可控震源匹配扫描方法研究
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摘要
常规的可控震源Chirp扫描信号的地震响应存在着相关信号旁瓣大、分辨率低的缺点;用二元伪随机编码信号作为可控震源的驱动信号,地震响应剖面中存在严重的相关噪声,降低了地震记录的信噪比.本文提出的可控震源匹配扫描方法,利用匹配伪随机序列偶调制正弦载波信号作为可控震源驱动信号进行扫描激发,得到两个匹配的原始地震记录,对两个匹配的原始地震记录分别解码后再进行叠加形成最终的综合解码地震剖面.地震数值模拟的结果表明,该方法基本不存在常规Chirp扫描情形的旁瓣效应,可有效避免m-序列编码扫描情形的相关噪声,其最后形成的综合解码地震剖面可以与脉冲震源的炮集记录相媲美.
Seismic response of conventional seismic vibrator driven by Chirp sweeping signals has the shortcomings of high side lobes and low resolution. When binary pseudorandom coded signals are used as seismic vibrator drive signals, there are serious correlation noises in seismic response section, reducing the signal-noise ratio. The matched sweep method for seismic vibrator put forward in this paper utilizes sine carrier signal modulated by matched pseudorandom sequence pair as seismic vibrator drive signal to sweep and excite, getting two matched original seismic records. After the two matched original seismic records are decoded, they are stacked to the final integration decoded seismic section. There are indications from results of seismic numerical simulation that the method basically does not have side-lobe effect of the conventional Chirp sweep case, which has effectively avoided correlation noises in m-sequence coded sweeping cases, and the final integration decoded seismic section can compare favorably with shot assembly records of pulse sources.
Seismic response of conventional seismic vibrator driven by Chirp sweeping signals has the shortcomings of high side lobes and low resolution. When binary pseudorandom coded signals are used as seismic vibrator drive signals, there are serious correlation noises in seismic response section, reducing the signal-noise ratio. The matched sweep method for seismic vibrator put forward in this paper utilizes sine carrier signal modulated by matched pseudorandom sequence pair as seismic vibrator drive signal to sweep and excite, getting two matched original seismic records. After the two matched original seismic records are decoded, they are stacked to the final integration decoded seismic section. There are indications from results of seismic numerical simulation that the method basically does not have side-lobe effect of the conventional Chirp sweep case, which has effectively avoided correlation noises in m-sequence coded sweeping cases, and the final integration decoded seismic section can compare favorably with shot assembly records of pulse sources.
引文
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[3] 林建民,王宝善,葛洪魁等.大容量气枪震源特征及地震波传播的震相分析.地球物理学报,2008,51(1) :206～212 Lin J M,Wang B S,Ge H K,et al.Study on large volume airgun source characteristics and seismic phase analysis.Chinese J.Geophys.(in Chinese),2008,51(1) :206～212
[4] 赵明辉,丘学林,夏少红等.大容量气枪震源及其波形特征.地球物理学报,2008,51(2) :558～565 Zhao M H,Qiu X L,Xia S H,et al.Large volume air-gun sources and its seismic waveform characters.Chinese J.Geophys.(in Chinese),2008,51(2) :558～565
[5] Chapman W L,Brown G L,Fair D W.The Vibroseis system:A high-frequency tool.Geophysics,1981,46(12) :1657～1666
[6] 姜福豪,王德江.可控震源高分辨率地震勘探采集技术--以莫桑比克2005年项目为例.石油地球物理勘探,2007,42 (2) :127～131 Jiang F H,Wang D J.Vibroseis'high resolution seismic exploration acquisition techniques:case of Mozambique project in 2005． Oil Geophysical Prospecting(in Chinese),2007,42(2) :127～131
[7] 陶知非.改善可控震源高频信号输出品质的探讨.物探装备,2008,18(2) :71～77 Tao Z F.Study on improving quality of high-frequency output signal invibroseis.EGP(in Chinese),2008,18(2) :71～77
[8] Crawford J M,Doty W E N,Lee M R.Continuous Signal Seismograph.Geophysics,1960,25(1) :95～105
[9] Goupillaud P L.Signal Design in the“Vibroseis”Technique.Geophysics,1976,41(6) :1291～1304
[10] 王忠仁,陈祖斌,张林行等.可控震源非线性扫描地震响应的数值模拟.地球物理学进展,2006,21(3) :756～761 Wang Z R,Chen Z B,Zhang L H,et al.Numerical simulation for seismic response to nonlinear sweeping signal from a vibrator.Progress in Geophysics(in Chinese),2006,21(3) :756～761
[11] Cunningham A B.Some Alternate Vilrator Signals.Geophysics,1979,44(12) :1901～1921
[12] 王忠仁,柴治媛.伪随机编码震源信号的地震响应.地球物理学进展,2007,12,22(6) :1736～1739 Wang Z R,Chai Z Y.Seismic response to pseudorandom coded vibrator signal.Progress in Geophysics(in Chinese),2007,12,22(6) :1736～1739
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