Durable wells with built-in downstream of the filter regeneration systems

Summary

The results of the studies of the durability of 224 unserviceable wells of 11 underground water intakes of Minsk city are presented. It is shown that the average service lifetime of the wells of typical design is 18–22 years, and the main causes of their outage are sanding and residual colmatage that cannot be removed by traditional repair works within the filters. A new design of a ground water well equipped with a system of downstream of the filter regeneration consisting of 4–5 polyethylene injection tubes (piezometers) is presented. The tubes have perforations opposite the well filter and are lead out onto the wellhead, installed in the hole clearance on the external boundary of the gravel package. Process flow schemes of chemical and chemical free well washing are suggested. It is shown that the symmetrical arrangement of the tubes provides for the radial directional washing flow in the gravel package at simultaneous operation of an airlift or a pump installed in the filter column. The technology of well construction is considered. The results of field testing the system of downstream of the filter regeneration of a new well in the mode of hydrodynamic washing drill mud and sludge out of the gravel package are presented. The suggested design of a water well with a gravel filter is specified by improved repairability, simplicity and can be recommended for underground water abstraction from soft water bearing rock.

Key words

water well , gravel filter , downstream of the filter regeneration , injection tube , near filter zone

On the evaluation of the life cycle of the wells operating at the existing water intakes

Summary

Life cycle or useful life expectancy of fixed assets including water abstraction wells is regulated by RF Government Decree No. 1 of 2002. For water abstraction wells the life cycle is 15–20 years. Besides, the requirements to the life cycle in the environmental management system are formulated in the system of RF state standards authentical to ISO 14000. On the basis of the experience of operating underground water intake facilities is shown that reaching the design operating life is possible only on the condition of complying with the requirements to the selection of well filters and gravel packages for water abstraction mode that minimize the hydraulic losses in the near-filter zones. The guidelines for meeting these requirements have been formulated. At the stage of hydrogeological survey of the underground water resources assessment is suggested to make predictions of the water corrosiveness and the ability to release clogging compounds and biological colmatage.

Key words

water well , environmental management , near filter zone , life cycle , useful life expectancy , hydraulic losses , colmatage