Over the past few years, intensive collaborations between drinking water companies, KWR Watercycle Research Institute and various market players has led to great progress in the development of Horizontal Directional Drilled Wells (HDDWs), that is, horizontal well screens installed by means of horizontal directional drilling (HDD).
The use of biodegradable drilling fluids permits, for example, the creation of an in-situ gravel pack in fine-sand aquifers. This latter development makes HDD suitable for a broad range of applications, such as sustainable drainage and geo-technical stabilisation of earthworks. However, the biodegradable drilling fluids result, in drinking water applications, in undesirable bacterial growth. To further expand the market potential of HDDWs, this project develops techniques to enable the installation of microbiologically reliable HDDWs in fine-sand aquifers.
The project involves preliminary research and a pilot to install an HDDW in the dunes of Dunea. The preliminary research aims to determine whether the use of HDDWs in the intended pilot locations does in fact offer sufficient benefits compared to established techniques, such as auger drilling. Field and lab experiments – including small-scale test drilling – are conducted to remove any bottlenecks.
This research project should lead to a full-scale HDDW pilot that produces good quality water in sufficient quantity. The insights and experience provided by the project regarding the implementability, proper drilling techniques, design requirements and development techniques are reported.
Various test drilling programmes were carried out at Dunea and test wells installed using HDD techniques, and experiments were done using different drill bits and fluids. The results clearly established which drilling techniques result in the highest abstraction capacity and produce bacteriologically reliable water. Analysis is still ongoing into whether the drilling fluids are in fact sufficiently removed from the wells, for the purpose of safeguarding the long-term capacity of the wells. This will provide the basis for a go/no-go decision on proceeding with a full-scale pilot.