March, 2008
SNGPL Project for laying 24" dia gas pipe line through HDD successfully completed.
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October, 2009
Uptil now ZUCS completed more than 65000 meters HDD work on different projects.

 
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Zaritel.com home » Horizontal Directional Drilling

Horizontal Directional Drilling

We take pride in stating that Zari Underground Construction is a fast growing company , which is geared up for undertaking “ Communication Network development Projects” too far meeting tremendous requirements in the vast field of communication . It won’t be unrealistic to say that present world is shrinking due to revolutionary expansion of communications.

We are pleased to inform you that we possess a very competent position due to our professional standing in the market. We have a well established technical infrastructure i.e Horizontal Directional Drilling Machines and locating equipments etc and are fully equipped to undertake the underground construction with HDPE and Steel pipes at any ground conditions up to 1500 meters bore length. We wish to take this opportunity to express that the rich technical culture and strong sense of responsibility inculcated into our highly skilled team, has enabled us to establish a sound ‘Implementation and Maintenance Support, system which provide a very much desired confidence to our quality conscious client base.

Zari Underground Construction completed more than 35000 meters HDD jobs at different sites of Link Direct ( Mobilink ) Optical fiber network and in other projects

 

Phone +92-51-4575223-225


 
HDD Procedure
 
Pilot Hole
 
Drilling mud
 
Pre-reaming
 
Pull-back
 
Pipe Bore Path Friction
 
Pulling Force Capability
 
Pulling Heads
 
References
 

Procedure


HDD is a trenchless construction method that involves drilling a small pilot hole, using technology that allows the drill to be steered and tracked from the surface. The pilot bore is launched from the surface at an angle between 8 and 20 degrees to the horizontal, and transitions to horizontal as the required depth is reached.

A bore path of very gradual curvature or near-straight alignment is normally followed to minimize friction and to stay within the allowable joint deflection and the allowable curve radius for the pipe. This minimizes the chance of getting the pipeline “hung up” in the soil or damaging the pipe. The pilot hole is enlarged (usually approximately 1.5 times the largest outside diameter of the new pipe) by pulling back increasingly larger reamers, or reaming heads, from the pipe insertion point to the rig side. To achieve the appropriate bore path size it may be necessary to perform several reaming operations.

Generally, all reaming procedures prior to the actual product installation are referred to as pre-reams, and the final ream to which the product pipe is attached is referred to as the back ream. After the pre-reams, the pulling head and connecting product pipe are attached to the reamer using a swivel, a device that isolates the product pipe from the rotation of the HDD drill pipe. The product pipe is then pulled behind the final reamer back through the horizontal directional drill path to the exit pit on the rig side.

Pilot hole


Mud motors

The tool used for drilling extended distances in solid rock formations is the mud motor. Mud motors consist of an angled housing, a power conversion section, a bearing section, and a rock cutting bit which rotates (See Figure ( a ). The angled sub is rigidly attached to the drill pipe extending from the boring unit. The angled section biases the bit to one side of the bore hole such that it will cut a curved section when thrusting forward without rotation, and will cut a predominantly straight path when advanced while rotating. As the name implies, a mud motor is powered by flow and pressure from the drilling fluid pumped through the drill stem. The power section, which may be 10 ft (3 m) in length or more, has a fixed displacement progressive cavity which drives the bit rotation as drilling fluid is pumped through. Mud motors may drill and steer effectively in formations with compressive strengths approaching 30,000 psi (200 MPa). Mud motors will be used with wireline steering tools which make them well suited to river and channel crossings where tool position must be determined by dead reckoning, i.e. calculation of position based on known orientation and travel distance, for a portion of the bore.


Figure (a). Typical mud motor drilling configuration.

