Horizontal Directional Drilling

To make you interested in the services we offer, we would like to tell you  about the idea of the technology which we use, describing its particular stages:

 

DRILLING THE PILOT HOLE

The result of this stage is to drill through under an obstacle by means of drilling pipes according  to a prior trajectory design.

 To do this, the first rod is tipped with a boring head equipped with a jet bit. Such equipment is drilled down into the ground with the following drill pipes being regularly attached. The pilot string has a cable probe which constantly informs the people taking the measurement and operating the rig about the drilling parameters ( the depth, the pilot string inclination). The data are broadcast or – in case of strong disturbances generated by outer sources (like power lines) – through a cable inside the drill pipe (cable probe). Steering is about the proper coordination of a boring head with a rotation and feed  transmitted from the rig to the drill pipes line.  

If an unexpected obstacle is met while drilling, it is possible to withdraw a few rods and change the direction to pass it. Experienced navigation systems operators cooperating with the rig operators can exit the pilot hole exact to a dozen or so centimeters, regardless of the length of the bore.   
During the bore, it is necessary to supply bentonite mud through the drill pipes and nozzles on the boring head. It is done to help work the ground, to carry the borings outside, to cool the boring head and to lubricate the outer walls of the rods.

 

ENLARGING THE HOLE

 

When the pilot hole is ready, the boring head is disassembled and then a reamer is attached in this place to enlarge the diameter of the hole.  The reamer is drilled down and drawn in the direction of the machine. While this is carried out, the following  drill pipes are screwed in. After the whole drilling cycle is finished and the reamer is disassembled, the rod following the reamer is connected to the rig. Another reamer Is attached to the other side of the drill string (on the pipe site) and the next reaming  is carried out. Depending on the type and diameter of the pipe which is to be pulled through, geological conditions and the length of the bore, the hole is enlarged up to a diameter by 20 to 100 % bigger than the diameter of the pipe.

Similar to the pilot hole, drilling mud – flowing out of the nozzles which are placed on the reamer walls -  is supplied  all the time. The basic task of the drilling mud in this stage is to carry the borings outside the bore, work its walls, cool the reamer and stabilize the hole’s walls. It is important to control and make the bentonite mud flow outside the hole together with the borings.   

 

PIPE INSTALLATION

 

 The last stage of the bore is installing the pipe.  When the hole is ready (enlarged to a needed diameter, with its walls stabilized, and cleaned), the pipe may be pulled through. The reamer ( provided with a swivel joint which prevents the pipe from rotating) is connected to the product pipe, whose end is equipped with a towing head.  The reamer in this state together with the pipe is pulled through the hole. This stage must be carried out continually and all the possible breaks should not be longer than the duration of all the necessary operations, like unscrewing and disassembling the rod on the rig.