FIELD OF THE DISCLOSURE

This disclosure relates to apparatus and methods for use in coupling tubing such as used in the creation, maintenance and use of bores drilled in the earth. BACKGROUND OF THE DISCLOSURE

In the oil and gas exploration and production industry bores are drilled from the surface of the earth to create wells for accessing subsurface hydrocarbon-bearing formations. The bores may be drilled using drill bits mounted on the ends of tubular supports, some of which are described as drill strings. The drill strings may be formed of sections of drill pipe which are coupled together using threaded end connections. Many other operations carried out in oil and gas wells utilise similar tubular strings, for example to locate tools or devices in the well.

During a typical drilling operation the upper end of the drill string is coupled to an arrangement commonly referred to as a top drive. The top drive may be pulley or rail-mounted above the rig floor and includes a motor coupled to a fluid transmitting output shaft. The shaft will normally be provided with a saver sub, a short hollow sacrificial coupling including a male thread for screwing into the upper end of the drill string. During a drilling operation fluid is pumped through the top drive and the saver sub and into the drill string while the top drive motor is operated to rotate and apply torque to the drill string. The top drive may be lowered and raised to apply weight or tension to the drill string, to provide the desired weight-on-bit.

Following an initial bore-drilling operation, the resulting bore may be lined with larger diameter tubing strings, typically known as casing or liner. Further tubing strings may be located within the casing and liner and used to, for example, carry fluids between the well and surface.

As noted above, fluid will be pumped into the drill string via the top drive during a drilling operation. However, there will be various other occasions when it is desirable or necessary to flow fluid into a tubing string, particularly as a tubing string is being made up and run into a well, or retrieved from a well. Typically, this requires the top drive saver sub to be screwed into the upper end of the drill string before the operation commences, and then unscrewed from the string following completion of the operation. SUMMARY

According to an aspect of the present disclosure there is provided a coupling apparatus configured to be positioned between an upper end of a tubing string and a top drive and configured to be held in position between the upper end of the tubing string and the top drive by lowering the top drive onto the apparatus, the apparatus comprising a fluid-transmitting body, a fluid inlet for communication with the top drive and a fluid outlet for communication with the upper end of the tubing string, whereby the coupling apparatus provides a fluid-tight coupling between the top drive and the tubing string. According to another aspect of the disclosure there is provided a method of directing fluid into a tubing string, the method comprising locating a coupling apparatus between a top drive and an upper end of a tubing string, lowering the top drive onto the coupling apparatus to locate an inlet of the coupling apparatus in sealing engagement with the top drive and an outlet of the coupling apparatus in sealing engagement with the upper end of the tubing string to provide a substantially fluid-tight coupling between the top drive and the tubing string, and pumping fluid from the top drive, through the coupling apparatus, and into the tubing string.

The coupling apparatus may comprise at least one seal for engaging the top drive or the upper end of the tubing string. Sealing contact between the apparatus and the top drive or the tubing string may be effected solely by relative axial movement. Lowering the top drive onto the apparatus may compress the at least one seal provided on the apparatus. The at least one seal may be deformable or resilient. The at least one seal may be effective over a range of relative axial positions, to accommodate the difficulty in accurately axially locating the top drive relative to the apparatus and the tubing string.

The at least one seal may be configured to withstand or absorb impacts or shocks, as may be created by downward movement of the top drive onto the coupling apparatus; a top-drive may have a mass of 30,000 - 60,000 lbs (13,608 - 27,216 kg). The at least one seal may include a relatively thick seal member, for example a seal member having a thickness in excess of ½ inch (12.7mm), in excess of 1 inch (25.4mm), or in excess of 1 ½ inches (38.1 mm). Seal members for the apparatus may comprise a natural or synthetic rubber, for example a nitrile rubber. The rubber may be relatively hard, that is having a Shore hardness of greater than 60, greater than 70, or greater than 80.

The coupling apparatus may comprise a seal for engaging a lower end of the top drive, which may be the lower end of a saver sub; any references herein to providing connections or couplings with a top drive are intended to encompass providing connections or couplings with a saver sub or the like. The seal may serve as a fluid inlet seal. The seal may comprise an annular gasket.

