CN111308560B - Method and device for eliminating noise of MWD (measurement while drilling) system - Google Patents

Abstract

The invention discloses a method for eliminating noise of a MWD (measurement while drilling) system, which comprises the following steps: receiving an acquired mud signal and determining the characteristic frequency of a periodic noise signal in the mud signal; carrying out Fourier transform on the mud signals to obtain frequency domain mud signals; and obtaining a denoised mud frequency domain output signal according to the characteristic frequency of the periodic noise signal in the mud signal, the mud signal of the frequency domain and a preset suppression factor. By the scheme of the invention, the periodic noise of the MWD system during measurement while drilling is eliminated in the frequency domain.

Description

Method and device for eliminating noise of MWD (measurement while drilling) system

Technical Field

The invention relates to the field of well logging, in particular to a method and a device for eliminating noise of a MWD system during measurement while drilling.

Background

The logging-while-drilling system is used for measuring underground geological and engineering parameters in real time in the drilling process. The mud pulse while-drilling data demodulation system is used for transmitting the while-drilling logging data to the ground from the underground in real time. The transmission system utilizes the mud interception effect generated by the motion of the pulser to cause the pressure fluctuation of mud, and modulates the digital signal in the mud pressure wave to be transmitted to the ground, thereby realizing the real-time transmission of underground measurement data to the ground. The mud pulse while-drilling data transmission system comprises three main functional modules: the device comprises a mud pulse generating mechanism, a mud signal transmission channel and a pressure wave acquisition and demodulation system. The mud pulse generating mechanism is mainly a pulser which can be divided into three categories of positive pulse, negative pulse and continuous wave pulse, and the core principle is the interception effect on mud. The mud signal transmission channel comprises a whole drilling fluid circulation pipeline, a mud pump, a manifold, a vertical pipe, a hose and various joints through which mud flows upwards, a drill rod, various well logging instruments, a flow channel converter, a guide short joint, a drill bit, a bottom hole reflection surface and the like downwards, mud pressure waves are transmitted to the well from the underground through the mud channel, and meanwhile, the mud pressure waves are subjected to superposition noise or attenuation characteristics. The pressure wave acquisition and demodulation system comprises a pressure sensor for converting the mud pressure wave into an electric signal, and the demodulation system processes and demodulates the electric signal into meaningful data.

The mud signal transmission system comprises a plurality of devices and tools with complex structures and mechanical motion characteristics, and the devices and tools cause superimposed noise to mud pulse signals and affect the signal quality. These noises are usually generated by specific mechanical structures, and mainly include three types, one is periodic noises, such as mud pump noises, motor rotation noises, top drive or turntable rotation noises; the second type is non-periodic noise which is mainly expressed as signal attenuation, such as a flow channel converter, variable diameter in a flow channel, a drill water hole structure and the like; the third category is transient noise, which is generated only in special cases, such as a brief blockage of the drill hole. These noises combine to affect the mud pressure signal quality.

At present, in the mud pulse while-drilling data demodulation, the adopted noise elimination methods comprise a time domain pump noise elimination method, a frequency domain high-frequency electrical noise elimination method and the like, and in the prior art, the periodic noise interference cannot be well denoised, so that the signal is easy to distort.

Therefore, how to suppress and eliminate periodic noise in the frequency domain is an urgent problem to be solved for the MWD while drilling system.

Disclosure of Invention

In order to solve the technical problem, the invention provides a method for eliminating the noise of a MWD system, which realizes the suppression of periodic noise in a frequency domain, thereby eliminating the interference of the periodic noise.

In order to achieve the purpose of the invention, the invention provides a Measurement While Drilling (MWD) system noise elimination method, which comprises the following steps:

receiving an acquired mud signal and determining the characteristic frequency of a periodic noise signal in the mud signal;

carrying out Fourier transform on the mud signals to obtain frequency domain mud signals;

and obtaining a denoised mud frequency domain output signal according to the characteristic frequency of the periodic noise signal in the mud signal, the mud signal of the frequency domain and a preset suppression factor.

In an exemplary embodiment, the method of receiving an acquired mud signal and determining a characteristic frequency of a periodic noise signal in the mud signal comprises:

receiving the collected mud signals;

when the input pumping signal can be acquired, inputting the pumping signal into a pumping signal buffer;

and determining the average pumping frequency obtained according to the pumping signal in the pumping signal buffer as the characteristic frequency of the periodic noise signal in the mud signal.

In an exemplary embodiment, the receiving the collected mud signal and determining a characteristic frequency of a periodic noise signal in the mud signal includes:

receiving the collected mud signals;

when the pump pulse signal cannot be acquired but the preset frequency of any one or more periodic noise signals can be acquired, determining the acquired preset frequency of any one or more periodic noise signals as the characteristic frequency of the periodic noise signals in the mud signal.

In an exemplary embodiment, the receiving the collected mud signal and determining a characteristic frequency of a periodic noise signal in the mud signal includes:

receiving the collected mud signals;

when any periodic noise signal cannot be acquired, determining the central frequency of the periodic noise signal in the mud signal as the characteristic frequency of the periodic noise signal in the mud signal according to the frequency spectrum of the mud signal.

In one exemplary embodiment of the present invention,

the mud signal is: s_in＝[s_in(n) s_in(n+1) … s_in(n+K-1)]^T(ii) a Wherein s is_in(n) denotes the mud signal, s_inRepresenting an input mud signal vector, K being the length of the input signal vector, n representing the starting sequence number of the input signal;

before the fourier transform is performed on the mud signal to obtain a frequency-domain mud signal, the method further includes:

inputting the mud signal into a mud signal buffer to obtain a mud signal s in the mud signal buffer_b：

s_b＝[s_in(n-M) … s_in(n-2) s_in(n-1) s_in]^TThe length of each mud signal buffer is N, and N is K + M.

In an exemplary embodiment, the pumping signal is:

p_in＝[p_in(n) p_in(n+1) … p_in(n+K-1)]^T；

wherein p is_inRepresenting the input pumping signal vector, K being the length of the input signal vector, and n representing the starting sequence number of the input signal.

In an exemplary embodiment, the inputting the pumping signal into a pumping signal buffer when the inputted pumping signal can be acquired includes:

when the input pumping signal can be acquired, inputting the pumping signal into a pumping signal buffer to acquire a pumping signal p in the pumping signal buffer_b：

p_b＝[p_in(n-M) … p_in(n-2) p_in(n-1) p_in]^T；

The length of each pump signal buffer is N, and N is K + M.

In an exemplary embodiment, the determining the average pumping frequency obtained from the pumping signal in the pumping signal buffer as the characteristic frequency of the periodic noise signal in the mud signal includes:

calculating to obtain the average pumping frequency of the pumping signal in the pumping signal buffer according to the time corresponding to the rising edge of the pumping signal in the pumping signal buffer and an average pumping frequency calculation formula;

determining the average pumping frequency of the obtained pumping signal as the characteristic frequency of a periodic noise signal in the mud signal;

wherein, the average pump stroke frequency calculation formula comprises:

pump signal p in a pump signal buffer_bComprises L +1 rising edges, and the corresponding time of the rising edge is t_k,k＝0,1,2,...,L；

Represents the average pumping frequency; t is t_kL +1 represents the number of rising edges at the time corresponding to the rising edge.

