Dual-seal drill bit pressure communication system

A drill bit for use in a borehole comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone and between said bearing cavity and the borehole, said annular primary seal having a primarily dynamic sealing surface;
• an annular secondary seal disposed between said annular primary seal and the borehole, said annular secondary seal having a primarily dynamic sealing surface;
• wherein a first contact pressure occurs at said primarily dynamic sealing surface of said annular primary seal and a second contact pressure occurs at said primarily dynamic sealing surface of said annular secondary seal, said first contact pressure being greater than said second contact pressure;
• and
• an annular space disposed between said annular primary seal and said annular secondary seal, said annular space at least partially containing fluid and in substantially absolute fluid isolation from said bearing cavity.

A drill bit for use in a borehole at least partially containing drilling fluid, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone;
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole, said annular secondary seal having a primarily dynamic sealing surface and a primarily static sealing surface, wherein a first contact pressure occurs at said primarily dynamic sealing surface and a second contact pressure occurs at said primarily static sealing surface, said first contact pressure and said second contact pressure being unequal;
• and
• an annular space disposed between said annular primary seal and said annular secondary seal, said annular space at least partially containing fluid and in substantially absolute fluid isolation from said bearing cavity.

A drill bit for use in a borehole at least partially containing drilling fluid, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone;
• and
• an annular secondary seal disposed between said annular primary seal and the borehole and between said leg and said roller cone, wherein said annular secondary seal is engageable with said leg and said roller cone, said annular secondary seal including a sealing surface engageable with one of said bit components, wherein said sealing surface includes first and second regions;
• and
• wherein a first contact pressure occurs at said first region of said sealing surface and a second contact pressure occurs at said second region of said sealing surface, said first contact pressure being greater than said second contact pressure.

A drill bit for use in a borehole at least partially containing drilling fluid, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone;
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole;
• and
• an annular space formed between said annular primary seal and said annular secondary seal, said annular space at least partially containing fluid and in substantially absolute fluid isolation from said bearing cavity, said annular space having a chamber pressure, wherein said chamber pressure may be altered by allowing the passage of fluid from said annular space to the borehole and from the borehole to said annular space.

A drill bit for use in a borehole at least partially containing fluid and having a borehole pressure, comprising:

• a bit body having at least two bit components said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone;
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole;
• and
• an annular space formed between said annular primary seal and said annular secondary seal, said annular space having a chamber pressure and at least partially containing fluid, said annular space being in substantially absolute fluid isolation from said bearing cavity, wherein said fluid migrates from said annular space to the borehole when said chamber pressure is greater than the borehole pressure and wherein fluid migrates from the borehole to said annular space when the borehole pressure is greater than said chamber pressure.

A drill bit for use in a borehole at least partially containing fluid and having a borehole pressure, comprising:

• a bit body having at least two bit components said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone;
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole;
• and
• an annular space formed between said annular primary seal and said annular secondary seal, said annular space having a chamber pressure and at least partially containing fluid, said annular space being in substantially absolute fluid isolation from said bearing cavity, wherein said fluid migrates from said annular space to the borehole when said chamber pressure is greater than the borehole pressure.

A drill bit for use in a borehole at least partially containing drilling fluid, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone;
• and
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole, said annular secondary seal having a sealing surface engageable with at least one said bit component, said sealing surface having first and second adjacent regions, wherein the thickness of said annular secondary seal at said first region of said sealing surface is greater than the thickness of said annular secondary seal at said second region of said sealing surface.

A drill bit for use in a borehole at least partially containing drilling fluid, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone;
• and
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole, said annular secondary seal including at least one region having a tapered cross-section.

A drill bit for use in a borehole at least partially containing drilling fluid, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone;
• and
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole, said annular secondary seal including at least first and second circumferentially adjacent regions, a primarily static sealing surface and a primarily dynamic sealing surface, each of said first and second circumferentially adjacent regions having a height measured between said primarily static and primarily dynamic sealing surfaces,
• wherein at least one of said static and dynamic sealing surfaces is at least partially disposed on said first and second circumferentially adjacent regions, wherein the height of said first circumferentially adjacent region is greater than the height of said second circumferentially adjacent region.

