GB2457081A - Launching a pig through a subsea christmas tree - Google Patents

Abstract

A system for launching pigs 6 into a pipeline 50 utilises a pigging spool 1 connected to a subsea Xmas Tree 9. The Xmas Tree mounted pig spool 1 may be used with a Completion Workover riser system, consisting of a coil tubing spool 17, a stress joint 25, riser joints 26, a tension joint 27, a swivel 28, a surface flowhead 29, a tension frame 30 and a coil tubing head 31, to allow a thruster pig or pipeline tractor to be deployed on coil tubing, thereby providing a hydrate remediation capability to allow pipeline blockage remediation. A pig launcher tube (57, figures 10-13) may be joined to the pigging spool 1 to supply pigs 6 to the system. The Xmas Tree mounted pig spool 1 can preferably utilise Xmas Tree production, injection or gas lift fluids 73 to drive the pigs 6 into the pipeline 50. Alternatively, the driving fluid may be supplied from the surface (see figure 1).

Description

Subsea Pigging and Hydrate Remediation System (SPAHRS)

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to subsea pig launching and hydrate remediation of pipelines. More particularly the present invention provides a method and apparatus for connecting a pigging and hydrate remediation system to a subsea Xmas Tree utilising the XT production, injection or gas lift fluid to drive the pig and coil tubing into the pipeline.

BACKGROUND OF THE INVENTION

In the subsea oil and gas industry it is common to remove wax scale and other such deposits from the bore of a pipeline by pushing a cleaning device referred to as a pig through the lines using fluid pressure.

In sonic instances pipelines can become blocked or partially blocked by wax and hydrates that use of conventional pigs is limited. Deploying a conventional pig down a pipeline in such instances can result in total blockage of the line, a stuck pig or both.

In emerging technologies, wax and hydrate removal can bc achieved by providing a return path for the displaced fluid thereby mininhising the risk of getting a stuck pig in the hole. The pig is deployed down the pipeline using coil tubing attached to the pig with the returns taken through the coil tubing back to surface The annular area between the flowline and the coil tubing is used to drive the pig through the pipeline. Chemicals such as mono-ethylene-glycol (MEG) can be used to help break up the hydrates and can be injected ahead of the pig using suitable ports in the pig. These types of pigs are known as thruster or pulling pigs. The pig is introduced into thc pipeline from a launching system attached to the pipeline. The coil tubing can, as an alternative, be deployed into the pipeline using a subsca tractor device with returns taken through the tractor and the coil tubing! riser annulus, Such pigging systems require the use of coil tubing to provide a conduit. The coil tubing is supplied on a reel and is usually situated on the platform, Mobile Offshore Drilling Unit (MODU) or driliship deck. The traditional means of introducing the coil tubing is through a workover riser with the lower end of the riser connected to the seabed and the top end connected to the MODIJ thereby. A coil tubing injector head is required to allow the tubing to be relayed through the riser.

SUMMARY OF Ti-JE INVENTiON

The present invention provides the apparatus for launching pigs subsea by utilising a pigging spool attached to the top of a subsea Xmas Tree. The pigging spool could also be used to allow the deployment of either a pulling pig or subsea tractor for the deployment of coil tubing into the pipeline and subsequent pigging operations.

Production pipelines and flowlines usually have a much greater diameter than that of a single Xmas Tree therefore a large bore pigging riser would he required to deploy the thruster pig or subsea tractor. Use of a full bore riser would be expensive, cumbersome and could be impractical due to the higher environmental loads associated with such systems.

The following system allows a standard completion workover (CWO) riser system (typically 5" bore) to be used Such CWO systems are traditionally used during interventions on subsea Xmas Trees.

Use of a CWO riser system is achieved hytlie use of a thruster pig-tractor spool (TPI'S) that connects directly to the top of a subsea Xmas Tree. The TPTS, with the thruster pig or tractor pre-installed in the bore of the spool, is attached to the bottom of the CWO riser and the complete assembly deployed subsea and the TPTS locked to the top of the Xmas Tree.

The XT and welihead provides a stable platfbi-m to withstand the external loads acting on the riser and to help resist nser tension. The XT and welihead also provide adequate support to resist any drift off and drive off loadings associated with non-anchored MODU's. The coil tubing is then deployed within the CWO riser and latches to the thruster pig or subsea tractor A coil tubing device such as a shear valve or ram is required at the bottom of the riser system to allow shearing of the coil tubing in event that the riser has to be disconnected due to extreme weather conditions or vessel drift off or drive off.

