Patent Grant
8356670
The present invention relates to a ball seat assembly and to a method of controlling fluid flow through a hollow body. In particular, but not exclusively, the present invention relates to a ball seat assembly having a ball seat which selectively defines a restriction to passage of a ball along a bore of a hollow body, and to a method of controlling fluid flow through a hollow body using such a ball seat.
In the oil and gas exploration and production industry; a wellbore or borehole of an oil or gas well is typically drilled from surface to a first depth and lined with a steel casing which is cemented in place. The borehole is then extended and a further section of smaller diameter casing is located in the extended section and also cemented in place. This process is repeated until the wellbore has been extended to a certain depth, and tubing known as a liner is then typically located in the borehole, extending from the deepest casing section (the casing ‘shoe’) to a producing formation. The well is then completed by locating a string of production tubing within the casing/liner and perforating the liner such that well fluids may flow from a producing formation, into the liner, and through the production tubing to surface.
The location of a liner extending from a casing shoe typically involves hanging the liner from the casing shoe using a liner hanger. Liner hangers include mechanical slips or the like which are selectively activated downhole to grip the internal wall of the casing, so that the liner may be suspended from the casing shoe and then cemented in place. Such liner hangers are typically run into the casing on a workstring carrying a liner setting tool, and are hydraulically actuated on exposure to fluid above a specified setting pressure, which urges the slips outwardly into engagement with the casing wall. These setting pressures are typically significantly higher than the hydrostatic pressure at depth within the well borehole, to prevent premature activation of the hanger.
To activate the hanger and thus to set the liner within the casing, it is necessary to close off fluid flow down through the workstring and the liner using the setting tool, so that the pressure of the fluid above the setting tool can be raised above the determined level necessary to activate the hanger. Currently, this is typically achieved by providing a setting tool including a ball seat which receives a ball dropped into the workstring from surface. The ball passes down into the setting tool, and lands on the ball seat to close fluid flow through the liner. The fluid above the tool is then pressured up, activating the hanger to set the liner. A further increase in fluid pressure acting on the ball (and thus on the ball seat) shears pins holding the ball seat in place. The ball seat is then carried down to a position where the seat is desupported, so that the ball can pass through the seat and exit the setting tool. Fluid flow through the liner has then been re-opened and the setting tool and workstring can be recovered to surface.
Whilst the above described tools and methods are effective at setting liner hangers within a casing, such ball seats are typically rated to shear at a relatively high pressure, typically 3000 psi or more, in order to prevent premature shearing out of the ball seat. At these high pressures, when the ball shears the seat out, there is an undesirable hydraulic shock imparted to the workstring carrying the liner/setting tool, and indeed to the surrounding rock formations, which can cause serious damage.
Similar such problems are encountered where other downhole tools are provided with ball seats that shear out at such high pressures, and indeed other types of ball seats and balls which operate at high pressures. Such alternative structures include those with deformable balls or ball seats, which permit blow-through of a ball at determined pressures. Typical such alternative tools include those utilised to selectively circulate fluid into an annulus between a workstring and the wall of a casing, to assist in a casing cleaning procedure, although it will be understood that many different types of downhole tool are activated in this way.
It is therefore amongst the objects of embodiments of the present invention to obviate or mitigate at least one of the foregoing disadvantages.
According to a first aspect of the present invention, there is provided a ball seat assembly comprising:
Providing a ball seat assembly where the ball seat is moveable to a retracted position, facilitating passage of the ball through the ball seat and thereby re-opening fluid flow through the body bore, in response to a reduction in the fluid pressure force acting on the ball seat, offers significant advantages over prior ball seat assemblies. This is because it is not necessary to expose the ball to high pressures in order to re-open flow through the body bore. This reduces the risk of damage both to downhole components and surrounding geological formations.
The ball seat may be movable to the retracted position by a subsequent reduction in the pressure of fluid acting on the ball and thus on the ball seat.
The ball seat may be moveable from the extended position to the retracted position in an uphole direction. It will be understood that references herein to movement in an uphole direction are to movements within a borehole in a direction towards the surface. References to movement in a downhole direction should therefore be construed accordingly. The ball may be adapted to be passed down into the body bore in a first axial direction, and the ball seat may be selectively moveable relative to the body bore in a second axial direction opposite to said first axial direction between the extended and retracted positions.