In an exemplary embodiment, the fourier transforming the mud signal to obtain a frequency-domain mud signal includes:

windowing the mud signal in the mud signal buffer to obtain a windowed mud signal;

and carrying out Fourier transform on the windowed mud signal to obtain a frequency domain mud signal.

In an exemplary embodiment, the obtaining a denoised mud frequency domain output signal according to a characteristic frequency of a periodic noise signal in the mud signal, the mud signal in the frequency domain, and a preset suppression factor includes:

determining the frequency of an inhibition factor according to the characteristic frequency of a periodic noise signal in the mud signal;

multiplying the mud signal of the frequency domain by the suppression factor to obtain a noise-eliminated mud frequency domain output signal;

wherein the inhibitory factors include:

sw is a mud signal in a frequency domain, and the frequency of a suppression factor is

K is an integer and satisfies

Is a characteristic frequency; f. of₀The center frequency of the effective signal of the mud signal; b is_sFor mud signal activity in frequency domainThe bandwidth of the number; Δ f is the frequency resolution of the DFT transform of the mud signal:

indicating a rounding down. Alpha is alpha_jIs an inhibitor, alpha_jThe value is a positive real number less than 1.

In order to solve the above problem, the present invention further provides a measurement while drilling MWD system noise elimination apparatus, including: a memory and a processor;

the memory is used for storing a program for MWD system noise elimination;

the processor is used for reading and executing the program for MWD system noise elimination and executing the following operations:

receiving an acquired mud signal and determining the characteristic frequency of a periodic noise signal in the mud signal;

carrying out Fourier transform on the mud signals to obtain frequency domain mud signals;

and obtaining a denoised mud frequency domain output signal according to the characteristic frequency of the periodic noise signal in the mud signal, the mud signal of the frequency domain and a preset suppression factor.

In an exemplary embodiment, the receiving the collected mud signal and determining a characteristic frequency of a periodic noise signal in the mud signal includes:

receiving the collected mud signals;

when the input pumping signal can be acquired, inputting the pumping signal into a pumping signal buffer;

and determining the average pumping frequency obtained according to the pumping signal in the pumping signal buffer as the characteristic frequency of the periodic noise signal in the mud signal.

In an exemplary embodiment, the receiving the collected mud signal and determining a characteristic frequency of a periodic noise signal in the mud signal includes:

receiving the collected mud signals;

when the pump pulse signal cannot be acquired but the preset frequency of any one or more periodic noise signals can be acquired, determining the acquired preset frequency of any one or more periodic noise signals as the characteristic frequency of the periodic noise signals in the mud signal.

In an exemplary embodiment, the receiving the collected mud signal and determining a characteristic frequency of a periodic noise signal in the mud signal includes:

receiving the collected mud signals;

when any periodic noise signal cannot be acquired, determining the central frequency of the periodic noise signal in the mud signal as the characteristic frequency of the periodic noise signal in the mud signal according to the frequency spectrum of the mud signal.

In an exemplary embodiment, the mud signal is:

s_in＝[s_in(n) s_in(n+1) … s_in(n+K-1)]^T(ii) a Wherein s is_in(n) denotes the mud signal, s_inRepresenting an input mud signal vector, K being the length of the input signal vector, n representing the starting sequence number of the input signal;

before the fourier transform of the mud signal is performed to obtain a frequency-domain mud signal, the processor further performs the following operations:

inputting the mud signal into a mud signal buffer to obtain a mud signal s in the mud signal buffer_b：

s_b＝[s_in(n-M) … s_in(n-2) s_in(n-1) s_in]^TThe length of each mud signal buffer is N, and N is K + M.

In one exemplary embodiment of the present invention,

the pumping signal is: p is a radical of_in＝[p_in(n) p_in(n+1) … p_in(n+K-1)]^T；

Wherein p is_inRepresenting the input pumping signal vector, K being the inputThe length of the signal vector, n, represents the starting sequence number of the input signal.

In an exemplary embodiment, the inputting the pumping signal into a pumping signal buffer when the inputted pumping signal can be acquired includes:

when the input pumping signal can be acquired, inputting the pumping signal into a pumping signal buffer to acquire a pumping signal p in the pumping signal buffer_b：

p_b＝[p_in(n-M) … p_in(n-2) p_in(n-1) p_in]^T；

The length of each pump signal buffer is N, and N is K + M.

In an exemplary embodiment, the determining the average pumping frequency obtained from the pumping signal in the pumping signal buffer as the characteristic frequency of the periodic noise signal in the mud signal includes:

calculating to obtain the average pumping frequency of the pumping signal in the pumping signal buffer according to the time corresponding to the rising edge of the pumping signal in the pumping signal buffer and an average pumping frequency calculation formula;

determining the average pumping frequency of the obtained pumping signal as the characteristic frequency of a periodic noise signal in the mud signal;

wherein, the average pump stroke frequency calculation formula comprises:

pump signal p in a pump signal buffer_bComprises L +1 rising edges, and the corresponding time of the rising edge is t_k,k＝0,1,2,...,L；

Represents the average pumping frequency; t is t_kL +1 represents the number of rising edges at the time corresponding to the rising edge.

In an exemplary embodiment, the fourier transforming the mud signal to obtain a frequency-domain mud signal includes:

windowing the mud signal in the mud signal buffer to obtain a windowed mud signal;

and carrying out Fourier transform on the windowed mud signal to obtain a frequency domain mud signal.

In an exemplary embodiment, the obtaining a denoised mud frequency domain output signal according to a characteristic frequency of a periodic noise signal in the mud signal, the mud signal in the frequency domain, and a preset suppression factor includes:

determining the frequency of an inhibition factor according to the characteristic frequency of a periodic noise signal in the mud signal;

multiplying the mud signal of the frequency domain by the suppression factor to obtain a noise-eliminated mud frequency domain output signal;

wherein the inhibitory factors include:

said S_wFor the frequency-domain mud signal, the frequency of the suppression factor is

K is an integer and satisfies

Is a characteristic frequency; f. of₀The center frequency of the effective signal of the mud signal; b is_sIs the bandwidth of the effective signal of the mud signal in the frequency domain; Δ f is the frequency resolution of the DFT transform of the mud signal:

indicating a rounding down. Alpha is alpha_jIs an inhibitor, alpha_jThe value is a positive real number less than 1.

Compared with the prior art, the invention discloses a method for eliminating noise of a MWD system during measurement while drilling, which comprises the following steps: receiving an acquired mud signal and determining the characteristic frequency of a periodic noise signal in the mud signal; carrying out Fourier transform on the mud signals to obtain frequency domain mud signals; and obtaining a denoised mud frequency domain output signal according to the characteristic frequency of the periodic noise signal in the mud signal, the mud signal of the frequency domain and a preset suppression factor. By the scheme of the invention, the periodic noise of the MWD system during measurement while drilling is eliminated in the frequency domain.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the example serve to explain the principles of the invention and not to limit the invention.