Another feature of the concept is the utilisation of the Xmas Tree to supply the pressurised fluid required to drive the thruster pig into the pipeline. For Injection Xmas Trees it is nomaI to inject fluids from the FPSO or Platform into the XT and downhole into the reservoir to boost production. Instead of injecting the fluid downhole the injected fluid through the XT could be diverted such that it was directed into the TPTS spool behind the pig and used to drive the pig through the pipeline thereby dispensing with a need to pump fluid from the MODU.

Use of a Xmas tree to support the TPTS also prevents the need to provide a separate seabed structure to support the TPTS and surface riser. Installation and equipment savings could therefore be achieved by attaching the TPTS direct to the Xmas Tree.

The TPTS could also be used to allow the subsequent connection of a pig launcher tube thereby providing a means of launching single or multiple cleaning, gauging or inspection pigs from the TPTS attached to the lop of the Xmas Tree. The riser would he removed and the pig launcher tube installed directly onto the TPTS. The CWO riser could then be connected direct onto an adjacent Xmas Tree to allow intervention work to he perfomied on an adjacent well, without the need to recover the nser to surFace, if need he, whilst pigging operations are concurrently being conducted on the pipeline.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the system components as they would be ready for thruster pig launching operations; Figure 2a shows the TPTS in more detail; Figure 2b shows the TPTS pig stop arrangement; Figure 3 shows the shear spool; Figure 4 shows the riser system with an EDP and LRP attached to the TPTS; Figure 5a shows a thruster pig or tractor profile for accepting the coil tubing; Figure Sb shows the coil tubing adapter; Figure Sc shows the coil tubing adapter attached to the coil tubing; Figure 5d shows the coil tubing adapter attached to the thruster pig or tractor; Figure 6 shows the pig in the pipeline and the pipe blockage; Figure 7 shows a method for releasing the coil tubing from the pig; Figure 8 shows the pig retrieved against an end stop; Figure 9 shows the TPTS with the shear-pig spool attached, Figure 10 shows a cleaning, gauging, inspection pig launcher system; Figure 11 shows a pig launcher tube; Figure I 2 shows a pig launcher system driven by the Xmas Ti-ce injection fluid; Figure I 3 shows a pig launcher system driven by the Xmas Tree production fluid; Figure 14a shows the TPTS system driven by the Xmas Tree injection fluid; Figure 14b shows a pail iew of a TPTS system driven by the Xmas Tree production fluid; Figure 15 shows a combined pig and shear ram spool; Figure 1 6 shows the combined pig and shear ram system.

DETAILED DESCRIPTION OF TI-FE PREFERRED EMBODIMENTS

Referring to figure I. The system comprises a pigging spool 1 connected to a Xmas Tree 9 which in turn is connected to a subsea wcllhead 48. A coinpietion workover riser system consisting ofa coil tubing spool 17, a stress joint 25, riser joints 26, a tension joint 27, a swivel 28, a surface flowhead 29, a tension frame 30 a coil tubing head 31 are all connected to form a riser system. The shear spool 1 7 is connected to the top of the Thruster Pig Tractor Spool (TPTS) I and a coil tubing reel 32 supplies coil tubing 37 into the bore of the riser via a coil tubing head 3 1. A thruster pig or tractor, herein simply referred to as the pig 6, is contained within the TPTS I and held in place within the TPTS 1 by a pig stop 4. The complete TPTS and nser assembly comprising TPTS I, pig 6, shear spool 17, stress joint 25, riser joints 26, terisionjoiiit 27, swivel 28 and flowhead 29 is landed and locked on an existing XT 9 aiid subsea wellhead 48. The riser system is kept in tension using ruckers 49 attached to the tension joint 27 at one end and the surface facility 50 at the other. Additional tensioning or split tension sharing can be achieved by utilising the tension frame or hails 30 attached to the flowhead 29 thereby keeping the complete riser string in tension The coil tubing head 31 is then connected to the toj) of the Ilowhead 29 and coil tubing 37 spooled into the iser 25, 26, 27 via the flowhead 29.