The body may comprise a recess, channel, groove or the like which may extend around an internal surface of the body and which may be adapted to receive at least part of the ball seat when the ball seat is moved from the extended position to the retracted position.
The assembly may comprise a control mechanism for controlling movement of the ball seat from the extended position to the retracted position, to selectively permit passage of a ball along the body bore and thus to selectively re-open fluid flow therethrough. The control mechanism may be activatable to move the ball seat from the extended position to the retracted position in response to the reduction in the fluid pressure force applied to the ball seat and thus to the ball when seated on the ball seat in the extended position.
The control mechanism may comprise a biasing member such as a spring for exerting a biasing force on the ball seat, to bias the ball seat towards the retracted position.
The control mechanism may comprise a restraint for restraining the ball seat against movement relative to the body bore. The restraint may be adapted to release the ball seat for movement relative to the body bore on exposure of the ball seat to a fluid pressure force at or above a determined level. It will be understood that this fluid pressure force will depend upon the pressure of fluid acting on the ball and the dimensions of the ball seat and the ball. The restraint may take the form of a shear pin and may be rated to shear at or above a fluid pressure force acting on the ball seat which is greater than a typical range of operating pressures experienced downhole. This may prevent premature release of the ball seat for movement relative to the body bore.
The ball seat may comprise at least one ball seat element which may be radially moveable relative to the body bore between the extended and retracted positions. In an embodiment of the invention, the ball seat comprises a plurality of ball seat elements which together define or describe the ball seat. The ball seat elements may take the form of arcuate dogs, the dogs together defining a generally annular ball seat when the dogs are in their respective extended positions. In the extended position of the ball seat, the body may support the ball seat, and the body may comprise a body portion defining a shoulder or the like adapted to abut the ball seat, to support and maintain the ball seat in the extended position. The body portion adapted to abut the ball seat may define or describe an internal diameter which, when the ball seat is located axially overlapping or adjacent to said portion, maintains the ball seat in the extended position defining the restriction.
The control mechanism may comprise a support member such as a sleeve or a cage coupled to the ball seat such that movement of the ball seat from the extended position to the retracted position is governed by the support member. Where the assembly comprises a biasing member for urging the ball seat towards the retracted position, the biasing member may be adapted to act on the support member to thereby urge the ball seat towards the retracted position. The support member may comprise at least one aperture for receiving the ball seat and, where the ball seat comprises a plurality of ball seat elements, may comprise an aperture for each ball seat element, which ball seat elements may be mounted for radial movement relative to the body bore within the respective apertures.
The ball seat assembly may comprise a collet comprising a plurality of sprung or resilient collet fingers, the collet fingers together defining the ball seat. The collet fingers may each comprise finger portions having inner surfaces each defining part of a surface of the ball seat and adapted to abut the ball. The finger portions may be of a larger radial thickness relative to at least an adjacent portion of the fingers, and may be adapted to engage in the recess or the like in the body when the ball seat is moved to the retracted position. It will therefore be understood that the finger portions of the collet fingers may be adapted to spring out into the recess to restrain the ball seat in the retracted position. The finger portions may comprise surfaces which are inclined, in use, in a downhole direction to resist movement of the ball seat from the retracted position.
The control mechanism may comprise an indexing arrangement including an indexing sleeve coupled to the ball seat, the indexing sleeve comprising an indexing channel extending at least part way around a circumference of the sleeve, and at least one indexing pin adapted to engage within the indexing channel. The indexing sleeve may be mounted for movement within the body of the assembly and the pin may be mounted extending through a wall of the body. In this fashion, movement of the indexing sleeve relative to the body may be controlled by an interaction between the pin and the channel. The indexing channel may comprise a plurality of axially and/or circumferentially spaced detent positions, and may comprise at least one first detent position in which the ball seat is in the extended position; and at least one second detent position, axially and/or circumferentially spaced from the first detent position, in which the ball seat is in the retracted position. The indexing channel may comprise at least one further detent position, which may be an intermediate detent position. The further detent position may be axially and/or circumferentially spaced from the first and/or second detent positions. In the further detent positions, the ball seat may be in a further position, in which the ball seat maintains a restriction to passage of a ball through the body bore, and said further position of the ball seat may be axially spaced from the further extended position. Location of the ball seat either at the first extended position, the further position or at a location between the two positions may be controlled by the fluid pressure force exerted on the ball seat.
