Horizontal directional drilling is one of the fastest growing techniques for trench less installation of pipelines. On one hand they provide a logical alternative when cables, pipelines or small tunnels need to cross roads, railways, dikes, wetlands, rivers and other structures that have to remain intact. On the other hand HDD techniques minimize the impact of installation activities in densely populated and economical sensitive areas.
The success of a horizontal directional drilling (HDD) is largely dependent on the success of the pullback operation, when the product pipe is installed in the created borehole. The cost of damaged pipelines and the costs for additional measures during and after the pullback operation can be considerable. The creation and maintenance of the borehole during the stages of horizontal directional drilling are therefore important aspects. The interaction processes between the downhole drilling tools, the drilling fluid and the soil need to be well understood for the creation and maintenance of a horizontal directional drilling borehole. A risk analysis based on the knowledge of these processes can be useful to avoid unexpected problems during the pullback operation of the pipeline.

dr Henk M.G. Kruse, Deltares