Roller cone drill bits with optimized bearing structures

• US 20060032674A1
• Filed: 08/12/2005
• Published: 02/16/2006
• Est. Priority Date: 08/16/2004
• Status: Active Grant

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Inventors: Sui, Ping C., Chen, Shilin
• Granted Patent: US 7,360,612 B2
• Time in Patent Office: Days
• US Class Current: 175/372
• CPC Class Codes: E21B 10/16 characterised by tooth form or arrangement
• CPC Class Codes: E21B 10/22 characterised by bearing, lubrication or sealing details

Abstract

A roller cone drill bit may include optimally designed bearing structures and cutting structures. The roller cone drill bit may include three cone assemblies rotatably mounted on respective spindles via respective bearing structures. Each cone assembly may have a respective cutting structure with a minimal moment center located along each respective axis of rotation. Each respective bearing structure has a center point located proximate each respective minimal moment center.

Claims

1. A roller cone drill bit comprising:

a bit body having a first support arm, a second support arm, and a third support arm extending therefrom;

each support arm having a spindle extending therefrom;

a respective bearing structure associated with each spindle;

a respective cone assembly rotatably mounted on the bearing structure of each spindle for engagement with a subterranean formation to form a wellbore;

a respective cutting structure associated with each cone assembly;

each cone assembly having a respective axis of rotation corresponding generally with a longitudinal axis of each respective spindle;

each cone assembly having a minimal moment center located proximate each respective axis of rotation;

the minimal moment center of each respective cone assembly defined in part by each respective cutting structure; and

each respective bearing structure having a center point located proximate the minimal moment center of the associated cone assembly.

2. The roller cone drill bit of claim 1 further comprising at least one respective bearing structure center point located proximate the minimal moment center of a respective cone assembly operable to minimize at least one anticipated end load acting on the at least one respective bearing structure.

3. The roller cone drill bit of claim 1 further comprising each cutting structure comprising a plurality of cutting elements.

4. The roller cone drill bit of claim 3 wherein the plurality of cutting elements further comprise a plurality of inserts.

5. The roller cone drill bit of claim 3 wherein the plurality of cutting elements further comprise a plurality of milled teeth.

6. The roller cone drill bit of claim 3 further comprising the plurality of cutting elements arranged in at least two rows.

7. The roller cone drill bit of claim 3 further comprising:

each cutting element having a crest extending from the associated cone assembly for engagement with a formation;

each crest having a respective crest point defined as a point located a greater distance from the axis of rotation of the associated cone assembly as compared with the distance between any other point on the crest and the axis of rotation of the associated cone assembly;

each cutting element having a normal force axis extending from the associated cone assembly through the respective crest point;

each cone assembly having a respective cone assembly profile defined in part as a combined projection of the crests of all cutting elements onto a vertical plane passing through the axis of rotation of the respective cone assembly; and

the normal force axes of the cutting elements intersecting at a selected force center point.

8. The drill bit of claim 7 further comprising at least one row of cutting elements on each cone assembly having the respective crest points located at approximately the same radial distance from the rotational axis of the cone.

9. The drill bit of claim 7 further comprising at least two rows of cutting elements on each cone having respective crest points located at approximately the same radial distance from the rotational axis of the cone assembly.

10. The roller cone drill bit of claim 1 further comprising each bearing structure selected from the group consisting of a roller bearing, a journal bearing, and a solid bearing.

11. The roller cone drill bit of claim 1 further comprising:

each cone assembly cutting structure having a cone profile and a set of insert profile angles; and

each respective cone assembly minimal moment center defined by the respective cone profile and respective set of insert profile angles.

12. A roller cone drill bit comprising:

a bit body having at least a first support arm, a second support arm, and a third support arm extending therefrom, each support arm having a spindle extending therefrom;

a respective bearing structure associated with each spindle;

a respective cone assembly rotatably mounted on each bearing structure for engagement with a subterranean formation to form a wellbore, each cone assembly having a distinct cone profile;

each cone assembly having a respective axis of rotation extending from the associated support arm, each axis of rotation corresponding with the longitudinal axis of each respective spindle, each cone assembly having a minimal moment center located along the respective axis of rotation and defined by bearing end loads associated with each distinct cone profile; and

each respective bearing structure having a center point proximate the respective minimal moment center.

13. The roller cone drill bit of claim 12 wherein at least one respective bearing structure center point provided proximate the respective minimal moment center operable to minimize at least one anticipated end load acting on the at least one respective bearing structure.

14. The roller cone drill bit of claim 12 further comprising each cone assembly having a distinct minimal moment center.

15. The roller cone drill bit of claim 12 further comprising each bearing structure selected from the group consisting of a roller bearing, a journal bearing, and a solid bearing.

16. The roller cone drill bit of claim 12 further comprising:

each cone assembly cutting structure having a cone profile and a set of insert profile angles; and

each respective cone assembly minimal moment center defined by each respective cone profile and respective set of insert profile angles.