The coil tubing 37 continues to be spooled until the coil tubing 37 is connected to the pig 6. A spool piece 10 connects the pig spool I to the manilbld or pipeline 36 via connection points 33 and 34 thereby pi-oviding a conduit from surface to the pig 6.

Figure 2a shows the TPTS 1 in more detail. The TPTS I comprises a connector body 7a and connector lock mechanism 7h at the lower end, a main body 2, a radiused spool 3, a pig stop 4 and a connector hub 5 at its UCF cnd. The pig 6 is installed in the main body 2, pig stops 4 locale the pig 6 within the main body 2. The connector 7a has a set of dogs 7b that can be mechanically or hydraulically operated to latch the connector 7a to the top of the XT 9. The spool 3 can either be integrally connected to the main body 2 or be separate from the main body 2 The spool 3 has a mating hub, flange or connector 8 to allow connection to the conduit 10. The pig stop 4 is shown in more detail in Figure 2b and comprises a threaded rod 12, a shaft 13, seals 14 and a drive mechanism 15. Rotation of the mechanism 15 causes the threaded rod 12 to rotate within the threaded profile 16 in the body 2 thereby causing the pig stop 4 to translate relative to the body 2. Rotation in one direction causes the pig stop 4 to extend thereby providing unrestricted access to the pig spool bore 11, rotation of the drive 1 5 in the opposite direction causes the pig stop 4 to retract thereby preventing passage of the pig 6 through the bore II. The pig stop 4 could be operated by other means such as hydraulic without departing from the spirit of this invention.

Figure 3 shows a coil tubing spool 17 comprising an emergency disconnect connector 18, a coil tubing shear i-airi 19, an adapter spool 20, an upper huh 21 with seal profile 22. The adapter spool upper hub 21 and seal profile 22 can be profiled to suit any proprietary lower stress joint interface. The connector 18 comprises a set of dogs 23 and a seal 24 to provide a means of locking and sealing to the top of the TPTS 1.

The CWO nsei-is shown in Figure 1 and comprises, a lower stress joint 25, riser joints 26, a tension joint 27, a swivel 28, a tlowhcad 29, a tension frame 30, a coil tubing unit 3 land a coil tubing reel 32 as traditionally used when conducting interventions or workovei-s on Xmas Trees. A landing string typical of that used for interventions on Horizontal Xmas trees could also be used in lieu of the CWO riser shown without departing from the nature of the invention. The riser system could equally well operate using a proprietary EDP 80 and LRP 8 1 as shown iii Figure 4 also typically used on CWO systems without impacting the invention.

Referring to Figure 1, the pig 6 is shown pre-installed in the TPTS body 2. The lower stiess Joint 25 would then be deployed through the rotary table on the MODU and connected to the top of the shear spool 17. The pig TPTS body 2 would then be deployed subsea using the appropriate number of riser joints 26. The tension joint 27, Swivel 28 and flowbead 29 would then be connected to the last riser joint 26. The XT Tree Cal) would then be removed fi-orn the lop of the Xmas Tree 9 in preparation for landing out the TPTS I and riser assembly directly onto the XI 9. The complete riser assembly would then be lowered the last few metres to allow connection of the TPTS I to the top of the Xmas Tree 9.

A length of conduit 10 with mating connection 33 would then be connected to the TPTS connection point 8 with the other end of the conduit 10 with mating connection 34 connected to the mating flange 35 on the manifold 36. For shallow water applications it is envisaged that the end connection 34 of the conduit 10 would be a bolted flange or clamp hub connection. For deepwater applications the conduit connection point 34 could be fitted with any proprietary deepwater remote connection system. Any suitable means of connecting the conduit 10 to the TPTS I and Pipeline 50 could be used without departing from the spirit of this invention.

The coil tubing head 31 would then be made up to the flowhead 29 and the coil tubing 37 spooled from the reeler 32 and into the riser 26 via the flowhead 29. The coil tubing 37 would be deployed through the shear spool I 7 and into the pig thruster spool 2 and automatically latch into the pig 6 Figure 5a shows the pig with a suitable profile to allow the coil tubing to be connected, the profile comprises a landing shoulder 43, a seal surface 44, a coil tubing adapter locking profile 45, a centralising profile 46 and a lead in profile 47.

