WO2016022029A1

WO2016022029A1 - Tubing hanger position check tool and method

Info

Publication number: WO2016022029A1
Application number: PCT/NO2015/050131
Authority: WO
Inventors: Adam MILLBERG; Pawel RADGOWSKI; Matz OLLI; Viktor GRENNBERG; Conny HADDERS
Original assignee: Aker Subsea As
Priority date: 2014-08-05
Filing date: 2015-07-31
Publication date: 2016-02-11
Also published as: NO341890B1; NO20140963A1

Abstract

A tubing hanger position check tool (10) comprising a wellhead landing section (19, 21) and a wellhead lock (23) adapted to lock the tool (10) to a wellhead (1). The tool (10) has an alignment portion (30) which is rotationally and axially movable with respect to the wellhead landing section (19, 21). The alignment portion (30) comprises an alignment dog (41) adapted to fit into a tubing hanger alignment slot (27). The alignment portion (30) comprises a position determination means (11). A method is also disclosed.

Description

Tubing hanger position check tool and method

The present invention relates to the field of subsea wells and more particularly a tool for checking the correct position of a tubing hanger installed in a subsea wellhead. The tool according to the invention is a light weight, ROV operable tool that enables the operator to perform the position check in a quick and cost saving fashion.

Background

In a subsea well using a vertical Xmas tree, a tubing hanger (TH) is installed in the wellhead before the vertical Xmas tree (VXT) is installed above the tubing hanger. In order to ensure proper engagement between the TH and VXT, both the TH and the VXT are installed with respect to an orientation reference. In addition, the VXT needs to be correctly installed with respect to a production guide base (PGB) surrounding the wellhead. This is, inter alia, necessary to ensure that the interface of the VXT for peripheral infrastructure, such as fluid lines and control jumpers, are correctly positioned. Hence, the TH also needs a correct position with respect to the PGB.

Although the TH has been correctly installed, one wants to check the position of the TH before installing the VXT on top of it. If the VXT is installed on top of an incorrectly positioned TH, both the TH and the VXT may be damaged, resulting in large costs and loss of time. Due to various reasons, even if correctly installed, the TH may move after installation. Also the PGB may in some instances move. This can result in a misalignment between the TH and the PGB, and eventually between the VXT and the PGB, if the VXT is installed correctly, per se, on a TH (which is misaligned with respect to the PGB).

To check the position of the TH, it is known to lower a replica of the VXT down to the wellhead to see if it fits onto the TH when the replica is in the correct position. As the replica is a large and heavy piece of equipment, it is lowered on wire or a riser, which is a time consuming procedure. Moreover, due to its size and considerable weight, it may cause damage to the TH and to portions of the wellhead, such as seal surfaces. Patent application publication GB2099881 describes a tool for detecting and giving a remote indication of correct installation of an underwater well

component, such as a pipe hanger. Patent application publication EP1319800 discloses a borehole equipment position detection system. The system is arranged to determine the position of equipment within a bore.

An object of the present invention is to provide a novel tool and accompanying method for controlling the correct position of a TH installed in a wellhead in a faster, more cost effective and less damage exposed manner than in the prior art.

Another object of the present invention is to provide a novel assembly and a method of predicting a correct tubing hanger position of a tubing hanger in a wellhead.

The invention

According to a first aspect of the present invention, there is provided a tubing hanger position check tool comprising a wellhead landing section and a wellhead lock adapted to lock the tool to a wellhead. According to the first aspect of the present invention, the tool comprises an alignment portion (in the embodiment description below referred to as the central part) which is rotationally and axially movable with respect to the wellhead landing section. Moreover, the alignment portion comprises an alignment dog adapted to fit into a tubing hanger alignment slot. The alignment portion also comprises a position determination means.

The wellhead landing section is a part of the tool which is adapted to land on a wellhead. In a typical embodiment, it may involve a fitting ring surrounding the wellhead and a plate landing on top of the wellhead.

