GB2457288A

GB2457288A - A drillstring connection valve

Info

Publication number: GB2457288A
Application number: GB0802407A
Authority: GB
Inventors: George Swietlik; Robert Large
Original assignee: Pilot Drilling Control Ltd
Current assignee: Pilot Drilling Control Ltd
Priority date: 2008-02-08
Filing date: 2008-02-08
Publication date: 2009-08-12
Also published as: GB0802407D0

Abstract

A tool (10, Fig.1) provides a fluid tight connection between a fluid supply (2, Fig. 1), a drillstring (4, Fig 1) and an outlet 222. The tool comprises a valve assembly 200 for selectively connecting: (A) the fluid supply to the drillstring; or (B) the drillstring to the outlet. The valve assembly comprises: a shuttle 230 disposed in a housing 15 and a port 220 in a sidewall of the housing the port being in flow communication with the outlet 222. The shuttle defines a flow passage there-through for flow from the fluid supply to the drillstring. A one-way flow valve 210 is provided to selectively close the flow passage, the one-way flow valve permitting flow from the fluid supply to the drillstring; wherein, (A) flow from the fluid supply biases the shuttle in a first position in which the port 220 is closed by the shuttle; and (B) flow from the drillstring biases the shuttle in a second position in which the port is open so that flow from the drillstring flows to the outlet.

Description

1 2457288 A drilistring tool This invention relates to a connector which establishes a fluid tight connection to a drillstring and preferably establishes a fluid tight connection between a drillstring and a top-drive.

Backcjround It is known in the oil and gas industry to use a top drive motor and a drillstring to drill wells. It is the top drive motor that provides the torque to rotate the drillstring, which in turn rotates the drill bit at the bottom of the well. The drillstring itself consists of a series of hollow pipes, typically 3Oft (9.14m) in length, and these are attached to each other via a threaded connection. The top drive is also attached to the drillstring via a threaded connection.

During the drilling process, drilling-mud is pumped through the connection between the top drive and the drillstring. This drilling-mud travels through the drillstring and ensures sufficient lubrication, cooling and the removal of cuttings. It is often necessary to remove the drilistring from the well (to replace the drill bit for example) and under such circumstances drilling-mud is pumped through the drilistring to displace and support the retreating drillstring and maintain hydraulic balance in the well bore. This ensures that a vacuum is not created and that the force required to remove the drillstring is minimised, allowing the removal to occur more quickly. In a conventional arrangement, the drilling-mud is pumped through the same connection, between the top drive and drillstring, as used when drilling.

When removing a drillstring from a well (which in the industry is known as tripping-out), successive sections of the drillstring have to be disconnected from the remaining sections of the drillstring. Furthermore, the section being removed also has to be disconnected from the top drive. A new connection is then established between the top drive and the remaining sections of the drillstring. However, making and breaking these threaded connections is very time consuming and slows down the process of removing a drillstring from a well. This has a serious impact on the productivity of the well.

Previous attempts have been made at speeding up the process of tripping-out.

GB2156402A discloses methods for controlling the rate of withdrawal and the drilling-mud pressure to maximise the tripping-out speed. However, the time taken to connect and disconnect each section of the drillstring to the top drive is not addressed. Other attempts include removing several sections at a time, as discussed in GB2156402A.

However, this approach is limited by the height of the derrick holding the top drive.

GB2435059A discloses a device which comprises an extending piston-rod with a bung, which is selectively engaged with the top of the drillstring to provide a fluid tight seal between the drilistring and top drive. This arrangement obviates the need for threading and unthreading the drilistring to the top drive. However, a problem with the device disclosed therein is that the extension of the piston-rod is dependent upon the pressure and flow of the drilling mud through the top drive. Whilst this is advantageous in certain applications, a greater degree of control over the piston-rod extension independent of the drilling mud pressure is desirable.

In other applications, it is often desirable to displace fluid from the borehole, particularly when lowering the drilistring, for example, in deep water drilling applications. In such deepwater applications the seabed accommodates equipment to support the construction of the well and the tubing used to line the well bore is hung and placed from this position. This is carried out by using a drillstring as a means of conveying and landing the tubing into position and as the drilistring is lowered, successive sections of drilistring have to be added. It would therefore be desirable to use a device similar to that disclosed in GB2435059A to minimise the number of threaded connections required. However, as the bore of the drillstring is much smaller than the bore of the tubing, then fluid will be displaced and exit up through the driHstring. The device disclosed in GB2435059A is not suitable for such an application because it is not designed for fluid to flow up the drillstring, as there is a risk that the piston-rod would not stay in position. The present invention seeks to address these issues.

Statements of Invention

According to a first aspect of the present invention, there is provided a tool which provides a fluid tight connection between a fluid supply, a drilistring and an outlet, the tool comprising a valve assembly for selectively connecting: (A) the drilistring to the outlet; or (B) the fluid supply to the drillstring.