FIG. 1 is a schematic diagram of the general architecture of a prior art drilling fluid MWD system;

FIG. 2 is a flowchart illustrating a signal processing procedure at a ground receiving end in the prior art;

FIG. 3 is a flow chart of a method for noise cancellation in a MWD system according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a noise elimination device of an MWD system for earth-boring measurement according to an embodiment of the present invention;

FIG. 5 is a prior art periodic noise cancellation flow diagram for a non-acquirable periodic signal;

FIG. 6 is a prior art periodic noise cancellation process for a signal that can be acquired periodically;

FIG. 7 is a flow chart of an exemplary MWD system noise cancellation method in accordance with an embodiment of the present invention;

FIG. 8 is a schematic diagram illustrating the effect of an exemplary noise elimination method for an MWD system according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, in the present application, the embodiments and features of the embodiments may be arbitrarily combined with each other without conflict.

The steps illustrated in the flow charts of the figures may be performed in a computer system such as a set of computer-executable instructions. Also, while a logical order is shown in the flow diagrams, in some cases, the steps shown or described may be performed in an order different than here.

Measurement While Drilling (MWD) is a technique that measures, collects well log data near the drill bit during the Drilling process, and transmits the collected data to a surface system in real time. The well log data typically includes formation property information and various drilling engineering parameters. As one of the most mature information transmission technologies used in the current drilling measurement while drilling, the basic working principle of the drilling fluid pressure signal transmission mode is to convert the underground measured information into control information, and apply the control information to an underground drilling fluid pressure signal generator to change the pressure of the drilling fluid in a transmission channel, so as to generate drilling fluid pressure pulsation, wherein the pressure pulsation is transmitted to the ground through the drilling fluid in the transmission channel, and is processed by a ground processing system to be converted into the required underground measurement information. The general structure of a drilling fluid MWD system is shown in fig. 1.

The mud pump drives the drilling fluid to circulate, the underground sending end sends data to the ground in a drilling fluid pressure pulse mode, the ground converts pressure change of the drilling fluid into an electric signal through the pressure sensor and sends the electric signal to the ground receiving unit, and the ground receiving unit is responsible for decoding the data sent underground.

The signal processing flow commonly used at the surface receiving end is shown in fig. 2, and the invention relates to the related technology of noise interference elimination, which is carried out in a preprocessing stage, so that the data sent underground can be accurately decoded by later data demodulation and decoding in the processing flow.

The drilling fluid signal transmission characteristics mainly comprise signal transmission speed, signal attenuation, signal reflection and the like. However, in the pressure transmission system of drilling fluid, during the transmission process of the pressure pulse signal from the bottom to the top of the drill string, since the drilling fluid belongs to three-phase flow of gas, liquid and solid, and contains solid-phase substances such as clay, rock debris, barite powder and the like, and gas-phase substances such as gas and the like in a free state often exist, the strength of the drilling fluid pressure signal generated by the pulse generator can be continuously attenuated, and the attenuation degree is influenced by signal frequency and transmission distance and is also related to internal parameters such as the inner diameter of a drilling fluid channel, the type and components of the drilling fluid, viscosity, volume gas content and the like. In summary, the drilling fluid channel is a channel with very complex transmission characteristics. In the information transmission mode, due to the influence of field measurement conditions, the output of a pressure sensor which is arranged on a vertical pipe and used for detecting mud pressure fluctuation comprises useful signals transmitted underground, pressure fluctuation caused by large-amplitude periodic pressure fluctuation and other various mechanical actions due to mud compression of a mud pump and random noise, interference is represented as periodic pulses related to pump impulse characteristics, the noise is represented as broadband white noise, the amplitude of the noise is far larger than that of the useful signals, and the signals at a wellhead are completely submerged in various noises.

According to actual measurement, the statistical distribution of the drilling fluid noise signals in the time domain is in normal distribution, and meanwhile, the drilling fluid noise signals contain strong periodic components. The cyclic components include mud pump noise, motor rotation noise, top drive or turntable rotation noise, and the like.

FIG. 3 is a flow chart of a method for noise cancellation in a MWD system according to an embodiment of the present invention.

301, receiving the collected mud signal and determining the characteristic frequency of the periodic noise signal in the mud signal.

In this embodiment, the measurement while drilling MWD system is used for measuring downhole geological parameters in real time during drilling, and includes: borehole trajectory parameters are measured while drilling, for example: angle of inclination, azimuth, tool face angle, and auxiliary parameters such as temperature.

In various interferences and noises of a drilling fluid while-drilling data transmission system, the pulse amplitude generated by a mud pump is strong, and when the frequency component of the pulse amplitude is mixed with a mud wave signal sent underground, the pulse amplitude can form strong interference on a useful signal. Although the pump stroke interference amplitude of the mud pump is strong, the mud pump has obvious periodic characteristics. Periodic noise includes mud pump noise, motor rotation noise, top drive or turntable rotation noise, and the like.

In an exemplary embodiment, the method of receiving an acquired mud signal and determining a characteristic frequency of a periodic noise signal in the mud signal comprises: receiving the collected mud signals; when the input pumping signal can be obtained, inputting the pumping signal into a pumping signal buffer; and determining the average pumping frequency obtained according to the pumping signal in the pumping signal buffer as the characteristic frequency of the periodic noise signal in the mud signal.

The mud signal is: s_in＝[s_in(n) s_in(n+1) … s_in(n+K-1)]^T(ii) a Wherein s is_in(n) denotes the mud signal, s_inRepresenting an input mud signal vector, K being the length of the input signal vector, n representing the starting sequence number of the input signal;

in an exemplary embodiment, the mud signal is input into a mud signal buffer to obtain a mud signal s in the mud signal buffer_b：

s_b＝[s_in(n-M) … s_in(n-2) s_in(n-1) s_in]^TThe length of each mud signal buffer is N, and N is K + M.

In an exemplary embodiment, the pumping signal is:

p_in＝[p_in(n) p_in(n+1) … p_in(n+K-1)]^T；

wherein p is_inRepresenting the input pumping signal vector, K being the length of the input signal vector, and n representing the starting sequence number of the input signal.

In an exemplary embodiment, the inputting the pumping signal into a pumping signal buffer when the inputted pumping signal can be acquired includes:

when the input pumping signal can be acquired, inputting the pumping signal into a pumping signal buffer to acquire a pumping signal p in the pumping signal buffer_b：

p_b＝[p_in(n-M) … p_in(n-2) p_in(n-1) p_in]^T；

The length of the pump signal buffer is N, where N is K + M, and M represents the original signal vector length in the signal buffer.

In an exemplary embodiment, the determining the average pumping frequency obtained from the pumping signal in the pumping signal buffer as the characteristic frequency of the periodic noise signal in the mud signal includes:

calculating to obtain the average pumping frequency of the pumping signal in the pumping signal buffer according to the time corresponding to the rising edge of the pumping signal in the pumping signal buffer and an average pumping frequency calculation formula;

determining the average pumping frequency of the obtained pumping signal as the characteristic frequency of a periodic noise signal in the mud signal;

wherein, the average pump stroke frequency calculation formula comprises:

pump signal p in a pump signal buffer_bComprises L +1 rising edges, and the corresponding time of the rising edge is t_k,k＝0,1,2,...,L；

Represents the average pumping frequency; t is t_kL +1 represents the number of rising edges at the time corresponding to the rising edge.

