FIELD

The present disclosure relates to a thrust bearing assembly, for example for providing high thrust capacity.

BACKGROUND

Thrust bearings are used to permit rotation between parts, particularly when under axial loading. In the oil and gas industry, for example, there are many situations which involve rotation between parts at high axial loads, and as such thrust bearings are commonly required, with the reliability of the bearings having a significant impact on successfully and efficiently performing operations.

Mechanical thrust bearings are known, which typically include opposing bearing surfaces in rotary sliding contact, which may thus be subject to high wear rates, require lubrication and the like. The surface area of sliding contact may dictate the load capacity of the bearing, with larger loads typically accommodated with larger bearing surface areas. In some examples this may be achieved by increasing the diameter of the bearing. However, in some circumstances this might not suit applications with space restrictions, such as downhole applications.

SUMMARY

An aspect of the present disclosure relates to a thrust bearing, comprising,

a mandrel; and

a bearing assembly mounted axially along the mandrel and comprising:

a bearing housing and a bearing piston axially and rotatably mounted relative to each other; and

a plurality of axially distributed bearing piston chambers defined between the bearing housing and the bearing piston, said bearing piston chambers configured to receive a bearing fluid for use in transmitting axial load between the bearing housing and the bearing piston when the bearing assembly is loaded in a first axial direction,

wherein the mandrel and the bearing assembly are axially moveable relative to each other in the first axial direction between a first configuration in which the mandrel is axially disengaged from the bearing assembly, and a second configuration in which the mandrel axially engages and loads the bearing assembly in the first axial direction, and wherein the mandrel and at least a portion of the bearing assembly are rotatable relative to each other at least when the mandrel and the bearing assembly are in their second configuration.

When the mandrel and the bearing assembly are in their first configuration, the bearing assembly may be considered to be in an unloaded state, with no axial load being applied due to the mandrel and bearing assembly being disengaged, and when the mandrel and the bearing assembly are in their second configuration, the bearing may become loaded in the first axial direction. Thus, the thrust bearing may be selectively operated or activated in accordance with relative axial movement between the bearing assembly and the mandrel. In some examples the thrust bearing may be defined as an axially unidirectional thrust bearing.

When the mandrel and the bearing assembly are in their second configuration axial loading may be transmitted therebetween in the first axial direction, via the bearing fluid when received within the bearing piston chambers. Further, the relative rotation between the mandrel and at least a portion of the bearing assembly when in the second configuration may permit axial load to be transmitted while still accommodating relative rotation, thus providing the function of a thrust bearing.

The bearing assembly may be connectable to an object, wherein the bearing assembly is operable to accommodate relative rotation and axial load transmission between the mandrel and the connected object when the bearing assembly and the mandrel are in the second configuration. In one example the bearing housing may be connectable to an object. In other examples the bearing piston may be connectable to an object.

The object may comprise any object, and it is not intended for the present disclosure to restrict the use of the thrust bearing to any specific application, unless explicitly mentioned otherwise.

The object may comprise a payload which is to be supported by, acted upon and/or operated by the mandrel. In some examples where the thrust bearing is used to permit a payload to be supported by the mandrel the thrust bearing may function as a swivel. In some examples the object may form part of an apparatus or system. The thrust bearing may be provided separately from, or as part of the same apparatus or system.

The object may comprise at least a portion of a downhole object, apparatus or system, such as a downhole tool, downhole tubing and/or the like. In this example the thrust bearing may be for use downhole, such that the thrust bearing may be defined as a downhole thrust bearing.

The object may comprise a drilling assembly, such that the thrust bearing may be utilised in drilling operations.

The object may include a jarring tool, such as a downhole jarring tool. In some examples the thrust bearing may form part of a jarring tool. The thrust bearing may accommodate axial loads required as part of a jarring operation, for example to seek to dislodge a stuck object (e.g., drill string, BHA etc.), to install an object (e.g., running casing, cementing operations, piling operations etc.), to retrieve an object (e.g., pulling casing, completions etc.) and/or the like. The ability to provide relative rotation between the mandrel and the bearing assembly, at least when in the second configuration, may provide a suitable operational drive to the jarring tool. In some examples the relative rotation between the mandrel and the bearing assembly may be converted through a suitable mechanism or assembly to provide jarring, such as linear jarring.

In some examples the permitted relative axial movement between the mandrel and the bearing assembly may permit the mandrel to be used to load a load mechanism forming part of the jarring tool. In such an example the thrust bearing, when reaching its second configuration, may function to provide a load limit within the load mechanism of the jarring tool.

The object may include a resonator.

In some examples the thrust bearing may be used in or with apparatus for the retrieval and/or deployment of equipment, infrastructure and the like from/to a wellbore. In one example the thrust bearing may be used in or with apparatus for removing or pulling casing from a wellbore, for example as part of a decommissioning operation. In this example the bearing assembly (e.g., the bearing housing) may be connectable to a casing spear for providing an anchor or other suitable connection to a casing string.

In some instances the thrust bearing may be required to accommodate significant axial loads, and as such the thrust bearing may be defined as a high capacity thrust bearing. In this respect the provision of multiple bearing piston chambers may contribute to high load capabilities, as will be discussed in further detail below.

The first configuration may not define a set relative position of the mandrel and bearing assembly. Instead, the first configuration may be any relative position in which the mandrel and the bearing assembly are axially disengaged.

The first axial direction may be a direction of relative axial movement between the mandrel and the bearing assembly. In this regard the first axial direction may be defined as a first relative axial direction between the bearing assembly and the mandrel. Such relative axial movement between the mandrel and the bearing assembly in the first axial direction may be achieved by at least one of: the mandrel being axially moveable relative to an axially stationary bearing assembly; the bearing assembly being axially moveable relative to an axially stationary mandrel; and both the mandrel and the bearing assembly being axially moveable.

A degree of relative axial movement between the mandrel and the bearing assembly in the first axial direction may be permitted before reaching the second configuration (i.e., while still in the first configuration), and thus before the mandrel and bearing assembly become axially engaged. Such permitted relative axial movement without corresponding restriction by engagement between the mandrel and the bearing assembly may permit or provide a useful function within an associated apparatus, system or method. Numerous possibilities exist, and may include, without limitation, rotatably unlocking the mandrel relative to the bearing assembly (e.g., axially disengaging a rotary connection), operating an associated apparatus, such as a jarring apparatus, resonator etc., opening/closing a valve, such as a ball valve, circulating sub etc., reconfiguring a mechanical system, providing a setting action such as to set slips, a sealing device, a reaming tool, an expandable drill bit etc. The mandrel and the bearing assembly may be moveable relative to each other in a reverse second axial direction. Such movement in the second axial direction may function to reduce or remove load from the bearing assembly. Movement in the second axial direction may permit the mandrel and the bearing assembly to be axially disengaged and move from the second configuration towards the first configuration. In some examples such reverse movement may function to engage or re-engage a rotary connection between the mandrel and the bearing assembly.

The second axial direction may be a direction of relative axial movement between the mandrel and the bearing assembly. In this regard the second axial direction may be defined as a second relative axial direction between the bearing assembly and the mandrel. Such relative axial movement between the mandrel and the bearing assembly in the second axial direction may be achieved by at least one of: the mandrel being axially moveable relative to an axially stationary bearing assembly; the bearing assembly being axially moveable relative to an axially stationary mandrel; and both the mandrel and the bearing assembly being axially moveable.

In some examples the mandrel and bearing assembly may be configured to be moved relative to each other in reverse first and second axial directions without being configured in or reaching the second configuration. That is, multiple axial manipulation events may be permitted in reverse directions without loading the bearing assembly. This may provide a desired functional capability within an associated apparatus, system or method.

