The significance of fracture roughness for hydraulic characterization of sparsely fractured (crystalline) rock using flow logs under steady‐state pumping conditions is investigated by numerical simulations in three‐dimensional fracture networks. A new solver for simulating flow in three‐dimensional discrete fracture networks is implemented using a hybrid finite volume and finite element method. The analysis is focused on different scales of heterogeneity in three‐dimensions: the network scale heterogeneity, the fracture‐to‐fracture scale heterogeneity, and the individual fracture scale heterogeneity (fracture roughness). The results show that the individual fracture scale heterogeneity due to fracture roughness is potentially an additional source of uncertainty for hydraulic tests in fractured rocks using flow logs. Specifically, it enhances the variation in measured flowrates and inferred transmissivity in addition to the network scale heterogeneity and the fracture‐to‐fracture scale heterogeneity. However, the individual fracture scale heterogeneity has relatively small impact on the inferred transmissivity distributions compared to the fracture‐to‐fracture scale heterogeneity. Moreover, fracture roughness and fracture‐to‐fracture heterogeneity have limited influence on the median values of the inferred transmissivity such that the median transmissivity is mostly reliable when inferred from flow logs. Comparison between the inferred and underlying input transmissivity distributions shows that interpreting hydraulic tests in crystalline rock using flow logs and the Thiem equation may underestimate the variation range of the underlying transmissivity. The results are helpful for understanding the uncertainty in hydraulic characterization of sparsely fractured rocks using flow logs that are relevant for various geo‐engineering and water resources applications.

中文翻译：

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稳态抽运下利用流动测井推论结晶岩中的透射率：多尺度非均质性的影响

在三维裂缝网络中，通过数值模拟研究了裂缝粗糙度对稳态泵送条件下使用流测井的稀疏裂缝（晶体）岩石水力表征的重要性。使用混合有限体积和有限元方法，实现了一种新的求解器，用于在三维离散裂缝网络中模拟流动。分析着眼于三个维度上的不同尺度的非均质性：网络尺度的非均质性，裂缝至断裂尺度的非均质性以及单个裂缝尺度的非均质性（裂缝粗糙度）。结果表明，由于裂缝粗糙度造成的单个裂缝尺度异质性可能是使用流动测井对裂缝岩石进行水力试验的另一不确定性来源。特别，除了网络规模的非均质性和裂缝到裂缝规模的非均质性，它还增加了测得流量的变化和推断的透射率。但是，与裂缝到裂缝尺度的非均质性相比，单个裂缝尺度的非均质性对推断的透射率分布的影响相对较小。此外，裂缝的粗糙度和裂缝到裂缝的非均质性对推断的透射率的中值的影响有限，因此，从流动测井推算得出的中值透射率最可靠。推断的输入透射率分布与基础输入透射率分布之间的比较表明，使用流量测井和Thiem方程解释晶体岩石中的水力测试可能会低估基础透射率的变化范围。