School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds LS1 9JT, UK.
J Contam Hydrol. 2013 Apr;147:96-111. doi: 10.1016/j.jconhyd.2013.02.003. Epub 2013 Feb 22.
A multi-borehole pumping and tracer test in fractured chalk is revisited and reinterpreted in the light of fractional flow. Pumping test data analyzed using a fractional flow model gives sub-spherical flow dimensions of 2.2-2.4 which are interpreted as due to the partially penetrating nature of the pumped borehole. The fractional flow model offers greater versatility than classical methods for interpreting pumping tests in fractured aquifers but its use has been hampered because the hydraulic parameters derived are hard to interpret. A method is developed to convert apparent transmissivity and storativity (L(4-n)/T and S(2-n)) to conventional transmissivity and storativity (L2/T and dimensionless) for the case where flow dimension, 2<n<3. These parameters may then be used in further applications, facilitating application of the fractional flow model. In the case illustrated, improved fits to drawdown data are obtained and the resultant transmissivities and storativities are found to be lower by 30% and an order of magnitude respectively, than estimates from classical methods. The revised hydraulic parameters are used in a reinterpretation of a tracer test using an analytical dual porosity model of solute transport incorporating matrix diffusion and modified for fractional flow. Model results show smaller fracture apertures, spacings and dispersivities than those when 2D flow is assumed. The pumping and tracer test results and modeling presented illustrate the importance of recognizing the potential fractional nature of flow generated by partially penetrating boreholes in fractured aquifers in estimating aquifer properties and interpreting tracer breakthrough curves.
重新考察了多井抽水和示踪剂测试在裂缝白垩中的应用，并结合分数流动进行了重新解释。使用分数流动模型分析抽水试验数据得出的亚球形流动尺寸为 2.2-2.4，这被解释为由于抽水井的部分穿透性质。分数流动模型为解释裂缝含水层中的抽水试验提供了比传统方法更大的通用性，但由于难以解释得出的水力参数，其应用受到了阻碍。本文开发了一种方法，用于将表观渗透率和储容率（L(4-n)/T 和 S(2-n)）转换为常规渗透率和储容率（L2/T 和无量纲），适用于流动尺寸为 2<n<3 的情况。这些参数可以用于进一步的应用，便于分数流动模型的应用。在所示的情况下，获得了对下降数据更好的拟合，并且发现所得的渗透率和储容率比传统方法的估计值低 30%和一个数量级。修正后的水力参数用于使用分析双重孔隙度模型重新解释示踪剂测试，该模型结合了基质扩散并针对分数流动进行了修正。模型结果表明，与假设 2D 流动时相比，裂缝开度、间距和分散度更小。提出的抽水和示踪剂测试结果和建模说明了认识到在估计含水层性质和解释示踪剂突破曲线时，由部分穿透的钻孔在裂缝含水层中产生的潜在分数流动性质的重要性。
