Method for identifying two-dimensional up-and-down sea-bottom multiple
Technical field
The present invention relates to geophysical exploration technology, belong to the technology category of the regular interference wave of compacting in the seismic data processing procedure, is a kind of method for identifying two-dimensional up-and-down sea-bottom multiple.
Background technology
In the seismic prospecting,, when earthquake data acquisition, can record more intense sea-bottom multiple at sea because the seabed is a strong reflecting interface between fluid and the solid.The existence of sea-bottom multiple can mislead the explanation personnel on the one hand and give the structure elucidation result who makes mistake, and can disturb primary reflection on the other hand, influences the structure imaging of primary reflection and utilizes primary reflection to carry out Reservoir Analysis.Therefore suppress sea-bottom multiple in the method for marine seismic data and be always a gordian technique during method for marine seismic data is handled.
The method of the sea-bottom multiple in the compacting method for marine seismic data generally is divided into two big classes.One class is based on the kinematics difference of sea-bottom multiple and primary reflection, multiple reflection is separated with primary reflection, thereby reach the purpose of multiple suppression; Another kind ofly be based on wave theory simulation or dope the model trace collection of sea-bottom multiple, utilize multiple reflection model trace collection then, adopt adaptive approach that the multiple reflection in the raw data is deducted as multiple reflection.
Method based on the kinematics difference multiple suppression of sea-bottom multiple and primary reflection mainly comprises predictive deconvolution method, F-K conversion filter method, Karhunen-Loeve transformation filter method, Tau-p conversion filter method and Tau-p territory The Method of Deconvolution.Based on wave theory carry out that the multiple reflection forecast method mainly contains that wave equation is just drilled, the wave field extrapolation method, based on the method for WRW model, based on the Born Series Method and the Kirchhoff Series Method of backscattering theory.Multiple reflection self-adaptation subraction comprises that mainly minimum two multipliers are according to matching method, pattern-recongnition method and independent component analysis method.
Wave field extrapolation multiple reflection forecasting techniques can be divided into the sea level by the geological data treated side and to be the wave field extrapolation multiple reflection forecasting techniques of treated side and to be the wave field extrapolation multiple reflection forecasting techniques of treated side with the sea bottom surface.Numerical method by wave field extrapolation can be divided into integral method wave field extrapolation multiple reflection forecasting techniques and phase shift method wave field extrapolation technology.Can be divided into single stage method, two-step approach and three-step approach wave field extrapolation multiple reflection forecasting techniques by the continuation step.
The wave field extrapolation multiple reflection forecasting techniques of traditional with the sea level is treated side is shown in Fig. 1 (a), general adopt integral method earlier geological data from the sea level continuation to the seabed, again continuation to the geological data in seabed from the seabed continuation to the sea level, so just doped sea-bottom multiple.This method has obviously been ignored the reflection that D is ordered, and need use the speed of medium under the seabed during integration.Need two speed when overcoming integration, people generally are approximately a monocline or flat seabed to the fluctuating seabed in an arrangement, shown in Fig. 1 (b).Fig. 1 (a) and (b) just different on the mode of processing seabed, but they need two step continuation to finish the prediction of sea-bottom multiple, and in order to reduce the inconvenience that the two-step approach continuation brings, people had proposed the single stage method continuation afterwards again.This method is that the big gun collection is placed on the mirror image face of sea level with respect to level and smooth sea bottom surface, utilizes upward traveling wave just can obtain the multiple reflection model trace collection of this big gun collection to the big gun collection to the sea level from the continuation of mirror image face like this, sees Fig. 1 (c).
Obviously, sea-bottom multiple Forecasting Methodology in the past based on wave field extrapolation, when acutely rising and falling in the seabed, because can not, therefore there is bigger error between the kinematics character of the sea-bottom multiple of prediction and actual multiple reflection.
Summary of the invention
The present invention seeks under the prerequisite of known submarine elevation and seawater speed, to fluctuating sea-bottom multiple prediction, provide a kind of method for identifying two-dimensional up-and-down sea-bottom multiple of wave field extrapolation of correct realization fluctuating seabed the wave field extrapolation technology introduction of fluctuating interface.
