CA2068608A1 - A downhole bearing assembly - Google Patents
A downhole bearing assemblyInfo
- Publication number
- CA2068608A1 CA2068608A1 CA 2068608 CA2068608A CA2068608A1 CA 2068608 A1 CA2068608 A1 CA 2068608A1 CA 2068608 CA2068608 CA 2068608 CA 2068608 A CA2068608 A CA 2068608A CA 2068608 A1 CA2068608 A1 CA 2068608A1
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- Prior art keywords
- pair
- shoulders
- annular
- tubular member
- bearing
- Prior art date
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Abstract
ABSTRACT OF THE DISCLOSURE
An improvement in bearing configuration for taking axial loading in both directions in a bearing assembly having a first tubular member telescopically received within a second tubular member. The bearing configuration consists of a single thrust bearing assembly having a single thrust bearing positioned between a first annular member and a second annular member.
The annular members are rotatably mounted on the first tubular member. The thrust bearing assembly is positioned between a first pair of shoulders adjacent the first annular member and a second pair of shoulders adjacent the second annular member.
Each pair of shoulders have an inner annular shoulder on the first tubular member and an outer annular shoulder on the second tubular member. Axial loading in compression is transmitted by the outer annular shoulder of the second pair of shoulders to the second annular member, to the thrust bearing, to the first annular member and to the inner annular shoulder of the first pair of shoulders. Axial loading in tension is transmitted by the outer annular shoulder of the first pair of shoulders to the first annular member, to the thrust bearing, to the second annular member and to the inner annular shoulder of the second pair of shoulders.
An improvement in bearing configuration for taking axial loading in both directions in a bearing assembly having a first tubular member telescopically received within a second tubular member. The bearing configuration consists of a single thrust bearing assembly having a single thrust bearing positioned between a first annular member and a second annular member.
The annular members are rotatably mounted on the first tubular member. The thrust bearing assembly is positioned between a first pair of shoulders adjacent the first annular member and a second pair of shoulders adjacent the second annular member.
Each pair of shoulders have an inner annular shoulder on the first tubular member and an outer annular shoulder on the second tubular member. Axial loading in compression is transmitted by the outer annular shoulder of the second pair of shoulders to the second annular member, to the thrust bearing, to the first annular member and to the inner annular shoulder of the first pair of shoulders. Axial loading in tension is transmitted by the outer annular shoulder of the first pair of shoulders to the first annular member, to the thrust bearing, to the second annular member and to the inner annular shoulder of the second pair of shoulders.
Description
20~86~
The present invention relates to a downhole bearing a~sembly.
S BF~CK~ROUND OF THE INVENTION
Downhole drilling motor~ are being used with increaRing frequency when drilling oil or gas wells. The type of downhole motor~ used are generally fluid driven with a rotor which moves in an eccentric fa~hion. The downhole motor is connected to a concentrically rotating bearing assembly by a universal joint coupling. The concentrically rotating bearing assembly is, in turn, connected to the drill bit. The universal joint coupling extend~ through a housing which is generally referred to as a "bent" housing for it usually has an angular offset or "bend"
which causes the borehole being drilled to deviate at an angle.
This is known as ~directional drilling~, for the downhole motor is steered at an angle toward an oil or gas bearing formation and in some cases horizontally across the formation to increase the area of the borehole traversing the potential oil or gas producing zone. The length of the downhole motor and its a#sociated components effects the rate at which the downhole motor can be made to "build angle", moving from vertical to, in some cases, substantially horizontal. It haæ long been recognized in the art that it is desirable to have the length of the downhole motor and its associated components as short as possible; particularly the length from the drill bit to the bend in the housing for the universal joint coupling.
The length from the drill bit to the bend in the housing of a typical downhole sealed bearing assembly at the present time is approximately eight feet. If this length could be significantly reduced it would represent a major advance in the art. The leeway for design changes is somewhat limited.
Sealed bearing assemblies must have bearings to take axial loading in both directions and radial loading and seals to prevent abrasive drilling fluids from limiting the useful life of the bearings.
2068~08 What is required is downhole bearing assembly which is shorter in length.