The coupling apparatus may comprise a seal for engaging an upper end of the tubing string. The seal may be configured for engaging an upper end surface of the tubing string, for example the seal face of a box connection, and in one example an inner edge of the seal face. The seal may serve as a fluid outlet seal.

The upper and lower seals may be associated with upper and lower support surfaces. The upper support surface may face upwards and the lower support surface may face downwards. The support surfaces may be provided on opposite faces of a support member which, in use, extends at least partially across the open upper end of the tubing string.

The coupling apparatus may include a guide portion to facilitate mating of the coupling apparatus with the top drive. The guide portion may be configured to facilitate mating when there is at least an initial misalignment of the coupling apparatus and the top drive. Such misalignment may be as a result of a misalignment of the top drive and the tubing string. The guide portion may taper inwards to provide an upper or leading end portion of relatively small diameter. The end portion may be of smaller diameter than an internal diameter of a top drive coupling, typically a top drive saver sub. The end portion may taper to a rounded point. Thus, the end portion may pass into the top drive coupling, even if there is a degree of misalignment between the coupling apparatus and the top drive. By providing a tapered end portion the degree of misalignment accommodated by the guide portion may be almost half the diameter of the internal diameter of the top drive coupling. The end portion may be closed. The fluid inlet may be provided below the end portion.

The guide portion may include an elongate portion for extending into the top drive, or at least into a saver sub provided on the top drive. The top drive or saver sub will likely be provided with a threaded pin connection and the guide portion may be configured to extend into the pin. Alternatively, or in addition, an elongate portion may be provided for extending into the upper end of the tubing string. The elongate portion may be hollow. The elongate portion may be configured to permit transverse flow into or out of the portion and may be configured to permit axial flow through the portion. The elongate portion may be configured to facilitate fluid flow externally of the portion. In one example the elongate portion may be dimensioned to provide a fluid flow path between the portion and a surrounding inner wall surface of a top drive outlet.

The elongate portion may comprise a wall including a plurality of flow openings. In one example the elongate portion comprises a tube having a perforated wall. The elongate portion may serve as a handle, facilitating manual handling and positioning of the apparatus.

The coupling apparatus may include at least one centraliser to facilitate location of the apparatus relative to the top drive or the tubing. The centraliser may include a tapered, bevelled or chamfered surface. The centraliser may be provided at a base of the elongate portion. Alternatively, or in addition, a centraliser may be provided to locate the apparatus centrally of the open upper end of the tubing string.

The coupling apparatus may comprise a thread protector for shielding a thread at the upper end of the tubing string. The thread protector may be configured to extend into the upper end of the tubing string between the tubing thread and the fluid flowing into the tubing, and may comprise an inverted cup form. The thread protector may have a form that is complementary to the thread to be protected: for example, drill tubing or pipe may feature a female or box section having a threaded portion which tapers inwardly from the upper end of the tubing and is configured to engage with a threaded tapered male or pin section; the thread protector may have a similar form to a drill pipe pin section, but does not feature a thread. The thread protector may be configured to guide the apparatus into the tubing string and to centralise the apparatus relative to the string. The thread protector may form the lowermost portion of the apparatus. The apparatus may thus extend a relatively short distance into the upper end of the tubing string, facilitating mounting and demounting of the apparatus from the tubing string.

The coupling apparatus may be configured to facilitate manual handling. The coupling apparatus may have a mass of 50 lbs (22.7kg) or less such that one person may lift and position the apparatus on the upper end of the drill string without mechanical assistance. The apparatus may have a mass of less than 45 lbs (20.4kg), less than 40 lbs (18.1 kg), less than 35 lbs (15.9kg), less than 30 lbs (13.63kg), less than 25 lbs (1 1.3kg), less than 20 lbs (9.1 kg), or less than 15 lbs (6.8kg). According to another aspect of the disclosure there is provided a method of translating an activating device through a tubing string, the method comprising: inserting an activating device into a tubing string; locating a coupling apparatus on the upper end of the string; lowering a top drive to engage the coupling apparatus; and pumping fluid from the top drive, through the coupling apparatus and into the string to translate the activating device through the string.