In some embodiments, the position determination means may be fitted onto the tool after the alignment portion has become aligned with the tubing hanger. The alignment portion can further comprise a guide rib and the wellhead landing section can comprise a guide rib entrance slot with which the guide rib is rotationally aligned when the alignment portion is axially movable. In some embodiments, the tool exhibits a storage position in which the guide rib is misaligned with the guide rib entrance slot and in which a spring biased clamp engages a clamp slot. In such embodiments the tool also exhibits an aligning position in which the guide rib is aligned with the guide rib entrance slot and in which the spring biased clamp is disengaged from the clamp slot. In a preferred embodiment, the clamp slot coincides or is the same slot as the guide rib entrance slot.

In some embodiments, the wellhead landing section can comprise a fitting ring adapted to encircle an upper portion of a wellhead, and a main plate connected to the fitting ring and adapted to land on top of the wellhead.

In such embodiments, the alignment portion can be arranged in an aperture in the main plate and can comprise a lower ring on which the wellhead landing section is adapted to rest when the tool is in a suspended position. In such a suspended position, the spring biased clamp will typically be engaged in the clamp slot to prevent mutual rotation between the alignment portion and the wellhead landing section.

An ROV handle can be arranged to the alignment portion. The alignment portion can then be rotated by means of an ROV.

The tubing hanger position check tool can comprise a tubing hanger height check pin which abuts a portion of the tubing hanger upon landing the tool on the wellhead, thereby becoming displaced upwards with respect to the tool.

The tool can advantageously be carried by a remotely operated vehicle. The design of the tool according to the invention is such that its weight can be limited compared to prior art solutions. For instance, the weight can typically be approximately 50 kg, however also more, particularly if provided with buoyancy arrangements.

The tubing hanger position check tool can comprise a position determination unit landing means and that the position determination means can be a position determination unit landed on said position determination unit landing means.

The position determination unit can comprise measuring devices arranged at different positions on the position determination unit.

The position determination means can also be a tubing hanger position prediction unit landed on a tubing hanger position prediction unit landing means of the tool, wherein the tubing hanger position prediction unit comprises a tubing hanger prediction alignment arm which is adapted to engage with a receiving slot in the production guide base. As will appear from the description of embodiment below, the tubing hanger prediction alignment arm of the TH position prediction unit can advantageously be an arm extending radially out from the TH position prediction unit. However, it may also have other configurations different from an "arm shape".

According to a second aspect of the present invention, there is provided a method of checking the position of a tubing hanger installed in a subsea wellhead. Thus method comprises the following steps

a) landing a tubing hanger position check tool on a wellhead in which the tubing hanger is installed;

e) aligning an alignment portion of the tool with the tubing hanger;

f) with a position determination means arranged on the alignment portion, determining the position of the tubing hanger. In an embodiment of the second aspect of the present invention, step e) further comprises rotating the alignment portion with respect to the tubing hanger until an alignment dog attached to the alignment portion enters a tubing hanger alignment slot. Advantageously, the method can comprise the following steps after step a) and before step f):

b) locking a landing section of the tool to the wellhead;

c) rotating the alignment portion with respect to the landing section, thereby enabling it to be lowered with respect to the landing section;

d) lowering the alignment portion with respect to the landing section, down to abutment with a landing shoulder in the tubing hanger.

In some embodiments, step f) can comprise the following steps:

i) landing a position determination unit on the tubing hanger position check tool in a predetermined mutual position;

ii) by means of measuring devices arranged at different positions on the position determination unit, determining the position of the tubing hanger. According to a third aspect of the present invention, there is provided a tubing hanger position determination assembly. The assembly comprises a wellhead landing section configured to be landed on and rotated with respect to the upper portion of a subsea wellhead. It also comprises a tubing hanger position prediction unit engaged with the wellhead landing section. The tubing hanger position prediction unit further has a tubing hanger prediction alignment arm and measuring devices. The measuring devices can advantageously be carried by legs extending out from a main body of the unit, in order to provide an

