TTI各向异性逆时偏移技术及应用

摘要

地下介质广泛存在各向异性,传统各向同性地震偏移成像技术往往会导致成像精度不高甚至深度偏差问题,宽方位采集技术和高精度逆时偏移(RTM)成像技术的应用更是突显了各向异性的影响.从弱各向异性弹性波波动方程出发,首先采用拟声波近似得到VTI各向异性伪声波控制方程,然后引入交叉导数项进行坐标旋转得到TTI各向异性伪声波控制方程,再由高阶有限差分方法得到TTI-RTM偏移算子,最后采用波场校正消除横波分量影响,提高各向异性偏移算子的精度.模型试算和实际资料处理结果表明,该技术在处理各向异性介质地震资料时具有更高的精度,是高精度地震成像理想的技术手段.%Anisotropy is widespread in the subsurface formation medium.The conventional isotropic seismic migration imaging technique often leads to low imaging accuracy and even depth error.The application of wide azimuth seismic acquisition technique and high precision RTM imaging technology have highlighted the influence of anisotropy.In this paper we begin with the weakly anisotropic elastic wave equation,First,the VTI anisotropic pseudo acoustic wave control equation is obtained by quasi acoustic approximation.Then,the cross derivative term is introduced to coordinate rotation to get the TTI anisotropic pseudo acoustic wave control equation.Next,the TTI-RTM migration operator is obtained by high order finite difference.Finally,the influence of the S-wave component is eliminated by wave field correction to improve the accuracy of the anisotropic migration operator.The model test and field data processing results show that,the technique is more beneficial to the anisotropic medium with higher precision and it's an ideal technique for high precision seismic imaging.