The coupling apparatus of this and other aspects of the disclosure may incorporate features of the coupling apparatus as described above, and as recited in the appended claims, either singly or in combination.

The use of the coupling apparatus may facilitate rapid initiation of pumping following insertion of the activating device into the string. In particular, in the absence of the coupling device it would be conventional to make up a threaded connection between the top drive and the tubing string. Examples of the coupling apparatus may provide a fluid-tight coupling between the top drive and the tubing string merely by lowering the top drive onto the coupling apparatus. The activating device may comprise a dart or ball, or may comprise one or more

RFID tags.

According to a further aspect of the present disclosure there is provided coupling apparatus configured to be positioned between an upper end of a tubing string and a top drive, the apparatus comprising a fluid-transmitting body, a guide portion for aligning the coupling apparatus with the top drive as the top drive is lowered onto the coupling apparatus, a fluid inlet provided below an upper end of the guide portion and a fluid outlet, whereby the coupling apparatus provides a fluid coupling between the top drive and the tubing string.

The guide portion may facilitate mating when there is at least an initial misalignment of the coupling apparatus and the top drive. The guide portion may taper inwards towards an upper or leading end portion. The guide portion may have a tapered end, which may feature a rounded point. The end portion may be of smaller diameter than an internal diameter of a top drive coupling, typically a top drive saver sub which may be provided with a threaded pin connection. Thus, the end portion may pass into the top drive coupling, even if there is a degree of misalignment between the coupling apparatus and the top drive; by providing a tapered end portion the degree of misalignment readily accommodated by the guide portion may be up to half the diameter of the internal diameter of the top drive coupling. The end portion may be closed to fluid flow.

BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view from above of coupling apparatus in accordance with an example of the present disclosure;

Figure 2 is a perspective view from below of the coupling apparatus of Figure 1 ; Figure 3 is a sectional view of the coupling apparatus of Figure 1 ; and

Figure 4 is a sectional view of the coupling apparatus of Figure 1 in use.

DETAILED DESCRIPTION OF THE DRAWINGS

The accompanying figures illustrate a coupling apparatus 10. As will be described, the illustrated apparatus 10 may be utilised to facilitate rapid coupling and decoupling of a fluid-tight connection between a top drive and a tubing string. In the illustrated example the apparatus 10 is utilised to allow fluid to be pumped into a drill string 12 (Figure 4). Typically, this will occur as the drill string 12 is being made-up and run into a bore, or as the drill string is being retrieved or tripped out of the bore.

The apparatus 10 comprises a hollow body 14 defining an axial through bore 15, an upper guide portion 11 incorporating an inlet portion 16, and a lower outlet portion 18. The body 14 of the illustrated example is an assembly of a number of metallic parts which are threaded together. The guide portion 11 comprises a hollow tube 20 with a perforated wall 22, and a tapered nose portion 24 which closes the upper end of the tube 20 at a rounded point. The lower end of the tube 20 is provided with an external thread 42 which engages an internal thread 44 formed in the upper end of an inverted cup member 26 which forms the outlet portion 18. The hollow tube 20 defines a bore 28 contiguous with a passage 30 extending through the upper end of the cup member 26 and opening into a larger diameter exit passage 32.

An annular upper face 34 of the cup member 26 is substantially planar and carries an annular resilient seal or gasket 36. The seal 36 is held in place by a frusto- conical centraliser 38 which is threaded to a stepped boss 40 which extends upwardly from the upper face 34. The tube-engaging thread 44 is provided in the upper end of the boss 40.

The cup member 26 includes a circumferential lip 46, a lower face of the lip 46 defining an undercut groove 47 for retaining a seal 48. An inner face of the seal 48 is engaged by a ring 50 which is an interference fit on an upper outer surface of a pin profile 52.

