Quantitative estimation of rock-physics properties is an important part of reservoir characterization. Most current seismic workflows in this field are based on amplitude variation with offset. Building on recent work on high-resolution multiparameter inversion for reservoir characterization, we have constructed a rock-physics parameterized elastic full-waveform inversion (EFWI) scheme. Within a suitably formed multiparameter EFWI, in this case a 2D frequency-domain isotropic-elastic full-waveform inversion with a truncated Gauss-Newton optimization, any rock-physics model with a well-defined mapping between its parameters and seismic velocity/density can be examined. We select a three-parameter porosity, clay content, and water saturation (PCS) parameterization, and we link them to elastic properties using three representative rock-physics models: the Han empirical model, the Voigt-Reuss-Hill boundary model, and the Kuster and Toksöz inclusion model. Numerical examples suggest that conditioning issues, which make a sequential inversion (in which velocities and density are first determined through EFWI, followed by PCS parameters) unstable, are avoided in this direct approach. Significant variability in inversion fidelity is visible from one rock-physics model to another. However, the response of the inversion to the range of possible numerical optimization and frequency selections, as well as acquisition geometries, varies widely. Water saturation tends to be the most difficult property to recover in all situations examined. This can be explained with radiation pattern analysis, in which very low relative scattering amplitudes from saturation perturbations are observed. An investigation performed with a Bayesian approach illustrates that the introduction of prior information may increase the inversion sensitivity to water saturation.

中文翻译：

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使用弹性全波形反演直接更新岩石物理属性

岩石物理性质的定量估计是储层表征的重要部分。该领域中当前大多数地震工作流程都是基于带偏移的振幅变化。在高分辨率多参数反演用于储层表征的最新工作的基础上，我们构建了岩石物理参数化弹性全波形反演（EFWI）方案。在适当形成的多参数EFWI中，在这种情况下，采用截断的Gauss-Newton优化进行二维频域各向同性弹性全波形反演，可以在参数和地震速度/密度之间建立明确映射的任何岩石物理学模型都可以被检查。我们选择一个三参数的孔隙率，粘土含量和水饱和度（PCS）参数化，然后使用三种代表性的岩石物理模型将它们与弹性特性关联起来：Han经验模型，Voigt-Reuss-Hill边界模型以及Kuster和Toksöz包含模型。数值示例表明，在这种直接方法中避免了使连续演算（其中速度和密度首先通过EFWI确定，然后是PCS参数确定）变得不稳定的条件问题。从一个岩石物理模型到另一个岩石物理模型，可以看到反演保真度的显着变化。但是，反演对可能的数值优化和频率选择范围以及采集几何形状的响应差异很大。在所有检查的情况下，水饱和度往往是最难恢复的特性。这可以用辐射图分析来解释，其中观察到来自饱和扰动的非常低的相对散射幅度。