The ball seat assembly may be for a downhole tool and, in a preferred embodiment, may be for a tubing setting tool, particularly a liner setting tool.
It will be understood that when, in use, a ball is landed on the ball seat when in the extended position, the ball may be sealingly received by the ball seat to prevent further flow through the body bore past the ball seat. Alternatively, the ball may be received by the ball seat in such a fashion as to substantially prevent fluid flow past the ball seat, but such that fluid communication between a portion of the body bore above the ball seat and a portion below the ball seat may still be permitted. References to permitting passage of the ball through the body bore to re-open fluid flow therethrough should be construed accordingly.
According to a second aspect of the present invention, there is provided a downhole tool comprising a ball seat assembly according to the first aspect of the present invention.
Preferably the downhole tool is a tubing setting tool and may take the form of a liner setting tool.
According to a second aspect of the present invention, there is provided a method of controlling fluid flow through a hollow body, the method comprising the steps of:
The method may be a method of hanging a tubing in a downhole environment, and may be a method of hanging a liner from a larger diameter tubing in a wellbore, which larger diameter tubing may be a casing.
The method may comprise providing a downhole tool, in particular a setting tool, defining the hollow body and controlling fluid flow through the hollow body of the setting tool in order to hang the tubing. The downhole tool may be coupled to the tubing and may serve for actuating a tubing hanger on the tubing. The hanger may be activated by raising fluid pressure in the tool above the ball to activate the hanger, and then reducing the fluid pressure to facilitate movement of the ball seat to the retracted position, to re-open flow.
Alternatively, the method may be a method of selectively activating a downhole tool for carrying out a downhole procedure, and may be a method of selectively activating one or more tools selected from a group comprising a cleaning tool, a packer, a milling tool and a circulation tool. The downhole tool may be activated in a similar fashion to the hanger discussed above.
The method may comprise raising a fluid pressure force acting on the ball after the ball has been brought into abutment with the ball seat, to carry out a further downhole procedure/operation, and/or to release a restraint (such as a shear pin) restraining movement of the ball seat relative to the body bore. This may be achieved by raising the pressure of fluid in the body bore above/upstream/uphole of the ball. Following carrying out of the downhole procedure and/or release of the restraint, the fluid pressure force acting on the ball may be lowered, by lowering the pressure of fluid in the body bore above/upstream/uphole of the ball, to facilitate movement of the ball seat to the retracted position.
According to a fourth aspect of the present invention, there is provided a ball seat assembly comprising:
According to a fifth aspect of the present invention, there is provided a method of controlling fluid flow through a hollow body, the method comprising the steps of:
It will be understood that, whilst a ball seat assembly comprising a ball seat defining a restriction to passage of a ball is defined herein, other types of seat assembly, defining restriction to passage of alternative restriction members, are encompassed. Accordingly, a valve seat assembly comprising a valve seat defining a restriction to a valve member may be provided. The valve may be a dart or other suitable member. A corresponding downhole tool and method may also be provided.
Embodiments of the present invention will now be described, by way of example only.
