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Recovering tracer test input functions from fluid electrical conductivity logging in fractured porous rocks
Author(s) -
Mathias S. A.,
Butler A. P.,
Peach D. W.,
Williams A. T.
Publication year - 2007
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2006wr005455
Subject(s) - tracer , aquifer , borehole , geology , porosity , well logging , diffusion , electrical resistivity and conductivity , hydraulic conductivity , breakthrough curve , soil science , mineralogy , geotechnical engineering , groundwater , geophysics , chemistry , soil water , thermodynamics , physics , electrical engineering , engineering , nuclear physics , organic chemistry , adsorption
A radially convergent tracer test was carried out in an unconfined Chalk aquifer of Berkshire, United Kingdom. Fluorescent tracers were injected into two boreholes lying 32 m (PL10A) and 54 m (PL10B) from the abstraction hole. The tracers were also mixed with an NaCl solution so that vertical distributions of tracer within the injection wells could be monitored using fluid electrical conductivity (FEC) logging. The breakthrough curve (BTC) from PL10A was unimodal and had a first arrival time of 14 min. The BTC from PL10B exhibited two distinct peaks and a first arrival time of just 4 min. The tracer test input functions were derived by numerically modeling the observed FEC logs of the injection wells. These were then convoluted with a conventional, Fickian matrix diffusion dual‐porosity model. The results suggested that the multiple peaks were due to the way in which the tracers left the injection wells and migrated into the aquifer. FEC log inversion proved to be an effective method for predicting borehole flow data obtained by flowmeters and recovering tracer test input functions for radially convergent tracer tests.