As noted above, the mandrel and at least a portion of the bearing assembly may be rotatable relative to each other at least when in the second configuration. In one example the mandrel and the bearing housing may be rotatable relative to each other. In this example the bearing housing may also be connectable to an object such that the thrust bearing may accommodate relative rotation between the mandrel and a connected object. Alternatively, or additionally, the mandrel and the bearing piston may be rotatable relative to each other.

The mandrel and at least a portion of the bearing assembly (e.g., the bearing housing) may be rotatable relative to each other when in both the first and second configurations. In an alternative example, the mandrel and at least a portion of the bearing assembly may be rotatably fixed relative to each other when in the first configuration. Such rotatable fixing may facilitate torque transmission between the mandrel and at least a portion of the bearing assembly when in the first configuration. Such torque transmission may have application in numerous operations, such as downhole drilling operations and the like.

The mandrel and the bearing housing may be rotatably fixed relative to each other when in the first configuration. In this example the bearing housing may also be connectable to an object such that the thrust bearing may accommodate torque transfer between the mandrel and the object when the bearing assembly and mandrel are in their first configuration.

Relative axial movement between the mandrel and the bearing assembly in the first axial direction towards the second configuration may facilitate the mandrel being rotatably unlocked relative to at least a portion of the bearing assembly, for example the bearing housing. Such unlocking may be established prior to or concurrently with the mandrel and the bearing assembly reaching their second configuration.

The thrust bearing may comprise a releasable rotatable connection between the mandrel and at least a portion of the bearing assembly (e.g., the bearing housing). The releasable rotatable connection may comprise, for example, a spline connection, key and key way arrangement, dog connection, shear arrangement or the like. The releasable rotatable connection may be engaged when the mandrel and the bearing assembly are in their first configuration, and released by relative axial movement between the mandrel and the bearing assembly in the first axial direction. In some examples the releasable axial connection may be resettable, for example by relative axial movement between the mandrel and the bearing assembly in a reverse second axial direction.

The thrust bearing may comprise the bearing fluid.

During loading of the bearing assembly a force may be applied between the bearing housing and the bearing piston in the first axial direction, with relative axial movement between the bearing housing and bearing piston in the first axial direction being resisted by bearing fluid within the bearing piston chambers. In this respect any relative movement permitted between the bearing housing and the bearing piston when the bearing assembly is loaded may be provided in accordance with the fluid properties of the bearing fluid.

In one example the bearing fluid may be substantially incompressible, such that relative movement of the bearing housing and the bearing piston in the first axial direction may be considered negligible. The bearing fluid may comprise a hydraulic fluid, such as hydraulic oil. In other examples a compressible fluid may be utilised, in which case some relative axial movement between the bearing housing and the bearing piston may be permitted when loaded.

Fluid pressure within the bearing piston chambers may increase when the bearing assembly is loaded in the first axial direction. Fluid pressure may be relieved when the bearing assembly is unloaded (i.e., when loading applied between the mandrel and the bearing assembly is reduced or removed entirely). The thrust bearing may comprise a suitable sealing arrangement or system to ensure containment of fluid/pressure, while still accommodating necessary relative movements, such as relative axial and rotatable movements.

By providing multiple bearing piston chambers the fluid pressures developed for a given load may be reduced, for example relative to a bearing with a single chamber. This may allow the operational pressures to be more readily maintained below the burst pressure of the thrust bearing, and in some cases may provide benefits in terms of lower pressure sealing requirements, reducing fatigue on seals and thus improving longevity, permit thinner walled structures to be utilised, which may deliver cost benefits etc.

The use of the bearing piston chambers to accommodate axial loading is such that the thrust bearing may be defined as a hydraulic thrust bearing (a pneumatic thrust bearing may also be considered). Further, with the provision of the axially distributed bearing piston chambers the thrust bearing may be defined as an axially stacked hydraulic (or pneumatic) thrust bearing.

The provision of the bearing piston chambers configured to receive the bearing fluid may minimise or eliminate the requirement for mechanical based thrust mechanisms, as typically used in mechanical type thrust bearings, which may be subject to high wear rates, friction heating, lubrication issues and the like. The bearing fluid may also function to carry or transmit the applied axial load while accommodating low resistance/drag during relative rotation between the bearing housing and the bearing piston. This may minimise energy losses within the thrust bearing. Furthermore, the bearing fluid may function to provide a degree of lubrication between relatively rotating parts.

The axial load applied through the bearing assembly may be divided between the plurality of axially distributed bearing piston chambers. The use of a fluid load transfer may minimise the requirement for exacting tolerances which may be required in axially stacked mechanical thrust bearings, to otherwise ensure appropriate contact loading is divided between stacked mechanical bearings in a controlled and desired manner.

The use of axially distributed bearing piston chambers may thus permit an axial distribution of the applied load. In this respect a design requirement to accommodate a higher load may be met by increasing the number of axially distributed bearing piston chambers, thus axially extending the bearing assembly. Such axial extension may minimise the requirement to meet a high load design requirement by increasing the diameter of the thrust bearing, which may not be desirable or indeed possible in some deployments, such as in downhole applications where available diameters are often very restricted. Further, such additional load capabilities by axial extension rather than increasing any diameter may permit any flow bore diameter through the thrust bearing to be maintained, or even maximised.

In some examples the thrust bearing may define a modular structure, permitting more ready adaptation to meet specific design requirements by allowing the requisite number of bearing piston chambers to be provided without requiring bespoke solutions in each case. For example, stacking or assembling standardised modules as required may permit a desired bearing design to be achieved.

At least two of the plurality of bearing piston chambers may be in pressure communication with each other. In one example each of the plurality of bearing piston chambers may be in pressure communication with each other. Such pressure communication may allow pressure balancing between different chambers, which may contribute to providing equal load sharing. This may assist to minimise the requirement for very accurate stack-up tolerances which would otherwise be required in similarly axially stacked mechanical type thrust bearings.

Pressure communication between the bearing piston chambers may be provided by a pressure transfer arrangement, such as a floating piston mechanism, diaphragm or the like. Such a pressure transfer arrangement may facilitate pressure communication without necessitating fluid communication,

At least two, and in some examples each of the plurality of bearing piston chambers may be in fluid communication with each other to allow pressure balancing therebetween, which may contribute to providing equal load sharing. Fluid communication may be achieved via a flow path interconnecting multiple bearing piston chambers. At least a portion of the flow path may be defined between the mandrel and the piston assembly, for example between the mandrel and the bearing piston. At least a portion of the flow path may be provided by a groove or channel in one or both of the mandrel and the piston assembly (e.g., the bearing piston). At least a portion of the flow path may comprise a spiral flow path. In one example the piston assembly may comprise communication ports for allowing communication between the bearing piston chambers and the flow path. The communication ports may be radial ports, for example.

When the bearing assembly is loaded in the first axial direction, tension may be applied axially along the bearing housing, whereas compression may be axially applied along the bearing piston. In an alternative example, when the bearing assembly is loaded in the first axial direction, compression may be applied axially along the bearing housing, whereas tension may be applied axially along the bearing piston. Other variations are possible, such as both the bearing housing and bearing piston being in tension, or both the bearing housing and bearing piston being in compression.

The bearing assembly may be mounted relative to the mandrel such that the bearing piston is positioned radially between the mandrel and the bearing housing.

In some examples the bearing assembly may be mounted externally of the mandrel. In such an example the mandrel may be defined as an inner mandrel. In this example the bearing housing may define an outermost surface of the thrust bearing. That is, a further outer housing may not be provided, which may assist to minimise the outer diameter of the thrust bearing, or indeed maximise the available inner diameter.

Alternatively, the bearing assembly may be mounted internally of the mandrel. In such an example the mandrel may be defined as an outer mandrel. In this example the bearing housing may define an inner surface of the thrust bearing. That is, a further inner housing may not be provided. In some examples the bearing housing may define at least a portion of a flow path through the thrust bearing.

