Wellhead assemblies and methods

Abstract

A wellhead assembly (Fig.1 100) comprising: a foundation (Fig.1 101) having at least one well slot (Fig.1 200); the well slot comprising a receptacle 102 having an internal profile (Fig.3 103) for holding a well pipe (Fig.2 201); a sleeve 110 arranged in the receptacle; wherein the sleeve is vertically movable and has a top end 111 which in a first position is located above the internal profile and in a second position is located below the internal profile. Also provided is a method of installing a wellhead assembly at a seabed 130, wherein the foundation is lowered to the seabed, the sleeve is lowered into the well slot below the surface of the seabed, and a casing is inserted into the sleeve. The casing is then cemented to the sleeve to fix it in place. The sleeve of the present invention supports and guides the inserted casing, and prevents loose sediment near the seabed surface from being disturbed during cementing.

Description

The present invention relates to subsea wellhead assemblies and methods, including but not limited to assemblies and methods for installing well pipes as part of a seabed structure. BACKGROUND Wellhead systems for subsea hydrocarbon production, carbon dioxide storage or similar applications are traditionally known to comprise a wellhead having a wellhead housing secured to a well casing extending into the earth towards a hydrocarbon reservoir or other subsurface geological structure. A foundation, such as a frame or a template, is often positioned on the seabed and used to support the wellhead and associated equipment. Publications which may be useful to understand the present disclosure include EP 3 333 358 A1; WO 2022 / 265516 A1; US 4822212 A; WO 2012 / 065896 A2; and NO 314320 B1. During the construction of hydrocarbon wells and the installation of well pipes, it is common to inject cement between the earth formation and the outermost pipe, and in annuli between pipes in the well. During the initial stages of well construction, when the wellbore closest to the seabed is constructed, control of the return cement may pose a challenge, which can lead to increased cement usage, longer operational time, and / or interference with equipment or other operations. It is also desirable to minimise movement of the seabed around the installed foundation during preparation of the wellbore, to avoid interfering with the support of the well and drilling operation. Due to the high costs of offshore well construction operations, often involving specialised and costly vessels, and the potentially serious consequences of irregularities in the safety-critical components making up the subsea wellhead system, there is a continuous need for improved technology in this area. The present disclosure has the objective to provide such improvements, or at least alternatives to the state of the art. SUMMARY In an example, there is provided a wellhead assembly comprising: a foundation having at least one well slot; the at least one well slot comprising a receptacle having an internal profile for holding a well pipe; a sleeve arranged in the receptacle; wherein the sleeve is vertically movable and has a top end which in a first position of the sleeve is located above the internal profile and in a second position of the sleeve is located below the internal profile. In an example, there is provided a method of installing a wellhead assembly at a seabed, the method comprising: positioning a foundation at the seabed, the foundation having at least one well slot; providing a sleeve; bringing the sleeve into the seabed at the at least one well slot; lowering a well pipe through the sleeve and into the seabed; and cementing the well pipe in place inside the sleeve. Various further embodiments and examples are outlined in the detailed description and claims below, and in the appended drawings. BRIEF DESCRIPTION OF THE DRAWINGS These and other characteristics will become clear from the following description of illustrative embodiments, given as non-restrictive examples, with reference to the attached drawings, in which: Fig 1 illustrates a subsea wellhead assembly. Fig 2 illustrates details of the subsea wellhead assembly, hereunder a receptacle holding a wellhead housing. Figs 3 and 4 illustrate a receptacle for a wellhead assembly having a sleeve which is movable between two positions. DETAILED DESCRIPTION Fig. 1 illustrates a wellhead assembly 100 for a subsea field. A foundation 101, such as a frame or a template, has at least one well slot 200 for supporting a wellhead and associated equipment. In the illustrated