CN1332225C - Method for eliminating linear and non-linear interference wave by using filtering operation at deep layer domain - Google Patents

Abstract

The present invention relates to a method for eliminating linear and nonlinear interference waves by utilizing depth field wave filtering. As for conventionally collected earthquake cannon collection data, data gaining is carried out on the collected cannon collection data, and the data is processed by path equalization in the spatial direction and by oscillation amplitude compensation in the time direction so that the data is suitable for wave equation processing; the cannon collection is processed by Fourier positive transformation and downward wave field extrapolation, so that the cannon collection is extrapolated from the ground surface to the reference surface; the cannon collection which extrapolates to the reference surface is processed by depth field filtering, the cannon collection of the reference plane after depth field wave filtering is inversely transformed in wave field extrapolation and fourier modes, and the cannon collection of the reference plane after depth field wave filtering is extrapolated from the reference surface to the ground surface. The present invention can effectively identifies linear and nonlinear interference waves on the complex near ground surface and eliminates linear and nonlinear interference waves by adopting depth field wave filtering.

Description

A kind of method that adopts Depth Domain filtering to eliminate linear and non-linear interference wave

Technical field

The present invention relates to the oil seismic exploration data processing technique, specifically is a kind of method that adopts Depth Domain filtering to eliminate seismologic record neutral line and non-linear interference wave.

Background technology

In field of seismic exploration, traditional signal is strengthened or the noise compact technique generally is to utilize signal to separate or prediction signal and noise in frequency (low pass, high pass or bandpass filtering), apparent velocity (FK filtering), polarised direction (polarization filtering) and the difference of statistical property aspects such as (random noise decay) with noise, and then signal or noise handled accordingly, these class methods are called the denoising method of data-driven.

Yet, increasingly sophisticated along with the survey area face of land and near surface seismic geological codition, various ground obstacles and near surface lithological change cause miscellaneous interference wave near the excitaton source, the dune ringing in desert, the seabed produce repeatedly or pegleg multiples, and the interference wave of various ground, oil-field development district and underground installation generation, linearity and non-linear interference wave that these complex near districts produce often show as in frequency, apparent velocity, the direction of propagation, polarised direction and statistical property aspect are difficult to come with the effective difference of reflected signal, therefore the denoising method of utilizing signal and the traditional data driving of noise variance in the data is burbling noise and signal fully, does not reach desirable denoising effect.

Summary of the invention

Technical matters to be solved by this invention provides a kind of method that can effectively discern the linearity and the non-linear interference wave of complex near generation and adopt Depth Domain filtering elimination linearity and non-linear interference wave.

The present invention adopts Depth Domain filtering to eliminate method linear and non-linear interference wave, and for the earthquake shot gather data of gathering, its concrete steps comprise,

(1) shot gather data is carried out the data gain, data are carried out trace equalization and carried out amplitude compensation along time orientation along direction in space, make data adapt to wave equation and handle;

(2) shot gather data is carried out Fourier direct transform and wave field extrapolation downwards, from the ground surface continuation to reference surface;

(3) continuation is carried out Depth Domain filtering to the shot gather data on the reference surface;

(4) to the filtered shot gather data of Depth Domain make progress wave field extrapolation and inverse fourier transform, from the reference surface continuation to ground surface;

(5) carry out data inverse gain, recover the original-shape of reflected signal, the seismic wave effectively of the be eliminated face of land and near surface interference wave also becomes figure.

The present invention after shot gather data gained, can select data are carried out space interpolation reducing spatial aliasing, thereby eliminate the incorrect continuation to the alias data when the spatial sampling of data is big at interval.

The present invention utilizes evanescent wave to count attenuate acoustic noise carrying out downwards and in the upward continuation process, selecting the phase shift operator of signal maintenance.

In the downward continuation process of the present invention, change the phase place of signal, do not change the amplitude of signal and discern noise.

The present invention in the process of upward continuation, the phase place of restoring signal.

The present invention explores resulting seismologic record for two dimension, adopts two-dimension fourier direct transform and inverse transformation.

The present invention explores resulting seismologic record for two dimension, and the phase shift operator that is adopted is in filtering advance row amplitude compensation and field statics.Should not destroy the earth's surface-consistent of record before the filtering to the processing of record.