The mandrel may include an axial loading structure configured to engage the bearing assembly when in the second configuration. The axial loading structure may comprise an annular structure, such as an annular load shoulder. The axial loading structure may be integrally provided with the mandrel. Alternatively, the axial loading structure may be separately provided and secured relative to the mandrel, for example via a threaded connection or the like. In some examples the axial loading structure may also function to provide a connection interface to permit the mandrel to be connected to a separate component, such as a separate tool, apparatus, system etc. In some examples the axial loading structure may be defined as a piston stack hammer.

The bearing assembly may comprise a bearing loading structure configured to be axially engaged by the mandrel, for example by an axial loading structure provided on the mandrel. The bearing loading structure may comprise an annular structure, such as an annular load shoulder. In some examples the bearing loading structure may be defined as an impact piston.

The thrust bearing may be arranged such that the mandrel axially engages one of the bearing housing and the bearing piston when the mandrel and the bearing assembly are in their second configuration. In one example the mandrel may axially engage the bearing housing when the mandrel and the bearing assembly are in their second configuration. However, in an alternative example the mandrel may axially engage the bearing piston when the mandrel and the bearing assembly are in their second configuration. In this example the bearing piston may be driven axially relative to the bearing housing, with load transfer achieved via the bearing fluid. Further, in this example the bearing housing may be connectable to an object, such that axial loading may be transferred between the mandrel and the object.

In examples where the mandrel axially engages the bearing piston, said bearing piston may comprise a bearing loading structure, such as an impact piston. The bearing loading structure may form part of the bearing piston, for example a terminating axial end of the bearing piston.

When the mandrel axially engages the bearing piston at least a portion of the bearing piston may become rotatably secured, for example via friction engagement, with the mandrel, such that at least a portion of the piston assembly rotates relative to the piston body.

The bearing housing may be sealed relative to the mandrel, for example via one or more sealing structures, such as one or more O-rings, cup seals etc. The bearing housing may be sealed relative to the mandrel at one axial end region of the bearing assembly. Any sealing provided between the bearing housing and the mandrel may be configured to accommodate one or both axial and rotational relative movement therebetween.

The bearing piston may be sealed relative to the mandrel, for example via one or more sealing structures, such as one or more O-rings, cup seals etc. The bearing piston may be sealed relative to the mandrel at one axial end region of the bearing assembly. Any sealing provided between the bearing piston and the mandrel may be configured to accommodate one or both axial and rotational relative movement therebetween.

In one example the bearing housing may be sealed relative to the mandrel via a first sealing arrangement towards a first axial side of the bearing assembly, and the bearing piston may be sealed relative to the mandrel via a second sealing arrangement towards an opposite second axial side of the bearing assembly. The plurality of bearing piston chambers may be provided axially between the first and second sealing arrangements. In one example the first and second sealing arrangements may function to retain bearing fluid within the thrust bearing, particularly at elevated operational pressures when the thrust bearing is under axial load. As defined above, the bearing housing and the bearing piston are rotatably mounted relative to each other. In this respect the bearing piston may be journaled relative to the bearing housing. The bearing piston may comprise a piston journal which facilitates rotatable engagement between the bearing piston and the bearing housing. In some examples the piston journal may be provided adjacent a sealing assembly which functions to provide rotatable sealing between the bearing piston and the bearing housing.

The bearing piston may comprise a plurality of piston heads which provide a boundary of a respective bearing piston chamber. The piston heads may be sealed relative to the bearing housing. Any suitable sealing arrangement between the piston heads and the bearing housing may be used. The sealing arrangement may provide dynamic sealing capabilities, configured to provide sealing between relatively rotatable bearing housing and bearing piston. In one example at least one cup seal may be utilised. An O-ring seal may be provided. One or more back up sealing arrangements may be provided.

In some examples the thrust bearing may comprise at least one wiper interposed between the bearing piston (e.g., a piston head) and the bearing housing. The at least one wiper may be configured to provide a wiping action against one, or both, of the bearing piston and bearing housing.

At least one and in some examples each of the piston heads may comprise a piston journal which facilitates rotatable engagement between the bearing piston and the bearing housing.

The bearing piston may comprise a piston stem extending axially between adjacent piston heads, providing an axial connection therebetween in at least one axial direction (e.g., the first axial direction). The piston stem may be generally cylindrical. In one example the piston stem may be sealingly engaged with the bearing housing. Such an arrangement may assist in providing isolation of associated bearing piston chambers.

A terminating piston stem may extend from a piston head towards a terminating end of the bearing piston. In this example the terminating piston stem may be configured to be axially engaged by the mandrel when the mandrel and the bearing assembly are in their second configuration, thus providing a transmission point of load into the bearing assembly from the mandrel. The mandrel may directly engage the piston stem. Alternatively, an additional component, such as an impact piston, may be axially interposed between the terminating piston stem and the mandrel.

The bearing piston chambers may define high pressure chambers, in that fluid pressure within these bearing piston chambers may be increased upon axial loading of the thrust bearing. The thrust bearing may further comprise a low pressure chamber defined between the bearing housing and bearing piston and being axially interposed between adjacent bearing piston chambers. The low pressure chamber may be vented to an environment external to the bearing assembly, for example to a surrounding environment (e.g., a downhole environment) in which the thrust bearing is deployed.

In some examples the low pressure chamber may accommodate thermal expansion of bearing fluid within the bearing piston chambers.

In examples where two bearing piston chambers are provided a single low pressure chamber may be present. However, where more than two bearing piston chambers are present multiple low pressure chambers may be provided, and axially alternating with the bearing piston chambers.

The thrust bearing may comprise a mechanical bearing interface in at least one of the bearing piston chambers. This mechanical bearing interface may be utilised in the event of loss of the bearing fluid (e.g., due to seal failure etc.) and axial collapse of the bearing piston chambers, for example when the thrust bearing is under load, when under the effect of a differential pressure etc. In this way the mechanical bearing interface may permit a mechanical thrust bearing function to be provided as a contingency measure, allowing the thrust bearing to continue its operation, at least on a temporary basis, until the thrust bearing may be recovered for repair and/or replacement. The mechanical bearing interface may be provided on or mounted to one or both of the bearing housing and the bearing piston. The mechanical bearing interface may be provided on, or define, one or more axial boundaries of at least one of the bearing piston chambers. The mechanical bearing interface may comprise, for example, one or more bearing rings. In one example each of the bearing piston chambers may comprise a mechanical bearing interface. In one example the bearing housing may be a unitary structure. However, in an alternative example the bearing housing may comprise multiple connected components. In this regard the bearing housing may be provided in modular form. Such a modular form may assist with ease of manufacture of individual components, ease of assembly, ease of matching specific design requirements (e.g., number of bearing piston chambers) with minimal inventory or minimal requirement for bespoke designs, and/or the like.

Individual components of the bearing housing may be connected in any suitable way, for example via threaded connections.

In one example the bearing housing may comprise an end body module. The end body module may be positioned towards one axial end of the bearing assembly. The end body module may be configured to be sealingly engaged with the mandrel. The end body module, together with the bearing piston, may define one of the plurality of bearing piston chambers.

The bearing housing may comprise a body coupling module. The body coupling module may be positioned towards one axial end of the bearing assembly (e.g., opposite the end body module). The body coupling module may facilitate connection of the bearing housing to an object. In some examples the body coupling module may be coupled (e.g., directly coupled) to the end body module.

The body coupling module may provide rotary sealing engagement with a portion of the bearing piston, for example with a piston stem portion of the bearing piston. In one example the body coupling module may comprise at least one rotary seal configured to provide sealing against a portion of a bearing piston.

