Imaging fractures and sedimentary fabrics using shear wave splitting measurements made on passive seismic data
Imaging fractures and sedimentary fabrics using shear wave splitting measurements made on passive seismic data
复制标题
使用被动地震数据的剪切波分裂测量对裂缝和沉积构造进行成像
DOI：
10.1111/j.1365-246x.2009.04347.x
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发表时间：
2009
影响因子：
2.8
通讯作者：
A. Wüstefeld
中科院分区：
文献类型：
--
作者：
J. Verdon;J. Kendall;A. Wüstefeld
利用地震各向异性检测对齐裂缝的能力为更好地开发油气藏提供了有价值的工具。也许识别各向异性的最直接方法是观察横波分裂。然而，剪切波与地下结构的相互作用往往是复杂的。虽然油气储层中的裂缝通常是近垂直的，但在井下接收器上记录的来自储层中或附近的微震事件的剪切波不太可能垂直传播。因此，解释在这种波上进行的分裂测量是一个重要的问题。在这里，我们开发了一种方法来模拟非垂直传播的剪切波的地下结构的影响。岩石物理学理论用于模拟沉积组构以及裂缝的影响，使我们能够使用剪切波分裂测量来反演对齐的裂缝。我们使用合成的例子来证明它是如何可能提前评估如何以及分裂测量将图像结构，以及这是如何高度依赖于射线覆盖的可用范围。最后，我们展示了在水力压裂增产过程中收集的被动地震数据集的反演技术。尽管一个不利的源-接收器的几何形状，一个对齐的裂缝集的走向被准确地识别。
SUMMARY The ability to detect aligned fractures using seismic anisotropy provides a valuable tool for exploiting hydrocarbon reservoirs better. Perhaps the most direct way of identifying anisotropy is by observing shear wave splitting. However, the interaction of shear waves with subsurface structure is often complicated. Although fractures in hydrocarbon reservoirs are usually subvertical, shear waves recorded on downhole receivers from microseismic events in or near the reservoir are not likely to have travelled vertically. As such, interpreting splitting measurements made on such waves is a non-trivial problem. Here we develop an approach to model the effects of subsurface structure on non-vertically propagating shear waves. Rock physics theory is used to model the effects of sedimentary fabrics as well as fractures, allowing us to use shear wave splitting measurements to invert for aligned fractures. We use synthetic examples to demonstrate how it is possible to assess in advance how well splitting measurements will image structures, and how this is highly dependent on the available range of ray coverage. Finally, we demonstrate the inversion technique on a passive seismic data set collected during hydraulic fracture stimulation. Despite an unfavourable source–receiver geometry, the strike of an aligned fracture set is accurately identified.