According to the present invention there i8 provided an improvement in a downhole bearing assembly. Downhole bearing a~semblies generally consist of a first tubular member telescopically received and rotatably mounted within a second tubular member. The first tubular member has a first end adapted for connection to a drill bit. The second tubular member has a second end adapted for connection to a bent housing and by means of a universal joint coupling to a drilling motor. An annular fluid flow passage extends through the first tubular member and the second tubular member whereby drilling fluids flow from the second end to the first end. A
sealed bearing chamber is disposed between the first tubular member and the second tubular member having bearing means taking axial loading in both directions and radial loading.
The improvement relates to the bearing means taking axial loading in both directions. The bearing mean~ consists of a single thrust bearing assembly having a single thrust bearing positioned between a first annular member and a second annular member. The annular members are rotatably mounted on the first tubular member. The thrust bearing assembly is positioned between a first pair of shoulders adjacent the irst annular member and a second pair of shoulders adjacent the second annular member. Each pair of shoulders have an inner annular shoulder on the first tubular member and an outer annular shoulder on the second tubular member. Axial loading in compression is transmitted by the outer annular shoulder o~ the second pair of shoulders to the second annular member, to the thrust bearing, to the first annular member and to the inner annular shoulder of the first pair of shoulders. Axial loading in tension is transmitted by the outer annular shoulder of the first pair of shoulders to the first annular member, to the thrust bearing, to the second annular member and to the inner annular shoulder of the second pair of shoulders.
20686~8 In order to take advantage of the environment in which the bearing assembly operates to further shorten the tool, it is preferred that the inner annular shoulder of the second pair of shoulders be provided by a connection with the universal joint coupling. By using one bearing to handle axial loading in both direction~, that i8 in tension and compression, the bearing assembly as described allows shorter tools to be con~tructed.
Although beneficial results may be obtained through the use of the bearing assembly as described, it is preferred that th0 primary seal used to seal the bearing assembly adjacent the first end be a mechanical seal. It is well known in the art that mechanical seals can withstand higher pressures than can elastomer seals when used as rotary shaft seals. In view of extreme radial loads encountered in directional drilling, the point of mounting of the mechanical seal on the output shaft of the bearing assembly should be as close to the bearing as possible to keep radial run out to a minimum. This helps ensure that the mechanical seal faces will remain engaged. There are practical design limitations as to how close a seal, especially a mechanical seal, can be positioned to a bearing to keep radial run out to a minimum. Even more beneficial result~ can therefore be obtained by having the bearing means taking radial loading being a bushing disposed in the bearing chamber. The bushing has a small cross-section, allowing the mechanical seal to be positioned close to the end of the bushing.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will become more apparent from the following description in which reference i~
made to the appended drawings, wherein:
FIGURE8 lA and lB are longitudinal section views of a bearing assembly constructed in accordance with the teaching~
of the present invention.
DE'TAILED DESCRIPTION OF T~E PREFERRED EMBODIMENT
The preferred embodiment, a downhole bearing assembly generally identified by reference numeral 10, will now be de~cribed with reference to FIGURE8 lA and lB.
The invention represents an improvement in a downhole bearing assembly. The environment into which the impxovement is incorporated consists of a ~irst tubular member 12 telescopically received and rotatably mounted within a second tubular member 14. For ease of assembly second tubular member 14 consiæts of three components 14a, 14b, and 14c. The telescopically conjoined tubular members 12 and 14 have a drill bit end 16 adapted for connection to a drill bit (not shown) and a motor end 18 adapted for connection to a bent housing 20 and by means of a universal joint coupling 22 to a drilling motor (not shown). An annular fluid flow passage 24 extends through the telescopically conjoined tubular members 12 and 14, whereby drilling fluids flow from motor end 18 to drill bit end 16. A sealed bearing chamber 26 is disposed between first tubular member 12 and second tubular member 14. Bearing chamber 26 houses bearings which must be capable of taking axial loading in both directions and radial loading.
The sealing configuration which will hereinafter be described is the subject of a concurrently filed copending patent applications. In order to provide a complete description of construction and operation the sealing configuration of bearing assembly 10 will now be described.
