1. A constant rate salt tracer injection method to quantify pumped flows in long-screened or open borehole wells.
- Author
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Poulsen, David L., Cook, Peter G., Simmons, Craig T., McCallum, James M., Noorduijn, Saskia L., and Dogramaci, Shawan
- Subjects
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FREE convection , *FROUDE number , *DIMENSIONLESS numbers , *GROUNDWATER flow , *SALT - Abstract
• Measuring in-well flow regimes improves key hydrogeological data and insight. • Efficient new field method and numerical model for a single-well tracer test. • Pumped flow profile quantified by inverting tracer dilution profiles. • Steady-state approach is suited to a wide range of pumping flow rates. • Analysis of mixed convection helps assess and avoid fluid/tracer density issues. Quantifying vertical flows in long-screened or open wells is essential for their reliable use in all types of groundwater investigations. In ambient conditions, a flow profile shows the producing/receiving zones of head-driven flow, the relative vertical head gradient in the aquifer system and potential bias in chemistry samples. A flow profile while pumping can be used to quantify aquifer heterogeneity and the sampled water mixtures. This paper describes a novel approach to a single-well tracer test to quantify the flow regime in a pumped well, which is unique in its utility over a wide range of discharge rates. During constant pumping, a tracer is injected at the opposite end of the well and, as it is drawn towards the pump, the tracer is diluted in proportion to each inflow. A dilution model using the advection-dispersion equation is used to visually fit a flow profile that explains all tracer profiles (pre-injection, transient phase and steady-state). Results compare favourably to borehole EM flowmeter data, particularly if tracer density issues are correctly interpreted and head-loss in the flowmeter is avoided. A dimensionless Froude number is provided to assist both with understanding and minimising the role of free convection when planning all types of in-well tracer tests involving a density contrast. Like the flowmeter, this method is particularly suited to screened wells, where packers are ineffective. Used together or separately in existing wells, these in-well methods can provide considerable information on aquifer-well hydraulics without the cost of additional drilling. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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