CN102565865A - Method and device for obtaining noise-reducing NMR (Nuclear Magnetic Resonance) logging echo signal - Google Patents

Abstract

The invention provides a method and device for obtaining a noise-reducing NMR (Nuclear Magnetic Resonance) logging echo signal. The method comprises the following steps: a received NMR logging echo signal can be converted into a digital echo signal by an AD (Analog-to-Digital) converting unit; the digital echo signal is subjected to delay processing by a delay module, and thus a delayed digital echo signal can be obtained; the delayed digital echo signal is subjected to filter processing by an FIR (Finite Impulse Response) filter, and thus a filtered echo signal can be obtained; the filtered echo signal is subjected to FFT (Fast Fourier Transform) processing by an FFT unit, and thus a frequency domain filtered echo signal can be obtained; the frequency domain filtered echo signal is subjected to phase correction by a phase correction unit according to the digital echo signal obtained by a counter, and thus a phase correction filtered echo signal can be obtained; and the phase correction filtered echo signal is subjected to IFFT (Inverse Fast Fourier Transform) processing by an IFFT unit, and thus the noise-reducing NMR logging echo signal can be obtained. According to the scheme, the problem of phase drift generated in a filtering process is removed.

Description

The preparation method and the device of noise reduction nuclear magnetic resonance log echoed signal

Technical field

The present invention relates to the nuclear magnetic resonance log technology, relate in particular to a kind of preparation method and device of noise reduction nuclear magnetic resonance log echoed signal.

Background technology

At petroleum exploration field, (Nuclear Magnetic Resonance, NMR) because magnetic field intensity is lower, spin echo signal is faint, usually is submerged in the noise for low-field nuclear magnetic resonance.In order to obtain desirable spin echo signal, must carry out noise reduction process to the spin echo signal that collects.

At present, generally adopt filtering technique that spin echo signal is carried out noise reduction process.Strengthen based on the self-adaptation spectral line of auto adapted filtering that (Adapitive Line Enhancement, ALE) technology is a kind of denoise processing method of novel actual effect.In the sef-adapting filter design of ALE, there is not external reference signal to utilize.Because the narrow band signal cycle is obvious, broadband noise is periodically poor, postpone a period of time after the related function of narrow band signal can be better than this characteristic of broadband noise significantly, original input signal is inserted lag line signal as a reference with fixed delay.Therefore; The suitable time delay of choosing, the broadband noise correlativity of the broadband noise of reference signal and original input will weaken rapidly, and the correlativity of narrow band cycle signal can not be affected; So can realize the effect of filtering noise reduction preferably; But owing to chosen time delay, therefore there is the problem of phase drift in filtered echoed signal.

Summary of the invention

The present invention provides a kind of preparation method and device of noise reduction nuclear magnetic resonance log echoed signal, strengthens the echoed signal phase drift problem that exists in the filtering technique in order to solve existing self-adaptation spectral line.

The preparation method of a kind of noise reduction nuclear magnetic resonance log echoed signal provided by the invention comprises:

AD conversion unit receives the nuclear magnetic resonance log echoed signal, and said nuclear magnetic resonance log echoed signal is converted into digital echo signal;

Postponement module receives said digital echo signal, and said digital echo signal is carried out delay process, to obtain the time-delay digital echo signal;

Limited unit impulse response (Finite Impulse response, FIR) wave filter receives said time-delay digital echo signal, and said time-delay digital echo signal is carried out Filtering Processing, to obtain filtering echoed signal;

Fast fourier transform unit receives said filtering echoed signal, and said filtering echoed signal is carried out FFT handle, to obtain frequency field filtering echoed signal;

The phase correction unit carry out phase correction according to the time-delay number of the said digital echo signal that counter obtains to said frequency field filtering echoed signal, to obtain phase correction filtering echoed signal;

The inverse fast fourier transform unit receives said phase correction filtering echoed signal, and said phase correction filtering echoed signal is carried out inverse fast fourier transform handle, to obtain noise reduction nuclear magnetic resonance log echoed signal.

The preparation method of aforesaid noise reduction nuclear magnetic resonance log echoed signal wherein, also comprises:

Error calculation unit is poor to said digital echo signal and said filtering echoed signal, to obtain error;

The filter coefficient unit obtains filter coefficient according to the step-length of said error and the output of step-length control module, and comes the filter coefficient in said limited next filtering cycle of unit impulse response filter is upgraded with this filter coefficient.