Figure 5b shows a coil tubing adapter 38. Figure 5c shows the adapter 3S attached to the coil tubing 37. The coil tubing adapter 38 comprises a centralising hub 39, a coil tubing stub 41 for connection to the coil tubing 37, a locking device 40 such as but not necessarily limited to a snap ring or spring loaded dogs and a seal 42 to seal the adapter 38 to the pig 6.

Figure Sd shows the coil tubing adaptcr 38 connected to the pig 6 with the coil tubing adapter locking device 40 engaged in the mating recess 45 of the pig 6 and the seal 42 sealing to the seal profile 44. The pig 6 has seals 54 that seals to the pig spool 1, conduit and the pipeline 50.

Figure 2b shows the pig stop arrangement 4 that comprises; a threaded rod 12, a drive mechanism 15 and seals 14. Following connection of the coil tubing 37 to the pig 6 the pig stops 4 would be operated by rotating the drive mechanisni I 5 thereby causing the threaded rod 12 to traverse outwards. The operation would be repeated on the opposite pig stop 4 thereby providing unrestricted access for the thruster pig 6 to pass through the bore of the TPTS 1.

Referring to Figures 1 and 5d, the pig 6 is forced through the TPTS I and into the conduit 52 then into the manifold 36 and subsequently into the pipeline 50 by introducing pressurised fluid 51 via the surface flowhead 29 and down the annulus 52 between the riser bore and the coil tubing outer diameter. The force developed across the annular area of the pig develops the force require to push the pig 6 and the coil tubing 37 into the pipeline 50.

Figure 6 shows the 6 pig in the pipeline 50, fluid returns from the pig 6 flow through the middle of the pig 53 and back through the coil tubing 37 and back to surface and out of the coil tubing reeler 32 for processing on the MODU or driliship. The pressurised fluid 51 may contain chemicals to help melt' the hydrate or breakdown the wax or scale deposits causing the blockage 49 in the pipeline 50 Once the blockage 49 has been cleared the pig 6 can continue to he pushed down the pipeline 50 and received at a pigging receiver if required Figure 7 shows a method of disconnecting the coil tubing 37 from the pig 6 by dropping a ball 55 into the coil tubing 37 and then pushed down the bore of the coil tubing 37 and into the upper profile of the pig 6. Applying pressure 56 down the bore of the coil tubing 37 behind the ball 55 generates a load to shear out the locking mechanism 40 to separate the coil tubing 37 from the pig 6.

Figure 8 shows an embodinient of' the system showing an alternative means of disconnecting the coil tubing 37 from the pig 6. Referring to Figures 1, 7 and 8, following removal of the blockage 49 from the pipeline 50 the pig 6 is pulled back into the TPTS I against the closed pig stops 4, applying an overpull on the coil tubing 37 shears out the lock mechanism 40 thereby separating the coil tubing 37 from the pig 6, alternatively a ball 55 can be dropped down the coil tubing 37 and pressure applied behind the ball 5510 shear out the locking mechanism 40 thereby separating the coil tubing 37 from thc pig 6.

The coil tubing 37 is then recovered to surface with the pig 6 remaining within the TPTS The coil tubing 37 would then be retrieved to above the shear ram 19 and the shear rams 19 closed. Clean fluid could then be pumped down the coil tubing 37 to circulate out any riser fluids that could not be expelled to sea. Once flushing of the riser was complete then the coil tubing 37 would then be retrieved through the riser 26. The conduit 10 would then be disconnected and the riser 26 complete with shear ram spool 1 7 and the TPTS I retrieved to surface.

Figure 9 shows an embodiment of the system whereby the pig 6 is stopped within the shear spool I 7a rather than in the pigging spool I a. This allows the pig 6 to be retrieved with the riser 26 leaving the pigging spool I a in place. The modified arrangement of the shear spool I 7a, herein referred to as the pig shear spool, is shown in Figure 9 and comprises; a connector body 1 8a, a connector locking arrangement I 8b, a seal element 24, a spool body 20a, a pair of shear rams 19, an upper hub 2 I, a seal surface 22 and a pig stop arrangement 4 and 4a. The pig 6 would be pushed through the pipeline 50 as previously described. Once the blockage 49 had been cleared then the pig 6 could be retrieved back into the pig shear spool I 7a. The upper pig stops 4a would have previously been closed with the lower pig stops 4 open such that the pig 6 would be positioned within the spool I 7a against the upper pig stops 4a. The lower pig stops 4 would then be closed thereby trapping the pig 6 within the spool 17a. The coil tubing 37 could then be disconnected from the pig 6 by an overpull or dropping a ball down the coil tubing bore as previously described. The riser contents could then be circulated out if required as previously described The pig shear spool I 7a would then he disconnected from the pig spool I a and the pig shear spool I 7a retrieved with the riser 26.