Bearing chamber 26 is sealed adjacent drill bit end 16 by means of a mechanical seal, generally identified by reference numeral 28. Mechanical seal 28 consists of a first ~eal ring 30 non-rotatably secured by means of pins 32 to first tubular member 12 and a second seal ring 34 non-rotatably secured by means of pins 36 to second tubular member 14. Seal rings 30 and 34 are capable of limited axial movement. Biasing means in the form of a plurality of springs 38 urge first seal ring 30 and second seal ring 34 together in face to face engagement to form a 20~8608 mechanical seal. As the portion of seal rings 30 and 34 which are in engagement must be specially treated, seal rings 30 and 34 as illustrated each consist of two portions; carrier portions 30a and 34a, and engaging portions 30b and 34b. A
lubricant reservoir 40 is positioned at drill bit end 16 of telescopically conjoined tubular members 12 and 1~. Lubricant reservoir 40 has a drill bit end 42 and a motor end 44. A
pa~sage 45 is positioned adjacent motor end 44 of lubricant reservoir 40 which communicates with bearing chamber 26. A
floating piston 46 is positioned in lubricant reservoir 40.
Floating piston 46 has one face 48 communicating with drilling fluids in annular fluid flow passage 24, and a second ~ace 50 communicating with lubricant in lubricant reservoir 40.
Floating piston 46 moves to increase the pressure upon lubricants within lubricant reservoir 40, and consequently within bearing chamber 26, in response to the flow of drilling fluids through annular fluid flow passage 24. Bearing chamber 26 adjacent motor end 18 is sealed by an elastomer seal 52.
Positioned adjacent seal 52 is a sealing chamber 85. A
floating seal 56 is disposed in sealing chamber 85. Seal 56 is biased by spring 54. There iB a pressure loss in the drilling fluid caused by the changing of direction of the fluid flow from portion 24A of fluid flow passage 24 to portion 24B.
The biasing of elastomer seal 56 by spring 54 places lubricants within sealing chamber 85 under a pressure greater than the pressure in passage 24, thus ensuring that seal 52 will receive lubrication from chamber 85. A shoulder 87 is formed by a narrowing between seal 52 and chamber 85. Chamber 85 is filled with lubricant through passage 89 via fill plug 88.
The improvement in the bearing assembly will now be described as it relates to the bearing means taking axial loading in both directions. The bearing means consists of a single thrust bearing assembly generally identified by reference numeral 60. Thrust bearing assembly 60 has a single thrust bearing 62 positioned between a first annular member 6~
and a second annular member 66. Annular members 64 and 66 are 20~86Q8 rotatably mounted on first tubular member 12 by means of teflon and lead coated bushings 68. Thrust bearing assembly 60 is positioned between a first pair of shoulders 70 and 72 adjacent fir~t annular member 64 and a second pair of shoulders 74 and 76 adjacent second annular member 66. Each pair of shoulders have an inner annular shoulder (70, 74) on first tubular member 12 and an outer annular shoulder (72, 76) on second tubular member 14. In order to further reduce the length of bearing assembly 10, inner annular shoulder 74 of the second pair of shoulders is provided by a connection 75 with universal joint coupling 22. The bearing means taking radial loading is a teflon lead coated bushing 78 disposed in bearing chamber 26.
There a number of minor features illustrated in FI~URE lA, which will now be described. ~IO~ ring seals 58 are positioned where various components join to prevent leakage. A retaining ring 80 ~ecured in place by a ~nap ring 82 i8 ~ecured to first tubular member 12 to prevent first tubular member 12 from being lost downhole should tubular member 12 break at connection 75.
Lubricant ports 84 are provided to permit lubricant to be pumped into lubricant reservoir 40 and bearing chamber 26 during assembly of bearing assembly 10. A seal between seal ring 30 and first tubular member 12 is maintained by "O" ring seal 90. "O" ring seal 90 engages seal surface 86. A seal between seal ring 34 and second tubular member 14 is maintained by "O" ring seal 91.
The use and operation of bearing assembly 10 will now be describ0d with reference to FIGURES lA and lB. When bearing assembly 10 is in use first tubular member 12 rotates within second tubular member 14 with the rotation being facilitate by and radial loading borne by teflon and lead coated bushing 78.