The preparation method of aforesaid noise reduction nuclear magnetic resonance log echoed signal, wherein,

The step-length of said step-length control module output is expressed as:

μ(k)＝1/(2x ^T(k)x(k))；

Wherein,

μ (k) is a k step-length constantly;

X (k) sample sequence;

x ^T(k) be the transposition of sample sequence;

k＝0，1，...，N-1；

N is a filter order, and N is a natural number.

The preparation method of aforesaid noise reduction nuclear magnetic resonance log echoed signal, wherein,

Said filter coefficient unit adopts following formula according to the step-length acquisition filter coefficient of said error and the output of step-length control module:

W(k+1)＝W(k)+[μ(k)e(k)x(k)]/[b+x ^T(k)x(k)]；

Wherein,

W (k) is a k filter coefficient;

W (k+1) is a k+1 filter coefficient;

E (k) is a k error constantly;

B is a constant;

μ (k) is a k step-length constantly;

X (k) sample sequence;

x ^T(k) be the transposition of sample sequence.

The preparation method of aforesaid noise reduction nuclear magnetic resonance log echoed signal, wherein, said fast fourier transform unit also comprises before receiving said filtering echoed signal:

Truncation carry out to the said filtering echoed signal of said limited unit impulse response filter output in the saturated unit that blocks.

The preparation method of aforesaid noise reduction nuclear magnetic resonance log echoed signal, wherein, said fast fourier transform unit is carried out FFT to said filtering echoed signal and is handled the following formula of employing:

$D^{\′}\left(k\right)=\mathrm{DFT}\left[y^{\′\′}\left(n\right)\right]=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}{y}^{\′\′}\left(n\right)\exp (-j\frac{2\mathrm{\π}}{N}\mathrm{nk});$

Wherein,

D ' is n data y of time domain behind the noise reduction (k) " (n) through k corresponding behind Fourier transform frequency domain data;

D (k) is a k frequency domain data behind the phase correction;

J is an imaginary unit;

k＝0，1，...，N-1；

n＝0，1，...，N-1；

N is a sampling number, and N is a natural number.

The preparation method of aforesaid noise reduction nuclear magnetic resonance log echoed signal; Wherein, the time-delay number of the said digital echo signal that obtains according to counter of said phase correction unit is carried out phase correction to said frequency field filtering echoed signal and is adopted following formula:

$D\left(k\right)=D^{\′}\left(k\right)\×\exp \left(j\frac{2\mathrm{\π}}{N}\mathrm{mk}\right);$

Wherein,

D (k) is n data y of time domain behind the noise reduction " (n) through the data behind k corresponding behind the Fourier transform frequency domain data phase correction;

D ' is n data y of time domain behind the noise reduction (k) " (n) through k corresponding behind Fourier transform frequency domain data;

M is for postponing number;

k＝0，1，...，N-1；

n＝0，1，...，N-1；

N is a sampling number, and N is a natural number.

The preparation method of aforesaid noise reduction nuclear magnetic resonance log echoed signal, wherein, said inverse fast fourier transform unit carries out inverse fast fourier transform to said phase correction filtering echoed signal and handles the following formula of employing:

$y\left(n\right)=\mathrm{IDFT}\left[D\left(k\right)\right]=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}D\left(k\right)\exp \left(j\frac{2\mathrm{\π}}{N}\mathrm{nk}\right);$

Wherein,

Y (n) is a noise reduction nuclear magnetic resonance log echoed signal;

N is a sampling number, and N is a natural number;

D (k) is n data y of time domain behind the noise reduction " (n) through the data behind k corresponding behind the Fourier transform frequency domain data phase correction;

k＝0，1，...，N-1；

n＝0，1，...，N-1。

The present invention also provides a kind of nuclear magnetic resonance log echoed signal denoising device, comprising:

AD conversion unit is used to receive the nuclear magnetic resonance log echoed signal, and said nuclear magnetic resonance log echoed signal is converted into digital echo signal;

Postponement module is used to receive said digital echo signal, and said digital echo signal is carried out delay process, to obtain the time-delay digital echo signal;

Limited unit impulse response filter is used to receive said time-delay digital echo signal, and said time-delay digital echo signal is carried out Filtering Processing, to obtain filtering echoed signal;

