CN103675898A - Method for quickly and accurately estimating time difference caused by stratigraphic absorption - Google Patents

Abstract

The invention relates to a method for quickly and accurately estimating time difference caused by stratigraphic absorption, which improves result fidelity in seismic data processing. The method comprises the following steps: according to the conventional seismic signal propagation time difference determination method and the conventional stratigraphic Q value estimation method, firstly determining a rough propagation time difference and a rough stratigraphic Q value, and then utilizing the obtained propagation time difference and the stratigraphic Q value to obtain the accurate value of the time difference caused by the stratigraphic Q absorption of a corresponding stratum segment through an iterative method. The value can be used for correcting the propagation time value used by the conventional treatment, and the accurate propagation time has important meaning for stratigraphic model building, speed analysis, statics correction and the like. The method has the advantages of simple principle, high computing speed and accurate and practical results.

Description

A kind of method of the time difference due to accurate estimation formation absorption fast

Technical field

The present invention relates to seismic exploration technique, is a kind of accurate method of the time difference due to estimation formation absorption fast of raising achievement fidelity during geological data is processed.

Background technology

In petroleum and natural gas seismic prospecting, the travel-time of seismic event is one of most important parameter: determining and the geological data processing procedure such as formation velocity, static correction etc. of the form of exploration targets, buried depth and inner structure, oil-gas possibility etc., all be unable to do without the travel-time of seismic event; So the travel-time is to earthquake data processing accurately, and even seismic prospecting all has very important significance.

In seismic prospecting, traditional method is that waveform by seismic wavelet when crest time, trough time and zero crossing (or) comes the travel-time of seismic wave definitely.Namely, artificial crest time, trough time or the zero crossing time that reads respectively the seismic wavelet recording two different locations on seismic propagation path, and for representing the time that arrives corresponding acceptance point, with the time that time of the late point of arrival deducts point of arrival morning, be the travel-time (this is traditional method of manually picking up) of two intersite seismic events; Or the cross correlation function between the seismic wavelet recording by two different locations on travel path is determined the travel-time (this is traditional cross-correlation method) of two intersite seismic events.The implicit basic assumption of these ways is: seismic event does not change in the form of communication process neutron deficiency, and at least the velocity of propagation of seismic wavelet different frequency component is all identical.And in fact, because stratum Q absorbs the frequency dispersion effect of the seismic event cause, seismic event is in communication process, not only there is because stratum produces to different frequency component the wave form varies that the energy attenuation relevant with frequency causes wave form varies and the time delay of also following the difference because of different frequency component velocity of propagation to cause.This makes the travel-time of the seismic event that obtains by said method can not accurately reflect propagation distance, and then to earthquake data processing, and even seismic prospecting achievement forms disturbs, and makes to estimate that the time difference that formation absorption causes produces error.

Summary of the invention

The object of the invention is to provide a kind of simple and easy to do, fast operation and the result accurate method of the time difference due to estimation formation absorption fast accurately.

Specific implementation of the present invention comprises the steps:

1) with manual type earthquake-wave-exciting in stratum, exploratory area, and at two different distance places leaving explosive source point, receive and record respectively two seismic signals and recorded geological data is done to pre-service;

Pre-service described in step 1) comprises carries out geometry definition, puts label geological data.

2) by manually pick up or computing machine automatic acquisition step 1) records two seismic signals and two acceptance points of seismic signal between propagation time difference t;

Step 2) described manually picks up take-off time, crest time or the trough time of reading seismic signal by naked eyes that refers to.

Step 2) described computing machine automatic acquisition refers to by two signals being carried out to simple crosscorrelation or obtaining the mistiming t between the two by similar method.

3) ask for respectively the spectral amplitude of two seismic signals that step 1) records, utilize step 2) in mistiming t, with logarithmic spectrum, than method, determine the average Q value Q of stratomere between two acceptance points;

4) according to step 2) in the average Q value Q that obtains in resulting mistiming t and step 3), frequency band matching seismic signal being dominant with following formula obtains the approximate time difference value Δ t that stratum Q between two measuring point absorbs the seismic wave propagation causing:

$\mathrm{\Δt}=-\frac{\frac{\underset{\mathrm{\ω}}{\mathrm{\Σ}}\frac{{\mathrm{\ω}}^{2}t}{\mathrm{\πQ}}}{\ln (\mathrm{\ω}/{\mathrm{\ω}}_c)}+1}{\underset{\mathrm{\ω}}{\mathrm{\Σ}}{\mathrm{\ω}}^2}---\left(1\right)$

In formula, ω is circular frequency; ω _cfor given reference frequency; π is circular constant;

5) approximate time difference value Δ t step 4) being obtained is from step 2) mistiming t deduct, repeating step 3 afterwards) and 4), again obtain stratum Q between two measuring point and absorb the seismic wave propagation time difference value Δ t causing;

Repeated execution of steps 3) to step 5), the seismic wave propagation time difference that obtains making stratum Q between two measuring point to absorb causing and the propagation time difference t actual value between two acceptance points;

6) the seismic prospecting signal repeating step 1 to the Different Strata interval record of same exploratory area) to step 5), obtaining respectively corresponding interval stratum Q absorbs the seismic wave propagation time difference value causing.

