CN101241192B - Method for eliminating pneumatic gun near-field wavelet imaginary reaction - Google Patents

Abstract

The present invention provides a method for eliminating ghost reflection of wavelet in air gun recent field which relates to petroleum geological exploration and construction technology. Blazing air gun and recording recent field wavelet of all units of air gun array; original wavelet of air gun unit is calculated by obtaining one unit resent wavelet data A[n] of air gun array, the ghost reflection of real measuring resent wavelet of all units is eliminated, employing air gun resent field wavelet eliminated ghost reflection simulate air gun far field wavelet, and introducing processed far field wavelet to earthquake data to gain section. The present invention has simple and efficient calculation and rapid calculation speed, can meet requirement of resent field wavelet simulating far field wavelet, is convenient for estimating and regulating quality of air gun array and can obtain exact inverse wavelet operator and improve the distinguish of earthquake data.

Description

A kind of method of eliminating pneumatic gun near-field wavelet imaginary reaction

Technical field

The present invention relates to the petroleum geology exploration operating technique, be applied to the analysis and the far-field wavelet simulation of the air gun source in the petroleum prospecting of neritic area, beach.A kind of method of eliminating pneumatic gun near-field wavelet imaginary reaction

Background technology

When petroleum geology exploration is constructed, need estimate and adjust the quality of the air-gun array of image data, and then obtain better processing profiles.Normally start with from the far-field wavelet of array, promptly examine the parameters index of far-field wavelet, comprising: the directivity (directivity) of main pulse value (primary), peak-to-peak value (peak-peak), bubble ratio (peak-bubble ratio), bubble period (period), dominant frequency size (dominantfrequency), frequency span (spectrum width), wavelet and stability (stability) etc.The far-field wavelet of known air-gun array, just can ask for anti-comparatively accurately wavelet operator, carry out deterministic deconvolution, improve the resolution of data effectively, in addition, though the air-gun array of excellent stability, in actual production, because the variation of factors such as the concentration of seawater, temperature, flow velocity, its wavelet all can have change to a certain degree.Based on the reason of above-mentioned several aspects, can excite along with air gun aborning and obtain the array wavelet in real time more and more to draw attention.

When the exploration of the utmost point shallow sea area depth of water more shallow (generally in tens meters) area, can't satisfy the requirement of record far-field wavelet, the approach that solves is the near-field wavelet of each unit in the real time record array (single rifle single or coherent body cluster), then calculates the far-field wavelet of whole array.Yet an important step of calculating in the far-field wavelet process is exactly the ghosting that will remove in the actual measurement air gun near-field wavelet.

At present, the method for eliminating ghosting can be divided into two big classes, and a class is based on the filtering method of difference between significant wave and the ghosting ripple, abbreviates filtering method as.This method is to utilize between ghosting ripple and the significant wave at ripple to propagate aspect the kinematics, as the time, differences such as speed, by shift meanses such as f-k tau-p and tau-q, the geological data that time and space territory (being called " old territory ") contained the ghosting ripple is mapped to other special region (be called ' neofield), at this moment, significant wave and ghosting ripple can present than " old territory " evident difference more at " neofield ", difference as two kinds of ripples distributing position on section, therefore can pass through various shift meanses, significant wave and ghosting wavelength-division are left, and then filtering ghosting ripple.

The another kind of prediction subraction that is based on wave equation abbreviates the wave equation prediction as and deducts method, and this method is predicted the ghosting ripple by actual wave field of wave equation simulation or inverting geological data, then it is deducted from original earthquake data.Method based on wave equation compacting ghosting ripple mainly contains three classes, (1) wave field extrapolation method; (2) feedback loop method is called for short feedback transmitter (3) backscattering progression method, is called for short anti-scattering method.The wave field extrapolation method is to simulate the ghosting ripple with wave field extrapolation, and feedback loop and backscattering progression method are to predict the ghosting ripple by prestack inversion.The ghosting ripple is deducted the process of eliminating ghosting of just having finished from the actual measurement seismic wave.

Usually these two kinds of methods all have the effect of eliminating ghosting preferably in the Data Processing process, but the distance of shot point and acceptance point is very near when measuring owing to the air gun near-field wavelet, usually has only 1 meter, shot point also has only several meters apart from the distance of seawater face, in the air gun near-field wavelet of actual measurement, the time of arrival of ghosting and first break time are at interval less than a sub-period of wave, this makes that above method can not be quick, the ghosting composition that to survey effectively in the air gun near-field wavelet is got rid of, quality assessment and adjustment have been influenced to air-gun array, can not ask for anti-comparatively accurately wavelet operator, improve the resolution of seismic data.