Fast fourier transform unit is used to receive said filtering echoed signal, and said filtering echoed signal is carried out FFT handle, to obtain frequency field filtering echoed signal;

The phase correction unit, the time-delay number of the said digital echo signal that is used for obtaining according to counter carry out phase correction to said frequency field filtering echoed signal, to obtain phase correction filtering echoed signal;

The inverse fast fourier transform unit is used to receive said phase correction filtering echoed signal, and said phase correction filtering echoed signal is carried out inverse fast fourier transform handle, to obtain noise reduction nuclear magnetic resonance log echoed signal.

Aforesaid nuclear magnetic resonance log echoed signal denoising device wherein, also comprises:

Error calculation unit, it is poor to be used for said digital echo signal and said filtering echoed signal, to obtain error;

The step-length control module is used to export step-length;

The filter coefficient unit is used for obtaining filter coefficient according to said error and said step-length, and comes the filter coefficient in said limited next filtering cycle of unit impulse response filter is upgraded with this filter coefficient.

Aforesaid nuclear magnetic resonance log echoed signal denoising device wherein, also comprises:

The saturated unit that blocks is used for the said filtering echoed signal of said limited unit impulse response filter output carry out truncation.

The preparation method and the device of noise reduction nuclear magnetic resonance log echoed signal provided by the invention; Adopt filtering echoed signal is carried out FFT through fast fourier transform unit; Make filtering echoed signal be transformed to the filtering echoed signal of frequency field by the time domain echoed signal, then, frequency field filtering echoed signal is handled through the phase correction unit; Multiply by preset linear phase compensating factor; Thereby compensate the phase drift that causes because of the noise reduction time-delay in frequency field, to obtain phase correction filtering echoed signal, afterwards; Through the inverse fast fourier transform unit phase correction filtering echoed signal is carried out inverse fast fourier transform again and handle, to obtain noise reduction nuclear magnetic resonance log echoed signal.Therefore the echoed signal after above-mentioned filtering noise reduction process has been eliminated the problem of phase drift.

Description of drawings

Fig. 1 is the process flow diagram of the preparation method embodiment of noise reduction nuclear magnetic resonance log echoed signal of the present invention;

Fig. 2 is the structural representation of nuclear magnetic resonance log echoed signal denoising device embodiment of the present invention;

Fig. 3 is the structural representation of another embodiment of nuclear magnetic resonance log echoed signal denoising device of the present invention;

Fig. 4 is the structural representation of the another embodiment of nuclear magnetic resonance log echoed signal denoising device of the present invention.

Embodiment

Fig. 1 is the process flow diagram of the preparation method embodiment of noise reduction nuclear magnetic resonance log echoed signal of the present invention; As shown in Figure 1, the embodiment of the preparation method of noise reduction nuclear magnetic resonance log echoed signal of the present invention may further comprise the steps:

Step 1: AD conversion unit receives the nuclear magnetic resonance log echoed signal, and said nuclear magnetic resonance log echoed signal is converted into digital echo signal;

The nuclear magnetic resonance log echoed signal that directly obtains in the nuclear magnetic resonance log process is a simulating signal; And be digital circuit at the circuit that the nuclear magnetic resonance log echoed signal is carried out follow-up Filtering Processing; Therefore; Need to adopt the analog-to-digital conversion unit that the nuclear magnetic resonance log echoed signal that receives is carried out analog-to-digital conversion, to obtain digital echo signal.

Step 2: Postponement module receives said digital echo signal, and said digital echo signal is carried out delay process, to obtain the time-delay digital echo signal;

Step 3: limited unit impulse response filter receives said time-delay digital echo signal, and said time-delay digital echo signal is carried out Filtering Processing, to obtain filtering echoed signal;

In this embodiment; FIR wave filter employing floating-point normalization minimum mean-square difference algorithm (Normalized Least Mean Square NLMS) carries out Filtering Processing to digital echo signal, and; Through this floating-point normalization minimum mean-square difference algorithm real-time regulated filter parameter; And need not know the priori of noise, can be in the faint NMR spin echo signal of extraction amplitude under the strong noise background (that is nuclear magnetic resonance log echoed signal); Thereby realize the purpose of compacting noise, to improve filter effect.

