WO2008146012A2

WO2008146012A2 - Downhole apparatus

Info

Publication number: WO2008146012A2
Application number: PCT/GB2008/001852
Authority: WO
Inventors: Andrew Phillip Chuchill
Original assignee: Churchill Drilling Tools Limited
Priority date: 2007-06-01
Filing date: 2008-05-30
Publication date: 2008-12-04
Also published as: WO2008146012A3; GB0710480D0

Abstract

A downhole apparatus comprises a tubular body including a seat, and an actuating member including a wiper dart and an extrudeable portion adapted to mate with the seat. When a first pressure is applied across the member a function may be performed. Application of a higher second pressure causes the portion to be extruded through the seat.

Description

DOWNHOLE APPARATUS

FIELD OF THE INVENTION

This invention relates to a downhole apparatus, and in particular to an apparatus adapted to be activated or actuated by creation of a pressure differential across an actuating member which is pumped or otherwise translated into the body of the apparatus.

BACKGROUND OF THE INVENTION Operators in the oil and gas exploration and production industry utilise various tools in which a ball is dropped or pumped through a tubular string of pipe to land on a ball seat, closing or partially closing the string bore. This permits a differential pressure to be created across the ball, which pressure may be utilised to, for example, open a bypass port. The ball may subsequently be forced past the seat, by deformation of one of the ball or seat, by applying a higher differential pressure across the ball. Examples of such tools are described in US Patents Nos 4,889,199 and 6,923,255, and WO 02/068793 all to Lee, and WO 2004/088091 and WO 02/061236, both to Telfer et al.

The applicant has proposed alternative tools, in which nozzled sleeves and other flow restrictions may be utilised to permit selective actuation of downhole tools as described in applicant's International Patent Applications Nos. PCT/GB2000/02712, PCT/GB 2004/004840, PCT/GB 2004/004852 and PCT/GB2006/004400. SUMMARY OF THE INVENTION

According the present invention there is provided downhole apparatus comprising: a tubular body including a seat; and an actuating member including an axially extending extrudeable portion with a leading end defining a profile adapted to mate with the seat, whereby a first force applied to the member allows a function to be performed and a higher second force causes the portion to be extruded through the seat.

According to another aspect of the present invention there is provided a method of operating a downhole apparatus, the method comprising: providing an actuating member including an axially extending extrudeable portion with a leading end defining a profile; pumping the member through a tubular string; landing the profile on a seat in the string; providing a first force to the member necessary to perform a function; and providing a higher second force to extrude the member through the seat.

The first force will typically be a fluid pressure force, for example a fluid pressure differential acting across the member.

The second force may be a fluid pressure force, a mechanical force, an impulse, or result from a combination forces. For example, the second force may be applied, at least in part, by a fluid propelled member impacting on the actuating member. The fluid propelled member may be a generally cylindrical member, which member may be of a diameter only slightly smaller than the seat and the body internal diameter, and will thus act as a piston. Also, if the fluid propelled member is pumped into the body through a tubular string the fluid propelled member will land on the actuating member and the momentum of the following column of fluid will act upon the actuating member, producing a very significant impulse.

In other embodiments, the second force may be applied immediately following the application of the first force. For example, the member may be pumped into the string at speed, apply a first force on landing on the seat, immediately followed by a larger second force created by the momentum of the column of fluid following the member. In another aspect of the invention, the force applied to the member may be substantially constant, but the time delay afforded between the member landing on the seat and being extruded through the seat is sufficient to perform the function. The provision of an axially extending extrudeable portion offers numerous advantages over the prior art arrangements, such as extrudeable balls. For example, it is possible to provide a secure mating arrangement between a profile and a seat where the seat is only very slightly smaller than the profile. Thus, the loss in internal diameter by provision of the seat may be minimal, such that access below the seat may be maintained essentially unobstructed and the seat induces little if any pressure loss in fluid flowing through the seat, and subsequently exerts little if any force on the seat.

The pressure or force necessary to extrude the portion through the seat may be controlled or varied by at least one or more of: the length of the portion, the difference in dimension or interference between the portion and the seat, the material used to form the portion, and the surface configuration of the portion. The pressure or force necessary to extrude the portion through the seat may also be determined with a degree of accuracy, permitting a greater degree of control in the operation of the apparatus. The axially extending extrudeable portion may be substantially cylindrical. The portion may include a conical or tapered surface portion, a corrugated portion, or a stepped portion.

The portion may be employed to create a lock between the actuating member and the seat, for example a tapered portion may create a taper lock. The actuation member may also be configured to create a lock between two relatively moveable parts, for example by engaging one part with a first area of the axially extending extrudeable portion and another part with a second area of the portion.

A stepped extrudeable portion may be utilised to provide a step change in the force that is required to extrude the portion from a first mating position to a second mating position.

The portion may comprise a more ductile or softer material than the seat. The portion may comprise any appropriate material, including one or more of plastics or metal. If metal, the portion may comprise aluminium or an aluminium alloy. The portion may be adapted to undergo elastic deformation, or may undergo plastic deformation, while being extruded through the seat. Where a metal portion is utilised, the portion is likely to undergo a combination of elastic and plastic deformation.

