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US 6,089,332 AGranted
Steerable rotary drilling systems
AssigneeCamco International (UK) Limited
InventorsJohn D. Barr, John M. Clegg, William C. Motion
Life of this patent
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AssigneeCamco International (UK) Limited
InventorsJohn D. Barr, John M. Clegg, William C. Motion
Estimating the term…
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 displaceable outwardly for engagement with the formation of the borehole being drilled. Each actuator may be connected, through a control valve, to a source of drilling fluid under pressure and the operation of the valve is controlled by the control unit so as to modulate the fluid pressure supplied to the actuators as the bias unit rotates. If the control valve is operated in synchronism with rotation of the bias unit the thrust members impart a lateral bias to the bias unit, and hence to the drill bit, to control the direction of drilling. Pulses transmitted through the drilling fluid as a result of operation of the bias unit are detected and interpreted at the surface, or at a different location downhole, to obtain information regarding the operation of the bias unit or other parts of the bottom hole assembly. Data signals from downhole sensors may be arranged to modify the control and operation of the bias unit in such manner that the data is encoded as pulses generated in the drilling fluid by the bias unit.
A method of operating a steerable rotary drilling system having a bottom hole assembly which includes a drill bit, a modulated bias unit and a control unit, the bias unit comprising a number of hydraulic actuators at the periphery of the unit for engagement with the formation of the borehole being drilled, each hydraulic actuator including a movable thrust member which is hydraulically displaceable, and each movable thrust member having an inlet passage for connection to a source of pressurised fluid, the pressure of fluid supplied to the movable thrust members from said source being controlled by valve means and the operation of the valve means being controlled by the control unit so as to modulate the fluid pressure supplied to the actuators as the bias unit rotates, the method including the step of deriving data signals from sensors in the bottom hole assembly, causing the control unit to control the bias unit in a manner dependent on said data signals from the sensors, detecting pulses transmitted through the fluid as a result of the consequent operation of the bias unit, and interpreting said pulses to derive therefrom data corresponding to said data signals from said sensors.
A method of operating a steerable rotary drilling system having a bottom hole assembly which includes a drill bit, a modulated bias unit and a control unit, the bias unit comprising a number of hydraulic actuators at the periphery of the unit for engagement with the formation of the borehole being drilled, each hydraulic actuator including a movable thrust member which is hydraulically displaceable, and each movable thrust member having an inlet passage for connection to a source of pressurised fluid, the pressure of fluid supplied to the movable thrust members from said source being controlled by valve means and the operation of the valve means being controlled by the control unit so as to modulate the fluid pressure supplied to the actuators as the bias unit rotates, the method comprising the steps of detecting pulses transmitted through the fluid as a result of operation of the bias unit, and interpreting said pulses to obtain information regarding the operation of the bottom hole assembly including the bias unit.
Dependencies are inferred from the claim text.