CN102798889A - Phased source consistency determining method - Google Patents

Phased source consistency determining method Download PDF

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CN102798889A
CN102798889A CN2012101252918A CN201210125291A CN102798889A CN 102798889 A CN102798889 A CN 102798889A CN 2012101252918 A CN2012101252918 A CN 2012101252918A CN 201210125291 A CN201210125291 A CN 201210125291A CN 102798889 A CN102798889 A CN 102798889A
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phased
signal
source
focus
consistance
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CN102798889B (en
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姜弢
林君
徐学纯
冯博
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Jilin University
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Jilin University
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Abstract

The invention relates to a phased source consistency determining method. The determining method comprises the following steps that: the vertical positioning accuracy error of a phased source is not more than 2m; for the improvement capability of an actual signal-to-noise ratio compared with a theoretical value, the signal-to-noise ratio decreases by not more than 3 dB; each source excitation signal has high linearity; different source signals are superposed in an out-of-phase manner to cause the signal signal-to-noise ratio; the phases of two quantitative signal waveforms are consistent; and if the conditions are met, the phased sources are regarded as consistent phased sources; otherwise, the phased sources are regarded as inconsistent phased sources. Tests prove that the determining method is applicable to the consistency testing process of any phased sources, combined sources and a plurality of controlled sources, and provides necessary collection quality assurance measures for field data collection of phased source seismic prospecting methods. Testing results show that the signal-to-noise ratio of the collected data is improved to a great extent. The phased source consistency determining method provides a basis for phased source performance evaluation, phased source system maintenance and effective collection of phased source seismic data, and simultaneously also can provide effective technical means for phased source maintenance and qualification testing.