The present invention's seismologic record that exploration obtains for three-dimensional, carry out three-dimensional Fourier direct transform and wave field extrapolation downwards, the phase shift operator automatically spreads to three-dimensional situation, carry out Depth Domain filtering after, carry out three-dimensional Fourier inverse transformation and upwards wave field extrapolation, promptly finished the filtering of three dimensional depth territory.

The present invention is with the two-dimension earthquake data instance, and the concrete principle of employing is:

The formula of evanescent wave number is

$\frac{{\mathrm{\ω}}^2}{c_n^2}-k_x^2=-{k_z}^2(k_z>0)$

The amplitude fading factor is e ^-kz

Observation wave field p (x, z t) meet following equation:

${\&dtri;}^{2}p(x,z,t)-\frac{1}{c^2\left(z\right)}\frac{{\&PartialD;}^{2}p(x,z,t)}{{\&PartialD;\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="C20041010264900131.png"\; state="\{\{state\}\}">t</figure-callout>}}^2}=0---\left(1\right)$

As near-surface velocity C (z) is only vertically to change, and near-surface model is discrete for thickness is Δ z, and speed is c _nN layer uniform dielectric, the x of equation (1) and t coordinate are used Fourier Tranform, can draw:

$\frac{{\&PartialD;}^2-P(k_x,z,\mathrm{\&omega;})}{{\&PartialD;z}^2}=(k_x^2-\frac{{\mathrm{\&omega;}}^2}{c_n^2})P(k_x,z,\mathrm{\&omega;})---\left(2\right)$

Defining vertical wave number is $k_z=\sqrt{\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2}$ , separating of equation (2) is exactly so:

$P(k_x,z,\mathrm{\&omega;})={\mathrm{Ae}}^{{\mathrm{ik}}_{z}z}+{\mathrm{Be}}^{{-\mathrm{ik}}_{z}z}---\left(3\right)$

Two coefficient A in the formula, B is determined by applied surface conditions.

Carry out the wave field downward continuation according to formula (3), formula is:

$P(k_x,z+\mathrm{\&Delta;z},\mathrm{\&omega;})=P(k_x,z,\mathrm{\&omega;})e^{{\mathrm{ik}}_z\mathrm{\&Delta;z}}---\left(4\right)$

$k_z=\left\{\begin{array}{cc}\sqrt{\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2}& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2\&GreaterEqual;0)\\ 0& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2<0)\end{array},---\left(5\right)\right.$

Carry out the wave field upward continuation according to formula (3), formula is:

$P(k_x,z-\mathrm{\&Delta;z},\mathrm{\&omega;})=P(k_x,z,\mathrm{\&omega;})e^{{\mathrm{ik}}_z\mathrm{\&Delta;z}}---\left(6\right)$

$k_z=\left\{\begin{array}{cc}\sqrt{\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2}& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2\&GreaterEqual;0)\\ \sqrt[i]{k_x^2-\frac{{\mathrm{\&omega;}}^2}{c_n^2}}& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2<0)\end{array}---\left(7\right)\right.$

The present invention is after taking all factors into consideration counting yield, adapting to aspect factors such as recording geometry ability and signal maintenance, employing is based on the model-driven denoising method of wave field extrapolation, the noise that compacting is associated with the evanescent wave number, eliminate the linear and non-linear interference of near surface, the amplitude and the phase information of holding signal can obtain glitch-free geological data fully.

Description of drawings

Fig. 1 is based on the model-driven filtering method synoptic diagram of wave field extrapolation, and after downward continuation and upward continuation, in the amplitude retaining zone, signal is constant, and in the phase place retaining zone, noise amplitude is pressed.

Fig. 2 is the near-surface model that contains a two layer medium and a scatterer, and wherein the scatterer yardstick is that 10m*10m, buried depth are that 100m, speed are 1500m/s, the speed c of two layer medium _nBe respectively 2500m/s and 3500m/s.Excite with receiving plane and be arranged on degree of depth 15m place, reference surface is at degree of depth 195m place, and the wave field downward continuation has avoided the wave field of scatterer 4 to disturb behind reference surface.

1-shot point wherein, 2-reference surface, 3-useful signal ripple, 4-scatterer.

The original big gun collection of Fig. 3 (left side), along the Depth Domain filtering result of degree of depth axle continuation (in) and difference road collection (right side), filtered as can be seen from difference road composite section and to have disturbed and to have preserved effective reflection.

