Directional drilling control using modulated bit rotation

• US 7,766,098 B2
• Filed: 08/31/2007
• Issued: 08/03/2010
• Est. Priority Date: 08/31/2007
• Status: Expired due to Fees

• Current Assignee: Weatherford Technology Holdings, LLC (Weatherford International PLC)
• Original Assignee: Precision Energy Services Incorporated (Weatherford International PLC)
• Inventors: Farley, Steven Reid
• Primary Examiner(s): Neuder; William P
• Assistant Examiner(s): Harcourt; Brad
• Application Number:
  US11/848,328
• Publication Number:
  US 20090057018A1
• Time in Patent Office: 1,068 Days
• Field of Search: 175/26, 175/45, 175/61, 175/62, 175/103, 175/73
• US Class Current: 175/61
• CPC Class Codes: E21B 7/067 with means for locking sections of a pipe or of a guide for a shaft in angular relation, e.g. adjustable bent sub
• CPC Class Codes: E21B 7/068 drilled by a down-hole drilling motor down-hole drives per se E21B4/00, E21B7/067 takes precedence

Abstract

A system for steering the direction of a borehole advanced by cutting action of a rotary drill bit by periodically varying the rotation speed of the drill bit. The steering system comprises a motor disposed in a bent housing subsection and operationally connected to a drill string and to the drill bit. The rotation speed of the drill bit is periodically varied by periodic varying the rotation speed of the motor or by periodic varying the rotation speed of the drill string. Periodic bit speed rotation results in preferential cutting of material from a predetermined arc of the borehole wall which, in turn, resulting in borehole deviation. Both the drill string and the drill motor are rotated simultaneously during straight and deviated borehole drilling.

Claims

1. A method for deviating a borehole advanced by a rotating drill bit, the method comprising:

periodically varying rotation speed of said drill bit to preferentially remove a disproportional amount of material in an azimuthal arc of a wall of said borehole;

periodically varying, at a speed variation angle, said rotation speed of said drill bit from a first rotation speed to a second rotation speed;

maintaining said second rotation speed through a dwell angle; and

subsequently resuming said first rotation speed.

2. The method of claim 1 further comprising varying rotation of said drill bit by periodic varying rotation speed of a drill bit motor to which said drill bit is operationally attached.

3. The method of claim 1 further comprising periodic varying rotation speed of said drill bit by periodic varying rotation rate of a drill string to which said drill bit is operationally attached.

4. The method of claim 1 wherein:

said drill bit is operationally attached to a drill bit motor and to a drill string; and

said drill bit motor and said drill string are simultaneously rotated while rotation speed of said drill bit is periodically varied.

5. The method of claim 1 further comprising telemetering, from the surface of the earth, said speed variation angle and said dwell angle to downhole processor cooperating with said drill bit motor thereby periodic varying said rotation speed of said drill bit by controlling said rotation speed of said drill bit motor.

6. The method of claim 1 further comprising:

storing said speed variation angle and said dwell angle in a downhole memory; and

transferring said speed variation angle and said dwell angle to downhole processor cooperating with said drill bit motor thereby periodic varying said rotation speed of said drill bit by controlling said rotation speed of said drill motor.

7. The method of claim 1 further comprising telemetering, from the surface of the earth, said speed variation angle and said dwell angle to a downhole processor cooperating with a drill bit motor thereby periodically varying said rotation speed of said drill bit by controlling said rotation speed of said drill bit motor.

8. The method of claim 1 further comprising:

storing said speed variation angle and said dwell angle in a downhole memory; and

transferring said speed variation angle and said dwell angle to a downhole processor cooperating with said drill motor thereby periodically varying said rotation speed of said drill bit by controlling rotation speed of said drill motor.