G360 Institute for Groundwater Research, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
G360 Institute for Groundwater Research, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
J Contam Hydrol. 2018 Jul;214:75-86. doi: 10.1016/j.jconhyd.2018.05.003. Epub 2018 May 17.
A straddle-packer system for use in boreholes in fractured rock was modified to investigate the average linear groundwater velocity (v¯) in fractures under ambient flow conditions. This packer system allows two different tests to be conducted in the same interval between packers without redeploying the system: (1) forced gradient hydraulic tests to determine the interval transmissivity (T), and (2) borehole dilution experiments to determine the groundwater flow rate (Q) across the test interval. The constant head step test method provides assurance that flow is Darcian when determining T for each interval and identifies the flow rate at the onset of non-Darcian flow. The critical Reynolds number method uses this flow rate to provide the number of hydraulically active fractures (N) in each interval, the average hydraulic aperture for the test interval and the effective bulk fracture porosity. The borehole dilution method provides Q values for the interval at the time of the test, and v¯ can be estimated from Q using the flow area derived from the hydraulic tests. The method was assessed by application to seven test intervals in a borehole 73 m deep in a densely fractured dolostone aquifer used for municipal water supply. The critical Reynolds number method identified one or two fractures in each test interval (1.1 m long), which provided v¯ values in the range of 10 to 8000 m/day. This velocity range is consistent with values reported in the literature for ambient flow in this aquifer. However, when hydraulically active fractures in each interval is identified and measured from acoustic and optical televiewer logs, the calculated v¯ values are unreasonably low as are the calculated values of the hydraulic gradient needed to provide the Q value for each tested interval. The combination of hydraulic and dilution tests in the same interval is an improved method to obtain values of groundwater velocity in fractured rock aquifers.
一种用于裂隙岩石钻孔的跨隔式封隔器系统经过改装，用于在环境流动条件下研究裂隙中的平均线性地下水速度（v¯）。该封隔器系统允许在两个封隔器之间的同一间隔内进行两种不同的测试，而无需重新部署系统：（1）强制梯度水力测试以确定间隔渗透率（T），（2）钻孔稀释实验以确定测试间隔内的地下水流速（Q）。定水头阶跃测试方法可确保在确定每个间隔的 T 时流动是达西流，并确定非达西流开始时的流速。临界雷诺数法使用该流速提供每个间隔的水力活动裂缝数量（N）、测试间隔的平均水力开度和有效整体裂缝孔隙度。钻孔稀释法可在测试时提供间隔的 Q 值，并且可以使用水力测试得出的流动面积从 Q 估算 v¯。该方法通过应用于用于市政供水的一个深 73m 的裂隙白云岩含水层中的七个测试间隔进行了评估。临界雷诺数法在每个测试间隔中确定了一个或两个裂缝（长 1.1m），其提供的 v¯ 值范围为 10 至 8000m/天。该速度范围与文献中报道的该含水层中环境流动的速度一致。然而，当从声学和光学电视测井中识别和测量每个间隔中的水力活动裂缝时，计算出的 v¯ 值异常低，并且为每个测试间隔提供 Q 值所需的水力梯度的计算值也异常低。在同一间隔内进行水力和稀释测试的组合是一种改进的方法，可以获得裂隙岩石含水层中的地下水速度值。