appropriate mutual distance between them. With the measuring devices, the operator is able to determine the position of the tubing hanger position determination assembly, an thus to determine a correct position of a tubing hanger which may already be installed or which is not yet installed in the wellhead. By knowing the correct position of a present or future tubing hanger, the operator will also know the position of a jumper interface of the Xmas tree to be installed above the tubing hanger. Hence, he may start designing and producing jumpers according to this known position, before the Xmas tree or even the tubing hanger is installed. According to a fourth aspect of the present invention, there is provided a method of predicting a correct tubing hanger position of a tubing hanger in association with a subsea wellhead. The method includes the following steps:

a) landing a wellhead landing section on a wellhead;

b) landing a tubing hanger position prediction unit on the wellhead landing section;

c) moving a tubing hanger prediction alignment arm of the tubing hanger position prediction unit into engagement with a receiving slot in the production guide base, thereby aligning the tubing hanger position prediction unit with the production guide base; and

d) with measuring devices arranged on the tubing hanger position prediction unit, determining the correct tubing hanger position.

The wellhead landing section can be parts of the tubing hanger position check tool disclosed above, or may be other components which are not equipped for checking the position of an installed tubing hanger.

Step a) and step b) above may indeed be performed simultaneously in an embodiment where the wellhead landing section is attached to tubing hanger position prediction unit during landing onto the wellhead.

Example of embodiment

While the general features of the present invention has been described above, a more detailed and non-limiting example of embodiment will be described in the following with reference to the drawings, in which

Fig. 1 is a schematic side view of a subsea wellhead and a tool being installed on the wellhead;

Fig. 2 is a schematic perspective view of the wellhead and the tool, wherein the tool has landed on the wellhead;

Fig. 3a and Fig. 3b are a side view and a perspective view of the tool being

installed onto the wellhead;

Fig. 4a and Fig. 4b are a side cross section view and a perspective cross section view of the tool having landed onto the wellhead; Fig. 5 is an enlarged cross section perspective view of the tool landed on the wellhead;

Fig. 6 is an enlarged perspective view of the tool according to the invention; Fig. 7a and Fig. 7b are a cross section side view and perspective view of the tool on the wellhead, after rotation of the central part of the tool;

Fig. 8a and Fig. 8b are a cross section side view and perspective view of the tool and wellhead, wherein the central part has been somewhat lowered; Fig. 9a and Fig. 9b are a cross section side view and perspective view of the tool and wellhead, wherein the central part of the tool is aligned with a tubing hanger in the wellhead;

Fig. 10 is an enlarged cross section view of the tool landed on the wellhead; Fig. 1 1 is an enlarged side view of the tool according to the invention;

Fig. 12 is another enlarged side view of the tool, shown in another situation; Fig. 13 is another enlarged side view of the tool, shown in yet another situation; Fig. 14a and Fig. 14b are a side cross section view of the tool and the wellheand, as well as an enlarged perspective view of parts of the tool;

Fig. 15 is a perspective view of an alternative embodiment of the tool according to the invention;

Fig. 16 is a perspective view according to Fig. 15, shown in another position; Fig. 17 is another view according to Fig. 15, shown with a position determination unit;

Fig. 18 is an enlarged perspective view of the alternative embodiment of the tool, shown with the position determination unit landed onto the tool;

Fig. 19 is yet another embodiment shown in a perspective view;

Fig. 20 is a perspective view of the embodiment of Fig. 19, landed onto a

wellhead; and

Fig. 21 is another perspective view illustrating the embodiment shown in Fig. 19 and Fig. 20.

Fig. 1 is a principle side view of a subsea wellhead 1 of a subsea well 3 that extends into the seabed 5. The wellhead 1 is surrounded by a production guide base 7 (PGB). Above the wellhead 1 is shown a tubing hanger position check tool 10 (THPCT) according to the invention (hereinafter called tool). In this embodiment the tool 10 is carried by a remotely operated vehicle 9 (ROV), the arm of which is shown in Fig. 1 .

Fig. 2 is a perspective principle view showing substantially the same components as in Fig. 1 . However, the tool 10 is landed onto the wellhead 1 . As will be described in detail further below, the tool 10 is aligned with a TH which is installed in the wellhead 1. A laser arrangement 1 1 emits a laser beam onto a target plate 13 which is fixed to the PGB 7. The position of the laser beam on the target plate 13 is then read in order to determine the orientation of the TH. This can be done for instance with a camera on an ROV, or through a reading arrangement which may be arranged, e.g., on the tool 10 or on the PGB 7. Fig. 1 and Fig. 2 illustrate the overall concept for determining or checking the angular position of the TH within the wellhead 1 . In the following, the functions of the tool 10 will be discussed in detail.

