A newly drilled well is not automatically ready for operation. Sand must be removed, and the filter zone must be properly developed before stable and efficient extraction is possible. In practice, however, wells are frequently considered ‘finished’ after swabbing, airlifting, shock pumping or surge plugging without verifying whether they have reached their actual hydraulic capacity. The PDF highlights that several widely used methods no longer reflect state-of-the-art practice, as the physical mechanisms behind deposit formation and removal are often underestimated.
Investigations described in the paper show that, particularly when drilling fluids (e.g. bentonite) contribute to persistent clogging, wells in the same geological formation can behave very differently in terms of yield and drawdown. Cross-sectional observations of dismantled wells revealed filter-cake layers that remained largely intact after conventional development, leaving only limited pathways for water to pass through. The document also states that swabbing and surge plugging may remove only 40–60% of the filter cake. In contrast, the ETSCHEL JET Master® is presented as a method that can remove filter cake comprehensively when applied correctly.
From a fluid mechanics perspective, the HPI-Process® uses high water pressure to generate pressure impulses that treat the gravel pack all the way through to the borehole wall and even into the aquifer. A key feature is the use of a double-rotation unit with four nozzles on two planes, which creates negative pressure that displaces the water horizon into the gravel ring space, supporting the ‘remarkable sand removal effect’ referenced by the DVGW (W55/99). The paper notes that single-plane systems would only affect a limited vertical zone of about 25 cm, whereas bi-rotational units can achieve an effective vertical treatment range of roughly 40–60 cm. Parameters such as nozzle distance, speed and pressure can be adjusted.
In a documented field case (Test 1, southern Germany), a well that had previously undergone conventional development exhibited a specific yield of 5.4 l/s per metre drawdown. Following HPI-Process® development using the JET Master®, the specific yield increased to 36 l/s per metre drawdown — a reported performance increase of 6.7 times, attributed to the removal of water-resistant deposits (e.g. clay/tone transported along the borehole wall). Additional trials with KIWA Water Research in the Netherlands saw the well developed until it was technically sand-free, with drilling additives (xanthan) removed. Subsequent chemical treatment with hydrogen peroxide did not improve performance further, indicating that the mechanical HPI development had already achieved the intended hydraulic result.
The concluding sections of the paper emphasise that not all rotating nozzles or “standard jetting” approaches deliver comparable results because the HPI-Process® relies on specific hydrodynamic effects and correct configuration. Container-based testing further supports this: fine sand fractions were reported as having been removed up to 12 cm behind the filter screen, while the natural aquifer gradation remained beyond that zone. For operators and project owners, this highlights the importance of evaluating well development based on measurable outcomes such as a sand-free condition, drawdown behaviour and specific yield, rather than solely on the completion of a traditional procedure.
For more detailed technical information and figures, please click the PDF button.
If you would like expert support with well development or rehabilitation using the HPI-Process®, Etschel Brunnenservice GmbH is available to advise you — contact us with your enquiries.