A drill bit for use in a borehole, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components, further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween, wherein at least one of said bit components includes an annular groove having first and second circumferentially adjacent regions, wherein the width of said first circumferentially adjacent region is greater than the width of said second circumferentially adjacent region;
• an annular primary seal disposed between said leg and said roller cone;
• and
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole, wherein said annular secondary seal is disposed within said annular groove.

A drill bit for use in a borehole, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween, wherein said bit components include first and second primarily non-energizing seal engagement surfaces;
• an annular primary seal disposed between said leg and said roller cone;
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole, said annular secondary seal having first and second sides engageable with said first and second primarily non-energizing seal engagement surfaces of said bit components, respectively;
• and
• wherein at least one of said first and second primarily non-energizing seal engagement surfaces of said bit components includes first and second regions, said first region including at least one cut-out.

A drill bit for use in a borehole, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween, wherein said bit components include first and second primarily non-energizing seal engagement surfaces;
• an annular primary seal disposed between said leg and said roller cone;
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole, said annular secondary seal having first and second sides engageable with said first and second primarily non-energizing seal engagement surfaces of said bit components, respectively;
• and
• wherein at least one of said first and second primarily non-energizing seal engagement surfaces of said bit components includes first and second regions, said first region being uneven with respect to said second region.

A drill bit for use in a borehole, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween, wherein at least one of said bit components includes an annular groove;
• an annular primary seal disposed between said leg and said roller cone;
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole, said annular secondary seal having first and second sides and being disposed within said annular groove;
• and
• wherein said annular groove includes a first primarily non-energizing surface engageable with said first side of said annular secondary seal and a second primarily non-energizing surface engageable with said second side of said annular secondary seal, said first primarily non-energizing surface disposed between said second primarily non-energizing surface and said bearing cavity, further wherein said second primarily non-energizing surface includes at least first and second circumferentially adjacent regions, wherein said first region of said second primarily non-energizing surface includes at least one cut-out, whereby the distance from said first region of said second primarily non-energizing surface to said first primarily non-energizing surface is greater than the distance from said second region of said second primarily non-energizing surface to said first primarily non-energizing surface.

A drill bit for use in a borehole at least partially containing drilling fluid, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone;
• and
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole, said annular secondary seal having first and second circumferentially adjacent regions and a sealing surface extending at least partially upon said first and second circumferentially adjacent regions, wherein said sealing surface of said first circumferentially adjacent region is uneven with respect to said sealing surface of said second circumferentially adjacent region.

A drill bit for use in a borehole at least partially containing drilling fluid, comprising:

• a bit body having at least two bit components, a first said bit component including at least one leg, said leg having a journal segment, and a second said bit component including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone;
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole;
• and
• wherein each of said first and second bit components includes at least one component surface engageable with said annular secondary seal, at least one said component surface including first and second adjacent regions, wherein said first region of said component surface is uneven with respect to said second region of said component surface.

A drill bit for use in a borehole, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween, wherein at least one of said bit components includes an annular groove having at least first and second circumferentially adjacent regions, wherein the depth of said first circumferentially adjacent region is greater than the depth of said circumferentially adjacent second region;
• an annular primary seal disposed between said leg and said roller cone;
• and
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole, wherein said annular secondary seal is disposed within said annular groove.

A drill bit for use in a borehole, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular interstice formed between said bit components, said annular interstice having at least one seal engagement surface, said seal engagement surface having first and second circumferentially adjacent regions, wherein the depth of said first circumferentially adjacent region of said seal engagement surface is greater than the depth of said second circumferentially adjacent region;
• an annular primary seal disposed between said leg and said roller cone;
• and
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole, wherein said annular secondary seal is disposed within said annular interstice.