It is simple that the present invention has principle, fast operation, and result is accurately practical.

Fig. 1 is for verifying the gross data result of the inventive method accuracy.According to Futterman model calculated Propagation that 40 hertz of Ricker wavelets are 120 in Q value waveform after 500 milliseconds and 1500 milliseconds and the time arriving.Fig. 1 can see near 500 milliseconds and 1500 milliseconds due to formation absorption caused obvious waveform and time of arrival difference two wavelets.Between existing definite these two wavelets, propagating the method for the time difference is the time difference of manually picking up between the two corresponding crest (or trough), or determines the mistiming between the two by the simple crosscorrelation of two wavelets.

Table 1 has provided the comparing result to method of the present invention and existing time difference pick-up method gained propagation time difference computational estimation competence in the gross data shown in Fig. 1, the real propagation time difference is 1000 milliseconds, and the time difference of traditional (simple crosscorrelation and peak picking) method gained is 1018 milliseconds, relative error is 1.8%; And use method of the present invention, only once iteration correction is just propagated gained the evaluated error of the time difference and has been reduced to 0.0427%.Obviously, it is very fast that the present invention approaches the speed of true value.

Accompanying drawing explanation

Fig. 1 is for verifying the data result schematic diagram of accuracy of the present invention.

Embodiment

Below in conjunction with example in detail the present invention.

Stratum Q absorbs and to refer to that seismic event is in stratum in communication process, and each frequency component of ripple can experience the energy becoming with propagation distance, frequency and stratum physical attribute (quality factor) and decays and propagate this objective physical phenomenon with different speed.The physical attribute that stratum produces absorption to seismic event is commonly referred to stratum quality factor (Quality factor), getting its initial Q represents, by the size of stratum quality factor q, Q value namely, the intensity of coming quantitative description stratum to absorb seismic event, it is a dimensionless physical quantity; This concept of stratum quality factor be seismic prospecting from physics or engineering, use for describing a physical quantity---the system quality factor of damped oscillation system capacity attenuation properties.

If want, estimate and eliminate the time difference that above-mentioned formation absorption causes, need to predict the mathematical model of formation absorption.Forefathers are doing a large amount of work aspect formation absorption effect, provided different formation absorption mathematical models.The most representative at present, also being most widely used, is that Futterman1962 is in " Dispersive body waves " (Geophysics reprint series, 1981,2,405 – 417.) mathematical model (being called again Futterman model) providing in a literary composition.

The present invention is according to the described dispersion relation of Futterman model, provided the quantitative expression of the time difference that formation absorption causes, and by the mode of iterative approach, sub-wave phase carried out to linear fit, thereby obtained the time difference that formation absorption causes.

The specific embodiment of the invention is as follows:

1) with manual type earthquake-wave-exciting in stratum, exploratory area, and at two different distance places leaving explosive source point, receive and record respectively two seismic signals and recorded seismic signal (being called again geological data) is done to pre-service;

Pre-service described in step 1) comprises carries out geometry definition, puts the contents such as label geological data.

2) by manually pick up or computing machine automatic acquisition step 1) records two seismic signals and two acceptance points of seismic signal between propagation time difference t;

Step 2) described manually picks up take-off time, crest time or the trough time of reading seismic signal by naked eyes that refers to.

Step 2) described computing machine automatic acquisition refers to by two signals being carried out to simple crosscorrelation or obtaining the mistiming t between the two by similar method;

3) ask for respectively the spectral amplitude of two seismic signals that step 1) records, and with logarithmic spectrum, than method, determine the average Q value Q of stratomere between two acceptance points; Step 2) the mistiming t in will participate in than method at logarithmic spectrum calculating;

4) according to step 2) in the average Q value Q that obtains in resulting mistiming t and step 3), frequency band matching seismic signal being dominant with following formula obtains the approximate time difference value Δ t that stratum Q between two measuring point absorbs the seismic wave propagation causing:

$\mathrm{\Δt}=-\frac{\frac{\underset{\mathrm{\ω}}{\mathrm{\Σ}}\frac{{\mathrm{\ω}}^{2}t}{\mathrm{\πQ}}}{\ln (\mathrm{\ω}/{\mathrm{\ω}}_c)}+1}{\underset{\mathrm{\ω}}{\mathrm{\Σ}}{\mathrm{\ω}}^2}---\left(1\right)$

