延时参数对地震信号信噪比的改善

SNR improvement of seismic signals with different time delays

当测区噪声很强,采用组合震源工作仍然不能得到高质量地震数据,为进一步提高地震信号的信噪比,引入能形成定向地震波的相控震源.相控震源产生的地震波方向可由延时参数控制,因此延时参数是影响相控地震效果的重要参数.理论分析表明,定向地震波技术可提高反射波信号信噪比,以含3个激震器的相控震源为例,信噪比可提高6.53～9.54 dB.针对延时参数分别为0,0.802,0.384,0.241,0.1 74,0.123 ms的情况,完成了野外地震实验.根据原始地震记录,得到了反射波信号功率谱,在此基础上定量地计算了不同延时参数下目标层反射信号的信噪比.结果表明,与单震源情况相比,在6种延时参数下,反射波信噪比分别提高了3.3150,8.0150,6.0547,5.0278,4.5383,4.0364 dB;与组合震源情况相比,信噪比分别提高了0,4.7000,2.7397,1.7128,1.2233,0.7214 dB.综合理论分析及野外实验结果,我们可以得到这样的结论:定向地震波技术能够提高反射波信号信噪比,延时参数变化对信噪比有很大影响,采用合理的延时参数能得到更高的信噪比.

When noise in the field is strong, it＇s difficult to obtain high SNR seismic data with single or combination vibrator. So phased-array vibrator system （PAVS）, which can form directional seismic beam, was developed. Because the orientation of the directional seismic wave is dependent on the time delay, the time delay is a dominant factor for PAVS to boost SNR of reflected signals. 3-unit PAVS is able to improve SNR by 6.53- 9. 54 dB based on theoretical analysis. Field seismic data were obtained for time delays 0, 0. 802, 0. 384, 0. 241, 0. 174, and 0. 123 ms respectively. Using the raw data with different time delays, the power spectrums of reflected seismic signals were calculated, and then quantitative SNR improvement is obtained. Compared to the case of single source, SNR increased by 3. 3150,8. 0150,6. 0547,5.0278,4. 5383, and 4. 0364 dB, respectively. Compared to the case of combination source, SNR increased by 0, 4. 7000,2. 7397,1. 7128,1. 2233,and 0. 7214 dB, respectively. On the basis of theoretical analysis and the results of field experiment, it concludes that directional seismic beam technique is useful to SNR improvement, SNR varies with time delay, proper time delay can raise SNR of reflected signals significantly.