Rotary steerable system called RSS, allows the string to rotate continuously, and at the same time, steer the string to the desired target location. The latest generation of these can actively steer themselves toward a defined target without intervention from the surface. A big advantage in rotary steerable systems is that by rotating the drill-string, axial drag is reduced, increasing the amount of WOB available at the bit. Due to the rotation of the drill-string, there is also a considerable improvement of hole cleaning, and reduced risk of differential sticking.
Rotary Steerable System Tool
There are two types of RSS system:
Point-the-bit allows the bit to tilt up, right, down or left, to the desired direction, using some deflection mechanism whereas the push-the-bit allows the bit to be forced to the desired direction using the bit side force. Due to the nature of the mode, the bit should be compatible to withstand the side forces. The push-the-bit system should have a side-cutting structure, and short gage vis-à-vis long gauge, for point-the-bit to act as pivot for deflection.
The mechanism involved may have adjustable stabilizers, kickpads, cams, eccentric rings, etc,. allowing the various options of tilt angles.