A mud motor cutting a hole as small as 6 in (15 cm) can easily require 120 gal/min (450 l/min) of drilling fluid or more to operate effectively. This flow rate of fluid necessitates the use of a fluid cleaning/recycling system to allow the drilling fluid which returns from the bore hole to be cleaned of rock cuttings and pumped back through the hole. If a fracture in the rock formation is encountered downhole, fluid loss quickly becomes a serious problem for the driller. In addition, pressure loss in the fluid as it passes through the drill pipe reduces the energy available to transfer to bit in the mud motor. Thus, the longer the bore becomes, the less efficiently the mud motor will operate.

Drilling Mud

“Drilling mud” is normally utilized to lubricate the cutting head during the drilling operation and stabilize the reamed bore path prior to and during pull-back. The “drilling mud” usually consists of a mixture of fresh water and bentonite clay; however, other materials such as polymers are sometimes used. Bentonite is a naturally occurring clay mineral that forms a mud when mixed with water. Drilling fluids are characterized by their viscosity, gel strength, filtration, fluid loss, fluid density, pH, and lubricity. The
Principal functions of drilling fluids used in HDD are:

  1. Transporting drill cuttings to the surface by suspending and carrying them in slurry that flows in the annulus between the bore wall and the drill/product pipe.
  2. Cleaning build-up on drill bits or reamer cutters by directing fluid streams at the cutters.
  3. Cooling the down hole tools and electronic equipment.
  4. Lubricating to reduce the friction between the drill pipe/ product and the bore wall.
  5. Stabilizing the bore path, especially in loose or soft soils, by building a low-permeability filter cake and exerting a positive hydrostatic pressure against the bore path wall. The filter cake and positive hydrostatic pressure reduce obstruction of the bore path and prevent formation fluids (i.e., groundwater) from flowing into the bore, or drilling fluids from exiting the bore path into the formation (loss of circulation).
  6. Providing hydraulic power to down hole mud motors.

For HDD, the proper drilling fluid mixture and delivery pressure is heavily dependent upon the type of soil encountered. It must be formulated for the anticipated geological conditions. For simplicity, soil conditions may be defined as either a coarse soil (sand and gravel) or a fine soil (clay, silt, and shale). In general, for coarse soils bentonite should be used, while for fine soils polymers (possibly added to a bentonite base) are recommended.

Pre-reaming

Tooling for backreaming in rock with HDD

As with all horizontally drilled bores, a successful pilot bore in rock is only the first challenge in a complete utility line installation. Tooling for backreaming is also specialized and is selected in accordance with the encountered rock formation and the drilling unit being utilized .

Drag-type, or scraping backreamers

These reamers typically feature carbide buttons or carbide tipped teeth on a reamer body which is rigidly attached to the drill pipe to rotate in conjunction with the pipe. As the reamer rotates, the carbide segments scrape along the face of the borehole to break or gouge away the rock. A couple examples of drag-type reamers are shown in Figures 6A and 6B. These reamers will be used with directional drilling unit.

The heavy construction of reamer Figure 6B and progressive spiral shape of this reamer are particularly effective in cutting through cobble formations and tightly packing the hole walls to provide smooth entry for the installed product.


Figure 6A.
Three Wing Rock reamer from Ditch Witch.
Figure 6B.
Kodiak Cobble reamer from Ditch Witch.

Rolling element backreamers

For solid rock formations whose compressive strengths render the drag-type reamers ineffective, the use of rolling element reamers is common. These reamers fracture the rock in much the same way as a tri-cone bit for pilot drilling. As the reamer is pulled into the face of the excavation and rotated, hardened steel teeth or carbide buttons embedded in steel “cones” roll across the rock face and create small compression fractures in the rock surface at each tooth/rock interface. A couple types of rolling element reamers are shown in Figures A1 and A2.


Figure A1.
Replaceable cone hole
Figure A 2.
Split-bit type reamer. opener.

The reamer of Figure A1 is typically referred to as a hole opener and features specially shaped cones which may be readily replaced as they wear. The buttons on this reamer which contact the rock to fracture it. Hole openers with carbide inserts, or TCI reamers, are used for harder, more abrasive rock formations. The reamer of Figure A 2 is commonly known as a “split-bit” reamer.

