Wavefield decomposition of ocean bottom multi-component seismograms with low signal-to-noise ratio
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摘要:
以多分量地震观测为基础，联合纵波和转换横波数据能更有效地估计地下介质的弹性和物性参数，提升地质构造成像与油气储层描述的精度.在海底多分量地震数据处理过程中，观测记录的上-下行波分解和P/S波分离可压制水层鸣震以及P与S波之间的串扰，对偏移成像和纵横波速度建模至关重要.但受海底环境、仪器与观测因素共同影响，许多海底多分量地震资料都无法基于现有的海底波场分离方法与流程取得合理的结果.本文以海底声波场与弹性波场分离基本原理为基础，通过对方法流程的修正，摆脱常规流程对中小偏移距直达波信号的依赖性.借助模拟数据实验讨论了波场分离对海底介质参数、噪声的敏感性.结合东海YQ探区海底多分量地震资料上-下行P/S波分离及其叠前深度偏移处理，验证了本文方法流程的可行性.
Abstract:Based on multi-component seismic observation, combined P-wave and converted S-wave data permits to more effectively estimate the elasticity and physical properties of subsurface media, and improve the accuracy of geological structure imaging and petroleum reservoir characterization. For the processing of ocean bottom seismic data, up-/down-going and P/S wave decomposition of the multi-component seismograms can suppress the water-layer reverberation and cross-talk between the P- and S-waves, and thus play a vital role in seismic migration and construction of P- and S-wave velocity models. However, affected affected by the seafloor environment, instrumental and observation factors, many ocean bottom multi-component seismic data sets have unreasonable results using the existing wavefield decomposition methods and workflow. In this paper, starting from the basic principle of acoustic and elastic wavefield decomposition, we modify the existing approach and workflow to avoid the dependence on direct waves at small-to-medium offsets. Through synthetic data experiments, we investigate the sensitivity of wavefield decomposition to seabed medium parameters and signal-to-noise ratio. Combined with the up/down and P/S decomposition and pre-stack depth migration, we demonstrate the feasibility of the proposed workflow with a multi-component seismic data set acquired by ocean-bottom seismographs (OBS) in the YQ field of the East China Sea.
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Key words:
- Multi-component /
- Ocean bottom seismograph /
- Elastic waves /
- P/S decomposition /
- East China Sea
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图 1
海底多分量地震记录波场分离示意图
Figure 1.
Schematic diagram of wavefield decomposition for ocean bottom multi-component seismic recordings
图 2
东海QY探区海底多分量共接收点记录
Figure 2.
OBS common-receiver gathers from QY area in East China Sea
图 4
二维三分量共炮点道集
Figure 4.
Synthetic two-dimensional three-component (2D3C) common-shot gathers
图 5
波场分离对海底介质参数的敏感性
Figure 5.
Sensitivity of wavefield decomposition to seabed medium parameters
图 7
vz分量频率域校正因子
Figure 7.
Calibration operator in the frequency domain for vz component
图 10
vx分量频率域校正因子
Figure 10.
Calibration operator in the frequency domain for vx component
图 11
检波器校正前后上-下行P/S模式分离结果对比
Figure 11.
Comparison of up-down P/S decomposition results before and after geophone calibration
图 16
偏移距100 m处分离的上行P/S波地震道对比
Figure 16.
Comparison of decomposed seismic traces of P- and S-waves at the offset of 100 m
图 18
声波场共接收点记录分离结果
Figure 18.
Acoustic wavefield decomposition of common-receiver gathers at the ocean bottom
图 21
海底共接收点数据弹性波场分离结果
Figure 21.
Elastic wavefield decomposition of common-receiver gathers at the ocean bottom
图 22
海底界面反射/透射系数分析
Figure 22.
Reflection and transmission coefficients at the seafloor interface
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