This invention relates to an apparatus and method for inserting coiled tubing into a sub-sea pipeline, particularly for remediation activities such as hydrate and wax remediation.

In the subsea oil and gas industry it is common to remove wax scale, hydrates and other such deposits from the bore of a flowline by pushing a cleaning device, referred to as a pig, through the flowlines using fluid pressure. In some instances, flowlines can become totally blocked by wax and hydrates, and use of conventional pigs is not possible. In these situations, the blockage can be removed by de-pressurising the flowline and raising the blocked flowline section from the sea bed to the surface. At the surface, coiled tubing can be inserted into the flowline section to deliver pressurised remediation chemicals, such as methanol, to the blockage to help disassociate the hydrate from the pipe wall. A coiled tubing pulling device can be attached to the coiled tubing to provide a thrust load to help pull the coil tubing deep into the flowline. Pulling devices such as a thruster pig or coil tubing tractor can be used. Return fluids can either be directed up the coil tubing bore or into the annulus between the coil tubing and the flowline bore.

An example of such a coiled tubing pulling device is disclosed in WO 03/067016. A retrievable pig apparatus is secured to an end of coiled tubing, the pig having a plurality of flexible cups around the body of the pig. When the pig is positioned in a pipeline, the cups engage the inner surface of the pipeline so as to prevent fluid flow between the inner surface of the pipeline and the pig. Fluid can be directed down the annulus between the pipeline and the coiled tubing at a predetermined pressure such that the pressurised fluid pushes the pig forward in the pipeline, the pig pulling the coiled tubing along as it travels forward. When the pig encounters a blockage, the pressure of the fluid directed down the annulus between the pipeline and the coiled tubing is increased, causing valves in the pig to open, permitting fluid to flow through the pig towards the blockage. Debris removed from the blockage is returned in a flow of fluid which passes through bores in the pig which communicate with a channel through the pig which in turn communicates with the interior of the coiled tubing.

To date, this system has only been used in hydrate remediation activities at the surface. WO 2004/033850 discloses a flow assurance system in which an inner pipe is disposed within an outer pipe, such as a flowline, to assure flow through the outer pipe. The inner pipe may be inserted at the surface into the top of the flowline riser. Alternatively, the inner pipe may be installed from a floating vessel such that it may be inserted at any point along the flowline. The inner pipe may be installed using a Swift Riser as described in US 6386290. However, no such arrangement has been commercialised to date and so no solution has been provided in practise.

Sub-sea pipeline blockages can cause the pipeline to stop flowing, and are therefore very serious problems. Currently available techniques for removing the blockage can take a number of months, particularly since the kind of equipment needed can not always be acquired immediately. Blockages are therefore very costly to a production facility. It is therefore highly desirable to deliver an apparatus and method which can be implemented easily to remove blockages.

The invention has been made with these points in mind.

According to a first aspect of the present invention, an apparatus for inserting coiled tubing into a sub-sea pipeline comprises an adaptor which is releasably couplable to an anchor to hold the adaptor in position against lateral and/or vertical forces, wherein the adaptor has: i) a first end comprising first coupling means for releasably coupling the adaptor to a riser and an opening through which coiled tubing can extend, ii) a second end comprising second coupling means for releasably coupling the adaptor to the anchor, and iii) a curved guide comprising an entrance end facing the opening and an exit end, the curved guide being in communication with the opening such that coiled tubing from the riser can extend through the opening and along the curved guide, the curved guide, in use, guiding the coiled tubing from a substantially vertical orientation at the entrance end to a substantially horizontal or near-horizontal orientation at the exit end.

According to a second aspect of the present invention, a method for inserting coiled tubing into a sub-sea pipeline comprises lowering an adaptor into contact with an anchor fixed to the sea bed, the adaptor having: i) a first end having first coupling means for releasably coupling the adaptor to a riser and a first opening through which coiled tubing can extend, ii) a second end having second coupling means for releasably coupling the adaptor to the anchor, and iii) a curved guide comprising an entrance end facing the opening and an exit end, the curved guide being in communication with the opening such that coiled tubing from the riser can extend through the opening and along the curved guide, the curved guide, in use, guiding the coiled tubing from a substantially vertical orientation at the entrance end to a substantially horizontal or near-horizontal orientation at the exit end; releasably coupling the adaptor to the anchor and feeding coiled tubing through the first opening of the adaptor and through the curved guide so that the coiled tubing exits the curved guide substantially horizontally or near-horizontally.