example, the foundation 101 has six well slots 200 defined by a horizontal beam structure making up the foundation 101, but the foundation 101 may have fewer than six or more than six well slots 200. The foundation 101 may optionally be of a different type, such as a single-well suction anchor foundation. Shown in closer detail in Fig. 2, each well slot 200 has a receptacle 102 for holding a well pipe 201. The well pipe 201 may be a low pressure pipe or a high pressure pipe, and may comprise a housing with a pipe connected thereto and which extends downwardly into the earth. In the case of a low pressure pipe, the well pipe housing may be a conductor housing, which itself can be configured to receive and hold a high-pressure housing, which may be a wellhead. The assembly 100 may, when installed, comprise a low pressure pipe (such as a conductor) with a low pressure housing landed and locked in the receptacle 102 and a high pressure pipe with a high pressure housing (such as a wellhead) landed and locked in the low pressure housing. As will be understood by the skilled reader, the terms low pressure and high pressure in this context differentiate between pipes which are configured for holding and handling reservoir and well fluid pressures, and those which are not configured for holding such high internal pressures. Optionally, the well pipe 201 may be a high pressure pipe with a housing arranged directly in the receptacle 102 without a low pressure housing therebetween, for example in a so-called conductorless well arrangement. Figs 3 and 4 illustrate the receptacle 102 in closer detail, in a cut view. The receptacle 102 has an internal profile 103 configured for receiving and holding the well pipe 201. The internal profile 103 may comprise, for example, shoulders for landing and carrying a weight of the well pipe 201 (and optionally any associated pipes connected to the well pipe 201), lock faces for locking the well pipe 201 in the receptacle 102, seal faces to cooperate with seals between the well pipe 201 and the receptacle 102, etc. The receptacle 102 further has at least one cement port 106. A movable sleeve 110 is arranged in the receptacle 102. The sleeve 110 may be a tubular member, and may for example be a tail pipe or washout sleeve configured to reduce unwanted cratering or other undesirable interaction with the seabed 130 during construction of a wellbore at the respective well slot 200. The sleeve 110 is movable between a first position, illustrated in Fig. 3, and a second position, illustrated in Fig. 4. In the first position, a top end 111 of the sleeve 110 is located above the internal profile 103 and in the second position the top end 111 is located below the internal profile 103. In the first position, as illustrated in Fig. 3, a bottom end 113 of the sleeve 110 may be located inside the receptacle 102, i.e. above a lowermost end of the receptacle 102. Alternatively, the bottom end 113 may be below the receptacle 102 but above the seabed 130. The receptacle 102 may be held above a seabed 130 (see Fig. 4) by the foundation 101. The sleeve 110 may have a length which is greater than a length of the receptacle 102, and the sleeve 110 may extend upwardly out of the receptacle 102 in the first position, as illustrated in Fig. 3. In the second position, as illustrated in Fig. 4, the sleeve 110 extends from the receptacle 102 and into the seabed 130, while still being (directly or indirectly) connected to the receptacle 102. In the second position, the top end 111 may be located below the at least one cement port 106 of the receptacle 102. The top end 111 may in the second position be located inside the receptacle 102 or inside a vertical downwardly extension 102a of the receptacle 102, which for the purposes of this disclosure is considered part of the receptacle 102. In use, the wellhead assembly 100 can be installed by positioning the foundation 101 at the seabed 130. The receptacle 102 may be a part of the foundation 101 when the foundation 101 is lowered to the seabed 130. The sleeve 110 may also be arranged at and thus installed together with the foundation 101 when the foundation 101 is lowered to the seabed 130. Optionally, the sleeve 110 can be lowered and positioned in the receptacle 102 after the foundation 101 has been placed on the seabed 130, for example via wireline from a surface vessel. When preparing the top hole, i.e. the uppermost part of the well extending into and directly below the seabed 130, the relevant well construction equipment can be run through the sleeve 110. This may, for example, include jetting equipment or drilling