APPARATUS AND A METHOD FOR DRILLING BOREHOLES

摘要

An apparatus (10) for inclusion in a string having a drill bit located at one end is described. The apparatus (10) comprises a body (20) having a longitudinal axis which is substantially coaxial with the longitudinal axis of the string. A portion (30) of the body (20) has a cross section where the centre of mass of the body (20) on that cross section is offset from the longitudinal axis of the string. A method of reducing the variation of a drill bit from an intended path (1) in a borehole is also described, where the drill bit is coupled to one end of a string having a longitudinal axis. The method comprises the steps of including a body (20) in the string, where a portion of the body (20) has a cross section where the centre of mass of the body (20) on that cross section is offset from the longitudinal axis of the string. The string is inserted into a borehole, and at least the portion of the body (20) is rotated.