Fig. 3a and Fig. 3b illustrate the same situation as shown in Fig. 1 in better detail. The ROV 9 is about to land the tool 10 onto the wellhead 1 , within which a TH (not shown) is installed. Preferably, the tool 10 is lowered down to the seabed 5 in a basket. The weight of the tool 10 is advantageously sufficiently low to be carried and manipulated by the ROV 9, for instance 50 kg. In this embodiment, the tool 10 has a first and a second ROV handle, here in the form of an upper ROV handle 15 and a lower ROV handle 17. When landing the tool 10 on the wellhead 1 , the ROV 9 carries the entire tool 10 in the upper ROV handle 15. In Fig. 4a and Fig. 4b the tool 10 has been landed onto the top of the wellhead 1 . The tool 10 comprises a fitting ring 19 which, when in the landed position, extends about the outer and upper circumference of the wellhead 1 . The fitting ring 19 is attached to a main plate 21. As appears from Fig. 3b and Fig. 4b, the main plate 21 only covers a portion of the area within the fitting ring 19, as it exhibits a plurality of portions which are open. This design reduces the weight of the tool 10 itself and also reduces the added mass when lowering or lifting the tool 10 through the seawater. Once landed on the wellhead 1 , the ROV 9 releases its grip of the upper ROV handle 15, letting the tool 10 rest on the wellhead 1 . The lower handle 17 is functionally connected to a fitting ring lock 23. By rotation of the lower handle 17, the ROV 9 locks the fitting ring to the wellhead 1 . The function of the fitting ring lock 23 is not described herein, as a person skilled in the art may use any appropriate solution. For instance, a concentric element may be connected to the lower handle 17 through a bolt which is attached eccentrically to the concentric element. Upon rotation of the lower handle 17 and the bolt, the concentric element may be forced into engagement with the outer face of the wellhead 1 , thereby fixing the fitting ring 19 to the wellhead 1 .

In Fig. 4a and Fig. 4b, the tubing hanger (TH) 25 can be seen installed within the inner bore of the wellhead 1 . In the perspective view of Fig. 4b, one can see various parts of the TH 25, such as the production bore, annulus access bore, and various connectors. Also appearing in Fig. 4b is a tubing hanger alignment slot 27. Typically, the TH 25 will have two such alignment slots 27. Advantageously, they are arranged in the inner, upper TH bore 29 of the TH 25, and positioned with 170 degrees between them, with respect to the inner periphery TH bore 29. Fig. 5 is an enlarged portion of Fig. 4b, illustrating parts of the tool 10 and the TH 25 in more detail. Several parts will now be identified with reference to Fig. 5.

Centrally arranged in the main plate 21 is an alignment portion, here in the form of a central part 30, on top of which the upper ROV handle 15 is arranged. The central part 30 is rotationally supported on the main plate 21 through a circular slide bearing 31 which is attached to the main plate 21 . Thus, the ROV 9 is able to rotate the central part 30 with respect to the main plate 21 , when the main plate 21 is locked to the wellhead 1 by means of the fitting ring lock 23. Moreover, the central part 30 is adapted to move up and down, i.e. axially, with respect to the main plate 21. In the position shown in Fig. 5, however, this is not yet possible. Attached to the central part 30 are two guide ribs 33 which, in the shown position, rest on the slide bearing 31 . The slide bearing 31 , as well as the main plate 21 , have two guide rib entrance slots 35, through which the two guide ribs 33 can be lowered when they are aligned with the guide rib entrance slots 35. Hence, in order to move the central part 30 axially downwards with respect to the main plate 21 and the wellhead 1 , the central part is rotated by the ROV 9 until the guide ribs 33 are aligned with the guide rib entrance slots 35. This position is shown in Fig. 7a and Fig. 7b. When in this position, the central part is lowered until landing on a landing shoulder 26 within the TH bore 29.