The present invention provides a simple solution which can be implemented quickly and easily since it enables existing sub-sea equipment and tools to be used to insert coiled tubing into a sub-sea pipeline such as a flowline.

In the exploration and production field, it is very well known to position a "Christmas tree" on the sea-bed over the top of a sub-sea well bore. A Christmas tree is, in general terms, an assembly of valves and conduits, and it serves to control the flow of fluids and the movement of equipment to/from a well bore. It is well known to connect a riser to a Christmas tree to allow well fluids to flow temporarily to a surface facility as well as to conduct well interventions. For example, it is common to deploy a work over riser, typically a completion work over (CWO) riser, from a mobile offshore drilling unit during well interventions such as fluid circulations, well clean up operations or well stimulation operations. The CWO riser is connected to the Christmas tree located at the top of the well bore. Coiled tubing is passed down the riser and through the Christmas tree into the well bore to carry out the intervention. The resources and expertise to carry out such interventions are available currently.

The present invention harnesses this known technique thereby enabling coiled tubing to be inserted into a sub-sea pipeline. The adaptor of the invention is intended to mimic to a certain extent a Christmas tree so that a riser can be deployed and can couple to the Christmas tree in the known manner. In this way, the coiled tubing can also be deployed in accordance with the conventional techniques for deploying coiled tubing into a well. However, due to the nature of the adaptor provided by the invention, and particularly the provision of a curved guide, the coiled tubing is redirected from a substantially vertical orientation inside the riser to a substantially horizontal or near-horizontal orientation. In the substantially horizontal or near-horizontal orientation, the coiled tubing can be aligned with a nearby flowline entry point, such as a flowline termination assembly (FTA) (also known as a pipeline end termination or PLET) at the end of a flowline, a flowline 'T' which is a connector part-way along a flowline, or an assembly such as that described in our co-pending US application, serial number 12/081574, titled "Pipeline Intervention". The assembly described in US serial number 12/081574 enables coiled tubing to be inserted into a pipeline at an angle of up to 10°, but preferably up to 5° and more preferably up to 2° to the horizontal. Accordingly, in the present invention, near-horizontal means up to 10°, but preferably up to 5° and more preferably up to 2° to the horizontal.

The invention therefore has the important benefit that known apparatus and techniques for deploying a riser and for deploying coiled tubing within the riser for well operations can be used in this new scenario with the adaptor of the invention.

The riser can be any riser known in the art and so may be in the form of jointed sections or a spoolable riser. For example, the riser may be a CWO riser, a light well intervention (LWI) riser, a drilling riser or the Swift riser disclosed in US 6386290. The riser may be tensioned or not. The riser may be deployed from various types of vessel or facility, including a mobile offshore drilling unit (MODU), a drillship or jackup rig in the case of the CWO, LWI or drilling riser, or from a multi-purpose support vessel or LWI vessel (i.e. a rigless well intervention vessel) in the case of the Swift riser or LWI riser. The riser may also be deployed from a fixed platform.

The anchor may be a conventional pile. Piles are well known in the art and are pieces of equipment, typically tubular in shape, that are secured to the seabed to provide a means of stabilising subsequent pieces of equipment, such as risers, sub sea. The pile supports the subsequent pieces of equipment against external loads and bending moments. Piles can be long, thin tubular members or shorter, wide tubular members. Short, wide members are also sometimes known as caissons. Suitable techniques for securing the pile to the sea bed are well known to the person skilled in the art, and include (a) drilling a suitably oversized hole, deploying the foot of the caisson into the hole and cementing the annular volume around the foot of the caisson; (b) driving the pile directly into the sea bed; (c) evacuating the interior of the pile, causing the surrounding pressure to drive the pile into the sea bed (suction installed); or (d) jetting a fluid into the sea bed to create a bore into which the pile is inserted as the bore is formed. The upper end of the pile is proud of the seabed and has a profile to allow connection of the other pieces of equipment thereto.

