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Thomsen各向异性参数的求取对于正确的时深转换和深度域偏移成像处理至关重要。相比其它各向异性参数估算方法,从VSP资料中更容易获取准确的各向异性参数用于地面地震偏移成像。本文分析研究了利用Walkaway VSP资料估算VTI介质Thomsen各向异性参数的方法,该方法基于VTI介质近偏移距动校正公式利用Walkaway VSP近偏移距初至信息求取各向异性参数δ;基于各向异性介质纵波速度Thomsen近似公式采用射线追踪时差扫描方法求取各向异性参数ε。数值模型正演表明利用该方法估算的各向异性参数误差较小。利用塔里木盆地8个方位的Walkaway VSP实际资料求取了该区深度域Thomsen各向异性参数ε和δ值,同时结合地面三维地震资料建立了较为准确的各向异性深度一速度模型用于叠前深度偏移成像,进一步提高了碳酸盐岩储层的成像精度,减小了目标地质体的深度误差。
Thomsen anisotropy parameters are crucial for correct time-depth conversion and depth domain offset imaging. Compared with other anisotropic parameter estimation methods, accurate anisotropy parameters are more easily obtained from VSP data for ground seismic migration imaging. In this paper, the method of estimating Thomsen’s anisotropy parameters of VTI media by using Walkaway VSP data is studied. The method is based on the dynamic correction formula of near-offset VTI media and the first-arrival information of Walkaway VSP is used to calculate the anisotropy parameter δ. Thomsen approximation of longitudinal wave velocity in anisotropic media The anisotropy parameter ε is obtained by ray tracing time-difference scanning. The numerical model forward shows that the anisotropy parameters estimated by this method have less error. The Thomsen anisotropy parameter ε and δ in the depth domain of the area were obtained by using the actual Walkaway VSP data of 8 azimuths in the Tarim Basin. At the same time, a more accurate anisotropic depth-velocity model was established for prestack Depth migration imaging further improves the imaging accuracy of carbonate reservoirs and reduces the depth error of target geologic bodies.