Description

Phased focus consistance decision method
Technical field:
The present invention relates to a kind of method of seismic prospecting, the conforming decision method of especially phased focus.
Background technology:
The vibroseis method of seismic prospecting, since destructive to the nothing of environment, in seismic prospecting, receive all the more widely and paying close attention to.The subject matter that the vibroseis seismic prospecting exists is that ground unrest is strong a little less than the seismic source energy, and it is lower to receive the data signal to noise ratio (S/N ratio).For improving the Seismic Source System power output, improve the vibroseis earthquake data quality, can adopt phased Seismic Source System.Phased focus is an a kind of array focus technology, to each focus of participating in work consistance of having relatively high expectations, and does not still have phased focus method for evaluating consistency at present.Do not judge if do not carry out consistance, can't guarantee directionally seismic wave of phased epicenter excitation, the false reflection ripple can occur in the seismic exploration data, cause explanation of error, cause phased focus unavailable underground structure.Be that phased focus consistance decision method guarantees to mention necessary condition before phased focus method of seismic prospecting is used.
Summary of the invention:
The object of the invention just is the deficiency to above-mentioned prior art, and a kind of phased focus consistance decision method is provided.
To the requirement of vibroseis high precision seismic exploration, phased focus consistance decision criteria has been proposed.According to this criterion, proposing a kind of is main with correlation analysis in time domain, and adopting Fourier transform (FFT) spectrum analysis is the phased focus consistance quantitative judgement method of assisting.Through this method, can guarantee to satisfy consistency criterion's phased Seismic Source System, vertical bearing accuracy error is no more than 2m; Actual signal to noise ratio (S/N ratio) improvement ability is compared with theoretical value, and signal to noise ratio (S/N ratio) descends and is no more than 3dB; To the Seismic Source System that does not meet coherence request, except that the time-domain analysis method, in frequency field, give the auxiliary quantity fractional analysis method of inconsistency, for the adjustment of focus, safeguard foundation is provided.
The main advantage of the inventive method is following two aspects: the one, and phased focus consistance has been provided quantitative analysis method, and the consistance judgement has been linked together with the seismic prospecting precision; The 2nd, the inventive method is that open-air phased focus high-quality earthquake data acquisition provides necessary guarantee.
The object of the invention is realized in the following manner:
Phased focus consistance decision method comprises following order and step:
Step 1, to the high precision seismic exploration demand, at first confirm conformance criteria, promptly satisfy the following system that requires and be considered to consistent: phased focus geological data is after coherent detection, and vertical bearing accuracy error is no more than 2m; Actual signal to noise ratio (S/N ratio) improvement ability is compared with theoretical value, and signal to noise ratio (S/N ratio) descends and is no more than 3dB; Each epicenter excitation signal has the higher linearity;
Step 2, at first according to above-mentioned conformance criteria, provides phased focus correlation analysis in time domain evaluation method, and the phased focus of specific requirement consistance should satisfy following three conditions simultaneously:
(1) it is non-with the superimposed Signal-to-Noise decline situation that causes at first to analyze different source signals.If s 1(t), s 2(t) represent two different source signals.By phased focus principle of work, be positioned at the wave detector in far field, the phased source signal of objective body reflection can be expressed as
S 2(t)＝s 1(t)+s 2(t)(1)
Work as s 1(t)=s 2(t), promptly two source signals are in full accord, then obtain desirable phased source signal
S 1(t)＝s 1(t)+s 1(t)(2)
If
Figure DEST_PATH_GDA00001684823100021
is related operation symbol, order
R 2 ( t ) = S 2 ( t ) ⊗ s 1 ( t ) R 1 ( t ) = S 1 ( t ) ⊗ s 1 ( t ) - - - ( 3 )
Calculate R 2(t) than R 1(t) signal to noise ratio (S/N ratio) decline degree if be no more than 3dB, then satisfies first condition that consistance is judged;
(2) consider that the vertical positioning error of phased Seismic Source System is not more than the requirement of 2m.After coherent detection, can occur the main lobe time shift with superimposed seismic event owing to non-, this time shift will cause the vertical positioning error on stratum.Base area seismic wave kinematics can know that establishing underground medium average velocity is V, and the formation at target locations depth D to the double whilst on tour T of seismic event, exists
2D＝V*T (4)
It is thus clear that, if vertical bearing accuracy error is Δ D, then double whilst on tour error
ΔT＝2ΔD/V (5)
In p wave interval velocity is 1400～3500m/s, and for Δ D≤2m, Δ T is no more than 1.14～2.86ms.Be R 2(t) maximum of points and ideal signal R 1(t) maximum of points time corresponding error should be no more than 1.14～2.86ms, and this is second condition that consistance is judged;
(3) employing method has the relative analysis method method, quantizes the phase equalization of two signal waveforms, and two source signal cross-correlation coefficients of specific requirement are not less than 0.95, and this is the 3rd condition that consistance is judged;
(4) if phased focus satisfies above-mentioned 3 conditions, be regarded as the phased source of consistance, judge and finish; Otherwise, being regarded as the phased focus of nonuniformity, execution in step three is further analyzed;
Step 3, do not satisfy the phased focus of coherence request,, can increase phased focus consistance assistant analysis link in the frequency field in order to grasp inconsistent concrete characteristic to time-domain analysis; Method is following: adopt the FFT method, ask its amplitude-frequency and phase frequency characteristic, thereby obtain the response characteristic difference of each focus at different frequency range, instruct the adjusting and the maintenance of focus;
Beneficial effect: through test; Phased focus consistance decision method disclosed by the invention; Be suitable for the consistency detection process of any phased focus, combination focus and many vibroseiss, be the field data collection of phased focus method of seismic prospecting, necessary acquisition quality safeguard measure is provided; Testing result shows that the image data signal to noise ratio (S/N ratio) is improved largely.For phased focus performance evaluation, phased Seismic Source System are safeguarded, phased focus geological data is effectively gathered foundation is provided.Simultaneously, the present invention can be used as also that phased focus is safeguarded and qualified detection provides the effect technique means.