Step 4: fast fourier transform unit receives said filtering echoed signal, and said filtering echoed signal is carried out FFT handle, to obtain frequency field filtering echoed signal;

Step 5: the phase correction unit carry out phase correction according to the time-delay number of the said digital echo signal that counter obtains to said frequency field filtering echoed signal, to obtain phase correction filtering echoed signal;

Step 6: the inverse fast fourier transform unit receives said phase correction filtering echoed signal, and said phase correction filtering echoed signal is carried out inverse fast fourier transform handle, to obtain noise reduction nuclear magnetic resonance log echoed signal.

Fast fourier transform unit and inverse fast fourier transform unit can adopt field programmable gate array (Field-Programmable Gate Array, FPGA) digital signal processing (Digital Signal Processing, the DSP) computing unit of inside.Adopt FPGA to utilize its good sequential control function and net synchronization capability here, and have a large amount of programming device gate circuits, realize each circuit function flexibly through modularization programming.

Such scheme carries out FFT with filtering echoed signal through fast fourier transform unit, makes filtering echoed signal be transformed to the frequency field filtering echoed signal of frequency field by the time domain echoed signal; Then; Frequency field filtering echoed signal is handled through the phase correction unit, multiply by preset linear phase compensating factor, thereby compensates the phase drift that causes because of the noise reduction time-delay in frequency field; To obtain phase correction filtering echoed signal; Afterwards, through the inverse fast fourier transform unit phase correction filtering echoed signal is carried out inverse fast fourier transform again and handle, to obtain noise reduction nuclear magnetic resonance log echoed signal.Therefore the echoed signal after above-mentioned filtering noise reduction process has been eliminated the problem of phase drift.

Further, based on the foregoing description, also comprise:

Error calculation unit is poor to said digital echo signal and said filtering echoed signal, to obtain error;

The filter coefficient unit obtains filter coefficient according to the step-length of said error and the output of step-length control module, and comes the filter coefficient in said limited next filtering cycle of unit impulse response filter is upgraded with this filter coefficient.

Pass through said method; Filter coefficient to the FIR wave filter carries out the adaptivity renewal; Promptly; Calculate the filter coefficient that the Error Calculation that obtains makes new advances according to the step-length of the NLMS algorithm computation in current filtering cycle and error calculation unit, and this new filter coefficient is passed to the FIR wave filter to participate in the filtering operation in next filtering cycle, with the raising filter effect.And when NLMS algorithm iteration number of times equaled the sampling number of nuclear magnetic resonance log, filter coefficient was changed to 1, and the iterative computation filter coefficient of next time sampling again.

Further, based on the foregoing description, the step-length of step-length control module output is expressed as:

μ(k)＝1/(2x ^T(k)x(k))；

Wherein, μ (k) is a k step-length constantly; X (k) sample sequence; x ^T(k) be the transposition of sample sequence; K=0,1 ..., N-1; N is a filter order, and N is a natural number.

Further, based on the foregoing description, the filter coefficient unit adopts following formula according to the step-length acquisition filter coefficient of said error and the output of step-length control module:

W(k+1)＝W(k)+[μ(k)e(k)x(k)]/[b+x ^T(k)x(k)]；

Wherein, W (k) is a k filter coefficient; W (k+1) is a k+1 filter coefficient; E (k) is a k error constantly; B is a constant; μ (k) is a k step-length constantly; X (k) sample sequence; x ^T(k) be the transposition of sample sequence.

Further, based on the foregoing description, said fast fourier transform unit also comprises before receiving said filtering echoed signal:

Truncation carry out to the said filtering echoed signal of said limited unit impulse response filter output in the saturated unit that blocks.

Keep the output length of FIR wave filter consistent through truncation with sampling length; Promptly be stored in RAS (the random access memory of FIR wave filter; RAM) last one output of filtering constantly in is transferred to the saturated unit that blocks and carries out truncation, and the signal after blocking is filtering echoed signal.

Further, based on the foregoing description, fast fourier transform unit is carried out FFT to said filtering echoed signal and is handled the following formula of employing:

$D^{\′}\left(k\right)=\mathrm{DFT}\left[y^{\′\′}\left(n\right)\right]=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}{y}^{\′\′}\left(n\right)\exp (-j\frac{2\mathrm{\π}}{N}\mathrm{nk});$

Wherein, D ' is n data y of time domain behind the noise reduction (k) " (n) through k corresponding behind Fourier transform frequency domain data; D (k) is a k frequency domain data behind the phase correction; J is an imaginary unit; K=0,1 ..., N-1; N=0,1 ..., N-1; N is a sampling number, and N is a natural number.