Turning firstly to
In use, when the ball 20 is landed on the ball seat 18 in its extended position, the ball 20 restricts fluid flow through the body bore 16, causing an increase in a fluid pressure force acting on the ball seat 18 for a given fluid pressure in the bore 16 above the ball 20. As will be described in more detail below, a subsequent reduction in the fluid pressure force acting on the ball seat 18 facilitates movement of the seat from the extended position shown in the upper half of
The setting tool 10 and the ball seat assembly 12 will now be described in more detail with reference also to
The work string 19 carrying the liner 22 is run-in to the wellbore 24 with the setting tool 10 in a run-in configuration, where the ball seat 18 is held in the position shown in the upper half of
To achieve this, the ball 20 is dropped into the work string 19 and passes under gravity and in fluid flowing down through the work string into the setting tool 10. The ball 20 is typically of 2⅛ inch diameter, whilst in the extended position, the ball seat 18 describes a maximum clearance of 2 inches. Accordingly, the ball comes to rest on a seating surface 48 of the ball seat 18. This restricts further flow down through the body bore 16; indeed, the close fit between the ball 20 and the seat 18 ensures that substantially all fluid flow down the body bore 16 past the seat 18 is arrested. For a given fluid pressure in the work string 19, this results in an increase in the fluid force acting on the ball 20 and thus on the ball seat 18. The fluid in the work string 19 above the ball seat 18 can then be pressured-up to activate the liner hanger 36 and thus to bring the slips 38 into engagement with the casing inner surface 40. This is achieved by fluid communication between the setting tool 10 and the hanger 36 through ports 41 (one shown) in the running tool 31. The liner 22 is thus now suspended from the casing 26, and the running tool 31 can be released from the liner 22, the packer 32 deactivated, and the string 19 returned to surface.
During setting of the hanger 36, the pressure of the fluid in the work string 19 above the ball seat 18 is raised above 1000 psi. Above 1000 psi, a number of shear pins 50 (two shown in
Following setting of the liner hanger 36, the fluid pressure in the work string 19 is reduced significantly, and the spring 54 urges the support sleeve 52 in an uphole direction (to the left in
A suitable ball catcher (not shown) may be provided further down the work string 19 for catching the ball 20, or the ball 20 may carry on down the workstring 19 to a further tool provided deeper in the well, or indeed to a further tool provided within the liner 22. For example, the ball may continue down the liner 22 to operate a differential fill float collar or float shoe (not shown) from a “fill” configuration to a “float” configuration, prior to cementing the liner 22.
The structure and method of operation of the downhole tool 10 will now be described in more detail.
The ball seat 18 comprises three ball seat elements in the form of arcuate dogs 56a, 56b and 56c, best shown in the sectional view of
The support sleeve 52 includes a shoulder portion 60 having a circumferentially extending channel 62 in which the shear pins 50 are engaged, to lock the support sleeve 52 against movement during run-in of the setting tool 10, holding the dogs 56 in their extended positions. The spring 54 is located between an end face 64 of the shoulder portion 60 and a shoulder 66 defined by a main portion 68 of the tool body 14. Ports 70 in the support sleeve 52 prevent hydraulic lock by allowing pressure equalisation between a chamber 72 in which the spring 54 is located and the body bore 16.
The body 14 also includes an upper sub 74 which is threaded to the main portion 68, and the upper sub 74 and main portion 68 define respective female box and male pin connectors, for connecting the setting tool 10 into the work string 19. The upper sub 74 includes a shoulder portion 80 having an abutment surface 82 which, when the sleeve 52 is in the position shown in the upper half of
In use, in the run-in configuration of the setting tool 10 shown in the upper half of
Following setting of the hanger 36, the fluid pressure force acting on the seat 18 can be reduced by bleeding off pressure in the work string 19. As the shear pins 50 have now been sheared, the spring 54 acts to urge the support sleeve 52 in an uphole direction. As the sleeve 52 moves uphole, it carries the seat dogs 56. The axial length of the upper sub shoulder portion 80 and the dimensions of the dogs 56 are selected such that the dogs 56 can only move out to their retracted positions, shown in the lower half of
Accordingly, it is necessary to greatly reduce pressure of fluid in the work string 19 in order that the dogs 56 be carried a sufficient distance uphole to move out into the recess 86.
On reaching this position, the ball 20 exerts a force on the dogs 56 to urge them radially outwardly into the recess 86, and the ball 20 is then released to pass on through the body bore 16, as described above. Magnets 94 in each dog 56 then hold the dogs 56 in the recess 86, effectively locking the dogs out and securing the support sleeve 52 against return movement against the biasing force of the spring 54.
Turning now to
The assembly 12′ includes a control mechanism 51′ having a support sleeve 52′ which carries a collet 96 at an upper end thereof. The collet 96 includes a number of sprung collet fingers 98, each of which includes a finger portion 100 of enlarged radial thickness at an end thereof.