The extrudeable portion may be adapted to be replaceable, such that following use a portion that has been extruded may be removed and replaced and the actuating member then reused. The portion may feature a threaded part to engage a corresponding threaded part on the body of the actuating member.

In embodiments of the invention, using 2 !4" diameter axially extending extrudeable portions, interference fits of 1-5 thousandths of an inch of up to ³A" length, may provide extrusion pressures, equivalent to the second force, of 1000- 8000psi. This is a workable range of pressure in many downhole operations and was achieved using an aluminium alloy portion and a hardened steel seat. Even smaller interference fits of 0.5-1" thousandths may be utilised when using a steel extrudeable portion on a hardened steel seat. Alternatively, if softer or more ductile materials are utilised, such as plastics, or softer metals are used to form the portion, a larger interface may be useful or required.

Some of the advantages provided by this aspect of the invention may also be available in an apparatus in accordance with an alternative aspect of the invention where the actuating member takes the form of a ball of relatively hard material, rather than the relatively soft nylon balls of prior art arrangements. The actuating member may be adapted to close the body bore completely on engaging the seat. The profile or portion may form a seal with the seat, facilitating creation of a pressure differential across the member.

The body may be adapted to be functioned on two or more occasions, and two or more actuation members may be passed through the body. The functions may be repetitions of the same functions, or may differ. The functions may be of a cyclic nature, for example a first function, followed by a second function, and then followed by a third function, which functions may then be repeated. An actuation member may be adapted to remain in the body, and such an actuation member may be adapted to resist extrusion through the seat. Thus, the body may be provided in combination with two or more actuation members, which members may be of the same or different construction.

The body may comprise a valve arrangement including one or more ports in the body wall and configurable to permit, for example, fluid to flow between the body and a surrounding annulus. The ports may be initially covered or filled. This minimises the likelihood of foreign material gaining access to the ports and potentially interfering with the functioning of the apparatus. For example, many downhole tools incorporate sliding parts with small clearances between the parts. The material normally present in drilling fluid passing up the annulus to surface may find its way into the spaces between the parts and pack-out the spaces or otherwise restrict movement of the parts, preventing operation of the apparatus. Similarly, the presence of certain downhole materials may cause or accelerate corrosion or degradation of parts, and the presence of corrosion may restrict movement and prevent or hinder operation of an apparatus. The ports may be covered or filled with a bung or the like, comprising, for example, a polymeric material. Alternatively, the ports may be filled with a suitable material, such as a two-part resin. The bung may comprise a relatively soft or light material, such that the bung will be carried to surface by the drilling fluid and will not damage or jam any other apparatus. The bung may be brightly coloured or otherwise distinguishable from the drilling fluid or drill cuttings; the bung may be readily identified on reaching the surface, and thus provides an indication that the apparatus has been activated or actuated.

The apparatus function may be operatively associated with the seat, for example application of a fluid pressure induced force across the actuating member, and transferred to the seat, may induce translation of the seat and the part of the body on which the seat is formed or mounted. Such movement may actuate, produce or result in an apparatus function, for example actuate a valve, operate a switch, actuate a coupling, and so on. Alternatively, or in addition, the apparatus function may be independent of the seat, for example an elevated fluid pressure in a tubular string above the actuating member may produce a differential pressure between a string bore and a surrounding annulus. Such a pressure differential may be utilised to actuate a differential piston. Alternatively, the function may simply be a pressure test, for example to test the pressure integrity of a tubular string above the apparatus, or the drifting of the string.

The body may include a sleeve and the seat may be operatively associated with a sleeve, indeed the seat may be formed on the internal diameter of a sleeve. The sleeve may be adapted for axial movement such that the sleeve moves downwards in response to a force applied to the seat by the actuating member. The sleeve may be biased upwards by a spring or the like. The movement of the sleeve may be controlled by means of a cam or the like. For example, one of the sleeve or the cooperating part of the body may feature a cam track and the other part a follower pin. In other aspects of the invention a member of a form other than a sleeve may be operatively associated with the seat.

A catcher may be provided for receiving the actuating member after the member has been pushed through the seat, and may allow fluid to flow around the member, thus permitting, for example, normal fluid circulation through a drill string. The catcher may be capable of accommodating a plurality of actuating members. The catcher may be provided towards a distal end of a string, facilitating access to the string bore between the catcher and the seat.

The actuating member may be adapted to be pumped into the body, for example the member may include a wiper dart. A dart, or an equivalent structure, also facilitates centralising the extrudeable portion as is travels through a string, reducing the likelihood of damage to the portion, which may be of a relatively soft material.

According to a further aspect of the present invention there is provided downhole apparatus comprising: a tubular body including a seat; and an actuating member including a wiper dart and an extrudeable portion adapted to mate with the seat, whereby a first pressure applied across the member allows a function to be performed and a higher second pressure causes the portion to be extruded through the seat.

According to a still further aspect of the invention there is provided a method of operating a downhole apparatus, the method comprising: providing an actuating member including a wiper dart and an extrudeable portion; pumping the member through a tubular to engage with a seat; applying a first pressure above the member to perform a function; and applying a higher second pressure to extrude the member through the seat.

