Pore fluid pressure effects in anisotropic rocks: Mechanisms of induced seismicity and weak faults
Pore fluid pressure effects in anisotropic rocks: Mechanisms of induced seismicity and weak faults
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各向异性岩石中的孔隙流体压力效应：诱发地震活动和弱断层的机制
DOI：
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
A. Nur
中科院分区：
文献类型：
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作者：
Qiang Chen;A. Nur
许多观测和研究表明，地壳岩石中的孔隙流体压力在变形、断裂和地震过程中起着重要作用。传统的孔隙压力效应模型通常假设各向同性的多孔岩石，并产生非偏压力效应，这似乎不足以解释与孔隙压力变化有关的各种现象，如流体提取引起的地震活动和地壳弱断层。本文推导了横向各向同性和正交各向异性岩石的各向异性有效应力定律，指出各向异性岩石中孔隙流体压力的偏置效应不仅影响岩石的有效强度，而且引起剪应力的变化。这种由孔隙压力上升或下降引起的剪应力变化可能导致断层失稳和触发地震，并为低水平剪应力的地壳弱断层的破坏提供机制。我们认为，各向异性岩石中孔隙流体压力的偏差效应在地震前兆和余震研究、油气藏表征、提高采收率和水力压裂等方面有着广泛的应用。
Many observations and studies indicate that pore fluid pressure in the crustal rocks plays an important role in deformation, faulting, and earthquake processes. Conventional models of pore pressure effects often assume isotropic porous rocks and yield the nondeviatoric pressure effects which seem insufficient to explain diverse phenomena related to pore pressure variation, such as fluid-extraction induced seismicity and crustal weak faults. We derive the anisotropic effective stress law especially for transversely-isotropic and orthotropic rocks, and propose that the deviatoric effects of pore fluid pressure in anisotropic rocks not only affect rock effective strength but also cause variation of shear stresses. Such shear stress variations induced by either pore pressure buildup or pore pressure decline may lead to faulting instability and trigger earthquakes, and provide mechanisms for the failure of crustal weak faults with low level of shear stresses. We believe that the deviatoric effects of pore fluid pressure in anisotropic rocks are of wide application in studies of earthquake precursors and aftershocks, oil and gas reservoir characterization, enhanced oil recovery, and hydraulic fracturing.