Axial loading in both compression and tension is borne by thrust bearing assembly 60. Axial loading in compression is transmitted by outer annular shoulder 76 of the second pair of shoulders to second annular member 66, to thrust bearing 62, to first annular member 64 and to inner annular shoulder 70 of 2~S86~8 the first pair of shoulders. Axial loading in tension is transmitted by outer annular shoulder 72 of the first pair of shoulders to first annular member 64, to thrust bearing 62, to second annular member 66 and to inner annular shoulder 74 of the 6econd pair of shoulders. This permits a single thrust bearing (thrust bearing 62) to be used, whereas previously a m:inimum of two were required. Thrust bearings 62 and teflon and lead coated bushings 78 and 68 would not function effectively for very long if exposed to abrasive drilling fluids. For this reason thrust bearing 62 and teflon and lead coated bushings 78 and 68 are positioned in sealed bearing chamber 26. Bearing chamber 26 is sealed adjacent drill bit end 16 by mechanical seal 28, and adjacent motor end 18 by elastomer seals 52 and 56. Seal rings 30 and 34 are bia3ed together by springs 38. Springs 38 control the amount of force with which seal rings 30 and 34 are forced into engagement and also perform a secondary function of permitting a limited accommodation for eccentric "run out". In order to function properly a thin film of lubricant must be maintained between engaging portions 30b and 34b of seal rings 30 and 34. In order to ensure lubricant is maintained between engaging portions 30b and 34b, a minute leakage of lubricant is permitted between engaging portions 30b and 34b which serve as the seal faces of mechanical seal 28. This ensures there will not be any incursion of abrasive drilling fluids between the engaging portions 30b and 34b. The lubricant in bearing chamber 26 is under a greater pressure than the drilling fluid external the tool, when surface pumps are running, by an amount equal to the pressure drop across the nozzle in the drill bit. This can also be expressed in terms of the difference between the pressure in passage 24 at bit end 16 and the hydrostatic pressure external of the tool. Therefore, there is always a pressure drop across engaging portions 30b and 34b of mechanical seal 28. A lubricant film is maintained between the seal faces while limiting the leakage by designing the proper relationship between the diameter of engaging portions 30b and 34b, width o~ seal faces 30b and 34b, seal surface diameters 2~ 6~8 86 and the biasing force of springs 38. The biasing of portions 30a and 34a of mechanical seal 28 between springs 38 allows for more eccentric run out than conventional mechanical seals which are only bia~ed in one direction. Biasing in both directions iB alco superior when axial shock loading or vibration occurs. There is less chance of engaging portions 30b and 34b separating causing lubricant loss. Lubricant reservoir 40 provides the additional supply of lubricant necessary to ensure that the supply of lubricant in bearing chamber 26 is not exhausted as a result of slow leakage through mechanical seal 28. As previously mentioned, the positioning of lubricant chamber 40 at drill bit end 16 connected with bearing chamber 26 by passage 45 is an innovation which permits bearing assembly 10 to be shortened. The area at drill bit end 16 of bearing assembly 10 where lubricant chamber 40 i8 now located e~ists on similar tools but is not used. Oil chambers have all been located at motor end 18 of other bearing assemblie~, adding to the length at motor end 18 of the tools which the length at drill bit end 16 remained the same. When surface pumps are used to pump drilling fluids through annular fluid flow passage 24, floating piston 46 moves to increase the pressure upon lubricants within lubricant reservoir 40, and consequently within bearing ch~her 26. Pressure is exerted upon first face 48 of floating piston 46 by drilling fluids in annular fluid flow passage 24. In response to this pressure floating piston 46 moves until an equal pressure i8 exerted upon second face 50 by lubricant in lubricant reservoir 40.
Seal 52 is between and adjacent lubricant chambers 26 and 85.
If this seal was eliminated seal 56 would be forced downward to æhoulder 87 even without biasing spring 54; since drilling fluid at motor end 18 of bearing assembly 10 in passage 24a is at a greater pressure then drilling fluid adjacent piston 46.
This would cause seal 56, without seal 52, to move down to shoulder 87, forcing piston 46 to move downward. In this situation, the drilling fluid adjacent seal 56 would be under greater pressure than the lubricant in bearing chamber 26.
This would shorten the life of seal 56. For the same reason, ~068~8 seal 52 would have a shortened life if seal 56 was eliminated.
If seal 52 and seal 56 were used without biasing spring 54, lubricant pressure in chamber 85 is equal to drilling fluid pressure adjacent seal 56. This is preferred over having negative pressure, but the preferred method is to use biasing spring S4, which puts lubricant adjacent seal 56 under positive pressure.
It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as defined by the claims.
The present invention relates to a downhole bearing a~sembly.
