Patent ID: 6321857
Filing Date: 2001-11-27
Classification: E21B

Abstract:
Directional drilling apparatus for location on a drill string for location in an inclined bore having a lower side, the apparatus comprising:a stabiliser comprising a mandrel for connection to a drill string, the mandrel being adapted for rotation about a longitudinal axis, and a normally non-rotating offsetting means mounted on the mandrel for offsetting the string in the bore; andorientation control means operatively associated with the offsetting means and including a non-rotating offset mass having a center of gravity laterally spaced from said longitudinal axis whereby said offset mass tends to an orientation in the bore with its center of gravity towards the lower side of the bore and said mass is adapted to be coupled to said offsetting means for maintaining a selected circumferential orientation of the offset of the string in the bore as the drill string rotates therein.