The present invention relates to a method of and system for providing hydraulic and / or electrical connections to a tubing hanger installed on a wellhead.

During the drilling of a wellbore for oil and/or gas production or during the completion process for bringing the wellbore into production it is known to mount a tubing hanger on the wellhead. The tubing hanger is typically mounted in a production adapter base or tubing head spool which is mounted on the wellhead. The tubing hanger is provided to support the production tubing string.

A schematic illustration of an example of a prior art system 10 for landing a tubing hanger on a subsea well head is illustrated in Figure 1. In this figure is shown a tubing hanger 12, tubing hanger running tool 14, shear joint 16, cross-over 18, drill string 20, riser 22, drilling rig 24, umbilical 26, well head 28, seabed 30, production adapter base 32, blowout preventer (BOP) stack 34 containing a ram-type BOP 36.

Typically, to install the tubing hanger 12, it is mounted on a tubing hanger running tool 14 which is suspended from a drill string 20 via a shear joint 16, and crossover 18. The shear joint 16 is a portion of tubular which is capable of being sheared using a ram-type blowout preventer 36. The drill string 20 is lowered down a riser 22 which extends from a drilling rig 24 to a blowout preventer (BOP) stack 34 mounted on a production adapter base (also known as a tubing hanger spool) on top of the wellhead 32, until the tubing hanger 12 is landed in the internal profile of the production adapter base 32, and the shear joint 16 is aligned with a ram-type BOP 36 in the BOP stack 34. In an emergency situation, the ram- type BOP 36 can be operated to sever the drill string 20 and release the tubing hanger 12 and tubing hanger running tool 14, the BOP 36 thus sealing the well bore and allowing the drill string 20 to be withdrawn from the riser 22. When the tubing hanger 12 is mounted on a subsea wellhead 32, it is known to provide the tubing hanger 12 with ports for hydraulic and electrical connection to the surface. The electrical connections may, for example, be used to provide power to electrical sensors mounted on the tubing hanger 12. The hydraulic connections may provide means for operating downhole safety valves or may provide a port for the injection of chemicals into the wellbore. These ports are connected to an electrohydraulic umbilical 26 via the internal crossover 18, shear joint 16 and tubing hanger running tool 14. Each of the internal crossover 18, shear joint 16 and the tubing hanger running tool 14 includes passages for the hydraulic and electric connections, which, when these parts are mounted on the drill string 20, extend generally parallel to the drill string 20. Stab connections are provided to connect the corresponding passages in adjacent parts.

The various electrical and hydraulic connectors in the umbilical 26 are connected to the passages in the crossover 18 on the rig 24, before the drill string 20 is lowered into the riser. The umbilical 26 is clamped to the drill string 20 periodically, as the drill string 20 is lowered. This process is relatively time consuming, and clamping the umbilical 26 to the drill string 20 can add around 12 hours to the time taken to install the tubing hanger 12, and the process of unclamping the umbilical 26 can take a further 12 hours of rig time during the recovery process.

It is an object of the present invention to provide an improved system for and method of providing connections to such a tubing hanger mounted on a subsea wellhead.

According to a first aspect of the invention we provide a method of connecting a tubing hanger mounted on a subsea wellhead to equipment external to the tubing hanger, the method comprising a) securing a tubing hanger to an end of a drill string using a tubing hanger running tool assembly, and lowering the drill string from a drilling rig, so as to land the tubing hanger on or in the well head,

b) running an umbilical from the sea surface to the well head, and connecting the

umbilical to conduits in the tubing hanger via the tubing hanger running tool assembly, the umbilical being unconnected to the drill string other than via the tubing hanger running tool assembly.

In a preferred embodiment of the invention, the drill string is lowered to the well head inside a riser, the riser extending upwardly from a subsea wellhead to the drilling rig, and the umbilical is run to the well head outside the riser. The riser may extend upwardly from a blowout preventer stack to the drilling rig. The umbilical may be connected to the tubing hanger running tool assembly via an external connector which is connected to an external surface of the tubing hanger running tool assembly.

An end of the umbilical may be connected to a subsea umbilical termination assembly at or above sea level, and the subsea umbilical termination assembly lowered on a cable to the sea bed with the umbilical connected thereto, until the subsea umbilical termination assembly comes to rest on the sea bed. In this case, the subsea termination assembly may be connected to the external connector via at least one electrical or hydraulic flying lead.

The or each flying lead may be connected to the external connector using a remotely operated vehicle.

The umbilical may be lowered to the well head from the drilling rig. Alternatively, the umbilical may be lowered to the well head from a separate vessel.