The central part 30 further comprises a lower ring 37, which in the position shown in Fig. 5, is arranged directly below the main plate 21. Down from the lower ring 37 depend two alignment dog flanges 39. On each alignment dog flange 39 there is arranged a radially outward protruding alignment dog 41 . The two alignment dogs 41 are adapted to enter down into the two TH alignment slots 27 which were discussed above. Fig. 6 is a perspective view of the tool 10, showing clearly a guide rib entrance slot 35 and a guide rib 33 which is yet not aligned with the guide rib entrance slot 35. Upwards from the lower ring 37 a spring biased clamp 43 extends into the guide rib entrance slot 35. The spring biased clamp 43 exhibits inclined side faces and will be pressed down upon rotation of the body of the slide bearing 31 . Thus, the spring biased clamp 43 ensures that the central part 30 and the main plate 21 remains in a constant mutual position, until the above discussed intended rotation shall take place.

Reverting to Fig. 7a and Fig. 7b. The fitting ring 19 is locked to the wellhead 1 by means of the fitting ring lock 23. The ROV 9 grips the upper ROV handle 15 and has rotated the central part 30 with respect to the fitting ring 19 and the main plate 21 , until the two guide ribs 33 have become aligned with the guide rib entrance slots 35. The spring biased clamp 43 was forced down into the lower ring 37 during this rotational movement. In Fig. 7a, a spring 45 is visible below the spring biased clamp 43.

Fig. 8a and Fig. 8b show a situation where the central part 30 has been lowered down with respect to the remaining main plate 21 . The alignment dogs 41 has landed on the landing shoulder 26 (cf. Fig. 5) in the TH 25. In some cases, the alignment dogs 41 may already be aligned with the tubing hanger alignment slots 27. In such a case, the central part 30, along with the alignment dogs 41 , will continue the downwards movement without landing on the landing shoulder 26.

Normally, however, the alignment dogs 41 will land on the landing shoulder 26. In order to move further down into the tubing hanger alignment slots 27, the tool 10 must be rotated with respect to the wellhead 1 and the TH 25. Hence, the fitting ring lock 23 is disengaged so that the entire tool 10 can rotate. The ROV 9 rotates the tool 10, along with the central part 30 and the alignment dogs 41 , until the latter are aligned with the tubing hanger alignment slots 27. Then the central part 30 moves into the lowermost position, in which it is rotationally aligned and engaged with the TH 25. This position is shown in Fig. 9a and Fig. 9b. As shown in Fig. 9a and fig. 9b, two stop flanges 36 abut the main plate 21 when in this position and thus halts the downward movement of the central part 30.

Fig. 10 is a perspective view of the tool 10 in the situation shown in Fig. 5, however shown from another view.

Fig. 1 1 is a side view of the tool 10 before lowering the central part 30.

Fig. 12 is another side view corresponding to Fig. 1 1 , however showing the situation shown in Fig. 8a and Fig. 8b.

Fig. 13 is yet another side view showing the tool in the final lowered and aligned position, corresponding to the situation in Fig. 9a and Fig. 9b. Reverting now to the principle drawing of Fig. 2. Once the tool 10 is in the lowered and aligned position, the laser arrangement 1 1 is employed to check the orientation of the tool 10, and hence the TH 25, with respect to the laser target plate 13.

As will be appreciated by the person skilled in the art, other position

determination means can be used instead of the laser 1 1 , for instance

transmitters/transponders/gyroscopes. One may even use mechanical measuring, such as an extendable bar which, by means of the ROV can be extended towards a painted target scale and inspected with camera. Such bars can also be retrofitted to the tool after installation and alignment. Another alternative is to have a camera on the tool 10 which take a picture of the TH position within the wellhead. Such a picture can then be compared with the optimal TH position and the actual orientation is thus verified.