According to a second aspect of the present invention, there is provided a connector which provides a fluid tight connection between a fluid supply, a drilistring and an outlet, the connector comprising a valve assembly for selectively connecting: (A) the fluid supply to the drilistring; or (B) the drillstring to the outlet; the valve assembly comprising: a shuttle disposed in a housing, the shuttle defining a first flow passage therethrough for flow from the fluid supply to the drilistring; a one-way flow valve provided to selectively close the flow passage through the shuttle, the one-way flow valve permitting flow from the fluid supply to the drillstring; and a port in flow communication with the outlet; wherein, (A) flow from the fluid supply biases the shuttle in a first position in which the port is closed by the shuttle; and (B) flow from the drillstring biases the shuttle in a second position in which the port is open so that flow from the drilistring flows to the outlet.

The port may be formed in a side wall of the housing and the shuttle may be slidably disposed in the housing. The port in the side wall of the housing may be angled, such that a pipe exiting the port and leading to the outlet may not be perpendicular to the housing. Alternatively, the pipe may be perpendicular to the housing so that it is substantially horizontal.

The housing may be in flow communication with the fluid supply and the drilistring, and/or a fluid tight seal may be provided between the shuttle and the housing. Fluid flowing from the drilistring may act against the one-way flow valve moving the shuttle from the first position to the second position such that the port in the side-wall of the housing may be exposed and fluid may flow from the drilistring to the outlet.

The one-way flow valve may be disposed at a first end of the shuttle adjacent to the drillstring. The one-way flow valve may be disposed at a second end of the shuttle adjacent to the fluid supply. The one-way flow valve may be disposed at a location between a first end of the shuttle adjacent to the drillstring and a second end of the shuttle adjacent to the fluid supply. The one-way flow valve may comprise a flap and seat arrangement.

The valve assembly may further comprise a first piston slidably disposed about the shuttle at a second end of the shuttle adjacent to the fluid supply. A fluid tight seal may be provided between the first pislon and the shuttle and the first piston and the housing.

The first piston may have: (A) a first position in which an opening in the sidewall of the shuttle is blocked by the first piston; and (B) a second position in which the opening is open so that the fluid passageway of the shuttle is in flow communication with the fluid supply.

A cap may be provided on the second end of the shuttle, the first piston abutting the cap when the first piston is in its first position. The projected area of the cap exposed to the flow from the fluid supply may be greater than the projected area of the first piston exposed to the flow from the fluid supply.

The first piston may be biased towards the first position by a resilient means. The resilient means may be resisted by an abutment emanating from the shuttle. The abutment may be in the form of an annular shoulder.

The connector may comprise a piston-rod and a cylinder, where the piston-rod may have a seal at or towards its free end which is adapted to sealingly engage the drillstring when the piston-rod is at least partially extended from the cylinder. The seal between the connector and the drilistring may be provided by the location of a tapered bung in the open end of the drillstring.

The piston-rod may be slidably mounted on a shaft so that the piston-rod telescopically extends from the shaft, the shaft defining a fluid path from the fluid supply to the drilistring.

The piston-rod may comprise a second piston at an end of the piston-rod enclosed by the cylinder. The second piston may be slidably mounted within the cylinder and may divide the cylinder into first and second chambers.

A control means may be provided. The control means may control the pressure of the fluid in the first chamber and/or the pressure of the fluid in the second chamber. The control means may control the extent of the piston-rod extension.

The fluid in the first chamber and/or second chamber may be a different fluid from that supplied by the fluid supply means. The fluid in the first chamber and/or second chamber may be the same fluid as supplied by the fluid supply means.

An advantage of the valving system described above is that the flow of drilling fluid is automatically controlled ri either direction without any alteration in position of the piston-rod. This is achieved by separating out operation of the drilling fluid valve (i.e. the shuttle valve) and the placement of the piston-rod in the drilistring (i.e. by virtue of the second piston). A further advantage of the present invention is that the port in the sidewall of the housing is less susceptible to blocking by debris carried in the flow from the well bore. With such an arrangement, a larger port opening is possible and horizontal or angled valving does not have the same tendency to block.

According to a third aspect of the present invention, there is provided a connector which provides a fluid tight connection between a fluid supply and a drilistring, the connector comprising: a piston-rod and a cylinder, the piston-rod having a seal at or towards its free end which is adapted to sealingly engage the drillstring when the piston-rod is at least partially extended from the cylinder; and a threaded portion provided on the cylinder; the threaded portion being adapted to engage with a threaded section in an open end of the drilistring; wherein the piston-rod extends through the threaded portion.

The seal between the connector and the drilistring may be provided by the location of a tapered bung in the open end of the drilistring. The seal may be detachable from the piston-rod. The seal may be interchangeable with one or more alternative seals. The connector may connect to the drilistring via the threaded portion engaging with a corresponding threaded section in the open end of the drillstririg.

The seal may be provided on a shaft, the shaft being detachable from the piston-rod.

The shaft may be threadably engaged with the piston-rod. The shaft may be threadably engaged to the piston-rod with a stub-acme connection.

A connection between the piston-rod and shaft may act as a sacrificial connection such that if an impact load is applied to the shaft, the piston-rod and cylinder may be protected. The connection between the piston-rod and shaft may be box weak.

The piston-rod may be retractable within the threaded portion, so that when the seal is detached the piston-rod may not be exposed beyond the end of the threaded portion.

