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    基于构造应力约束的裂缝参数反演方法及应用

    Fracture parameter inversion with tectonic stress constraints and its application

    • 摘要: 高角度裂缝的存在导致地下介质呈现方位各向异性,反射系数随方位角的变化可以用方位傅里叶级数分析来表征。构造应力控制着裂缝的形成和分布,提出一种基于构造应力差异约束的反射振幅随方位角变化(AVAz)裂缝参数反演方法。首先,利用叠后地震数据提取曲率属性,基于最大正曲率和最小负曲率构建归一化构造应力差异因子;其次,对数据进行傅里叶级数分析,计算其二阶傅里叶相位角和零阶傅里叶系数;最后,引入构造应力差异因子作为约束条件,构建以二阶傅里叶系数为求解目标的反演目标函数,实现裂缝密度反演。塔里木盆地奥陶系碳酸盐岩缝洞型储层受构造应力控制,基于构造应力差异因子约束的AVAz裂缝参数反演方法在塔河油田奥陶系碳酸盐岩缝洞型储层中的应用结果显示,裂缝密度和裂缝走向反演结果与测井数据相吻合,验证了该反演方法的有效性。实际应用结果表明,该方法能有效提高裂缝预测精度,为裂缝型储层预测提供了一种新的技术支撑。

       

      Abstract: The existence of high-angle fractures leads to an anisotropic underground medium, and the reflection coefficient varies with the azimuth, which can be characterized using the azimuthal Fourier series analysis. The formation and distribution of fractures are controlled by tectonic stress. An amplitude variation with azimuth (AVAz) fracture parameter inversion method was proposed based on different tectonic stress constraints. Firstly, the curvature attribute was extracted using the post-stack seismic data, and the normalized differential tectonic stress factor was constructed based on the maximum positive curvature and the minimum negative curvature. Secondly, Fourier series analysis was performed on the data, and its second-order Fourier phase angle and zero-order Fourier coefficient were calculated. Finally, a differential tectonic stress factor was introduced as a constraint condition, and an inversion objective function based on the second-order Fourier coefficients was constructed as the solution target, thereby achieving the inversion of fracture density. The Ordovician carbonate rock fracture-cavity reservoirs in the Tarim Basin are controlled by tectonic stress. The application results of the AVAz fracture parameter inversion method based on the constraint of differential tectonic stress factor in the Ordovician carbonate rock fracture-cavity reservoir of Tahe Oilfield show that the inversion results of fracture density and fracture orientation are consistent with the logging data, verifying the effectiveness of this inversion method. The application demonstrates that the proposed method can effectively improve the prediction accuracy of the fractures and thus provides a new technical support for fractured reservoir prediction.

       

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