The content of invention

The object of the invention provides a kind of for accurately obtaining anti-wavelet operator, improves the resolution of seismic data and eliminates the method for pneumatic gun near-field wavelet imaginary reaction.

The present invention adopts following steps:

1) adopts common exploration means, excite air gun and write down the near-field wavelet of each unit of air-gun array;

2) get the near-field wavelet data A[n of a unit of air-gun array], n is the sampling number of data;

3) try to achieve the former wavelet of air gun unit by following formula, thereby eliminate the ghosting of air gun near-field wavelet,

$\left\{\begin{array}{c}A\left[i\right]=X\left[i\right]/s;(i<=I,i=\mathrm{0,1,2}\&CenterDot;\&CenterDot;\&CenterDot;I)\\ A\left[i\right]=X\left[i\right]/s+(\left(X\right[i-I]/h)*r)/(h+s);(i>I,i=I+1,I+2\&CenterDot;\&CenterDot;\&CenterDot;n-1)\end{array}\right.$

In the formula: X[n] be the former wavelet of air gun;

A[n] for surveying the air gun near-field wavelet;

N is the sampling number of actual measurement air gun near-field wavelet;

H is that air gun is displayed the degree of depth;

S is wave detector position, near field (position of near field wave detector s rice below air gun source);

V is the velocity of propagation of seismic wave in seawater;

R is the boundary reflection coefficient;

P is the data sampling interval;

When I arrived the near field wave detector for the ghosting ripple, the sampling number of having finished calculated by following formula: I=int (((h+h+s)/v-s/v)/p)=int (2h/v/p);

4) repeat above 2,3 steps each air gun unit is calculated, finish the actual measurement near-field wavelet of all unit and eliminate ghosting;

5) adopt the air gun near-field wavelet simulation air gun far-field wavelet of eliminating ghosting with usual way, the far-field wavelet importing seismic data after handling is handled obtaining section.

The ghosting of the elimination air gun near-field wavelet of linear equation is separated in utilization of the present invention, calculates simply, effectively, and arithmetic speed is exceedingly fast, and can satisfy the requirement of near-field wavelet Simulation of far-field wavelet fully.Made things convenient for quality assessment and adjustment, can ask for anti-comparatively accurately wavelet operator, improved the resolution of seismic data air-gun array.

Description of drawings

Fig. 1 adds figure for the present invention surveys wavelet (a), former wavelet (b), ghosting ripple folded (c);

Fig. 2 is air-gun array figure of the present invention;

Fig. 3 surveys air gun near-field wavelet figure for the present invention;

Fig. 4 eliminates air gun near-field wavelet figure after the ghosting for the present invention.

Embodiment:

Actual measurement air gun near-field wavelet is formed by stacking by former wavelet and ghosting ripple, sees Fig. 1, can promptly eliminate the air gun near-field wavelet after the ghosting in the hope of the former wavelet of air gun according to the boundary reflection characteristic of ripple and air-gun array parameter and experiment parameter.

The ghosting of the method elimination air gun near-field wavelet of linear equation is found the solution in utilization of the present invention, establishing the former wavelet of air gun earlier is X[n], actual measurement air gun near-field wavelet is A[n], then display degree of depth h, wave detector position, near field s (the near field wave detector is in the position of s rice below the air gun source), seismic wave velocity of propagation v, boundary reflection coefficient r, the data sampling interval p in seawater according to the boundary reflection characteristic and the air gun of ripple, calculate the former wavelet X[n of air gun], promptly eliminated the air gun near-field wavelet of ghosting.

The embodiment of the invention has 30 air guns, divides 14 unit to form air-gun array, as shown in Figure 2.Air gun capacity 2430cu.in, gun pressure 2000psi, air gun display degree of depth h=3.5m, the position of near field wave detector is at the vertical lower s=1m of air gun unit, sampling interval p=1ms, sampling number n=250, boundary reflection coefficient r=1.0, experiment waters seawater speed v=1650m.Utilize the present invention to eliminate the ghosting of actual measurement air gun near-field wavelet, process is as follows:

1) in utmost point shallow sea area exploration work progress, when air gun excited, the near field wave detector had write down the near-field wavelet of each unit of air-gun array, and with air gun near-field wavelet data recording to tape.

