Pressure Compensated Rotating Electrical Contact

Abstract

A technique facilitates communication of electrical signals in harsh environments and between components that undergo relative rotation with respect to each other. The technique comprises rotatably mounting a first component with respect to a second component. The first component also is electrically coupled with the second component via an electrical coupler. The electrical coupler may comprise a first electrical contact located at the first component and a second electrical contact located at the second component. The first electrical contact is conductively connected with the second electrical contact via a conductive bearing. The conductive bearing is located in a volume which is filled with a substantially incompressible fluid to protect the bearing.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present document is based on and claims priority to U.S. Provisional Application Ser. No.: 62/014,086, filed Jun. 18, 2014, which is incorporated herein by reference in its entirety.

BACKGROUND

In many hydrocarbon well applications, a wellbore is formed in a hydrocarbon-bearing formation and a well string is deployed in the wellbore. The well string is formed with tubing and other types of downhole components, some of which are electrically operated or comprise electrical devices. Sometimes an electrical contact is formed between a rotating component and a stationary component via a slip ring to enable electrical communication with a downhole electrical device. However, the high pressures, dirty environments, and shocks that often occur in a downhole environment can have a detrimental impact on the functionality and longevity of the electrical contact.

SUMMARY

In general, a system and methodology are provided to facilitate communication of electrical signals in harsh environments and between components that undergo relative rotation with respect to each other. The technique comprises rotatably mounting a first component with respect to a second component. The first component also is electrically coupled with the second component via an electrical coupler. The electrical coupler may comprise a first electrical contact located at the first component and a second electrical contact located at the second component. The first electrical contact is conductively connected with the second electrical contact via a conductive bearing, e.g. a sliding bearing, a rolling element type bearing, or other suitable bearing. The conductive bearing is located in a volume which is filled with a substantially incompressible fluid to protect the bearing.

However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and:

FIG. 1 is a schematic illustration of an example of a system having components which undergo relative rotation with respect to each other, according to an embodiment of the disclosure;

FIG. 2 is a cross-sectional view of an example of an electrical coupler which couples components which undergo relative rotation with respect to each other, according to an embodiment of the disclosure;

FIG. 3 is a cross-sectional view of another example of an electrical coupler which couples components which undergo relative rotation with respect to each other, according to an embodiment of the disclosure;

FIG. 4 is a cross-sectional view of another example of an electrical coupler which couples components which undergo relative rotation with respect to each other, according to an embodiment of the disclosure; and

FIG. 5 is a cross-sectional view of another example of an electrical coupler which couples components which undergo relative rotation with respect to each other, according to an embodiment of the disclosure.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

The present disclosure generally relates to a system and methodology for facilitating communication of electrical signals between components which rotate relative to each other. The system and methodology for communicating electrical signals are useful in a variety of harsh environments, e.g wellbore environments. In many applications, the technique comprises rotatably and electrically coupling a first component with a second component. For example, the first component may be electrically coupled with the second component via an electrical coupler. The electrical coupler utilizes a first electrical contact conductively connected with a second electrical contact via a conductive bearing. By way of example, the conductive bearing may be in the form of a plain bearing, e.g. sliding bearing, or a rolling-type bearing, e.g. a cylindrical roller bearing or a ball bearing. The conductive bearing is located in a volume which is filled with a substantially incompressible fluid to protect the bearing.

The electrical coupling utilizes a pressure permeable housing in combination with the conductive bearing, e.g. a rolling bearing. In some applications, the rolling bearing may comprise a ball bearing in the form of a shielded or sealed ball bearing unit. The pressure permeable housing may be packed with grease or another suitable fluid that is substantially incompressible. The grease or other fluid may be de-gassed to further reduce its compressibility. The bearing is protected against overheating via operation at a relatively slow speed and/or via flow of cooling fluid past the bearing. In certain wellbore applications, for example, a cooling flow of fluid may be directed past the electrical coupling to remove heat generated by the bearing. In drilling applications, a flow of drilling mud may be used to provide the cooling.

In some embodiments, the bearing can be used to perform a dual duty of providing both a conductive path between components undergoing relative rotation and as a bearing to facilitate the relative rotation. The electrical coupler may be constructed to provide a sealed electrical path through the races of the bearing, thus allowing electrical signals to be passed between the components. In some applications, the electrical signals are passed between a rotatable shaft and an adjacent housing via conductive, rolling contact elements of a bearing placed between the rotatable shaft and the adjacent housing.

