Abstract
The invention relates to a subsea wellhead support system (1) comprising: —a foundation assembly (2); —a conductor housing (31) for supporting a wellhead (4); —a connection arrangement (5) between the foundation assembly (2) and the conductor housing (3′); wherein the connection arrangement (5) is configured to releasably connect the conductor housing (3′) to the foundation assembly (2), such that: —during installation of the subsea wellhead support system (1), the conductor housing (1) can be fixed relative the foundation assembly (2), and—after installation of the subsea wellhead support system (1), the connection arrangement (5) can be released from the foundation assembly (2) allowing the conductor housing (3′) to move parallel along a longitudinal direction of a throughgoing opening of the conductor housing (31).
Claims
1. A subsea wellhead support system comprising: a foundation assembly; a conductor housing for supporting a wellhead; and a connection arrangement between the foundation assembly and the conductor housing; wherein the connection arrangement is configured to releasably connect the conductor housing to the foundation assembly, such that, during installation of the subsea wellhead support system, the conductor housing can be fixed relative the foundation assembly, and after installation of the subsea wellhead support system, the connection arrangement can be released from the foundation assembly allowing to allow the conductor housing to move parallel along a longitudinal direction of a through-going opening of the conductor housing.
2. The subsea system according to claim 1, wherein the foundation assembly comprises a suction anchor.
3. The subsea system according to claim 1, wherein the foundation assembly comprises a well template structure having at least one well slot and a number of suction anchors.
4. The subsea system according to claim 1, further comprising a conductor extension which is fixedly connected to the conductor housing.
5. The subsea system according to claim 1, further comprising a fluid-tight cap covering a cross section of the conductor housing.
6. The subsea system according to claim 1, further comprising a guide pipe fixedly connected to the foundation assembly, wherein the conductor housing is arranged radially inside the guide pipe.
7. The subsea system according to claim 6, further comprising a conductor extension which is fixedly connected to the conductor housing.
8. The subsea system according to claim 2, wherein the conductor housing is arranged inside a periphery of the of the suction anchor.
9. The subsea system according to claim 2, wherein the connection arrangement is configured to provide a fluid tight seal between the suction anchor and the conductor housing.
10. The subsea system according to claim 1, wherein the connection arrangement comprises a safety device configured to fail when subjected to a force above a predetermined force to thereby release the conductor housing from the foundation assembly.
11. The subsea system according to claim 1, wherein the connection arrangement comprises a lock operable by an ROV after installation of the subsea system.
12. The subsea system according to claim 2, further comprising a pump arrangement comprising at least one pump configured to create an underpressure in an inner volume formed by a surface of a seabed, a side portion of the suction anchor and a top portion of the suction anchor relative to a surrounding pressure.
13. The subsea system according to claim 2, wherein the conductor housing is arranged radially outside a periphery of the suction anchor.
14. A method of installing a subsea support system comprising: a foundation assembly; a conductor housing for supporting a wellhead; and a connection arrangement between the foundation assembly and the conductor housing; wherein the method comprises the steps of: prior to installing the subsea support system subsea, releasably connecting the conductor housing to the foundation assembly using the connection arrangement, thereby fixing the conductor housing relative the foundation assembly; installing the subsea support system subsea a single run; after installation of the subsea wellhead support system, releasing the connection arrangement so as to release the conductor housing from the foundation assembly, thereby allowing parallel movement of the conductor housing along a longitudinal direction of a through-going opening of the conductor housing.
15. The method according to claim 14, wherein the step of releasing the connection arrangement comprises operating a Remotely Operated Vehicle to release the conductor housing from the foundation assembly.
16. The method according to claim 15, wherein the step of releasably connecting the conductor housing to the foundation assembly comprises selecting a connection force of the connection arrangement which is above a maximum expected force occurring during the installation and below a median of expected force of a well-growth during production of a well extending through the conductor housing.