In a convenient embodiment, the first and second ends of the adaptor are at opposing ends of an adaptor body. Side walls of the adaptor body can separate the first and second ends. The adaptor body may have a generally circular cross section, for example.

The curved guide is essentially an arcuate conduit which curves along at least a portion of its length so that it can guide coiled tubing from one orientation to another, substantially perpendicular orientation. The central axis through the entrance end of the curved guide is co-axial with the central axis extending through the adaptor body from the first end to the second end of the adaptor. Typically, in use, the central axis through the entrance end of the curved adaptor is substantially vertical such that the entrance end of the curved guide is aligned with the central axis through the riser (at the base of the riser). The central axis through the exit end of the curved guide is substantially perpendicular or near- perpendicular to the central axis through the entrance end. By near-perpendicular, it is meant that the central axis through the exit end of the curved guide makes an angle of at least 80°, preferably at least 85° and optionally at least 88° to the central axis through the entrance end.

The curved guide preferably has a generally circular cross-section. This means that the inner surface of the curved guide is generally complementary in shape to the outer surface of the coiled tubing. The curved guide has a diameter which allows a clearance between the outer surface of the coiled tubing and the inner surface of the curved guide such that a fluid can flow easily through the annular space between the coiled tubing and the curved guide.

Advantageously, the curved guide has a large radius of curvature so that the coiled tubing bends gently as it is guided from the vertical to the horizontal/near-horizontal orientation. Preferably, the radius of curvature is at least about 20 times, and typically no more than 40 times, the outer diameter of the coiled tubing to be used. Preferably, the radius of curvature is between 20 and 30 times the outer diameter of the curved guide. A large radius of curvature reduces 'capstan' friction. The curved guide can extend through a side wall of the adaptor body, for example through an opening in the side wall, so that the exit end of the curved guide is outside the adaptor body. The opening can be generally circular, though could be in the form of an elongate slot if appropriate, for example to allow some movement of the curved guide or to allow height adjustment of the curved guide as described below.

The apparatus may be used to carry out flowline interventions, for example to remove blockages. The intervention may be carried out by simply passing fluid down coiled tubing into the flowline. Alternatively, the apparatus may include a pipeline intervention tool which is couplable to the coiled tubing. The intervention tool may be a pig,, tractor or other known intervention device, for example the coiled tubing pulling device described in WO 03/067016.

Preferably, the apparatus further comprises a launcher which has a channel extending there-through for housing the pipeline intervention tool, the launcher being couplable downstream of the adaptor so that coiled tubing extending from the exit of the curved guide of the adaptor can extend into the channel through the launcher to couple to the intervention tool. The downstream direction is in the direction in which coiled tubing is moved when inserting it into a pipeline. Accordingly, movement from the entrance end of the curved guide to the exit end of the curved guide is movement from the upstream end to the downstream end. This feature of the invention means that the intervention tool need not be deployed from the surface attached to the coiled tubing. This is beneficial since the intervention tool need not be capable of manoeuvring through the riser or the curved guide, which can consequently have smaller diameters than the maximum diameter of the intervention tool.

Optionally, a transition element may be provided between the exit of the curved guide and the launcher, the transition element comprising a channel there-through for conducting coiled tubing from the curved guide to the launcher. Preferably, the channel has an entrance adjacent the exit of the curved guide and an exit adjacent the launcher. The transition element is provided to bridge the gap between the exit of the curved guide and the entrance of the launcher. Where no launcher is required, for example if coiled tubing is being inserted into the pipeline without the need for a pipeline intervention tool, the transition element simply bridges the gap between the exit of the curved guide and the flowline access point.

The transition element is preferably adapted to accommodate one or more of a separation or a vertical, lateral or rotational misalignment between the exit of the curved guide and the entrance to the launcher. A separation may exist between the curved guide and the launcher because the anchor cannot be secured to the sea bed immediately adjacent the launcher. This can be because setting the anchor into the sea bed immediately adjacent the launcher would damage the nearby flowline access point due to its proximity. Additionally, the sea bed may be too rocky in a particular area to allow the anchor to be set there. The anchor may therefore be secured some distance away from the launcher.