Referring generally to FIG. 1, an example of a system 20, e.g. a well system, is illustrated as having a first component 22 which is rotatable with respect to a second component 24. Electrical signals routed along a conductor 26, e.g. an electrical communication line, pass between the first component 22 and the second component 24 via an electrical coupler 28. By way of example, the electrical signals may be sent to or transmitted from an electrical device 30.

In the specific example illustrated, system 20 is in the form of a well system comprising a well string 32, e.g. a tubing string, extending along a wellbore 34 from a wellhead, a drilling rig, or other suitable surface equipment 36. In some applications, one of the components 22, 24 is stationary while the other is rotatable. For example, first component 22 may be stationary with respect to the portions of well string 32 above component 22 while the second component 24 is rotatable with respect to first component 22. However, the components 22, 24 may be rotated at different speeds relative to a third reference and/or they may be rotated at the same speed during certain periods of operation. The rotatable second component 24 may comprise a shaft or a variety of other types of rotatable components. It should be noted the electrical coupler 28 also may be used in a variety of surface or non-well related applications to facilitate transmission of electrical signals between components that undergo relative rotation with respect to each other.

Referring generally to FIG. 2, an example of the electrical coupler 28 is illustrated. In this example, the electrical coupler 28 comprises a housing 38 which may be part of or attached to first component 22. The housing 38 is engaged with second component 24 in a manner which allows relative rotation between the housing 38/first component 22 and the second component 24. By way of example, the second component 24 may comprise a rotatable shaft 40 which rotates about an axis 42. The electrical coupling 28 further comprises an electrical contact 44 positioned at the first component and another electrical contact 46 positioned at the second component. Additionally, a bearing 48 is mounted between the first component 22 and the second component 24, e.g. between housing 38 and shaft 40. The bearing 48 may comprise a variety of sliding-type bearings or rolling-type bearings, e.g. ball bearings, cylindrical roller bearings, or rolling pin bearings. The bearing 48 also is formed of a conductive material, e.g. a conductive steel material, to enable efficient transfer of electrical signals between electrical contacts 44 and 46.

In the example illustrated, bearing 48 comprises a first race 50 mounted against first component 22 and in contact with first electrical contact 44. The bearing 48 also comprises a second race 52 mounted against second component 22 and in contact with second electrical contact 46. The electrical contacts 44, 46 are otherwise insulated but conductively connected to the races 50, 52, respectively, so that an electrical signal may pass through bearing 48. The bearing 48 further comprises a plurality of rotatable members 54 which are rotatably trapped between the first race 50 and the second race 52.

In an embodiment, bearing 48 is in the form of a plain bearing having sliding contact surfaces which may be lubricated. In other embodiments, bearing 48 may be in the form of a rolling-type bearing having rolling contact elements in the form of rotatable members 54. By way of example, rotatable members 54 may be cylindrical rollers, balls, pins, or other suitable rotatable members. Additionally, bearing 48 may be in the form of a shielded or sealed unit bearing. The bearing 48 also may be electrically isolated via insulating material or insulating devices so that short circuits do not occur. In some applications, the bearing races 50, 52 or other bearing components may be formed partially of plastic or other materials and provided with conductive contacts to maintain the electrical connection during relative rotation of first component 22 with respect to second component 24.

As illustrated in FIG. 2, the bearing 48 is located in a cavity 56 disposed between the first component 22 and the second component 24. By way of example, the cavity 56 may be formed in housing 38 and may extend to second component 24. The cavity 56 has a volume for receiving a substantially incompressible fluid 58 which surrounds at least a portion of the bearing 48. In a variety of applications, the substantially incompressible fluid 58 may be in the form of grease. Additionally, the substantially incompressible fluid 58 may be de-gassed to further reduce its compressibility.

The electrical coupler 28 also is constructed to enable pressure equalization between the cavity 56 and an exterior region 60 outside of cavity 56 and housing 38. According to an embodiment, the pressure equalization may be achieved through a porous material 62. The porous material 62 may be in the form of a porous gland/membrane 64 placed between the first component 22, e.g. the stationary component, and the second component 24, e.g. the rotary component.