The tubing hanger running tool assembly may have a first end which has the tubing hanger releasably suspended therefrom, a second end which is connected to the drill string, an end face at its first end and a radially outward facing surface which extends generally

perpendicular to the end face, wherein the tubing hanger running tool assembly is further provided with a conduit which extends from the end face to the radially outward facing surface, and which is connected to a corresponding conduit in the tubing hanger.

The tubing hanger running tool assembly may include a tubing hanger running tool at its first end, and a separate crossover part which is at its second end, the conduits extending from the end face of the tubing hanger running tool to the radially outward facing surface of the crossover part. In this case, the conduit in the tubing hanger running tool assembly is formed by a conduit portion in the tubing hanger running tool and a conduit portion in the crossover part, the conduit portions being connected by stab connectors. The tubing hanger running tool assembly and tubing hanger may be provided with a plurality of such conduits.

The conduit or at least one of the conduits may comprise a passage along which flow of fluid is permitted. The conduit or at least one of the conduits may comprise an electrical line.

The method may further comprise, prior to landing the tubing hanger in or on the well head, mounting on the well head a separate external crossover part which is generally tubular and has a radially inward facing surface which encloses a generally central space and a radially outward facing surface, and a passage which extends from the radially outward facing surface to the radially inward facing surface, and when lowering the drill string to land the tubing hanger in or on the well head, passing the tubing hanger through the generally central space of the external crossover part and when the tubing hanger is landed in or on the well head aligning the or each conduit emerging from the radially outward facing surface of the tubing hanger assembly with the passage in the external crossover part.

The external connector may be inserted into the passage of the external crossover part from outside the external crossover part to provide an electrical or fluid tight connection to the or each conduit in the tubing hanger running tool assembly.

The external connector may be mounted on the external crossover part before the external crossover part is mounted on the well head.

A blowout preventer stack may be mounted on top of the external crossover part.

The tubing hanger may be landed in a tubing hanger support part, known as production adapter base, tubing hanger spool or tubing head spool, which is mounted on top of and secured to the wellhead. Where an external crossover part is used, the external crossover part may be mounted on top of the tubing hanger support part.

According to a second aspect of the invention we provide a system for providing

connections to a tubing hanger mounted in a subsea wellhead, the system comprising a tubing hanger running tool assembly having a first end which is configured to have a tubing hanger releasably suspended therefrom, an end face at its first end and a radially outward facing surface which extends generally perpendicular to the end face, wherein the tubing hanger running tool assembly is further provided with at least one conduit which extends from the end face to the radially outward facing surface. In one embodiment, the tubing hanger running tool assembly includes a tubing hanger running tool at its first end, and a separate crossover part which is at a second end of the assembly, the conduits extending from the end face of the tubing hanger running tool to the radially outward facing surface of the crossover part. In this case, the conduit may be formed by a conduit portion in the tubing hanger running tool and a conduit portion in the crossover part, the conduit portions being connected by stab connectors.

The tubing hanger running tool assembly may be provided with a plurality of such conduits.

The conduit or at least one of the conduits may comprise a passage along which flow of fluid is permitted. The conduit or at least one of the conduits may comprise an electrical line.

The system may further comprise a separate external crossover part which is generally tubular and has a radially inward facing surface which encloses a generally central space and a radially outward facing surface, and a passage which extends from the radially outward facing surface to the radially inward facing surface, wherein the external crossover part is sized relative to the tubing hanger running tool assembly such that the tubing hanger running tool assembly fits into the generally central space with the or each conduit emerging from the radially outward facing surface of the tubing hanger assembly into the passage.

The system may further comprise a connector which is adapted to be inserted into the passage of the external crossover part from outside the external crossover part to provide an electrical or fluid tight connection to the conduits in the tubing hanger running tool assembly.

The system may further comprise an umbilical by means of which the conduits can be connected to surface equipment. In this case, the system may further comprise an umbilical termination assembly which is adapted to be connected to the umbilical, and to the connector via one or more flying hydraulic or electrical flying leads.

Embodiments of the invention will now be described, by way of example only, with reference to and as shown in the accompanying drawings, of which, FIGURE 2 shows a schematic illustration of a first embodiment of system according the second aspect of the invention,

FIGURE 3 shows a schematic illustration of a second embodiment of system according to the second aspect of the invention, FIGURE 4 is an illustration of the details of the internal crossover used in the systems illustrated in Figures 2 and 3, and

FIGURE 5 shows a schematic illustration of a longitudinal cross-section through the internal crossover, external crossover and external connector used in the systems illustrated in Figures 2 and 3. Referring now to Figures 2 and 3, there is shown a system 10 for providing connections to a tubing hanger 12 landed in a subsea wellhead 28. The tubing hanger 12 is located in a production adapter base 32 which is mounted on the wellhead 28. The system 10 includes a tubing hanger running tool assembly, which, in this example comprises a tubing hanger running tool 14 and separate crossover part 18', hereinafter referred to the internal crossover 18'. It will be appreciated that whilst these parts are generally separate, and mechanically connected together, they could equally be integrally formed in a single part.