The piston-rod may fit inside the interior of the drilistring beyond the threaded section in the open end of the drilistring. The piston-rod may be provided with a mechanical stop limiting the retraction of the piston-rod into the cylinder.

The piston-rod may provide a flow communication path between the fluid supply and the drillstring. The piston-rod may be hollow and the shaft may be hollow.

The threaded portion may be provided on a threaded member disposed about the piston-rod and the threaded member may be detachable from the cylinder. The threaded member may be threadably engaged with the cylinder. The threaded member may be interchangeable with one or more alternative threaded members.

The piston-rod may be provided with a keyway. The threaded member may be provided with a key and the key may interface with the keyway of the piston-rod so that rotation of the piston-rod may be prevented. The key and keyway may provide the mechanical stop limiting the retraction of the piston-rod.

The threaded member may be provided with a port and the port may act as a vent for fluid displaced in the cylinder by movement of the piston-rod.

The connector may be capable of transmitting torque from a top-drive to the drillstring via the threaded portion engaging with the threaded section of the drillstring. All threaded connections may be orientated in the same direction. The threaded portion may comprise a standard pin connection. The threaded section in the open end of the drillstring may comprise a standard box connection.

According to a fourth aspect of the present invention, there is provided a connector which provides a fluid tight connection between a fluid supply and a drillstring, the connector comprising: a hydraulic ram comprising a piston-rod and a cylinder, the piston-rod having a seal at or towards its free end which is adapted to sealingly engage the drillstring when the piston-rod is at least partially extended from the cylinder; and a threaded portion provided on the cylinder; the threaded portion being adapted to engage with a threaded section in an open end of the drilistring; wherein the seal is detachable from the piston-rod.

According to a fifth aspect of the present invention, there is provided a connector which provides a fluid tight connection between a fluid supply and a drilistring, the connector comprising: a hydraulic ram comprising a piston-rod and a cylinder, the piston-rod having a seal at or towards its free end which is adapted to sealingly engage the drillstring when the piston-rod is at least partially extended from the cylinder; and a threaded portion provided on the cylinder; the threaded portion being adapted to engage with a threaded section in an open end of the drilistring; wherein the threaded portion is provided on a threaded member disposed about the piston-rod, the threaded member being detachable from the cylinder.

According to a sixth aspect of the present invention, there is provided a connector which provides a fluid tight connection between a fluid supply and a drillstring, the connector comprising: a piston-rod and a cylinder, the piston-rod having a seal at or towards its free end which is adapted to sealingly engage the drilistring when the piston-rod is at least partially extended from the cylinder; and a threaded portion provided on the cylinder; the threaded portion being adapted to engage with a threaded section in an open end of the drillstring; wherein the piston-rod and the cylinder form an hydraulic ram.

According to a seventh aspect of the present invention, there is provided a connector which provides a fluid tight connection between a fluid supply and a drilistring, the connector comprising: a piston-rod and a cylinder, the piston-rod having a seal at or towards its free end which is adapted to sealingly engage the drillstring when the piston-rod is at least partially extended from the cylinder; wherein the seal is detachable from the piston-rod.

Preferably, the seal is fixed to a detachable shaft, which is mounted to the piston-rod.

Preferably, the detachable shaft is connected to the piston-rod by means of a threaded conneetion.

According to an eighth aspect of the present invention, there is provided a connector which provides a fluid tight connection between a fluid supply and a drillstring, the connector comprising: a piston-rod and a cylinder, the piston-rod having a seal at or towards its free end which is adapted to sealingly engage the drillstring when the piston-rod is at least partially extended from the cylinder; and a threaded portion provided on the cylinder; the threaded portion being adapted to engage with a threaded section in an open end of the drillstring with the seal in engagement with the drilistring.

Brief Description of the Drawings

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the following drawings, in which: Figure 1 is a schematic of the connector and shows the connector in position between the top drive and the drillstring; Figures 2a and 2b are sectional side projections of the connector according to a first embodiment of the invention and show the connector in a retracted position (Figure 2a) and in an extended position (Figure 2b); Figures 3a and 3b are sectional side projections of the connector according to a first embodiment of the invention and show the detail of the arrangement for extending and retracting the connector; Figures 4a, 4b and 4c are a more detailed sectional view of the connector according to a first embodiment of the invention and show the arrangement for selectively transferring the drilling fluid from the drillstring or the outlet; Figures 5a and 5b are more detailed sectional views of the connector according to a first embodiment of the invention and show the connector in a retracted position (Figure 5a) and a concealed position (Figure 5b); Figure 6 is a sectional side projection of the connector according to a second embodiment of the invention; and Figure 7 is a sectional side projection of the connector according to a third embodiment of the invention.