5-significant wave wherein, 6-interference wave, 7-direct wave.

Fig. 4 is to the hard image before and after the prestack list big gun seismologic record filtering of two-dimension earthquake survey data.Wherein (a) is the seismic record section that adopts filtering of the present invention preceding, and the regional near surface that is enclosed disturbs very strong; (b) be the big gun collection recording picture that adopts after the inventive method is handled; (c) be the interference wave image that adopts filtering of the present invention.

Fig. 5 is the CMP road set pair ratio image that prestack list big gun seismologic record filtering front and back of above-mentioned two-dimension earthquake survey data are extracted.Wherein (a) is the seismic record section that adopts filtering of the present invention preceding, and the disturbed ripple of significant wave is covered, and the regional near surface that is enclosed disturbs very strong; (b) be the big gun collection recording picture that adopts after the inventive method is handled, useful signal strengthens; (c) be the interference wave image that adopts filtering of the present invention.

Fig. 6 is the stacked section contrast of the present invention after to same data filtering, (a) is the stack result before the filtering, (b) is filtered stack result, (c) is noise.

Fig. 7 is a 3D seismic data Depth Domain filtering comparison diagram, (a) is original shot gather data before the filtering, and (b) filtered shot gather data is (c) by the noise of filtering.

Embodiment

Embodiment 1

For the earthquake shot gather data of gathering, to choose the geological data of a two-dimentional survey line and implement the Depth Domain Filtering Processing, the basic condition of data is:

Data track is long to be 4000ms, and sampling interval is 4ms,

The survey line data comprise 351 big guns altogether, every big gun 800 roads.

1) at first carries out the data gain, data are carried out trace equalization and carried out amplitude compensation along time orientation along space x direction, make data adapt to wave equation and handle.

2) secondly carry out two-dimension fourier direct transform and downward wave field extrapolation, to the big gun collection by formula (4) and (5) from the ground surface continuation to reference surface, the selected reference surface degree of depth is 150m, be divided into three layers, every layer thickness and speed are respectively: 80m, 40m and 30m, 2000m/s, 2400m/s, 2800m/s.

$P(k_x,z+\mathrm{\&Delta;z},\mathrm{\&omega;})=P(k_x,z,\mathrm{\&omega;})e^{-i{k}_z\mathrm{\&Delta;Z}}---\left(4\right)$

$k_z=\left\{\begin{array}{cc}\sqrt{\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2}& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2\&GreaterEqual;0)\\ 0& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2<0)\end{array}\right.----\left(5\right)$

In the formula, ω and k _xThe circular wavenumber of representing circular frequency and horizontal direction respectively; P (k _x, z ω) is ω-k _xThe wave field at inherent depth z place, territory.P (k _x, 0, ω) be illustrated in ω-k _xThe terrestrial gun collection record in territory; c _nBe illustrated in the dielectric layer speed between z and the z+ Δ z.

In the process of downward continuation, the noise that is associated with the evanescent wave number is changed to zero, and is identified, and the useful signal continuation is to reference surface.

3) carry out Depth Domain filtering then, (x, t), to the big gun collection of continuation to the reference surface, the time, (x, wave field t) was interference wave, with its zero setting less than DT to establish the direct wave that arrives reference surface from focus and be hourage DT.

4) make progress wave field extrapolation and two dimensional inverse fourier transform, to the filtered big gun collection of Depth Domain by formula (6) and (7) from the reference surface continuation to ground surface.

$P(k_x,z-\mathrm{\&Delta;z},\mathrm{\&omega;})=P(k_x,z,\mathrm{\&omega;})e^{i{k}_z\mathrm{\&Delta;z}}---\left(6\right)$

$k_z=\left\{\begin{array}{cc}\sqrt{\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2}& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2\&GreaterEqual;0)\\ \sqrt[i]{k_x^2-\frac{{\mathrm{\&omega;}}^2}{c_n^2}}& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2<0)\end{array}\right.---\left(7\right)$

5) carry out the data inverse gain at last, recover the original-shape of reflected signal, the seismic wave effectively of the face of land and near surface interference wave is eliminated, owing to can change the waveform of signal along the gain of time orientation, the purpose of inversion benefit is to recover the original-shape of reflected signal, to guarantee in the denoising process reflected signal without any injury.

Through the Depth Domain Filtering Processing, the noise that is associated with the evanescent wave number has been pressed, and the reflection useful signal has obtained reservation, as shown in Figure 4.

