Natural and anthropogenic fractured aquifers and reservoirs are dual porosity matrix-fracture systems, where the fracture network provides highly–conductive flow pathways and the low–permeability matrix stores most of the fluid. The coupling between flow and mechanical deformation in fractured media is often modeled using the classical theory of dual-porosity poroelasticity (DPP), based on Barenblatt's hypothesis of pressure equilibrium inside the rock matrix blocks. Equilibrium can be expected if the matrix blocks are small and the matrix diffusion time is comparable to the flow time scales along the fractures. In practice, matrix blocks may be large enough so that diffusion time scales are long, and the equilibrium hypothesis breaks down. Here, we study nonequilibrium effects in coupled flow and deformation in fractured media. We compare analytical predictions and modeling results of coupled flow and deformation in heterogeneous fractured porous media. The theoretical analysis is a nonequilibrium, dual-porosity model. We use this theory to (a) Reveal the limitations of classical DPP formulations. (b) Obtain the scalings for drainage and displacement to be expected for coupled flow and deformation in highly heterogeneous, fractured media. (c) Identify what behavior to expect in fractured aquifers and reservoirs regarding flow and deformation. We observe strong tailing in fluid fluxes and land subsidence that cannot be captured by the classical DPP approach or a single porosity effective medium approach. We show that theoretical predictions from the multirate DPP model and high-fidelity models agree, even for highly heterogeneous matrix-fracture systems, and reproduce the observed nonequilibrium effects.

中文翻译：

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压裂介质中双孔隙孔隙弹性的多速率传质方法

天然和人为裂缝含水层和储层是双孔隙度基质-裂缝系统，其中裂缝网络提供高导流通道，低渗透性基质储存大部分流体。基于 Barenblatt 的岩石基质块内压力平衡假设，通常使用双孔隙率多孔弹性 (DPP) 的经典理论对裂缝介质中的流动和机械变形之间的耦合进行建模。如果基质块很小并且基质扩散时间与沿裂缝的流动时间尺度相当，则可以预期达到平衡。在实践中，矩阵块可能足够大，以至于扩散时间尺度很长，均衡假设失效。在这里，我们研究了断裂介质中耦合流动和变形的非平衡效应。我们比较了非均质裂隙多孔介质中耦合流动和变形的分析预测和建模结果。理论分析是非平衡的双孔隙度模型。我们使用这个理论来 (a) 揭示经典 DPP 公式的局限性。(b) 获得高度非均质、断裂介质中耦合流动和变形的预期排水和位移比例。(c) 确定裂缝含水层和水库中关于流动和变形的预期行为。我们观察到经典 DPP 方法或单一孔隙度有效介质方法无法捕获的流体通量和地面沉降的强烈拖尾。我们表明，多速率 DPP 模型和高保真模型的理论预测是一致的，即使对于高度异质的基质断裂系统，