By making provision for a volume around the bearing 48 that is filled with nearly incompressible fluid 58, e.g. grease, fluid that enters cavity 56 is effectively isolated from the bearing 48. At most, minute volumes of external fluid can enter the cavity 56 before the pressures are equalized. Once equilibrium is achieved, there is no mechanism to further drive the exterior fluid into bearing 48. The porous gland 64 may further be used to filter out abrasive particles from external fluid which enters cavity 56. The porous gland 64 also blocks fluid flow which could potentially remove the grease or other incompressible fluid 58 from cavity 56.

The porous gland/membrane 64 also may be originally filled with a clean and neutral fluid 66, e.g. oil or grease, such that minute amounts of this clean and neutral fluid 66 are displaced into cavity 56 during pressure equalization. The clean and neutral fluid 66 may have a volume greater than the change in volume of the fluid 58 in cavity 56 when placed under hydrostatic compression resulting from the incoming external fluid that drives the clean fluid 66 from the pores of porous material 62. Undesirable, external borehole fluid is thus maintained in external region 60 outside of cavity 56. In some applications, the porous gland 64 may be in the form of a felt material, and the clean fluid 66 may be in the form of a grease impregnating the felt material. However, various other porous materials 62 may be used to construct porous gland 64 including sponge materials, porous metals, porous composites, and/or other suitably porous materials. Similarly, a variety of greases, viscous liquids, and other suitable fluid and material mixtures may be used for fluids 58 and 66. Depending on the application, fluid 66 and fluid 58 may be of the same type of fluid or of different types of fluid.

If the volume of grease or other substantially incompressible fluid 58 is large enough, a “stirring” effect resulting from rotation of the bearing 48 does not reach the outer zones of cavity 56. The size of cavity 56 may thus be used to further limit the ability of external fluid to migrate to the bearing 48 if minute amounts of such external fluid move into the outer reaches of cavity 56. By using shielded or sealed bearings 48, the mechanical stirring effect can further be reduced or eliminated, thus providing additional protection against particles in the substantially incompressible fluid 58. The shielded or sealed bearings 48 also are filled with grease or another suitable fluid. In some applications, the shielded or sealed bearings 48 may be in the form of standard shielded or sealed bearings.

Referring generally to FIG. 3, another embodiment of the electrical coupler 28 is illustrated. In this embodiment, housing 38 is a porous housing formed at least in part of porous material 62. It should be noted, however, the porous material 62 used to form housing 38 may be a different type of material than the porous material used to form porous gland/membrane 64. For example, the porous gland 64 may be a soft material, e.g. felt, and the porous material 62 used to form porous housing 38 may be a harder material which retains its form. Examples of harder, porous material comprise a porous metallic material, porous ceramic material, or porous composite material. A specific example of a material comprises (Mite® Bearing material available from Beemer Precision, Inc.

In the example illustrated, the pores of porous housing 38 may be pre-loaded with clean fluid 66. The clean fluid 66 may be a suitable grease, oil, or other material. Considerable volumes of clean fluid 66 may be held in the porous material of housing 38 for the purpose of pressure compensation. The large areas exposed to pressure allow the housing 38 to transmit balancing fluid more quickly and to thus support quicker pressure compensation. A variety of seals 68, e.g. conventional shaft seals, may be disposed between the first component 22 and second component 24, as illustrated. The structure illustrated in FIG. 3 facilitates operation of the system with considerable pressure gradients acting across the bearing 48. As with the previous embodiment, the bearing 48 may be electrically isolated so that electrical signals can pass between electrical contacts 44, 46 without creating a short-circuit.

In another embodiment, housing 38 is a solid housing and seals 68 are used between first component 22 and second component 24, as illustrated in FIG. 4. However, a porous element 70 is located in housing 38 and extends through housing 38 between cavity 56 and exterior region 60. The porous element 70 is formed with a suitable porous material 62 so as to facilitate pressure equalization. As with previous embodiments, the pores of porous material 62 may be filled with clean fluid 66. The porous element 70 is sized properly so as to act as a clean fluid reservoir while remaining sealed at the interface with the surrounding portions of housing 38.

In another embodiment illustrated in FIG. 5, housing 38 is again a solid housing and seals 68 are used between first component 22 and second component 24. However, the porous element 70 is located in second component 24 and extends through the second component 24 between cavity 56 and exterior region 60. By way of example, the second component 24 may be in the form of shaft 40 and porous element 70 may be routed along shaft 40 for exposure to both cavity 56 and exterior region 60. In some applications, the entire shaft 40 may be formed from porous material 62 so as to facilitate a greater rate of pressure equalization. In this latter embodiment, the pores of porous material 62 also may be filled with clean fluid 60. In some applications, both first component 22 and second component 24 (or portions of each of the components 22, 24) may be formed of a suitable porous material 62.

