起伏海面背景下的鬼波压制方法研究
发布时间：2018-10-11 19:43
【摘要】：海洋拖缆采集中,检波器接收到的记录包括来自地下反射界面的一次反射波和一次反射波到经过海水表面反射到达检波器的虚反射(鬼波)。鬼波紧随一次波后,与一次波相互干涉,改变了一次反射波的波形特征,甚至产生虚假的同相轴。此外,鬼波的陷频特性,使得地震资料频带变窄,降低了地震资料的分辨率,给地震资料反演、解释带来了困难。高分辨率的宽频带地震资料是实现对地下复杂地质体精确成像的先决条件,为了得到高分辨率的宽频带地震资料,地震资料处理过程中需要对鬼波进行压制。鬼波压制过程中,起伏海面是不可忽略的一个影响因素。然而,目前针对单分量拖缆鬼波压制的方法都是基于平坦海表面的假设,导致对鬼波算子参数(海表面反射系数、鬼波延迟时间)估计不准确,使得鬼波压制不完全,去鬼波结果中引入不必要的窜扰噪音,陷波点能量得不到较好的恢复。针对以上问题,本文首先对鬼波的产生机理进行了研究。然后介绍了频率-时间域、频率-波数域、拉东域常规鬼波压制方法的原理和适用条件,并分析了起伏海表面对鬼波压制效果的影响。最后提出了起伏海面背景下的频率域自适应鬼波压制方法和拉东域鬼波压制方法,实现对鬼波的精准压制,为海上地震资料的鬼波压制提供了技术支持。基于信号峭度最大化的频率域自适应鬼波压制方法,通过定义峭度系数来评价去鬼波结果的质量,通过设定搜索范围,对鬼波延迟时间进行搜索,能自适应准确估计最优反射系数和鬼波延迟时间,达到自适应压制鬼波的目的。该方法无论是在平坦海表面背景或者起伏海表面背景下,都能有效地压制鬼波,使得陷波点处的能量得到恢复,地震剖面的频带宽度得到拓宽。基于海表面成像的拉东域鬼波压制方法,通过求解最小线性拉东方程得到海表面处上行波场,正向和反向延拓海表面处上行波场至检波器处,利用最小二乘反演精确求解获得海表面处上行波场,采用最小平方成像条件成像海表面,进而校正检波器实际沉放深度来消除起伏海面的影响,实现了起伏海面背景下鬼波的压制。方法通过考虑起伏海表面对鬼波的影响,改善基于平坦海表面假设下鬼波压制不完全的情况。数值模拟数据和海上实际拖缆数据测试结果表明,该方法能更好地压制鬼波,最大程度拓宽地震记录频带。
[Abstract]:In the acquisition of ocean towing cables, the records received by the geophone include one reflection from the underground reflection interface and one reflection wave to the virtual reflection (ghost wave) which is reflected through the sea water surface to the geophone. After the first wave, the ghost wave interacts with the first wave, which changes the waveform characteristics of the first reflection wave, and even produces a false cophase axis. In addition, the notch frequency characteristic of ghost wave makes the frequency band of seismic data narrow, reduces the resolution of seismic data, and brings difficulties to inversion and interpretation of seismic data. Broadband seismic data with high resolution is a prerequisite for accurate imaging of underground complex geological bodies. In order to obtain broadband seismic data with high resolution, ghost waves need to be suppressed in the process of seismic data processing. In the process of ghost wave suppression, undulating sea surface is a factor that can not be ignored. However, the current methods for suppressing ghost waves by single component towing cable are based on the assumption of flat sea surface, which leads to inaccurate estimation of the parameters of ghost wave operator (reflection coefficient of sea surface, delay time of ghost wave), which makes the suppression of ghost waves incomplete. When unnecessary noise is introduced into the deconvolution result, the energy of the notch point can not be recovered well. In order to solve the above problems, the mechanism of ghost wave is studied in this paper. Then the principle and applicable conditions of conventional ghost wave suppression methods in frequency-time domain, frequency-wavenumber domain and Radon domain are introduced, and the influence of the surface of undulating sea on the suppression effect of ghost waves is analyzed. Finally, the adaptive suppression method in frequency domain and the ghost wave suppression method in Radon region in the background of undulating sea surface are proposed to achieve the accurate suppression of ghost wave, which provides technical support for the suppression of ghost wave in seismic data on the sea. Based on the frequency domain adaptive ghost suppression method based on the maximum kurtosis of signal, the kurtosis coefficient is defined to evaluate the quality of the deghost result, and the delay time of the ghost wave is searched by setting the search range. The optimal reflection coefficient and ghost delay time can be estimated adaptively and accurately, and the purpose of adaptive suppression of ghost wave can be achieved. This method can suppress ghost wave effectively in the background of flat sea surface or undulating sea surface, so that the energy at the notch point can be restored and the band width of seismic section can be widened. On the basis of sea surface imaging, the ghost wave suppression method in Lato domain is used to obtain the upward wave field at the sea surface by solving the minimum linear eastward path, and the upstream wave field from the forward and reverse extending sea surface to the geophone. The up-going wave field at the sea surface is obtained by using the least square inversion, and the least square imaging condition is used to image the sea surface, and then the actual sinking depth of the geophone is corrected to eliminate the influence of the undulating sea surface. The suppression of ghost waves under the background of undulating sea surface is realized. Methods the influence of undulating sea surface on ghost wave was considered to improve the incomplete suppression of ghost wave on the assumption of flat sea surface. The numerical simulation data and the actual towed cable data at sea show that the method can suppress ghost waves better and widen the seismic record frequency band to the greatest extent.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P631.4