In an exemplary embodiment, the receiving the collected mud signal and determining a characteristic frequency of a periodic noise signal in the mud signal includes: receiving the collected mud signals; when the pump pulse signal cannot be acquired but the preset frequency of any one or more periodic noise signals can be acquired, determining the acquired preset frequency of any one or more periodic noise signals as the characteristic frequency of the periodic noise signals in the mud signal. In this embodiment, the periodic noise signal includes top drive noise, and the input frequency of the top drive, that is, the frequency of the top drive, can be directly obtained by the top drive device, where the periodic noise signal includes, but is not limited to, top drive noise, and includes all periodic noise of the preset frequency that can be obtained.

In an exemplary embodiment, the receiving the collected mud signal and determining a characteristic frequency of a periodic noise signal in the mud signal includes: receiving the collected mud signals; when any periodic noise signal cannot be acquired, determining the central frequency of the periodic noise signal in the mud signal as the characteristic frequency of the periodic noise signal in the mud signal according to the frequency spectrum of the mud signal. In the present embodiment, the case where the noise frequency cannot be obtained is addressed.

And 302, carrying out Fourier transform on the mud signals to obtain frequency-domain mud signals.

In this embodiment, the mud signal is fourier transformed to obtain a frequency domain mud signal.

In an exemplary embodiment, the mud signal is:

s_in＝[s_in(n) s_in(n+1) … s_in(n+K-1)]^T(ii) a Wherein s is_in(n) denotes the mud signal, s_inRepresenting an input mud signal vector, K being the length of the input signal vector, n representing the starting sequence number of the input signal;

before the fourier transform is performed on the mud signal to obtain a frequency-domain mud signal, the method further includes:

inputting the mud signal into a mud signal buffer to obtain a mud signal s in the mud signal buffer_b：

s_b＝[s_in(n-M) … s_in(n-2) s_in(n-1) s_in]^TThe length of each mud signal buffer is N, wherein N is K + M, and M represents the length of an original signal vector in the signal buffer.

In an exemplary embodiment, the fourier transforming the mud signal to obtain a frequency-domain mud signal includes: windowing the mud signal in the mud signal buffer to obtain a windowed mud signal; and carrying out Fourier transform on the windowed mud signal to obtain a frequency domain mud signal. In this embodiment, the mud signal sb in the mud signal buffer is multiplied by a preset window function, and a windowed mud signal s is calculated_wThe calculation formula of the windowing processing is as follows:

s_w＝s_b·w_N，

wherein, w_N＝[w(0) w(1) … w(N-1)]^TThe window function has a length N,

if the selected window function vector is:

s_w＝s_b·w_N"·" in the formula means that two vectors are correspondingly multiplied element by element.

In this embodiment, the window function in the windowing process may be a hanning window, or may select another window function, which is not specifically limited, and different window functions may be selected according to the information related to the well data to be processed.

And 303, obtaining a denoised mud frequency domain output signal according to the characteristic frequency of the periodic noise signal in the mud signal, the mud signal of the frequency domain and a preset suppression factor.

In this embodiment, a denoised mud frequency domain output signal is obtained according to the average pumping frequency, the mud signal in the frequency domain, and a preset suppression factor. The value of the suppression factor can be set as a fixed value, and can also be selected according to the intensity of pump impulse interference and the suppression effect expected to be achieved; the smaller the value of the suppression factor is, the more obvious the suppression is on the pump impulse interference component of the corresponding frequency.

In an exemplary embodiment, the obtaining a denoised mud frequency domain output signal according to the average pumping frequency, the mud signal in the frequency domain and a preset suppression factor includes:

multiplying the mud signal of the frequency domain by an inhibition factor to obtain a noise-eliminated mud frequency domain output signal;

wherein the inhibitory factors include:

wherein S is_wFor the frequency-domain mud signal, the frequency of the suppression factor is

K is an integer and satisfies

Is a characteristic frequency; f. of₀Is the center frequency of the effective signal of the mud signal in the frequency domain; b is_sThe bandwidth of the effective signal of the mud signal in a frequency domain; Δ f is the frequency resolution of the mud signal for DFT conversion:

indicating a rounding down. Alpha is alpha_jIs an inhibitor, alpha_jA positive real number with a value less than 1. In this embodiment, the specific implementation process is as follows: to s_wDFT conversion is carried out to obtain a frequency domain signal S_w＝DFT{s_wHere, DFT { · } represents a DFT operation. s_wThe frequency domain mud signal may be a windowed frequency domain mud signal. In the frequency domain, for S_wThe pump interference component in the effective signal bandwidth is suppressed, namely the suppression frequency is

K is an integer and satisfies

f₀The effective mud signal center frequency, which is the frequency generated by the downhole pulser and is required to be transmitted to the surface acquisition system for demodulation processing, f₀Determined by the modulation scheme and frequency of the useful signal, i.e. after determining the modulation scheme and frequency used, f is obtained₀；B_sIs the effective signal bandwidth. The frequency resolution of the DFT fourier transform is:

wherein, T_sIs the sampling period of the mud signal, and N is the number of sampling points.

In this embodiment, a suppression vector is defined:

a＝[a(0) a(1) ... a(N-1)]^Twherein the content of the first and second substances,

k is an integer and satisfies

Indicating a rounding down. Alpha is alpha_jIs attenuationFactor, which is a positive real number less than 1.

After the suppression factor is defined, noise elimination processing is carried out on the mud signal in the frequency domain, and the calculation formula of the noise elimination processing is as follows:

S_dn＝S_wa wherein s_wThe mud signal is a frequency domain mud signal or a windowed frequency domain mud signal, and a is an inhibition factor; s_dnThe noise-eliminated mud signal is the frequency domain mud signal.

In an exemplary embodiment, the denoised frequency domain mud signal S_dnIDFT (inverse discrete Fourier transform) is adopted to transform the time domain to obtain a denoised mud signal s of the time domain_dn：

s_dn＝IDFT{S_dn}

If s_dn＝[s_dn(0) s_dn(1) ... s_dn(N-1)]^TIntercepting the denoised mud signal s of the time domain_dnAnd obtaining the signal vector of the output slurry after the pump impulse interference is eliminated by the central K sampling points:

in order to solve the above problem, as shown in fig. 4, the present invention also provides a measurement while drilling MWD system noise elimination apparatus, including: a memory and a processor;

the memory is used for storing a program for MWD system noise elimination;

the processor is used for reading and executing the program for MWD system noise elimination and executing the following operations:

receiving an acquired mud signal and determining the characteristic frequency of a periodic noise signal in the mud signal;

carrying out Fourier transform on the mud signals to obtain frequency domain mud signals;

and obtaining a denoised mud frequency domain output signal according to the characteristic frequency of the periodic noise signal in the mud signal, the mud signal of the frequency domain and a preset suppression factor.

In an exemplary embodiment, the receiving the collected mud signal and determining a characteristic frequency of a periodic noise signal in the mud signal includes:

receiving the collected mud signals;

when the input pumping signal can be acquired, inputting the pumping signal into a pumping signal buffer;

and determining the average pumping frequency obtained according to the pumping signal in the pumping signal buffer as the characteristic frequency of the periodic noise signal in the mud signal.

