In many groundwater wells, performance losses are often linked to solids restricting inflow. Yet common methods such as brushing, swabbing, shock pumping, surge plugging and standard jetting do not always achieve optimal outcomes, particularly when deeper penetration of the gravel pack and the near-well aquifer zone is required. In the Donauried area of Württemberg — one of Baden-Württemberg’s key groundwater reservoirs — these challenges are important because the system supports the regional drinking water supply and must handle seasonal demand peaks. The practical question is clear: how can development be made more effective without adding extra time and cost?
The state water supply of Baden-Württemberg operates a large inventory of wells, including older wells in the Niederstotzingen/Ulm catchment that have been in use for over 100 years (including the use of an energy-saving siphon principle). Preliminary investigations identified severe corrosion on screens and casings, prompting a rehabilitation programme favouring full reconstruction of proven but ageing assets. Within this framework, Etschel Brunnenservice supported the programme as a subcontractor for well development, using the High Pressure Impulse Process (HPI-Process®), and for final CCTV acceptance testing.
ETSCHEL’s original nozzle rotation unit (UNINOZ®) is used with the JET Master® to generate high-pressure impulses. The known hydraulic effects between opposing nozzle arms, such as underpressure and cavitation, can contribute to the separation of zones above and below nozzle pairs. The aim of the redesign was to intensify and extend these effects, enabling the nozzle rotation unit to better ‘reach’ the space between nozzle pairs and drive impulses deeper through the gravel pack into the aquifer. The resulting innovation is the MAXINOZ®, a patented nozzle rotation unit with an adjustable nozzle angle that can be matched to screen geometry to improve penetration depth.
The comparative field test was run on six adjacent wells (1814–1819) with similar geological conditions and comparable construction: V4A Johnson Type filter screens, DN 500, with a slot width of 2.0 mm and gravel packs of 5.6–8 mm. Three of the wells were treated with UNINOZ® and three with MAXINOZ®, immediately after sanitation and prior to pumping. A key complication was the extreme sizing (DN 1000 bore diameter vs. DN 500 screen), which created a very thick gravel pack layer that made effective development challenging. As shown in Table 1, the MAXINOZ® wells removed an average of around 10 times more sand and undersize particles than the UNINOZ® wells (136 litres vs. 14 litres), demonstrating substantially greater depth effectiveness.
The results imply the following for practice: less ‘partial desanding’ where MAXINOZ® is used properly.
The report concludes that for similarly sized wells, relying on the conventional UNINOZ® configuration alone is no longer effective enough; it may appear to meet termination criteria without truly desanding deeper into the aquifer. By contrast, MAXINOZ® enables deeper sand removal and facilitates the development of a more ‘natural filter’ transition at the borehole wall–aquifer interface. The findings also suggest that surge plugging (‘partial desanding’) using the pumping quantities specified in DVGW W 119 is often not cost-effective in such cases. If used, it may only be worthwhile with significantly increased pumping rates, although well hydraulics may limit what is technically feasible. Overall, MAXINOZ® is presented as an innovative improvement for developing wells in loose rock under challenging gravel-pack conditions.
For more detailed information, including the complete test setup, tables, and diagrams, please click the PDF button to access the full technical article.
Do you need support with well development or rehabilitation? Etschel Brunnenservice GmbH specialises in high-pressure impulse well development and well diagnostics. Contact us to discuss your project or site conditions.