The bearing housing may comprise one or more intermediate body modules axially interconnected (e.g., via threaded connections) between the end body module and the body coupling module. Each intermediate body module, together with the bearing piston, may define one of the plurality of bearing piston chambers. At least one, and in one example each intermediate body module may provide rotary sealing engagement with a respective portion of the bearing piston, for example with respective piston stem portions of the bearing piston. At least one, and in one example each intermediate body module may comprise at least one rotary seal configured to provide sealing against a portion of a bearing piston.

In one example, as noted above, individual housing modules may be connected together to form the bearing housing. In this respect each module may be connected together via a connection interface, such as a threaded interface. In some examples the connection interfaces may be generally axially aligned with respective low pressure chambers. This may permit the connection arrangements to be provided with no or limited sealing capabilities, thus simplifying construction. The connection interfaces may be such that upon connection associated sealing features may be energised, such as sealing features for sealing against portions of the bearing piston.

The connection interfaces may be configured to accommodate the principal axial load type (e.g., tension or compression) when the bearing assembly is under load.

In one example the bearing piston may be a unitary structure. However, in an alternative example the bearing piston may comprise multiple components. In this regard the bearing piston may be provided in modular form. Such a modular form may assist with ease of assembly, ease of matching specific design requirements (e.g., number of bearing piston chambers) with minimal inventory or minimal requirement for bespoke designs, and/or the like.

Individual components of the bearing piston may be axially connected together. However, in some examples individual components may not be connected, but instead axially stacked in abutting relationship relative to each other. The individual bearing piston components may be held axially together under axial compression when the bearing assembly is loaded.

The bearing piston may comprise a plurality of bearing piston modules. Each bearing piston module may be provided similarly or identical to each other. The bearing piston modules may be axially stacked relative to each other. Each bearing piston module may be in abutting relationship with an adjacent bearing piston module. An abutting interface between adjacent bearing modules may comprise a friction interface. In some examples the friction interface may comprise a low-friction material. The friction interface may comprise a high wear material. When a compressive axial load is applied along the bearing piston frictional engagement between the bearing piston modules may permit torque transference between adjacent modules, such that rotation of one module may cause rotation of an adjacent module. In some examples, however, a degree of rotational slippage between adjacent bearing piston modules may be present. The degree of slippage may depending on factors such as the number of modules present, the axial compressive load applied, the speed of a rotational drive (e.g., the rotational speed of the mandrel), and the like. In some cases one or more bearing piston modules located distally (i.e., away from) a loading point may not rotate, or rotate at a significantly slower rate than a bearing piston module located proximal to (e.g., at) the loading point.

Each bearing piston module may comprise a piston head which provides a boundary of a respective bearing piston chamber. One or more of the piston heads may comprise a piston sealing arrangement for sealing engagement with the bearing housing. In some examples one or more of the piston heads may comprise a piston journal which facilitates rotatable engagement between the bearing piston and the bearing housing. In some examples the piston journal may be provided adjacent a sealing assembly which functions to provide rotatable sealing between the bearing piston and the bearing housing.

At least one bearing piston module may comprise a piston stem extending axially from the piston head. The piston stem may be integrally formed with its associated piston head. However, in alternative examples the piston stem may be separately formed and otherwise connected to or engaged with its associated piston head.

The piston stem may be generally cylindrical. In one example the piston stem may be sealingly engaged with the bearing housing. Such an arrangement may assist in providing isolation of associated bearing piston chambers.

The piston stem may be configured to axially engage an adjacent bearing piston module. Such an arrangement may permit axial loading to be transmitted along the different modules. In one example the piston stem of one module may be configured to engage the piston head of an adjacent bearing piston module. A communication flow path may be provided at an interface between the piston stem of one bearing piston module and the piston head of an adjacent bearing piston module, wherein the communication flow path facilitates communication with an associated bearing piston chamber. This may be used as part of an arrangement to permit multiple bearing piston chambers to be in pressure communication with each other. In one example one or both of the adjacent piston stem and piston head may include at least one axial notch, recess etc. which provides a region of relief when the adjacent piston stem and head are engaged. This region of relief may define the communication flow path.

At least one bearing piston module may comprise a groove or channel which forms part of a communication path between at least two bearing piston chambers. In one example the grove or channel may be provided on an inner surface of the bearing piston module. The groove or channel may be a spiral groove or channel. The groove or channel may merge with a flow path provided at an interface between the piston stem of one bearing piston module and the piston head of an adjacent bearing piston module.

The bearing piston may comprise a bearing loading module configured to be axially engaged by the mandrel, for example by an axial loading structure provided on the mandrel. The bearing loading module may be sealed against the mandrel. The bearing loading module may be sealed against the bearing housing. In some examples the bearing loading module may be defined as an impact piston. A piston stem of an adjacent bearing piston module may axially engage the bearing loading module, such that loading applied by the mandrel may be transmitted through the loading module and into the stacked bearing piston modules.

The loading module may define a bearing piston chamber with the bearing housing.

An aspect of the present disclosure relates to a method for operating a thrust bearing, comprising:

establishing relative axial movement in a first axial direction between a mandrel and a bearing assembly mounted axially along the mandrel to bring the mandrel into axial engagement with the bearing assembly, wherein the bearing assembly includes a bearing housing and a bearing piston axially and rotatably mounted relative to each other;

applying axial load between the engaged mandrel and bearing assembly in the first axial direction, wherein said axial load is transmitted between the bearing piston and the bearing housing via a bearing fluid contained in a plurality of axially distributed bearing piston chambers defined between the bearing housing and the bearing piston; and

providing relative rotation between the mandrel and at least a portion of the bearing assembly.

The method may comprise operating the thrust bearing according to any other aspect. In this respect the features defined in relation to any other aspect may equally apply within the present defined method.

For example, the method may comprise connecting the bearing assembly to an object, wherein the bearing assembly is operable to accommodate relative rotation and axial load transmission between the mandrel and the connected object when the bearing assembly and the mandrel are in the second configuration. In one example the method may comprise connecting the bearing housing to an object.

A degree of relative axial movement between the mandrel and the bearing assembly in the first axial direction may be permitted before the mandrel and bearing assembly become axially engaged. Such permitted relative axial movement without corresponding restriction by engagement between the mandrel and the bearing assembly may permit or provide a useful function within an associated apparatus, system or method. Thus, the step of establishing relative axial movement in a first axial direction between a mandrel and a bearing assembly may comprise operating an associated apparatus, system or method.

The method may comprise providing relative axial movement in a reverse second axial direction between the mandrel and the bearing assembly reduce or remove load from the bearing assembly. Movement in the second axial direction may permit the mandrel and the bearing assembly to be axially disengaged. The method may comprise providing relative rotation between the mandrel and the bearing housing.

The method may comprise rotatably unlocking the mandrel relative to at least a portion of the bearing assembly during the relative movement in the first axial direction.

The method may comprise establishing relative axial movement in the first axial direction between the mandrel and the bearing assembly to bring the mandrel into axial engagement with the bearing piston. In this example the bearing piston may be driven axially relative to the bearing housing, with load transfer achieved via the bearing fluid.

An aspect of the present disclosure relates to a bearing assembly, comprising:

a bearing housing; and

a bearing piston mounted relative to the bearing housing to define a plurality of axially distributed bearing piston chambers within the bearing assembly, said bearing piston chambers configured to receive a fluid for use in transmitting axial load between the piston body and the bearing piston assembly when the bearing is under axial loading.

The bearing assembly may be configured to be mounted axially along a mandrel. The bearing assembly may be provided in accordance with any other aspect.

An aspect of the present disclosure relates to a thrust bearing, comprising,

a mandrel; and

a bearing assembly including a bearing housing rotatably mounted relative to the mandrel, and a bearing piston mounted radially between the mandrel and the piston body to define a plurality of axially distributed bearing piston chambers within the bearing assembly, said bearing piston chambers configured to receive a fluid for use in transmitting axial load between the piston body and the piston assembly when the piston body and piston assembly are axially loaded;

wherein the mandrel is axially moveable relative to the bearing assembly.