equipment, to prepare the uppermost parts of the well. The sleeve 110 may be arranged to be movable relative to the receptacle 102 while preparing the uppermost parts of the well, such that the sleeve 110 can move into the well as the top hole is being prepared (e.g. by its own gravity or by downforce from the well construction equipment). Alternatively, the sleeve 110 can be driven into the seabed 130, for example by weight, by suitable equipment therefor (e.g. by jarring), or by other means. The sleeve 110 is moved into the seabed 130 and soil until it reaches the second position, as illustrated in Fig. 4. The assembly 100 may comprise a sleeve lock mechanism operable to lock the sleeve 110 in the second position, to prevent longitudinal movement of the sleeve 110 relative to the receptacle 102 when the sleeve 110 is in the second position. The sleeve lock mechanism can be arranged to automatically engage and lock the sleeve 110 relative to the receptacle 102 when the sleeve 110 reaches the second position when moved from the first position. In the schematically illustrated example in Figs 3 and 4, the sleeve lock mechanism is a sleeve lock member 104 in the form of a split ring, arranged at a top end part 112 of the sleeve 110, e.g. near or directly below the top end 111. The sleeve lock member 104 is configured to engage a lock face 120, such as a groove or recess, arranged below the internal profile 103 in the receptacle 102. Alternatively, the sleeve lock member, such as a split ring, may be arranged in the receptacle 102, and the lock face, such as a groove or recess, may be arranged at the top end part 112 of the sleeve 110. The lock member and lock face may comprise any other suitable mechanism, such as locking dogs, clamps or the like. The lock mechanism may be self-activating, for example by means of spring preload, when the sleeve 110 reaches the second position. Optionally, the lock mechanism may be operable and engageable from outside the receptacle 102, for example by means of an ROV. The sleeve 110 can in this manner be locked in place when reaching the second position, as illustrated in Fig. 4. A vertical lock 105 may be provided, and operable to temporarily hold the sleeve 110 fixed in the first position. This may, for example, be advantageous to ensure that the sleeve 110 remains in the first position and fixed relative to the receptacle 102 during installation of the foundation 101 at the seabed 130. The vertical lock 105 may have an unlock interface 105a via which the vertical lock 105 can be released, such as to release the sleeve 110. The unlock interface 105a can, for example, be engageable by an ROV from outside the receptacle 103, by well construction equipment inside the sleeve 110, or by other means. In the illustrated example, the vertical lock 105 is arranged at the receptacle 102 and engaging the sleeve 110. Optionally, the vertical lock 105 can be provided at the sleeve 110, e.g. in the form of a removable lock pin resting against a surface on the receptacle 103, or other mechanisms. In order to ensure reliable movement of the sleeve 110 relative to the receptacle 102, two vertically spaced support faces 120,122 can be provided for alignment of the sleeve 110 inside the receptacle. In this manner, it can be ensured that the sleeve 110 moves vertically downwardly, and not at an undesired angle. The support faces 120,122 can be arranged with a clearance to the sleeve 110 which is sufficiently small so that the support faces 120,122 engages the sleeve 110 if there is misalignment which is greater than a pre-determined desirable value. As illustrated in Figs 3 and 4, the support faces 120,122 can be located below the internal profile 103. Optionally one or both support faces 120,122 can be provided in or as part of the profile 103, or above the profile 103. With the wellhead assembly 100 arranged as illustrated in Fig. 4, further drilling can be carried out to install well pipes in the well. These well pipes can then be cemented in place. When injecting cement between the to-be-installed well pipe and the open formation, the cement will proceed up to the bottom end 113 of the sleeve 110, from which point it will proceed substantially entirely inside the sleeve 110 up to the receptacle 103, where the cement can flow out of the cement port(s) 106 and be handled appropriately. With the wellhead assembly 100, problems with cement control due to soft soils at and immediately below the seabed 130 can be reduced or eliminated. This provides for lower cement losses and / or reduced risk of problems associated with return cement flowing out below