In an exemplary embodiment, the receiving the collected mud signal and determining a characteristic frequency of a periodic noise signal in the mud signal includes:

receiving the collected mud signals;

when the pump pulse signal cannot be acquired but the preset frequency of any one or more periodic noise signals can be acquired, determining the acquired preset frequency of any one or more periodic noise signals as the characteristic frequency of the periodic noise signals in the mud signal.

In an exemplary embodiment, the receiving the collected mud signal and determining a characteristic frequency of a periodic noise signal in the mud signal includes:

receiving the collected mud signals;

when any periodic noise signal cannot be acquired, determining the central frequency of the periodic noise signal in the mud signal as the characteristic frequency of the periodic noise signal in the mud signal according to the frequency spectrum of the mud signal.

In an exemplary embodiment, the mud signal is:

s_in＝[s_in(n) s_in(n+1) … s_in(n+K-1)]^T(ii) a Wherein s is_in(n) denotes the mud signal, s_inRepresenting an input mud signal vector, K being the length of the input signal vector, n representing the starting sequence number of the input signal;

before the fourier transform of the mud signal is performed to obtain a frequency-domain mud signal, the processor further performs the following operations:

inputting the mud signal into a mud signal buffer to obtain a mud signal s in the mud signal buffer_b：

s_b＝[s_in(n-M) … s_in(n-2) s_in(n-1) s_in]^TThe length of each mud signal buffer is N, and N is K + M.

In one exemplary embodiment of the present invention,

the pumping signal is: p is a radical of_in＝[p_in(n) p_in(n+1) … p_in(n+K-1)]^T；

Wherein p is_inRepresenting the input pumping signal vector, K being the length of the input signal vector, and n representing the starting sequence number of the input signal.

In an exemplary embodiment, the inputting the pumping signal into a pumping signal buffer when the inputted pumping signal can be acquired includes:

when the input pumping signal can be acquired, inputting the pumping signal into a pumping signal buffer to acquire a pumping signal p in the pumping signal buffer_b：

p_b＝[p_in(n-M) … p_in(n-2) p_in(n-1) p_in]^T；

The length of each pump signal buffer is N, and N is K + M.

In an exemplary embodiment, the determining the average pumping frequency obtained from the pumping signal in the pumping signal buffer as the characteristic frequency of the periodic noise signal in the mud signal includes:

calculating to obtain the average pumping frequency of the pumping signal in the pumping signal buffer according to the time corresponding to the rising edge of the pumping signal in the pumping signal buffer and an average pumping frequency calculation formula;

determining the average pumping frequency of the obtained pumping signal as the characteristic frequency of a periodic noise signal in the mud signal;

wherein, the average pump stroke frequency calculation formula comprises:

pump signal p in a pump signal buffer_bComprises L +1 rising edges, and the corresponding time of the rising edge is t_k,k＝0,1,2,...,L；

Represents the average pumping frequency; t is t_kL +1 represents the number of rising edges at the time corresponding to the rising edge.

In an exemplary embodiment, the fourier transforming the mud signal to obtain a frequency-domain mud signal includes:

windowing the mud signal in the mud signal buffer to obtain a windowed mud signal;

and carrying out Fourier transform on the windowed mud signal to obtain a frequency domain mud signal.

In an exemplary embodiment, the obtaining a denoised mud frequency domain output signal according to a characteristic frequency of a periodic noise signal in the mud signal, the mud signal in the frequency domain, and a preset suppression factor includes:

determining the frequency of an inhibition factor according to the characteristic frequency of a periodic noise signal in the mud signal;

multiplying the mud signal of the frequency domain by the suppression factor to obtain a noise-eliminated mud frequency domain output signal;

wherein the inhibitory factors include:

said S_wFor the frequency-domain mud signal, the frequency of the suppression factor is

K is an integer and satisfies

Is a characteristic frequency; f. of₀The center frequency of the effective signal of the mud signal; b is_sIs the bandwidth of the effective signal of the mud signal in the frequency domain; Δ f is the frequency resolution of the DFT transform of the mud signal:

indicating a rounding down. Alpha is alpha_jIs an inhibitor, alpha_jThe value is a positive real number less than 1.

An exemplary embodiment

Among various interferences and noises of a drilling fluid while-drilling data transmission system, the pulse amplitude generated by a mud pump is strong, and when the frequency component of the pulse amplitude is mixed with a mud wave signal sent underground, the pulse amplitude can form strong interference on a useful signal and is difficult to remove. In the prior art, a periodic noise cancellation process for a non-acquirable periodic signal is shown in fig. 5, and a periodic noise cancellation process for an acquirable periodic signal is shown in fig. 6. The method for periodic pump noise cancellation is shown in fig. 7:

and 701, receiving the collected mud signals and acquiring input pumping signals.

In the step, the pump stroke interference of the slurry pump is high in amplitude, but the analysis of the pump stroke interference has obvious periodic characteristics. The collected mud signal can be s_in(n) the input pumping signal is p_in(n)；

The mud signals collected were: s_in＝[s_in(n) s_in(n+1) … s_in(n+K-1)]^T；

The input pump pulse signal is: p is a radical of_in＝[p_in(n) p_in(n+1) … p_in(n+K-1)]^T；

Wherein s is_in(n) denotes the mud signal, s_inRepresenting the input mud signal vector, p_inRepresenting the input pumping signal vector, and K is the length of the input signal vector.

And 702, inputting the mud signal and the pumping signal into a mud signal buffer and a pumping signal buffer respectively.

In the step, the mud signal is input into a mud signal buffer to obtain a mud signal s in the mud signal buffer_b：

s_b＝[s_in(n-M) … s_in(n-2) s_in(n-1) s_in]^TInputting the pumping signal into a pumping signal buffer to obtain a pumping signal p in the pumping signal buffer_b：

p_b＝[p_in(n-M) … p_in(n-2) p_in(n-1) p_in]^T；

The length of the mud signal buffer and the pump stroke signal buffer is both N, and N is K + M.

And 703, obtaining the average pumping frequency according to the pumping signal in the pumping signal buffer.

In this step, the average pumping frequency of the pumping signal in the pumping signal buffer is calculated according to the time corresponding to the rising edge of the pumping signal in the pumping signal buffer and an average pumping frequency calculation formula;

wherein the average pumping frequency calculation formula comprises:

pump signal p in a pump signal buffer_bComprises L +1 rising edges, and the corresponding time of the rising edge is t_k,k＝0,1,2,...,L；

Wherein the content of the first and second substances,

represents the average pumping frequency; t is t_kL +1 represents the number of rising edges at the time corresponding to the rising edge.

And 704, windowing the mud signal in the mud signal buffer.

In this step, windowing is performed on the mud signal in the mud signal buffer, and the formula of the windowing is as follows:

s_w＝s_b·w_N，

wherein, w_N＝[w(0) w(1) … w(N-1)]^TA window function of a hanning window of length N,

the window function vector of the Hanning window is:

wherein s is_w＝s_b·w_N"·" in the formula means that two vectors are correspondingly multiplied element by element. And 705, performing Fourier transform on the mud signals in the mud signal buffer subjected to windowing processing to obtain frequency-domain mud signals.

