1
Michael K Russell, John D Barr: Steerable rotary drilling systems. Camco Drilling Group, November 30, 1993: US05265682 (193 worldwide citation)

A system for maintaining a downhole instrumentation package in a roll stabilised orientation with respect to a drill string comprises an instrument carrier which is mounted within a drill collar for rotation about the longitudinal axis of the collar. An impeller is mounted on the instrument carrier ...


2
John D Barr, Mark W Burrell, Robert A Russell, Richard Thorp, David Boast, John Clegg: Modulated bias units for steerable rotary drilling systems. Camco International, September 10, 1996: US05553678 (186 worldwide citation)

A modulated bias unit is provided for controlling the direction of drilling of a rotary drill bit when drilling boreholes in subsurface formations. The unit comprises a plurality of hydraulic actuators spaced apart around the periphery of the unit and having movable thrust members hydraulically disp ...


3
John D Barr: Steerable rotary drilling systems. Camco Drilling Group of Hycalog, January 13, 1998: US05706905 (183 worldwide citation)

A modulated bias unit, for use in a steerable rotary drilling system, comprises a number of hydraulic actuators spaced apart around the periphery of the unit, each having a movable thrust member which is hydraulically displaceable outwardly for engagement with the formation of the borehole, and a co ...


4
John D Barr, Richard E Thorp, Robert A Russell: Modulated bias unit for rotary drilling. Camco Drilling Group, May 28, 1996: US05520255 (159 worldwide citation)

A modulated bias unit, for controlling the direction of drilling of a rotary drill bit when drilling boreholes in subsurface formations, comprises a number of hydraulic actuators spaced apart around the periphery of the unit, each having a movable thrust member which is hydraulically displaceable ou ...


5
John D Barr: Modulated bias unit for rotary drilling. Camco Drilling Group, December 10, 1996: US05582259 (126 worldwide citation)

A modulated bias unit, for controlling the direction of drilling of a rotary drill bit when drilling boreholes in subsurface formations, comprises a number of hydraulic actuators spaced apart around the periphery of the unit. Each actuator comprises a movable thrust member which is hydraulically dis ...


6
John D Barr, John M Clegg, William C Motion: Steerable rotary drilling systems and method of operating such systems. Camco Drilling Group of Hycalog, September 8, 1998: US05803185 (122 worldwide citation)

A steerable rotary drilling system has a bottom hole assembly which includes, in addition to the drill bit, a modulated bias unit and a control unit, the bias unit comprising a number of hydraulic actuators around the periphery of the unit, each having a movable thrust member which is hydraulically ...


7
John D Barr, John M Clegg, William C Motion: Steerable rotary drilling systems. Camco International, Brigitte Jeffery, July 18, 2000: US06089332 (120 worldwide citation)

A steerable rotary drilling system has a bottom hole assembly which includes, in addition to the drill bit, a modulated bias unit and a control unit, the bias unit comprising a number of hydraulic actuators around the periphery of the unit, each having a movable thrust member which is hydraulically ...


8
John D Barr, John M Clegg, William C Motion: Method of operating a steerable rotary drilling system. Camco Drilling Group of Hycalog, November 11, 1997: US05685379 (109 worldwide citation)

A steerable rotary drilling system comprises a bottom hole assembly which includes, in addition to a drill bit, a modulated bias unit and a control unit including an instrument carrier which is rotatable relative to the bias unit. The bias unit comprises a number of hydraulic actuators spaced apart ...


9
John D Barr, William C Motion, Michael K Russell: System and method of controlling rotation of a downhole instrument package. Camco Drilling Group of Hycalog, December 9, 1997: US05695015 (96 worldwide citation)

A system for controlling the rotation of a roll stabilizable control unit in a steerable rotary drilling assembly comprises an instrument carrier rotatably mounted on a support connected to the drill string. A first rotatable impeller is mounted for rotation by a flow of drilling fluid over the impe ...


10
John D Barr: Drag bit and cutters. NL, Browning Bushman Zamecki & Anderson, June 10, 1986: US04593777 (78 worldwide citation)

A drill bit comprises a bit body having an operating end face. A plurality of self-sharpening cutters are mounted in the bit body and extend through the operating end face. The cutters have cutting faces adapted to engage an earth formation and cut the earth formation to a desired three-dimensional ...



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