Fig. 14a and Fig. 14b illustrate an optional embodiment of the present invention. In this embodiment, the tool 10 is provided with a tubing hanger height check pin 51 . When the tool 10 has been lowered onto the wellhead 1 , a lower portion of the tubing hanger height check pin 51 will abut an upper face of the wellhead 1 , and thereby become moved upwards with respect to the tool 10. A (not shown) indication ring on the check pin 51 will appear above the upper rim of a support sleeve 53, by means of which the check pin 51 is supported. That is, the check pin 51 extends through the support sleeve 53 in a sliding manner.

Fig. 15 and Fig. 16 illustrate an alternative embodiment of the present invention. In this embodiment, the tool 10 is provided with a landing plate 55. The landing plate 55 is connected to the central part 30 of the tool 10, above the guide ribs 33. Extending upwards from the landing plate 55 are a first guide pin 57 and a second guide pin 59, which are of different shape. In the situation shown in Fig. 16, the tool 10 has been aligned with the TH 25 within the wellhead 1 in the manner discussed above. As appreciated from Fig. 15 and Fig. 16, in this embodiment, the tool 10 is without the laser arrangement 1 1. Instead, a position determination unit 100 is adapted to land onto the landing plate 55 of the tool 10. Fig. 17 shows a situation where the position determination unit 100 is about to land. Typically, the position determination unit 100 is operated with an ROV. The operator will make sure that the first and second guide pins 57, 59 on the tool 10 enters into mating recesses (not shown) in the position determination unit 100. Since the first and second guide pins 57, 59 are of different shapes, there will be only one possible mutual and engaged position between the tool 10 and the position determination unit 100 when the guide pins are engaged in the recesses. Hence, since the tool 10 is correctly aligned with respect to the TH 25 within the wellhead 1 , the position of the position

determination unit 100 is also known.

In Fig. 18 the position determination unit 100 is shown in a landed position on the tool 10. The position determination unit 100 exhibits a central opening through which the upper ROV handle 15 extends, together with the upper portion of the central part 30.

The position determination unit 100 exhibits a plurality of radially extending legs 101 , four legs in this embodiment. The legs 101 extend substantially radially out from a common main body 103. At an outer end portion of the legs 101 , they each have a receiving receptacle 105. The receiving receptacles are adapted to receive measuring devices 107 which are used to determine the position/ orientation of the position determination unit 100. In this embodiment the measuring devices are transponders 107. Preferably, the operator may use an ROV to place the transponders 107 into the receiving receptacles after the position determination unit 100 has landed onto the tool 10.

This embodiment, which includes the position determination unit 100, enables the operator to know the position of the entire system, i.e. the PGB 7, TH 25 and the manifold (not discussed herein). As a result, he may start the manufacturing of tie-in jumpers before installation of the VXT. This will contribute in saving significant time for the operator. Moreover, the operator is able to determine the future routing of tie-in jumpers and the position of the tie-in connectors before the VXT is installed on top of the TH 25. Fig. 19 depicts yet another embodiment. This embodiment includes a TH prediction unit 200. The TH prediction unit 200 is used for determining or predicting a correct present or future position / orientation of the tubing hanger (TH) 25. That is, it may be used in a situation where the TH 25 is installed in the wellhead 1 , as well as in a situation where the TH is not yet installed.

About the wellhead 1 there is arranged an orientation can 8 which is a part of the PGB 7. In the orientation can 8 there are four Y-slots 6. Generally, the TH prediction unit 200 is shaped according to the position determination unit 100, and similar components will not be discussed again. However, the TH prediction unit 200 additionally comprises a tubing hanger prediction alignment arm 209. In the shown embodiment the tubing hanger prediction alignment arm 209 is attached to two legs 201 of the TH prediction unit 200. In some embodiments the tubing hanger prediction alignment arm 209 may be supported in a pivoting manner, so that it may pivot about its attachment points to the legs 201 . As will be understood by the person skilled in the art, the tubing hanger prediction alignment arm 209 may have any suitable shape which will fulfill its technical purpose. Hence, it needs not be shaped like an arm.