In this step, the windowed mud signal s in the mud signal buffer is processed_wDFT conversion is carried out to obtain a frequency domain mud signal S_w，

S_w＝DFT{s_wHere, DFT { · } represents a DFT operation.

Step 706, setting the suppression factor and determining the suppression vector.

a＝[a(0) a(1) ... a(N-1)]^T。

Determining an inhibitory factor comprising:

wherein, the S_wFor the frequency-domain mud signal, the frequency of the suppression factor is

K is an integer and satisfies

Is the average pumping frequency; f. of₀Is the center frequency of the effective signal of the mud signal in the frequency domain; b is_sIs the bandwidth of the effective signal of the mud signal in the frequency domain; Δ f is the frequency resolution of the DFT transform of the mud signal:

indicating a rounding down. Alpha is alpha_jIs an inhibitor, alpha_jPositive real numbers with values less than 1.

And step 707, multiplying the mud signal of the frequency domain by the suppression factor to obtain a noise-eliminated mud frequency domain output signal.

In this step, after the suppression factor is defined, noise cancellation processing is performed on the mud signal in the frequency domain, and a calculation formula of the noise cancellation processing is as follows:

S_dn＝S_wa wherein s_wThe mud signal is a frequency domain mud signal or a windowed frequency domain mud signal, and a is an inhibition factor; s_dnThe noise-eliminated mud signal is the frequency domain mud signal.

Step 708 (not shown) is to denoise the frequency domain mud signal S_dnIDFT (inverse discrete Fourier transform) is adopted to transform the time domain to obtain a denoised mud signal s of the time domain_dn：

s_dn＝IDFT{S_dn}

709 (not shown), obtaining a signal of the denoised output mud according to the time domain denoised mud signal. In this step, s_dn＝[s_dn(0) s_dn(1) ... s_dn(N-1)]^TIntercepting the time-domain denoised mud signal s_dnAnd obtaining a signal vector of the output slurry after the pump stroke interference is eliminated by the central K sampling points:

the noise reduction effect of the noise reduction processing procedure of the embodiment on the actual drilling mud signals in the frequency domain is shown in fig. 8. The effective signal of the mud signal is a 2FSK modulation signal with 4bps, the two carrier frequencies are respectively 4Hz and 8Hz, and the signal frequency band range is 2 Hz-10 Hz. As can be seen in fig. 8-a, the surface acquired signal contains a significant component of pump-induced interference. It can be seen from fig. 8-b that the pumping interference component is not significant in the range of 2Hz to 10Hz after noise cancellation, and only 4Hz and 8Hz carrier components remain.

In the embodiment, the pump noise elimination is carried out in the frequency domain for the MWD system, and the periodic component of the pump impulse interference is restrained in the frequency domain, so that the periodic noise is eliminated by the frequency domain method for eliminating the pump impulse interference, and a good denoising effect can be obtained.

An exemplary embodiment

The method for eliminating the noise of the MWD system comprises the following steps:

step 801. receive the collected mud signal.

In this step, the collected mud signal can be regarded as s_in(n), the collected mud signals are: s_in＝[s_in(n) s_in(n+1) … s_in(n+K-1)]^T(ii) a Wherein s is_in(n) denotes the mud signal, s_inRepresenting the input mud signal vector, K being the length of the input signal vector, and n representing the starting sequence number of the input signal.

And step 802, inputting the mud signal into a mud signal buffer.

In the step, the mud signal is input into a mud signal buffer to obtain a mud signal s in the mud signal buffer_b：

s_b＝[s_in(n-M) … s_in(n-2) s_in(n-1) s_in]^TThe length of the mud signal buffer is N, wherein N is K + M, and M represents the length of the original signal vector in the signal buffer.

And 803, determining the characteristic frequency of the periodic noise signal in the mud signal.

In this step, a preset frequency of any one or more periodic noise signals is acquired, and the acquired preset frequency is determined as a characteristic frequency of the periodic noise signals in the mud signal. For example: the frequency of the top drive noise is retrievable.

And 804, windowing the mud signals in the mud signal buffer.

In this step, windowing is performed on the mud signal in the mud signal buffer, and the formula of the windowing is as follows:

s_w＝s_b·w_N，

wherein, w_N＝[w(0) w(1) … w(N-1)]^TA window function of a hanning window of length N,

the window function vector of the Hanning window is:

wherein s is_w＝s_b·w_N"·" in the formula means that two vectors are correspondingly multiplied element by element. And 805, performing Fourier transform on the mud signals in the windowed mud signal buffer to obtain frequency domain mud signals.

In this step, the windowed mud signal s in the mud signal buffer is processed_wDFT conversion is carried out to obtain a frequency domain mud signal S_w，

S_w＝DFT{s_wHere, DFT { · } represents a DFT operation.

Step 806, setting a suppression factor and determining a suppression vector.

a＝[a(0) a(1) ... a(N-1)]^T。

Determining an inhibitory factor comprising:

wherein, the S_wFor the frequency-domain mud signal, the frequency of the suppression factor is

K is an integer and satisfies

Is a characteristic frequency; f. of₀Is the center frequency of the effective signal of the mud signal in the frequency domain; b is_sIs the bandwidth of the effective signal of the mud signal in the frequency domain; Δ f is the frequency resolution of the DFT transform of the mud signal:

indicating a rounding down. Alpha is alpha_jIs an inhibitor, alpha_jPositive real numbers with values less than 1.

And step 807, multiplying the mud signal of the frequency domain by the suppression factor to obtain a noise-eliminated mud frequency domain output signal.

In this step, after the suppression factor is defined, noise cancellation processing is performed on the mud signal in the frequency domain, and a calculation formula of the noise cancellation processing is as follows:

S_dn＝S_wa wherein s_wThe mud signal is a frequency domain mud signal or a windowed frequency domain mud signal, and a is an inhibition factor; s_dnThe noise-eliminated mud signal is the frequency domain mud signal.

Step 808, de-noising the frequency domain mud signal S_dnIDFT (inverse discrete Fourier transform) is adopted to transform the time domain to obtain a denoised mud signal of the time domains_dn：

s_dn＝IDFT{S_dn}

And step 809, obtaining a signal of the denoised output mud according to the denoised mud signal of the time domain.

In this step, s_dn＝[s_dn(0) s_dn(1) ... s_dn(N-1)]^TIntercepting the denoised mud signal s of the time domain_dnAnd obtaining the signal vector of the output slurry after the pump impulse interference is eliminated by the central K sampling points:

in the embodiment, noise elimination in a frequency domain is provided for the MWD system, and periodic components are suppressed in the frequency domain, so that the purpose of eliminating noise interference is achieved.

An exemplary embodiment

The method for eliminating the noise of the MWD system comprises the following steps:

and step 901, receiving the collected mud signals.

In this step, the collected mud signal can be regarded as s_in(n), the collected mud signals are:

wherein s is_in(n) denotes the mud signal, s_inRepresenting the input mud signal vector, K being the length of the input signal vector, and n representing the starting sequence number of the input signal.

And 902, inputting the mud signal into a mud signal buffer.

In the step, the mud signal is input into a mud signal buffer to obtain a mud signal s in the mud signal buffer_b：

s_b＝[s_in(n-M) … s_in(n-2) s_in(n-1) s_in]^TThe length of the mud signal buffer is N, N is K + M, and M represents the signal bufferThe original signal vector length in the dasher.

