摘要
偏移成像是VSP数据处理中的一个重要环节,常规的VSP成像方法通常利用VSP-CDP转换或Kirchhoff偏移,均存在保幅性差及成像精度低等问题,而波动方程叠前深度偏移被认为是对地下复杂构造进行成像的精确偏移方法.任意广角波动方程作为一种高精度的空间域单程波波动方程,同时由于只含有二阶偏导数项,易于数值实现,与其他单程波波动方程相比,具有更大的成像倾角,因此是偏移成像的有力工具之一.本文将AWWE推广应用到VSP数据成像中,实现了VSP时空域高角度单程波方程偏移.首先从三维标量任意广角波动方程出发,推导了完全匹配层吸收边界条件,在基本不增加计算量的前提下有效地压制了边界反射成像噪音,同时利用非线性反演算法优选参考速度来提高平方根算子的近似程度,从而提高高角度地层的成像精度.模型数值模拟实验验证了该方法的有效性,同时表明该方法在陡倾角构造情况下能取得很好的成像效果.最后对某地区实际观测的VSP资料进行了偏移成像,并与地面地震偏移结果进行了对比,显示出VSP波动方程偏移在成像分辨率上的优势.
Migration is a key step in VSP data processing,VSP imaging commonly uses VSP-CDP conversion or Kirchhoff migration which has issues of poor amplitude conservation and low imaging precision,while wave equation prestack depth migration is an effective method to image complex structures.Arbitrarily wide-angle wave equation（AWWE）is a space domain one-way wave equation（OWWE）with a high accuracy and easy numerical implementation because of only including two-order partial derivative term.Compared with other OWWEs,AWWE is capable of imaging steeper dips,which enables it to be one of powerful migration tools.In this paper,we extended AWWE to VSP imaging and realized VSP migration based on high angle one-way wave equation in time-space domain.And the perfectly matched layer（PML）absorbing boundary condition was derived to provide a good approach to suppress artifacts arising at truncation boundaries at a price of limited additional computation cost.Meanwhile,we optimized reference velocities usingnonlinear algorithm to enhance the approximation degree of square root operator and improved imaging precision of high-dip layers.Model tests proved the effectivity of the method and showed that it can obtain good imaging result in the case of steep-dip structures.The method was also applied to field VSP data,the comparison of VSP migration result and surface seismic section showed that VSP migration provides a higher resolution image.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2016年第9期3459-3469,共11页
Chinese Journal of Geophysics
基金
国家科技重大专项(2011ZX05024)资助
关键词
任意广角波动方程
VSP偏移
PML
Arbitrarily wide-angle wave equation
VSP migration
Perfectly matched layer
作者简介
范廷恩，男，1972年生，高级工程师，主要从事地震反演、地震属性分析及油藏精细描述等方面的研究．E-mail：fante@cnooc．com．cn
通讯作者：马淑芳，女，1984年生，博士，主要从事井中地震及井地联合高分辨率处理等方面的研究．E—mail：mashf2@cnooc．com．cn
