Patent ID: 9598904
Date: 2017-03-21
CPC Classifications: E21B

Claim:
1. A method for drilling a borehole through an earth formation with a drilling system comprising: a drillstring comprising a rotatable shaft at the leading end of which is a drill bit; a drive coupled with the upper end of the drillstring and configured to rotate the drillstring in the borehole: a variable friction inducing member coupled with the drillstring wherein the variable friction inducing member comprises a plurality of extendable elements disposed around the drillstring circumference and configured in use to provide a rotational friction by physical contact with an inside face of the borehole, wherein the friction inducing member is arranged to exert a first rotational frictional force when the shaft in the vicinity of the member is substantially rotating and a second rotational frictional force when the shaft in the vicinity of the member is substantially not rotating, wherein the first rotational frictional force is less than the second rotational frictional force; and a downhole motor coupled with the drillstring between the variable friction inducing member and the drill bit and configured for rotating the drill bit, the method comprising periods of rotating the drillstring with the drive at the surface during which the extendable elements of the friction inducing member are retracted so that the friction inducing member exerts the first rotational frictional force, and periods of rotating the drill bit with the downhole motor while the drillstring is substantially not rotating and the extendable elements are extended and the friction inducing member exerts the second rotational frictional force.