And 903, determining the characteristic frequency of the periodic noise signal in the mud signal.

In this step, the center frequency of the periodic noise signal in the mud signal is determined as the characteristic frequency of the periodic noise signal in the mud signal. For the case that the frequency of the noise cannot be determined and the noise signal cannot be acquired, the center frequency of the periodic noise signal in the mud signal can be used to determine the characteristic frequency of the periodic noise signal in the mud signal.

And 904, windowing the mud signal in the mud signal buffer.

In this step, windowing is performed on the mud signal in the mud signal buffer, and the formula of the windowing is as follows:

s_w＝s_b·w_N，

wherein, w_N＝[w(0) w(1) … w(N-1)]A window function of a hanning window of length N,

the window function vector of the Hanning window is:

wherein s is_w＝s_b·w_N"·" in the formula means that two vectors are correspondingly multiplied element by element. And 905, carrying out Fourier transform on the mud signals in the windowed mud signal buffer to obtain frequency domain mud signals.

In this step, the windowed mud signal s in the mud signal buffer is processed_wDFT conversion is carried out to obtain a frequency domain mud signal S_w，

S_w＝DFT{s_wHere, DFT { · } represents a DFT operation.

And step 906, setting a suppression factor and determining a suppression vector.

a＝[a(0) a(1) ... a(N-1)]^T。

Determining an inhibitory factor comprising:

wherein, the S_wFor the frequency-domain mud signal, the frequency of the suppression factor is

K is an integer and satisfies

Is a characteristic frequency; f. of₀Is the center frequency of the effective signal of the mud signal in the frequency domain; b is_sIs the bandwidth of the effective signal of the mud signal in the frequency domain; Δ f is the frequency resolution of the DFT transform of the mud signal:

indicating a rounding down. Alpha is alpha_jIs an inhibitor, alpha_jPositive real numbers with values less than 1.

And step 907, multiplying the mud signal of the frequency domain by the suppression factor to obtain a noise-eliminated mud frequency domain output signal.

In this step, after the suppression factor is defined, noise cancellation processing is performed on the mud signal in the frequency domain, and a calculation formula of the noise cancellation processing is as follows:

S_dn＝S_wa wherein s_wThe mud signal is a frequency domain mud signal or a windowed frequency domain mud signal, and a is an inhibition factor; s_dnThe noise-eliminated mud signal is the frequency domain mud signal.

Step 908, the noise-eliminated frequency domain mud signal S_dnIDFT (inverse discrete Fourier transform) is adopted to transform the time domain to obtain a denoised mud signal s of the time domain_dn：

s_dn＝IDFT{S_dn}

And step 909, obtaining a signal of the denoised output mud according to the denoised mud signal of the time domain.

In this step, s_dn＝[s_dn(0) s_dn(1) ... s_dn(N-1)]^TIntercepting the denoised mud signal s of the time domain_dnAnd obtaining the signal vector of the output slurry after the pump impulse interference is eliminated by the central K sampling points:

in the embodiment, noise elimination in a frequency domain is provided for the MWD system, and periodic components are suppressed in the frequency domain, so that the purpose of eliminating noise interference is achieved.

It will be understood by those of ordinary skill in the art that all or some of the steps of the methods, systems, functional modules/units in the devices disclosed above may be implemented as software, firmware, hardware, and suitable combinations thereof. In a hardware implementation, the division between functional modules/units mentioned in the above description does not necessarily correspond to the division of physical components; for example, one physical component may have multiple functions, or one function or step may be performed by several physical components in cooperation. Some or all of the components may be implemented as software executed by a processor, such as a digital signal processor or microprocessor, or as hardware, or as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on computer readable media, which may include computer storage media (or non-transitory media) and communication media (or transitory media). The term computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data, as is well known to those of ordinary skill in the art. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, Digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can accessed by a computer. In addition, communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media as known to those skilled in the art.

Claims (18)

1. A method of noise cancellation in a measurement-while-drilling MWD system, the method comprising:

receiving an acquired mud signal and determining the characteristic frequency of a periodic noise signal in the mud signal;

carrying out Fourier transform on the mud signals to obtain frequency domain mud signals;

obtaining a denoised mud frequency domain output signal according to the characteristic frequency of the periodic noise signal in the mud signal, the mud signal of the frequency domain and a preset suppression factor;

the obtaining of the denoised mud frequency domain output signal according to the characteristic frequency of the periodic noise signal in the mud signal, the mud signal of the frequency domain and a preset suppression factor comprises:

determining the frequency of an inhibition factor according to the characteristic frequency of a periodic noise signal in the mud signal;

multiplying the mud signal of the frequency domain by the suppression factor to obtain a noise-eliminated mud frequency domain output signal;

wherein the inhibitory factors include:

said S_wFor the frequency-domain mud signal, the frequency of the suppression factor is

K is an integer and satisfies

Is a characteristic frequency; f. of₀The center frequency of the effective signal of the mud signal; b is_sIs the bandwidth of the effective signal of the mud signal in the frequency domain; Δ f is the frequency resolution of the DFT transform of the mud signal:

represents rounding down; alpha is alpha_jIs an inhibitor, alpha_jPositive real numbers with values less than 1.

2. The MWD system noise cancellation method of claim 1, wherein the receiving the acquired mud signal and determining the characteristic frequency of the periodic noise signal in the mud signal comprises:

receiving the collected mud signals;

when the input pumping signal can be acquired, inputting the pumping signal into a pumping signal buffer;

and determining the average pumping frequency obtained according to the pumping signal in the pumping signal buffer as the characteristic frequency of the periodic noise signal in the mud signal.

3. The MWD system noise cancellation method of claim 2, wherein the receiving the acquired mud signal and determining the characteristic frequency of the periodic noise signal in the mud signal comprises:

receiving the collected mud signals;

when the pump pulse signal cannot be acquired but the preset frequency of any one or more periodic noise signals can be acquired, determining the acquired preset frequency of any one or more periodic noise signals as the characteristic frequency of the periodic noise signals in the mud signal.

4. The MWD system noise cancellation method of claim 3, wherein the receiving the acquired mud signal and determining the characteristic frequency of the periodic noise signal in the mud signal comprises:

receiving the collected mud signals;

when any periodic noise signal cannot be acquired, determining the central frequency of the periodic noise signal in the mud signal as the characteristic frequency of the periodic noise signal in the mud signal according to the frequency spectrum of the mud signal.

5. The MWD system noise cancellation method of claim 1,

the mud signal is: s_in＝[s_in(n) s_in(n+1) … s_in(n+K-1)]^T(ii) a Wherein s is_in(n) denotes the mud signal, s_inRepresenting an input mud signal vector, K being the length of the input signal vector, n representing the starting sequence number of the input signal;

before the fourier transform is performed on the mud signal to obtain a frequency-domain mud signal, the method further includes:

inputting the mud signal into a mud signal buffer to obtain a mud signal s in the mud signal buffer_b：

s_b＝[s_in(n-M) … s_in(n-2) s_in(n-1) s_in]^TThe length of each mud signal buffer is N, and N is K + M.

