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Estimates of Individual Fracture Compliances Along Boreholes From Full‐Waveform Sonic Log Data
Journal of Geophysical Research: Solid Earth ( IF 3.9 ) Pub Date : 2021-04-27 , DOI: 10.1029/2021jb022015
Nicolás D. Barbosa 1, 2 , Andrew Greenwood 3 , Eva Caspari 3 , Nathan Dutler 4 , Klaus Holliger 5
Affiliation  

An important seismic attenuation mechanism in fractured environments is related to energy conversion into reflected and transmitted waves at fracture interfaces. Using full‐waveform sonic (FWS) log data, we show that it is possible to quantify transmission losses across a set of fractures from time delays and amplitude differences of the critically refracted P‐wave as compared to intact sections along the borehole. In the presence of fractures, the transmission coefficient associated with a given fracture is obtained by combining information on transmission losses from multiple receivers and source positions into a linear system of equations for all fractures intersecting the borehole. Fracture compliance is computed from the inferred transmission coefficient based on a linear slip model. For validation, we use synthetic FWS log data obtained from numerical simulations of wave propagation in a water‐filled borehole surrounded by low‐permeability rocks with discrete fractures. The methodology is then applied to field data acquired along boreholes penetrating multiple fractures in a granodioritic host rock. We show that our estimations of mechanical compliance are consistent with previously reported values, which were estimated for individual fractures intersecting one of the boreholes with a related method valid only for isolated single fractures. Comparison between our estimates of fracture compliance and transmissivity profiles from previous hydraulic characterizations of the fractures suggests that the proposed method may also allow to locate the most permeable fractures along a borehole, which, in turn, opens the perspective of enhancing the design and effectiveness of subsequent hydraulic testing and fracturing experiments.

中文翻译:

从全波形声波测井资料估算井眼各个裂缝的顺应性

裂缝环境中重要的地震衰减机制与能量转换成裂缝界面处的反射波和透射波有关。使用全波形声波(FWS)测井数据,我们表明可以通过与沿井眼完整部分相比的临界折射P波的时间延迟和幅度差异来量化一组裂缝中的传输损失。在存在裂缝的情况下,通过将来自多个接收器和震源位置的有关传输损耗的信息合并到与井眼相交的所有裂缝的线性方程组中,可以得到与给定裂缝相关的传输系数。基于线性滑动模型,从推断的透射系数计算出裂缝顺应性。为了验证,我们使用合成的FWS测井数据,该数据是通过在充满离散裂缝的低渗透率岩石包围的充水钻孔中波传播的数值模拟中获得的。然后将该方法应用于沿钻孔获得的现场数据,该钻孔贯穿花岗二叠纪主岩中的多个裂缝。我们表明,我们对机械顺应性的估计与先前报道的值一致,该值是使用仅对孤立的单个裂缝有效的相关方法对与其中一个井眼相交的单个裂缝进行估算的。我们根据先前裂缝的水力特征对裂缝顺应性和透射率剖面的估计值之间的比较表明,所提出的方法还可以允许沿着井眼定位最易渗透的裂缝,进而,
更新日期:2021-05-11
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