In order to further specify the effect of filtering, be CMP road collection with filtered data pick-up, Fig. 5 is the CMP road set pair ratio image that is extracted before and after the filtering, as can be seen from the figure, concentrate in first and the 3rd CMP road, sightless reflected wave information is high-visible after filtering originally.Second CMP road collection, the reflection wave signal to noise ratio (S/N ratio) that nearly geophone offset place is the hyperbolic wire increases, and the reflection at geophone offset place far away is grown out of nothing.

Fig. 6 has provided before the filtering and filtered one section stacked section and corresponding poor road collection stacked section.Stacked section shallow, in, deep reflex ripple lineups all become more clear.And in the difference road collection stacked section, do not have reflection wave imaging, further specify the characteristics that signal of the present invention keeps.

Embodiment 2

For the earthquake shot gather data of gathering, to choose the geological data of the three-dimensional survey line of a big gun and implement the Depth Domain Filtering Processing, the basic condition of data is:

Data track is long to be 6000ms, and sampling interval is 2ms,

Data comprise 8 surveys line, every line 192 roads.

Dx＝40m，Dy＝240m

1) at first carries out the data gain, data are carried out trace equalization and carried out amplitude compensation along time orientation along space x, y direction, make data adapt to wave equation and handle.

2) secondly carry out three-dimensional Fourier direct transform and wave field extrapolation downwards, to the big gun collection by formula (5) and (6) from the ground surface continuation to reference surface, the selected reference surface degree of depth is 150m, be divided into three layers, every layer thickness and speed are respectively: 80m, 40m and 20m, 2000m/s, 2400m/s, 2700m/s.

$P(k_x,k_y,z+\mathrm{\&Delta;z},\mathrm{\&omega;})=P(k_x,k_y,z,\mathrm{\&omega;})e^{-i{k}_z\mathrm{\&Delta;z}}---\left(8\right)$

$k_z=\left\{\begin{array}{cc}\sqrt{\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2-k_y^2}& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2-{\mathrm{<figure-callout\; id="2"\; label="k\; y"\; filenames="C20041010264900131.png"\; state="\{\{state\}\}">k</figure-callout>}}_y^{}\&GreaterEqual;0)\\ 0& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2-{\mathrm{<figure-callout\; id="2"\; label="k\; y"\; filenames="C20041010264900131.png"\; state="\{\{state\}\}">k</figure-callout>}}_y^{}<0)\end{array}\right.---\left(9\right)$

In the formula, ω, k _xAnd k _yRepresent circular frequency respectively, the circular wavenumber of horizontal direction and vertical direction; P (k _x, k _y, z ω) is ω-k _xThe wave field at inherent depth z place, territory.P (k _x, k _y, 0, ω) be illustrated in ω-k _x-k _yThe terrestrial gun collection record in territory; c _nBe illustrated in the dielectric layer speed between z and the z+ Δ z.

3) carry out Depth Domain filtering then, establish from the hourage that focus arrives the direct wave of reference surface be DT (x, t), to the big gun collection of continuation to the reference surface, the time less than DT (x, part zero setting t).

4) make progress wave field extrapolation and three-dimensional Fourier inverse transformation, to the filtered big gun collection of Depth Domain by formula (10) and (11) from the reference surface continuation to ground surface.

$P(k_x,k_y,z-\mathrm{\&Delta;z},\mathrm{\&omega;})=P(k_x,k_y,z,\mathrm{\&omega;})e^{i{k}_z\mathrm{\&Delta;z}}---\left(10\right)$

$k_z=\left\{\begin{array}{cc}\sqrt{\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2-k_y^2}& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2-{\mathrm{<figure-callout\; id="2"\; label="k\; y"\; filenames="C20041010264900131.png"\; state="\{\{state\}\}">k</figure-callout>}}_y^{}\&GreaterEqual;0)\\ i\sqrt{k_x^2+k_y^2-\frac{{\mathrm{\&omega;}}^2}{c_n^2}}& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2-{\mathrm{<figure-callout\; id="2"\; label="k\; y"\; filenames="C20041010264900131.png"\; state="\{\{state\}\}">k</figure-callout>}}_y^{}<0)\end{array}\right.---\left(11\right)$

5) carry out the data inverse gain at last, recover the original-shape of reflected signal, the seismic wave effectively of the face of land and near surface interference wave is eliminated, owing to can change the waveform of signal along the gain of time orientation, the purpose of inversion benefit is to recover the original-shape of reflected signal, thereby guarantees in the denoising process reflected signal without any injury.