Detailed Description of the Preferred Embodiment

With reference to Figure 1, a drillstring 4 is lowered into a well by lowering a top drive 2. In a conventional arrangement, the top-most section 3 of the drillstring 4 is provided with a female thread, which directly engages a male threaded connector 5 on the top drive 2 to provide a connection to allow drilling-mud to be pumped into or from the drillstring 4. Once a section of the drillstring 4 is lowered into the well it must then be disconnected from the top drive 2 before the next section can be added to the drillstring. Making and breaking the threaded connection between the top drive and drillstring is time consuming, particularly when lowering an entire drillstring 4 section by section to below the seabed when deep sea drilling. The present invention therefore relates to an alternative means for establishing this connection, whilst also allowing drilling fluid to flow through the connector in either direction. This alternative connection is achieved via a connector 10, which is placed between the top drive 2 and drillstring 4.

With reference to Figures 2a and 2b, the connector 10, according to a first embodiment of the present invention, comprises a cylinder 15 and a piston-rod 20, the piston-rod 20 being slidably engaged in the cylinder 15. The piston-rod 20 further comprises a hollow tubular 30, the tubular 30 being slidably engaged in the cylinder 15 such that a first end of the tubular 30 protrudes outside the cylinder 15 and a second end is within the cylinder 15. The tubular 30 is also disposed about a hollow shaft 16, the shaft 16 being disposed within the cylinder 15. The tubular 30, cylinder 15 and shaft 16 are arranged such that their longitudinal axes are coincident and the tubular 30 is slidably disposed about the shaft 16 such that the piston-rod 20 telescopically extends through the cylinder 15 from a retracted position to an extended position. Figure 2a shows the piston-rod 20 in its retracted position, whilst figure 2b shows the piston-rod 20 in its extended position.

A bung 60 and seals 130 are located on the first end of the tubular 30. The bung 60 may be made from a resilient and/or elastomeric material such as rubber or nylon and is shaped to fit into the top end of a drillstring 4. The bung 60 and seals 130 engage the top end of a drillstring 4 when the piston-rod 20 is in its extended position, thereby providing a fluid tight seal between the connector 10 and drillstring 4. For example, the bung 60 and/or seals may seal on, in or around a box at the top end of the drillstring 4.

At a first end of the cylinder 15 there is provided a first end plug 42, through which the tubular 30 protrudes. The first end plug 42 is threaded to the first end of the cylinder 15. A threaded member 110 is then provided on the first end plug 42. The threaded member 110 is connected to the first end plug 42 by virtue of a threaded connection and the threaded member 110 is hollow to allow the tubular 30 to pass through it. The threaded member 110 seals the inside of the cylinder 15 from the outside, whilst also allowing the tubular 30 to slide in or out of the cylinder 15. Seals, such as 0-ring seals 26 are used to seal between the first end plug 42 and tubular 30.

At the opposite end of the cylinder 15 to the first end plug 42, there is provided a socket for engagement with the top drive 2. The socket 25 comprises a female threaded connection which may be in the form of a conventional box and which threads onto a corresponding thread (or pin) on the top drive 2. The top drive 2 provides drilling fluid to the cylinder 15 through the socket 25.

With reference to Figures 3a and 3b, the piston-rod 20 further comprises a second piston 50 disposed at a second end of the tubular 30. The second piston 50 is slidably mounted on the tubular 30 inside the cylinder 15 and is free to move between a second end plug 40 and the first end plug 42. The second end plug 40 is threaded into the cylinder 15 and threaded onto the shaft 16 such that the hollow centre of the shaft 16 continues through the second end plug 40. The inside of the cylinder 15 is divided by the second piston 50 to form a first chamber 80 and a second chamber 70. The first end plug 42, cylinder 15, tubular 30 and second piston 50 define the first chamber and an end-face 41, cylinder 15, shaft 16 and second piston 50 define the second chamber 70. The piston 50 is fixedly attached to the tubular 30 and is sealed against the inside of cylinder 15 and the outside of shaft 16, for example by means of 0-ring seals 52 and 54, to ensure no flow communication between the two chambers 70 and 80.

Retraction of the piston-rod 20 is limited by the bung 60 impinging against the threaded member 110 and the extension of the piston-rod 20 is limited by an annular shoulder 114 in the tubular 30 engaging with an annular abutment surface 116 in the threaded member 110. The annular shoulder 114, annular abutment surface 116, bung 60 and threaded member 110 thereby act as mechanical stops. An atmospheric vent 112 is provided in the threaded member 110 between the annular shoulder 114 and the annular abutment surface 116 to ensure that movement of the tubular 30 is not resisted by air trapped therebetween. Retraction of the piston-rod 20 is also limited by a second annular shoulder 115, which is disposed inside the piston-rod 20, such that the second annular shoulder abuts an end of the shaft 16. To avoid a pressure lock from occurring, the volume of fluid displaced by the movement of the second annular shoulder 115 is preferably equal to the volume of fluid displaced by the piston-rod 20 as it extends into the drillstring.

In the first embodiment of the invention, the first and second chambers 80 and 70 are provided with pressurised air via an air supply (not shown). The first chamber 80 is in flow communication with the air supply via a first supply port 100 and the second chamber 70 is in flow communication with the air supply via a second supply port 90.

In the first embodiment of the invention, a valve 118 is provided between the first and second supply ports 100, 90, the valve 118 is also connected to the air supply and the atmosphere. The valve 118 in an exemplary embodiment comprises a four-way cross port valve for selectively connecting the first and second supply ports 100, 90 to the air supply and the second and first supply ports 90, 100 respectively to the atmosphere.