Description of drawings:
Fig. 1 is 2 source signal time domain waveforms of phased focus consistance decision method comparison diagram;
Fig. 2 is 2 source signal coherent detections of phased focus consistance decision method comparison diagrams as a result;
Fig. 3 is another group source signal amplitude spectrum and phase spectrum comparison diagram of phased focus consistance decision method;
(a) amplitude spectrogram, (b) phase place spectrogram.
Embodiment
Phased focus consistance decision method, to the requirement of vibroseis high precision seismic exploration, proposing a kind of is main with correlation analysis in time domain, the FFT spectrum analysis is the comprehensive quantitative evaluation method of assisting.Through this decision method, can guarantee to satisfy consistency criterion's phased Seismic Source System, vertical bearing accuracy error is no more than 2m; Actual signal to noise ratio (S/N ratio) improvement ability is compared with theoretical value, and signal to noise ratio (S/N ratio) descends and is no more than 3dB; To the Seismic Source System that does not meet coherence request, except that the time-domain analysis result, in frequency field, give inconsistent auxiliary quantification and judge, for the adjustment of focus, safeguard foundation is provided.The inventive method is for guaranteeing that phased focus earthquake data acquisition quality provides the necessary apparatus quality judging method.
Be example with the phased focus in Unit 2 in the present embodiment, explained that consistance judges concrete grammar.
The enforcement order and the step of method are following:
1, phased focus consistance decision method comprises following order and step:
Step 1, to the high precision seismic exploration demand, at first confirm conformance criteria, promptly satisfy the following system that requires and be considered to consistent: phased focus geological data is after coherent detection, and vertical bearing accuracy error is no more than 2m; Actual signal to noise ratio (S/N ratio) improvement ability is compared with theoretical value, and signal to noise ratio (S/N ratio) descends and is no more than 3dB; Each epicenter excitation signal has the higher linearity;
Step 2, at first according to above-mentioned conformance criteria, provides phased focus correlation analysis in time domain decision method, and the phased focus of specific requirement consistance should satisfy following three conditions simultaneously:
(1) it is non-with the superimposed Signal-to-Noise decline situation that causes at first to analyze different source signals.If s 1(t), s 2(t) represent two different source signals.By phased focus principle of work, be positioned at the wave detector in far field, the phased source signal of objective body reflection can be expressed as
S 2(t)＝s 1(t)+s 2(t)(1)
Work as s 1(t)=s 2(t), promptly two source signals are in full accord, then obtain desirable phased source signal
S 1(t)＝s 1(t)+s 1(t)(2)
If is related operation symbol, order
R 2 ( t ) = S 2 ( t ) ⊗ s 1 ( t ) R 1 ( t ) = S 1 ( t ) ⊗ s 1 ( t ) - - - ( 3 )
Calculate R 2(t) than R 1(t) signal to noise ratio (S/N ratio) decline degree if be no more than 3dB, then satisfies first condition that consistance is judged;
(2) consider that the vertical positioning error of phased Seismic Source System is not more than the requirement of 2m.After coherent detection, can occur the main lobe time shift with superimposed seismic event owing to non-, this time shift will cause the vertical positioning error on stratum.Base area seismic wave kinematics can know that establishing underground medium average velocity is V, and the formation at target locations depth D to the double whilst on tour T of seismic event, exists
2D＝V*T (4)
It is thus clear that, if vertical bearing accuracy error is Δ D, then double whilst on tour error
ΔT＝2ΔD/V (5)
In the p wave interval velocity is 1400-3500m/s, and for Δ D≤2m, Δ T is no more than 1.14-2.86ms.Be R 2(t) maximum of points and ideal signal R 1(t) maximum of points time corresponding error should be no more than 1.14-2.86ms, and this is second condition that consistance is judged;
(3) employing method has correlation analysis method, quantizes the phase equalization of two signal waveforms, and two source signal cross-correlation coefficients of specific requirement are not less than 0.95, and this is the 3rd condition that consistance is judged;
(4) if phased focus satisfies above-mentioned 3 conditions, be regarded as the phased source of consistance, judge and finish; Otherwise, be regarded as the phased focus of nonuniformity, but execution in step three is analyzed further;
To one group of phased focus of embodiment, the time domain waveform sig.1 and the sig.2 of two source signals are as shown in Figure 1, can find out that sig.1 is consistent with the wave form varies trend of sig.2; Use the time domain method for evaluating consistency that sample data sig.1 and sig.2 are analyzed, reality that obtains and desirable phased focus seismic wavelet are shown in Fig. 2 (a), and Fig. 2 (b) is that the waveform of Fig. 2 (a) amplifies.Can be known that by Fig. 2 the seismic event of the epicenter excitation in the phased Seismic Source System then deviation is 0, signal to noise ratio (S/N ratio) drops to 0.4242dB, and less than 3dB, related coefficient is 0.9850, meets coherence request.Actual phased focus output signal is compared signal to noise ratio (S/N ratio) decline 0.4242dB with theory output signal, satisfies less than the 3dB condition;
Step 3, do not satisfy the phased focus of coherence request,, can increase phased focus consistance assistant analysis link in the frequency field in order to grasp inconsistent concrete characteristic to time-domain analysis; Method is following: adopt the FFT method, ask its amplitude-frequency and phase frequency characteristic, thereby obtain the response characteristic difference of each focus at different frequency range, instruct the adjusting and the maintenance of focus.
Can be known that by Fig. 2 and Fig. 3 in the 150Hz frequency range, bigger deviation has appearred in amplitude at 130Hz for the time domain waveform sig.3 of two source signals and sig.4, the changes in amplitude trend of two groups of data changes basically identical in other frequency ranges, but that amplitude has is more different.Concrete, in 120～140Hz frequency range, the amplitude of sig.3 is greater than sig.4, and in 140～200Hz frequency range, then is the amplitude of sig.4 greater than sig.3; Sig.3 and sig.4 phase spectrum variation tendency are basic identical, but the phase place of sig.3 is more leading than the phase place of sig.4 generally, have caused the overall consistance of system deviation to occur.