The various optional features of the first two aspects of the invention described above may equally be utilised in combination with these or other aspects of the invention. Furthermore, the optional features of the second two aspects of the present invention may be utilised in combination with the first two aspects, or other aspects, of the present invention.

The extrudeable portion may take a similar form to the portion of the aspects described above or may take a different form, for example the portion may be an extrudeable or deformable ball.

The wiper dart may include a plurality of sealing members, which members may define the same or different diameters.

Due to the presence of the wiper dart in the actuating member, the member will tend to require a pressure differential across the member to translate the member through a tubular, although even a relatively small pressure differential will normally be sufficient to displace the actuating member. The wiper dart also permits the position of the member in a tubular string to be predicted with a degree of accuracy, by measuring the volume of fluid pumped into the string behind the dart. Thus, the member may be pumped relatively rapidly into the string and then slowed a short distance from the seat.

Where the apparatus includes a bypass arrangement, a function of the apparatus being the opening of bypass ports, the presence of the wiper dart allows lost circulation material (LCM) to be pumped into the string directly behind the dart.

According to a still further aspect of the present invention there is provided downhole apparatus comprising: a tubular body including a seat of a first diameter; and an actuating member of a larger second diameter adapted to mate with the seat and to be extrudeable through the seat, whereby the second diameter is less than 1/8" larger than the first diameter.

According to a yet further aspect of the present invention there is provided a downhole apparatus comprising a tubular body having a wall defining at least one port, the port being initially filled with a removable bung. The bung may take any appropriate form, and may include a polymeric material. The bung may be provided in a form suitable to be inserted in the port or may be formed or moulded in the port. For the latter, the bung may be formed of a wax, lubricious resin or other low melting point material which facilitates the filing of the port, but which may be selected to have a melting temperature which is higher than the temperatures likely to be encountered in use. The bung may seal the port, or may merely partially occupy the port to restrict or limit access of external material to the port.

The port may be intended to permit fluid flow through the wall, or may provide passage for a blade or other member, such as an extendable cutter. Although the above aspects are described with reference to downhole applications, it will be recognised that the various aspects of the invention may find application in other situations, including pipelines and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Figure 1 is a sectional view of elements of a downhole apparatus, in the form of a bypass tool, in accordance with a first embodiment of the present invention; Figures 2 and 3 illustrate steps in the operation of the apparatus of Figure 1 ;

Figure 4 illustrates a downhole apparatus, in the form of a bypass tool, in accordance with a second embodiment of the present invention;

Figures 5 and 6 illustrate steps in the operation of a downhole apparatus, in the form of a bypass tool, in accordance with a third embodiment of the present invention; Figure 7 is an enlarged view of a mating profile and seat of the tool of Figures

5 and 6;

Figures 8 to 10 illustrate steps in the operation of a downhole apparatus, in the form of a bypass tool, in accordance with a fourth embodiment of the present invention; and Figure 11 is an enlarged view of a mating profile and seat of the tool of

Figures 8 to 10.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is first made to Figure 1 of the drawings, which illustrates three primary elements of a downhole apparatus, in the form of a bypass tool 10, in accordance with a first embodiment of the present invention. The tool 10 comprises a generally tubular main body 12 provided with conventional phi and box connections to allow the body 12 to be incorporated at an appropriate point in a drill string. As will be described, the tool 10 is operable to provide selective bypass, that is to allow drilling fluid to be passed from the body 12 directly into an annulus surrounding the drill string, without the drilling fluid having to pass the full length of the string, exit the string through the bottom hole assembly (BHA) and pass up through the annulus to the body location. The tool 10 also comprises an actuating member 14, which combines a wiper dart 16 and a deformable ball 18. As will be described, the diameter of the ball 18 is selected such that the ball will land on a seat 20 defined within the main body 12. The tool 10 further comprises a catcher sub 22, which is, like the main body 12, adapted to be incorporated in a drill string. In use, the catcher 22 will typically be located towards the distal end of the drill string, below the main body 12. As noted above, the body 12 is generally cylindrical and features conventional pin and box end connections. The body wall 26 also defines a flow port 28. An axially movable valve sleeve 30 mounted within the body 12 initially closes the flow port 28, seals 32 provided on the internal diameter of the body 12 and engaging the outer diameter of the valve sleeve 30 ensuring that there is no leakage between the main body bore and the surrounding annulus when the valve sleeve 30 is in the closed position. Also, it will be noted from Figure 1 that the flow port 28 is initially occupied by a bung 34 sized to fit snugly within the flow port 28, and also featuring peripheral seals 36.

The valve sleeve 30 also features a port 38 which may be aligned with the body port 28 to allow fluid communication between the main body bore and . the surrounding annulus, as will be described. The valve sleeve 30 is restricted to move in an axial direction by an alignment pin 40, and a compression spring 42 acting between opposing shoulders on the body and sleeve urges the sleeve 30 upwardly, to the closed position. At its upper end, the sleeve 30 is held in place by a threaded retainer 44 which engages a corresponding internal thread on the body wall.

The ball seat 20 is defined by an insert 46 which fits within the sleeve 30, and is located a short distance below the valve sleeve port 38.

