A novel approach of unconventional reservoir stress evaluation is proposed to enhance the accuracy of fracture development prediction. Differential horizontal stress ratio can reflect the stress characteristic of fractured reservoir. To calculate the differential horizontal stress ratio more intuitionistic and simpler, we re‐derive its formula with Poisson's ratio and fracture density. Meanwhile, a new azimuthal PP‐wave amplitude versus offset equation based on Poisson's ratio and fracture density was derived for inverting above elastic parameters directly. Therefore, two steps are needed to realize stress evaluation. First, amplitude‐versus‐azimuthal angle inversion in the Bayesian framework in constraint of prior information such as well log data or rock physics information is executed for elastic and fracture parameters using pre‐stack angle gathers of different azimuth angles. The second procedure is to estimate differential horizontal stress ratio with Poisson's ratio and fracture density. Finally, a real data set is studied to test the new approach and the result demonstrated that the estimated differential horizontal stress ratio can reflect the stress property and it agrees with geological law and the new drilled well interpretation. Therefore, we can conclude that the combination of newly derived differential horizontal stress ratio and azimuthal PP‐wave amplitude versus offset equation in this study provides an available method for estimating the differential horizontal stress ratio of unconventional reservoirs, and the new approach can offer reliable geophysical information for stress evaluation.

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非常规油藏方位振幅反偏移反演的应力预测与评估方法

提出了一种非常规储层应力评价的新方法，以提高裂缝发育预测的准确性。水平差应力比可以反映裂缝性储层的应力特征。为了更直观，更简单地计算差分水平应力比，我们用泊松比和裂缝密度重新推导其公式。同时，推导了一个新的基于泊松比和裂缝密度的PP波振幅与偏移的关系方程，可以直接对上述弹性参数进行反演。因此，需要两个步骤来实现应力评估。第一，在贝叶斯框架中，在先验信息（例如测井数据或岩石物理信息）的约束下，使用叠前不同角度的叠角角度弹性和裂缝参数对振幅和方位角进行反演。第二个步骤是用泊松比和断裂密度估算水平应力比。最后，研究了一个真实的数据集以测试该新方法，结果表明，估计的水平差分应力比可以反映应力特性，并且符合地质定律和新的钻井解释。因此，