CN102053265B - Filtering method for eliminating wild value of seismic data - Google Patents

Abstract

The invention belongs to the field for carrying out signal processing to seismic data in the seismic geological field, in particular to a method for effectively eliminating a wild value signal in signals. The invention adopts a seismic complex-trace filtering method and comprises the steps of concerting and decomposing a seismic data signal, carrying out smooth filtering, and reconstructing instantaneous envelopment subjected to smooth filtering and a wave-phase function of an original signal to eliminate an output signal of the wild value wave.

Description

A kind of filtering method to the wild value of earthquake document weeding

Technical field

The invention belongs to the field of in seismogeology field, seismic data being carried out signal processing, relate in particular to a kind of method of wild value signal in signal being carried out to effective rejecting.

Background technology

In seismic data, the frequency of wild value signal and phase place are uncertain, and it may be Fourier (cyclic swing) signal, may be also small echo (fluctuation non-periodic) signals.Therefore, all produce little effect concerning rejecting wild value for the various filtering methods of frequency and phase place.Unique feature of wild value signal is that its relative amplitude is very big, and still, the amplitude threshold of wild value cannot be determined equally.Adopt separately smothing filtering (as medium filtering) can effectively pick wild value, but, concerning other Fourier signal, but may the frequency of occurrences or phase distortion.The wild value of prior art automatic rejection in real number road is very difficult, and at present, each seismic data processing system has the function of the wild value of automatic rejection, but its effect is all undesirable, all cannot effectively reject frequency or phase distortion that wild value does not produce signal simultaneously.

Summary of the invention

The present invention, in order to solve the technical matters existing in prior art, has researched and developed the method for the wild value of a kind of complex trace rejecting, and the method can effectively be rejected wild value, and retains frequency and the phase place of significant wave signal and wild value signal, and phenomenon that seismic trace signal is undistorted occurs.

The method applied in the present invention is to reject and filtering for the wild value signal existing in seismic data signal, and retains frequency and the phase place of significant wave signal and wild value signal; The present invention adopts the method for earthquake complex trace filtering, comprise earthquake data signal is carried out to signal conversion and decomposition step and smothing filtering step, and the instantaneous envelope after smothing filtering and the reconstruct of original signal wave phase function are obtained rejecting the output signal of wild value ripple.

Specifically, the inventive method comprises the steps,

1.. the input of seismic data signal;

2.. input signal is decomposed in conversion: adopt Hilbert transform decomposition method

3.. instantaneous envelope smothing filtering step;

4.. by filtered instantaneous envelope and the reconstruct of original phase function output signal:

Be that reconstruction step is the long-pending of filtered instantaneous envelope a (t) and original phase function cos θ (t):

y _r(t)＝cosθ(t)·a(t)

Wherein, y _r(t) for rejected wild value and without the final output of phase place and frequency distortion.

Wherein, in described step 2, adopt Hilbert transform decomposition method to be

Real function x _r(t) Hilbert transform is x _h(t);

$x_h\left(t\right)=\frac{1}{\mathrm{\π}}{\∫}_{-\∞}^{+\∞}\frac{x_r\left(\mathrm{\τ}\right)}{t-\mathrm{\τ}}\mathrm{d\τ}=x_r\left(t\right)*\frac{1}{\mathrm{\πt}}$

In formula: t is time series, * is convolution;

Instantaneous envelope: $a\left(t\right)=\sqrt{x_r^2\left(t\right)+x_h^2\left(t\right)};$ Phase function is: $\cos \mathrm{\θ}\left(t\right)=\frac{x_r\left(t\right)}{a\left(t\right)};$

So: x _r(t)=cos θ (t) a (t)

Real function x _r(t) be broken down into the long-pending of phase function cos θ (t) and instantaneous envelope a (t);

The amplitude of instantaneous envelope a (t) reflected signal changes, with phase place and the frequency-independent of signal; Phase place and the frequency of cos θ (t) reflected signal, irrelevant with the amplitude of signal.

In wherein said step 3, adopt smothing filtering step for instantaneous envelope a (t) is implemented to smothing filtering

a(t)＝smooth{a(t)}

In formula, smooth is smothing filtering; Described smothing filtering is median filter method.

A (t) is filtered output; Can not cause phase place and the frequency distortion of signal to instantaneous envelope enforcement smothing filtering.

Brief description of the drawings

Fig. 1 is the schematic flow sheet of the inventive method;

Fig. 2 is the real signal road figure that has wild value;

Fig. 3 adopts medium filtering directly the design sketch after smothing filtering to be implemented in the real signal road of Fig. 2;

Fig. 4 is that the real signal road that the present invention is directed to Fig. 2 carries out Hilbert transform, obtains instantaneous envelope a (t) figure;

Fig. 5 is that the real signal road that the present invention is directed to Fig. 2 carries out Hilbert transform, obtains phase function cos θ (t) figure;

Fig. 6 the present invention is directed to the instantaneous envelope a of Fig. 4 (t) to make medium filtering, obtains instantaneous envelope a (t) figure after smothing filtering;

Fig. 7 is the last reconstruct output signal of the present invention y _r(t) figure;

Fig. 8 is the Yi Ge CMP road collection figure in a certain oil-gas exploration of embodiment of the present invention work area;

Fig. 9 is the picture arc phenomenon appearance figure that in embodiment, wild value signal wherein causes pre-stack time migration imaging section;

Figure 10 is that embodiment adopts the present invention to rejecting the Output rusults figure of wild value shown in Fig. 8;

Figure 11 is that the picture arc phenomenon disappearance that embodiment rejects the pre-stack time migration imaging section being caused by wild value signal after wild value signal is schemed.