A body 14′ of the setting tool 10′ includes a main portion 68′, an upper sub 74′ and an intermediate portion 102 which couples the upper sub 74′ to the main portion 68′. The intermediate portion 102 includes a shoulder 104, and the tool 10′ includes a shoulder portion 80′ defined by a short sleeve located between the shoulder 104 and an end 106 of the upper sub 74′. The shoulder portion 80′ includes an abutment surface 82′ and a shoulder 108, and serves for maintaining a ball seat 18′ defined by the collet finger portions 100 in an extended position, shown in the upper half of
A portion 112 of the support sleeve 52 carries an indexing sleeve 114, which defines a number of indexing channels (two shown) 116 that extend part way around a circumference of the sleeve 114. A number of indexing pins 118 (two shown) are located extending through a wall 120 of the body main portion 68′ and locate in a respective indexing channel 116. Interaction between the pins 118 and the channels 116 controls axial and rotational motion of the support sleeve 52 relative to the tool body 14′ and thus within a bore 16′ of the tool.
The indexing channel 116 defines two first detent positions 122 and a second detent position 123, as well as two intermediate detent positions 124. These are best shown in the developed circumferential view of
In use of the tool 10′, the tool is made up to a work string such as the work string 19 in place of the tool 10 shown in
When this fluid pressure force has been raised to a sufficient level, by increasing the pressure of fluid in the work string 19, the support sleeve 52 is carried axially downwardly and is rotated such that the index pins 118 now reside in the first one of the intermediate detent positions 124. Further downward and rotational motion of the support sleeve 52 is prevented by engagement of the pins 118 in the intermediate detent positions 124. Also, the shoulder 108 on shoulder portion 80′ arrests further downhole movement. The fluid pressure force is then reduced by bleeding off fluid pressure, and the spring 54′ urges the support sleeve 52 uphole. However, the collet finger portions 100′ are restricted from moving to their retracted positions.
This is because the indexing pins 118 now reside in the second one of the first detent positions 122, preventing movement of the support sleeve 52 to a position where the collet finger portions 100 are retracted.
By this mechanism, premature activation of the setting tool 10′ is prevented. It is therefore necessary to carry out a further pressure cycle, moving the indexing pins 118 from the second one of the first detent positions 122 to the second one of the intermediate detent positions 124. When fluid pressure is then again bled off, the pins 118 move into respective long arms 128 of the indexing channel 116, and come to rest in the second detent position 123. As with the tool 10 described above, this is only possible when the fluid pressure is bled to a sufficiently low level which, again, is set to be around 50 psi, according to the dimensions and rating of the spring 54′.
When trailing edges 90′ of the collet finger portions 100 pass beyond the side wall 92 of the recess 86, the sprung collet fingers 98 snap radially outwardly such that the finger portions 100 now reside within the recess 86′. The ball 20′ is then released and can pass through the body bore 16′ and out of the tool 10′. This is best shown in
It will readily be understood by persons skilled in the art that the tools 10 and 10′ may be utilised in a wide range of downhole operations/procedures, and thus for activating a wide range of alternative downhole tools. For example, the tools 10 and 10′ may be provided as part of a tool string carrying a fluid actuated circulation tool; a cleaning tool; a valve assembly; a perforation tool; a packer; a milling tool or the like or any combination thereof.
Various modifications may be made to forgoing without departing from the spirit and scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0706350.6 | Mar 2007 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/GB2008/000904 | 3/14/2008 | WO | 00 | 2/4/2010 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2008/119931 | 10/9/2008 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4502542 | Thurman et al. | Mar 1985 | A |
| 4729432 | Helms | Mar 1988 | A |
| 5181569 | McCoy et al. | Jan 1993 | A |
| 7469744 | Ruddock et al. | Dec 2008 | B2 |
| 7637323 | Schasteen et al. | Dec 2009 | B2 |
| 20110315389 | Crider et al. | Dec 2011 | A1 |
| 20110315390 | Guillory et al. | Dec 2011 | A1 |
| Entry |
|---|
| International Search Report from PCT/GB2008/000904 dated Jul. 7, 2008 (3 pages). |
| Written Opinion from PCT/GB2008/000904 dated Jul. 7, 2008 (7 pages). |
| Number | Date | Country | |
|---|---|---|---|
| 20100132954 A1 | Jun 2010 | US |