An aspect of the present disclosure relates to a thrust bearing, comprising,

a mandrel; and a bearing assembly including a bearing housing mounted relative to the mandrel, and a bearing piston mounted radially between the mandrel and the bearing housing to define a plurality of axially distributed bearing piston chambers within the bearing assembly, said bearing piston chambers configured to receive a fluid for use in transmitting axial load between the piston body and the bearing piston when the bearing assembly is axially loaded;

wherein the mandrel and the bearing assembly are axially moveable relative to each other between a first configuration in which the mandrel is axially disengaged from the bearing assembly, and a second configuration in which the mandrel axially engages the bearing assembly to axially load said bearing assembly.

An aspect of the present disclosure relates to a jarring apparatus comprising a thrust bearing according to any other aspect.

An aspect of the present disclosure relates to a kit of parts for use in forming a thrust bearing, comprising:

a mandrel;

a plurality of housing modules, wherein a selected number of housing modules are connectable together to define a bearing housing of a bearing assembly to be mounted on the mandrel; and

a plurality of bearing piston modules, wherein a selected number of bearing piston modules are arrangeable together to define a bearing piston of the bearing assembly.

An aspect of the present disclosure relates to a method for forming a thrust bearing, comprising:

providing a mandrel; and

forming a bearing assembly on the mandrel from a selected number of housing modules and a selected number of bearing piston modules.

It should be recognised that the features defined in relation to one aspect may be applied in combination with any other aspect. BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a longitudinal cross-sectional view of a thrust bearing illustrated in an unloaded state;

Figure 2 is a longitudinal cross-sectional view of the thrust bearing of Figure 1 illustrated in a loaded state;

Figure 3 provides an enlarged view of the thrust bearing of Figure 1 between dashed lines 3-3;

Figures 4 and 5 provide alternative isometric views of a bearing housing module of the thrust bearing of Figure 1 ;

Figure 6 is a longitudinal cross sectional view of the bearing housing module of Figures 4 and 5;

Figures 7 and 8 provide alternative isometric views of a bearing piston module of the thrust bearing of Figure 1 ;

Figure 9 is a longitudinal cross sectional view of the bearing piston module of Figures 7 and 8;

Figures 10 to 13 are isometric cross-sectional views of the thrust bearing of Figure 1 during stages of assembly;

Figures 14 to 16 are longitudinal cross-sectional views of different examples of a thrust bearing; and

Figures 17 and 18 provide diagrammatic operational sequences of a jarring apparatus which may use a thrust bearing. DETAILED DESCRIPTION OF THE DRAWINGS

The present disclosure relates to a thrust bearing which may be utilised in any number of applications. In the description that follows example forms of thrust bearings are presented, without any intended restriction on a specific application or use, although some examples will be suggested, and one specific example use of a thrust bearing in combination with a jarring tool will be provided.

Figure 1 is a longitudinal cross-sectional view of a hydraulic thrust bearing 10 which includes an inner mandrel 12 and a bearing assembly 14 mounted axially along an outer surface of the mandrel 12. The bearing assembly 14 includes an outer bearing housing 16 which defines an outer surface of the thrust bearing 10, and a bearing piston 18 which is positioned radially between the mandrel 12 and the bearing housing 16, wherein the bearing housing 16 and the bearing piston 18 are axially and rotatably moveable relative to each other.

While the thrust bearing 10 may be used in multiple applications, in one example the thrust bearing 10 may be for use downhole, for example in a wellbore associated with the exploration and recovery of hydrocarbons. In this case the thrust bearing 10 may define an outer diameter which permits suitable downhole deployment and operation.

The mandrel 12 may be coupled to or form part of a string, such as a tubing string 19 (e.g. drill string). In one example the tubing string 19 may function to apply an axial force and rotary drive to the mandrel 12. The bearing housing 16 may be coupled to an object 22, such that the thrust bearing 10 may be operable to accommodate relative rotation and axial load transmission between the mandrel 12 and the connected object 22. The object 22 may comprise any object, and it is not intended for the present disclosure to restrict the use of the thrust bearing 10 to any specific application. In some examples the object 22 may comprise a payload, an apparatus or system, such as a downhole apparatus or system, a downhole tool, downhole tubing, a drilling assembly, a jarring tool, a resonator, a casing spear, a Bottom Hole Assembly (BHA) and/or the like.

The mandrel 12 includes an axial load shoulder 20 which is provided on a connector 24 which may be used to connect the mandrel 12 to further components 26, such as might form part of the connected object 22. However, in other examples the mandrel 12 may terminate at the axial load shoulder 20. The bearing piston 18 includes a load piston module 28, wherein in the configuration illustrated in Figure 1 the axial load shoulder 20 of the mandrel 12 and the load piston module 28 of the bearing piston 18 are axially separated, such that the mandrel 12 may be considered to be axially disengaged from the bearing assembly 14. When in the illustrated axially disengaged configuration of Figure 1 the thrust bearing 10 may be considered to be in a first configuration.

An optional releasable rotary connection 29 (e.g., a spline connection) may be provided between the mandrel 12 and the bearing housing 16, wherein the releasable connection 29 is in a connected state when the thrust bearing 10 is in the illustrated first configuration of Figure 1. In this case torque may be transmitted via the releasable rotary connection 29 between the mandrel 12 and the bearing housing 16, and thus the connected object 22. Such torque transmission may be used in applications such as drilling, milling etc.

A plurality of axially distributed bearing piston chambers 30 (four in the present example) are defined between the bearing housing 16 and the bearing piston 18, said bearing piston chambers 30 configured to receive a bearing fluid (e.g., hydraulic oil) for use in transmitting axial load between the bearing housing 16 and the bearing piston 18 when the bearing assembly 14 is loaded, which will be described in more detail below.

As illustrated in Figure 2, to load the thrust bearing 10 the mandrel 12 and the bearing assembly 14 are moved axially relative to each other in the direction of opposing arrows 32a, 32b, which may be defined as a first relative axial direction. Such relative axial movement may be achieved by at least one of: the mandrel 12 being axially moveable in the direction of arrow 32a with the bearing assembly 14 being axially stationary; the bearing assembly 14 being axially moveable in the direction of arrow 32b with the mandrel 12 being axially stationary; and simultaneous axial movement of the mandrel 12 and the bearing assembly 14 in the direction of respective opposing arrows 32a, 32b. However, for the purposes of the present description it is assumed that the mandrel 12 is moved in the direction of arrow 32a, with the bearing assembly 14 being held axially stationary, for example by virtue of being fixed (intentionally or otherwise) relative to a wellbore in which the thrust bearing 10 is deployed. Such movement in the first relative axial direction will release the rotary connection 29 between the mandrel 12 and the bearing housing 16, and will also bring the load shoulder 20 of the mandrel 12 into axial engagement with the load piston portion 28 of the bearing piston 18, such that the load applied by the mandrel 12 in the direction of arrow 32a will be imparted to the bearing piston 18. When in this axially engaged configuration of Figure 2 the thrust bearing 10 may be considered to be in a second configuration.

The axial load applied on the bearing piston 18 will be transmitted to the bearing housing 16, and connected object 22, via the bearing fluid within the bearing piston chambers 30. Furthermore, the released rotary connection 29 permits the mandrel 12 and the bearing housing 16 (and thus the connected object 22) to be rotated relative to each other while also transmitting the applied axial load.

The provision of the bearing piston chambers 30 and bearing fluid may minimise or eliminate the requirement for mechanical based thrust mechanisms which may be subject to high wear rates, friction heating, lubrication issues, manufacturing tolerance issues and the like. The bearing fluid may also function to carry or transmit the applied axial load while accommodating low resistance/drag during rotation. This may minimise energy losses within the thrust bearing 10. Furthermore, the bearing fluid may function to provide a degree of lubrication between the relatively rotating parts.