or around the foundations 101. With the wellhead assembly 100, the installation of the sleeve 110 into the seabed 130 and subsoil can be done in a reliable manner, compared to for example having a tail pipe or washout sleeve fixed and extending downwardly from the foundation 101 as the foundation is landed on the seabed 130. Lowering of the sleeve 110 can be carried out in a controlled manner, and supported by for example jetting or drilling immediately below the sleeve 110 as it is being lowered. After the sleeve 110 reaches the second position, it can remain in place over the life of the associated hydrocarbon well. Continued construction and operation of the well can be done through the sleeve 110. In any of the examples or embodiments described or claimed here, the sleeve 110 may, in the first position, extend upwardly from the receptacle 102. A majority portion of the sleeve 110 may be located above the internal profile 103 in the first position. For example, more than 50%, more than 60% or more than 70% of the longitudinal length of the sleeve 110 may be located above the internal profile 103 and / or the receptacle 102 when in the first position. Installing the wellhead assembly 100 at the seabed 130 may comprise providing the sleeve 110 pre-installed in the foundation 101 and lowering the foundation 101 to the seabed 130 with the sleeve 110 temporarily fixed at the foundation 101. The sleeve 110 may be fixed in a first position, in which the sleeve 110 extends upwardly from the receptacle 102. Advantageously, the foundation 101 is installed with the sleeve 110 in a position whereby the sleeve 110 remains spaced from the seabed 130 until the foundation 101 has been installed. Subsequent to installing the foundation 101, the sleeve 110 can be moved into the seabed 130. Providing the bottom end 113 of the sleeve 110 above the seabed 130 during landing and / or installation of the foundation 101 reduces risk of operational problems during installation. The foundation 101 may, for example, be landed and installed (which may include anchoring the foundation 101 to the seabed 130, e.g. via suction buckets, piles or other means) with the bottom end 113 spaced from the seabed 130. After installation of the foundation 101, the sleeve(s) 110 may be moved (e.g., driven) into the seabed 130 in a controlled manner, for example using jetting or drilling, as described above. Well construction equipment in the form of a sea bed removal tool, such as a drilling tool or a jetting tool, can be used to install the sleeve 110. Particularly, the sleeve 110 can be moved into the seabed 130 by driving the sea bed removal tool through the sleeve 110. The sea bed removal tool may create a bore for the sleeve 110 to be moved (i.e., lowered) into. Advantageously, the sleeve 110 may be installed by concurrently driving the sea bed removal tool into the seabed 130 through the sleeve 110 and moving the sleeve 110 into the seabed 130. The sea bed removal tool may, for example, be positioned such that it extends through the sleeve 110 and with a drilling or jetting head at or immediately below the lower end 113, and the sleeve 110 and sea bed removal tool may be lowered together into the bore created by the sea bed removal tool. This may provide a controlled installation of the sleeve 110, with low risk of wash-out or collapse of the bore. With the sleeve 110 installed, i.e. statically positioned in the seabed 130 and extending downward from the foundation 101, a sea bed removal tool may be driven into the seabed 130 through the sleeve 110 to produce a borehole for the well pipe 201. The sea bed removal tool may be the same sea bed removal tool as described above, or a different one. After producing the borehole for the well pipe 201, the well pipe 201 is lowered into the borehole through the sleeve 110. The well pipe 201 may then be cemented in place inside the sleeve 110 and extend downwardly from the sleeve 110 into the seabed 130. The skilled reader will appreciate that the well pipe 201 may have a length which is considerably greater than that of the sleeve 110. The sleeve 110 may, for example, have a length of 2-10 m. The well pipe 201 may have a length which is one order of magnitude higher or more. The well pipe 201 may have a housing at a top end part thereof, such as a conductor housing or wellhead housing, which is landed and locked in the receptacle 102. Alternatively, the sleeve 110 may comprise an internal profile for holding the well pipe housing, such that the well pipe 201 can be landed and locked in the internal profile of the sleeve 110. The following numbered clauses