The invention provides following solution:
1) geological data, field survey or the indoor submarine elevation data of asking for of employing marine streamer seismic acquisition;
2) from minimum big gun gunfire collection, read also (can not occur subjective action word) submarine elevation of arranging according to big gun collection place of shot gather data, obtain its maximum submarine elevation and minimum submarine elevation, it is poor to calculate minimum and maximum submarine elevation;
3) when minimum and maximum submarine elevation difference during, by horizontal seabed prediction sea-bottom multiple less than 5 meters:
p
n(x, z=0 t) are the n big gun geological data that is positioned at (z=0) on the sea level,
m
n(x, z=0 t) are the sea-bottom multiple of determining of the correspondence n big gun that is positioned at (z=0) on the sea level obtained,
Wherein n is a big gun number, and x is the distance of shot point to acceptance point, and z is the elevation coordinate, and t is a time coordinate;
The multiple reflection in the described definite horizontal seabed of step 3) is meant:
(1) to p
n(x, z=0 t) carry out two-dimentional fourier transform about x and t, obtain P
n(k
x, z=0, ω), k wherein
xBe respectively horizontal direction circular wavenumber and circular frequency with ω;
Be the vertical direction circular wavenumber, c is the speed of seawater;
(2) by formula
Obtain the multiple reflection that frequency-wavenumber domain is surveyed, wherein, M
n(k
x, z=0 is the multiple reflection of the n big gun of frequency-wavenumber domain prediction ω), H is the mean value of minimum and maximum submarine elevation;
(3) to M
n(k
x, z=0 ω) carries out two-dimentional Fu Shi inverse transformation, obtains the multiple reflection m of the n big gun of time domain prediction
n(x, z=0, t).
4) when minimum and maximum submarine elevation difference during, by fluctuating seabed prediction sea-bottom multiple greater than 5 meters:
p
n(x, z=0 t) are the n big gun geological data that is positioned on the sea level (z=0),
p
n(x, z=Z
0, t) be n big gun seismic wave field of (z=Z0) on bottom surface, shallow sea,
p
n(x, z=Z
N, t) be the n big gun on bottom surface, deep-sea (seismic wave field of z=ZN,
p
n(x, z
i, t) be the n big gun at z
i=z
0+ (i-1) Δ z (i=1,2 ... the N+1) seismic wave field on the face,
q
n(z
i, be that the n big gun is at z t)
i=z
0+ (i-1) Δ z (i=1,2 ... the N+1) record of bottom, face Shanghai,
m
n(x, z=0 t) are the sea-bottom multiple of the prediction of the n big gun on sea level (z=0) obtained,
Wherein n is a big gun number, and x is the distance of shot point to acceptance point, and z is the elevation coordinate, and t is a time coordinate, and Δ z is the step size of depth direction.
The multiple reflection in the described definite fluctuating seabed of step 3) is meant:
(1) to p
n(x, z=0 t) carry out fourier transform about x and t, obtain P
n(k
x, z=0, ω), k wherein
xWith ω for being respectively horizontal direction circular wavenumber and circular frequency;
Be the vertical direction circular wavenumber, c is the speed of seawater;
(2) by formula
Obtain the seismic wave field of the frequency-wavenumber domain of (z=Z0) on bottom surface, shallow sea;
(3) from bottom surface, shallow sea (i=1) to bottom surface, deep-sea (i=N+1), by formula P
n(k
x, z=z
I+1, ω)=P
n(k
x, z=z
i, ω) e
-2ik Δ zCalculate z
i=z
0+ (i-1) the descending wave-wave field on the Δ z face is to P
n(k
x, z=z
I+1, ω) carry out two-dimentional Fu Shi inverse transformation, and the following traveling-wave field q at place, record seabed
n(z
I+1, t);
(4) from bottom surface, deep-sea (i=N+1) to bottom surface, shallow sea (i=1), by formula p
n(x, z=z
i, t)=p
n(x, z=z
i, t)+q (z
i, t) carry out wave field and be bumped into, by formula: P
n(k
x, z=z
I-1, ω)=P
n(k
x, z=z
i, ω) e
-ik Δ zCarry out the upstream wave field continuation;
(5) by formula
Obtain the sea-bottom multiple of the frequency-wavenumber domain that on the sea level, writes down;
(6) to M
n(k
x, z=0 ω) carries out two-dimentional Fu Shi inverse transformation, obtains the multiple reflection of the n big gun of time domain prediction, m
n(x, z=0, t).
Advantage one of the present invention is to have taken all factors into consideration precision and efficient, and the different situations in seabed are carried out different processing, locates to adopt all the highest phase shift technique of precision and efficient gently in the seabed; At the submarine relief place, adopt the very high wave field of precision to be bumped into technology; The 2nd, first wave field is bumped into the technology sea-bottom multiple that is applied to rise and fall and determines.
Description of drawings
The sea-bottom multiple that Fig. 1 is traditional is determined the method synoptic diagram;
(a) traditional multiple reflection Forecasting Methodology based on wave field extrapolation,
(b) the approximate multiple reflection Forecasting Methodology of inclination or flat sea bottom surface based on wave field extrapolation,
(c) the multiple reflection Forecasting Methodology that begins from the mirror image face based on wave field extrapolation
Fig. 2 the present invention sea-bottom multiple that rises and falls is determined the method synoptic diagram;
(a) according to submarine elevation the seabed is divided into horizontal seabed with the fluctuating seabed and adopt different wave field extrapolation algorithms
(b) corresponding fluctuating benthic division adopts wave field to be bumped into method to carry out wave field extrapolation
The big gun collection record of Fig. 3 input;
The sea-bottom multiple of the prediction of Fig. 4 output.