Further, the use of axially distributed bearing piston chambers 30 may permit an axial distribution of the applied load, in that each piston chamber 30, or bearing stage, carries only a proportion of the total applied load, which may provide benefits in terms of improved load capacity and the like. In this respect a design requirement to accommodate a higher load may be met by increasing the number of axially distributed bearing piston chambers 30, thus axially extending the bearing assembly 14. Such axial extension may minimise any requirement to increase the diameter of the thrust bearing 10 for load capability reasons, which may not be desirable or indeed possible in some deployments, such as in downhole applications where available diameters are often very restricted. Further, such additional load capabilities by axial extension rather than increasing any diameter may permit any flow bore diameter through the thrust bearing 10 (e.g., through the mandrel 12) to be maintained, or even maximised. The ability to axially distribute the load along the thrust bearing 10 may also permit the pressure in each bearing piston chamber 30 to be minimised. This may provide benefits in terms of lower pressure sealing requirements, reducing fatigue on seals and thus improving longevity and the like.

The permitted relative movement between the mandrel 12 and the bearing assembly 14 before reaching the engaged second configuration may provide a useful function, for example within an associated apparatus, system or method. Numerous possibilities exist, and may include, without limitation, rotatably unlocking the mandrel 12 relative to the bearing assembly 14 (i.e., releasing the rotary connection 29 as noted above), operating an associated apparatus, such as apparatus associated with the object 22, opening/closing a valve, such as a ball valve, circulating sub etc., reconfiguring a mechanical system, providing a setting action such as to set slips, a sealing device, a reaming tool, an expandable drill bit etc.

The mandrel 12 and the bearing assembly 14 may also be moveable relative to each other in a reverse second axial direction. Such movement in the second axial direction may function to reduce or remove load from the bearing assembly 14. Movement in the second axial direction may permit the mandrel 12 and the bearing assembly14 to be axially disengaged and move from the second configuration (Figure 2) towards the first configuration (Figure 1). Thus, a degree of relative movement between the mandrel 12 and the bearing assembly 14 may be permitted in reverse axial directions without axial engagement between the mandrel 12 and the bearing piston 18. Such reverse axial manipulation may provide a useful function or operational benefit, for example as noted above.

Relative movement of the mandrel 12 and the bearing assembly 14 in the reverse second direction may also permit re-engagement of the rotary connection 29 (if present), which may again permit torque to be transmitted via the rotary connection 29 between the mandrel 12 and the bearing housing 16, and thus the connected object 22. As such, the releasable rotary connection 29 may be resettable.

Reference is now made to Figure 3 which is an enlarged view of the thrust bearing 10 between dashed lines 3-3 of Figure 1. The bearing assembly 14 is sealed relative to the mandrel 12 at opposing axial ends, specifically via a first mandrel seal 38 towards a first axial end 34, and a second mandrel seal 40 towards a second axial end 36. In the present example the first mandrel seal 38 is provided between the mandrel 12 and the bearing housing 16, and the second mandrel seal 40 is provided between the mandrel 12 and the bearing piston 18, specifically the load piston module 28 of the bearing piston 18. The first and second mandrel seals 38, 40 function to retain the bearing fluid within the bearing assembly 14.

The bearing piston chambers 30 are in fluid communication with each other via a communication path which includes a spiral groove 42 extending along the inner surface of the bearing piston 18, and multiple communication passages 44 extending radially through the bearing piston 18 to facilitate fluid communication between the respective bearing piston chambers 30 and the spiral groove 42. In some examples an annular gap between the mandrel 12 and bearing piston 18 may be such that the spiral groove 42 may not be necessary. Further, the mandrel 12 may alternatively, or additionally, include a suitable groove. In some cases the groove 42 may not necessarily be spiral, but may be provided in any suitable form.

Fluid communication between the bearing piston chambers 30 ensures that the chambers 30 are pressure balanced with each other, such that when the thrust bearing 10 is loaded the axial load is uniformly distributed between the bearing piston chambers 30. Such pressure balancing may avoid disproportionate loading being applied within the thrust bearing 10, which may otherwise establish failure risk. Further, the uniform load distribution by pressure balancing may assist to minimise the requirement for very accurate stack-up tolerances which may otherwise be required in similarly axially stacked mechanical type thrust bearings.

When the thrust bearing 10 is under load the bearing fluid pressure will increase, such that the bearing piston chambers 30 may be defined as high pressure chambers. The thrust bearing 10 further comprises axially distributed low pressure chambers 46 (three in the present example) which are interspersed between the bearing piston chambers 30, and which are each in fluid communication with the environment externally of the thrust bearing 10 via respective radial ports 48. The low pressure chambers 42 permit axial load transfer between the bearing housing 16 and the bearing piston 18 via the bearing piston chambers 30 without being compromised or affected by any hydraulic locking action within the thrust bearing 10. Further, the low pressure chambers 42 accommodate thermal expansion/contraction of the bearing fluid within the bearing piston chambers 30.

The bearing housing 16 is of a modular construction and includes multiple connected components. In the present example the bearing housing 16 comprises an end body module 16a towards the first axial end region 34, wherein the first mandrel seal 38 is provided on this end body module 16a. The bearing housing 16 also comprises a body coupling module 16b towards the second axial end region 36 which facilitates connection of the bearing housing 16 to the object 22 (Figure 1). The bearing housing 16 further comprises a plurality (two in the present example) of intermediate body modules 16c axially interconnected via threaded connections 50 between the end body module 16a and the body coupling module 16b. In the present example the threaded connections 50 are generally axially aligned with the respective low pressure chambers 46, which may permit the connections 50 to be provided with no or limited sealing capabilities, thus simplifying construction.

Reference is additionally made to Figures 4 to 6, wherein Figures 4 and 5 provide alternative isometric views of an intermediate body module 16c, whereas Figure 6 is a longitudinal cross sectional view of the intermediate body module 16c of Figures 4 and 5. The intermediate body module 16c includes an outer body surface 52 which forms part of the outer surface of the thrust bearing 10, wherein the ports 48 extend radially into the outer body surface 52 to facilitate communication with the low pressure chambers 46 (Figure 3) when the thrust bearing 10 is assembled. An external male threaded portion 54 is provided on one end of the module 16c, and an internal female threaded portion 56 is provided on an opposite end of the module 16c, wherein the male threaded portion 54 is configured to threadedly engage the female threaded portion 56 of an adjacent module 16c (or modules 16a, 16b), and vice versa.

The intermediate body module 16c further includes a piston bore surface 58 which is configured to be sealingly engaged by the bearing piston 18. A stepped transition 60 is provided between the female threaded portion 56 and the piston bore surface 58.

A piston back-up ring 62 is mounted on the male threaded end of the intermediate body module 16c and axially captivates a seal member 64 which in use sealingly engages an outer surface of the bearing piston 18. In the present example the piston back-up ring 62 is slidingly inserted into the intermediate body module. When the male threaded portion 54 of the intermediate body module 16c is connected to the female threaded portion 56 of an adjacent module 16c (or end body module 16a) the piston back-up ring may become engaged against stepped transition 60, thus captivating the seal member 64. The piston back-up ring 62 may function as an anti-extrusion device to minimise extrusion of the seal member 64 when under pressure. Further, the piston back-up ring 62 defines an inner circumferential journal surface 65 which provides a journal support relative to the bearing piston 18.

The piston back-up ring 62 includes circumferentially spaced slots 66 which permit fluid communication between the radial ports 48 and the full extent of the low pressure chambers 46 when the housing modules are interconnected.

It should be noted that the end body module 16a includes a piston bore surface, female threaded portion and associated features which are similar to that of the intermediate body module 16c. Similarly, the body coupling module 16b includes a male threaded portion and associated features which are similar to that of the intermediate body module 16c.