A misalignment could arise (i.e. the anchor may not lie along the axis of the flowline at the flowline access point) also because the sea bed is too rocky, but also because, in sub-sea environments, it can be difficult to position the anchor on the sea bed with a high degree of precision. Alternatively, where the invention is used to access a flowline part-way along its length, the apparatus may need to be offset from the length of the flowline so as to not interfere with the path of the flowline.

Also, a rotational misalignment can arise between the curved guide and the launcher (i.e. where the central axis through the exit end of the curved guide is at an angle to the central axis through the channel extending through the launcher) when the adaptor is attached to the anchor.

To accommodate for a separation, the transition element may have an adjustable length. It may, for example, comprise an extendable section. To accommodate for vertical, fateral or rotational misalignment, the transition element can include at least a portion that is generally rigid but which is resilient so as to allow flexing along the length thereof. A longer resilient portion can accommodate a greater misalignment, and so preferably the resilient portion extends substantially along the full length of the transition element. In this way, a misalignment can be accommodated without the use of sharp bends in the transition element, permitting coiled tubing to move along the transition element in a relatively smooth path. It is useful to avoid sharp bends in the transition element so as to reduce friction between the coiled tubing and the transition element.

Where the resilience of the transition element does not permit a sufficient degree of flexing to accommodate the misalignment, the transition element may comprise an adjustable section which allows the exit end of the transition element to be freely adjusted with respect to the exit end of the curved guide of the adaptor. The adjustable section may be made of a flexible material, for example it could be a section of flexible pipe. Alternatively, a flex joint may be included at one or both of the entrance end or the exit end of the transition element so as to allow the orientation of the transition element to be varied. The flex joint could be of the type commonly used in traditional marine riser systems above the lower marine riser package. For example, it may comprise a swivel joint or a universal joint. The MisAHgning Flange (MAF), available from Oil States International, Inc. could be used.

In this way, the transition element can bridge the gap between an adaptor and a launcher irrespective of their relative positions.

In an alternative embodiment, the transition element can be purpose built for a given intervention activity. The purpose built transition element is therefore designed to accommodate the separation and vertical, lateral and rotational misalignment between the anchor and the launcher.

Additionally, the exit end of the transition element may be provided with a funnel for guiding the exit end into engagement with the launcher in use.

The transition element may be part of the adaptor, for example it may be an extension to the curved guide. However, it is preferred that the transition element is releasably couplable to the adaptor.

Advantageously, the distance between the first and second ends of the adaptor may be adjustable so as to vary the height of the curved guide. For example, the adaptor body can comprise two parts and adjustment means for adjusting the relative positions of the two parts. The adjustment means may include one or more spacers which can be positioned between the two parts of the adaptor body to separate the two parts. In another example, the adjustment means can include threaded portions on the two parts of the adaptor body which are engagable to allow relative rotation of the two parts which causes an increase or decrease in the distance between the first and second ends of the adaptor.

By adjusting the distance between the first and second ends of the adaptor, the adaptor can accommodate certain vertical misalignments between the exit end of the curved guide and the flowline/launcher.

The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a cross-section of a first embodiment of the invention in use with a riser system and flowline termination assembly; Figure 2 is a perspective of an anchor for use with the invention; Figure 3 is a perspective of an adaptor of the invention;

Figure 4 is a cross-section through the first end of the adaptor of Figure 3;

Figure 5 shows a transition element of the invention;

Figure 6 is a cross-section through an extendable section of the transition element of Figure

5;

Figure 7 is a perspective of a launcher of the invention;

Figure 8 is a cross-section through the launcher of Figure 7;

Figure 9 is a cross-section through an adaptor according to a second embodiment of the invention;

Figure 10 is a cross-section through an adaptor according to a third embodiment of the invention.

Figure 1 shows the apparatus of the present invention in use with a typical completion work over (CWO) riser system (1) so as to enable coiled tubing (6) to be inserted into a flowline (3) via a conventional flowline termination assembly (FTA) (2). The CWO riser system (1) can be deployed from a mobile offshore drilling unit (MODU) (not shown). The apparatus of the invention comprises an adaptor (10) to which the CWO riser system (1) is connected, a curved guide (16), a transition element (30) and a launcher (60). The adaptor (10) is secured to the sea bed (4) by way of an anchor in the form of a riser caisson (7) which, as mentioned above, can be viewed as a short, wide pile. The launcher (60) is connected to the FTA (2) using a flowline connector (5). Suitable flowline connectors are well known in the art, as is the way in which they are connected to the FTA (2). For example, the STABCON product from FMC Technologies could be used.

