Two species of microcracks
Two species of microcracks
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DOI：
10.1007/s11770-014-0415-7
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发表时间：
2014-04
影响因子：
0.7
通讯作者：
C. Stuart;Yuan Gao
中科院分区：
文献类型：
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作者：
C. Stuart;Yuan Gao
我们确定了两种相互关联但独立的微裂纹，它们具有不同的起源和不同的分布。其中一种是在与声发射相关的实验室应力单元中发现的经典高应力微裂纹，因为微裂纹随着应力的增加而打开。另一种是紧密排列的应力排列的流体饱和微裂纹的低应力分布，剪切波分裂（SWS）观测表明，这种分布几乎遍及上地壳、下地壳和地幔最上层 400 km 的所有原位岩石。在某些情况下，这两组微裂纹可能相互关联且相似（因此称为“物种”），但它们通常具有根本不同的属性、不同的分布和不同的含义。碳氢化合物勘探和采收的重要性在于碳氢化合物储层中的 SWS 可以监测裂缝排列和流体流动的首选方向。对于地震学来说，SWS 的重要性在于，小地震上方的 SWS 可以监测应力增加对普遍的低应力微裂纹分布的影响，从而可以识别地震前（可能是遥远的地震）的应力积累，并预测即将发生的地震应力。
We identify two interrelated but independent species of microcracks with different origins and different distributions. One species is the classic high-stress microcracks identified in laboratory stress-cells associated with acoustic emissions as microcracks open with increasing stress. The other species is the low-stress distributions of closely-spaced stress-aligned fluid-saturated microcracks that observations of shear-wave splitting (SWS) demonstrate pervade almost all in situ rocks in the upper crust, the lower crust, and the uppermost 400 km of the mantle. On some occasions these two sets of microcracks may be interrelated and similar (hence ‘species’) but they typically have fundamentally-different properties, different distributions, and different implications. The importance for hydrocarbon exploration and recovery is that SWS in hydrocarbon reservoirs monitors crack alignments and preferred directions of fluid-flow. The importance for earthquake seismology is that SWS above small earthquakes monitors the effects of increasing stress on the pervasive low-stress microcrack distributions so that stress-accumulation before, possibly distant, earthquakes can be recognised and impending earthquakes stress-forecast.