Varco International, Inc.

Gregory A Goris

Igor Krasnov

Stephen B Wetch

Disclosed is a method and apparatus comprising a side drive system with a drive shaft (24, 24a) driven from the platform level (10) and powering a drilling unit (16) for rotating drill pipe (14). Except for the tethering of the drive shaft at the top of the derrick (60-64) and its coupling to a power source (70) at the platform level, there is preferably no stabilizing means for the system. The drive shaft (24, 24a) is stationary, preferably hollow, and extends the height of the derrick located to one side of the main drilling axis. The power source (70) at the platform level comprises a power takeoff from a conventional rotary table (84). The upper drive assembly (18) of the drilling unit (16) is coupled to the drive shaft (24, 24a) and capable of vertical movement along the drive shaft and providing torque to the drill string. As an option, a stabilizing system for the drilling unit in the form of tension members (182) may be used, or the drive shaft itself may be stabilized at various elevations along its length by stabilizing arms (190) to provide lateral bending restraint yet permitting rotational freedom. The preferred embodiment is such that the side drive system may operate without stabilizing mechanisms for the drilling unit or drive shaft.

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Oxnard, CA, United States of America

Gregory A Goris