Inferring rock fracture evolution during reservoir stimulation from seismic anisotropy
Inferring rock fracture evolution during reservoir stimulation from seismic anisotropy
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DOI：
10.1190/geo2011-0057.1
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发表时间：
2011-11
期刊：
影响因子：
3.3
通讯作者：
A. Wuestefeld;J. Verdon;J. Kendall;J. Rutledge;H. Clarke;J. Wookey
中科院分区：
文献类型：
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作者：
A. Wuestefeld;J. Verdon;J. Kendall;J. Rutledge;H. Clarke;J. Wookey
我们已经分析了地震各向异性使用剪切wavessplitting测量过程中记录在一个致密气藏在迦太基，得克萨斯州东部的水力压裂实验中的微震事件。微震事件记录在两个井下三分量传感器阵列上，其几何形状为各向异性分析提供了良好的射线覆盖。来自888个定位事件的16，633个地震记录产生了1545个井约束剪切波分裂测量。对来自该数据集的子集的分裂的手动分析揭示了压裂期间分裂的时间变化。反演使用完整的数据集允许识别裂缝走向和密度，这是观察到在压裂过程中发生变化。岩体中恢复的裂缝走向平行于区域钻孔崩落的方向，但倾斜于由微震事件映射的水力裂缝走廊。我们将此与预先存在的裂缝的雁列断裂有关。剪切波分裂的幅度在每个泵送阶段显示出明显的时间增加，表明裂缝和裂隙在裂缝走廊周围的晕中产生，从而增加了岩体的整体渗透性。我们的研究结果表明，剪切波分裂分析可以提供一个有用的工具，监测空间和时间变化的裂缝网络所产生的水力刺激。
We have analyzed seismic anisotropy using shear-wavesplitting measurements made on microseismic events recorded during a hydraulic fracture experiment in a tight gas reservoir in Carthage, east Texas. Microseismic events were recorded on two downhole arrays of three-component sensors, the geometry of which provided good ray coverage for anisotropy analysis. A total of 16,633 seismograms from 888 located events yielded 1545 well-constrained shear-wave-splitting measurements. Manual analysis of splitting from a subset of this data set reveals temporal changes in splitting during fracturing. Inversion using the full data set allows the identification of fracture strike and density, which is observed to vary during fracturing. The recovered fracture strike in the rock mass is parallel to directions of regional borehole breakout, but oblique to the hydraulic fracture corridor as mapped by the microseismic event. We relate this to en-echelon fracturing of preexisting cracks. The magnitude of shear-wave splitting shows a clear temporal increase during each pumping stage, indicating the generation of cracks and fissures in a halo around the fracture corridor, which thus increase the overall permeability of the rock mass. Our results show that shear-wave-splitting analysis can provide a useful tool for monitoring spatial and temporal variations in fracture networks generated by hydraulic stimulation.