Through the Depth Domain Filtering Processing, the noise that is associated with the evanescent wave number has been pressed, and the usable reflection signal has obtained reservation, as shown in Figure 7.

Claims (3)

1, a kind of method that adopts Depth Domain filtering to eliminate linear and non-linear interference wave is characterized in that may further comprise the steps:

(1) gathers the earthquake shot gather data, the shot gather data of gathering is carried out the data gain, data are carried out trace equalization and carried out amplitude compensation along time orientation along direction in space, make data adapt to wave equation and handle;

When the spatial sampling of data is big at interval, after shot gather data gained, select data are carried out space interpolation to reduce spatial aliasing, eliminate incorrect continuation to the alias data;

(2) shot gather data is carried out Fourier direct transform and wave field extrapolation downwards, to reference surface, in the downward continuation process, change the phase place of signal, do not change the amplitude of signal and discern noise from the ground surface continuation;

(3) continuation is carried out Depth Domain filtering to the shot gather data on the reference surface;

(4) to the filtered shot gather data of Depth Domain make progress wave field extrapolation and inverse fourier transform, from the reference surface continuation to ground surface, in the process of upward continuation, the phase place of restoring signal;

Carrying out downwards and in the upward continuation process, selecting the phase shift operator of signal maintenance, utilize evanescent wave to count attenuate acoustic noise;

(5) carry out data inverse gain, recover the original-shape of reflected signal, the seismic wave effectively of the be eliminated face of land and near surface interference wave also becomes figure,

Explore resulting seismologic record for two dimension, adopt following two-dimension fourier direct transform and inverse transformation:

Two-dimension fourier direct transform and downward wave field extrapolation, to the big gun collection as follows from the ground surface continuation to reference surface, the reference surface degree of depth is 150m, is divided into three layers, every layer thickness and speed are respectively 80m, 40m and 30m, 2000m/s, 2400m/s, 2800m/s;

P(k _x，z+Δz，ω)＝P(k _x，z，ω)e ^-ikzΔz (4)

$k_z=\{\begin{array}{cc}\sqrt{\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2}& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2\&GreaterEqual;0)\\ 0& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2<0)\end{array}---\left(5\right)$

In the formula, ω and k _xThe circular wavenumber of representing circular frequency and horizontal direction respectively; P (k _x, z ω) is ω-k _xThe wave field at inherent depth z place, territory.P (k _x, 0, ω) be illustrated in ω-k _xThe terrestrial gun collection record in territory; c _nBe illustrated in the dielectric layer speed between z and the z+ Δ z,

In the process of downward continuation, the noise that is associated with the evanescent wave number is changed to zero, and is identified, the useful signal continuation to reference surface,

Carry out Depth Domain filtering then, the direct wave that arrives reference surface from focus be hourage DT (x, t), to the big gun collection of continuation to the reference surface, the time less than DT (x, wave field t) is interference wave, with its zero setting,

Make progress wave field extrapolation and two dimensional inverse fourier transform, to the filtered big gun collection of Depth Domain as follows from the reference surface continuation to ground surface:

P(k _x，z-Δz，ω)＝P(k _x，z，ω)e ^ikzΔz (6)

$k_z=\{\begin{array}{cc}\sqrt{\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2}& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}{-k}_x^2\&GreaterEqual;0)\\ i\sqrt{k_x^2-\frac{{\mathrm{\&omega;}}^2}{c_n^2}}& (\frac{{\mathrm{\&omega;}}^2}{c_n^2}-k_x^2<0)\end{array}---\left(7\right)$

2, a kind of method that adopts Depth Domain filtering to eliminate linear and non-linear interference wave according to claim 1, it is characterized in that exploring resulting seismologic record for two dimension, the phase shift operator that is adopted is in filtering advance row amplitude compensation and field statics.

3, a kind of method that adopts Depth Domain filtering to eliminate linear and non-linear interference wave according to claim 1, it is characterized in that the seismologic record that exploration obtains for three-dimensional, seismologic record is carried out three-dimensional Fourier direct transform and inverse transformation, and the phase shift operator automatically spreads to three-dimensional situation.

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