POWER SECTION AND TRANSMISSION OF A DOWNHOLE DRILLING MOTOR

• US 20160245022A1
• Filed: 02/25/2015
• Published: 08/25/2016
• Est. Priority Date: 02/25/2015
• Status: Active Grant

• Current Assignee: Nabors Drillling Technologies USA, Inc.
• Original Assignee: Axon Energy Products, Inc.
• Inventors: Leitko, Curtis E. Jr., Mallard, Rory J. Jr., Pittard, Gerard T.
• Granted Patent: US 9,546,518 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: E21B 4/003 Bearing, sealing, lubricating details for roller bits E21B10/22
• CPC Class Codes: E21B 4/02 Fluid rotary type drives
• CPC Class Codes: E21B 7/06 Deflecting the direction of boreholes

Abstract

Present embodiments of the disclosure are directed to power section and transmission components within a downhole drilling motor that may reduce or eliminate axial thrust loads on the transmission of the drilling motor. The transmission may utilize a driven shaft coupled between two connectors that enable torque transfer to and from the transmission while allowing the driven shaft to move freely in two planes. The power section may include a rotor with a through bore and a flex-shaft disposed in the through bore. The flex-shaft may be designed to rotate with the rotor. The flex-shaft may extend beyond the length of the rotor in one direction to be centralized within a bearing assembly. The opposite end of the flex-shaft may include a load-carrying shoulder that is retained in the bottom end of the rotor.

Claims

1. A transmission coupling for use in a downhole drilling motor, comprising:

a shaft for transmitting torque from an upstream power section of the downhole drilling motor to a drive shaft of the downhole drilling motor;

a first connector disposed over a first end of the shaft to couple the first end of the shaft to a first component of the downhole drilling motor;

a first pair of ball bearings disposed between the shaft and the first connector, wherein the first pair of ball bearings are radially offset from each other by approximately 180 degrees about a longitudinal axis of the shaft; and

a first sliding connection disposed between the shaft and the first connector to enable the first pair of ball bearings to move opposite from one another in a direction substantially parallel to an axis of the first connector.

2. The transmission coupling of claim 1, further comprising:

a second connector disposed over a second end of the shaft to couple the second end of the shaft to a second component of the downhole drilling motor;

a second pair of ball bearings disposed between the shaft and the second connector, wherein the second pair of ball bearings are radially offset from each other by approximately 180 degrees about the longitudinal axis, and wherein the second pair of ball bearings are radially offset from the first pair of ball bearings by approximately 90 degrees about the longitudinal axis; and

a second sliding connection disposed between the shaft and the second connector to enable the second pair of ball bearings to move opposite from one another in a direction substantially parallel to an axis of the second connector.

3. The transmission coupling of claim 2, wherein the first pair of ball bearings and the first sliding connection enable the shaft to move freely in two planes relative to the first connector, and wherein the second pair of ball bearings and the second sliding connection enable the shaft to move freely in the same two planes relative to the second connector.

4. The transmission coupling of claim 1, wherein the first component of the downhole drilling motor comprises the upstream power section and wherein the second component of the downhole drilling motor comprises a downstream bearing section having the drive shaft.

5. The transmission coupling of claim 1, wherein the first sliding connection comprises:

a pair of slots formed in the first connector and aligned with the first pair of ball bearings; and

a pair of slide blocks disposed one in each of the pair of slots, wherein the slide blocks comprise rounded surfaces to engage with the pair of ball bearings.

6. The transmission coupling of claim 1, wherein the first end of the shaft comprises a spherical rounded end, and wherein the first connector comprises a spherical socket to receive the spherical rounded end.

7. The transmission coupling of claim 1, wherein the shaft comprises a pair of spherical shaped sockets formed into the first end of the shaft to receive the first pair of ball bearings.

8. The transmission coupling of claim 1, wherein the first connector comprises a keyed connection feature to engage with a corresponding keyed connection feature on the first component to facilitate an axially sliding connection between the first connector and the first component.

9. The transmission coupling of claim 1, further comprising a first seal boot disposed between the shaft and the first connector to seal oil within the first connector.

10. The transmission coupling of claim 1, further comprising a first slide block cap disposed over the first sliding connection to maintain the first sliding connection proximate the shaft.

11. A power section for use in a downhole drilling motor, comprising:

a stator;

a rotor disposed in the stator, wherein the rotor is configured to rotate a drive shaft of the downhole drilling motor via a transmission coupling disposed between the rotor and the drive shaft, wherein the rotor comprises a central bore formed through the rotor;

a flex-shaft disposed in a central bore of the rotor and coupled to the rotor to enable a transfer of axial thrust forces from the rotor to the flex-shaft; and

a thrust bearing assembly, wherein the flex-shaft is centralized in the thrust bearing assembly to support the rotor within the stator such that the axial thrust forces do not transfer from the rotor to the transmission coupling.

12. The power section of claim 11, wherein:

the flex-shaft comprises a first end that is fixed to a first end of the rotor to enable transfer of the axial thrust forces from the rotor to the flex-shaft; and

the thrust bearing assembly is disposed opposite the first end of the rotor, wherein a second end of the flex-shaft opposite the first end is centralized in the thrust bearing assembly to transfer the axial thrust forces from the rotor to the thrust bearing assembly.

13. The power section of claim 12, wherein the second end of the flex-shaft is centralized in a position aligned with a power section axis, the first end of the flex-shaft is fixed in a position aligned with a rotor axis, and wherein the rotor axis is offset from the power section axis.

14. The power section of claim 12, wherein the flex-shaft comprises an axial load carrying shoulder disposed at the first end of the flex-shaft proximate the first end of the rotor, and wherein the first end of the rotor comprises a pair of retainer features disposed one on each side of the load-carrying shoulder.

15. The power section of claim 11, further comprising a seal boot disposed along a portion of the flex-shaft extending from the central bore to seal the central bore.

16. The power section of claim 11, wherein the rotor is coupled to the transmission coupling via a keyed connection feature to facilitate an axially sliding connection between the rotor and the transmission coupling.

17. A method comprising:

rotating a rotor relative to a stator of a downhole drilling motor;

transmitting torque from the rotor to a drive shaft of the downhole drilling motor via a transmission coupling disposed between the rotor and the drive shaft; and

supporting the rotor within the stator to prevent axial loading of the transmission coupling due to axial thrust forces on the rotor during rotation of the rotor.

18. The method of claim 17, wherein supporting the rotor comprises:

transferring axial thrust forces from the rotor to a flex-shaft fixed to the rotor via an axial load carrying connection;

centralizing the flex-shaft within a thrust bearing assembly; and

dissipating the axial thrust forces transferred from the rotor via the thrust bearing assembly.

19. The method of claim 18, further comprising stabilizing and retaining the rotor in position within the downhole drilling motor via the thrust bearing assembly.

20. The method of claim 17, further comprising facilitating an axially sliding connection between the rotor and the transmission coupling of the downhole drilling motor via a keyed connection feature disposed at an end of the rotor.