Using this arrangement, coiled tubing (6) can be deployed from the MODU using deployment equipment and techniques well known in the art. The coiled tubing can be passed down the CWO riser (72), into the adaptor (10) so that it is redirected from a substantially vertical orientation to a substantially horizontal orientation, through the transition element (30) and into the launcher (60). A pipeline intervention tool (66; see Fig. 8)) such as the coiled tubing pulling device disclosed in WO 03/067016, is pre-loaded into the launcher (60) so that the coiled tubing (6) can be connected to the tool (66) in the launcher (60). The coiled tubing (6) and tool (66) can then be moved downstream together into the flowline (3) via the FTA (2).

It can be seen that invention enables coiled tubing to be inserted into a flowline using equipment and techniques largely already available in the art.

The individual components will be described in more detail with reference to Figures 2 to 9.

Figure 2 shows the caisson (7) in more detail. At its first (upper) end (8), it comprises coupling means for releasably coupling to complementary coupling means provided on the adaptor (10). In this embodiment, the coupling means are in the form of annular grooves (9) around the exterior of the first end of the caisson, which can be engaged by hydraulically or mechanically operated dogs provided on the adaptor (a "dog" being a device that prevents movement of another object). The caisson is generally cylindrical in shape, though it may have a smaller diameter at its first end than at its opposing second end if a wider second end is required for additional stability. The caisson is typically made from steel.

The caisson is secured to the sea bed (4) by suitable means known in the art, for example by cementing the caisson (7) into a bore in the sea bed. As shown in Figure 1 , the first (upper) end (8) of the caisson protrudes above the sea bed after the caisson has been secured thereto.

When the adaptor (10) is coupled to the caisson (7), the caisson supports the adaptor against lateral, vertical and bending forces acting on the adaptor. Such forces result from the motion of the sea acting directly on the adaptor (10), but more significantly from the riser's (72) motion caused by movement of the sea and movement of the MODU from which the riser is deployed.

Figures 3 and 4 show the adaptor (10) in more detail. The adaptor has a generally cylindrical adaptor body (11) and a curved guide (16). The adaptor body (11) has a first end (12), which is the upper end in use, and a second end (13), which is the lower end in use. The first end (12) comprises first coupling means for releasably coupling the adaptor (10) to the riser system (1), and also has an opening (14) to allow coiled tubing to pass into the adaptor. The second end (13) comprises second coupling means (see Figure 9) for releasably coupling the adaptor (10) to the caisson (7). The first coupling means includes a hub profile to which a riser connector connects in the manner widely used to connect risers to Christmas trees. More specifically, a lower riser package (71) attached at the lower end of the riser (72) is provided with a plurality of hydraulically operated dogs which can be controlled to engage the hub profile at the first end (12) of the adaptor (10). The hub profile comprises an annular groove (15) with an angled load shoulder to mate with the dogs of the lower riser package.

The second coupling means also includes a plurality of hydraulically or mechanically operated dogs (see Figure 9) which can engage annular grooves (9) on the first (upper) end (8) of the caisson (7).

The curved guide (16) of the adaptor has an entrance end (17) facing the opening (14) in the first end (12) of the adaptor (10). In this example, the entrance end (17) of the curved guide (16) has a flange (18) which can be secured to the first end (12) of the adaptor using studs and nuts (19). A gasket (20) provides a seal between the first end (12) and the flange (18). The curved guide (16) also has an exit end (21). The entrance (17) and exit (21) ends of the curved guide (16) are connected by an arcuate conduit which curves along at least a portion of its length and which allows the passage of coiled tubing there-through. The arcuate conduit is shaped so as to be capable of guiding coiled tubing from a substantially vertical orientation upstream of the adaptor to a substantially horizontal orientation downstream of the adaptor (10). Accordingly, the central axis through the entrance end (17) of the curved guide (16) is substantially perpendicular to the central axis through the exit end (21) of the curved guide. An opening (22) in the adaptor body (11) allows the curved guide (16) to pass through the adaptor body.