17. The method according to claim 16, wherein the connection arrangement comprises shear element(s) which break at predetermined shear forces, and wherein the method comprises selecting a type and/or number of shear element(s) based on said maximum expected installation forces and the median expected well-growth forces.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0064] FIG. 1A shows a foundation structure in the form of a suction anchor, with a conductor housing inside the suction anchor;
[0065] FIG. 1B is a similar view as FIG. 1A, but with the addition of a conductor extension connected to the conductor housing;
[0066] FIG. 1C is a simplified sketch of a foundation assembly in the form of a well template;
[0067] FIG. 1D shows a foundation structure in the form of a suction anchor with a guide pipe installed therein, where a conductor housing is arranged inside the guide pipe;
[0068] FIG. 1E shows a foundation structure in the form of a suction anchor with a guide pipe installed therein, where a conductor housing with a conductor extension is arranged inside the guide pipe;
[0069] FIGS. 2A and 2B are perspective side view of cylindrical suction anchors with a circular cross section where the conductor housing is arranged inside the suction anchor;
[0070] FIGS. 3A and 3B are perspective side view of cylindrical suction anchors with a circular cross section where the conductor housing(s) is arranged radially outside the periphery of the suction anchor;
[0071] FIGS. 4A-4C show different examples of cylindrical foundation assemblies, where FIG. 4A shows a cylindrical foundation with a rectangular/quadratic cross section, FIG. 4B shows a cylindrical foundation with a triangular cross section, and FIG. 4C shows a cylindrical foundation with a pentagonal cross section;
[0072] FIG. 5A shows a possible setup of a subsea wellhead support system when used in a foundation assembly in the form of a well template;
[0073] FIG. 5B shows a sectional view in a vertical plane of FIG. 5A after installation of the conductor housing and when the contingency lock(s) has been removed;
[0074] FIG. 6A shows a similar solution as in FIGS. 5A and 5B without a conductor extension;
[0075] FIG. 6B is a detailed view of section S in FIG. 6A;
DETAILED DESCRIPTION OF THE INVENTION
[0076] In the following, embodiments of the invention will be discussed in more detail with reference to the appended drawings. It should be understood, however, that the drawings are not intended to limit the invention to the subject-matter depicted in the drawings. Furthermore, even if some of the features are described in relation to the subsea wellhead support system only, it is apparent that they are valid for the related method as well, and vice versa. Hence, any features described in relation to the method only are also valid for the subsea wellhead support system.
[0077] It is clear that the subsea wellhead support system may comprise additional elements not mentioned specifically or disclosed in the figures.
[0078] FIG. 1A shows a foundation structure in the form of a suction anchor, with a conductor housing inside the suction anchor 2′. A Subsea wellhead support system 1 comprising a foundation assembly 2 in the form of a suction anchor 2′. It is further disclosed a conductor housing 3′. The conductor housing 3′ supports a wellhead 4. The wellhead 4 is arranged radially inside the conductor housing 3′. A connection arrangement 5 is arranged between the suction anchor 2′ and the conductor housing 3′. The connection arrangement 5 is configured to releasably connect the conductor housing 3′ to the suction anchor 2′ such that during installation of the subsea wellhead support system 1, the conductor housing (3′) can be fixed relative the foundation assembly (2), and after installation of the subsea wellhead support system 1, the connection arrangement 5 can be released from the suction anchor 2 allowing the conductor housing 3′ to move parallel along a longitudinal direction of a through-going opening of the conductor housing 3′ as indicated by two-way arrow A. I.e. in other words, after installation and disconnection of the connection arrangement 5 locking the conductor housing to the suction anchor 2′, the conductor housing 3′ is allowed to move relative the suction anchor 2′ in the vertical, or mainly vertical, direction indicated by the two-way arrow A.
[0079] The suction anchors would be equipped with standard equipment for setting suction anchor, for example suction pumps, installation hatch for water displacement. These features will be known to the skilled person and will not be further described herein.