Installation Methods for HDD of HDPE Pipe

Actual installation of the pipe in an HDD application involves maintaining an unobstructed bore path that the pipe is pulled through as smoothly and quickly as possible. HDD installations with HDPE pipe have an advantage over other pipe materials since the installation can be readily accomplished by either the Butt fusion method, where pipes are pre-assembled on an adjacent right of way, then pulled in as a single unit.

Pull-back

The pull-back operation involves pulling the entire pipeline length in one segment (Usually) back through the drilling mud along the reamed-hole pathway. Proper pipe handling, cradling, bending minimization, surface inspection, and fusion welding procedures need to be followed. Axial tension force readings, constant insertion velocity, mud flow circulation/exit rates, and footage length installed should be recorded. The pullback speed ranges usually between 1 to 2 feet per minute.

Pipe Bore Path Friction

Case histories have given indications “that pulling loads were less for HDPE pipe than they typically were for similar size steel pipe.”3 One reason for this is that the bulk density of empty HDPE pipe is normally closer to that of the soil/fluid slurry than it is with lighter pipe materials. Therefore, there may often be very little normal force from gravity or buoyancy to result in increased friction against the walls of the bore hole as the pipe is pulled back.4
In HDD installations, restrained joint pipe bells can be oriented to minimize friction of the bell in pulling through the bore hole.

This allows the drilling fluid and excavated material to flow easily over the smooth contour of the bells. With low-profile, internal ring joint designs this is normally the spigot-forward orientation, but this varies by joint design, and pipe manufacturers should
be consulted.

Pulling Force Capability

Our HDD machines are capable of generating tremendous pulling forces. The pipe joint must be capable of withstanding these forces. HDPE pipe manufacturers have proprietary restrained joints with substantial strength that they recommend for HDD applications. Contact the individual pipe manufacturers for their recommended maximum allowable pulling force.

Pulling Heads

After the pre-reaming operation(s) has been completed, a swivel connector is attached between the final reamer and the pulling head. The pulling head is then attached to the spigot end of the first piece of pipe. There are many different pulling head designs. Pulling heads may be fabricated by the installer or obtained from some pipe manufacturers.

References



Site Address District Pipe Installed
Chichar Canal Gujranwala
Chichar Canal Gujranwala
Samrial Canal
Babu Sabu Lahore
Khoari Canal
Lado Sodra Canal
Lado Road Cross
Nandipur Canal Small
Nandipur Canal
Sahuwala Canal
Nala one Sialkot
Daska Canal
Kamra Haji Shah
Tarnab Farm
Shershah Canal
Sodra Canal
DHA-01
DHA-02
Nasir Killay Pabbi
Pehllwan Hotel Pabbi
Khawarzai Nala Pabbi
College Stop Pabbi
Rashakai Mardan
Bilal Masjid Mardan
Chamkani
Ring Road Mandi Mawashian
Jaba Bridge Peshawar
Shorkot Shikarpur
Shorkot Shikarpur
Shorkot Shikarpur
Central Jail Shikarpur
Central Jail Shikarpur
Central Jail Shikarpur
Ibrahim Kot Shikarpur
Ibrahim Kot Shikarpur
Ibrahim Kot Shikarpur
Habib Kot Shikarpur
Habib Kot Shikarpur
Habib Kot Shikarpur
DC Office Shikarpur
Gujranwala
Gujranwala
Sialkot
Lahore
Lahore
Wazirabad
Wazirabad
Gujranwala
Gujranwala
Sialkot
Sialkot
Daska
Attock
Peshawar
Multan
Wazirabad
Islamabad
Islamabad
Peshawar
Peshawar
Peshawar
Peshawar
Mardan
Mardan
Peshawar
Peshawar
Peshawar
Shikarpur
Shikarpur
Shikarpur
Shikarpur
Shikarpur
Shikarpur
Shikarpur
Shikarpur
Shikarpur
Shikarpur
Shikarpur
Shikarpur
Shikarpur
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm
HDPE 90mm

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