Assembly

Abstract

An assembly is provided for connecting a well head system to a subsea foundation structure, the assembly comprising a first component and a second component The first component has a first opening and the second component has a second opening, which is configured for insertion of a wellhead system therethrough. The second component comprises a recess for receiving at least part of the first component therein, wherein the second component comprises a housing portion that is configured to extend away from the first component, when the first component has been received in the recess of the second component. The assembly may comprise a third component that is arranged to in use be located between at least part of the first component and / or second component and at least part of the wellhead system.

Description

[0001] ASSEMBLY

[0002] Technical Field

[0003] The present invention concerns an assembly for connecting a well head system to a subsea foundation structure and a method of connecting a wellhead system to a subsea foundation via a connecting assembly.

[0004] It is known that the exploration, and the production, or extraction, of hydrocarbons from susbsea sources typically involves the use of a well, comprising one or more pipes that penetrate the seabed, with a wellhead system (which may be referred to, for brevity, simply as a ‘wellhead’) at its / their upper end, which is configured to connect to external structures such as a rig or riser. The pipe(s) and wellhead are physically supported by a foundation structure, which may take the form of an anchor, mat, or pile. The role of the foundation structure is typically to maintain the position of the well, relative to the seabed, and to absorb and / or dissipate at least some of the forces that the components of the well are subjected to.

[0005] One known type of subsea structure, which forms the foundation and support of a subsea well for exploration and hydrocarbon production, is a suction anchor. Suction anchors are known and are described, for example, in “Suction Anchor Foundation", disclosed by Equinor Energy AS, Research Disclosure database number 666004, published in the October 2019 paper journal. For ease of reference, an example suction anchor is described briefly below. But the invention described herein is not limited to use with suction anchors.

[0006] A suction anchor 100 (as shown in Figure 1 for example) is a device that forms a closed volume with the sea bed (or whichever surface it is to be sucked into) and in which the pressure can be adjusted so that it can be moved relative to the seabed. This is achieved by reducing the pressure inside the suction anchor 100 to be less than the external sea pressure at the depth at which the suction anchor is located. This causes the suction anchor 100 to be sucked / pushed into the sea bed by the pressure differential created. Conversely, if it is desired to uninstall / retrieve the suction anchor 100, this may be achieved by increasing the pressure inside the suction anchor 100 to be greater than the external sea pressure at the depth at which the suction anchor 100 is located, so that the suction anchor 100 is forced out of the sea bed by the pressure differential created. As shown in Figure 2, the closed annular volume (suction chamber 102) is bounded by an outer suction skirt 104, a top plate 106 that forms an annular connection portion, and a central pipe 108 of the suction anchor 100.

[0007] The central pipe 108 is connected to the top plate 106 via an inner pipe support ring 110, which itself is part of, or connects to, a conductor housing receptacle 123 (described further below). This is a pressure tight connection (e.g. formed by welding) so as to create the sealed internal volume.

[0008] The central pipe 108 is about the same length or slightly shorter than the length of the suction skirt 104. At the bottom of the central pipe 108 is a tail pipe 112. Distance markings 114 may be provided on the outer suction skirt 104 and / or the tail pipe 112. These markings 114 may be used during installation so that it can be ascertained how deep the foundation has penetrated the seabed.

[0009] When the suction anchor 100 is placed on the sea bed, the suction anchor 100 will generally self-penetrate a certain depth into the sea bed (the exact depth depending on factors such as the weight of the suction anchor and the geology of the sea bed) such that the tail pipe 112, central pipe 108, and outer suction skirt 104 form the closed sealed volume in which the pressure can be adjusted. This can be checked using the distance markings.

[0010] Once the suction anchor 100 is sealed against the seabed, the pressure therein can be reduced by connecting ventilation hatches (which may also be referred to as pump ports) in the top plate 106 to a pump which can remove air, water and / or soil from inside the internal annular volume to reduce the pressure.

[0011] The suction anchor 100 is used as a foundation and support for a subsea well. The suction anchor 100 provides a load path for forces to be transmitted from the structure itself and the subsea well (and the components mounted on the subsea well, such as but not limited to a Blowout Preventer (BOP)) or Xmas Tree into the sea bed. As the skilled reader will know, the term ‘Xmas Tree’, in this context is used to describe an assembly of several valves, which normally is placed on top of the wellhead (system). These valves represent the main controllable barriers of the well. They are used to control the well stream (for example, turning it on and off) and also to ensure access for monitoring the well, circulating various types of fluid / gas to and from the well. The subsea well extends through the centre of the suction anchor 100, via the central pipe 108.

[0012] There is a high pressure wellhead 116, which is shown in Figure 3, which connects to the central pipe 108 of the suction anchor 100. The high pressure wellhead 116 is shown mounted in a conductor housing 118 (which may also be referred to as a low-pressure housing) that in turn is mounted within a cylindrical conductor housing receptacle 123. Alternatively, the conductor housing 118 may be omitted.

