Understanding and predicting fracture propagation and subsequent fluid flow characteristics is critical to geoenergy technologies that engineer and/or utilize favorable geological conditions to store or extract fluids from the subsurface. Fracture permeability decreases nonlinearly with increasing normal stress, but the relationship between shear displacement and fracture permeability is less well understood. We utilize the new Geo‐Reservoir Experimental Analogue Technology (GREAT cell), which can apply polyaxial stress states and realistic reservoir temperatures and pressures to cylindrical samples and has the unique capability to alter both the magnitude and orientation of the radial stress field by increments of 11.25° during an experiment. We load synthetic analogue materials and real rock samples to stress conditions representative of 500–1,000 m depth, investigate the hydraulic stimulation process, and then conduct flow experiments while changing the fluid pressure and the orientation of the intermediate and minimum principal stresses. High‐resolution circumferential strain measurements combined with fluid pressure data indicate fracture propagation can be both stable (no fluid pressure drop) and unstable (fluid pressure drop). The induced fractures exhibit both opening and shear displacements during their creation and/or during fluid flow with changing radial stress states. Flow tests during radial stress field rotation reveal that fracture normal effective stress has first‐order control on fracture permeability but increasing fracture offset can lead to elevated permeabilities at maximum shear stress. The results have implications for our conceptual understanding of fracture propagation as well as fluid flow and deformation around fractures.

中文翻译：

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多轴应力条件下水力压裂和渗透率应力敏感性试验研究

对于设计和/或利用有利的地质条件从地下存储或提取流体的地能技术而言，了解和预测裂缝的扩展以及随后的流体流动特性至关重要。断裂渗透率随法向应力的增加而非线性降低，但对剪切位移与断裂渗透率之间的关系知之甚少。我们利用新摹EO- [R eservoir ê xperimental一个nalogue ŧ技术（GREAT单元），可以将多轴应力状态以及实际的储层温度和压力应用于圆柱状样品，并且具有在实验过程中以11.25°的增量改变径向应力场的大小和方向的独特功能。我们将合成的模拟材料和真实的岩石样品加载到代表500–1,000 m深度的应力条件下，研究水力增产过程，然后进行流量实验，同时改变流体压力以及中，最小主应力的方向。高分辨率周向应变测量与流体压力数据相结合，表明裂缝扩展既稳定（无流体压降）又不稳定（流体压降）。诱发的裂缝在其产生期间和/或在流体流动期间具有变化的径向应力状态，同时呈现出开裂位移和剪切位移。径向应力场旋转过程中的流动测试表明，裂缝法向有效应力具有对裂缝渗透率的一级控制，但是增加的裂缝偏移量会导致最大剪切应力时渗透率升高。这些结果对我们对裂缝扩展以及裂缝周围的流体流动和变形的概念理解具有启示意义。