In alternative embodiments the first and second chambers 80, 70 may be pressurised with a fluid other than air and the valve 118 may comprise an alternative valve system for selectively pressurising the first and second chambers 80, 70.

In operation the air supply selectively provides pressurised air to either the first chamber 80 or the second chamber 70, via valve 118, and the other of the first or second chambers 80, 70 is vented to the atmosphere, again via valve 118. A pressure differential is therefore created across the second piston 50 and the piston-rod 20 extends when the force acting on the second piston 50 due to air pressure in the first chamber 80 is higher than the force acting on the second piston 50 due to the air pressure in the second chamber 70 (figure 3b). Conversely, the piston-rod 20 retracts when the force acting on the second piston 50 due to air pressure in the second chamber 70 is higher than the force acting on the second piston 50 due to the air pressure in the first chamber 70 (figure 3a).

With reference to Figures 4a, 4b and 4c, the cylinder 15 further comprises a valve assembly 200, the valve assembly 200 being disposed within the cylinder 15 between the socket 25 and the end face 41 of the second end plug 40, and on the other side of the end face 41 to the shaft 16 and tubular 30. The valve assembly 200 comprises a shuttle valve 230, which is slidably disposed in the cylinder 15. A port 220 is provided in a sidewall of the cylinder 15, the port 220 providing an outlet to a reservoir for drilling fluid via a pipe 222. The port 220 is located in a section of the cylinder 15 traversed by the shuttle valve 230 so that when the shuttle valve 230 is in a first position the port 220 is closed by the shuttle 230 (figures 4a and 4b); and when the shuttle 230 is in a second position the port 220 is open to the centre of the cylinder 15 (figure 4c). In the second (open) position, the port 220 is therefore in flow communication with the centre of the cylinder 15, between the shuttle 230 and second end plug 40, and the centre of the hollow shaft 16, which adjoins the second end plug 40. Furthermore, the shuttle valve 230 has a hollow section, which provides a flow passage therethrough for flow from the socket 25 to the centre of the hollow shaft 16 and subsequently through the tubular 30 and into the drillstring 4.

The shuttle valve 230 comprises a one-way flow valve 210 disposed at a first end of the shuttle valve adjacent to the second end plug 40. The one-way flow valve 210 permits flow from the socket 25 to the shaft 16, but not vice versa. The one-way flow valve 210 in the first embodiment of the invention is a flapper valve, which engages a seat, but in alternative embodiments the one-way flow valve 210 may comprise a ball or plug socket arrangement.

The valve assembly 200 further comprises a first piston 240 slidably disposed about a second end of the shuttle valve 230 adjacent to the socket 25. A fluid tight seal is provided between the first piston 240 and the shuttle 230 and the first piston 240 and the cylinder 15 by virtue of seals 242 and 244 respectively. The shuttle valve 230 further comprises an opening 260 in the sidewall of the shuttle valve 230. The opening 260 in the sidewall of the shuttle valve 230 is blocked by the first piston 240 when the first piston 240 is in a first position relative to the shuttle 230 (Figures 4a and 4c). By contrast, the opening 260 is open when the first piston 240 is in a second position relative to the shuttle 230 (Figure 4b) so that the hollow section of the shuttle is in flow communication with the socket 25.

The shuttle valve 230 further comprises a cap 250, which is provided on the second end of the shuttle valve 230. The first piston 240 abuts the cap 250 when the first piston 240 is in its first position and serves to prevent movement of the first piston 240 beyond the second end of the shuttle valve 230. The cap 250 is also substantially conically shaped so that it can direct the flow of drilling fluid around the cap 250 and into the opening 260 when the first piston 240 is in its second position. The cap 250 also limits the movement of the shuttle valve 230: when the shuttle valve 230 is in its second position, the cap 250 abuts a recess in the socket 25 (Figure 4c). Furthermore, the projected area of the cap 250 exposed to the flow from the socket 25 is greater than the projected area of the first piston 240 exposed to the flow from the socket 25.

The motion of the first piston 240 relative to the shuttle valve 230 is biased towards the first position of the first piston 240 by a spring 280. A first end of the spring 280 abuts the first piston 24, whilst a second end of the spring 280 abuts an abutment 282 emanating from the shuttle valve 230. The abutment 282 also provides a means for limiting the motion of the shuttle valve 230, as the abutment 282 abuts a notch 284 in the cylinder 15 when the shuttle valve 230 is in its first position. The spring 280 occupies a cavity 288 formed by the notch 284, the cylinder 15, first piston 240 and shuttle valve 230. A vent 286 to the cavity 288 is provided in the sidewall of cylinder 15 as the volume of the cavity 288 changes as the shuttle valve 230 moves between its two positions. In an alternative embodiment, the spring 280 could instead comprise a pneumatic or hydraulic piston arrangement, which could for example be achieved by closing vent 286.

