The effective monitoring of hydraulic fracturing in unconventional oil and gas production requires tools to quantify elastic property variations even in the absence of microseismic activity. To track the subtle time-lapse variations in reservoir properties during such activities, monitoring techniques with high repeatability and high resolution, spatially and temporally, are required. Distributed acoustic sensing (DAS) is a rapidly maturing fiber-optic technology for low-cost, permanent, high density, in-well monitoring. Surface orbital vibrators (SOVs) are inexpensive fixed rotary seismic sources that offer the opportunity to frequently interrogate the subsurface with energies comparable to vibroseis sources. We have evaluated a field vertical seismic profile test, conducted in the Eagle Ford play, pairing an SOV source recorded by DAS behind casing in a deviated well to better evaluate the potential of the technology set for unconventional reservoir monitoring. We determine the data processing workflow for reservoir monitoring using the SOV-DAS system. We analyze the data characteristics of the SOV-DAS system, including the signal-to-noise ratio characteristics and source repeatability. High-quality P- and S-wave reflections, as well as mode conversions, are visible in the vertical section. In addition, clear P-P reflections are also observable along the horizontal well sections. Time shifts with a mean value of 10 μs between different data sets demonstrate the high repeatability for the semipermanent SOV source, which is crucial for time-lapse analysis. We also apply reflection imaging on P and S to reveal reflection depths. In a first-of-its-kind deployment, we implemented a rotating SOV with a slewing bearing and discuss the possibility to optimize S-wave construction along the horizontal well with specific SOV orientation directions. Our preliminary results indicate that the combination of repeatable surface sources such as SOVs with DAS has significant potential for providing a low-cost approach for high-resolution seismic monitoring of unconventional reservoirs.

中文翻译：

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测试永久轨道表面源和分布式声学传感以监测非常规油​​藏：Eagle Ford页岩的初步结果

在非常规油气生产中对水力压裂进行有效监控需要即使没有微地震活动也能量化弹性特性变化的工具。为了在这样的活动过程中跟踪储层性质的细微时移变化，需要在空间和时间上具有高重复性和高分辨率的监测技术。分布式声学传感（DAS）是一种快速成熟的光纤技术，用于低成本，永久性，高密度的井内监测。地表轨道振动器（SOV）是廉价的固定旋转地震源，它提供了用与振动源相当的能量频繁地探查地下的机会。我们评估了在Eagle Ford游戏中进行的现场垂直地震剖面测试，在偏井中将DAS记录的SOV源在套管后配对，以更好地评估该技术组用于非常规油藏监测的潜力。我们确定使用SOV-DAS系统进行储层监测的数据处理工作流程。我们分析了SOV-DAS系统的数据特征，包括信噪比特征和源可重复性。在垂直部分可以看到高质量的P波和S波反射以及模式转换。此外，沿水平井段也可观察到清晰的PP反射。不同数据集之间的平均值为10μs的时移证明了半永久SOV源具有很高的可重复性，这对于延时分析至关重要。我们还对P和S应用反射成像以揭示反射深度。在首例部署中，我们实现了带有回转轴承的旋转式SOV，并讨论了优化SOV定向方向沿水平井的S波构造的可能性。我们的初步结果表明，可重复使用的地表资源（如SOV和DAS）的结合具有巨大的潜力，可为非常规水库的高分辨率地震监测提供低成本的方法。