Method and apparatus for controlling the force applied to a drill bit while drilling

Abstract From the Canadian patent

A method of apparatus for controlling in a wellbore the force applied to a rotating drill bit of the type having fluid circulating through an opening in the lower end thereof. One aspect of the method comprises sensing the torque in the drill bit and varying the flow of the circulating fluid through the drill bit responsive to the torque. Apparatus is provided for maintaining constant torque in the drill bit by varying the fluid flow through the bit, which varies in turn the weight applied to the bit and therefore bit torque.