Optimized earth boring seal means

• US 20030051921A1
• Filed: 09/03/2002
• Published: 03/20/2003
• Est. Priority Date: 08/31/2001
• Status: Active Grant

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Inventors: Miglierini, Raul A.
• Granted Patent: US 6,769,500 B2
• Time in Patent Office: Days
• US Class Current: 175/372
• CPC Class Codes: E21B 10/25 characterised by sealing details

Abstract

A rock bit seal in which the shape of the retainer lip (which restrains the seal from axial motion in response to pressure differentials) is optimized, with respect to the as-deformed shape of the seal in place, to achieve a preload stress which is everywhere nonzero. Preferably the ratio of maximum to minimum stress in the as-installed condition is kept to a small ratio, e.g. less than 2:1.

Claims

1. A rock bit sealing structure assembly comprising:

a spindle exterior surface and a cone interior surface defining seal compression surfaces therebetween;

a seal

positioned between said seal compression surfaces, and

deformed under stress from said surfaces, and

resting statically with respect to a first one of said surfaces while moving dynamically with respect to a second one of said surfaces; and

an extension of said second surface which confines said seal from motion along said second surface;

said extension having a profile which is complementary to the profile of said seal as deformed, and which provides a nonzero distributed preload stress to all portions of said seal in contact therewith, when standard lubricant-filling hydrostatic pressure is applied thereto;

whereby said seal is constrained by said extension against moving in response to hydraulic pressure differentials, but is not dragged along by friction with said extension during normal operation.

2. The sealing structure of claim 1, wherein said seal compression surfaces are substantially cylindrical.

3. The sealing structure of claim 1, wherein said seal is entirely elastomeric.

4. The sealing structure of claim 1, wherein said first surface is part of a cone, and said second surface is part of a spindle.

5. The sealing structure of claim 1, wherein said seal is homogeneous.

15. A bit for downhole rotary drilling, comprising:

a body having an internal passage for the delivery of drilling fluid, said body having an attachment portion capable of being attached to a drill string;

at least one cutting element rotatably supported, through a respective bearing, by a respective spindle which is supported by said body; and

at least one seal according to claim 1 which provides a dynamic seal between said cutting element and said spindle, to thereby exclude drilling mud from said bearing.

18. A method for rotary drilling, comprising the actions of:

applying torque and weight-on-bit to a drill string having a roller-cone-type bit thereon;

allowing cones of said bit to rotate on bearings which are mounted on spindles of said bit, to thereby extend a borehole; and

excluding debris from said bearings by using a seal according to claim 1.

21. A rotary drilling system, comprising:

a roller-cone-type bit mounted on a drill string, and having cutter cones rotatably mounted on bearings which are supported by spindles of said bit; and

machinery which applies torque and weight-on-bit to said drill string, to thereby extend a borehole;

wherein said bearings are protected by seals according to claim 1.

6. A sealing structure, comprising:

a spindle exterior surface and a cone interior surface defining seal compression surfaces therebetween;

a seal

positioned between said compression surfaces, and

deformed under stress from said surfaces, and

resting statically with respect to a first one of said surfaces while moving dynamically with respect to a second one of said surfaces; and

an extension of said second surface which confines said seal from motion along said second surface;

said extension having a profile which is complementary to the profile of said seal as deformed, and which provides a distributed preload stress to portions of said seal in contact therewith;

whereby said seal is constrained by said extension against moving in response to hydraulic pressure differentials, but is not dragged along by friction with said extension during normal operation.

7. The sealing structure of claim 6, wherein said seal compression surfaces are substantially cylindrical.

8. The sealing structure of claim 6, wherein said seal is entirely elastomeric.

9. The sealing structure of claim 6, wherein said seal is homogeneous.

16. A bit for downhole rotary drilling, comprising:

a body having an internal passage for the delivery of drilling fluid, said body having an attachment portion capable of being attached to a drill string;

at least one cutting element rotatably supported, through a respective bearing, by a respective spindle which is supported by said body; and

at least one seal according to claim 6 which provides a dynamic seal between said cutting element and said spindle, to thereby exclude drilling mud from said bearing.

19. A method for rotary drilling, comprising the actions of:

applying torque and weight-on-bit to a drill string having a roller-cone-type bit thereon;

allowing cones of said bit to rotate on bearings which are mounted on spindles of said bit, to thereby extend a borehole; and

excluding debris from said bearings by using a seal according to claim 6.

22. A rotary drilling system, comprising:

a roller-cone-type bit mounted on a drill string, and having cutter cones rotatably mounted on bearings which are supported by spindles of said bit; and

machinery which applies torque and weight-on-bit to said drill string, to thereby extend a borehole;

wherein said bearings are protected by seals according to claim 6.

10. A rotary sealing structure, comprising:

a seal positioned between and deformed under sealing stress from first and second seal compression surfaces, and resting statically with respect to said first surface while moving dynamically with respect to said second surface; and

an extension of said second surface which confines said seal from motion along said second surface;

said extension having a profile

which is complementary to the profile of said seal as deformed,

and which provides a distributed preload stress to portions of said seal in contact therewith, said preload stress

having a maximum intensity, outside the location of said sealing stress, which is less than half the peak value of said sealing stress, and

having a minimum intensity which is more than one-third of said maximum intensity;

whereby said seal is constrained by said extension against moving axially in response to hydrostatic pressure.

11. The sealing structure of claim 10, wherein said seal compression surfaces are substantially cylindrical.

12. The sealing structure of claim 10, wherein said seal is entirely elastomeric.

13. The sealing structure of claim 10, wherein said seal is homogeneous.

14. The sealing structure of claim 10, wherein said first surface is part of a rock bit'"'"'s cone, and said second surface is part of a spindle.

17. A bit for downhole rotary drilling, comprising:

a body having an internal passage for the delivery of drilling fluid, said body having an attachment portion capable of being attached to a drill string;

at least one cutting element rotatably supported, through a respective bearing, by a respective spindle which is supported by said body; and

at least one seal according to claim 10 which provides a dynamic seal between said cutting element and said spindle, to thereby exclude drilling mud from said bearing.

20. A method for rotary drilling, comprising the actions of:

applying torque and weight-on-bit to a drill string having a roller-cone-type bit thereon;

allowing cones of said bit to rotate on bearings which are mounted on spindles of said bit, to thereby extend a borehole; and

excluding debris from said bearings by using a seal according to claim 10.

23. A rotary drilling system, comprising:

a roller-cone-type bit mounted on a drill string, and having cutter cones rotatably mounted on bearings which are supported by spindles of said bit; and

machinery which applies torque and weight-on-bit to said drill string, to thereby extend a borehole;

wherein said bearings are protected by seals according to claim 10.

24. A method of designing a bit for rotary drilling, comprising the actions of:

simulating the as-deformed shape of a seal element under a sealing stress between a static and a dynamic sealing surface; and

optimizing the contour of an extension of said dynamic sealing surface to provide a distributed preload stress, under an applied hydrostatic preload pressure, which is everywhere nonzero but less than said sealing stress.