Further, based on the foregoing description, the phase correction unit carries out phase correction according to the time-delay number of the said digital echo signal of counter acquisition to said frequency field filtering echoed signal and adopts following formula:

$D\left(k\right)=D^{\′}\left(k\right)\×\exp \left(j\frac{2\mathrm{\π}}{N}\mathrm{mk}\right);$

Wherein, D (k) is n data y of time domain behind the noise reduction " (n) through the data behind k corresponding behind the Fourier transform frequency domain data phase correction; D ' is n data y of time domain behind the noise reduction (k) " (n) through k corresponding behind Fourier transform frequency domain data; M is for postponing number; K=0,1 ..., N-1; N=0,1 ..., N-1; N is a sampling number, and N is a natural number.

Further, based on the foregoing description, the inverse fast fourier transform unit carries out inverse fast fourier transform to said phase correction filtering echoed signal and handles the following formula of employing:

$y\left(n\right)=\mathrm{IDFT}\left[D\left(k\right)\right]=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}D\left(k\right)\exp \left(j\frac{2\mathrm{\π}}{N}\mathrm{nk}\right);$

Wherein, y (n) is a noise reduction nuclear magnetic resonance log echoed signal; N is a sampling number, and N is a natural number; D (k) is n data y of time domain behind the noise reduction " (n) through the data behind k corresponding behind the Fourier transform frequency domain data phase correction; K=0,1 ..., N-1; N=0,1 ..., N-1.

One of ordinary skill in the art will appreciate that: all or part of step that realizes above-mentioned each method embodiment can be accomplished through the relevant hardware of programmed instruction.Aforesaid program can be stored in the computer read/write memory medium.This program the step that comprises above-mentioned each method embodiment when carrying out; And aforesaid storage medium comprises: various media that can be program code stored such as ROM, RAM, magnetic disc or CD.

Fig. 2 is the structural representation of nuclear magnetic resonance log echoed signal denoising device embodiment of the present invention; As shown in Figure 2; The embodiment of nuclear magnetic resonance log echoed signal denoising device of the present invention comprises AD conversion unit 21, Postponement module 22, limited unit impulse response filter 23, fast fourier transform unit 24, phase correction unit 25 and inverse fast fourier transform unit 26.

Particularly, AD conversion unit 21 is used to receive the nuclear magnetic resonance log echoed signal, and said nuclear magnetic resonance log echoed signal is converted into digital echo signal; Postponement module 22 is used to receive said digital echo signal, and said digital echo signal is carried out delay process, to obtain the time-delay digital echo signal; Limited unit impulse response filter 23 is used to receive said time-delay digital echo signal, and said time-delay digital echo signal is carried out Filtering Processing, to obtain filtering echoed signal; Fast fourier transform unit 24 is used to receive said filtering echoed signal, and said filtering echoed signal is carried out FFT handle, to obtain frequency field filtering echoed signal; Phase correction unit 25 is used for according to the time-delay number of the said digital echo signal of counter acquisition said frequency field filtering echoed signal carry out phase correction, to obtain phase correction filtering echoed signal; Inverse fast fourier transform unit 26 is used to receive said phase correction filtering echoed signal, and said phase correction filtering echoed signal is carried out inverse fast fourier transform handle, to obtain noise reduction nuclear magnetic resonance log echoed signal.

The function and the treatment scheme of each module in the nuclear magnetic resonance log echoed signal denoising device that present embodiment provides can be referring to above-mentioned method embodiment shown in Figure 1, and its realization principle and technique effect are similar, repeat no more here.

Further; Based on the foregoing description; As shown in Figure 3; Another embodiment of invention nuclear magnetic resonance log echoed signal denoising device, AD conversion unit 21, Postponement module 22, limited unit impulse response filter 23, fast fourier transform unit 24, phase correction unit 25 and inverse fast fourier transform unit 26 except comprising the foregoing description also comprise error calculation unit 27, step-length control module 28 and filter coefficient unit 29.

