摘要
基于弹性波动理论的多波多分量高斯束偏移具有计算效率高和成像准确等优点.但是目前此方法没有考虑实际地下介质的黏弹性对地震波传播的影响,从而无法补偿能量衰减和校正相位畸变,这使得该方法对一些含高黏弹性地层的成像效果不佳.针对衰减区域的成像问题,本文提出一种黏弹性衰减补偿高斯束偏移方法,该方法以多波多分量矢量波场弹性高斯束偏移方法为基础,在偏移过程中沿射线路径通过引入品质因子Q来考虑黏弹性影响并进行衰减补偿.该方法能够在偏移过程中实现PP波和PS波的自动分离及分别成像.同时,本文给出了在矢量波场偏移过程中提取角度域共成像点道集的方法,以便用于成像质量控制,并为后续速度和黏弹性参数反演提供所需的数据.本文利用2D层状模型和洼陷模型进行了方法测试,其成像结果验证了本文所提出的黏弹性衰减补偿高斯束偏移方法的可行性和有效性.
Elastic-wave equation based multicomponent Gaussian beam migration is a desirable method for its efficiency and accuracy.However,it is not applicable for attenuating media in which anelasticity of the subsurface will cause amplitude loss and phase distortion of seismic waves.Meanwhile seismic attenuation will lead to poor illumination and misplacement of reflectors in a migration image.To increase the resolution of seismic migration images,it makes sense to compensate for such attenuation effect.To process multicomponent seismic records in a viscoelastic medium correctly,we propose a vector-based Gaussian beam migration method with attenuation compensation.In this approach,viscoelasticity is taken into consideration by introducing the quality factor(Q).Attenuation is compensated along seismic rays.We correct the travel time with Qand extend the Gaussian beam migration from elastic media imaging to viscoelastic attenuation compensationimaging.Multimode and multicomponent waves are automatically decomposed into PP and PS waves during the migration without prior separation.In order to monitor imaging quality,angledomain common image gathers are acquired during the vector-based migration,which can be utilized for migration velocity analysis and amplitude-variation-with-angle(AVA)inversion.Numerical experiments demonstrate that this method is feasible and efficient.
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