As noted above, the actuating member 14 comprises a wiper dart 16 and a deformable ball 18. The wiper dart elements of the member 14 features three axially spaced cup seals, these being a larger diameter leading and trailing seal 50, 52 and a smaller diameter intermediate seal 54. The actuating member 14 is intended to be pumped into the drill string and into the body 12, and the seals 50, 52, 54 ensure fluid being pumped behind the member 14 remains above the member 14. The smaller diameter intermediate seal 54 ensures that a seal is maintained as the member 14 passes through smaller diameter sections of the drill string, such as at connections between drill pipe sections. The ball 18 is formed of nylon, and is mounted to the trailing end of the wiper dart 16. The diameter of the ball 18 is significantly larger than the inner diameter of the seat 20.

The catcher sub 22 comprises a tubular body 58 with a larger diameter upper section 60 which accommodates a tube 62 for receiving one or more actuating members 14. The tube 62 is mounted between flanges 64, 65 which include bypass passages 66, 61 such that, when an actuating member 14 is located within the tube 62, the fluid may still flow passed the member 14. In particular, the fluid may pass from the upper bypass passage 66, through the annulus 68 between the tube 62 and the body 58, and then pass through the lower bypass passage 67. The tube 62 may define a seat which is positively engaged by the ball 18.

Reference is now also made to Figures 2 and 3 of the drawings, which illustrate steps in the operation of the tool 10. The main body 12 and the catcher sub 22 will be incorporated in a drill string at appropriate locations, that is the catcher sub

22 typically being located towards the distal end of the string, while the main body 12 may be located at an intermediate point in the string, or more typically also towards the distal end of the string, a short distance above the catcher sub 22. The drilling operation may proceed as normal, with the tool 10 being effectively dormant until it is actuated, as described below.

The tool 10 might be activated if it was desired to provide fluid bypass, that is it is desired to pass drilling fluid directly into the annulus, without passing the fluid through the bottom hole assembly (BHA), to clear cuttings from the annulus.

Alternatively, if mud losses are encountered, it may be desired to pump lost circulation material (LCM) into the annulus.

To actuate the tool, the actuating member 14 is inserted into the string on surface and then pumped down through the drill string towards the body 12. As the wiper dart 16 forms a sliding, sealing contact with the internal diameter of the string, the fluid pumped behind the actuating member 14 is isolated from the fluid being displaced by the actuating member 14 as the member 14 is pushed through the string.

Also, the relatively low weight of the actuating member, and the friction between the wiper dart seals 50, 52, 54 and the string bore wall, are such that the actuating member 14 will not pass through the string under the influence of gravity alone; the actuating member 14 will only translate through the string as fluid is being pumped into the string behind the member 14. Although this feature may be considered a disadvantage in situations where it is not possible to circulate fluid, or in vertical holes where gravity alone will carry conventional occluding balls into a bypass tool without pumping, it is possible to pump the member 14 into a hole at any angle with even very limited fluid circulation. It is also relatively easy for an operator to pinpoint the location of the actuating member 14 in the drill string, with reference to the volume of fluid that is pumped into the string behind the member 14. In practice, the actuating member 14 may be moved through the string relatively quickly, until the operator identifies that the member 14 is approaching the body 12, at which point the pump rate may be lowered, such that the member 14 is moving relatively slowly as it passes into the body 12, minimising the risk of the member 14 being inadvertently pushed straight through the body 12.

The wiper dart 16 will pass through the retainer 44 and into the valve sleeve 30, and continue to pass through the valve sleeve 30 until the ball 18 lands on the seat 20. If necessary, the operator will then turn up the pumps on surface to provide a fluid pressure in the string bore sufficient to provide a fluid pressure differential across the ball 18 to apply a force through the valve sleeve 30, via the seat 20, sufficient to compress the spring 42.

The valve sleeve 30 will thus move downwardly within the body 12, until the valve sleeve port 38 is aligned with the body wall flow ports 28, as illustrated in Figure 2. As the ports 38, 28 are aligned, the fluid pressure in the drill string above the ball 18 will push the bungs 34 out of the ports 28, and fluid will then flow directly from the drill string into the annulus.

If desired, the operator may then increase the pump rate, to increase the flow rate of fluid through the string and into the annulus. If the pumps are turned off for any reason, the spring 42 will lift the valve sleeve 30 to close the ports 28 once more.

When the operator wishes to return to normal fluid circulation through the string, a further ball 70 is placed in the string at surface and pumped down into the body 12, as illustrated in Figure 3. The ball 70 is dimensioned to be smaller than the deformable ball 18, but is large enough to close the valve sleeve port 38, as illustrated in Figure 3.

On the ball 70 closing the port 38, a pressure differential is created across the ball 18. By increasing the pump pressure, it is then possible to extrude or force the ball 18 through the seat 20. Once the ball 18 has passed through the seat 20, the pressure differential across the wiper dart 16 will push the actuating member 14 down through the lower portion of the string until the member 14 enters the catcher sub 22.

Once the actuating member 14 has passed from the body 12, there will be no axial pressure differential acting across the valve sleeve 30, such that the spring 42 will raise the sleeve 30 to misalign the ports 38, 28. The smaller ball 70 will then pass downwardly through the string to land in the catcher sub 22 above the actuating member 14.