本文编号：2265020
[Abstract]:In the acquisition of ocean towing cables, the records received by the geophone include one reflection from the underground reflection interface and one reflection wave to the virtual reflection (ghost wave) which is reflected through the sea water surface to the geophone. After the first wave, the ghost wave interacts with the first wave, which changes the waveform characteristics of the first reflection wave, and even produces a false cophase axis. In addition, the notch frequency characteristic of ghost wave makes the frequency band of seismic data narrow, reduces the resolution of seismic data, and brings difficulties to inversion and interpretation of seismic data. Broadband seismic data with high resolution is a prerequisite for accurate imaging of underground complex geological bodies. In order to obtain broadband seismic data with high resolution, ghost waves need to be suppressed in the process of seismic data processing. In the process of ghost wave suppression, undulating sea surface is a factor that can not be ignored. However, the current methods for suppressing ghost waves by single component towing cable are based on the assumption of flat sea surface, which leads to inaccurate estimation of the parameters of ghost wave operator (reflection coefficient of sea surface, delay time of ghost wave), which makes the suppression of ghost waves incomplete. When unnecessary noise is introduced into the deconvolution result, the energy of the notch point can not be recovered well. In order to solve the above problems, the mechanism of ghost wave is studied in this paper. Then the principle and applicable conditions of conventional ghost wave suppression methods in frequency-time domain, frequency-wavenumber domain and Radon domain are introduced, and the influence of the surface of undulating sea on the suppression effect of ghost waves is analyzed. Finally, the adaptive suppression method in frequency domain and the ghost wave suppression method in Radon region in the background of undulating sea surface are proposed to achieve the accurate suppression of ghost wave, which provides technical support for the suppression of ghost wave in seismic data on the sea. Based on the frequency domain adaptive ghost suppression method based on the maximum kurtosis of signal, the kurtosis coefficient is defined to evaluate the quality of the deghost result, and the delay time of the ghost wave is searched by setting the search range. The optimal reflection coefficient and ghost delay time can be estimated adaptively and accurately, and the purpose of adaptive suppression of ghost wave can be achieved. This method can suppress ghost wave effectively in the background of flat sea surface or undulating sea surface, so that the energy at the notch point can be restored and the band width of seismic section can be widened. On the basis of sea surface imaging, the ghost wave suppression method in Lato domain is used to obtain the upward wave field at the sea surface by solving the minimum linear eastward path, and the upstream wave field from the forward and reverse extending sea surface to the geophone. The up-going wave field at the sea surface is obtained by using the least square inversion, and the least square imaging condition is used to image the sea surface, and then the actual sinking depth of the geophone is corrected to eliminate the influence of the undulating sea surface. The suppression of ghost waves under the background of undulating sea surface is realized. Methods the influence of undulating sea surface on ghost wave was considered to improve the incomplete suppression of ghost wave on the assumption of flat sea surface. The numerical simulation data and the actual towed cable data at sea show that the method can suppress ghost waves better and widen the seismic record frequency band to the greatest extent.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P631.4
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