Is Location & Guidiance Important In Drilling?
Location and guidance of the drilling is an important part of the drilling operation, as the drilling head is under the ground while drilling and, in most cases, not visible from the ground surface. Uncontrolled or unguided drilling can lead to substantial destruction, which can be eliminated by properly locating and guiding the drill head.
There are three types of locating equipment for locating the bore head: the walk-over locating system, the wire-line locating system and the gyro guided drilling, where a full inertial navigation system is located close to the drill head. In first both systems a sonde, or transmitter, behind the bore head registers angle, rotation, direction, and temperature data.
This information is encoded into an electro-magnetic signal and transmitted through the ground to the surface in a walk-over system. At the surface a receiver (usually a hand-held locator) is manually positioned over the sonde, the signal is decoded and steering directions are relayed to the bore machine operator. In a wire-line system, this information is transmitted through the cable fitted within the drill string.
Those both systems have their own merits, and a particular system is chosen depending upon the site requirements. The gyro based system is fully autonomously working and therefore one of the most accurate system where sufficient diameter (200 mm) is available and where long distances (up to 2 km) have to be performed with small deviation (less than 1 m position error).