In the absence of the actuating member 14 within the valve sleeve 30, there is little or no pressure differential acting on the sleeve 30, such that the spring 42 will maintain the sleeve 30 in the closed position.

If, subsequently during the drilling operation, it is considered appropriate to provide fluid bypass once more, a second actuating member 14 may be pumped into the string, and the operation repeated.

Reference is now made to Figure 4 of the drawings, which illustrates the body 12 after a different actuating member 80 has landed on a seat 20a of larger diameter than the seat 20 described above. The actuating member 80 comprises a wiper dart 16 but, rather than a deformable ball 18, a generally cylindrical deformable member 82 is provided to mate with the seat 20a. The leading end of the member 82 is generally conical, and features a profile 84 adapted to engage with the seat 20a. When the elevated differential pressure is applied across the member 80, to push the member 80 through the valve sleeve 30, the cylindrical deformable member 82 must be extruded through the seat 20a. The force necessary to extrude the member 82 through the seat is controllable in a number of ways, including: the difference between the outside diameter of the member 82 and the inside diameter of the seat 20a, the length of the member 82 which must be extruded, and the material which forms the member 82. Clearly, the greater the difference in diameter between the seat 20a and the member 82, the longer the member 82, and the less ductile the material which forms the member 82, the greater the force necessary to extrude the member 82 through the seat 20a. By appropriate selection of cylindrical member 82 material and dimensions it is possible to provide an actuating member 80 which will be extruded past the seat 20a by a force comparable to the force necessary to extrude the actuating member 14 through the seat 20, as described above, despite the smaller degree of interference between the seat 20a and deformable member 82 compared to the seat 20 and the ball 18. This offers the significant advantage of allowing provision of a larger diameter seat 20a, which minimises pressure losses and provides minimal restriction to access below the tool.

Reference is now made to Figures 5, 6 and 7 of the drawings, which illustrate steps in the operation of a downhole apparatus, in the form of a bypass tool 90, in accordance with a third embodiment of the present invention. The tool 90 features a main body 92 which is similar in many respects to the main body 12 described above. However, in the tool 90, the seat 94 (see Figure 7) is defined within the valve sleeve 96.

In addition, the actuating member 98 features a deformable member 100 at the leading end of the wiper dart 102, rather than at the trailing end of the wiper dart, as in the previous two embodiments. This offers particular advantages when the tool 90 is being used in spotting lost circulation material (LCM). As will be understood by those of skill in the art, LCM is utilised to prevent or minimise losses of well fluid into permeable formations. Thus, LCM tends to feature materials such as blast- furnace slag, gypsum cement and the like, which it is preferable to isolate from sealing surfaces, such as the seat 94. By locating the deformable member 100 in front of the dart 102, any LCM being pumped into the string behind the dart 102 is kept clear of the member 100 and thus also the seat 94. The possibility of LCM becoming trapped between the member 100 and the dart 102 is also minimised. The operation of the tool 90 is similar to the tools described above, in that the actuating member 98 is pumped through the string into the valve sleeve 96. On the deformable member 100 landing on the seat 94, a pressure differential may be created across the actuating member 98, allowing the fluid pressure acting above the member 98 to translate the valve sleeve 96 downwardly, to align the flow ports. In this embodiment, the deformable member 100 is formed of an aluminium alloy, and lands on a hardened steel seat 94, as illustrated in Figure 7 of the drawings. It will be noted that the deformable member 100 is provided with a thread for engaging the wiper dart, which allows the deformable member to be removed and replaced as necessary. It will also be noted from Figure 7 that the difference between the outer diameter of the deformable member 100 and the inner diameter of the seat 94 is relatively small, and smaller than the embodiments described above, in this case in the order of 1-5 thousands of an inch. Thus, it will be apparent that the seat provides little if any restriction to fluid flow through the main body 92 when the tool 90 is not in use. Also, the seat 94 provides little if any restriction to access below the seat 94.

One embodiment of the invention features a 3 thousands of an inch difference in diameter between the deformable member and the seat. This requires setting higher tolerances than are normally required for comparable apparatus (plus or minus 5 thousands of an inch for a normal engineering finish and perhaps plus or minus 1 thousands of an inch for a sealing face). Also, despite the minimal restriction in the flow area, the seat 94 may still be liable to erosion and wear, and given the very small differences in dimensions between the parts the resulting enlargement of the seat diameter could impact on the functionality of the apparatus. Accordingly, it is advisable to provide the seat with an appropriate wear and erosion-resistant finish, which may be achieved with, for example, an applied diamond-like coating, tungsten carbide or ceramic. It is also considered advantageous to provide the seat with a shallow lead-in angle, typically of 5 degrees or less. An alternative is to provide a seat configuration which will erode in a predictable manner, and which will accommodate a predetermined degree of wear, and thus maintain the desired degree of interference despite the leading edge of the raised wall portion retreating.

When it is desired to remove the actuating member 98 from the body 92, a cylindrical shell 104 is pumped through the drill string to land on the upper end of the actuating member 98, as illustrated in Figure 5. The shell 104 may be pumped through the string at a relatively high rate, such that the shell 104 will have significant momentum when it strikes the upper end of the actuating member 98. The momentum of the column of fluid following the shell 104 also creates a significant force on the member 98. It will be noted that the shell 104 is a close fit within the valve sleeve 96, and also serves to close the valve sleeve flow ports 106; the use of a shell 104 rather than a ball allows for the provision of more than one flow port. This ensures that, in addition to the forces mentioned above, there is also a significant pressure differential acting across the actuating member 98.

