Patent ID: 6116354
Filing Date: 2000-09-12
Classification: E21B

Abstract:
A rotary steerable system for use in a rotating drill string for drilling a deviated well, the drill string including a drill bit and top sub, comprising:a housing for receiving the rotary steerable system, which housing is connected in the drill string between the drill bit and the top sub for rotation with the drill string;a pad which is installed on the periphery of the housing and which, when actuated, imparts a force to the wall of the borehole;a cartridge in the housing which rotates with the housing;a mechanical gravity reference device comprising (i) an unbalanced weight which is installed in the cartridge and which moves independently of the rotation of the drill string so that the heavy portion of the unbalanced weight is always oriented toward the low side of the borehole, and (ii) a magnet attached to a portion of the gravity reference device;a magnetic switch whose angular position with respect to the pad is known, which switch is mounted in the cartridge proximate the gravity reference device for rotation with the drill string and which switch is activated when its axis coincides with the axis of the magnet; andcircuitry operatively connected to the magnetic switch and responsive to the activation of the magnetic switch to trigger actuation of the pad.