A constant rate salt tracer injection method to quantify pumped flows in long-screened or open borehole wells

David L. Poulsen, Peter G. Cook, Craig T. Simmons, James M. McCallum, Saskia L. Noorduijn, Shawan Dogramaci

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)408-420
Number of pages13
JournalJournal of Hydrology
Volume574
DOIs
Publication statusPublished - 1 Jul 2019

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