The pin profile 52 forms the lower portion of the cup member 26 and has a tapering form generally similar to the form of a threaded pin connection, but has a smooth external surface. The seal-retaining ring 50 sits at the upper end of the pin profile 52 and is dimensioned to, in use, mate with the profile 57 (Figure 4) directly above the box thread 59. As the pin profile 52 is not load-bearing the pin profile wall 53 may be relatively thin, to assist in keeping the weight of the apparatus down. However, the cup member base 55 may experience significant loads, supporting at least a portion of the weight of a top drive on the top of the drill string, and thus is of heavier construction.

Figure 4 of the drawings illustrates, somewhat schematically and in addition to the coupling apparatus 10 and upper end of the drill string 12 (sometimes referred to as the "stick-up"), a rig floor 60, slips 62, and the lower portion of a top drive 64. The top drive 64 includes a protective shroud 66, a saver sub 68, and stabbing guides 70 on an inside surface of the shroud 66. The saver sub 68 includes a threaded pin 72 which may be engaged with a threaded box 74 on the upper end of the drill string 12. During a drilling operation the top drive motor may rotate the saver sub 68, via the top-drive drive shaft, which in turn rotates the drill string 12. Further, the top drive 64 may support the drill string 12, that is apply a tension to the string 12, or the top drive 64 may be utilised to apply weight or compression to the string 12. If the threads of the pin and box connections 72, 74 are clean and fully made up there is a fluid-tight coupling between the saver sub 68 and the drill string 12, allowing drilling fluid to be pumped into the drill string 12 via the top drive 64.

The top drive 64 may be rail or pulley-mounted and may be raised and lowered relative to the rig floor 60. As noted above, during a drilling operation the top drive 64 is coupled to the drill string 12 via the saver sub 68 and the drill string 12 may be raised and lowered with the top drive 64. However, while making up or retrieving a drill string there may be stages of the operation when there is no requirement for rotation of the string 12 or circulation of fluid through the string 12, and thus no requirement to couple the top drive 64 to the drill string 12; this requires the threaded saver sub pin connection 72 to be made up (screwed on) to or separated (screwed off) from the threaded drill string box connection 74. Rather, the rig will be provided with elevators (not shown) which clamp around the drill string 12 below the box 74 and permit the drill string 12 to be raised and lowered. The elevators may engage and disengage with the drill string 12 quickly and without risking damage to the threads on the saver sub 68. Although the saver sub 68 is provided as a sacrificial coupling, and will likely be subject to some wear and damage during normal usage, replacement of a saver sub is still time-consuming and difficult, and an unscheduled saver sub replacement may be very disruptive to rig operations.

Conventionally, if top-filling of the drill string 12 is required during the running in or retrieving of the string, that is the upper end of the string 12 is filled with air it is desired to replace with liquid, the operator will position the saver sub 68 a short distance above the drill string box connection 74 and trickle drilling fluid into the string. This allows the air displaced by the drilling fluid to pass out of the open top of the drill string. Alternatively, the operator may provide an apparatus as described in US Patent Nos 7,975,766 and 8,915,299, both to Churchill. Apparatus described in the Churchill patents permits a top-filling operation to be carried out relatively quickly by, for example, allowing displaced air to exit the drill string without disrupting the flow of drilling fluid into the string. However, if it is desired to circulate fluid through the string, or otherwise pressurise the fluid in the string, the saver sub 68 is screwed into the drill string box connection 74 to create a fluid-tight coupling.

