Horizontal drilling pipes installment is performed with the help of a horizontal drilling machine (direct drilling called “mole”). Therefore the footprint on the environment and infrastructure, such as buildings, roads, pavements, etc. are minimum. The pipes are to be installed in accordance with the customer desire and project. The process of pipeline installment with guided horizontal drilling goes through the following technological stages:

  • Design / Preliminary investigation and assessment of the existing subterranean pipes’ condition and terrestrial conditions.
  • Choice of horizontal drilling equipment.
  • Pilot Bore: The pilot bore is steered from a designated entry point with a small diameter, along a predetermined path, to a designated end point. The horizontal drilling is performed from a drill head with the help of a drilling fluid under pressure. The control is facilitated by the asymmetrical shape of the drill head combined with a spatial progressive and rotary motion and orientation of the drilling head. The position of the head is controlled by an electronic system, consisting of a transmitter, located in the drill head, and a receiver, located on the surface..
  • Enlarging (reaming) of Drilling: Once the drill head reaches the end point, it is disassembled and the so called back reamer is attached instead. The drilling machine withdraws the reamer with a progressive-rotary motion and enlarges the tunnel diameter. Bentonite additive is applied, which withdraws soil particles and stabilizes the drilling tunnel. The pilot bore subsequently may be reamed to a larger diameter to accommodate the desired size of the installed pipe.
  • Pipes assembly and pipeline installations: After reaching the required tunnel diameter, a system to catch and withdraw the pipe is assembled to the reamer. The pipe is withdrawn into the tunnel afterwards. The drilling fluid (consisting of fine soil particles, bentonite and water solution) is effective in building a filter cake that lines the borehole walls and prevents loss of drilling fluid during drilling. Bentonite-based drilling mud supports the borehole wall well. Furthermore, it has relatively high viscosity and density, and effectively removes cuttings from the borehole.


This highly productive horizontal drilling method, requiring only entry and designated end point with minimum dimensions, results in short operation terms and a decreasing trend in expenditure. Therefore, these are the paramount advantages of horizontal directional drilling technology without digging. Horizontal directional drilling length, called “mole”, can reach from several dozens to 1,500 m.