S BF~CK~ROUND OF THE INVENTION
Downhole drilling motor~ are being used with increaRing frequency when drilling oil or gas wells. The type of downhole motor~ used are generally fluid driven with a rotor which moves in an eccentric fa~hion. The downhole motor is connected to a concentrically rotating bearing assembly by a universal joint coupling. The concentrically rotating bearing assembly is, in turn, connected to the drill bit. The universal joint coupling extend~ through a housing which is generally referred to as a "bent" housing for it usually has an angular offset or "bend"
which causes the borehole being drilled to deviate at an angle.
This is known as ~directional drilling~, for the downhole motor is steered at an angle toward an oil or gas bearing formation and in some cases horizontally across the formation to increase the area of the borehole traversing the potential oil or gas producing zone. The length of the downhole motor and its a#sociated components effects the rate at which the downhole motor can be made to "build angle", moving from vertical to, in some cases, substantially horizontal. It haæ long been recognized in the art that it is desirable to have the length of the downhole motor and its associated components as short as possible; particularly the length from the drill bit to the bend in the housing for the universal joint coupling.
The length from the drill bit to the bend in the housing of a typical downhole sealed bearing assembly at the present time is approximately eight feet. If this length could be significantly reduced it would represent a major advance in the art. The leeway for design changes is somewhat limited.
Sealed bearing assemblies must have bearings to take axial loading in both directions and radial loading and seals to prevent abrasive drilling fluids from limiting the useful life of the bearings.
2068~08 What is required is downhole bearing assembly which is shorter in length.
According to the present invention there i8 provided an improvement in a downhole bearing assembly. Downhole bearing a~semblies generally consist of a first tubular member telescopically received and rotatably mounted within a second tubular member. The first tubular member has a first end adapted for connection to a drill bit. The second tubular member has a second end adapted for connection to a bent housing and by means of a universal joint coupling to a drilling motor. An annular fluid flow passage extends through the first tubular member and the second tubular member whereby drilling fluids flow from the second end to the first end. A
sealed bearing chamber is disposed between the first tubular member and the second tubular member having bearing means taking axial loading in both directions and radial loading.
The improvement relates to the bearing means taking axial loading in both directions. The bearing mean~ consists of a single thrust bearing assembly having a single thrust bearing positioned between a first annular member and a second annular member. The annular members are rotatably mounted on the first tubular member. The thrust bearing assembly is positioned between a first pair of shoulders adjacent the irst annular member and a second pair of shoulders adjacent the second annular member. Each pair of shoulders have an inner annular shoulder on the first tubular member and an outer annular shoulder on the second tubular member. Axial loading in compression is transmitted by the outer annular shoulder o~ the second pair of shoulders to the second annular member, to the thrust bearing, to the first annular member and to the inner annular shoulder of the first pair of shoulders. Axial loading in tension is transmitted by the outer annular shoulder of the first pair of shoulders to the first annular member, to the thrust bearing, to the second annular member and to the inner annular shoulder of the second pair of shoulders.
20686~8 In order to take advantage of the environment in which the bearing assembly operates to further shorten the tool, it is preferred that the inner annular shoulder of the second pair of shoulders be provided by a connection with the universal joint coupling. By using one bearing to handle axial loading in both direction~, that i8 in tension and compression, the bearing assembly as described allows shorter tools to be con~tructed.
Although beneficial results may be obtained through the use of the bearing assembly as described, it is preferred that th0 primary seal used to seal the bearing assembly adjacent the first end be a mechanical seal. It is well known in the art that mechanical seals can withstand higher pressures than can elastomer seals when used as rotary shaft seals. In view of extreme radial loads encountered in directional drilling, the point of mounting of the mechanical seal on the output shaft of the bearing assembly should be as close to the bearing as possible to keep radial run out to a minimum. This helps ensure that the mechanical seal faces will remain engaged. There are practical design limitations as to how close a seal, especially a mechanical seal, can be positioned to a bearing to keep radial run out to a minimum. Even more beneficial result~ can therefore be obtained by having the bearing means taking radial loading being a bushing disposed in the bearing chamber. The bushing has a small cross-section, allowing the mechanical seal to be positioned close to the end of the bushing.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will become more apparent from the following description in which reference i~
made to the appended drawings, wherein:
FIGURE8 lA and lB are longitudinal section views of a bearing assembly constructed in accordance with the teaching~
of the present invention.
DE'TAILED DESCRIPTION OF T~E PREFERRED EMBODIMENT
The preferred embodiment, a downhole bearing assembly generally identified by reference numeral 10, will now be de~cribed with reference to FIGURE8 lA and lB.