If a drill string is being run into a bore, the drill string is likely to be made-up by adding a stand of tubing or pipe to the drill string 12 while the drill string is supported at the rig floor 60 using the slips 62. The stand of pipe is supported by the elevators, which may hang below the top drive 64, and is lowered towards the rig floor 60 such that the pin connection on the lower end of the stand engages with the box connection at the upper end of the string. Tongs may be used to make-up the connection by rotating the pipe stand while holding the drill string stick-up stationary. The elevators may then be used to raise or support the stand, now coupled to the drill string, so that the slips 62 may be released. The drill string 12, including the newly-added stand, is then lowered into the bore until the upper end of the newly-added stand approaches the level of the rig floor 60. The slips 62 are then redeployed to engage and support the string 12, such that the elevators may then be employed to engage and position another stand, ready for connection to the drill string 12. As noted above, from time-to-time it is desirable or necessary to pump liquid, typically in the form of drilling fluid, into the string. According to this example of the present disclosure this is achieved by an operator manually lifting the apparatus 10 onto the drill string 12 and locating the pin profile 52 in the box connection 74 at the upper end of the drill string 12. Typically, the apparatus 10 will have a mass of less than 50 lbs (22.7kg) to facilitate manual handling by one person and the tube 20 may serve as a handle; an apparatus 10 fabricated primarily from steel and for use in combination with full-hole connections provided on 6 5/8 inch (168mm) drill pipe (the largest drill pipe in common usage) may have a mass of approximately 18 lbs (8.2kg). The pin profile 52 is relatively shallow and thus the apparatus 10 does not have to be lifted far above the upper end of the stick-up 12 to locate the pin profile 52 in the box connection 74. The apparatus 10 also self-centres in the box 74, such that no manual repositioning of the apparatus 10 should be necessary. The apparatus 10 will sit in the box connection 74 with the lower seal 48 resting on the upper face 80 of the box. The pin profile 52 covers most if not all of the box connection thread. The tube 20 extends vertically upwards from the top of the drill string.

An operator then lowers the top drive 64 such that the saver sub 68 and the saver sub pin 72 passes over and onto the hollow tube 20, the correct relative lateral positioning of the saver sub 68 and tube 20 being facilitated by the tapered end of the nose portion 24 and the centraliser 38 at the base of the tube 20; no manual adjustment of the relative positioning of the parts is likely to be required. In normal operations on a rig, there will often be a degree of misalignment between the upper end of the drill string 12 and the top drive 64. Given the significant mass of a typical top drive (30,000 to 60,000 lbs (13,608 - 27,216kg)), such misalignment has the potential to cause damage to the mating parts when the top drive 64 and the drill string 12 are brought together. The provision of the nose portion 24 with a tapered end allows the nose portion 24 to pass safely into the saver sub 68 even when there is degree of misalignment; the illustrated example features a saver sub with an internal diameter of 4 or 4 1/4 inches (102 or 108mm) and will accommodate up to 2 inches (51 mm) of misalignment. The saver sub 68 is then guided down the tube 20 and any remaining misalignment is accommodated and corrected by the centraliser 38. The top drive 64 is lowered until the lower end face of the saver sub 68 engages and compresses the gasket seal 36, the weight of the top drive 64 supported by the apparatus 10 also serving to ensure contact between the seal 48 and the upper end face of the drill string 80. The compressed seal 36 thus ensures a fluid-tight coupling between the end of the saver sub pin 72 and the coupling apparatus 10 around the inlet portion 16, and the compressed seal 48 ensures a fluid-tight coupling between the upper end face of the drill string 80 around the outlet portion 18.

As noted above, the top drive 64 is likely to have a significant mass, such that the apparatus 10 must be sufficiently robust to support at least a proportion of the mass of the top drive 64, and also to absorb significant impact loads should the operator lower the top drive 64 onto the apparatus 10 too quickly, or misjudge the vertical positioning of the top drive 64 relative to the string 12. This may be achieved by providing a robust cup member base 55 and a relatively thick gasket seal 36. In one example, a 2 inch (51 mm) thick and relatively hard (90 Shore) nitrile rubber gasket 36 may be provided.

As is apparent from Figure 4, the hollow tube 20 of the guide portion 1 1 is dimensioned to extend into the saver sub 68 while retaining an annular clearance around the tube 20. Thus, fluid may flow through the saver sub 68, around the tube 20, and then through the perforated tube wall 22. The fluid may then pass through the short passage 30, out of the exit passage 32, and into the drill string 12.

In a top-filling operation there may be situations where the operator judges that there is no requirement to accommodate displaced air. In such circumstances the apparatus 10 may be utilised and liquid may be pumped into the string at a relatively high flow-rate. The air which filled the upper end of the string is dispersed in the liquid which is introduced into the string.

