Organic‐rich shales contain large amounts of oil and gas and are anisotropic because of fine‐scale layering and the partial alignment of organic matter and anisotropic clay minerals with the bedding. An example is the Wolfcamp Shale in the Permian Basin. Elastic anisotropy needs to be accounted for in the characterization of such formations using seismic data and plays a role in hydraulic fracturing and in the evaluation of stress changes and geomechanical effects resulting from production. Using extensive well log data acquired in the Midland Basin, the eastern sub‐basin of the Permian Basin, we estimate and compare the elastic anisotropy in the Middle and Upper Wolfcamp Shale by combining data from a vertical pilot well with two lateral wells, one (6SM) drilled in the Middle Wolfcamp and one (6SU) drilled in the Upper Wolfcamp. The data used were acquired at the Hydraulic Fracture Test Site 1, located in the eastern part of the Midland Basin. Thomsen's anisotropy parameter calculated from the fast and slow shear sonic is higher on average for the 6SM lateral than for 6SU, consistent with there being less carbonate content in 6SM than in 6SU. However, the anisotropy parameter in some regions with higher carbonate content in well 6SU is higher than in well 6SM. This may indicate the influence of natural fractures. The primary set of steeply dipping fractures observed in the lateral wells at Hydraulic Fracture Test Site 1 acts to increase if the ratio of the normal‐to‐shear fracture compliance is less than about 0.5. Sub‐horizontal fractures may also increase and could affect the vertical extent of hydraulic fractures. Relations between elastic moduli C33 and C55 in the Upper and Lower Wolfcamp in a vertical pilot well allow C33 to be predicted in a lateral well using measurements of C55 in that well. Comparison of Thomsen's anisotropy parameters and , with calculated from the measured values of C55 and C66 and calculated from the measured values of C11 and predicted values of C33, show that is mostly greater than .

中文翻译：

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米德兰盆地中、上Wolfcamp页岩弹性各向异性对比

富含有机质页岩含有大量石油和天然气，并且由于精细分层以及有机质和各向异性粘土矿物与层理的部分排列而具有各向异性。二叠纪盆地的沃尔夫坎普页岩就是一个例子。在使用地震数据表征此类地层时需要考虑弹性各向异性，并且弹性各向异性在水力压裂以及评估生产产生的应力变化和地质力学效应中发挥作用。利用在二叠纪盆地东部次盆地米德兰盆地获得的大量测井数据，我们通过结合来自垂直导向井和两个侧向井的数据来估计和比较中沃尔夫坎普页岩和上沃尔夫坎普页岩的弹性各向异性，其中一个（ 6SM）在中沃尔夫坎普（Middle Wolfcamp）进行钻探，1 架（6SU）在上沃尔夫坎普（Upper Wolfcamp）进行钻探。使用的数据是在位于米德兰盆地东部的 1 号水力压裂试验场获得的。根据快剪切声波和慢剪切声波计算得出的汤姆森各向异性参数，6SM 横向平均高于 6SU，这与 6SM 中碳酸盐含量低于 6SU 一致。但6SU井部分碳酸盐含量较高的区域各向异性参数高于6SM井。这可能表明天然裂缝的影响。如果正剪裂缝柔量之比小于约 0.5，则在水力压裂试验点 1 的侧井中观察到的第一组陡倾裂缝会增加。次水平裂缝也可能增加，并可能影响水力裂缝的垂直范围。弹性模量之间的关系C33和C55在上沃尔夫坎普和下沃尔夫坎普的垂直先导井中允许C33使用测量值在侧井中进行预测C55在那口井里。汤姆森各向异性参数 和 的比较，根据测量值计算C55和C66并根据测量值计算C11和预测值C33，表明大多数情况下大于 。