As a result of the above noted forces, a very significant force will act on the actuating member 98 on the shell 104 landing on the upper end of the member 98. This will extrude the aluminium alloy deformable member 100 through the hardened steel seat 94. The member 98 and the shell 104 are then carried down through the string to land in the catcher sub 108, as illustrated in Figure 6.

Reference is now made to Figures 8 to 11 of the drawings, Figures 8 to 10 illustrating steps in the operation of a downhole apparatus, in the form of a bypass tool 110, in accordance with a fourth embodiment of the invention, and Figure 11 being an enlarged view of a mating profile and seat of the tool 110. The tool 110 operates in a largely similar manner to the tools described above, with some notable differences, as will be described.

The tool 110 features a valve sleeve 112 which is axially movable within a main body 114, to selectively align flow ports 116, 117. However, the outside diameter of the valve sleeve defines a cam track 118, which co-operates with follower pins 120 mounted in the body 114. Also, the actuating member 122 (Figure 9) does not feature a wiper dart, only a bullet-shaped deformable member 124. As is more clearly seen in Figure 11 of the drawings, the deformable member 124 features a profile 126 towards the trailing end of the member 124, which is sized to provide an interference fit with a seat 128 formed on the internal diameter of the valve sleeve 112, above the valve sleeve flow ports 116.

Figure 8 illustrates the tool 90 in an initial, dormant configuration. In this configuration changes in fluid pressure within the body 114 will have no impact on the position of the valve sleeve 112. If it is desired to provide fluid bypass, the actuating member 122 is pumped through the string to land on the seat 128, as illustrated in Figure 11. It will be noted that there is only a very small degree of interference between the profile 126 and the seat 128, however this is sufficient to hold the actuating member 122 within the valve sleeve 112. It will be noted that the seat 128 is positioned above the valve sleeve flow ports 116, such that when the actuating member 122 lands in the sleeve 112 there is no fluid access to the flow ports 116.

If the fluid pressure in the string above the landed actuating member 122 is increased, the valve sleeve 112 is moved downwards, against the action of the spring 130, to the position shown in Figure 9. Further increasing the fluid pressure above the actuating member 122 above a predetermined level will then extrude the deformable member 124 through the seat 128. These increases in fluid pressure will typically occur instantaneously, immediately following the actuating member 122 landing on the seat 128. However, the provision of the axial interference profile between the deformable member 124 and the seat 128 prevents the actuating member 122 from passing through the seat 128 so quickly that the valve sleeve 112 is not translated to the lower position as illustrated in Figure 9. On the member 122 passing through the seat 128, and then passing through the remainder of the valve sleeve 112, the spring 130 raises the valve sleeve 112 to an intermediate position, under the control the cam track 118 and follower pins 120, in which the valve sleeve flow ports 116 are aligned with the body flow ports 132, as shown in Figure 10. As the body flow ports 117 now experience the pressure differential between the body bore and the annulus, the body flow port bungs 134 are pushed out of the ports 117, such than a proportion of the fluid being pumped down through the string passes directly into the annulus through the ports 116, 117, rather than being directed through the bottom hole assembly.

The valve sleeve 112 will remain in the position as illustrated in Figure 10 until a second actuating member 122 is pumped into the string to land in the body 114, allowing cycling of the valve sleeve 112 back to the initial position as illustrated in Figure 8.

Those of skill in the art will recognise that the above described embodiments are mere exemplary of the present invention, and that various modifications and improvements may be made thereto without departing from the scope of the invention. For example, in a variation of the tool 110 described above, a relatively hard ball, for example a steel ball, may be used in place of the bullet-shaped deformable member 124. By balancing the pressure used to pump the ball into place in the sleeve 112, the ball material properties and the degree of interference between the ball and the seat 128 (which may still be relatively small if a harder, less ductile material is chosen), it is possible apply the necessary force to the sleeve 112 for the necessary time to move the sleeve 112 downwards to the position illustrated in Figure 9, before the ball is forced through the seat 128.

Claims

1. Downhole apparatus comprising: a tubular body including a seat; and an actuating member including a wiper dart and an extrudeable portion adapted to mate with the seat, whereby a first pressure applied across the member allows a function to be performed and a higher second pressure causes the portion to be extruded through the seat.

2. The apparatus of claim 1, wherein the extrudeable portion comprises an extrudeable or deformable ball.

3. The apparatus of claim 1 or 2, wherein the wiper dart includes a plurality of sealing members.

4. The apparatus of claim 1, 2 or 3, wherein the sealing members define the same or different diameters.

5. Downhole apparatus comprising: a tubular body including a seat; and an actuating member including an axially extending extrudeable portion with a leading end defining a profile adapted to mate with the seat, whereby a first force applied to the member allows a function to be performed and a higher second force causes the portion to be extruded through the seat.