The entrance end (17) of the curved guide (16) is in alignment with the opening (14) through the first end (12) of the adaptor (10) to allow the curved guide to be in communication with the opening (14). In this case, the curved guide is in sealed communication with the opening (14).

At the exit end (21) of the curved guide (16), there is a clamp assembly (23) comprising clamp elements which can be operated by a remotely operated vehicle (ROV) so as to clamp the exit end of the curved guide to the transition element (30). A guide funnel (24) provides a means of aligning the curved guide (16) with the transition element (30). A sealing profile and gasket can be provided to ensure a seal between the curved guide and the transition element.

The radius of curvature of the curved guide is as large as possible so that the coiled tubing is redirected very gently as it passes through the curved guide. In this example, the radius of curvature is about 25 times the outer diameter of the curved guide. For a typical curved guide outer diameter of 8 ^S Λ" (21.9cm), the radius of curvature can be about 215" (546cm).

Figures 5 and 6 (not to scale) show the transition element (30) in more detail. The transition element has a generally tubular shape having a conduit (31) extending therethrough. A hub (32) at one end facilitates connection to the curved guide (16) of the adaptor (10) and a clamp and guide funnel (33), similar to those provided at the exit end (21) of the curved guide (16) of the adaptor (10), are provided at the other end of the transition element (30) for joining the transition element to the launcher (60).

The transition element (30) includes a telescopic joint assembly (36), shown in detail in Figure 6, which allows the transition element (30) to vary its length to allow ease of connection between the exit end (21) of the curved guide (10) and the launcher (60). The telescopic joint assembly (36) comprises a piston (37) connected to a sliding end (38) of the transition element. The piston (37) is located within a cylinder (39). An end stop (40) connected to the cylinder (39), via a thread (41), controls the limit of travel of the piston (37) in the extended position. The cylinder (39) is attached to a transition end stop (42), via a thread (43) that controls the limit of travel of the piston in the retracted position. The transition end stop (42) is connected to the fixed end (44) of the transition element. Seals (45,46) on the end stops (40,42) provide pressure containment for the hydraulic fluid within the chamber (47). Wiper seals (48) centralise the sliding end (38) within the transition end stop (42) and provide a cleaning action on the sealing bore (49) (of the transition end stop (42). The piston (37) has dynamic seals (50) that provide a seal between the piston (37) and the bore of the cylinder (39). An ROV is used to feed fluid to or receive fluid from the chamber (47) in order to extend or retract the sliding end (38) of the transition element. The fluid is fed to the chamber (47) via a hot stab (51) (which is essentially a fluid connector for the ROV) and via an extend port (52) and retract port (53) on the transition element (30).

The retracted (i.e. minimum) length of the transition element can be several meters or tens of meters long, and extending the transition element can increase the length by tens of centimetres or even several meters. The transition element is typically made from a strong material that is relatively rigid, but which, in the form of a long cylinder as in the transition element, has some resilience, such as low alloy steel or other similar materials. In this way, the long length of the transition element and the construction of the transition element, allows some bending of the transition element to occur. This enables some vertical, lateral and rotational misalignments between the exit end of the curved guide and the launcher to be accommodated.

Figures 7 and 8 show the launcher (60) in more detail. The launcher is generally tubular in shape and comprises a body (61), a rear hub (62), a front flange (63) and two pairs of tool stop assemblies (64). The rear hub (62) can be connected to the transition element (30) by way of the clamp (33) on the downstream end of the transition element (30). The front flange (63) has a sealing face (65) to match the flowline connector (5).

A generally cylindrical conduit (67) extends through the launcher and can house a pipeline intervention tool (66) such as the coiled tubing pulling device disclosed in WO 03/067016. The tool (66) is pre-loaded into the launcher at the surface before the launcher is positioned sub-sea. The tool (66) is held against the pairs of tool stop assemblies (64) which can be mechanically or hydraulically released by an ROV.

The intervention tool (66) is provided with coupling means (68) at its upstream end to engage coupling means on the downstream end of the coiled tubing so that the coiled tubing and tool (66) can be connected in the launcher (60). The coupling means (68) can take the form of a latch mechanism or the like.