In formula: ω is circular frequency; ω _cfor given reference frequency; π is circular constant;

5) approximate time difference value Δ t step 4) being obtained is from step 2) mistiming t deduct, repeating step 3 afterwards) and 4), again obtain stratum Q between two measuring point and absorb the seismic wave propagation time difference value Δ t causing;

Repeated execution of steps 3) to step 5), the seismic wave propagation time difference that obtains making stratum Q between two measuring point to absorb causing and the propagation time difference t actual value between two acceptance points;

6) the seismic prospecting signal repeating step 1 to the Different Strata interval record of same exploratory area) to step 5), obtaining respectively corresponding interval stratum Q absorbs the seismic wave propagation time difference value causing.

Adopt following steps to test the present invention:

1) by the Ricker wavelet of 40 hertz, do source wavelet, quality factor (namely Q) value of getting stratum is 120.

2) according to Futterman model, calculate in the stratum that source wavelet is 120 in this quality factor and propagate 500 milliseconds and 1000 milliseconds, and experience waveform after Amplitude absorbing and frequency dispersion effect and by these two theoretical seismograms that waveform forms.The results are shown in Figure 1.

3) by manually picking up the method for crest, on the theoretical seismogram shown in Fig. 1, ask for the propagation time difference between two seismic wavelets that propagate into 500 milliseconds and 1000 milliseconds.The results are shown in Table 1.

4) by cross-correlation method, on the theoretical seismogram shown in Fig. 1, ask for the propagation time difference between two seismic wavelets that propagate into 500 milliseconds and 1000 milliseconds.The results are shown in Table 1.

5) with the present invention, the theoretical seismogram shown in Fig. 1 is carried out to step 2 of the present invention) to the operation of step 5), obtain revised propagation time difference as shown in table 1.

" true value " in travel-time, " the peak value time difference of manually picking up " in contrast table 1, " time difference that cross-correlation method picks up " and with the revised time difference of the present invention, visible the present invention only need once calculate and just can obtain the result very approaching with true value.

Claims (4)

1. the quick accurately method of the time difference due to estimation formation absorption, feature is to adopt following steps to realize:

1) with manual type earthquake-wave-exciting in stratum, exploratory area, and at two different distance places leaving explosive source point, receive and record respectively two seismic signals and recorded geological data is done to pre-service;

2) by manually pick up or computing machine automatic acquisition step 1) records two seismic signals and two acceptance points of seismic signal between propagation time difference t;

3) ask for respectively the spectral amplitude of two seismic signals that step 1) records, utilize step 2) in mistiming t, with logarithmic spectrum, than method, determine the average Q value Q of stratomere between two acceptance points;

4) according to step 2) in the average Q value Q that obtains in resulting mistiming t and step 3), frequency band matching seismic signal being dominant with following formula obtains the approximate time difference value Δ t that stratum Q between two measuring point absorbs the seismic wave propagation causing:

$\mathrm{\Δt}=-\frac{\frac{\underset{\mathrm{\ω}}{\mathrm{\Σ}}\frac{{\mathrm{\ω}}^{2}t}{\mathrm{\πQ}}}{\ln (\mathrm{\ω}/{\mathrm{\ω}}_c)}+1}{\underset{\mathrm{\ω}}{\mathrm{\Σ}}{\mathrm{\ω}}^2}---\left(1\right)$

In formula, ω is circular frequency; ω _cfor given reference frequency; π is circular constant;

5) approximate time difference value Δ t step 4) being obtained is from step 2) mistiming t deduct, repeating step 3 afterwards) and 4), again obtain stratum Q between two measuring point and absorb the seismic wave propagation time difference value Δ t causing;

Repeated execution of steps 3) to step 5), the seismic wave propagation time difference that obtains making stratum Q between two measuring point to absorb causing and the propagation time difference t actual value between two acceptance points;

6) the seismic prospecting signal repeating step 1 to the Different Strata interval record of same exploratory area) to step 5), obtaining respectively corresponding interval stratum Q absorbs the seismic wave propagation time difference value causing.

2. method according to claim 1, feature is that the pre-service described in step 1) comprises to geological data is carried out geometry definition, puts label.

3. method according to claim 1, feature is step 2) described manually picking up take-off time, crest time or the trough time of reading seismic signal by naked eyes that refers to.

4. method according to claim 1, feature is step 2) described computing machine automatic acquisition refers to by two signals being carried out to simple crosscorrelation or obtaining the mistiming t between the two by similar method.