Above-mentioned each width accompanying drawing is illustrated in connection with summary of the invention and embodiment.

Embodiment

Fig. 1 is the schematic flow sheet of the inventive method, in figure, first adopt Hilbert transform decomposition method, be instantaneous envelope and phase function by seismic data signal decomposition, then implement smothing filtering step for instantaneous envelope, finally by filtered instantaneous envelope and the reconstruct of original phase function output signal.

Exist the real signal road of wild value as Fig. 2, first adopt medium filtering directly smothing filtering to be implemented in this signal road, result as shown in Figure 3, although wild value signal is disallowable,, all there is distortion (scabbling) phenomenon in the crest of other signal and trough.

Use this technology, real signal road to Fig. 2 carries out Hilbert transform, obtain instantaneous envelope a (t), as shown in Figure 4 with phase function cos θ (t) as shown in Figure 5, make medium filtering for instantaneous envelope a (t), obtain the instantaneous envelope a (t) after smothing filtering, see Fig. 6, last reconstruct output y _r(t) Fig. 7.

As shown in Figure 7, the amplitude of wild value signal is subject to effective compacting, and distortion phenomenon does not all occur for the crest of other signal and trough.Retaining under the frequency of wild value signal and the prerequisite of phase characteristic, suppress its amplitude, instead of excise simply it.

Fig. 8 is the Yi Ge CMP road collection in oil-gas exploration work area, and wild value signal is wherein high-visible, and these wild value signals cause that the picture arc phenomenon of pre-stack time migration imaging section occurs, shown in Fig. 9.Therefore, must before migration imaging, reject wild value, guarantee imaging effect.

Figure 10 uses the Output rusults of this technology to the wild value of Fig. 8 automatic rejection, and after this Output rusults again migration imaging, the picture arc phenomenon being caused by open country value disappears, as shown in figure 11.

Technique scheme is one embodiment of the present invention, for those skilled in the art, the invention discloses on the basis of application process and principle, be easy to make various types of improvement or distortion, and be not limited only to the described structure of the above-mentioned embodiment of the present invention, therefore previously described mode is preferably, and does not have restrictive meaning.

Claims (4)

1. the filtering method to the wild value of earthquake document weeding, is characterized in that, described method is rejected and filtering for the wild value signal existing in seismic data signal, and retains frequency and the phase place of significant wave signal and wild value signal; The method that adopts the filtering of earthquake complex trace, comprises earthquake data signal is carried out to signal conversion and decomposition step and smothing filtering step, and the instantaneous envelope after smothing filtering and the reconstruct of original signal wave phase function are obtained rejecting the output signal of wild value ripple;

Described filtering method comprises,

1.. the input of seismic data signal;

2.. input signal is decomposed in conversion: adopt Hilbert transform decomposition method;

3.. instantaneous envelope smothing filtering step;

4.. by filtered instantaneous envelope and the reconstruct of original phase function output signal:

Be that reconstruction step is filtered instantaneous envelope long-pending with original phase function cos θ (t):

$y_r\left(t\right)=\cos \mathrm{\θ}\left(t\right)\·\stackrel{\‾}{a\left(t\right)}$

Wherein, y _r(t) for rejected wild value and without the final output of phase place and frequency distortion.

2. a kind of filtering method to the wild value of earthquake document weeding according to claim 1, is characterized in that,

In described step 2, adopt Hilbert transform decomposition method to be

Real function x _r(t) Hilbert transform is x _h(t);

$x_h\left(t\right)=\frac{1}{\mathrm{\π}}{\∫}_{-\∞}^{+\∞}\frac{x_r\left(\mathrm{\τ}\right)}{t-\mathrm{\τ}}\mathrm{d\τ}=x_r\left(t\right)*\frac{1}{\mathrm{\πt}}$

In formula: t is time series, * is convolution;

Instantaneous envelope: $a\left(t\right)=\sqrt{x_r^2\left(t\right)+x_h^2\left(t\right)};$ Phase function is: $\cos \mathrm{\θ}\left(t\right)=\frac{x_r\left(t\right)}{a\left(t\right)};$

So: x _r(t)=cos θ (t) a (t)

Real function x _r(t) be broken down into the long-pending of phase function cos θ (t) and instantaneous envelope a (t);

The amplitude of instantaneous envelope a (t) reflected signal changes, with phase place and the frequency-independent of signal; Phase place and the frequency of cos θ (t) reflected signal, irrelevant with the amplitude of signal.

3. a kind of filtering method to the wild value of earthquake document weeding according to claim 1 and 2, is characterized in that,

In described step 3, adopt smothing filtering step for instantaneous envelope a (t) is implemented to smothing filtering

$\stackrel{\‾}{a\left(t\right)}=\mathrm{smooth}\left\{a\left(t\right)\right\}$

In formula, smooth is smothing filtering; filtered output; Can not cause phase place and the frequency distortion of signal to instantaneous envelope enforcement smothing filtering.

4. a kind of filtering method to the wild value of earthquake document weeding according to claim 3, is characterized in that, described smothing filtering is median filter method.