Effects of ageing on the hydraulics of water wells and the influence of non-Darcy flow

Well ageing is mostly caused by mechanical and biogeochemical clogging processes, which affect the gravel pack, screen slots and casing. Clogging deposits increase head losses due to a constriction of the hydraulically effective area. For this study, clogging is mimicked by systematically reducing t...

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Bibliographic Details
Published in:Hydrogeology journal 2018-06, Vol.26 (4), p.1285-1294
Main Authors: Houben, Georg J., Wachenhausen, Julia, Guevara Morel, Carlos R.
Format: Article
Language:English
Subjects:
Ageing
Aging
Aquatic Pollution
Biogeochemistry
Darcy-weisbach equation
Earth and Environmental Science
Earth Sciences
Effective porosity
Flow velocity
Fluid dynamics
Fluid flow
Geology
Geophysics/Geodesy
Gravel
Groundwater
Groundwater flow
Hydraulic conductivity
Hydraulics
Hydrogeology
Hydrology/Water Resources
Mathematical models
Obstructions
Orifices
Porosity
Technical Note
Turbulent flow
Waste Water Technology
Water Management
Water Pollution Control
Water Quality/Water Pollution
Water wells
Well yield
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Summary:Well ageing is mostly caused by mechanical and biogeochemical clogging processes, which affect the gravel pack, screen slots and casing. Clogging deposits increase head losses due to a constriction of the hydraulically effective area. For this study, clogging is mimicked by systematically reducing the gravel pack porosity, the screen open area and the nominal inner casing diameter. Groundwater flow velocity strongly increases close to the well, inducing inertial and turbulent flow components. Therefore, gravel pack head losses were calculated using the Forchheimer-Engelund equation, in conjunction with the Kozeny-Carman equation, which relates gravel pack porosity and hydraulic conductivity. Screen losses were assessed using the Orifice equation and turbulent casing losses with the Darcy-Weisbach equation. For the settings chosen here, a dramatic increase of head losses occurs when the clogging has reduced the effective porosity in the gravel pack by ~65%, the open area of the screen by ≥98%, and the casing diameter by ~50%. Since the latter two conditions are rarely reached in actual wells, the clogging of the gravel pack is the decisive parameter that controls well ageing. Regular monitoring of the well yield is therefore needed, since processes in the gravel pack are difficult to track directly. Unlike the deposits on the casing and in the screen slots, obstructions in the gravel pack are much more difficult to remove.
ISSN:1431-2174
1435-0157
DOI:10.1007/s10040-018-1775-5