The apparatus 10 is self-centring on the stick-up and also, as noted above, centres the top drive 64 as the saver sub 68 is lowered onto the tube 20, thus facilitating handling and requiring little if any manual positioning. The ability of the apparatus 10 to provide a fluid-tight coupling between the top drive 64 and the drill string 12 merely by compressing the apparatus 10 between the top drive 64 and the drill string 12, removes any requirement for the saver sub 68 to be screwed into the drill string box connection 74, which saves time and reduces the risk of wear and damage to the saver sub 68. The protection of the box connection thread 59 by the pin profile 52 also avoids any dope or grease which has been applied to the thread 59 being washed away by the flow of fluid, such that re-coating of the thread 59 before making up the next connection should be unnecessary. The operation will be completed once a sufficient volume of fluid has been pumped into the string 12. The top drive 64 is then raised until the shroud 66 is clear of the apparatus 10. The operator may then remove the apparatus 10 from the upper end of the string 12. As noted above, the tube 20 provides a convenient handle, allowing the operator to tilt the apparatus 10 on the string 12 and free the apparatus 10 from the box. If the apparatus 10 has become stuck in the box connection 74, the operator may pull laterally on the tube 20 to apply leverage to the body 14; given the close fit between the pin profile 52 and the box 74 and the likely presence of dope or grease on the box thread 59, it is likely that the abutting surfaces will have "stuck" together. The presence of the perforations in the tube 20 also enhances the operator's grip on the outer surface of the tube 20, which may be coated with drilling fluid.

The apparatus 10 may also be employed to top-fill or circulate fluid in a drill string 12 being retrieved from a well. For example, it may be desired to retrieve or trip a drill string with the upper end of the drill string "dry", and filled with air rather than liquid. This may be possible where a lower portion of the drill string is in fluid communication with the bore annulus, such that fluid may drain from the string 12 as the string is raised out of the well. Ensuring that the upper end of the string is substantially free of fluid may be achieved, for example, by pumping a volume or slug of relatively heavy fluid into the drill string. Conventionally, this will be achieved by screwing the saver sub 68 into the string 12, pumping in a volume of heavy-weight fluid, and then unscrewing the saver sub 68 from the string 12. The heavy slug of liquid displaces the lighter fluid in the string and annulus, such that air may fill the upper end of the string. However, there may be occasions when it is desirable to have the upper end of the "dry" string filled with fluid, and in such a situation the drill string must be top-filled. Conventionally, this is achieved by running drilling fluid into the open end of the string 12 from the end of the saver sub 68. However, with the apparatus 10 of the present disclosure, this may be achieved more rapidly and as described above, by an operator trapping and sealing the apparatus 10 between the top drive 64 and the drill string 12 and then pumping an appropriate volume of heavier liquid into the string 12, via the apparatus 10.

This top-filling of the string 12 may be required to allow a dart or ball to be safely dropped or pumped down through the string 12 to activate a tool in the string, for example to open a bypass tool. A bypass tool may be opened as the tool is located at a wellhead provided with a blow-out preventer (BOP), to allow fluid to be jetted out of the bypass tool and clean the BOP. Of course this cleaning or jetting process may be utilised in other devices within the well, for example in nipples or valves.

Once a dart or other activating device is placed in the string 12, it may be desired to commence pumping fluid into the string 12 relatively quickly, for example to provide the dart with the velocity necessary to engage properly with the tool in the string. Conventionally, this would require the saver sub 68 to be screwed into the upper end of the drill string 12 before pumping could commence. This operation will typically take several minutes. In contrast, the apparatus 10 of the present disclosure may be located on the drill string immediately after the dart has been placed in the string 12, the top-drive 64 lowered to engage and seal with the apparatus 10, and the fluid pumps started, all within a matter of seconds. Furthermore, once the jetting of the BOP has been completed, the apparatus 10 may be demounted from the string 12 very quickly, simply by raising the top drive 64 and then lifting the apparatus 10 off the string 12.