outline further inventive examples and embodiments. A1. A wellhead assembly (100) comprising: a foundation (101) having at least one well slot (200); the at least one well slot (200) comprising a receptacle (102) having an internal profile (103) for holding a well pipe (201); a sleeve (110) arranged in the receptacle (102); wherein the sleeve (110) is vertically movable and has a top end (111) which in a first position of the sleeve (110) is located above the internal profile (103) and in a second position of the sleeve (110) is located below the internal profile (103). A2.The wellhead assembly (100) of any preceding clause, comprising a sleeve lock mechanism (104,120) operable to lock the sleeve (110) such as to prevent longitudinal movement of the sleeve (110) relative to the receptacle (102) when the sleeve (110) is in the second position. A3. The wellhead assembly (100) of any preceding clause, wherein the sleeve lock mechanism (104,120) is arranged to automatically engage and lock the sleeve (110) relative to the receptacle (102) when the sleeve (110) reaches the second position when moved from the first position. A4.The wellhead assembly (100) of any preceding clause, wherein the sleeve (110) has a sleeve lock member (104) at a top end part (112) of the sleeve (110), the sleeve lock member (104) configured to engage a lock face (120) arranged below the internal profile (103) in the receptacle (102), or the receptacle (102) has a sleeve lock member arranged below the internal profile (103) in the receptacle (102) and configured to engage a lock face arranged at the top end part (112) of the sleeve (110). A5.The wellhead assembly (100) of any preceding clause comprising a vertical lock (105) operable to temporarily hold the sleeve (110) fixed in the first position. A6.The wellhead assembly (100) of any preceding clause, wherein the vertical lock (105) has an interface (105a) via which the vertical lock (105) can be released such as to release the sleeve (110). A7.The wellhead assembly (100) of any preceding clause, wherein the receptacle (102) comprises two vertically spaced support faces (120,122) for alignment of the sleeve (110). A8.The wellhead assembly (100) of any preceding clause, wherein the support faces (120,122) are located below the internal profile (103). A9.The wellhead assembly (100) of any preceding clause, wherein, in the first position, a bottom end (113) of the sleeve (110) is located inside the receptacle (102), or below the receptacle (102) and configured to be or being above a seabed (130) on which the foundation (101) is supported when the foundation (101) is in an installed position. A10. The wellhead assembly (100) of any preceding clause, wherein the receptacle (102) comprises at least one cement port (106) and the top end (111) in the second position of the sleeve (110) is located below the at least one cement port (106). A11. The wellhead assembly (100) of any preceding clause, wherein, in the first position, a majority portion of the sleeve (110) is located above the internal profile (103), for example wherein more than 50%, more than 60% or more than 70% of a length of the sleeve (110) is located above the internal profile (103). A12. The wellhead assembly (100) of any preceding clause, wherein the foundation (101) comprises at least two well slots (200). A13. The wellhead assembly (100) of any preceding clause, wherein the foundation (102) is arranged on the sea floor (130) and the well pipe (201) is cemented in place inside the sleeve (110). A14. The wellhead assembly (100) of any preceding clause, wherein the well pipe (201) comprises a well pipe housing which is landed in and locked at the internal profile (103). A15. The wellhead assembly (100) of any preceding clause, wherein the well pipe (201) is a high pressure pipe. A16. The wellhead assembly (100) of any preceding clause, wherein a length of the sleeve (110) is less than 10 metre, for example wherein the length of the sleeve (110) is between 2 metre and 10 metre. A17. The wellhead assembly (100) of any preceding clause, wherein the well pipe (201) comprises a low pressure pipe having a housing landed and locked in the receptacle (110) and a high pressure pipe having a housing landed and locked in the housing of the low pressure pipe. A18. The wellhead assembly (100) of any preceding clause, wherein the sleeve (110) comprises an internal profile for holding a housing of the well pipe (201). A19. A method of installing a wellhead assembly (100) at a seabed (130), the method comprising: positioning a foundation (101) at the seabed (130), the foundation having at least