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How does horizontal directional drilling work?

Updated: Oct 23, 2023

Horizontal Directional Drilling
How does horizontal directional drilling work?

Horizontal directional drilling (HDD) is a trenchless method used to install underground utilities, pipelines, and conduits without the need for open-cut trenches. It involves drilling a controlled path underground, following a predetermined trajectory. Here's an overview of how horizontal directional drilling works:

  1. Planning and Surveying: Before the drilling process begins, engineers and surveyors carefully plan the drilling path. They consider factors such as the distance to be drilled, the depth of the utility or pipeline, geological conditions, and any environmental considerations. Surveys and subsurface investigations are conducted to ensure a clear understanding of the subsurface conditions.

  2. Surface Entry Point: The HDD process starts with the creation of a surface entry point. This is typically where the drill rig is set up and where the pilot hole drilling will commence.

  3. Pilot Hole Drilling: A small-diameter pilot hole is drilled from the surface entry point. The pilot hole serves as a guide for the subsequent drilling phases. The drill head, which may be equipped with a mud motor, is used to advance through the ground along the planned path.

  4. Real-time Monitoring: During the pilot hole drilling, various sensors and navigation tools are used to monitor the position and orientation of the drill head in real-time. These tools may include gyroscopic tools, magnetic sensors, inclinometers, and accelerometers.

  5. Steering and Correction: Based on the real-time data and monitoring, the drilling operator makes adjustments to the drilling path as needed. The operator can correct the direction of the drill head to ensure it stays on course and follows the planned path accurately.

  6. Reaming: Once the pilot hole is drilled, it is typically smaller in diameter than the desired utility or pipeline. The pilot hole is then enlarged through a process called reaming. Reaming involves the use of progressively larger cutting tools or reamers to create a larger hole.

  7. Utility or Pipeline Installation: After reaming, the utility or pipeline is pulled through the drilled hole using a pullback operation. Tension is applied to the utility as it is drawn through the bore, and the drill head and reaming tools are removed in the process.

  8. Exit Point and Restoration: The utility emerges at the exit point, and final connections are made. Any remaining drilling mud is cleaned, and the borehole is backfilled and restored to its original condition.

Horizontal directional drilling offers several advantages, including reduced surface disruption, environmental friendliness, versatility, and enhanced safety. It is widely used in various industries, including oil and gas, telecommunications, water supply, and power distribution, for the installation of underground infrastructure in a more efficient and less invasive manner.

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