Fig. 20 depicts the TH prediction unit 200 landed on a tool 10 which is already landed onto the wellhead 1 . As with the position determination unit 100 discussed above, the TH prediction unit 200 also exhibits the first and second guide pins 57, 59. After landing the PGB position unit 200 on the tool 10, they are both rotated until the tubing hanger prediction alignment arm 209 aligns with and engages a Y-slot 6 in the orientation can 8 of the PGB 7. In order to render such rotation possible, the fitting ring lock 23 of the tool 10 is not engaged. Alternatively the fitting ring lock 23 is not at all present. Hence, the tool 10 rotates freely on the wellhead 1 . Moreover, the first and second guide pins 57, 59 on the landing plate 55 makes the TH prediction unit 200 rotate upon rotation of the tool 10. To rotate the tool 10, an ROV 9 can be used, engaging the upper ROV handle 15. In this embodiment, the tool 10 is merely used as a landing means for the TH prediction unit 200, and as a rotating interface with the wellhead 1 . Thus, the tool 10 may have been landed onto the wellhead 1 without any TH being present in the wellhead 1 . In such a case, the tool may be a stripped version of the tool 10 discussed above, since it will not need to engage a TH and it will thus not need to exhibit an axially / vertically moving central part 30. For instance, the TH prediction unit 200 may land onto and/or be engaged with a simple wellhead landing section which merely provides for landing on the wellhead and the possibility of rotation with respect to the wellhead.

At an end portion of the tubing hanger prediction alignment arm 209 there is provided a slot engagement unit 21 1 which fits snuggly into the lower part of the Y-slot 6. Thus, when the slot engagement unit 21 1 is in the engaged position, the TH prediction unit 200 is oriented with respect to the PGB 7 with high accuracy. By means of the measuring devices 207, corresponding to those discussed above, the operator is now able to precisely determine the correct position of a TH 25, which may or may not be installed in the wellhead 1. Advantageously, the tubing hanger prediction alignment arm 209 and/or the engagement unit 21 1 are easily replaceable in order to adapt to various shapes of the PGB 7, in particular various shapes of the orientation can 8 and its Y-slots 6. As will be appreciated by the skilled person in the art, this embodiment, including the TH prediction unit 200, does not make use of the tubing hanger alignment slot 27 in order to determine the correct position of a TH. When the TH 25 is installed, it will typically be aligned with respect to the Y-slot 6. Fig. 21 is an overall side view showing the PGB 7, the wellhead 1 , the tool 10 and the PGB position unit 200.

With the embodiment including the TH prediction unit 200, the operator is able to determine the future position of the tie-in jumpers that will connect to the Xmas tree. Thus, he may start producing the jumpers even before the TH 25 is installed in the wellhead.

Claims

1 . A tubing hanger position check tool (10) comprising a wellhead landing section (19, 21 ) and a wellhead lock (23) adapted to lock the tool (10) to a wellhead (1 ), characterized in that

- the tool (10) comprises an alignment portion (30) which is rotationally and axially movable with respect to the wellhead landing section (19, 21 );

- the alignment portion (30) comprises an alignment dog (41 ) adapted to fit into a tubing hanger alignment slot (27); and that

- that the alignment portion (30) comprises a position determination means (1 1 ).

2. A tubing hanger position check tool (10) according to claim 1 , characterized in that the alignment portion (30) further comprises a guide rib (33) and the wellhead landing section (19, 21 ) comprises a guide rib entrance slot (35) with which the guide rib (33) is rotationally aligned when the alignment portion (30) is axially movable.

3. A tubing hanger position check tool (10) according to claim 2, characterized in that it exhibits

- a storage position in which the guide rib (33) is misaligned with the guide rib entrance slot (35) and in which a spring biased clamp (43) engages a clamp slot (35); and

- an aligning position in which the guide rib (33) is aligned with the guide rib entrance slot (35) and in which the spring biased clamp (43) is disengaged from the clamp slot (35).

4. A tubing hanger position check tool (10) according to one of the preceding claims, characterized in that the wellhead landing section (19, 21 ) comprises a fitting ring (19) adapted to encircle an upper portion of a wellhead (1 ), and a main plate (21 ) connected to the fitting ring (19) and adapted to land on top of the wellhead (1 ).