[0080] A pump arrangement 6 comprising one or more pumps may be arranged in an upper part of the suction anchor 2′ in order to provide for the possibility of sucking fluids from an inside of the suction anchor 2′ to an outside of the suction anchor 2′ thereby creating negative pressure inside the suction anchor 2′ relative to the outside of the suction anchor thus assisting in penetration of the suction anchor 2′ into the soil. The suction anchor 2′ comprises sidewalls (i.e. “skirt) and top cover with an opening fit for receiving conductor housing 3′ etc.
[0081] During installation of the system of FIG. 1A, i.e. a system without a conductor extension, it is required to seal the cross section of the conductor housing 3′ in order to be able to create the required underpressure or negative pressure for suction of the suction anchor 2′ into the seabed or soil. This cross section seal may be a fluid-tight cap covering a cross section of the conductor housing 3′.
[0082] FIG. 1B is a similar view as FIG. 1A, but with the addition of a conductor extension connected to the conductor housing. In FIG. 1B, the conductor extension 3” has the same length as the skirt (i.e. the part of the suction anchor penetrating the soil) of the suction anchor 2′. Although it is shown that the length of the conductor extension 3″ is equal to the length of the skirt, the skilled person will understand that the conductor extension 3″ can also be shorter or longer than the length of the skirt of the suction anchor 2′, such that the conductor extension 3″ may penetrate the soil shallower, deeper or the same length as the skirt of the suction anchor 2′.
[0083] Contrary to the system of FIG. 1A, the presence of the conductor extension 3″ in FIG. 1B renders the fluid-tight cap covering the cross section of the conductor housing 3′ superfluous. This is because the conductor housing 3′ and the conductor extension extend a sufficient length relative the skirt of the suction anchor 2′ thereby creating a closed volume between an outside of the conductor assembly (i.e. the combination of conductor housing 3′ and conductor extension 3″) and the inner surface of the suction anchor (i.e. top cover of suction anchor 2′ and sidewall/skirt of suction anchor 2′).
[0084] FIG. 1C is a simplified sketch of a foundation assembly 2 in the form of a well template 2″. The well template 2″ is discloses with a total of eight well slots 8 arranged in two parallel rows in the well template 2″. Each well slot 8 leads to one individual well. Each of the well slots 8 is disclosed with a conductor housing 3′ supporting a wellhead 4. A connection arrangement 5 connects the conductor housing 3′ (and possibly a conductor extension 3″ (not shown inn FIG. 1C)) during installation is configured to releasably connect the conductor housing 3′ to the foundation assembly 2, such that during installation of the subsea wellhead support system 1, the conductor housing 1 can be fixed relative the foundation assembly 2, and after installation of the subsea wellhead support system 1, the connection arrangement 5 can be released from the foundation assembly 2 allowing the conductor housing 3′ to move parallel along a longitudinal direction of a through-going opening of the conductor housing 3′.
[0085] FIG. 1D shows a foundation structure in the form of a suction anchor 2′ with a guide pipe 7 installed therein, where the conductor housing 3′ is arranged inside the guide pipe 7. The guide pipe 7 is fixedly connected to the suction anchor 2′. The conductor housing 3′ is arranged radially inside the guide pipe 7. The length of the guide pipe 7 is shown as being equal to the skirt of the suction anchor 2′, but it can also be shorter or longer than the length of the skirt of the suction anchor 2′. As such, the guide pipe 7 may penetrate shallower, deeper or the same length as the skirt of the suction anchor 2′. In the embodiment of FIG. 1D, the connection arrangement 5 is arranged between the guide pipe 7 and the conductor housing 3′. The remaining features are similar as the embodiment in FIG. 1A.
[0086] FIG. 1E shows a foundation structure in the form of a suction anchor with a guide pipe installed therein, where a conductor housing with a conductor extension 3″ is arranged inside the guide pipe 7. The remaining features are similar as in the embodiment of FIG. 1D and will not be repeated.
