Elastic impedance variation with angle inversion for elastic parameters
Elastic impedance variation with angle inversion for elastic parameters
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DOI：
10.1088/1742-2132/9/3/247
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发表时间：
2012-06
影响因子：
1.4
通讯作者：
Z. Zong;Xingyao Yin;Guo-chen Wu
中科院分区：
文献类型：
--
作者：
Z. Zong;Xingyao Yin;Guo-chen Wu
弹性波阻抗（EI）和振幅随炮检距或角度变化（AVO/AVA）反演是利用反射地震资料估计地下弹性参数的两种主要方法。常规EI反演作为一种叠前叠后联合反演方法，因其子波提取效率高、稳定性好等优点在工业界得到了广泛应用，但常规EI反演提取弹性参数的鲁棒性仍存在争议。三项AVO反演的鲁棒性有了很大的提高，但对于每个炮检距或入射角提取合理的空间变化子波仍然是一个挑战。本文在贝叶斯框架下提出了一种鲁棒的三参数估计方法--弹性波阻抗随角度变化（伊娃）反演方法，该方法可以直接从EI估计弹性参数。该方法假设待反演参数服从柯西分布，并基于对数域上的归一化EI方程实现，从而减小了反演的非线性。在目标函数中引入协方差矩阵对测井曲线的参数和约束进行去相关处理，增强了伊娃反演的鲁棒性。模型试验表明，所提出的伊娃反演方法，使一个非常光滑的初始模型和适度的高斯噪声估计合理的弹性参数。真实的资料实例表明，反演的纵、横波速度和密度与测井解释结果吻合较好，说明了该方法的有效性。
Elastic impedance (EI) and amplitude variation with offset or angle (AVO/AVA) inversion are two cardinal methods to estimate elastic parameters underground with reflection seismic data. Conventional EI inversion as a kind of pre-stack and post-stack joint inversion method has been widely applied in the industry because of its high efficiency and high stability of wavelet extraction; however, the robustness of extracting elastic parameters in conventional EI inversion is still controversial. The robustness of three-term AVO inversion has improved a lot; however, it is still challenging to extract reasonable space variant wavelets for each offset or incident angle. In this paper, a robust three-parameter estimation method, named elastic impedance variation with angle (EVA) inversion, is proposed in the Bayesian framework, which can estimate elastic parameters directly from EI. This method supposes that the parameters to be inverted are Cauchy distributed and it is implemented based on a normalized EI equation in a logarithmic domain which can reduce the nonlinearity of inversion. Application of a covariance matrix to decorrelate the parameters and constraint of well log curves introduced in an objective function enhances the robustness of EVA inversion. A model test shows that the proposed EVA inversion method enables one to estimate reasonable elastic parameters with extremely smooth initial models and moderate Gaussian noise. A real data example shows that the inverted P-wave velocity, S-wave velocity and density are identical to well log interpretation results, which shows the validity of the proposed method.