Downhole rotary drilling apparatus with formation-interfacing members and control system

摘要

A steerable drilling apparatus includes a control system inside a cylindrical housing connected to a drill bit having radially-extendable pistons. A piston-actuating fluid flows from the housing and through a fluid-metering assembly which directs fluid into fluid channels in the drill bit leading to respective pistons. The control system controls the fluid-metering assembly to selectively allow fluid to flow through the fluid channels to the pistons and to exit through an orifice in each fluid channel. The selective fluid flow causes pistons in the drill bit to temporarily extend in the opposite direction to a desired wellbore deviation, thereby deflecting it away from the borehole centerline. The fluid-metering assembly has the ability to stabilize, steer, and change TFA within the drill bit by moving an upper member within the fluid-metering assembly. The control system and the drill bit connect in a specific manner to facilitate removal to change the drill bit's steering section and cutting structure configuration or gauge simultaneously.