With reference to Figure 5a, the bung 60, the connector 10, further comprises a detachable shaft 105. The detachable shaft 105 is threadably attached to the tubular 30 and is selectively detachable from the tubular 30. The seals 130 are provided around the outside of the detachable shaft 105. The detachable shaft 105 is hollow to allow the flow of drilling fluid from the top drive 2, through the shaft 16 and tubular 15, and into the top of the drillstring 4.

The detachable shaft 105 and attached seals 130 are interchangeable with alternative shaft and seal arrangements. This facilitates the repair and replacement of worn seals, or differently shaped bungs could be deployed for different drillstrings. Furthermore, the connection between the tubular 30 and the detachable shaft 105 can be made deliberately weak, so that it acts as a sacrificial connection. If an impact load is applied to the bung 60 the connection will tend to fail, so that the piston-rod 20 and cylinder 15 are protected from damage. For example, the detachable shaft 105 may be provided with a female threaded socket, which engages with a corresponding male thread on the tubular 30, and the female threaded socket of the detachable shaft 105 may be deliberately weakened at its root so that it will fail before damage occurs to the tubular 30.

The end of the detachable shaft 105, which attaches to the tubular 30, has the same or smaller external dimensions as the tubular 30. This ensures that the detachable shaft fits inside the threaded member 110. Furthermore, the detachable shaft 105 has a protrusion 106, which acts as a mechanical stop limiting the retraction of the piston-rod 20 into the cylinder 15. The protrusion 106 is shaped with spanner flats so that the detachable shaft 105 can be removed from the tubular 30.

With reference to Figure 5b, the tubular 30 further comprises an abutment shoulder 150, which is formed by a flat portion on the outer surface of the tubular 30 being adjacent to a cylindrical portion. The flat portion on the surface of the tubular 30 provides a keyway and the threaded member 110 is provided with a corresponding key 160. The key 160 interfaces with the keyway of the tubular 30 so that rotation of the tubular 30 is prevented, thereby facilitating removal of the detachable shaft 105 Furthermore, the tubular 30 may be fully retractable within the threaded member 110 when the detachable shaft 105 is removed, such that the tubular 30 does not extend beyond the end of the threaded member 110. The key 160 and keyway also provide a mechanical stop limiting the retraction of the piston-rod 20 when the detachable shaft is removed.

The threaded member 110 is further provided with a threaded section 170. In one mode of operation the threaded section 170 is threadably connected to the open end of the drillstring 4 and the connector 10 is therefore capable of transmitting torque from the top-drive 2 to the drillstring 4. Accordingly, in order to transmit drive, the threaded connections between the top-drive 2, socket 25, threaded member 110 and drillstring 4 are orientated in the same direction.

The detachable shaft 105 and hence bung 60 are removed from the tubular 30 when the threaded member 110 is connected to the drillstring 4. The tubular 30 is sized so that it fits inside the interior of the drilistring beyond the threaded section in the open end of the drillstring. Alternatively, the tubular 30 may also be retracted into the threaded member 110.

In an alternative embodiment, the detachable shaft 105 need not be removed from the tubular 30 when threading the threaded member 110 to the drillstring. The connector 10 may then connect to the drillstring by virtue of both the bung 60 and the threaded member 110. Such an alternative embodiment would allow rapid deployment of the threaded connection without having to remove the detachable shaft 105, thereby saving time and money. In order to enable the engagement of the threaded member with the drillstring 4 without removing the detachable shaft 105, the protrusion may be smaller than the protrusion 106 shown in figure 3a. For example, the protrusion may not extend radially outwardly beyond the radially outer surface of the bung 60.

The threaded member 110 is removable from the first end cap 42 and as such is interchangeable with alternative threaded members. This facilitates repair of the threaded member 110 and/or enables differently shaped threaded members to be deployed to suit the particular drillstring 4 in use.

In operation, the connector 10 is connected to the top drive 2 and the top drive 2 is lowered to a suitable position, so that the connector can reach the open end of the driltstring 4. Once the top drive 2 and connector 10 are in place, the piston-rod 20 is extended by increasing the pressure in the second chamber 70. The bung 60 is then located in the box at the end of the drillstring 4 and a fluid tight seal is provided by the seals 130. The elevators 6 can then engage the drillstring 4 and the slips (not shown) can be released. The drillstring 4 can then be lifted from the well. Whilst the drillstring 4 is being lifted, drilling fluid may be pumped from the top drive 2, through the connector 10 and into the drillstring 4, to replace the volume of the drillstring displaced as it is retracted from the well.

The top drive 2 pumps drilling fluid through the socket 25, which connects the top drive 2 to the connector 10. The pressure of the drilling fluid then acts on the cap 250 and first piston 240 and the shuttle is moved from its second position towards its first position. The first piston 240 remains in its first position relative to the shuttle, as the projected area the cap 250 is greater than the projected area of the first piston 240.

The shuttle movement ceases once the abutment 282 on the shuttle valve 230 engages the notch 284. The shuttle valve 230 is then in its first position (see Figure 4a). The pressure of the drilling fluid then forces the first piston to move relative to the shuttle. As the first piston moves into its second position, the opening 260 in the shuttle valve 230 is revealed and drilling fluid can flow through the opening 260 into the passageway through the shuttle valve 230 and through the one-way flow valve 210 and into the passage defined by the hollow shaft 16 (see Figure 4b). The drilling fluid then flows into the extended tubular 30 and into the drillstring 4, thereby replacing the volume displaced by the drillstring 4 as it is retracted from the well.

