基于VTI介质理论的P波速度分析和动校正

P-WAVE NONHYPERBOLIC MOVEOUT ANALYSIS IN VTI MEDIA

地震各向异性在沉积岩石中是广泛存在的,针对各向异性资料进行处理时,最大的困难就是如何从地面地震资料中恢复出速度场并估算地下介质参数。传统地震资料处理通常假设地下介质是各向同性的,这将大量浪费大排列处的地震信息,而且它提供的叠加速度及层速度通常无法满足钻前压力预测的需要。针对最常见的层状VTI介质,利用P波走时资料,根据非双曲时差理论,通过速度谱分析方法获得水平界面双曲时差速度和地层各向异性参数,并在此基础上对资料进行动校叠加。将该方法应用于理论模型和西部某探区实际资料后,可以看出当目标层埋深较大时,为改善叠加剖面质量,提高资料的分辨率和信噪比,更好的追踪层位,必须考虑各向异性对P波走时的影响。

The sedimentary rocks may produce significant seismic anisotropy,the main difficulty in extending seismic processing to anisotropic medium is reconstruct the anisotropic velocity fields and obtain effective anisotropic parameter from surface reflection data.Conventional seismic exploration is based on the assumption of isotropy,it will be waste lots of usefull informations of long offset,and the precision of stack velocity and interval velocity provided can't meet the need of predicting the pre-drilling press.This paper only consider the transve-rsely isotropic media with a vertical symmetry axis,after scanned nonhyperbolic moveout of P-wave reflections form horizontal interfaces in VTI medium we obtain two accurate parameters:the zero-dip NMO velocity,and an anisotropy parameter η that is special combination of Thomsen's anisotropy parameters.After we achieved used this algorithm in synthetic model and two real data in some areas,west China,it can be realize that application of anisotropic processing to P-wave data is very important.Because taking anisotropy into account yields better images,as well as better understanding of the subsurface structure.