The apparatus of the present invention can be used to enable coiled tubing (6) to be inserted into a flowline (3), for instance in case the flowline is blocked. As mentioned elsewhere, the flowline entry point may be at an FTA (2) at the end of the flowline (3), or part- way along the flowline at a flowline 'T' or at an apparatus as described in co-pending US serial number 12/081574. Typically, in normal operation, one end of a FTA (2) is connected to the flowline (3) and the other end is often linked via a short spool piece to a sub sea manifold or other such sub sea hardware. In order to gain mechanical access to the flowline, the spool piece must first be removed. The apparatus of the present invention can then be used to direct coiled tubing into the flowline.

Where the access point is at an FTA (2), the sea bed (4) adjacent the FTA is inspected to identify a suitable location for a caisson (7). A location which lies on the axis through the flowline end is desirable, though some misalignment may be encountered if the sea bed surface prevents locating the caisson on the flowline's axis. The caisson (7) is set into the sea bed, for example using concrete, such that its upper end (8) protrudes above the sea bed (4).

The pipeline intervention tool (66) is loaded into the launcher (60) at surface, and the flowline connector (5) is connected to the exit end of the launcher. The assembly is then lowered to the sea bed and connected to the FTA (2) using the flowline connector (5).

At surface, the adaptor (10) is connected to the CWO riser (72) using well known connectors used commonly to connect risers to Christmas trees. Specifically, an emergency disconnect package (EDP) (70) is connected to a lower riser package (LRP) (71), and the adaptor (10) is connected to the underside of the LRP (71). The CWO riser (72) can then be connected to the top of the EDP (70). A surface flow tree (SFT) (90), which is an assembly that comprises one or more valves to control fluids in/out of the riser, is connected to the top of the riser (72). The riser, EDP, LRP and adaptor are then deployed subsea.

The adaptor (10) is orientated subsea so that the exit end (21) of the curved guide (16) aligns as much as possible with the launcher (60) and the adaptor is then landed out on the caisson. The second coupling means on the adaptor are then operated to lock the adaptor to the caisson.

The transition element (30) can then be deployed sub sea and positioned such that the hub (32) of the entrance end of the transition element is positioned within the open clamp (24) on the exit end (21) of the curved guide (16). The clamp (24) is operated by an ROV, for example by using a torque tool to engage a torque bucket of the clamp (24), thereby locking the hub (32) to the adaptor (10).

The ROV would then connect the hot stab (51) to the extend (52) and retract (53) ports on the transition element (30) so as to put the ROV and the chamber (47) of the transition element (30) into fluid communication. The ROV can apply pressurised fluid to extend the sliding end (38) of the transition element until the funnel of the clamp and funnel arrangement (33) is engaged over the launcher rear hub (62).

The flared shape of the funnel (33) means that, even if the exit of the transition element and the launcher are misaligned, the launcher can still be captured by the width of the funnel. As the transition element extends towards the launcher, the inner surface of the funnel (33) acts as a cam surface so as to guide the exit of the transition element into engagement with the launcher. In this way, the funnel allows the transition element to be self-centring. This process can cause some flexing of the transition element to accommodate the misalignment. The clamp of the clamp and funnel arrangement (33) is then operated by ROV torque tool to lock the transition element to the launcher.

An external pressure test can then be conducted to verify the sealing integrity of the connections. An external pressure test port, for example on the adaptor or transition element, can be used by an ROV in such testing.

The system is now ready for coiled tubing deployment. The equipment and technique to deploy the coiled tubing (6) into the riser (72) are well known, and so will be described only briefly here. A coiled tubing stripper (91) or lubricator is connected to the top of the SFT (90). Coiled tubing (6) is deployed through the riser (72) and into the adaptor (10). The coiled tubing (6) can then be advanced through the transition element (30) and into the launcher (60). At this point, the seawater in the riser (72) and other pieces of equipment can be flushed out to methanol by pumping methanol down the coiled tubing bore and taking seawater returns up the annulus between the coiled tubing and the riser. The coiled tubing would then engage the pipeline intervention tool (66) in the launcher.