Throughout this process the drilling fluid is kept separate from the air in the first and second chambers 80, 70, by virtue of the end-plug 40, shaft 16 and tubular 30. The drilling fluid flows through the centre of shaft 16 and tubular 30, whilst the air is outside these components and this separation is maintained by the deals 54 between the inside of the tubular 30 and the outside of shaft 16.

If there is a build up of pressure of drilling fluid due to an excess of drilling fluid in the well, a blockage or lowering of the drillstring 4, then drilling fluid will flow back through the piston-rod 20, shaft 16 and second end plug 40 towards the shuttle valve 230.

However, once this flow reaches the shuttle valve 230, the drilling fluid closes the one-way flow valve 210 and the flow may not pass through the shuttle valve 230. Under such conditions, the one-way flow valve 210 and shuttle valve 230 will effectively form a piston arrangement, and the shuttle valve 230 will be forced into its second position.

The port 220 will therefore be revealed and the flow from the drillstring 4 may continue through the port outlet and piping 222 to a reservoir (see Figure 4c). Once the pressure in the drillstring 4 has reduced, the shuttle valve 230 will return to its first position, closing the port 220, and normal operation, as described above, may resume.

When a sufficient section of the drillstring 4 is clear of the well (one or more sections may be removed at a time), the slips will reengage with the drillstring 4 and the flow of drilling fluid from the top drive 2 will be stopped. The first piston 240 will then move to its first position under the action of the biasing spring 280, thereby shutting off the opening 260 and the flow path to the drillstring 4. The piston-rod 20 can then be retracted from the drillstring 4 by increasing the pressure in the first chamber 80 without leaking any drilling fluid from the top drive 2. The exposed section of the drillstring 4 can then be removed from the rest of the drilistring remaining in the well and the process described above can be repeated.

As previously mentioned, the connector 10 replaces the traditional threaded connection between a top drive 2 and drillstring 4 during the removal of a drillstring 4 from a well.

With this connector, the connection between the top drive 2 and drillstring 4 can therefore be established in a much shorter time and great savings can be achieved.

With reference to Figure 6, the second chamber 70, according to a second embodiment of the present invention, is provided with drilling fluid via a bypass pipe 500. The bypass pipe 500 is in the form of a large through-bore hydraulic link, which joins a section of the cylinder 15 between the shuttle valve 230 and socket 25 to the second chamber 70. A second one-way flow valve 510 is provided in the bypass pipe 500, the second one-way flow valve 510 permitting flow into the second chamber 70, but not in the opposite direction. In addition to the second one-way flow valve 510 there is a release valve 520, which is disposed in a parallel fashion beside the second one-way flow valve 510. The release valve 520 is also in flow communication with the second chamber 70 and the bypass pipe 500, however the release valve 520 permits flow from the second chamber 70 to the bypass pipe 500 when a sufficient pressure is applied to a side valve 530 on the release valve 520. The side valve 530 is not in flow communication with the second chamber 70 or bypass pipe 500, but merely serves to release the release valve 520 so that drilling fluid may flow from the second chamber to the top drive 2. The side valve 530 is in flow communication with the air supply and the first supply port 100. When the pressure of the air supply (which may be located on the top drive) is increased, the air in the first chamber 80 acts on the second piston 50 causing the piston-rod 20 to retract. The pressunsed air supply also releases the release valve 520 and the drilling fluid in the second chamber 70 can drain through the release valve 520 and bypass pipe 500 back to the top drive 2. When the pressure of the air supply is reduced, the release valve 520 reseats and drilling fluid flows into the second chamber 70 via the second one-way valve 510. The piston-rod 20 then extends due to the pressure of the drilling fluid acting on the second piston 50.

With reference to Figure 7, the first chamber 80, according to a third embodiment of the present invention, is provided with a second spring 600. The second spring 600 acts against the second piston 50, so that the second piston 50 and piston-rod 20 are biased towards the end-face 41. Pressurised air is then selectively supplied to the second chamber 70 to extend the piston-rod 20. To retract the piston-rod 20, the second chamber 70 is vented to atmospheric pressure.

In an alternative embodiment of the invention, the second spring 600 may be provided in the second chamber 70 and the second piston 50 and piston-rod 20 are biased towards the first end plug 42. The first chamber 80 is then selectively provided with pressurised air to retract the piston-rod 20.

According to a fourth embodiment of the invention (not shown), the valving assembly is provided as a tool separate from the connector 10. In such an embodiment, the valving assembly 200 is provided in a section of the drillstring 4 and the portion of the cylinder 15 enclosing the valving assembly 200 interfaces directly with adjacent sections of the drillstring. The port 220 of the valving assembly 200 in this embodiment provides a direct outlet for drilling fluid to the space between the drillstring 4 and the wellbore casing. The arrangement of the valving assembly 200 is otherwise unchanged.

