Directional Drilling Using Variable Bit Speed, Thrust, and Active Deflection

Abstract

A downhole assembly for directionally drilling a borehole has a motor, a transmission, and a steering mechanism. The motor has a rotor driven in a stator by flow of drilling fluid therebetween. The transmission operatively couples the rotor to a drill bit for drilling the borehole. A flow control controls the flow of drilling fluid through an internal passage of the rotor. The flow control can thereby vary the drive of the rotor in a bit speed effect that preferentially cuts the wall of the borehole to achieve directional drilling. The flow control can also thereby create a differential pressure displacing the rotor along a longitudinal axis of the motor in a thrust effect. The steering mechanism responds to the displacement of the rotor and deviates a direction of the drill bit from the longitudinal axis of the motor to further achieve directional drilling. The bit speed effect, the rotor displacement, and the deviation are preferentially coordinated to coincide or at least operate together.

What is claimed is: 
     
         1 . A drilling assembly for deviating a borehole advanced by a drill bit, the drilling assembly comprising:
 a motor having a rotor driven by flow of fluid through the motor;   a transmission transferring the drive of the rotor to the drill bit; and   a flow control controlling the flow of fluid through the motor and creating a change in differential pressure in the motor, the change in differential pressure periodically varying a thrust load applied by the motor in advancing the borehole.   
     
     
         2 . The assembly of  claim 1 , wherein the flow control bypasses at least a portion of the flow of fluid away from the motor. 
     
     
         3 . The assembly of  claim 1 , wherein the flow control is disposed within the flow of fluid. 
     
     
         4 . The assembly of  claim 1 , wherein the periodic variation of the thrust load varies an effective weight-on-bit of the assembly and thereby disproportionately engages the drill bit within the borehole. 
     
     
         5 . The assembly of  claim 1 , wherein in controlling the flow of fluid through the motor, the flow control further periodically varies the drive of the rotor and thereby disproportionally engages the drill bit within the borehole. 
     
     
         6 . The assembly of  claim 1 , wherein the rotor defines an internal passage therethrough; and wherein the flow control controls the flow of fluid through the internal passage of the rotor. 
     
     
         7 . The assembly of  claim 1 , wherein a distal section of the assembly is at least partially articulatable or is disposed at a preconfigured bend relative to a proximal section of the assembly, the proximal section having the motor, the distal section extending from the proximal section and supporting the drill bit. 
     
     
         8 . The assembly of  claim 1 , wherein the transmission comprises one or more transmission shafts operatively coupled between the rotor and a drive mandrel, the drive mandrel having the drill bit and supported by a bearing assembly. 
     
     
         9 . The assembly of  claim 1 , wherein the rotor is at least partially displaceable along a longitudinal axis of the motor, and wherein the change in differential pressure at least partially displaces the rotor along the longitudinal axis of the motor. 
     
     
         10 . The assembly of  claim 1 , wherein in the periodic variation of the thrust load, the rotor periodically displaces along a longitudinal axis of the motor and thereby disproportionally engages the drill bit within the borehole. 
     
     
         11 . The assembly of  claim 10 , wherein in controlling the flow of fluid through the motor, the flow control further periodically varies the drive of the rotor and thereby disproportionally engages the drill bit within the borehole. 
     
     
         12 . The assembly of  claim 11 , wherein the periodic variation of the drive of the rotor is coordinated with the periodic displacement of the rotor. 
     
     
         13 . The assembly of  claim 1 , further comprising a mechanism responding to the thrust load of the motor and deviating at least a portion of the drilling assembly in the borehole. 
     
     
         14 . The assembly of  claim 13 , wherein in the periodic variation of the thrust load, the rotor periodically displaces along a longitudinal axis of the motor and deviates the portion of the drilling assembly. 
     
     
         15 . The assembly of  claim 13 , wherein in controlling the flow of fluid through the motor, the flow control further periodically varies the drive of the rotor and thereby disproportionally engages the drill bit within the borehole. 
     
     
         16 . A drilling assembly for deviating a borehole advanced by a drill bit, the drilling assembly comprising:
 a motor having a rotor, the rotor driven by flow of fluid through the motor and being at least partially displaceable along a longitudinal axis of the motor;   a transmission transferring the drive of the rotor to the drill bit; and   a flow control controlling the flow of fluid through the motor and creating a differential pressure at least partially displacing the rotor along the longitudinal axis of the motor.   
     
     
         17 . The assembly of  claim 16 , wherein the differential pressure creates a thrust load upon the rotor and causes displacement of the rotor. 
     
     
         18 . The assembly of  claim 17 , wherein the varied thrust load applied by the motor varies an effective weight-on-bit of the assembly and thereby disproportionately engages the drill bit within the borehole. 
     
     
         19 . The assembly of  claim 16 , wherein in controlling the flow of fluid through the motor, the flow control further periodically varies the drive of the rotor and thereby disproportionally engages the drill bit within the borehole. 
     
     
         20 . The assembly of  claim 16 , wherein the rotor defines an internal passage; and wherein the flow control is operable between first and second conditions to control the flow of fluid through the internal passage of the rotor. 
     