Referring again to Figure 3, the bearing piston 18 is also of a modular construction and in addition to the load piston module 28 also includes multiple axially stacked piston modules 18a (three provided in the present example). The load piston module 28 includes an impact piston 70 which is arranged to be engaged by the load shoulder 20 of the mandrel 12 (see Figure 2), and a piston drive cap 72 which is arranged to engage an adjacent piston module 18a. The load piston module 28 includes the second mandrel seal 40 on an internal surface thereof which provides sealing with the mandrel 12. The load piston module 28 also includes an outer sealing structure 74 which provides sealing with the body coupling module 16b. The load piston module 28, together with the body coupling module 16b, defines one of the plurality of bearing piston chambers 30.

Reference is additionally made to Figures 7 to 9, wherein Figures 7 and 8 provide alternative isometric views of a piston module 18a, whereas Figure 9 is a longitudinal cross sectional view of the piston module 18a of Figures 7 and 8. The piston module 18a comprises a piston head 74 and a smaller diameter cylindrical stem 76 extending axially from the piston head 74. A piston journal 78 is mounted on the piston head 74 and defines a circumferential journal surface which rotatably engages the piston bore surface 58 (see Figure 6) of a body coupling module 16c or of the end body module 16a. The piston journal 78 is held in place via keys 80, wherein said keys 80 are radially captivated when the piston module 18a is mounted within the bearing housing 16. A seal stack 82 is mounted on the piston head 74, wherein the seal stack 82 is axially captivated by the piston journal 78. The seal stack 82 provides sealing engagement with the piston bore surface 58 (Figure 6) of a body coupling module 16b or of the end body module 16a. An axial end face 84 of the piston head 74 defines a moving barrier of an associated bearing piston chamber 30, and includes a radial notch 92.

The piston stem 76 defines a bearing housing sealing surface 88 which includes a region of slightly increased outer diameter. When the thrust bearing 10 is assembled the bearing housing sealing surface 88 is sealingly engaged by the seal member 64 of an intermediate body module 16c (see Figure 6) of the bearing housing 16. Further, sealing surface 88 is also engaged by journal surface 65 of the piston back-up ring 62 (see Figure 6). The piston stem 76 terminates at an axial stem face 90 which includes a radial notch 86.

The inner surface of the piston module 18a includes a spiral groove 94, which defines a portion of the spiral groove 42 of the bearing piston 18 for use in providing fluid communication between the bearing piston chambers 30.

When the piston modules 18a are installed, as illustrated in Figure 3, the axial stem face 90 of one piston module 18a axially engages the axial end face 84 of the piston head of an adjacent piston module 18a. This of course is not the case with the piston modules 18a located towards each of the first and second axial end regions 34, 36 of the bearing assembly 14. In this regard the piston head end face 84 of the piston module 18a towards the first axial end region 34 defines a terminating axial end of the bearing piston 18, and the axial stem face 90 of the piston module 18a towards the second axial end region 36 axially engages the load piston module 28. When adjacent piston modules 18a are engaged, the radial notches 86, 92 in the axial end faces may function to provide the communication passages 44 which facilitate fluid communication between the bearing piston chambers 30 and the spiral groove 42(94).

Referring again to Figure 3, the thrust bearing 10 further comprises a mechanical bearing ring 96 in each bearing piston chamber 30. The mechanical bearing rings 96 may be utilised in the event of loss of the bearing fluid (e.g., due to seal failure etc.) and axial collapse of the bearing piston chambers 30, for example when the thrust bearing 10 is under load, when under the effect of a differential pressure etc. In this way the mechanical bearing rings 96 may permit a mechanical thrust bearing function to be provided as a contingency measure, allowing the thrust bearing 10 to continue its operation, at least on a temporary basis, until the thrust bearing 10 may be recovered for repair and/or replacement.

The bearing assembly 14 further includes fill ports 98, 100, provided at opposing end regions 34, 36 of the bearing assembly 14, for use in filling the bearing assembly 14 with a suitable bearing fluid. In one example the bearing fluid may be delivered into the bearing assembly via port 98, and when the bearing fluid is visually identified as exiting port 100 a complete fill may be verified, and suitable plugs set within the ports 98, 100.

The modular construction of the bearing assembly 14 may facilitate improved assembly, and may permit variation in bearing capacity to be readily achieved without reverting to bespoke designs. In this respect initial stages of a process for assembling the thrust bearing 10 is illustrated in Figures 10 to 13.

The end body module 16a is mounted on the mandrel 12, as shown in Figure 10, followed by installation of a mechanical bearing ring 96 as shown in Figure 11. Following this, as shown in Figure 12 a piston module is inserted in the annular space between the mandrel 12 and the end body module 16a. An intermediate body module 16c is then screwed to the end body module 16a via connector 50, as illustrated in Figure 13, thus effectively completing a first bearing stage which includes a bearing piston chamber 30. This process of installing a mechanical bearing ring 96, piston module 18a and intermediate body module 16c may be repeated to provide the requisite number of bearing stages and piston chambers 30, with the final assembly stage involving securing the body coupling module 16b to the last intermediate body module 16c, and installing the load piston module 28, as illustrated in Figure 3.

In the Example of Figures 1 to 3 the thrust bearing 10 includes four bearing piston chambers 30. However, any required number of bearing chambers/stages may be provided using the same common modular components. For example, an alternative thrust bearing 110 is illustrated in Figure 14 which includes nine bearing piston chambers 130.

In the example described above the mandrel 12 is disclosed as being axially moved in the direction of arrow 32a (see Figure 2) to load the bearing assembly 14. When in the context of a downhole bearing such manipulation of the mandrel 12 may include upward movement, or pulling, of the mandrel 12. However, the principles and functionality of the thrust bearing may still be achieved with alternative loading directions. For example, Figure 15 illustrates an alternative thrust bearing 210 which is similar to thrust bearing 10 described above, but axially inverted such that a mandrel 12 is moved in a reverse direction of arrow 232 to load a bearing assembly 214. When in the context of a downhole bearing such manipulation of the mandrel 212 may include downward movement of, or applying weight to, the mandrel 212.

In the examples described above a bearing assembly is mounted externally of a mandrel. However, in an alternative example, illustrated in Figure 16, a thrust bearing 310 may include a bearing assembly 312 which is mounted internally of a mandrel 312. The thrust bearing 310 is similar in most respects to the thrust bearing 10 first shown in Figure 1 , and as such no further description will be given. However, in the present example the thrust bearing 310 may be considered to be radially inverted relative to the thrust bearing 10.

As noted above, thrust bearings according to the present disclosure may be utilised in any number of applications. However, there follows an example of a jarring apparatus in which a thrust bearing according to the present disclosure may be used.

A jarring apparatus, generally identified by reference numeral 400, is diagrammatically illustrated in cross-section in Figure 17. The jarring apparatus 400, which is only partially shown in Figure 17, is illustrated in a non-jarring configuration and is sized and arranged to be deployed into a wellbore. Although not shown, the jarring apparatus 400 may be deployed into a wellbore on wireline, tubing, such as coiled tubing, jointed pipe or the like.

The jarring apparatus 400 comprises a first jarring assembly in the form of a mandrel 412, and a second jarring assembly in the form of an outer housing assembly 414. The jarring apparatus 400 is configured such that relative rotation established between the mandrel 412 and outer housing assembly 414 causes reciprocating motion of a jarring mass 424 to generate repeated linear jarring forces. In this regard, as jarring is achieved through relative rotation, the apparatus 400 may be defined as a rotary jarring apparatus. In use, the outer housing assembly 414 may be engaged with an object (not shown), such as a stuck object within a wellbore, with the mandrel 412 rotated via a suitable rotary drive, such as a motor, rotatable work string or the like, thus applying the generated jarring forces to the object.