5. A tubing hanger position check tool (10) according to claim 4, characterized in that the alignment portion (30) is arranged in an aperture in the main plate (21 ) and comprises a lower ring (37) on which the wellhead landing section (19, 21 ) is adapted to rest when the tool (10) is in a suspended position.

6. A tubing hanger position check tool (10) according to one of the preceding claims, characterized in that an ROV handle (15) is arranged to the alignment portion (30).

7. A tubing hanger position check tool (10) according to one of the preceding claims, characterized in that it comprises a tubing hanger height check pin (51 ) which is adapted to abut a portion of the tubing hanger (25) upon landing the tool on the wellhead (1 ), thereby becoming displaced upwards with respect to the tool (10).

8. A tubing hanger position check tool (10) according to one of the preceding claims, characterized in that it is carried by a remotely operated vehicle.

9. A tubing hanger position check tool (10) according to one of the preceding claims, characterized in that it comprises a position determination unit landing means (55, 57, 59) and that the position determination means (1 1 ) is a position determination unit (100) landed on said position determination unit landing means (55, 57, 59).

10. A tubing hanger position check tool (10) according to claim 9, characterized in that the position determination unit (100) comprises measuring devices (107) arranged at different positions on the position determination unit (100).

1 1. A tubing hanger position check tool (10) according to one of the claims 1 to 9, characterized in that the position determination means is a tubing hanger position prediction unit (200) landed on a tubing hanger position prediction unit landing means (55, 57, 59) of the tool (10), wherein the tubing hanger position prediction unit (200) comprises a tubing hanger prediction alignment arm (209) which is adapted to engage with a receiving slot (6) in the production guide base (7).

12. Method of checking the position of a tubing hanger (25) installed in a subsea wellhead (1 ), comprising the following step:

a) landing a tubing hanger position check tool (10) on a wellhead (1 ) in which the tubing hanger (25) is installed;

characterized in that the method further comprises the following steps :

e) aligning an alignment portion (30) of the tool (10) with the tubing hanger (25); f) with a position determination means (1 1 ) arranged on the alignment portion (30), determining the position of the tubing hanger (25).

13. Method according to claim 12, characterized in that step e) further comprises: rotating the alignment portion (30) with respect to the tubing hanger (25) until alignment dog (41 ) attached to the alignment portion (30) enters a tubing hanger alignment slot (27).

14. Method according to claim 13, characterized in that it comprises the following steps after step a) and before step f):

b) locking a landing section (19, 21 ) of the tool (10) to the wellhead (1 );

c) rotating the alignment portion (30) with respect to the landing section (19, 21 ), thereby enabling it to be lowered with respect to the landing section (10, 21 ); d) lowering the alignment portion (30) with respect to the landing section (10, 21 ), down to abutment with a landing shoulder (26) in the tubing hanger (25).

15. Method according to one of the claims 12 to 14, characterized in that step f) comprises:

i) landing a position determination unit (100) on the tubing hanger position check tool (10) in a predetermined mutual position;

ii) by means of measuring devices (107) arranged at different positions on the position determination unit (100), determining the position of the tubing hanger (25).

16. A tubing hanger position determination assembly, characterized in that it comprises

- a wellhead landing section (19, 21 ) configured to be landed on and rotated with respect to the upper portion of a subsea wellhead (1 );

- a tubing hanger position prediction unit (200) engaged with the wellhead landing section (19, 21 );

wherein the tubing hanger position prediction unit (200) further comprises a tubing hanger prediction alignment arm (209) and measuring devices (207).

17. Method of predicting a correct tubing hanger position of a tubing hanger in association with a subsea wellhead (1 ), comprising the following step:

a) landing a wellhead landing section (19, 21 ) on a wellhead (1 );

characterized in that the method further comprises the following steps:

b) landing a tubing hanger position prediction unit (200) on the wellhead landing section (19, 21 );

c) moving a tubing hanger prediction alignment arm (209) of the tubing hanger position prediction unit (200) into engagement with a receiving slot (6) in the production guide base (7), thereby aligning the tubing hanger position prediction unit (200) with the production guide base (7); and

d) with measuring devices (207) arranged on the tubing hanger position prediction unit (200), determining the correct tubing hanger position.