The connection between the top drive 2 and drillstring 4 is still established by the piston-rod 20, although a device separate from the valving assembly 200 provides this connection. As will be appreciated, alternative connection means known to the skilled person may be used.

The valving assembly 200 according to the fourth embodiment of the invention can be located at any point in the drillstring, for example at the top of the drilistring or further down. With the valving assembly 200 provided at the topmost end of the drillstring, the valving assembly is provided with a box connection so that it directly receives the piston-rod 20 of the connection means. In such an arrangement, the pipe 222 leading from the port 220 may either deliver the backflow of drilling fluid to the space between the drillstring and wellbore casing or to a separate reservoir.

In an alternative embodiment the valving assembly 200 is integral to the top drive 4 and is provided as a separate tool to the connection means.

Claims

Claims 1. A tool comprising a valve assembly for selectively connecting: (A) a fluid supply to a drillstring; or (B) the drilistring to an outlet; the valve assembly comprising a shuttle disposed in a housing, the shuttle defining a flow passage therethrough for flow from the fluid supply to the drillstring; a one-way flow valve provided to selectively close the flow passage through the shuttle, the one-way flow valve permitting flow from the fluid supply to the drillstring; and, a port in flow communication with the outlet; wherein, (A) flow from the fluid supply biases the shuttle in a first position in which the port is closed by the shuttle; and (B) flow from the drillstring biases the shuttle in a second position in which the port is open so that flow from the drillstring flows to the outlet.
2. A tool as claimed in claim 1, wherein the port is formed in a side-wall of the housing.
3. A tool as claimed in claim 1 or 2, wherein the shuttle is slidably disposed in the housing, the housing being in flow communication with the fluid supply and the drilistring, with a fluid tight seal being provided between the shuttle and the housing.
4. A tool as claimed in claim 2 or 3, when dependent on claim 2. wherein fluid flowing from the drillstring acts against the one-way flow valve moving the shuttle from the first position to the second position such that the port in the side-wall of the housing is exposed and fluid flows from the drillstring to the outlet.
5. A tool as claimed in any preceding claim, wherein the one-way flow valve is disposed at a first end of the shuttle adjacent to the drillstring.
6. A tool as claimed in any preceding claim, wherein the one-way flow valve is disposed at a second end of the shuttle adjacent to the fluid supply.
7. A tool as claimed in any preceding claim, wherein the one-way flow valve is disposed at a location between a first end of the shuttle adjacent to the drilistring and a second end of the shuttle adjacent to the fluid supply.
8. A tool as claimed in any preceding claim, wherein the one-way flow valve comprises a flap and seat arrangement.
9. A tool as claimed in any preceding claim, wherein the valve assembly further comprises a first piston slidably disposed about the shuttle at a second end of the shuttle adjacent to the fluid supply, a fluid tight seal being provided between the first piston and the shuttle and the first piston and the housing.
10. A tool as claimed in claim 9, wherein the first piston has: (A) a first position in which an opening in the sidewall of the shuttle is blocked by the first piston; and (B) a second position in which the opening is open so that the fluid passageway of the shuttle is in flow communication with the fluid supply.
11. A tool as claimed in claim io, wherein a cap is provided on the second end of the shuttle, the first piston abutting the cap when the first piston is in its first position.
12. A tool as claimed in claim 11, wherein the projected area of the cap exposed to the flow from the fluid supply is greater than the projected area of the first piston exposed to the flow from the fluid supply.
13. A tool as claimed in claim 10, 11 or 12, wherein the first piston is biased towards the first position by a resilient means.
14. A tool as claimed in claim 13, wherein the resilient means is resisted by an abutment emanating from the shuttle.
15. A tool as claimed in any preceding claim, wherein the tool comprises a piston-rod and a cylinder, the piston-rod having a seal at or towards its free end which is adapted to sealingly engage the drilistring when the piston-rod is at least partially extended from the cylinder.
16. A tool as claimed in claim 15, whereIn the seal between the tool and the drilistring is provided by the location of a tapered bung in the open end of the drillstring.
17. A tool as claimed in claim 15 or 16, wherein the piston-rod is slidably mounted on a shaft so that the piston-rod telescopically extends from the shaft, the shaft defining a fluid path from the fluid supply to the drillstring.
18. A tool as claimed in claim 15, 16 or 17, wherein the piston-rod comprises a second piston at an end of the piston-rod enclosed by the cylinder, the second piston being slidably mounted within the cylinder and dividing the cylinder into first and second chambers.
19. A tool as claimed in claim 18, wherein a control means is provided to control the pressure of the fluid in the first chamber and/or the pressure of the fluid in the second chamber.
20. A tool as claimed in claim 19, wherein the control means controls the extent of the piston-rod extension.
21. A tool as claimed in claim 19 or 20, wherein the fluid in the first chamber and/or second chamber is a different fluid from that supplied by the fluid supply means.
22. A tool as claimed in claim 19 or 20, wherein the fluid in the first chamber and/or second chamber is the same fluid as supplied by the fluid supply means.
23. A tool for interfacing with a drillstring, substantially as described herein with reference to and as shown in the accompanying drawings.