The examples described above are merely exemplary, and the apparatus and methods described may be utilised in many different operations and in combination with a range of tubulars, including tool strings, completions, liner and casing. For example, the apparatus and methods of the disclosure may be employed in pressure testing tubing, translating an activating device such as a dart or ball through a tubing string, pumping a slug of heavy fluid into tubing, or providing fluid circulation through a tubing string. For example, while pulling a string out of a well or running a string into a well, it may be desirable to provide fluid circulation from time-to-time, to maintain the condition of the drilling fluid and prevent gelling or thickening of the fluid, to circulate fluid having different properties into the well, or to cool the Bottom Hole Assembly (BHA) in a "hot" well. The disclosed apparatus and method facilitates pumping or circulation of fluid without the requirement to first screw on and then screw off a threaded connection; the ability to provide a fluid-tight coupling between a top drive and a tubing string merely by placing the apparatus on the upper end of the tubing and then lowering the top drive onto the apparatus to engage the seals provides a valuable saving in rig time. In many of the operations described herein, the circulation or pumping operation may be relatively short. As noted above, where it is desired to retrieve or trip a drill string "dry" with the upper end of the string filled with air, a slug of relatively heavy liquid is pumped into string; pumping a 30 barrel slug of heavy fluid into a string at 10 barrels a minute will only take 3 minutes, however screwing on and subsequently screwing off a threaded connection prior to and following the pumping operation will typically take around 10 minutes. Thus, it is anticipated that some operations may be completed using the apparatus and methods of the present disclosure in less the 30 or 40% of the time currently required. The ability of the disclosed apparatus to accommodate a degree of misalignment between the drill string and the top drive also saves time that would otherwise have to be spent ensuring proper alignment and also minimises the risk of damage when misaligned parts are brought together. Operator safety is also enhanced, as less manual intervention will be required in ensuring that the parts are aligned.

In addition to the cost savings generated by the time-efficiencies made available through use of the disclosed apparatus, there may also be operational advantages gained by initiating circulation of fluid relatively quickly once a string 12 has been set in the slips 62. As described above, it may be advantageous to initiate pumping of fluid behind a dart to ensure the dart lands on a tool at an appropriate velocity, or the rapid initiation of fluid circulation may render differential sticking less likely when a string is being held stationary in a bore. The ability to initiate circulation quickly may also offer advantages in well control and in freeing stuck pipe.

The apparatus 10 may also be utilised to maintain fluid circulation in situations where, for example, the power supply to the top drive 64 has failed, such that the top drive motor cannot be operated to make up the threaded connection between the saver sub 68 and the drill string 12. Is such a case, the apparatus 10 may simply be positioned on the string 12 and the top drive 64 lowered to make the seals 36, 48 effective, such that the pumps may then pump fluid into the string 12 via the fluid-tight connection provided by the apparatus 10.

In other examples, a shorter guide portion 1 1 may be provided; the illustrated example may have a tube and nose portion which is approximately 12 inch (305mm) long. While a shorter guide portion 11 may facilitate provision of a lighter-weight apparatus, the shorter tube 20 will provide less mechanical advantage when freeing an apparatus that has become stuck on the box connection. Accordingly, such an apparatus may be provided in combination with a longer and larger diameter tube or pipe that may be placed over the guide portion 11 and then used as a lever, or a tool that may be used to prise the apparatus off the box connection 74. Of course the apparatus may be formed of different materials, such as lighter aluminium alloy, or have non-loadbearing parts formed of composite or plastics materials.

In the illustrated example, the apparatus 10 includes seals 36, 48 which rely on the apparatus 10 being compressed to some extent between the top drive 64 and the drill string 12. In other examples, alternative or additional seal forms may be provided. One or more cup seals may be provided to engage an inner surface of the saver sub 68 and/or an inner surface of the tubing string. An apparatus provided with upper and lower cup seals may provide a fluid-tight connection without requiring compression of the apparatus. The apparatus may also be provided with seals which are arranged or configured to be energised or extended by flow or pressure, facilitating sealing against surfaces of different internal diameters.