The invention represents an improvement in a downhole bearing assembly. The environment into which the impxovement is incorporated consists of a ~irst tubular member 12 telescopically received and rotatably mounted within a second tubular member 14. For ease of assembly second tubular member 14 consiæts of three components 14a, 14b, and 14c. The telescopically conjoined tubular members 12 and 14 have a drill bit end 16 adapted for connection to a drill bit (not shown) and a motor end 18 adapted for connection to a bent housing 20 and by means of a universal joint coupling 22 to a drilling motor (not shown). An annular fluid flow passage 24 extends through the telescopically conjoined tubular members 12 and 14, whereby drilling fluids flow from motor end 18 to drill bit end 16. A sealed bearing chamber 26 is disposed between first tubular member 12 and second tubular member 14. Bearing chamber 26 houses bearings which must be capable of taking axial loading in both directions and radial loading.
The sealing configuration which will hereinafter be described is the subject of a concurrently filed copending patent applications. In order to provide a complete description of construction and operation the sealing configuration of bearing assembly 10 will now be described.
Bearing chamber 26 is sealed adjacent drill bit end 16 by means of a mechanical seal, generally identified by reference numeral 28. Mechanical seal 28 consists of a first ~eal ring 30 non-rotatably secured by means of pins 32 to first tubular member 12 and a second seal ring 34 non-rotatably secured by means of pins 36 to second tubular member 14. Seal rings 30 and 34 are capable of limited axial movement. Biasing means in the form of a plurality of springs 38 urge first seal ring 30 and second seal ring 34 together in face to face engagement to form a 20~8608 mechanical seal. As the portion of seal rings 30 and 34 which are in engagement must be specially treated, seal rings 30 and 34 as illustrated each consist of two portions; carrier portions 30a and 34a, and engaging portions 30b and 34b. A
lubricant reservoir 40 is positioned at drill bit end 16 of telescopically conjoined tubular members 12 and 1~. Lubricant reservoir 40 has a drill bit end 42 and a motor end 44. A
pa~sage 45 is positioned adjacent motor end 44 of lubricant reservoir 40 which communicates with bearing chamber 26. A
floating piston 46 is positioned in lubricant reservoir 40.
Floating piston 46 has one face 48 communicating with drilling fluids in annular fluid flow passage 24, and a second ~ace 50 communicating with lubricant in lubricant reservoir 40.
Floating piston 46 moves to increase the pressure upon lubricants within lubricant reservoir 40, and consequently within bearing chamber 26, in response to the flow of drilling fluids through annular fluid flow passage 24. Bearing chamber 26 adjacent motor end 18 is sealed by an elastomer seal 52.
Positioned adjacent seal 52 is a sealing chamber 85. A
floating seal 56 is disposed in sealing chamber 85. Seal 56 is biased by spring 54. There iB a pressure loss in the drilling fluid caused by the changing of direction of the fluid flow from portion 24A of fluid flow passage 24 to portion 24B.
The biasing of elastomer seal 56 by spring 54 places lubricants within sealing chamber 85 under a pressure greater than the pressure in passage 24, thus ensuring that seal 52 will receive lubrication from chamber 85. A shoulder 87 is formed by a narrowing between seal 52 and chamber 85. Chamber 85 is filled with lubricant through passage 89 via fill plug 88.
The improvement in the bearing assembly will now be described as it relates to the bearing means taking axial loading in both directions. The bearing means consists of a single thrust bearing assembly generally identified by reference numeral 60. Thrust bearing assembly 60 has a single thrust bearing 62 positioned between a first annular member 6~
and a second annular member 66. Annular members 64 and 66 are 20~86Q8 rotatably mounted on first tubular member 12 by means of teflon and lead coated bushings 68. Thrust bearing assembly 60 is positioned between a first pair of shoulders 70 and 72 adjacent fir~t annular member 64 and a second pair of shoulders 74 and 76 adjacent second annular member 66. Each pair of shoulders have an inner annular shoulder (70, 74) on first tubular member 12 and an outer annular shoulder (72, 76) on second tubular member 14. In order to further reduce the length of bearing assembly 10, inner annular shoulder 74 of the second pair of shoulders is provided by a connection 75 with universal joint coupling 22. The bearing means taking radial loading is a teflon lead coated bushing 78 disposed in bearing chamber 26.