one well slot (200); providing a sleeve (110); bringing the sleeve (110) into the seabed (130) at the at least one well slot (200); lowering a well pipe (201) through the sleeve (110) and into the seabed (130); and cementing the well pipe (201) in place inside the sleeve (110). A20. The method of any preceding clause, the method comprising driving a sea bed removal tool, such as a drilling tool or a jetting tool, into the seabed (130) through the sleeve (110). A21. The method of any preceding clause, the method comprising concurrently driving the sea bed removal tool into the seabed (130) through the sleeve (110), such as drilling or jetting through the sleeve (110), and moving the sleeve (110) into the seabed (130). A22. The method of any preceding clause, wherein the step of driving the sea bed removal tool into the seabed (130) through the sleeve (110) comprises creating a borehole for the sleeve (110), and the step of moving the sleeve (110) into the seabed (130) comprises moving the sleeve (110) into the borehole. A23. The method of any preceding clause, the method comprising, with the sleeve (110) statically positioned in the seabed (130), driving the sea bed removal tool into the seabed (130) through the sleeve (110) to produce a borehole for the well pipe (201), and subsequent to producing the borehole for the well pipe (201), carrying out the step of lowering the well pipe (201) through the sleeve (110) and into the seabed (130), whereby the well pipe (201) is lowered into the borehole through the sleeve (110). A24. The method of any preceding clause, wherein the foundation (101) comprises a receptacle (102) positioned in the at least one well slot (200), the receptacle (102) having an internal profile (103) for holding a housing of the well pipe (201), and wherein the step of bringing the sleeve (110) into the seabed (130) comprises: moving the sleeve (110) from a first position in which the sleeve (110) is positioned in and extending upwardly from the receptacle (102) to a second position in which a top end (111) of the sleeve (110) is located below the internal profile (103). A25. The method of any preceding clause, wherein the step of positioning the foundation (101) at the seabed (130) comprises lowering the foundation (101) to the seabed (130) with the sleeve (110) temporarily fixed in the first position. A26. The method of any preceding clause, wherein sleeve (110) in the first position is spaced from the seabed (130) and the step of moving the sleeve (110) to the second position comprises moving the sleeve (110) into the seabed (130). A27. The method of any preceding clause, wherein the step of positioning the foundation (101) at the seabed (130) comprises landing the foundation (101) at the seabed (130) with a bottom end (113) of the sleeve (110) spaced from and located above the seabed (130), and wherein the method comprises subsequent to the step of positioning the foundation (101) at the seabed (130), moving the sleeve (110) into the seabed (130). A28. The method of any preceding clause, wherein, in the first position, a majority portion of the sleeve (110) is located above the internal profile (103), for example wherein more than 50%, more than 60% or more than 70% of a length of the sleeve (110) is located above the internal profile (103). A29. The method of any preceding clause, wherein the foundation (101) comprises at least two well slots (200). A30. The method of any preceding clause, comprising locking the sleeve (110) in the second position by means of a sleeve lock mechanism (104,120). A31. The method of any preceding clause, wherein the well pipe (201) is a high pressure pipe. A32. The method of any preceding clause, wherein the well pipe (201) comprises a low pressure pipe having a low pressure pipe housing and a high pressure pipe having a high pressure pipe housing, and the method comprises: landing and locking the low pressure pipe housing in the receptacle (110) and landing and locking the high pressure pipe housing in the low pressure pipe housing. A33. The method of any preceding clause, wherein the step of cementing the well pipe (201) in place inside the sleeve (110) comprises pumping cement into the well pipe (201), and leading a return cement flow through an annulus between the sleeve (110) and the well pipe (201) and out of at least one cement port (106) of the receptacle (102). A34. The method of any preceding clause, wherein the sleeve (110) comprises an internal profile for holding a housing of the well pipe (201), and the method comprises landing the well pipe (201) in the internal profile of the sleeve (110).