In the present example the jarring apparatus 400 is arranged to provide axial jarring forces in the direction of arrow 416, which may be defined as an uphole direction. In use, an axial pulling force may be applied to the mandrel 412 in the direction of arrow 416 during the jarring operation, and a load/resistance applied to the housing 414 in the direction of arrow 417, such as from a stuck object, suspended load etc. Such loading through the apparatus 400 may contribute to the generation of a jarring force. However, in the present example the jarring apparatus 400 incorporates features to provide a degree of protection from excessive loading or overloading.

The apparatus 400 comprises a thrust bearing 410, which in the present example is illustrated in a simplified format, for clarity purposes. However, the thrust bearing 410 may be provided in accordance with any of the example thrust bearings described above. The simplified thrust bearing 410 includes a first thrust shoulder 420 provided on the mandrel 412, and a second thrust shoulder 428 provided on the housing 414. In this respect the first thrust shoulder may be equivalent to the load shoulder 20 and the second thrust shoulder 428 may be equivalent to the load piston module 28 of the thrust bearing 10 first shown in Figure 1.

In the configuration shown in Figure 17 the first and second thrust shoulders 420, 428 are axially separated and thus disengaged. However, as will be described in more detail below, relative axial movement between the mandrel 412 and housing 414 (in the relative direction of arrows 416, 417) will eventually bring the first and second thrust shoulders 420, 428 into engagement, such that axial loading may be transmitted between the mandrel 412 and housing 414 via the thrust bearing 410, thus diverting such loading from other components within the apparatus 400. In this respect the thrust bearing 410 may function as or define a load limiter. The thrust bearing 410 permits rotation between the first and second thrust shoulders 20, 22 when engaged, thus providing a rotary bearing function.

The jarring mass 424 is radially positioned between the mandrel 412 and housing 414, and is axially moveable in reverse directions (directions 416, 417) relative to both the mandrel 412 and housing 414. The jarring mass 424 is rotatably fixed relative to the mandrel 12 via a rotary connection 426, such as a keyed or splined connection. However, in other examples the jarring mass may alternatively be rotatably fixed relative to the housing 414.

The jarring mass 424 includes a first impact surface 430, and the housing 414 includes a second impact surface 432, wherein, in use, reciprocating axial movement of the jarring mass 424 causes the first and second impact surfaces 430, 432 to axially impact together, thus generating repeated axial jarring forces within the apparatus 400. In an alternative example the mandrel 412 may comprise an axial impact surface, alternative or in addition to the impact surface provided on the housing 414. As the jarring mass 424 is responsible for generating impact within the apparatus 400, the jarring mass may thus also be defined as a hammer.

A force mechanism 434 in the form of a power spring (e.g., a Bellville spring stack) is provided within the apparatus 400, and is configured, in use, to bias the jarring mass 424 to move axially in the direction of arrow 416, and thus to bias the first and second impact surfaces 430, 432 into engagement. As will be described in more detail below, relative movement between the mandrel 412 and housing 414 in the direction of arrows 416, 417, will cause the spring 434 to be engaged and compressed by an annular shoulder 436 on the mandrel 412. In this respect, the force generated by the spring 434 against the jarring mass 424 is a function of the compression or displacement of the spring 434. In some examples the spring 434 may be uncompressed until engaged by the mandrel. However, in other examples the spring may carry a degree of pre compression.

The jarring apparatus 400 further includes a lifting assembly 438 which is operable by relative rotation between the mandrel 412 and housing 414 to cyclically lift the jarring mass 424 in the direction of arrow 417 against the bias of the spring 434, and release the lifted jarring mass 424 to permit the jarring mass to be driven by the spring 434 in the direction of arrow 416, causing the impact surfaces 430, 432 to rapidly engage to establish a jarring force. Any suitable form of lifting assembly 438 may be provided to function to cyclically lift and release the jarring mass 424 in the manner described.

In the present example the lifting assembly 438 includes a first lifting structure 440 rotatably and axially fixed relative to the housing 414, and a second lifting structure 442 rotatably fixed, but axially moveable, relative to the mandrel 412. In the present example the second lifting structure 442 is integrally formed with the jarring mass 424, and is thus rotatably connected to the mandrel 412 via rotatable connection 426. In other examples the second lifting structure 442 may be separately formed and rotatably coupled to the jarring mass 426. In further examples the second lifting structure 442 may be separately rotatably coupled to the mandrel 412. In such examples the jarring mass 424 may not necessarily be rotatably coupled to the mandrel 412.

The lifting structures 440, 442 include cooperating cam structures which cooperate during relative rotation therebetween to cause the second lifting structure 442 to be axially moved in cyclical lifting and dropping phases, thus effecting axial reciprocating movement of the jarring mass 424.

Loading may be applied between the first and second lifting structures 440, 442 which is a function of the biasing force provided by the spring 434. In this respect such loading may be controlled by appropriate selection of the spring 434, by the extent of compression of the spring 434 caused by relative movement between the mandrel 412 and housing 414, and by virtue of the load limiting effect of the thrust bearing 410, which will be described in more detail below. This may assist to increase the longevity of the first and second lifting structures, and thus of the lifting assembly. The jarring apparatus 400 further includes an optional releasable rotary connection 444 (similar to connection 30 illustrated in the example of Figure 1) between the mandrel 412 and housing 414. In the present example the releasable rotary connection 444 includes a splined connection. When the apparatus 400 is configured as shown in Figure 17, the releasable rotary connection 444 is engaged, and the mandrel 412 and housing 414 are rotatably coupled. Such a configuration may thus prevent any jarring to occur, to the extent that this configuration may be defined as a non-jarring configuration. Further, the rotary connection 444 may allow torque to be transmitted between the mandrel 412 and housing 414, which may be useful or required in many applications, such as in drilling applications and the like.

When jarring is to be performed, the mandrel 412 and housing 414 are axially moved relative to each other (in the relative direction of arrows 416, 417) to disengage the rotary connection 444, as illustrated in Figure 18, thus permitting relative rotational movement to be achieved to operate the lifting assembly 438 and lift/drop the jarring mass 424 to generate jarring. In some applications the housing 414 may be held stationary, such that the relative movement is achieved by moving, for example pulling, and rotating the mandrel 412. Such axial movement, in addition to releasing the rotary connection 444, causes the annular shoulder 436 of the mandrel 412 to pick up and energise the spring 434, thus establishing the bias force acting against the jarring mass 424 in the direction of arrow 416.

Although not shown, the apparatus may further comprise a releasable axial connection between the mandrel 412 and housing 414 which first needs to be disengaged to allow the relative axial movement. Such a releasable axial connection may be releasable upon application of a threshold release force applied between the mandrel 412 and housing 414.

In the configuration of Figure 18 the mandrel 412 has been moved until the thrust bearing 410 is engaged, such that further axial loading applied between the mandrel 412 and housing 414 (e.g., by increasing an overpull on the mandrel 412) will be transmitted via the thrust bearing 410 and thus diverted from the spring 434 and the lifting assembly 438. In this configuration the spring 434 may be considered to provide its maximum bias force, subject to any minor variation caused by the cyclical lifting of the jarring mass 424 by the lifting assembly 438. While Figure 18 illustrates the thrust bearing 410 fully engaged, it should be understood that jarring may be effected at any stage following release of the rotary connection 444 and energising of the spring 434. In this respect, the extent of axial loading applied between the mandrel 412 and housing 414, prior to engagement of the thrust bearing 410, will dictate the level of bias force developed by the spring 434 and thus the level of jarring forces created within the apparatus 400. In this respect, a user may control the jarring force output by controlling the overpull on the mandrel 412, up until the load limit has been reached via engagement of the thrust bearing 410. This can provide a significant degree of operational flexibility within the apparatus 400, while minimising risk of overloading.

It should be understood that the examples provided herein are merely exemplary of the present disclosure and that various modifications may be made thereto without departing from the scope defined by the claims.