It is poor that error calculation unit 27 is used for said digital echo signal and said filtering echoed signal, to obtain error; Step-length control module 28 is used to export step-length; Filter coefficient unit 29 is used for obtaining filter coefficient according to said error and said step-length, and comes the filter coefficient in said limited next filtering cycle of unit impulse response filter is upgraded with this filter coefficient.

Further; Based on the foregoing description; As shown in Figure 4; The another embodiment of invention nuclear magnetic resonance log echoed signal denoising device, AD conversion unit 21, Postponement module 22, limited unit impulse response filter 23, fast fourier transform unit 24, phase correction unit 25 and inverse fast fourier transform unit 26, error calculation unit 27, step-length control module 28 and filter coefficient unit 29 except comprising the foregoing description also comprise the saturated unit 30 that blocks.

The saturated unit 30 that blocks is used for the said filtering echoed signal of said limited unit impulse response filter output carry out truncation.

What should explain at last is: above each embodiment is only in order to explaining technical scheme of the present invention, but not to its restriction; Although the present invention has been carried out detailed explanation with reference to aforementioned each embodiment; Those of ordinary skill in the art is to be understood that: it still can be made amendment to the technical scheme that aforementioned each embodiment put down in writing, perhaps to wherein part or all technical characteristic are equal to replacement; And these are revised or replacement, do not make the scope of the essence disengaging various embodiments of the present invention technical scheme of relevant art scheme.

Claims (11)

1. the preparation method of a noise reduction nuclear magnetic resonance log echoed signal is characterized in that, comprising:

AD conversion unit receives the nuclear magnetic resonance log echoed signal, and said nuclear magnetic resonance log echoed signal is converted into digital echo signal;

Postponement module receives said digital echo signal, and said digital echo signal is carried out delay process, to obtain the time-delay digital echo signal;

Limited unit impulse response filter receives said time-delay digital echo signal, and said time-delay digital echo signal is carried out Filtering Processing, to obtain filtering echoed signal;

Fast fourier transform unit receives said filtering echoed signal, and said filtering echoed signal is carried out FFT handle, to obtain frequency field filtering echoed signal;

The phase correction unit carry out phase correction according to the time-delay number of the said digital echo signal that counter obtains to said frequency field filtering echoed signal, to obtain phase correction filtering echoed signal;

The inverse fast fourier transform unit receives said phase correction filtering echoed signal, and said phase correction filtering echoed signal is carried out inverse fast fourier transform handle, to obtain noise reduction nuclear magnetic resonance log echoed signal.

2. the preparation method of noise reduction nuclear magnetic resonance log echoed signal according to claim 1 is characterized in that, also comprises:

Error calculation unit is poor to said digital echo signal and said filtering echoed signal, to obtain error;

The filter coefficient unit obtains filter coefficient according to the step-length of said error and the output of step-length control module, and comes the filter coefficient in said limited next filtering cycle of unit impulse response filter is upgraded with this filter coefficient.

3. the preparation method of noise reduction nuclear magnetic resonance log echoed signal according to claim 2 is characterized in that,

The step-length of said step-length control module output is expressed as:

μ(k)＝1/(2x ^T(k)x(k))；

Wherein,

μ (k) is a k step-length constantly;

X (k) sample sequence;

x ^T(k) be the transposition of sample sequence;

k＝0，1，...，N-1；

N is a filter order, and N is a natural number.

4. according to the preparation method of claim 2 or 3 described noise reduction nuclear magnetic resonance log echoed signals, it is characterized in that,

Said filter coefficient unit adopts following formula according to the step-length acquisition filter coefficient of said error and the output of step-length control module:

W(k+1)＝W(k)+[μ(k)e(k)x(k)]/[b+x ^T(k)x(k)]；

Wherein,

W (k) is a k filter coefficient;

W (k+1) is a k+1 filter coefficient;

E (k) is a k error constantly;

B is a constant;

μ (k) is a k step-length constantly;

X (k) sample sequence;

x ^T(k) be the transposition of sample sequence.

5. according to the preparation method of claim 1 or 2 or 3 described noise reduction nuclear magnetic resonance log echoed signals, it is characterized in that said fast fourier transform unit also comprises before receiving said filtering echoed signal:

Truncation carry out to the said filtering echoed signal of said limited unit impulse response filter output in the saturated unit that blocks.