6. The apparatus of claim 5, wherein the apparatus is adapted to function in response to a first fluid pressure force.

7. The apparatus of claim 6, wherein the apparatus is adapted to function in response to a first fluid pressure force comprising a fluid pressure differential acting across the member.

8. The apparatus of any preceding claim, wherein the extrudeable portion is adapted to be extruded through the seat in response to at least one of a fluid pressure force, a mechanical force, an impulse, and a combination of forces.

9. The apparatus of claim 8, wherein the portion is adapted to be extruded through the seat in response to a fluid propelled member impacting on the actuating member.

10. The apparatus of any preceding claim, in combination with a member adapted to be propelled by fluid and impact on the actuating member.

11. The apparatus of claim 10, wherein the fluid propelled member is a generally cylindrical member.

12. The apparatus of claim 11, wherein the fluid propelled member is of a diameter only slightly smaller than the seat and the body internal diameter.

13. The apparatus of any preceding claim, wherein the extrudeable portion is substantially cylindrical.

14. The apparatus of any preceding claim, wherein the extrudeable portion includes at least one of a conical or tapered surface portion, a corrugated portion, and a stepped portion.

15. The apparatus of any preceding claim, wherein the extrudeale portion is adapted to create a lock between the actuating member and the seat.

16. The apparatus of any preceding claim, wherein the actuation member is configured to create a lock between two relatively moveable parts.

17. The apparatus of claim 16, wherein the actuation member is configured to create a lock between two relatively moveable parts by engaging one part with a first area of the extrudeable portion and another part with a second area of the portion.

18. The apparatus of any preceding claim, wherein a stepped extrudeable portion is provided to provide a step change in the force that is required to extrude the portion from a first mating position to a second mating position.

19. The apparatus of any preceding claim, wherein the extrudeable portion comprise a more ductile material than the seat.

20. The apparatus of claim 19, wherein the extrudeable portion comprise one or more of plastics or metal.

21. The apparatus of claim 20, wherein the extrudeable portion comprises aluminium.

22. The apparatus of any preceding claim, wherein the extrudeable portion is adapted to undergo elastic deformation while being extruded through the seat.

23. The apparatus of any preceding claim, wherein the extrudeable portion is adapted to undergo plastic deformation while being extruded through the seat.

24. The apparatus of any preceding claim, wherein the extrudeable portion is adapted to undergo a combination of elastic and plastic deformation.

25. The apparatus of any preceding claim, wherein the extrudeable portion is adapted to be replaceable.

26. The apparatus of claim 25, wherein the extrudeable portion includes a threaded part to engage a corresponding threaded part on the body of the actuating member.

27. The apparatus of any preceding claim, wherein the actuating member is adapted to close the body bore completely on engaging the seat.

28. The apparatus of claim 27, wherein at least one of the profile and extrudeable portion is adapted to form a seal with the seat.

29. The apparatus of any preceding claim, wherein the body is adapted to be functioned on two or more occasions.

30. The apparatus of claim 29, comprising two or more actuation members.

31. The apparatus of claim 30, wherein a second actuation member is adapted to remain in the body.

32. The apparatus of claim 30, wherein said second actuation member is adapted to resist extrusion through the seat.

33. The apparatus of any preceding claim, wherein the body comprises a valve arrangement including a port in the body wall.

34. The apparatus of claim 33, wherein the port is initially covered or filled.

35. The apparatus of claim 34, wherein the ports is initially covered or filled with a bung.

36. The apparatus of claim 35, wherein the bung comprises a relatively soft or light material, such that the bung will be carried to surface by the drilling fluid and will not damage or jam any other apparatus.

37. The apparatus of claim 35 or 36, wherein the bung is adapted to be readily distinguishable from the drilling fluid or drill cuttings.

38. The apparatus of any preceding claim, wherein the apparatus function is independent of the seat.

39. The apparatus of any preceding claim, wherein the apparatus function is operatively associated with the seat.

40. The apparatus of claim 39, wherein the apparatus is configured such that application of a fluid pressure induced force across the actuating member, and transferred to the seat, induces translation of the seat and the part of the body on which the seat is formed or mounted.

41. The apparatus of any preceding claim, wherein the body includes a sleeve and the seat is operatively associated with the sleeve.

42. The apparatus of claim 41, wherein the seat is formed on the internal diameter of a sleeve.

43. The apparatus of claim 41 or 42, wherein the sleeve is adapted for axial movement such that the sleeve moves downwards in response to a force applied to the seat by the actuating member.

44. The apparatus of any of claims 41 to 43, wherein the sleeve is biased upwards by a spring or the like.

45. The apparatus of any of claims 41 to 44, wherein movement of the sleeve is controlled by means of a cam or the like.

46. The apparatus of any preceding claim, further comprising a catcher for receiving the actuating member after the member has been pushed through the seat.

47. The apparatus of claim 46, wherein the catcher is adapted to accommodate a plurality of actuating members.

48. The apparatus of any preceding claim, wherein the actuating member is adapted to be pumped into the body.

49. The apparatus of claim 48, wherein the actuating member includes a wiper dart.

50. A method of operating a downhole apparatus, the method comprising: providing an actuating member including a wiper dart and an extrudeable portion; pumping the member through a tubular to engage with a seat; applying a first pressure above the member to perform a function; and applying a higher second pressure to extrude the member through the seat.