A drill bit for use in a borehole at least partially containing drilling fluid, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone;
• and
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole, said annular secondary seal including a primarily dynamic sealing surface and a primarily static sealing surface, each of said primarily dynamic and static sealing surfaces engageable with one of said bit components, wherein at least a portion of at least one of said primarily dynamic and static sealing surfaces includes a non-elastomeric porous inlay capable of at least partially allowing the passage of fluid past said annular secondary seal when said portion of at least one of said sealing surfaces is engaged with said bit component.

A drill bit for use in a borehole at least partially containing fluid and having a borehole pressure, comprising:

• a bit body having at least one leg, said leg including an exterior surface and a journal segment;
• a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone;
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole;
• an annular space disposed between said annular primary seal and said annular secondary seal, said annular space at least partially including fluid and being in substantially absolute fluid isolation from said bearing cavity;
• an opening in said exterior surface of said leg;
• and
• a passage disposed in said leg and extending from said opening to said annular space, said passage allowing fluid communication between said annular space and the borehole.

A drill bit for use in a borehole at least partially containing fluid and having a borehole pressure, comprising:

• a bit body having at least one leg, said leg including an exterior surface and a journal segment;
• a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone and forming a substantially absolute seal therebetween;
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole;
• an annular space disposed between said annular primary seal and said annular secondary seal, said annular space in substantially absolute fluid isolation from said bearing cavity;
• an opening in said exterior surface of said leg;
• a passage disposed in said leg and extending from said opening to said annular space, said passage being filled with incompressible fluid;
• and
• a plug disposed in said opening.

A drill bit for use in a borehole at least partially containing fluid, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween, wherein at least one of said bit components includes at least two seal engagement surfaces;
• an annular primary seal disposed between said leg and said roller cone;
• and
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole, said annular secondary seal including a primarily dynamic sealing surface and a primarily static sealing surface, each said sealing surface of said annular secondary seal having a width and being engageable at said width with one of said seal engagement surfaces of said bit components, at least one of said annular primarily dynamic and primarily static sealing surfaces including first and second regions, said width of said first region being smaller than said width of said second region.

A drill bit for use in a borehole at least partially containing fluid, comprising:

• a bit body having at least two bit components, said bit components including at least one leg, said leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone;
• and
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole, said annular secondary seal including at least one region having an at least partially non-symmetrical cross-section.

A drill bit for use in a borehole at least partially containing fluid, comprising:

• a bit body having at least two bit components, said bit components including at least one leg having a journal segment, said bit components further including a roller cone rotatably mounted upon said journal segment and forming at least one bearing cavity therebetween;
• an annular primary seal disposed between said leg and said roller cone;
• and
• an annular secondary seal disposed between said leg and said roller cone and between said annular primary seal and the borehole, said annular secondary seal having a primarily dynamic sealing surface and first and second side surfaces adjacent to said primarily dynamic sealing surface, wherein at least one of said bit components includes at least one non-energizing surface at least partially engageable with one of said first and second side surfaces of said annular secondary seal, at least one of said first and second side surfaces of said annular secondary seal and said non-energizing surface of said bit component including first and second sections, wherein said first section is uneven with respect to said second section.

A method for communicating fluid pressure between a borehole at least partially containing drilling fluid and the annular space formed between first and second annular seals in a dual-seal drill bit, the drill bit including a bit body having at least two bit components, the bit components including at least one leg having a journal segment, the bit components further including a roller cone rotatably mounted upon the journal segment and forming at least one bearing cavity therebetween, the first annular seal disposed between the leg and the roller cone, the second annular seal disposed between the leg and the roller cone and between the annular primary seal and the borehole, including:

• providing an absolute seal between the first annular seal and the bit components;
• fluidly isolating the annular space between the first and second annular seals from the bearing cavity;
• filling the annular space between the first and second annular seals with incompressible fluid;
• permitting the flow of incompressible fluid from the annular space to the borehole;
• and
• permitting the flow of drilling fluid from the borehole to the annular space.