| 基于波动方程的上下缆地震数据鬼波压制方法研究 |
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| 引用本文： | 管西竹,陈宝书,符力耘,陶杰,李列.基于波动方程的上下缆地震数据鬼波压制方法研究[J].地球物理学报,2015,58(10):3746-3757. |
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| 作者姓名： | 管西竹 陈宝书 符力耘 陶杰 李列 |
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| 作者单位： | 1. 中国科学院油气资源研究重点实验室, 中国科学院地质与地球物理研究所, 北京 100029;
2. 中海油研究总院, 北京 100027;
3. 中海石油(中国)有限公司湛江分公司, 广东湛江 524057 |
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| 基金项目： | 国家自然科学基金项目(41130418, 40925013)和国家科技重大专项(2011ZX05025-001-02)联合资助. |
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| 摘 要： | 本文发展基于波动方程的上下缆鬼波压制方法,推导了上下缆地震波场频率波数域波动方程延拓合并公式.基于Fourier变换的波场解析延拓确保上下缆资料振幅相位的一致性,消除了长拖缆远偏移距信号的计算误差,同时具有较高的计算效率;上下缆地震波场的波动方程法合并有效解偶鬼波干涉,实现综合利用上下缆地震数据压制鬼波.理论模型数据和实际采集地震数据的测试表明了方法的有效性.
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| 关 键 词： | 海上地震采集 上下缆 鬼波压制 波动方程延拓合并 频率波数域 |
| 收稿时间： | 2014-09-19 |
The study of a deghosting method of over/under streamer seismic data based on wave equation |
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| GUAN Xi-Zhu,CHEN Bao-Shu,FU Li-Yun,TAO Jie,LI Lie.The study of a deghosting method of over/under streamer seismic data based on wave equation[J].Chinese Journal of Geophysics,2015,58(10):3746-3757. |
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| Authors: | GUAN Xi-Zhu CHEN Bao-Shu FU Li-Yun TAO Jie LI Lie |
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| Institution: | 1. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;
2. CNOOC Research Center, Beijing 100027, China;
3. CNOOC China Ltd., Guangdong Zhanjiang 524057, China |
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| Abstract: | In marine seismic acquisition, ghost effect due to the strong reflection of the sea surface causes serious notch trap in the spectrum. Ghost effect can be reduced by over/under towed streamer acquisition. However, most of deghosting technology for over/under streamer acquisition is based on seismic kinematics method, which cannot effectively solve the ghost wave interference and brings incomplete ghost suppression and distortion of the effective signal.It is necessary to develop the deghosting technology for over/under streamer. Cases studies of synthetic and real seismic data sets demonstrate that our seismic wavefield extrapolation based on Fourier transform ensures the consistency of the seismic amplitude and phase of over/under streamer seismic data and significantly eliminates the amplitude and phase error of far offset especially for the long streamer condition,which helps to decouple the real wave and the ghost wave and fill notch effect in the spectrum.
In order to take advantage of both shallow and deep streamers, it has been proposed to record the pressure field at two different depths and to combine optimally all the measurements. We propose adeghosting method of over/under streamer based on seismic wave equation continuation formula in the frequency wavenumber domain, which eliminate far offset signal calculation error of the long streamer contract to the traditional dephase and sum algorithm.The analytical seismic wave continuation based on Fourier transform ensure the consistency of the amplitude and phase of seismic signal from over/under streamer seismic acquisition with high computing efficiency, suppress the ghost signal that interference the up-going signal from the earth under water effectively and fill the notchesin the amplitude spectrum.A synthetic single shot gather is used to verify the performance of the proposed method. Finally,we apply the proposed method on a real over/undermarine data set from China. The results show that the proposed method can simultaneously achieve good imaging of shallow and deep targets, seismic data wide frequency band width by effectively suppressing the ghost.
In conventional streamer marine seismic acquisition, the pressure sensor in a towed streamer records two wavefields that interfere with each other. The two wavefields are the upgoing pressure wavefield propagating directly to the pressure sensor from the streamer below, and the downgoing pressure wavefield reflected downwards from thefree (sea) surface immediately above the streamer. The downgoing pressure wavefield like a "ghost"of the upgoing pressure wavefield. The receiver ghost from free surface cancels or degrades the signal at some frequencies, resulting steep notches in amplitude-frequency spectrum at low as well as high frequency.A streamer towed at shallow depth, the lower frequencies arestrongly attenuated and cannot be recovered by a simple deconvolution as usually the swell noise is too strong, but it is good at receiving high-frequency components, because the frequency notches shifts to higher frequency. In contrast,a streamer at a deeper depth, it is good at receiving low-frequency components and the swell noise is normally strongly attenuated for it is exponentially decaying with depth, but the notching frequencies within the bandwidth hence limiting the useful frequencies.For simplicity, we take a simple two-layered model with flat sea bottomas an example to test the method.The synthetic seismic data sets of over/under towed streamer with depth 17m and 23m without direct wave and multiple wave and the f-k spectrum of the synthetic seismic datasets. It can be seen that the arrival time of reflect wave and ghost wave in the synthetic seismic recording of 17m streamer and 23m streamer is obviously different.It can be also shown that the difference value between the up-going wave and the ghost wave at near offset and far offset increases, therefore the interference of up-going wave and ghost wave enhanced. Because of the effect of the ghost, there are periodic notches in the frequency wavenumber amplitude spectra, which are caused by the ghost.The resultshot record obtainedby the proposed method and the f-k spectrum of the resultare shown, respectively. It is clear that the proposed method can remove the ghost wave effectively and fill the notches well. To demonstrate the performance of the proposed method, we applied it on a real over/under dataset.The acquisition configuration of this dataset is set as following:An over/under source were deployed at 6 m depth and 12 m depth,and two streamers were deployed at depths of 17 m and 23 m,respectively.the shots after denoising at depths of 17 m, 23 m, and the f-k amplitude spectraof the shotsat depths of 17 m, 23 m and the shots at depth 23 m, the combined results obtained by the traditional dephase and sum method and the combined results obtained by the proposed method and the f-k amplitude spectra, it is clear that the result obtained bythe proposed method has much richer frequencies components at big wavenumber. Furthermore, the notches at small wave number are well filled and the energy is also enhanced.From the near offset primary reflection wave of the seabed in the shots at depth 23 m,the combined results obtained by the traditional dephase and sum method and the combined results obtained by the proposed method and the far offset primary reflection wave of the seabed in the shots at depth 23 m, the combined results obtained by the traditional dephase and sum method and the combined results obtained by the proposed method.It is visible that both traditional dephase and sum method and proposed method can remove the ghost well. It is shown that the wave is so distort that it is not possible to find the reflection wave.Incontrast, the reflection wave can be easy to distinguish, the wave are comprised of the reflection wave and the source ghost. Clearly the proposed method suppresses the receiver ghost better than the traditional method.
We propose a new deghosting method forover/under streamer acquisiton based on analytical f-k domain seismic wavefield extrapolation characterized by high computing efficiency. In the proposed method, the computing of the upgoing wavefield from pressure measurements acquired at different towdepths corresponding to wave equation continuation results from the data. Compared with the traditional methods, the proposed method has much richer frequencies components at big wavenumber. Furthermore, the proposed method suppresses the receiver ghost at far offset better. Synthetic and realdata examples demonstrate that the proposed method can obtains a deghosting result with rich lowand high frequencies and fill the notches in f-k amplitude spectra well. |
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| Keywords: | Marine seismic acquisition Over/under streamer Deghosting Combination based on seismic wave field continuation Frequency wavenumber domain |
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