Hydrodynamic analysis of radial collector well ageing at Belgrade well field

124463 582 M20 М21а The origin and effect of hydraulic resistances on the rate of ageing of radial collector wells are identified through numerical hydrodynamic analysis. The research includes hydrodynamic modeling of one such well with new laterals at Belgrade well field. The performance of the laterals is aggravated by rapid ageing. The change in the hydraulic parameters of the laterals during the first decade of operation is analyzed through simulations of the groundwater regime with realistically specified geometries and hydraulics of the laterals. Contrary to previous investigations, two genetically different types of clogging were identified. The initial hydraulic resistances are a result of colmation due to the gravel pack grain-sizes and screen slot sizes being mismatched with the sand and gravel sediments of the aquifer deposited at the depth of the laterals. Colmation affects the hydraulic performance of the laterals. Well ageing is aggravated by incrustation, caused by high iron concentrations in the captured groundwater. The research highlights a strong correlation between increasing resistances at the laterals, on account of iron precipitation, and groundwater entrance velocities at the laterals. It is possible to differentiate between colmation and incrustation and accurately define the increase in resistances at the laterals by specifying known thicknesses of the near-lateral screen zones and quantifying hydraulic conductivities of those zones. MODFLOW–USG code and Connected Linear Network Process package are recommended for simulating laterals and defining real rather than hydraulically equivalent characteristics of the laterals, as an approach to hydrodynamic investigations relating to radial collector wells.