51. The method of claim 50 comprising measuring the volume of fluid pumped into the tubular behind the dart.

52. The method of claim 50 or 51 comprising pumping the member relatively rapidly into the tubular and then reducing the pump rate a short distance from the seat.

53. The method of any of claims 50 to 52, wherein the function comprises operating a bypass tool and further comprising pumping lost circulation material

(LCM) into the tubular behind the dart.

54. A method of operating a downhole apparatus, the method comprising: providing an actuating member including an axially extending extrudeable portion with a leading end defining a profile; pumping the member through a tubular string; landing the profile on a seat in the string; providing a first force to the member necessary to perform a function; and providing a higher second force to extrude the member through the seat.

55. The method of claim 54, wherein the first force is a fluid pressure force.

56. The method of claim 55, wherein the first force is a fluid pressure differential acting across the member.

57. The method of any of claims 50 to 56, wherein the second force includes at least one of: a fluid pressure force, a mechanical force, an impulse, or a combination of forces.

58. The method of claim 57, wherein the second force is applied, at least in part, by a fluid propelled member impacting on the actuating member.

59. The method of claim 58, comprising pumping the fluid propelled member into the body through a tubular string.

60. The method of any of claims 50 to 59, wherein the second force is applied immediately following the application of the first force.

61. The method of any of claims 50 to 60, wherein the force applied to the member is substantially constant, a time delay between the member landing on the seat and being extruded through the seat being sufficient to perform the function.

62. The method of any of claims 50 to 61, comprising selecting the force necessary to extrude the member through the seat by selecting at least one of: the length of the portion, the difference in dimension or interference between the portion and the seat, the material used to form the portion, and the surface configuration of the portion.

63, The method of any of claims 50 to 62, comprising creating a lock between the actuating member and the seat.

64. The method of any of claims 50 to 63, comprising providing a stepped extrudeable portion to provide a step change in the force that is required to extrude the portion from a first mating position to a second mating position.

65. The method of any of claims 50 to 64, further comprising subjecting the portion to at least one of elastic deformation and plastic deformation on extrusion through the seat.

66. The method of any of claims 50 to 65, further comprising replacing the extrudeable portion.

67. The method of any of claims 50 to 66, comprising close the body bore completely on the actuating member engaging the seat.

68. The method of claim 67, comprising forming a seal between the profile or portion and the seat.

69. The method of any of claims 50 to 68, comprising functioning the body on two or more occasions.

70. The method of claim 69, comprising passing two or more actuation members through the body.

71. The method of claim 69 or 70, wherein the functions include repetitions of the same functions.

72. The method of claim 69, 70 or 71, wherein the functions include different functions.

73. The method of any of claims 69 to 72, wherein the functions are of a cyclic nature.

74. The method of any of claims 50 to 73, comprising retaining an actuation member in the body.

75. The method of any of claims 50 to 74, comprising providing two or more actuation members.

76. The method of any of claims 54 to 75, comprising functioning the body to permit fluid to flow between the body and a surrounding annulus.

77. The method of claim 76, comprising initially covering or closing a flow port in the body wall.

78. The method of claim 77, comprising initially covering or closing the flow port with a bung.

79. The method of claim 78, comprising carrying the bung to surface with drilling fluid.

80. The method of any of claims 50 to 79, comprising applying of a fluid pressure induced force across the actuating member, transferring the force to the seat, and inducing translation of the seat and the part of the body on which the seat is formed or mounted.

81. The method of any of claims 50 to 80, comprising creating a fluid pressure differential across the actuating member to create an elevated fluid pressure in a tubular string above the actuating member to produce a differential pressure between a string bore and a surrounding annulus.

82. The method of any of claims 50 to 81, wherein the function is a pressure test.

83. The method of any of claims 50 to 82, wherein the function is drifting a string.

84. The method of any of claims 50 to 83, comprising axially moving a sleeve downwards in response to a force applied to the seat by the actuating member.

85. The method of claim 84, comprising controlling the movement of the sleeve using a cam or the like.

86. The method of any of claims 50 to 85 comprising providing a catcher for receiving the actuating member after the member has been pushed through the seat.

87. The method of any of claims 50 to 86, comprising circulating fluid through a drill string including the body after the actuating member is extruded through the seat.

88. The method of any of claims 50 to 87, comprising pumping the actuating member into the body.

89. Downhole apparatus comprising a tubular body having a wall defining at least one port, the port being initially filled with a removable bung.

90. The apparatus of claim 89, wherein the bung comprises a polymeric material.

91. The apparatus of claim 89 or 90, wherein the bung is adapted to be inserted in the port.

92. The apparatus of claim 89 or 90, wherein the bung is adapted to be formed or moulded in the port.

93. The apparatus of any of claims 89 to 92, wherein the port is adapted to permit fluid flow through the wall.

94. The apparatus of any of claims 89 to 92, wherein the port is adapted to provide passage for a blade or other member.

95. Downhole apparatus comprising: a tubular body including a seat of a first diameter; and an actuating member of a larger second diameter adapted to mate with the seat and to be extrudeable through the seat, whereby the second diameter is less than 1/8" larger than the first diameter.