针对现有地层压裂效果评估的声波测井方法通常用压裂缝密度来评价压裂缝体积,其结果往往不能准确反映实际产能的问题,研究了压裂缝的动态渗透性能及其与测井声场的相互作用,在实验观测的压裂缝分形现象基础上建立复杂压裂缝网的渗透率模型,将该模型的动态渗流响应与描述渗透性地层声波传播的Biot-Rosenbaum理论相结合,得到斯通利波速度频散特征与压裂缝渗透性能的关系,进而提出压裂缝渗透性能的评价方法。研究结果表明：复杂压裂缝导致的斯通利波速度频散特征可以与平板缝模型等效,前提是将压裂缝模型的平均渗透率等效于平板缝的渗透率;压裂缝开启的高渗条件（缝宽为10~100 μm,渗透率为数百平方微米）和压裂缝闭合渗透率降低条件（缝宽为1~10 μm,渗透率为数十平方微米）下,斯通利波速度频散特征具有明显差异。现场应用结果表明,提出的渗透性能定量评价模型可以评价压裂缝的渗透率和压裂贯通系数。
The existing acoustic logging methods for evaluating the hydraulic fracturing effectiveness usually use the fracture density to evaluate the fracture volume, and the results often cannot accurately reflect the actual productivity. This paper studies the dynamic fluid flow through hydraulic fractures and its effect on borehole acoustic waves. Firstly, based on the fractal characteristics of fractures observed in hydraulic fracturing experiments, a permeability model of complex fracture network is established. Combining the dynamic fluid flow response of the model with the Biot-Rosenbaum theory that describes the acoustic wave propagation in permeable formations, the influence of hydraulic fractures on the velocity dispersion of borehole Stoneley-wave is then calculated and analyzed, whereby a novel hydraulic fracture fluid transport property evaluation method is proposed. The results show that the Stoneley-wave velocity dispersion characteristics caused by complex fractures can be equivalent to those of the plane fracture model, provided that the average permeability of the complex fracture model is equal to the permeability of the plane fracture. In addition, for fractures under high-permeability (fracture width 10~100 μm, permeability ~100 μm2) and reduced permeability (1~10 μm, ~10 μm2, as in fracture closure) conditions, the Stoneley-wave velocity dispersion characteristics are significantly different. The field application shows that this fluid transport property evaluation method is practical to assess the permeability and the connectivity of hydraulic fractures.
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