Figure 10 shows a pig launcher tube 57 with prc-loadecl cleaning, gauging or inspection pigs, herein referred to simply as disc pigs, 64 deployed on top of the pig spool Ia thereby allowing the disc pigs 64 to be deployed as required without the need to disconnect the spool 1 0 from the manifold 36 or pipeline 50. The arrangement showing the pig launcher tube 57 is shown in figure 11 and comprises; a connector body 58, a locking dog 59, a lower tube 60, an upper tube 61, an end closure 62, a lifting point 63 and a hydraulic connection point or points 65. Referring to Figures 10 and II, a down-line 66 from a surface vessel 67 is connected to the pig launcher hydraulic connection 65.

Disc pigs 64 are shown pre-loaded into the pig tube 57 with each pig separated by a pig stop 4 as previously described. The lowermost disc pig 64 can be launched into the pipeline 50 via the pig spool I a, spool 3 and conduit 10 by supplying fluid pressure from the vessel 67 following opening of the lowermost pig stop 4. The hydraulic down line can then be connected disconnected by ROV 68 and re-positioned on the next hydraulic connection 65, the next disc pig 64 can then be launched into the pipeline as before. Once all the disc pigs 64 have been pushed through the pipeline 50 then the hydraulic down line 66 can be disconnected from the hydraulic connection 65 and the launcher tube connector dogs 59 unlocked from the Xmas Tree 9 and the launcher tube 57 recovered to surface via lift wire 69.

An enibodimcnt of (lie pig launcher system is shown in Figure 12 wherein the disc pigs 64 can be launched into the pipeline 50 without the need for a down line from a surlace vessel 67. The pig spool lb has a bore 70 linked to the XT bore 71. The lower end of the conduit 72 attached to the pig spool lb via a suitable connection point such as, but not necessarily limited to, a flange 79. The other end of the conduit 72 is connected to the pig launcher tube 57 via a hydraulic connection 65.

The system is shown in Figure 12 and comprises a Xmas Tree 9 attached to a wellhead 48, a pig launch tube 57 containing pre-installed disc pigs 64 is attached to the pig spool lb. The pig spool lb is connected to the top of the Xmas Tree 9, which in turn is connected to the wellhead 48. The method of connecting the pig launch tube 57 to the pig spool lb is as previously described.

Once the lower most pig stop 4 has been opened pressure is directed from the inject ion fluid or gas lift fluid inlet 73 via the XT choke 74, the XT wing valve 75 the Swab Valve 76 and into the pig spool Ib, along the fluid conduit 72 and into the pig spool 57 via the hydraulic connection 65 thereby forcing the disc pig 64 through the pig launcher tube 57, pig spool Ib, conduit 3 and into conduit 10 and into the pipeline 50. Once the disc pig 64 has been received at the pig receiver then the Swab Valve 76 is then closed and the fluid conduit 72 disconnected from the launcher tube 57 and connected to the next hydraulic connection point 65 to allow the second disc pig 64 to be launched. The Swab Valve 76 is then opened thereby directing the pressurised fluid behind the second disc pig 64 and forcing the disc pig 64 into the pipeline 50. The above process is then repeated until all the disc pigs 64 have been launched.

The Swab Valve 76 is then closed and the Master Valve 77 opened to allow the inlet fluid 73 to be directed into the injection well. The fluid conduit 72 is then disconnected from the launcher tube 57 and the launcher tube 57 disconnected &om the Xi 9 by operating the clamp 59 and retieving the launcher tube 57 via the lift point 69. The fluid conduit 10 would then be disconnected from the spool 3. A suitable retrieval tool would then be attached to the pig spool I b and the pig spool lb unlocked from the XT 9 and recovered to surface. The XT Tree Cap would then be installed back onto the Xmas Tree 9.

Figure 13 shows a further embodiment of the system wherein produced fluid from the Xi 9 is produced from the well past the open Master Valve 77 and open Swab \1alve 76 and into the pig launcher 57. The operation of launching the disc pigs 64 being as previously described.

