基于各向异性反演的河道砂岩薄储层预测方法研究及应用

    Research and application of a prediction method for thin channel sandstone reservoirs based on anisotropic inversion

    • 摘要: 河道砂岩具有一定的方位各向异性特征,考虑各向异性反演能实现对河道砂体更精细的预测,但由于待反演参数过多,直接反演结果往往不稳定。本文首先基于测井资料确定河道砂体的各向异性特征,对比不同AVO近似方程发现Rűger三项式方程相对更加精确;针对各向异性反演的不稳定性问题,基于宽方位高密度地震资料,提出了两步法反演实现策略,首先分扇区反演得到不同扇区的梯度项,然后使用稳健的线性反演算法求解各向异性参数和弹性参数相对值;最后开展机器学习高分辨率融合反演得到弹性参数绝对值,并结合岩石物理特征分析,预测了河道砂体薄储层的分布,其结果与测井资料和地质认识相吻合,说明该方法对类似地区河道砂岩薄储层预测和各向异性反演具有借鉴意义。

       

      Abstract: Channel sandstones exhibit distinct azimuthal anisotropy, enabling anisotropic inversion to more accurately characterize and predict channel sand bodies. However, direct inversion frequently yields unstable results due to an excessive number of parameters to be inverted. In this study, the anisotropic characteristics of channel sand bodies were first determined based on logging data. Comparison of various amplitude variation with offset (AVO) approximate equations demonstrates that the three-term Rűger equation outperformed others. To address the instability of anisotropic inversion, this study proposed a two-step inversion strategy based on wide-azimuth, high-density seismic data. Specifically, the gradient terms of various azimuth sectors were first derived through sector-specific inversion. The relative values of elastic parameters were then calculated using robust linear inversion algorithms. Finally, the absolute values of elastic parameters were determined through machine learning-based high-resolution fusion. The distribution of thin channel sandstone reservoirs predicted by combining petrophysical analysis agreed well with log data and geological understanding. The results of this study can serve as a guide for the prediction and anisotropic inversion of thin channel sandstone reservoirs in similar areas.

       

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