Depending on the application, system 20 may have a variety of configurations comprising other and/or additional components. For example, the shape and structure of the components 22 and 24 may vary in size and configuration depending on the parameters of a given application and environment. Similarly, a variety of materials may be used to construct the various components of the electrical coupler 28. The system 20 also may utilize many types of electrical devices 30 for various downhole applications or other types of applications. The bearing 48 may comprise a variety of plain bearings having conductive sliding contact surfaces or a variety of roller-type bearings having conductive rolling members, e.g. cylinders, balls, pins, or other suitable, conductive rolling contact elements.

Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

Claims

1. A system for use in a well, comprising:

a well string having a first component, a second component, and an electrical coupler for conducting electric current between the first component and the second component, the first component being rotatable with respect to the second component, the electrical coupler comprising: a first electrical contact positioned in the first component; a second electrical contact positioned in the second component; a bearing formed of conductive material and mounted between the first component and the second component, the bearing being formed of a ii conductive material and being located in a cavity between the first component and the second component; and a substantially incompressible fluid disposed in the cavity.

2. The system as recited in claim 1, wherein pressure equalizes between the cavity and an exterior region outside of the cavity.

3. The system as recited in claim 2, wherein the substantially incompressible fluid comprises a grease.

4. The system as recited in claim 3, wherein the first component comprises a shaft.

5. The system as recited in claim 4, wherein the bearing comprises a first race mounted against the first component in contact with the first electrical contact, a second race mounted against the second component in contact with the second electrical contact; and a plurality of conductive contact elements rotatably trapped s between the first race and the second race.

6. The system as recited in claim 2, wherein the pressure equalizes through a porous gland material placed between the first component and the second component.

7. The system as recited in claim 6, wherein the porous gland material contains a fluid.

8. The system as recited in claim 2, wherein the pressure equalizes through a porous material located in at least one of the first component or the second component.

9. The system as recited in claim 2, wherein the second component is formed of a porous material and further wherein the pressure equalizes through the porous material.

10. The system as recited in claim 2, wherein the first component is formed of a porous material and further wherein the pressure equalizes through the porous material.

11. A method, comprising:

rotatably mounting a first component with respect to a second component;

locating a first electrical contact at the first component and a second electrical contact at the second component;

conductively connecting the first electrical contact and the second electrical contact via a conductive bearing; and

filling a volume around at least a portion of the conductive bearing with a substantially incompressible fluid.

12. The method as recited in claim 11, wherein rotatably mounting comprises rotatably mounting first and second well components.

13. The method as recited in claim 12, wherein conductively connecting comprises connecting via the conductive bearing by engaging a first race of the conductive bearing with the first component, engaging a second race of the conductive bearing with the second component, and rotatably capturing a plurality of the conductive rotatable members between the first race and the second race such that electricity may be conducted through the first race, the plurality of conductive rotatable members, and the second race.

14. The method as recited in claim 13, wherein filling the volume comprises filling the volume with a grease.

15. The method as recited in claim 13, further comprising equalizing pressure between an exterior region and the volume via a porous material.

16. The method as recited in claim 15, further comprising using the porous material to prevent movement of particulates into the volume.

17. The method as recited in claim 12, further comprising moving the first component and the second component downhole into a wellbore and removing heat generated by the ball bearing via flow of a well fluid.

18. A system for communicating electrical signals, comprising:

a first component rotatably mounted with respect to a second component;

a first electrical contact located at the first component and a second electrical contact located at the second component, the first electrical contact being operatively coupled with the second electrical contact via a conductive bearing, the conductive bearing having a plurality of rotatable members which rotate during rotation of the first component with respect to the second component; and

a housing creating a volume around at least a portion of the conductive bearing, the volume being filled with a substantially incompressible fluid.

19. The system as recited in claim 18, wherein the first component and the second component are downhole well components.

20. The method as recited in claim 18, wherein the conductive bearing comprises a first race engaged with the first component, a second race engaged with the second component, wherein the plurality of rotatable members are rotatably trapped between the first race and the second race such that electricity may be conducted through the first race, the plurality of rotatable members, and the second race.