Specific embodiments
The present invention adopts streamer seismic data, field survey or the indoor submarine elevation data of asking for of marine streamer seismic acquisition, on the basis of taking all factors into consideration computational accuracy and counting yield, utilize phase shift horizontal interface wave field extrapolation method and wave field to be bumped into the sea-bottom multiple that method fluctuating interface wave field continuation method predicts that the seabed produces, obtain the sea-bottom multiple geological data of prediction.
Definition:
Bottom, the shallow sea elevation (Shallow bottom elevation) of SBE or Z0---;
The elevation (Deep bottom elevation) of the bottom, deep-sea of DBE or ZN-;
Poor (the Bottom elevation difference) of the most shallow and deep-sea floor elevation of BED---;
The mean value (Mean of bottom elevation) of the most shallow and deep-sea floor elevation of MBE--;
The most shallow and the deep-sea floor elevation that LBED---user is given poor is used to differentiate (the Limitation of the bottom elevation difference) that flat seabed still is the fluctuating seabed;
The wave field extrapolation step-length that DZ---user is given.
The specific implementation step of fluctuating sea-bottom multiple prediction is as follows:
1, from minimum big gun gunfire collection, reads shot gather data p
n(x, z=0, t) (see figure 3) and submarine elevation data.p
n(t) for being positioned at the n big gun geological data of (z=0) on the sea level, wherein n is a big gun number for x, z=0, and x is the distance of shot point to acceptance point, and z is the elevation coordinate, and t is a time coordinate;
2, the submarine elevation section of arranging according to big gun collection place obtains the altitude figures SBE and the DBE of the most shallow and bottom, deep-sea.
3, calculate the dark and the most shallow submarine elevation difference BED of place.As shown in Figure 2, when difference of elevation is less than BEI at the bottom of the darkest and shallow sea, the multiple reflection in prediction level seabed according to the following steps.
(1) the mean value MBE of the minimum and maximum submarine elevation of calculating puts H=MBE;
(2) to p
n(x, z=0 t) carry out two-dimentional fourier transform about x and t, obtain P
n(k
x, z=0, ω), k wherein
xBe respectively the circular wavenumber and the circular frequency of horizontal direction with ω;
Be the circular wavenumber of vertical direction, c is the speed of seawater;
(3) by formula
Obtain the sea-bottom multiple that frequency-wavenumber domain is surveyed, wherein, M
n(k
x, z=0 is the multiple reflection of n big gun collection of frequency-wavenumber domain prediction ω), H is the mean value of minimum and maximum submarine elevation;
(4) to M
n(k
x, z=0 ω) carries out two-dimentional Fu Shi inverse transformation, obtains the multiple reflection m of n big gun collection of time domain prediction
n(x, z=0 t), see Fig. 4.
4, when the difference of elevation of the most shallow and bottom, deep-sea during, as shown in Figure 2, adopt wave field to be bumped into the multiple reflection in method prediction fluctuating seabed according to the following steps less than BEI.
(1) to p
n(x, z=0 t) carry out fourier transform about x and t, obtain P
n(k
x, z=0, ω), k wherein
xWith ω be circular wavenumber and the circular frequency that is respectively horizontal direction;
Be the circular wavenumber of vertical direction, c is the speed of seawater;
(2) by formula
Obtain the seismic wave field of the frequency-wavenumber domain of (z=Z0) on bottom surface, shallow sea;
(3) from bottom surface, shallow sea (i=1) to bottom surface, deep-sea (i=N+1), by formula P
n(k
x, z=z
I+1, ω)=P
n(k
x, z=z
i, ω) e
-2ik Δ zCalculate z
i=z
0+ (i-1) the descending wave-wave field on the Δ z face is to P
n(k
x, z=z
I+1, ω) carry out two-dimentional Fu Shi inverse transformation, and the following traveling-wave field q at place, record seabed
n(z
I+1, t);
(4) from bottom surface, deep-sea (i=N+1) to bottom surface, shallow sea (i=1), by formula p
n(x, z=z
i, t)=p
n(x, z=z
i, t)+q (z
i, t) carry out wave field and be bumped into, by formula P
n(k
x, z=z
I-1, ω)=P
n(k
x, z=z
i, ω) e
-ik Δ zCarry out the upstream wave field continuation;
(5) by formula
Obtain the sea-bottom multiple of the frequency-wavenumber domain that on the sea level, writes down;
(6) to M
n(k
x, z=0 ω) carries out two-dimentional Fu Shi inverse transformation, obtains the multiple reflection of n big gun collection of time domain prediction, m
n(x, z=0 t), see Fig. 4.