There a number of minor features illustrated in FI~URE lA, which will now be described. ~IO~ ring seals 58 are positioned where various components join to prevent leakage. A retaining ring 80 ~ecured in place by a ~nap ring 82 i8 ~ecured to first tubular member 12 to prevent first tubular member 12 from being lost downhole should tubular member 12 break at connection 75.
Lubricant ports 84 are provided to permit lubricant to be pumped into lubricant reservoir 40 and bearing chamber 26 during assembly of bearing assembly 10. A seal between seal ring 30 and first tubular member 12 is maintained by "O" ring seal 90. "O" ring seal 90 engages seal surface 86. A seal between seal ring 34 and second tubular member 14 is maintained by "O" ring seal 91.
The use and operation of bearing assembly 10 will now be describ0d with reference to FIGURES lA and lB. When bearing assembly 10 is in use first tubular member 12 rotates within second tubular member 14 with the rotation being facilitate by and radial loading borne by teflon and lead coated bushing 78.
Axial loading in both compression and tension is borne by thrust bearing assembly 60. Axial loading in compression is transmitted by outer annular shoulder 76 of the second pair of shoulders to second annular member 66, to thrust bearing 62, to first annular member 64 and to inner annular shoulder 70 of 2~S86~8 the first pair of shoulders. Axial loading in tension is transmitted by outer annular shoulder 72 of the first pair of shoulders to first annular member 64, to thrust bearing 62, to second annular member 66 and to inner annular shoulder 74 of the 6econd pair of shoulders. This permits a single thrust bearing (thrust bearing 62) to be used, whereas previously a m:inimum of two were required. Thrust bearings 62 and teflon and lead coated bushings 78 and 68 would not function effectively for very long if exposed to abrasive drilling fluids. For this reason thrust bearing 62 and teflon and lead coated bushings 78 and 68 are positioned in sealed bearing chamber 26. Bearing chamber 26 is sealed adjacent drill bit end 16 by mechanical seal 28, and adjacent motor end 18 by elastomer seals 52 and 56. Seal rings 30 and 34 are bia3ed together by springs 38. Springs 38 control the amount of force with which seal rings 30 and 34 are forced into engagement and also perform a secondary function of permitting a limited accommodation for eccentric "run out". In order to function properly a thin film of lubricant must be maintained between engaging portions 30b and 34b of seal rings 30 and 34. In order to ensure lubricant is maintained between engaging portions 30b and 34b, a minute leakage of lubricant is permitted between engaging portions 30b and 34b which serve as the seal faces of mechanical seal 28. This ensures there will not be any incursion of abrasive drilling fluids between the engaging portions 30b and 34b. The lubricant in bearing chamber 26 is under a greater pressure than the drilling fluid external the tool, when surface pumps are running, by an amount equal to the pressure drop across the nozzle in the drill bit. This can also be expressed in terms of the difference between the pressure in passage 24 at bit end 16 and the hydrostatic pressure external of the tool. Therefore, there is always a pressure drop across engaging portions 30b and 34b of mechanical seal 28. A lubricant film is maintained between the seal faces while limiting the leakage by designing the proper relationship between the diameter of engaging portions 30b and 34b, width o~ seal faces 30b and 34b, seal surface diameters 2~ 6~8 86 and the biasing force of springs 38. The biasing of portions 30a and 34a of mechanical seal 28 between springs 38 allows for more eccentric run out than conventional mechanical seals which are only bia~ed in one direction. Biasing in both directions iB alco superior when axial shock loading or vibration occurs. There is less chance of engaging portions 30b and 34b separating causing lubricant loss. Lubricant reservoir 40 provides the additional supply of lubricant necessary to ensure that the supply of lubricant in bearing chamber 26 is not exhausted as a result of slow leakage through mechanical seal 28. As previously mentioned, the positioning of lubricant chamber 40 at drill bit end 16 connected with bearing chamber 26 by passage 45 is an innovation which permits bearing assembly 10 to be shortened. The area at drill bit end 16 of bearing assembly 10 where lubricant chamber 40 i8 now located e~ists on similar tools but is not used. Oil chambers have all been located at motor end 18 of other bearing assemblie~, adding to the length at motor end 18 of the tools which the length at drill bit end 16 remained the same. When surface pumps are used to pump drilling fluids through annular fluid flow passage 24, floating piston 46 moves to increase the pressure upon lubricants within lubricant reservoir 40, and consequently within bearing ch~her 26. Pressure is exerted upon first face 48 of floating piston 46 by drilling fluids in annular fluid flow passage 24. In response to this pressure floating piston 46 moves until an equal pressure i8 exerted upon second face 50 by lubricant in lubricant reservoir 40.