The tubing hanger 12 is mounted on a lowermost end of a drill string 20 via the internal crossover 18' and tubing hanger running tool 14. The drill string 20 extends down from a drilling rig 24 into a riser 22, the riser 22 extending from the drilling rig 24 to a blowout preventer (BOP) stack 34 which is mounted on top of the production adapter base 32 via a second crossover part 38, hereinafter referred to as the external crossover 38. The BOP stack 34 has a main passage with a longitudinal axis which is generally aligned with a longitudinal axis of the drill string 20, and includes at least one ram-type blowout preventer which is aligned with the drill string 20 above the internal crossover 18'. The tubing hanger 12, and tubing hanger running tool 14 are of conventional construction, each include at least one conduit by means of which a hydraulic or electrical connection can be made between the tubing hanger 12 and external equipment. Typically, it is required to provide a plurality of both hydraulic and electrical connections to the tubing hanger for the reasons discussed in the introduction above. As such, in a preferred embodiment of the invention, a plurality of such conduits are provided, some providing electrical connectivity and some providing hydraulic connectivity.

The tubing hanger 12 is suspended from a lowermost end of the tubing hanger running tool 14 by conventional means.

As is conventional, each conduit in the tubing hanger 12 is connected to a corresponding conduit 15 in the tubing hanger running tool 14, in this example, by means of a stab connection. These connections are made in adjacent faces of the tubing hanger 12 and tubing hanger running tool 14 which extend generally perpendicular to the longitudinal axis of the BOP stack 34, i.e. the face at the uppermost end of the tubing hanger 12 and the face at the lowermost end of the tubing hanger running tool 14.

Each conduit in the tubing hanger running tool 14 is connected to a corresponding conduit 19 in the internal crossover 18', in this example, also by means of a stab connection. These connections are made in adjacent faces of the tubing hanger running tool 14 and internal crossover 18' which extend generally perpendicular to the longitudinal axis of the BOP stack 34, i.e. the face at the uppermost end of the tubing hanger running tool 14 and the face at the lowermost end of the internal crossover 18'.

The internal crossover 18' is illustrated in more detail in Figures 4 & 5, and has two generally parallel end faces 18a, 18b, and a side face 18c which extends between the two end faces 18a, 18b. In this example, the internal crossover 18' is generally cylindrical. The internal crossover 18' could, of course, be conical or frusto-conical, provided that side wall 18c is inclined such that the outer diameter of the lowermost end face 18a is less than the outer diameter of the uppermost end face 18b.

The internal crossover 18' differs from the conventional crossover 18 used in the prior art system described above in that the conduits 19 therein extend from the lowermost end face 18a, before turning through approximately 90° (depending on the exact angle between the end face 18a and the side wall 18c) to reach the side wall 18c. The external crossover 38 is tubular and has two ends, and a radially inward facing surface 38a and a radially outward facing surface 38b which extend between the two ends. System is arranged such that when the tubing hanger 12 is landed in the production adapter base 32, the internal crossover 18' is located in the space enclosed by the external crossover 38. The external crossover has a passage 38c which extends radially from the inward facing surface 38a to the outward facing surface 38b, and which is positioned such that the ends of the conduits 19 in the side wall 18c of the internal crossover 18' are aligned with the passage 38c in the external crossover 38. This means that the conduits in the tubing hanger 12 can be can be connected to the exterior of the external crossover 38 via the conduits 19 in the internal crossover 18' and the conduits in the tubing hanger running tool 14.

It will be appreciated that each conduit could comprise a passage or bore along which flow of fluid is permitted, or it could comprise an electrical line.

The system is further provided with an umbilical 26 which is used to connect the conduits in the tubing hanger 12 with the appropriate external equipment. The umbilical 26 is of conventional construction, and includes the required number of hydraulic and / or electrical lines to mate with the conduits in the tubing hanger 12.

A first end 26a of the umbilical 26 is located above sea level, whilst a second end 26b of the umbilical 26 is connected, by conventional means, to a subsea umbilical termination assembly 40, hereinafter referred to as SUTA 40, which rests on the sea bed 30. -The SUTA 40 has ROV panels with multi quick connection plates and electrical connector interface

(sockets) by means of which the hydraulic and electrical lines in the umbilical 26 may be connected to hydraulic and electrical flying leads.

