Analysis of slug-tests with high-frequency oscillations

Olivier Audouin (1) , Jacques Bodin (1)

1 HydrASA - Hydrogéologie, argiles, sols et altérations - FRE3114

Extensive slug-test experiments have been performed at the Hydrogeological Experimental Site (HES) of Poitiers in France, made up of moderately fractured limestones. All data are publicly available through the "H+" database, developed within the scope of the ERO program (French Environmental Research Observatory, http://hplus.ore.fr). Slug-test responses with high-frequency (> 0.12 Hz) oscillations have been consistently observed in wells equipped with multiple concentric casing. These oscillations are interpreted as the result of inertia-induced fluctuations of the water level in the annular space between the inner and outer casing. In certain cases, these high-frequency oscillations overlap with lower frequency (< 0.05 Hz) oscillations, which leads to complex responses that cannot be interpreted using conventional models. Slug-test data have been processed in the Fourier-frequency domain, in order to remove the high-frequency component by a signal-filtering method. The corrected signals have been interpreted with the model of (McElwee and Zenner, 1998), which accounts for the inertia of the water-column above the well screen, non-linear head losses in the well, and neglects the aquifer storage (quasi-steady-state approximation). Hydraulic conductivity values interpreted from dual-frequency slug-tests compare well to those interpreted from "standard" overdamped or underdamped slug-test responses.

Domaines: Hydrologie

Olivier Audouin, Jacques Bodin. Analysis of slug-tests with high-frequency oscillations. Journal of Hydrology, 2007, 334, pp.282-289. ⟨10.1016/j.jhydrol.2006.10.009⟩. ⟨hal-00260614⟩