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Horizontal Directional Drilling introduction


Horizontal Directional Drilling (HDD) is a trenchless excavation method originated in the late 1960’s by merging technologies prominent in the water wells and utilities industry. HDD involves drilling along a desired pathway while simultaneously inserting a pipe into the new borehole.

The HDD process is completed in three parts, the first being the drilling of a pilot hole along the proposed centreline and the second being the enlarging of the hole with a reamer. The last step would be have the new pipe installed behind the reamer during the last pass of the reaming process.

In any HDD works, a major component of the drilling activities is the drilling fluid. In many instances and also in situations when the new pipe diameter is much larger than the pilot hole, it is vitally important that the correct amount and mixtures of drilling fluid is resourced. The use of drilling fluid helps to prevent the potential collapse of the bore path, assists in the removal of cutting material produced by the drilling process, and reduces friction during the pullback of the new pipe process.

Ensuring the correct bore hole diameter may take more than one pass or reaming before the borehole is large enough in diameter to install the proposed new pipe. The number of required reaming passes may also be affected by geographical conditions. On the final pass with the reamer, the new pipe is attached to the reamer and pulled back through the borehole from the exit point to the drill rig.