的所述同步序列本地波形进行相关计算，得到相关曲线。
  4. 根据权利要求1所述的随钻测量***的同步方法，其特征在于，所述利用三角函数的不相关性，构造井下发送同步训练序列波形和井上同步训练序列本地波形的对应关系，具体包括：
    在井下发送经过FSK调制的同步训练码字波形，在井上采用OOK调制的本地波形。
  5. 根据权利要求1所述的随钻测量***的同步方法，其特征在于，所述利用三角函数的不相关性，构造井下发送同步训练序列波形和井上同步训练序列本地波形的对应关系，具体包括：
    在井下发送经过OOK调制的同步训练码字波形，在井上采用FSK调制的本地波形。
  6. 根据权利要求1所述的随钻测量***的同步方法，其特征在于，所述根据所述相关曲线的峰值找到同步位置，具体包括：
    将所述相关曲线中的峰值位置作为同步输出结果。
  7. 根据权利要求1所述的随钻测量***的同步方法，其特征在于，在同步之前，所述方法还包括：
    依次实施的井下编码与调制、泥浆连续波信道对有用信号产生衰减和干扰、井上消噪、井上匹配滤波的步骤。
  8. 根据权利要求1所述的随钻测量***的同步方法，其特征在于，在所述利用三角函数的不相关性，构造井下发送同步训练序列波形和井上同步训练序列本地波形的对应关系之后，所述方法还包括：
    依次实施的井上均衡、井上解调与解码的步骤。
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