2) adopt conventional method to read the near-field wavelet data A[n of a unit of air-gun array], n=250 is the sampling number of data, the near-field wavelet form of surveying each unit is as shown in Figure 3;

3) adopt following formula to calculate:

$\left\{\begin{array}{c}A\left[i\right]=X\left[i\right]/s;(i<=I,i=\mathrm{0,1,2}\&CenterDot;\&CenterDot;\&CenterDot;I)\\ A\left[i\right]=X\left[i\right]/s+(\left(X\right[i-I]/h)*r)/(h+s);(i>I,i=I+1,I+2\&CenterDot;\&CenterDot;\&CenterDot;n-1)\end{array}\right.$

, be the unknown term that to find the solution wherein: X[n] for the former wavelet of hypothesis air gun;

A[n] for surveying the air gun near-field wavelet;

H=3.5m is that air gun is displayed the degree of depth;

S=1m is wave detector position, near field (position of near field wave detector s rice below air gun source);

V=1650m/s is the velocity of propagation of seismic wave in seawater;

R=1 is the boundary reflection coefficient;

P=1ms is the data sampling interval;

N=250 is the sampling number of actual measurement air gun near-field wavelet;

When I=arrives the near field wave detector for the ghosting ripple, the sampling number of having finished.

I＝int(((h+h+s)/v-s/v)/p)；

＝int(((3.5+3.5+1)/1650-1/1650)/0.001)；

＝4；

With parameter value substitution formula group obtain as shown in the formula:

$\left\{\begin{array}{c}A\left[i\right]=X\left[i\right]/1;(i<=4,i=\mathrm{0,1,2}\&CenterDot;\&CenterDot;\&CenterDot;4)\\ A\left[i\right]=X\left[i\right]/1+(\left(X\right[i-4]/3.5)*1)/(3.5+1);(i>4,i=\mathrm{5,6}\&CenterDot;\&CenterDot;\&CenterDot;249)\end{array}\right.$

4) calculate the former wavelet of trying to achieve this air gun unit, promptly eliminated the air gun near-field wavelet of ghosting.

5) each air gun unit is carried out 2,3,4 steps, actual measurement near field of finishing all unit is eliminated the work of ghosting.

Wavelet form after the actual measurement air gun near-field wavelet elimination ghosting as shown in Figure 4.

6) use the air gun near-field wavelet of having eliminated ghosting and can simulate the air gun far-field wavelet, and far-field wavelet is applied to the seismic data processing procedure, to obtain better processing profiles.

A[n of the present invention], h, s, v, r, parameters such as p, n are actual measurement or given data, its scope is not limited to embodiment of the invention institute numerical value.

Claims (1)

1. method of eliminating pneumatic gun near-field wavelet imaginary reaction, its feature adopts following steps:

1) adopts common exploration means, excite air gun and write down the near-field wavelet of each unit of air-gun array;

2) get the actual measurement air gun near-field wavelet data A[n of a unit of air-gun array], n is the sampling number of actual measurement air gun near-field wavelet data;

3) try to achieve the former wavelet of air gun unit by following formula, thereby eliminate the ghosting of air gun near-field wavelet,

$\left\{\begin{array}{c}A\left[i\right]=X\left[i\right]/s;(i<=I,i=\mathrm{0,1,2}...I)\\ A\left[i\right]=X\left[i\right]/s+(\left(X\right[i-I]/h)*r)/(h+s);(i>I,i=I+1,I+2...n-1)\end{array}\right.$

In the formula: X[n] be the former wavelet of air gun;

A[n] for surveying air gun near-field wavelet data;

N is the sampling number of actual measurement air gun near-field wavelet data;

H is that air gun is displayed the degree of depth;

S is wave detector position, near field, i.e. the position of near field wave detector S rice below air gun source;

V is the velocity of propagation of seismic wave in seawater;

R is the boundary reflection coefficient;

P is the data sampling interval;

When I arrived the near field wave detector for the ghosting ripple, the sampling number of having finished calculated by following formula: I=int (((h+h+s)/v-s/v)/p)=int (2h/v/p);

4) repeat above 2,3 steps each air gun unit is calculated, finish the actual measurement near-field wavelet of all unit and eliminate ghosting;

5) adopt the air gun near-field wavelet simulation air gun far-field wavelet of eliminating ghosting with usual way, the far-field wavelet importing seismic data after handling is handled obtaining section.

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