     
         21 . The assembly of  claim 20 , wherein the flow control comprises a valve movable relative to a seat communicating the flow with the internal passage of the rotor. 
     
     
         22 . The assembly of  claim 20 , wherein the flow control produces a first of the differential pressure across the rotor when in the first condition and produces a second of the differential pressure across the rotor when in the second condition, the second differential pressure being greater than the first differential pressure. 
     
     
         23 . The assembly of  claim 16 , wherein the flow control further comprises a throttle producing a preconfigured pressure drop in the flow of fluid relative to the rotor. 
     
     
         24 . The assembly of  claim 16 , further comprising a mechanism responding to the displacement of the rotor and deviating at least a portion of the drilling assembly in the borehole. 
     
     
         25 . The assembly of  claim 24 , wherein one portion of the transmission is operatively coupled to the rotor, and wherein another portion of the transmission transfers the displacement of the rotor to the mechanism. 
     
     
         26 . The assembly of  claim 25 , wherein the one portion of the transmission comprises a transmission shaft having a first end operatively coupled to the rotor with a first coupling, and wherein the other portion comprises a second coupling operatively coupled to a second end of the transmission shaft. 
     
     
         27 . The assembly of  claim 24 , wherein the mechanism comprises a joint movably disposed on the drilling assembly, the joint pivoting in response to the displacement of the rotor and deviating at least a portion of the drilling assembly in the borehole. 
     
     
         28 . The assembly of  claim 27 , wherein the joint comprises a first section responsive to the displacement of the rotor and comprises a second section disposed relative to the drill bit, the first section of the joint responding to the displacement of the rotor and pivoting the second section relative to the first section. 
     
     
         29 . The assembly of  claim 28 , wherein the mechanism comprises a piston biased relative to the displacement of the rotor, the piston responsive to the displacement of the rotor and engaging the first section of the joint. 
     
     
         30 . The assembly of  claim 29 , wherein the piston and the first section comprise cooperative contact points transferring the displacement of the rotor off the longitudinal axis of the motor. 
     
     
         31 . The assembly of  claim 24 , wherein the mechanism comprises at least one pad movably disposed on the drilling assembly, the at least one pad extending from the drilling assembly in response to the displacement of the rotor and deviating at least the portion of the drilling assembly within the borehole. 
     
     
         32 . The assembly of  claim 31 , wherein the mechanism comprises a sleeve shifting along the longitudinal axis in response to the displacement of the rotor, the shifted sleeve extending the at least one pad from the drilling assembly. 
     
     
         33 . The assembly of  claim 32 , wherein the mechanism comprises a piston biased relative to the displacement of the rotor, the piston responsive to the displacement of the rotor and shifting the sleeve. 
     
     
         34 . A method of drilling an advancing borehole with a drill bit of a drilling assembly, the method comprising:
 driving a rotor of the drilling assembly by flowing fluid through the drilling assembly;   transmitting the drive of the rotor to the drill bit; and   deviating the drilling assembly in the advancing borehole by:
 controlling the flow of fluid through motor, and 
 creating a differential pressure at least partially displacing the rotor along a longitudinal axis of the drilling assembly. 
   
     
     
         35 . The method of  claim 34 , wherein deviating the drilling assembly in the advancing borehole comprises disproportionally engaging the drill bit in the advancing borehole. 
     
     
         36 . The method of  claim 35 , wherein disproportionally engaging the drill bit in the advancing borehole comprises periodically displacing the rotor along the longitudinal axis of the drilling assembly by controlling the flow of fluid through an internal passage of the rotor. 
     
     
         37 . The method of  claim 36 , wherein disproportionally engaging the drill bit in the advancing borehole further comprises periodically varying the drive of the rotor with the control of the flow of fluid through the internal passage of the rotor. 
     
     
         38 . The method of  claim 34 , wherein controlling the flow of fluid through the motor comprises:
 determining a steering direction for the drilling assembly;   sensing an angular orientation of the drilling assembly; and   controlling the flow through the motor based upon the determined steering direction and the sensed angular orientation.   
     
     
         39 . The method of  claim 34 , wherein deviating the drilling assembly in the advancing borehole comprises moving at least a portion of the drilling assembly by responding to the displacement of the rotor. 
     
     
         40 . The method of  claim 39 , wherein moving by responding to the displacement of the rotor comprises articulating a distal end of the drilling assembly having the drill bit relative to a proximal end of the drilling assembly. 
     
     
         41 . The method of  claim 40 , wherein articulating the distal end relative to the proximal end comprises pivoting the distal end on a joint in response to the displacement of the rotor being offset from the longitudinal axis by the joint. 
     
     
         42 . The method of  claim 39 , wherein moving by responding to the displacement of the rotor comprises extending a portion of the drilling assembly against the borehole. 
     
     
         43 . The method of  claim 42 , wherein extending a portion of the drilling assembly against the borehole comprises shifting a sleeve in response to the displacement of the rotor and extending a movable pad transverse to the drilling assembly with the shifted sleeve.