Claims

1. A wellhead assembly (100) comprising:a foundation (101) having at least one well slot (200);the at least one well slot (200) comprising a receptacle (102) having an internal profile (103) for holding a well pipe (201);a sleeve (110) arranged in the receptacle (102);wherein the sleeve (110) is vertically movable and has a top end (111) which in a first position of the sleeve (110) is located above the internal profile (103) and in a second position of the sleeve (110) is located below the internal profile (103).

2. The wellhead assembly (100) of claim 1, comprisinga sleeve lock mechanism (104,120) operable to lock the sleeve (110) such as to prevent longitudinal movement of the sleeve (110) relative to the receptacle (102) when the sleeve (110) is in the second position.

3. The wellhead assembly (100) of claim 2, wherein the sleeve lock mechanism (104,120) is arranged to automatically engage and lock the sleeve (110) relative to the receptacle (102) when the sleeve (110) reaches the second position when moved from the first position.

4. The wellhead assembly (100) of any preceding claim comprising a vertical lock (105) operable to temporarily hold the sleeve (110) fixed in the first position.

5. The wellhead assembly (100) of claim 4, wherein the vertical lock (105) has an interface (105a) via which the vertical lock (105) can be released such as to release the sleeve (110).

6. The wellhead assembly (100) of any preceding claim, wherein the receptacle (102) comprises two vertically spaced support faces (120,122) for alignment of the sleeve (110).

7. The wellhead assembly (100) of claim 6, wherein the support faces (120,122) are located below the internal profile (103).

8. The wellhead assembly (100) of any preceding claim, wherein, in the first position, a bottom end (113) of the sleeve (110) is locatedinside the receptacle (102), orbelow the receptacle (102) and configured to be or being above a seabed (130) on which the foundation (101) is supported when the foundation (101) is in an installed position.

9. The wellhead assembly (100) of any preceding claim, wherein the receptacle (102) comprises at least one cement port (106) and the top end (111) in the second position of the sleeve (110) is located below the at least one cement port (106).

10. The wellhead assembly (100) of any preceding claim, wherein, in the first position, a majority portion of the sleeve (110) is located above the internal profile (103).

11. A method of installing a wellhead assembly (100) at a seabed (130), the method comprising:positioning a foundation (101) at the seabed (130), the foundation having at least one well slot (200);providing a sleeve (110);bringing the sleeve (110) into the seabed (130) at the at least one well slot (200);lowering a well pipe (201) through the sleeve (110) and into the seabed (130); andcementing the well pipe (201) in place inside the sleeve (110).

12. The method of claim 11, the method comprising concurrently driving a sea bed removal tool into the seabed (130) through the sleeve (110) and moving the sleeve (110) into the seabed (130).

13. The method of claim 11 or 12, wherein the foundation (101) comprises a receptacle (102) positioned in the at least one well slot (200), the receptacle (102) having an internal profile (103) for holding a housing of the well pipe (201), and wherein the step of bringing the sleeve (110) into the seabed (130) comprises:moving the sleeve (110) from a first position in which the sleeve (110) is positioned in and extending upwardly from the receptacle (102) to a second position in which a top end (111) of the sleeve (110) is located below the internal profile (103).

14. The method of claim 13, wherein the step of positioning the foundation (101) at the seabed (130) comprises lowering the foundation (101) to the seabed (130) with the sleeve (110) temporarily fixed in the first position.

15. The method of claim 13 or 14, comprising locking the sleeve (110) in the second position by means of a sleeve lock mechanism (104,120).

16. The method of any of claims 11-15, whereinthe step of positioning the foundation (101) at the seabed (130) comprises landing the foundation (101) at the seabed (130) with a bottom end (113) of the sleeve (110) spaced from and located above the seabed (130), and wherein the method comprisessubsequent to the step of positioning the foundation (101) at the seabed (130), moving the sleeve (110) into the seabed (130).

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