The SUTA 40 is connected to the conduits 19 in the internal crossover 18' by hydraulic and/or electrical flying leads 42 and an external connector 44. As illustrated in Figure 5, the external connector 44 has a plurality of individual hydraulic or electrical stab connectors 38b each one of which extends along the passage 38c in the external crossover 38 into one of the conduits 19 in the internal crossover 18'. In this example, the external connector 44 is generally cylindrical, having a longitudinal axis which is arranged generally perpendicular to the longitudinal axis of the BOP stack 34. It also has a radially outwardly extending flange 44a by means of which the external connector 44 may be secured, using a plurality of bolts 48, to the radially outward facing surface 38a of the external crossover 38 around the passage 38c, as illustrated in Figure 5. It also includes a plurality of stab connectors 44b - one for each hydraulic or electrical connection to be made, which are movable between a retracted position and an extended position. This actuation of external connector could be performed hydraulic or mechanically

(torque/rotation) by ROV. By utilising the inventive system, the tubing hanger 12 may be installed in the production adapter base 32 as follows.

The external connector 44 is secured to the external crossover 38, using the bolts 48, at surface - either on the drilling rig 24 or on a separate vessel 50. At this point, the stab connectors 44b in the external connector 44 are retracted so that they extend only into the passage 38c of the external connector 44, and not into the volume enclosed by the inward facing surface 38a.

The external crossover 38 is then mounted on top of the production adapter base 32, the BOP stack 34 is secured on top of the external crossover 38, and the lowermost end of the riser 22 secured to the top of the BOP stack 34. The tubing hanger 12 is mounted on the end of the drill string 20 via the tubing hanger running tool 14 and the internal crossover 18', and the drill string 20 is lowered into the riser 22 from the drilling rig 24 until the tubing hanger 12 is landed in the production adapter base 32. The production adapter base 32 is provided with a shoulder, on which the tubing hanger 12 comes to rest. The shoulder is in the form of a helix (single or double helix), which assists in ensuring that the conduits 19 are aligned with the passage 38c in the external connector 38 when the tubing hanger 12 comes to a rest. The stab connectors 44b in the external connector 44 can then be extended along the passage in the external connector 38c to engage with the conduits 19 in the internal crossover 18' as illustrated in Figure 5. This is done without clamping the umbilical 26 to drill string 20, as a result of which, a weaker drill string 20 may be used with than in the prior art method discussed in the introduction above. This weaker drill string 20 can be severed by operating a ram-type BOP 36 in the BOP stack 34, and so it is not necessary to provide a shear joint 16 between the internal crossover 18 and the tubing hanger running tool 14 as in the prior art arrangement illustrated in Figure 1. This simplifies the installation procedure and reduces the number of interfaces in the system, and hence reduces the number of stab connectors required to make the necessary connections to the conduits 13 in the tubing hanger 12.

Avoiding the need to clamp the umbilical 26 to the drill string 20 may also significantly decrease the time taken to land the tubing hanger 12 in the production adapter base 32, which has significant cost benefits, as well as reducing the amount of activity in the moon pool during the installation procedure, which improves the safety of the procedure. Finally, in the prior art process, there is a risk that one or more of the clamps used to secure the umbilical 26 to the drill string 20 may fall into the well bore, and would need to be retrieved, thus adding to the installation time, and cost, of the procedure. This problem is avoided by using the inventive system.

The umbilical 26 is connected to the SUTA 40 above sea level, and the SUTA 40 is suspended from a cable, to which the umbilical is clamped, and lowered to the sea bed 30 using a conventional "Launch and Recovery System" which comprises a winch, heave compensator and umbilical reel 46. When the SUTA 40 is in place, the connections between the SUTA 40 and the external crossover are made using at least one remotely operated vehicle (ROV), which secures the external connector 44 to the SUTA 40 via the appropriate number of hydraulic or electrical flying leads to provide the desired number and type of connections from surface to the tubing hanger. The inventive system therefore separates the procedure of landing the tubing hanger 12 in the production adapter base 32, from the process of making the electrical and/or hydraulic connections to the tubing hanger 12, so that the two processes can be carried out simultaneously or at different times, depending on what fits in best with the overall completion process. The launch and recovery system may be mounted on the drilling rig 24 as illustrated in Figure 2, or on a separate vessel 50 as illustrated in Figure 3. Using a separate vessel 50 may be advantageous as it frees up space on the drilling rig 24, and facilitates quicker movement of the launch and recovery system for use in a different operation or on a different site.