Introduction Corporate History Technique Site Layouts Rig Suitability Experience Record Project Profiles Contact Us	Technique Drilling the profile A small diameter pilot hole is drilled under directional control to a predetermined path using a mud-motor or jet bit on the end of the pilot string. The pilot string is drilled up to 80 metres in length, then the washover pipe is advanced in rotary mode until it is approximately 30 metres behind the drill bit. Alternate pilot string and drilling operations take place until the exit point is reached. Then the smaller pilot string is removed Enlarging the hole Pre-reaming operations are carried out to enlarge the drilled hole to a size suitable for accepting the product pipe. Pull-back pipe is added behind the reamer. Depending upon the pipe diameter to be installed several pre-reaming operations may be necessary, each progressively enlarging the hole. Installing the pipe The pull-back pipe is connected to a 'cleaning' reamer which in turn connects to a swivel joint, (to prevent pipe rotation) that is attached to the pipeline towhead. The drill rig is then used to pull the product pipe into the preformed hole. The drilling fluid consisting of water and clay minerals will remain in the annulus and protect the pipe.