The tool stop assemblies (64) of the launcher are opened by an ROV by inserting a torque tool into the torque tool bucket and operating the tool to open the stops (64) thereby providing unrestricted access to the FTA (2). Alternatively, the tool stop assemblies are opened hydraulically by the ROV.

Where the pipeline intervention tool (66) is the coiled tubing pulling device described in WO 03/067016, a fluid can be applied via an inlet in the SFT to act as thruster drive fluid, thereby pressurising the annulus between the outside of the coiled tubing and the riser bore. The fluid acts on the sealing cups of the CT pulling device thereby causing the pulling device to be driven into the flowline (3) via the FTA.

As the coiled tubing advances into the flowline, displaced fluid in front of the CT pulling device is directed back through the coiled tubing bore and back to the MODU (or other vessel/platform from which the riser is deployed). Once the coiled tubing has reached the flowline blockage, such as a hydrate plug, pressurised fluid or chemicals can be pumped down the riser annulus and out via the thruster nozzles to help disassociate the plug. As the plug disassociates, the coiled tubing is moved further into the flowline and the jetting continues. Eventually the plug will be removed and the CT pulling device and coiled tubing can be recovered using the coiled tubing injector in reverse to pull the coiled tubing out of the flowline. The coiled tubing pulling device (66) is retrieved into the launcher (60) until it contacts the rearmost tool stop assembly (64). The coiled tubing is then disconnected from the CT pulling device.

The contents of the riser (72) can be flushed to seawater by pumping seawater down the coiled tubing bore to displace any chemicals and remaining hydrocarbon out of the riser. Following flushing, the coiled tubing (6) is then recovered back through the riser (72) and out through the SFT.

After use, the apparatus of the invention can be left on the sea bed or can be removed to surface.

Figures 9 and 10 show further embodiments of the adaptor of the invention. Where features of the adaptors shown in Figures 9 and 10 are the same as those of the adaptor shown in Figures 3 and 4, like reference numerals are used. In Figure 9, a spacer (80) is positioned between the hub at the first end (12) and the adaptor body (11). In this way, the height of the curved guide (16) can be adjusted with respect to the second end (13) by inserting a spacer. The opening (22) through the adaptor body (11), through which the curved guide (16) extends, is elongate to allow for this vertical adjustment.

Figure 9 also shows hydraulically operated dogs (81) on the inner surface of the second end of the adaptor for engaging grooves (9) on the caisson (7). These dogs are the same as those described above with respect to Figures 3 and 4.

In Figure 10, the adaptor body (11) is formed in two parts; a fixed part (82) and a moveable part (83). The fixed part (82) is the part which connects adjacent the caisson (7), whereas the moveable part (83) is adapted to move with respect to the fixed part (82) so as to adjust the separation between the first (12) and second (13) ends of the adaptor. This movement is achieved using threads (88) on the inner surface of the fixed part which can engage threads (87) on the outer surface of the moveable part. Relative rotation of the two parts causes the separation between the first and second ends of the adaptor to be adjusted.

The adaptor shown in Figure 10 can be assembled for a particular curved guide height as follows. The moveable part (83) is first brought together with the fixed part (82) and the two are screwed together using the threads (87,88) until the desired separation between the first (12) and second (13) ends is obtained. Bolts (84) extend through bores in a flange (86) on the moveable part (83) and a flange (85) on the fixed part (82) to lock the relative positions of the moveable part (83) and the fixed part (82). The entrance end (17) of the curved guide (16.) is fed through the opening (22) in the side wall (11) and is then attached to the first end (13) of the adaptor by bolts (19). The first end (12), with the curved guide attached, can then be fixed to the moveable part (83) by bolts (89).

Should subsequent adjustment of the relative positions of the moveable (83) and fixed (82) parts be required, the bolts (84) connecting the moveable part to the fixed part and the bolts (89) connecting the first end (12) and the moveable part (83) are removed so that the moveable part (83) can be screwed or unscrewed as necessary with respect to the fixed part. Reassembly of the fixed part, moveable part and first end as described above then follows.

The adaptors of Figures 9 and 10 enable the vertical position of the exit end (21) of the curved guide (16) to be adjusted as required for a particular situation, specifically where there would otherwise be a vertical misalignment between the exit end of the curved guide and the launcher.