Perforation shots excite guided waves that propagate in a low-velocity unconventional shale reservoir. They have a frequency content of up to 700 Hz and are dispersive. We have analyzed horizontal crosswell perforation shots recorded by a distributed acoustic sensing (DAS) array. As guided waves propagate through a previously stimulated area, we observe a dramatic influence on the guided SH waves in the form of delayed arrival times, scattering, phase incoherency, and loss of amplitude and frequency. The leaky compressional waves undergo a gradual slowdown. Using a simple geometric analysis of the spatial locations of the distortions in the direct arrivals of the guided SH waves, we can estimate the half-lengths of the induced fractures, which range from 50% to 75% of the distance between the perforated and monitoring wells. Furthermore, we find that the propagation disturbances originate from the middle of the stimulated area. Other diffracted signals, notably from frac plugs, are clearly visible in the data. We report the first large-scale use of DAS records of guided waves. Their potential for high-resolution imaging and inversion of subsurface properties before and after hydraulic stimulation opens new possibilities for the use of seismology in optimizing production from unconventional reservoirs.

中文翻译：

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使用非常规油藏中导波的分布式声波记录记录来估算断裂特性

射孔弹激发在低速非常规页岩储层中传播的导波。它们的频率成分高达700 Hz，并且具有色散性。我们已经分析了由分布式声感测（DAS）阵列记录的水平井间射孔弹。当导波传播通过先前受激的区域时，我们以延迟到达时间，散射，相位不相干以及振幅和频率损失的形式观察到对SH导波的巨大影响。泄漏的压缩波会逐渐变慢。通过对引导的SH波直接到达时的变形的空间位置进行简单的几何分析，我们可以估算出诱导裂缝的半长，其范围为射孔与监测之间距离的50％至75％。井。此外，我们发现传播干扰源于受激区域的中部。其他衍射信号，特别是来自压裂塞的衍射信号，在数据中清晰可见。我们报告了DAS导波记录的首次大规模使用。它们在水力压裂之前和之后进行高分辨率成像和地下特性反演的潜力，为利用地震学优化非常规油藏生产开辟了新的可能性。