6. The MWD system noise cancellation method of claim 2,

the pumping signal is: p is a radical of_in＝[p_in(n) p_in(n+1) … p_in(n+K-1)]^T；

Wherein p is_inRepresenting the input pumping signal vector, K being the length of the input signal vector, and n representing the starting sequence number of the input signal.

7. The MWD system noise cancellation method according to claim 6, wherein the inputting the pumping signal to a pumping signal buffer when the inputted pumping signal can be acquired comprises:

when the input pumping signal can be acquired, inputting the pumping signal into a pumping signal buffer to acquire a pumping signal p in the pumping signal buffer_b：

p_b＝[p_in(n-M) … p_in(n-2) p_in(n-1) p_in]^T；

The length of each pump signal buffer is N, and N is K + M.

8. The MWD system noise cancellation method of claim 7, wherein the determining the average pumping frequency derived from the pumping signal in the pumping signal buffer as the characteristic frequency of the periodic noise signal in the mud signal comprises:

calculating to obtain the average pumping frequency of the pumping signal in the pumping signal buffer according to the time corresponding to the rising edge of the pumping signal in the pumping signal buffer and an average pumping frequency calculation formula;

determining the average pumping frequency of the obtained pumping signal as the characteristic frequency of a periodic noise signal in the mud signal;

wherein, the average pump stroke frequency calculation formula comprises:

pump signal p in a pump signal buffer_bComprises L +1 rising edges, and the corresponding time of the rising edge is t_k,k＝0,1,2,...,L；

Represents the average pumping frequency; t is t_kL +1 represents the number of rising edges at the time corresponding to the rising edge.

9. The MWD system noise cancellation method of claim 5, wherein the fourier transforming the mud signal to obtain a frequency domain mud signal comprises:

windowing the mud signal in the mud signal buffer to obtain a windowed mud signal;

and carrying out Fourier transform on the windowed mud signal to obtain a frequency domain mud signal.

10. An MWD system noise cancellation device, the device comprising: a memory and a processor; the method is characterized in that:

the memory is used for storing a program for MWD system noise elimination;

the processor is used for reading and executing the program for MWD system noise elimination and executing the following operations:

receiving an acquired mud signal and determining the characteristic frequency of a periodic noise signal in the mud signal;

carrying out Fourier transform on the mud signals to obtain frequency domain mud signals;

obtaining a denoised mud frequency domain output signal according to the characteristic frequency of the periodic noise signal in the mud signal, the mud signal of the frequency domain and a preset suppression factor;

the processor obtains a denoised mud frequency domain output signal according to the characteristic frequency of the periodic noise signal in the mud signal, the mud signal of the frequency domain and a preset suppression factor, and the denoised mud frequency domain output signal comprises the following steps:

determining the frequency of an inhibition factor according to the characteristic frequency of a periodic noise signal in the mud signal;

multiplying the mud signal of the frequency domain by the suppression factor to obtain a noise-eliminated mud frequency domain output signal;

wherein the inhibitory factors include:

said S_wFor the frequency-domain mud signal, the frequency of the suppression factor is

K is an integer and satisfies

Is a characteristic frequency; f. of₀The center frequency of the effective signal of the mud signal; b is_sIs the bandwidth of the effective signal of the mud signal in the frequency domain; Δ f is the frequency resolution of the DFT transform of the mud signal:

represents rounding down; alpha is alpha_jIs an inhibitor, alpha_jPositive real numbers with values less than 1.

11. The MWD system noise cancellation device according to claim 10, wherein the receiving the acquired mud signal and determining the characteristic frequency of the periodic noise signal in the mud signal comprises:

receiving the collected mud signals;

when the input pumping signal can be acquired, inputting the pumping signal into a pumping signal buffer;

and determining the average pumping frequency obtained according to the pumping signal in the pumping signal buffer as the characteristic frequency of the periodic noise signal in the mud signal.

12. The MWD system noise cancellation device according to claim 11, wherein the receiving the acquired mud signal and determining the characteristic frequency of the periodic noise signal in the mud signal comprises:

receiving the collected mud signals;

when the pump pulse signal cannot be acquired but the preset frequency of any one or more periodic noise signals can be acquired, determining the acquired preset frequency of any one or more periodic noise signals as the characteristic frequency of the periodic noise signals in the mud signal.

13. The MWD system noise cancellation device according to claim 12, wherein the receiving the acquired mud signal and determining the characteristic frequency of the periodic noise signal in the mud signal comprises:

receiving the collected mud signals;

when any periodic noise signal cannot be acquired, determining the central frequency of the periodic noise signal in the mud signal as the characteristic frequency of the periodic noise signal in the mud signal according to the frequency spectrum of the mud signal.

14. The MWD system noise cancellation arrangement of claim 10,

the mud signal is: s_in＝[s_in(n) s_in(n+1) … s_in(n+K-1)]^T(ii) a Wherein s is_in(n) denotes the mud signal, s_inRepresenting an input mud signal vector, K being the length of the input signal vector, n representing the starting sequence number of the input signal;

before the fourier transform of the mud signal is performed to obtain a frequency domain mud signal, the processor further performs the following operations:

inputting the mud signal into a mud signal buffer to obtain the mud signal bufferMud signal s of_b：

s_b＝[s_in(n-M) … s_in(n-2) s_in(n-1) s_in]^TThe length of each mud signal buffer is N, and N is K + M.

15. The MWD system noise cancellation arrangement of claim 11,

the pumping signal is: p is a radical of_in＝[p_in(n) p_in(n+1) … p_in(n+K-1)]^T；

Wherein p is_inRepresenting the input pumping signal vector, K being the length of the input signal vector, and n representing the starting sequence number of the input signal.

16. The MWD system noise cancellation device according to claim 15, wherein the inputting the pumping signal to a pumping signal buffer when the inputted pumping signal can be acquired comprises:

when the input pumping signal can be acquired, inputting the pumping signal into a pumping signal buffer to acquire a pumping signal p in the pumping signal buffer_b：

p_b＝[p_in(n-M) … p_in(n-2) p_in(n-1)p_in]^T；

The length of each pump signal buffer is N, and N is K + M.

17. The MWD system noise cancellation device according to claim 16, wherein the determining the average pumping frequency derived from the pumping signal in the pumping signal buffer as the characteristic frequency of the periodic noise signal in the mud signal comprises:

calculating to obtain the average pumping frequency of the pumping signal in the pumping signal buffer according to the time corresponding to the rising edge of the pumping signal in the pumping signal buffer and an average pumping frequency calculation formula;

determining the average pumping frequency of the obtained pumping signal as the characteristic frequency of a periodic noise signal in the mud signal;

wherein, the average pump stroke frequency calculation formula comprises:

pump signal p in a pump signal buffer_bComprises L +1 rising edges, and the corresponding time of the rising edge is t_k,k＝0,1,2,...,L；

Represents the average pumping frequency; t is t_kL +1 represents the number of rising edges at the time corresponding to the rising edge.

18. The MWD system noise cancellation device according to claim 14, wherein the fourier transforming the mud signal to obtain a frequency domain mud signal comprises:

windowing the mud signal in the mud signal buffer to obtain a windowed mud signal;

and carrying out Fourier transform on the windowed mud signal to obtain a frequency domain mud signal.

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