Drilling of the pilot hole along the designated route will be carried out commonly using a Tri-Cone drill bit and a bent sub assembly which is fixed just behind the drill head during drilling. In hard (rock) ground a down hole (mud) motor will be deployed instead.

The survey probe assembly that monitors the drill path will be positioned along with two non-magnetic drill collars behind the jetting assembly and forms part of the BHA.



Upon completion of the pilot hole, the borehole reaming process will be commenced. Launch pit and mud containment pit will be constructed at the exit position (details enclosed)

The staging and number of reaming passes will depend on the soil formations encountered and the diameter of the utility to be installed. Depending on actual soil conditions, various types of reaming tools can be utilized including barrel reamers, fly cutters and hole openers.

The final borehole size is depending on the product line diameter and should not be less than 1.3 x O.D of the product pipe as a general rule in normal cases. However, the exact reaming program will be defined for each crossing based on job-specific parameters.

To verify and ensure a borehole of suitable condition, the reaming process is followed by a borehole cleaning / calibration phase whereas the final reamer will be run again to guarantee conditioning of the borehole and removal of cuttings. This process may be repeated several times depending on actual borehole condition encountered.

Upon removal of each drill rod on the rig, another rod will be added to the drill string at the pipe site behind the reamer. After the reamer reaches the rig site, it will be dismantled from the drill string, cleaned, inspected and prepared for its next deployment



Upon completion of the final borehole cleaning path, the pulling assembly consisting of a suitable barrel reamer (min 4 inch larger than the product pipe diameter) and a swivel will be connected to the pipeline section through the pulling head.

Then the pipeline section will be pulled to the entry launch pit. A final test of the reamer and jets as well as final pipeline coating inspection will enable the pullback to commence.

Pulling operations will be paused at intervals only to remove drill rods as they are pulled. The removal of the pulling assembly which is consisting of the barrel reamer, the swivel, and the pulling head will take place upon completion of pullback process when the reamer and pulling assembly emerge from the borehole in front of the HDD rig.

During all phases of the drilling operations, a log is kept applicable to each drilled or pulled pipe. During pilot drilling a comprehensive survey data logs are produced for each installed drill pipe.

Together with the survey and drillers logs a daily reports are issued for recording all work progress and forwarded to the client subsequently. Further reports weekly / monthly will be submitted as per the contractual requirements.

Together with the “as-built” documentation, a final report will be issued for the client, containing all the relevant data for the drilling & installation process.



Horizontal Directional Drilling (HDD) is an advanced steerable trenchless technology, used around the globe for the installation of underground utilities along a predesigned bore path. Services include cables, gas lines, crude oil lines, sewer lines, water lines, shore approaches as well as other environmental applications. HDD is particularly useful within settings where the installation of infrastructure utilities by traditional methods, such as trenching or excavation, is not possible. The process requires minimal restoration and leaves an almost negligible impact on the surrounding environment. HDD offers a solution that is more economic, flexible and even quicker-to-finish than other open-cut methods.


The trenchless installation of pipes and cables using the horizontal directional drilling (HDD) method has become a recognized alternative installation in open trenches. Environmentally safe materials makes directional drilling the method of choice on environmental remediation projects and is perfect for utility installations in congested urban environments. Due to the technical advantages of the technology, the minimum adverse effect on the ground surface and its economic efficiency, the (HDD) method is widely used. The practice shows, that application of this technology reduces the operating costs of a traditional technology by a factor of 2 to 3. This method of operation is considerably faster than conventional methods, which means that the job is completed in many instances without people in the area being aware it has been done.



Any size of pipes can 
be utilized.


HDD is unaffected by surface obstacles.


HDD has minimal impact on landscapes and no disruption to streets.


HDD is cost and time efficient


Working area is limited to the drill entry and exit points