6. according to the preparation method of claim 1 or 2 or 3 described noise reduction nuclear magnetic resonance log echoed signals, it is characterized in that said fast fourier transform unit is carried out FFT to said filtering echoed signal and handled the following formula of employing:

$D^{\′}\left(k\right)=\mathrm{DFT}\left[y^{\′\′}\left(n\right)\right]=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}{y}^{\′\′}\left(n\right)\exp (-j\frac{2\mathrm{\π}}{N}\mathrm{nk});$

Wherein,

D ' is n data y of time domain behind the noise reduction (k) " (n) through k corresponding behind Fourier transform frequency domain data;

D (k) is a k frequency domain data behind the phase correction;

J is an imaginary unit;

k＝0，1，...，N-1；

n＝0，1，...，N-1；

N is a sampling number, and N is a natural number.

7. according to the preparation method of claim 1 or 2 or 3 described noise reduction nuclear magnetic resonance log echoed signals; It is characterized in that said phase correction unit carries out phase correction according to the time-delay number of the said digital echo signal of counter acquisition to said frequency field filtering echoed signal and adopts following formula:

$D\left(k\right)=D^{\′}\left(k\right)\×\exp \left(j\frac{2\mathrm{\π}}{N}\mathrm{mk}\right);$

Wherein,

D (k) is n data y of time domain behind the noise reduction " (n) through the data behind k corresponding behind the Fourier transform frequency domain data phase correction;

D ' is n data y of time domain behind the noise reduction (k) " (n) through k corresponding behind Fourier transform frequency domain data;

M is for postponing number;

k＝0，1，...，N-1；

n＝0，1，...，N-1；

N is a sampling number, and N is a natural number.

8. according to the preparation method of claim 1 or 2 or 3 described noise reduction nuclear magnetic resonance log echoed signals; It is characterized in that said inverse fast fourier transform unit carries out inverse fast fourier transform to said phase correction filtering echoed signal and handles the following formula of employing:

$y\left(n\right)=\mathrm{IDFT}\left[D\left(k\right)\right]=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}D\left(k\right)\exp \left(j\frac{2\mathrm{\π}}{N}\mathrm{nk}\right);$

Wherein,

Y (n) is a noise reduction nuclear magnetic resonance log echoed signal;

N is a sampling number, and N is a natural number;

D (k) is n data y of time domain behind the noise reduction " (n) through the data behind k corresponding behind the Fourier transform frequency domain data phase correction;

k＝0，1，...，N-1；

n＝0，1，...，N-1。

9. a nuclear magnetic resonance log echoed signal denoising device is characterized in that, comprising:

AD conversion unit is used to receive the nuclear magnetic resonance log echoed signal, and said nuclear magnetic resonance log echoed signal is converted into digital echo signal;

Postponement module is used to receive said digital echo signal, and said digital echo signal is carried out delay process, to obtain the time-delay digital echo signal;

Limited unit impulse response filter is used to receive said time-delay digital echo signal, and said time-delay digital echo signal is carried out Filtering Processing, to obtain filtering echoed signal;

Fast fourier transform unit is used to receive said filtering echoed signal, and said filtering echoed signal is carried out FFT handle, to obtain frequency field filtering echoed signal;

The phase correction unit, the time-delay number of the said digital echo signal that is used for obtaining according to counter carry out phase correction to said frequency field filtering echoed signal, to obtain phase correction filtering echoed signal;

The inverse fast fourier transform unit is used to receive said phase correction filtering echoed signal, and said phase correction filtering echoed signal is carried out inverse fast fourier transform handle, to obtain noise reduction nuclear magnetic resonance log echoed signal.

10. nuclear magnetic resonance log echoed signal denoising device according to claim 9 is characterized in that, also comprises:

Error calculation unit, it is poor to be used for said digital echo signal and said filtering echoed signal, to obtain error;

The step-length control module is used to export step-length;

The filter coefficient unit is used for obtaining filter coefficient according to said error and said step-length, and comes the filter coefficient in said limited next filtering cycle of unit impulse response filter is upgraded with this filter coefficient.

11. according to claim 9 or 10 described nuclear magnetic resonance log echoed signal denoising devices, it is characterized in that, also comprise:

The saturated unit that blocks is used for the said filtering echoed signal of said limited unit impulse response filter output carry out truncation.

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