Trenchless Technology

Horizontal Directional Drilling


Overview

Horizontal Directional Drilling commonly called as HDD is a trenchless method for installing a product that serves as a conduit for liquids, gases, or as a duct pipe, cable wire line products. It is a multi – stage process consisting of site preparation and restoration, equipment setup, and drilling a pilot bore along a pre-determined path and then pulling the product back through the drilled space. When necessary, enlargement of the pilot borehole may be necessary to accommodate a product larger than the pilot bore hole size. This process is referred to as back reaming and is done at the same time the product is being pulled back through the pilot bore hole. Accomplish alignment of the bore by proper orientation of the drill bit head as it is being pushed into the ground by a hydraulic jack. Determine orientation and tracking of the drill bit by an above ground radio detection device which picks up a radio signal generated from a transmitter located within the drill bit head. Then electronically translate the radio signal into depth and alignment, in order to minimize friction and prevent collapse of the bore hole, introduce a soil stabilizing agent (drilling fluid) into the annular bore space from the trailing end of the drill bit. The rotation of the bit in the soil wetted by the drilling fluid creates slurry. The slurry acts to stabilize the surrounding soil and prevent collapse of the bore hole as well as provides lubrication. Select or design drilling fluids for the site specific soil and groundwater conditions. Confine free flowing (escaping) slurry or drilling fluids at the ground surface during pull back or drilling. Accomplish this creating sump areas or vacuum operations to prevent damage or hazardous conditions in surrounding areas. Remove all residual slurry from the surface and restore the site to preconstruction conditions.

Equipment Requirements

EQUIPMENT

The directional drilling equipment shall consist of a directional drilling rig of sufficient capacity to perform the bore and pullback the pipe, a drilling fluid mixing and delivery system of sufficient capacity to successfully complete the crossing, a guidance system to accurately guide boring operations and trained and competent personnel to operate the system. All equipment shall be in good, safe operating condition with sufficient supplies, materials and spare parts on hand to maintain the system in good working order for the duration.

DRILLING SYSTEM

  • DRILLING RIG – the directional drilling machine shall consist of a hydraulically powered system to rotate, push and pull hollow drill pipe into the ground at a variable angle while delivering a pressurized fluid mixture to a guidable drill (bore) head. The machine shall be anchored to the ground to withstand the pulling, pushing and rotating pressure required to complete crossing. The hydraulic power system shall be self-contained with sufficient pressure and volume to power drilling operations. Hydraulic system shall be free of leaks. Rigs shall have a system to monitor and record maximum pull-back pressure during pull-back operations.
  • DRILL HEAD – the drill head shall be steerable by changing it’s rotation and shall provide the necessary cutting surfaces and drilling fluid jets. We have a wide range of drill heads that best suits site soil condition.
  • MUD MOTORS (if required) – mud motors shall be of adequate power to turn the required drilling tools.
  • DRILL PIPE – shall be constructed of high quality 4130 seamless tubing, grade D or better, with threaded box and pins. Tool joints should be hardened to 32 – 36 RC.

GUIDANCE SYSTEM

The Guidance System shall be of proven type and shall be setup and operated by personnel trained and experienced with this system. The operator shall be aware of any magnetic anomalies and shall consider such influences in the operation of the guidance system if using a magnetic system.

DRILLING FLUID (MUD) SYSTEM

  • MIXING SYSTEM – a self-contained, closed, drilling fluid mixing system shall be of sufficient size to mix and deliver drilling fluid composed of bentonite clay, potable water and appropriate additives. Mixing system shall be able to molecularly shear individual bentonite particles from the dry powder to avoid clumping and ensure thorough mixing. The drilling fluid reservoir tank shall be sized for adequate storage of the mud. Mixing system shall continually agitate the drilling fluid during drilling operations.
  • DRILLING FLUIDS – drilling fluids shall be composed of clean water and an appropriate additive. Water shall from a clean source with a pH of 8.5-10 and/or as per mixing requirements of the manufacturer. Water of a lower pH or with excessive calcium shall be treated with appropriate amount of sodium carbonate or equal. The water and additives shall be mixed thoroughly and be absent of any clumps or clods. No hazardous additives may be used. Drilling fluid shall be maintained at a viscosity sufficient to suspend cuttings and maintain the integrity of bore wall. Used drilling fluid and drilling fluid spilled during drilling operations shall be contained and properly disposed of.
  • DELIVERY SYSTEM – the mud pumping system shall have a minimum capacity to supply mud in accordance with the drilling equipment pull-back rating at a constant required pressure. The delivery system shall have filters in-line to prevent solids from being pumped into the drill pipe. Proper mudflow control should be adopted so that cuttings are removed efficiently from the drill holes. Connections between the pump and drill pipe shall be relatively leak-free. A berm, minimum of 12” high, shall be maintained around drill rigs, drilling fluid mixing system, entry and exit pits and drilling fluid recycling system (if used) to prevent spills into the surrounding environment. Pumps and or vacuum truck(s) of sufficient size shall be in place to convey excess drilling fluid from containment areas to storage facilities.

OTHER EQUIPMENT

  • PIPE ROLLERS – pipe rollers, if required, shall be of sufficient size to fully support the weight of the pipe while being hydro-tested and during pull-back operations. Sufficient number of rollers shall be used to prevent excess sagging of pipe.