基于接收阵列的时域地震波束形成方法

摘要

In order to improve signal-to-noise ratio (SNR) in seismic exploration, we propose "Time-domain Seismic Beam-forming Based on Receiver Array" (TSBBRA), which is based on beam-forming theory. On the basis of wave field analysis to phased-array vibrator systemrn (PAVS), the idea of beamforming at receiver arrays is deduced in seismic data processing. Here we give two steps of TSBBRA: the first one is to separate seismic shot records into different groups, and the second is to generate directional seismic records by time delay and sum process. TSBBRA is more useful when direction of reflected waves from the target layer is not consistent with interference waves. We show the directional wave field from TSBBRA using wave field simulation, and compare time profiles from PAVS and TSBBRA. The results indicate the feasibility of TSBBRA. Finally, we show a TSBBRA result profile from the oil shale area in Jilin Province. Comparing the raw data, SNR increases 3 to 35 dB and depth of identified reflectors is extended from 200 ms to 1000 ms. And signals from seismic marker horizons are consistent with geological and geophysical data in the neighborhood. These demonstrate that TSBBRA is helpful to improve SNR and exploration depth in seismic data acquisition during exploration. Moreover, TSBBRA is more applicable in deep exploration.%地震勘探中,针对目的层地震数据信噪比较低情况,为改善信噪比,本文提出一种基于接收阵列的时域地震波束形成方法(TSBBRA).该方法的理论依据是波束形成原理,文中通过对相控震源激发定向地震波场的分析,提出在反射地震勘探中,在信号接收端同样能生成定向地震波的思路.具体地,论文给出在地震数据集上先对单炮记录分组,再对组内记录时域内延时、叠加,生成对应定向地震波场的地震记录的方法.TSBBRA方法适于杂波干扰强,且杂波与目的层反射波方向不一致的地震条件.本文先通过波场模拟,展示了TSBBRA方法具有形成定向地震波场的能力；而后通过对比相控震源与TSBBBRA时间剖面,说明了TSBBRA方法的有效性；最后在吉林某油页岩矿区,用TSBBRA方法,分别针对浅层目标与深层目标,生成定向地震波数据.与原始数据相比,目标层信噪比提高了3～35 dB,在时间剖面上观测到的深部目标信号从200 ms扩展到1000 ms,TSBBRA剖面资料与测区附近区域的地质与地震资料一致.由此得出结论,TSBBRA方法有助于改善目的层地震资料信噪比,当关注深部目的层时,由于TSBBRA方法能有效压制噪声,因此可用于能够实现更大的勘探深度.实验中,我们给出了浅层勘探结果,由于本方法对震源及观测系统没有限制,实际应用中TSBBRA方法可作为深部资源勘探领域提高深部地震资料信噪比的有效方法.