Claims (1)

1. a phased focus consistance decision method is characterized in that, may further comprise the steps:
Step 1, to the high precision seismic exploration requirement, at first confirm conformance criteria, promptly satisfy the following system that requires and be considered to consistent: the vertical bearing accuracy error of phased focus geological data is no more than 2m; Actual signal to noise ratio (S/N ratio) improvement ability is compared with theoretical value, and signal to noise ratio (S/N ratio) descends and is no more than 3dB; Each epicenter excitation signal has the higher linearity;
Step 2, according to above-mentioned conformance criteria, provide phased focus correlation analysis in time domain decision method, the phased focus of specific requirement consistance should satisfy following three conditions simultaneously:
(1) it is non-with the superimposed Signal-to-Noise decline situation that causes at first to analyze different source signals, establishes s 1(t), s 2(t) represent two different source signals, be positioned at the wave detector in far field, the phased source signal of objective body reflection can be expressed as
S 2(t)＝s 1(t)+s 2(t) (1)
Work as s 1(t)=s 2(t), promptly two source signals are in full accord, then obtain desirable phased source signal
S 1(t)＝s 1(t)+s 1(t) (2)
If
Figure FDA0000157526070000011
is related operation symbol, order
R 2 ( t ) = S 2 ( t ) ⊗ s 1 ( t ) R 1 ( t ) = S 1 ( t ) ⊗ s 1 ( t ) - - - ( 3 )
Calculate R 2(t) than R 1(t) signal to noise ratio (S/N ratio) decline degree if be no more than 3dB, then satisfies first condition that consistance is judged;
(2) consider that the vertical positioning error of phased Seismic Source System is not more than the requirement of 2m; After coherent detection, can occur the main lobe time shift with superimposed seismic event owing to non-, this time shift will cause the vertical positioning error on stratum, and base area seismic wave kinematics can be known; If underground medium average velocity is V; The formation at target locations depth D to the double whilst on tour T of seismic event, exists
2D＝V*T (4)
It is thus clear that, if vertical bearing accuracy error is Δ D, then double whilst on tour error
ΔT＝2ΔD/V (5)
In the p wave interval velocity is 1400-3500m/s, and for Δ D≤2m, Δ T is no more than 1.14-2.86ms, i.e. R 2(t) maximum of points and ideal signal R 1(t) maximum of points time corresponding error should be no more than 1.14-2.86ms, and this is second condition that consistance is judged;
(3) adopt correlation analysis method, quantize the phase equalization of two signal waveforms, specific requirement is that two source signal cross-correlation coefficients are not less than 0.95, and this is the 3rd condition that consistance is judged;
(4) if phased focus satisfies above-mentioned 3 conditions, be regarded as the phased source of consistance, judge and finish; Otherwise, being regarded as the phased focus of nonuniformity, execution in step three is further judged;
Step 3, do not satisfy the phased focus of coherence request, adopt Fourier transform (FFT) method, ask its amplitude-frequency and phase frequency characteristic, thereby obtain the response characteristic difference of each focus, instruct the adjusting and the maintenance of focus at different frequency range to time-domain analysis.
CN201210125291.8A 2012-04-26 2012-04-26 Phased source consistency determining method Expired - Fee Related CN102798889B (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104536046A (en) * 2014-12-26 2015-04-22 吉林大学 Focus excitation signal consistency evaluating method based on earthquake records
CN104536034A (en) * 2015-01-08 2015-04-22 吉林大学 Multi-seismic-resource parallel motivation collecting and hybrid seismic record separating method
CN112180469A (en) * 2019-07-03 2021-01-05 中国石油天然气集团有限公司 Method for testing consistency of seismic source cable

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Publication number Priority date Publication date Assignee Title
CN1560651A (en) * 2004-03-03 2005-01-05 吉林大学 Phased array seismic prospecting method

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CN1560651A (en) * 2004-03-03 2005-01-05 吉林大学 Phased array seismic prospecting method

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104536046A (en) * 2014-12-26 2015-04-22 吉林大学 Focus excitation signal consistency evaluating method based on earthquake records
CN104536046B (en) * 2014-12-26 2017-03-29 吉林大学 Epicenter excitation signal conformance evaluation methodology based on earthquake record
CN104536034A (en) * 2015-01-08 2015-04-22 吉林大学 Multi-seismic-resource parallel motivation collecting and hybrid seismic record separating method
CN104536034B (en) * 2015-01-08 2017-02-22 吉林大学 Multi-seismic-resource parallel motivation collecting and hybrid seismic record separating method
CN112180469A (en) * 2019-07-03 2021-01-05 中国石油天然气集团有限公司 Method for testing consistency of seismic source cable
CN112180469B (en) * 2019-07-03 2023-10-27 中国石油天然气集团有限公司 Method for testing wired consistency of seismic source

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