17. A method for designing a roller cone drill bit comprising:

forming a bit body with at least a first support arm, a second support arm, and a third support arm, each support arm having a spindle extending therefrom;

providing a first cone assembly having a first cutting structure, a second cone assembly having a second cutting structure, and a third cone assembly having a third cutting structure;

determining a first minimal moment center along a first axis of rotation of the first spindle based on the first cone assembly cutting structure;

determining a second minimal moment center along a second axis of rotation of the second spindle based on the second cone assembly cutting structure;

determining a third minimal moment center along a third axis of rotation of the third spindle based on the third cone assembly cutting structure;

providing a first bearing assembly on the first spindle, the first bearing assembly having a center disposed proximate the first minimal moment center;

providing a second bearing assembly on the second spindle, the second bearing assembly having a center disposed proximate the second minimal moment center; and

providing a third bearing assembly on the third spindle, the third bearing assembly having a center disposed proximate the third minimal moment center.

18. The method of claim 17 further comprising:

rotatably mounting the first cone assembly to the first spindle;

rotatably mounting the second cone assembly to the second spindle; and

rotatably mounting the third cone assembly to the third spindle.

19. The method of claim 17 further comprising:

determining the first minimal moment center based upon a first insert profile angle of the first cutting structure;

determining the second minimal moment center based upon a second insert profile angle of the second cutting structure; and

determining the third minimal moment center based upon a third insert profile angle of the third cutting structure.

20. The method of claim 17 further comprising:

determining the first minimal moment center based upon a first cone profile associated with the first cutting structure;

determining the second minimal moment center based upon a second cone profile associated with the second cutting structure; and

determining the third minimal moment center based upon a third cone profile associated with the third cutting structure.

21. The method of claim 17 further comprising:

determining the first minimal moment center based on a set of insert profile angles and a cone profile associated with the first cutting structure;

determining the second minimal moment center based on a set of insert profile angles and a cone profile associated with the second cutting structure; and

determining the third minimal moment center based on a set of insert profile angles and a cone profile associated with the third cutting structure.

22. A method for designing a roller cone drill bit comprising:

providing a bit body with at least a first support arm, a second support arm, and a third support arm, each support arm having a spindle extending therefrom;

providing a first cone assembly having a first cutting structure, a second cone assembly having a second cutting structure, and a third cone assembly having a third cutting structure;

determining a first bearing center point for a first bearing assembly for the first spindle;

determining a second bearing center point for a second bearing assembly for the second spindle;

determining a third bearing center point for a third bearing assembly for the third spindle;

modifying the cutting structure of the first cone assembly to have a first minimal moment center proximate the first bearing center point;

modifying the cutting structure of the second cone assembly to have a second minimal moment center proximate the second bearing center point; and

modifying the cutting structure of the third cone assembly to have a third minimal moment center proximate the third bearing center point.

23. The method of claim 22 further comprising:

modifying the first bearing assembly such that the first bearing center point is located closer to the first minimal moment center;

modifying the second bearing assembly such that the second bearing center point is located closer to the second minimal moment center; and

modifying the third bearing assembly such that the third bearing center point is located closer to the third minimal moment center.

24. The method of claim 22 further comprising:

the modifying of the first bearing assembly occurs simultaneously with modifying the first cutting structure;

the modifying of the second bearing assembly occurs simultaneously with modifying the second cutting structure; and

the modifying of the third bearing assembly occurs simultaneously with modifying the third cutting structure.

25. The method of claim 24 further comprising:

the modifying of the first bearing assembly and the modifying of the first cutting structure occurs iteratively;

the modifying of the second bearing assembly and the modifying of the second cutting structure occurs iteratively; and

the modifying of the third bearing assembly and the modifying of the third cutting structure occurs iteratively.

26. A method for determining a minimal moment center of a roller cone having a plurality of cutting elements comprising:

calculating the anticipated forces acting on each cutting element under a specified drilling condition at a selected time step;

projecting the forces acting on each cutting element into a cone coordinate system;

calculating the forces acting on each cone in the cone coordinate system;

simplifying the cone forces into a bearing coordinate system at a selected point located on bearing axis;

calculating the moments at that selected point and calculating the average moments;

calculating the vector sum of the moments at the selected point;

simplifying the cone forces into a bearing coordinate systems at a second selected point, calculating the moment at the second selected point and calculating the vector sum of the moments at the second selected point on the bearing axis;

plotting the moment as a function of the selected points along the bearing axis; and

determining the minimal moment position along the bearing axis according to the plotting.

27. A method of designing a bearing structure configuration for a roller cone comprising:

determining a minimal moment center for the bearing structure based in part upon an associated cutting structure;

designing an initial bearing structure configuration;

developing a mechanics model for the initial bearing configuration;

calculating the anticipated end loads on the bearing, with the help of finite element method ; and

adjusting the bearing configuration and recalculating the end loads on the bearing to substantially minimize the anticipated end load.

28. A method for designing a bearing structure configuration for a roller cone drill bit comprising:

designing an initial cutting structure of a cone assembly and determining the minimal moment center of the cone assembly;

designing a bearing structure configuration for rotatably mounting and calculating the anticipated end loads on the bearing structure; and

adjusting the cutting structure to minimize the end loads on the bearing.

29. A method of design bearing configuration for roller cone comprising:

designing an initial cutting structure of each cone and determining the minimal moment center;

designing an initial bearing configuration and calculating the end loads on the bearing; and

adjusting either the cutting structure and the bearing structure configuration to minimize the anticipated end loads acting of the bearing.