Seal 52 is between and adjacent lubricant chambers 26 and 85.
If this seal was eliminated seal 56 would be forced downward to æhoulder 87 even without biasing spring 54; since drilling fluid at motor end 18 of bearing assembly 10 in passage 24a is at a greater pressure then drilling fluid adjacent piston 46.
This would cause seal 56, without seal 52, to move down to shoulder 87, forcing piston 46 to move downward. In this situation, the drilling fluid adjacent seal 56 would be under greater pressure than the lubricant in bearing chamber 26.
This would shorten the life of seal 56. For the same reason, ~068~8 seal 52 would have a shortened life if seal 56 was eliminated.
If seal 52 and seal 56 were used without biasing spring 54, lubricant pressure in chamber 85 is equal to drilling fluid pressure adjacent seal 56. This is preferred over having negative pressure, but the preferred method is to use biasing spring S4, which puts lubricant adjacent seal 56 under positive pressure.
It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as defined by the claims.
Claims (3)
1. An improvement in a downhole bearing assembly consisting of a first tubular member telescopically received and rotatably mounted within a second tubular member, the telescopically conjoined tubular members having a drill bit end adapted for connection to a drill bit and a motor end adapted for connection to a bent housing and by means of a universal joint coupling to a drilling motor, an annular fluid flow passage extends through the telescopically conjoined tubular members whereby drilling fluids flow from the motor end to the drill bit end, a sealed bearing chamber being disposed between the first tubular member and the second tubular member, the bearing chamber housing bearing means taking axial loading in both directions and radial loading, the improvement comprising:
the bearing means taking axial loading in both directions being a single thrust bearing assembly consisting of a single thrust bearing positioned between a first annular member and a second annular member, the annular members being rotatably mounted on the first tubular member, the thrust bearing assembly being positioned between a first pair of shoulders adjacent the first annular member and a second pair of shoulders adjacent the second annular member, each pair of shoulders having an inner annular shoulder on the first tubular member and an outer annular shoulder on the second tubular member, such that axial loading in compression is transmitted by outer annular shoulder of the second pair of shoulders to the second annular member, to the thrust bearing, to the first annular member and to the inner annular shoulder of the first pair of shoulders, and axial loading in tension is transmitted by the outer annular shoulder of the first pair of shoulders to the first annular member, to the thrust bearing, to the second annular member and to the inner annular shoulder of the second pair of shoulders.
the bearing means taking axial loading in both directions being a single thrust bearing assembly consisting of a single thrust bearing positioned between a first annular member and a second annular member, the annular members being rotatably mounted on the first tubular member, the thrust bearing assembly being positioned between a first pair of shoulders adjacent the first annular member and a second pair of shoulders adjacent the second annular member, each pair of shoulders having an inner annular shoulder on the first tubular member and an outer annular shoulder on the second tubular member, such that axial loading in compression is transmitted by outer annular shoulder of the second pair of shoulders to the second annular member, to the thrust bearing, to the first annular member and to the inner annular shoulder of the first pair of shoulders, and axial loading in tension is transmitted by the outer annular shoulder of the first pair of shoulders to the first annular member, to the thrust bearing, to the second annular member and to the inner annular shoulder of the second pair of shoulders.
2. The Improvement as defined in Claim 1, the inner annular shoulder of the second pair of shoulders being provided by a connection with the universal joint coupling.
3. The improvement as defined in Claim 1, the bearing means taking radial loading being a bushing disposed in the bearing chamber.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2068608 CA2068608A1 (en) | 1992-05-13 | 1992-05-13 | A downhole bearing assembly |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2068608 CA2068608A1 (en) | 1992-05-13 | 1992-05-13 | A downhole bearing assembly |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2068608A1 true CA2068608A1 (en) | 1993-11-14 |
Family
ID=4149833
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2068608 Abandoned CA2068608A1 (en) | 1992-05-13 | 1992-05-13 | A downhole bearing assembly |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2068608A1 (en) |
-
1992
- 1992-05-13 CA CA 2068608 patent/CA2068608A1/en not_active Abandoned
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |