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Some anomalous features of flow and solute transport arising from fracture aperture variability
Author(s) -
Moreno Luis,
Tsang ChinFu,
Tsang Yvonne,
Neretnieks Ivars
Publication year - 1990
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/wr026i010p02377
Subject(s) - tracer , fracture (geology) , flow (mathematics) , mechanics , volumetric flow rate , aperture (computer memory) , geology , materials science , soil science , geotechnical engineering , physics , acoustics , nuclear physics
Model fractures with variable apertures are generated by a statistical method, and water flow and tracer transport in these fractures are calculated. Tracer injection and collection are simulated for parallel and convergent flow fields. The impact of the use of different injection flow rates and the different locations of injection and collection points are studied. The results show that the transport time, dispersion, and the so‐called mass balance fracture aperture are very sensitive to the location of the injection point and the injection flow rate. These anomalous effects appear to be consistent with observations in several recent field experiments. The implications of the calculated results on the analysis of tracer tests are discussed. It is concluded that because of the stochastic nature of variable fracture apertures (and their permeabilities) a point tracer test in a fracture is not sufficient to characterize the properties of the fracture. Dispersivities and apertures calculated from different tracer tests in the same fracture may vary by orders of magnitude depending on the flow rate and the location of the injection. However, a line injection of tracer, averaged over a series of adjacent points, may avoid some of these problems.