[0087] FIGS. 2A and 2B are perspective side views of cylindrical suction anchors 2′ with a circular cross section where the conductor housing 3′ is arranged inside (e.g. as disclosed in the center) the suction anchor 2′. The only difference between the figures being that in FIG. 2B the conductor housing 3′ is connected to a conductor extension 3′. The other components which may form part of the system, such as the connection arrangement, guide pipe, pump arrangement, top cover etc. are omitted from FIGS. 2A and 2B to better illustrate the different possible positions of the conductor housing relative the suction anchor 2′.
[0088] FIGS. 3A and 3B are perspective side views of cylindrical suction anchors 2′ with a circular cross section where the conductor housing(s) 3′ is arranged radially outside the horizontal extent of the suction anchor 2′. The other components which may form part of the system, such as the connection arrangement, guide pipe, pump arrangement, top cover etc. are omitted from FIGS. 2A and 3B to better illustrate the different possible positions of the conductor housing relative the suction anchor 2′. There may be one conductor housing (e.g. as shown in FIG. 3A) or two or more conductor housings 3′ (e.g. for example three conductor housings as illustrated in FIG. 3B) radially outside the horizontal extent of the suction anchor 2′. Although not disclosed, in the figures, if there are more than one conductor housing 3′ there may be at least one conductor housing inside the suction anchor 2′ and at least one conductor housing 3′ outside the horizontal extent of the suction anchor 2′.
[0089] FIGS. 4A-4C show different examples of differently shaped cylindrical foundation assemblies, where FIG. 4A shows a cylindrical foundation with a rectangular/quadratic cross section, FIG. 4B shows a cylindrical foundation with a triangular cross section, and FIG. 4C shows a cylindrical foundation with a pentagonal cross section.
[0090] FIG. 5A shows a possible setup of a subsea wellhead support system 1 when used in a foundation assembly in the form of a well template 2″. A connection arrangement 5 comprising one or more weak link bolt(s) 8 securing a locking ring 9 to the well template 2″ is disclosed. The connection arrangement 5 may have two functions, including fixing the conductor housing 3′ to the well template 2″ during installation, as well as preventing uplift during cement operations (e.g. cementing of any guide pipe or other pipe to be cemented). The system may further comprise a contingency lock 10 to additionally secure the locking ring to the well template 2″ during cementing operation(s).
[0091] After installation (and any cementing operation(s)), the contingency lock 10 is removed. This may be performed using ROV or other suitable means. The weak link(s) 8 are dimensioned such that they tear off when subject to forces created by well growth.
[0092] FIG. 5B shows a sectional view in a vertical plane of FIG. 5A after installation of the conductor housing 3′ and when the contingency lock(s) 10 has been removed. As is seen from the FIG. 5B. Vertical pins 11 fastened to the well template 2″ may be provided with an end stop 12 that may allow for some well growth, for example in the magnitude of +−100 mm.
[0093] FIG. 6A shows a similar solution as in FIGS. 5A and 5B without a conductor extension 3″. In order to create a closed volume inside the suction anchor 2′ during installation, a fluid tight end cap 13 covers the cross section of the conductor housing 3′ during installation. After installation, the end cap 13 is removed.
[0094] FIG. 6B is a detailed view of section S in FIG. 6A.
[0095] The invention is now explained with reference to non-limiting embodiments. However, a skilled person will understand that there may be made alternations and modifications to the embodiment that are within the scope of the invention as defined in the attached claims.
REFERENCE NUMERALS
[0096]
TABLE-US-00001 1 Subsea wellhead support system 2 Foundation assembly .sub. 2′ Foundation assembly, suction anchor .sub. 2″ Foundation assembly, well template 3 Conductor assembly .sub. 3′ Conductor housing .sub. 3″ Conductor extension 4 wellhead 5 Connection arrangement 6 Pump arrangement 7 Guide pipe 8 Well slot 9 Weak link bolt 10 Contingency lock 11 Vertical pin 12 End stop of vertical pin 13 Fluid tight cap A Arrow S Section
