Horizontal Directional Drilling: An Overview

By Gerald Gilbert 3 years ago

HDD, or horizontal directional drilling, is a trenchless method of installing pipelines and conduits beneath obstacles such as roads,  rivers, coastal shorelines/landfalls, railways, and other areas where open-cut excavations are not practical or desired for constructability, social, economic,or environmental reasons.

This method is used in projects other drilling methods, such as trenching or excavating, is not ideal. It is often used in various soil conditions and jobs such as landscaping, road building, and river crossings.

Applications of HDD

 

HDD is used to install infrastructure such as the following:

  • telecommunications cables
  • power cable conduits
  • sewer lines
  • water lines
  • gas and oil lines

It is also used for crossing inland waterways, coastal shorelines, congested areas, roads and areas that are environmentally sensitive.

What Are The Advantages Of The Hdd Method?

 

HDD is a preferred method of drilling for gas and oil reservoirs due to the following benefits:

  • Much reduced impact on the natural environment
  • Little to no disruption to surface traffic
  • Less disturbance to local communities
  • Minimised risk of damaging existing subsurface utilities
  • Minimised risk of damaging existing structures
  • No access pit required
  • For shore crossings – avoid damaging existing seawalls/revetments or breakwaters
  • Greater depth of cover offering better protection to the pipelines and conduits being installed
  • Shorter completion times
  • More cost-effective method of construction

Stages of HDD

The process of horizontal directional drilling usually comes in four stages.

Stage 1: Drilling the Pilot Hole

A horizontal pilot hole is drilled, then a predetermined design path is followed beneath and across the barrier. In a housing right behind the directional drilling cutting head, an electronic transmitter is installed.

A signal is sent from the transmitter to the surface, which the receiver reads and relays to the drill rig operator. The driller can then steer the bore path in any desired direction using the communicated information.

Stage 2: Pre-Reaming

The pilot hole is expanded in this phase to ensure that product lines can be installed safely. To remove debris and expand the hole, the reamer is pulled back and rotated as drilling fluid is pumped into the cut.

Additives are utilised to keep the borehole clean and stable, as well as to prevent clogs from forming.

Stage 3: Pullback Operations

Pullback is the third stage of the horizontal directional drilling method. The conduit can be dragged through the bored hole after it has been enlarged. The pipeline is prefabricated at the drill rig’s opposite end of the bore.

A reamer is hooked to the drill string, and then a pulling head and swivel are used to connect it to the product. The swivel allows the reamer to rotate without causing the product to rotate. The directional drilling rig next starts the pullback process, which involves rotating and tugging the drill string while also circulating drilling fluids.

The reamer is pulled back until the drill rig exits the bore path and the pipeline is installed.

Stage 4: Installation of Conduits

An aircraft cable is fitted into the horizontally bored conduit before it is pulled into position, whether it is to transport electricity lines, fibre optic cable, or any other product. The product is pulled into position within the pipe using the directional drill rig once the pipe has been installed.

Pressure testing is carried out at the end of the horizontal directional drilling process to confirm the pipe’s integrity.

Takeaway

HDD has opened floodgates for commercial entities and homeowners in need of more underground utility installations ranging from water, sewer, and electricity to gas and telecommunications. With horizontal directional drilling, utilities may be installed almost anywhere at a low cost and with no environmental impacts.