Figures 14a and 14h shows Ilirthereinbodiments of the system shown in Figure 1 but wherein the thruster pig drive fluid is supplied from the Xmas Tree 9 thereby dispensing with the need to supply pig drive fluid from the MODU or driliship. Figure 14a shows the system arrangement for an injection XT thruster pig drive fluid supply with the method of driving the pig as previously described per the Figure 12 system. Figure l4b shows a Production Xi pig drivc fluid supply with the meihod of driving the thruster pig 6 as previously described pei the Figure 1 3 disc pig system.

Figure 15 shows a further embodiment of the system wherein the shear rams are incorporated into the thruster pig spool. This system would reduce the height of the equipment above the XT and thereby reduce the bending moment on the XT and wellhead and dispense with the need for a separate shear spool above the pig spool.

The combined shear-pig spooi is shown in Figure 15 and comprises a connector body 7a, locking dogs 7b, coil tubing shear device 19, a double set of pig stops 4 an upper hub 21 and seal prolile 22 and an outlet spool 3. The pig 6 is I)re-installed in the spool I 7h and held within the upper and lower pig stops 4.

The pig 6 would be retrieved until it contacted the upper closed pig stop 4 The lower pig stops 4 would then be closed thereby restraining the pig 6 from movement in either dii-ection. The coil tubing 37 would then be disconnected by dropping a haIl 55 down the coil tubing 37 and into the upper profile of the pg 6. Applying pressure within the coil tubing 37creates an end load to shear out the device 40 on the coil tubing adapter 38 thereby freeing the coil tubing 37 from the pig 6 with the lower pig stop 4 preventing the pig 6 from being pushed back down into the pipeline 50. A disconnect point would be required above the pig spool and Figure 16 shows the Lower Stress Joint 25 temlinating in a disconnect connector 78 at the bottom of the riser jon-it The overall system showing the pig-shear ram spool and disconnect connector is shown in Figure 16.

The riser would then be disconnected from the pig spool I 7h by unlocking the connector 7a by operating the locking device 7b leaving the pig spool 17b in place. Once the thruster pig 6 pigging operations were complete and the riser disconnected from the TPTS II a pig launcher tube 57, with pre-installed pigs 64 as shown in Figure 11 could then be installed onto the pig-shear spool I 7b thereby allowing cleaning, gauging and inspection pigs 64 to be deployed as required to complete the pigging programme without disturbing the connection between the pig-shear spool I 7b and the Manifold 36. A downline from surface would be required to provide pigging fluid to drive the cleaning gauging or inspection pigs through the pipeline or alternatively the pigs could be launched using the XT production, injection or gas lift fluid as previously described and illustrated in Figures 12 and 13.

Claims (10)

1. A method for launching a pig into a pipeline comprising a pig spool that connects to a subsea Xmas Tree.

2. A subsea pig launcher system according to Claim I, wherein the pigging spool can accept cleaning pigs, gauging pigs, inspection pigs, a thruster pig or a pipeline tractor within the pigging spool body.

3. A subsea pig launcher system according to Claim 1, wherein the pigging spool is connected to the manifold or pipeline via a fluid conduit.

4. A subsea pig launcher system according to Claim 1, wherein a riser can be attached to the pigging spool via a coil tubing shear spool.

5. A subsea pig launcher system according to Claim 1, wherein the pigging spooi incorporates a coil tubing shear ram or valve.

6. A subsea pig launcher system according to Claim I, wherein a separate coil tubing shear ram spool is attached to the pigging spool.

7. A subsea pig launcher system according to Claim 1, wherein the pigging spool incorporates a pig stop mechanism or mechanism.

8. A subsea pig launcher system according to Ci aim 1, wherein the pigging spool incorporates a conduit connecting the Xi production, injection or gas lift bore to an inlet on the pigging spool, with the inlet positioned above the rear of the pig such that the XT production or injection fluid can be used to drive the pig into the pipeline.

9. A subsea pig launcher system according to Claim I wherein a pig launcher tube with single or multiple pigs can be attached to the pigging spool.

10. A subsea pig launcher system according to Claim 9, wherein the pig drive fluid is supplied via the suhsea Xmas Ti-ce production, injection or gas lift bore.