[0013] The conductor housing receptacle 123 comprises a cylindrical collar 120, which is configured to surround at least part of the wellhead system, when it is inserted for connection to the subsea foundation structure. The conductor housing receptacle 123 further incudes a receptacle support ring 124, which extends substantially laterally / radially outwards from the top of the collar 120, and the inner pipe support ring 110, which extends substantially laterally / radially inwards from the bottom of the collar 120. The inner pipe support ring 110 includes a portion that serves to support the central pipe 108.

[0014] The conductor housing receptacle 123 is welded (or otherwise fixed) to the suction anchor 100 via a top frame 121. The top frame 121 is - in the arrangement shown in Figures 1 to 3 - made up of a plurality of radially extending I-beams 122, for example but not limited to eight I-beams 122.

[0015] The I-beams 122 are welded along the length of their bottom surface to the top plate 106 of the suction anchor 100. These I-beams 122 have the purpose of both 1) strengthening the annular top plate 106 against imploding or exploding when the pressure is reduced or raised in the internal annular volume of the suction anchor 100 and 2) providing a load path through which loads exerted on the wellhead can be transferred into the remainder of the foundation, e.g. suction anchor 100, before ultimately being transferred into the seabed. End plates are provided at the distal ends of each I-beam. On top of the top frame 121 are a plurality of guidepost supports 126. These are small stubs to which guideposts may be mounted and secured. The guideposts may be connected to guide wires that run from a vessel at the surface.

[0016] As discussed above, the conductor housing 118 is shown in this example as being located within the conductor housing receptacle 123. It is connected to it at its lower end via an adaptor ring 128 that is supported on the inner pipe support ring 110. The use of an adaptor ring 128 allows the suction anchor 100 to be used with different sizes and geometry of conductor housings 118 that may be provided by different suppliers. This, in turn, allows the suction anchor foundation to be used with different-wellhead systems from different manufacturers and different equipment mounted on the high-pressure wellhead housing

[0017] The upper end of the conductor housing 118 is locked into the conductor housing receptacle 123 using a flange ring 130. A (radially inward) surface of the flange ring 130 engages with a shoulder on the outer surface of the conductor housing 118. At least part of the flange ring 130 rests on top of, and therefore overlaps, the receptacle support ring 124. The flange ring 130 is bolted onto the receptacle support ring 124, which forms an upper end of the conductor housing receptacle 123, which is turn is connected (such as welded) to the top frame 121 of the suction anchor structure.

[0018] The adaptor ring 128 and the conductor housing receptacle 123 provide a load transmitting connection between the conductor housing 118 and the remainder of the suction anchor foundation.

[0019] The suction anchor may be installed in the seabed (or other location) by any suitable process, and so the installation is not described herein.

[0020] Once the suction anchor has been suitably installed, wellhead valves, such as a blowout preventer (BOP) and / or Xmas tree etc, may be connected to and mounted on top of the wellhead. As described above, it may be guided by guideposts and guide wires extending from the guidepost supports. Additionally, or alternatively, the foundation and / or the wellhead valve may be provided with a large guide funnel and / or lead in stab that are used to guide the wellhead valve onto the wellhead housing. With such funnels, the guideposts may not be needed and thus these and the corresponding guideposts supports may be omitted. The wellhead valve is mounted directly onto the high-pressure wellhead housing. Additionally, the wellhead valve may be connected to other parts of the assembly other than the high-pressure wellhead housing. For example, there may be a connection between the wellhead valve and the pad-eyes.

[0021] The installed well may be an exploration and / or a production well. The well may be used for exploration but the well may be converted to a production well. Hence the well may be a so- called ‘keeper well’.

[0022] It will be appreciated that significant loads will be experienced by a wellhead system, for example during drilling, and for example due to the size and weight of components that will be connected to it for use. It is desirable to transfer loads from a wellhead system into the surrounding foundation structure, such as an anchor, mat, or pile, and onwards into the seabed or other setting, as efficiently and effectively as possible. Known assemblies, such as those shown in Figures 1 to 3 herein, rely on the transference of load primarily around the top and bottom points at which the wellhead (system) meets a part or parts of the foundation structure. In the example of Figures 1 to 3 herein, this load transference happens from the flange ring 130 to the receptacle support ring 124, at an upper end of the conductor housing receptacle 123, and from the adaptor ring 128 to the inner pipe support ring 110, at a lower end of the conductor housing receptacle. As can be seen from those figures, the transfer of load from the flange ring to the receptacle support ring relies on a heavily bolted, pretensioned connection. It also, in known assemblies, relies on specific surface roughness of either the flange ring and / or the receptacle support ring, to create friction between those two components. This set up for load transfer is limited, in terms of the maximum load size that can be transferred. It also generates a lot of wear and tear in the component parts.

[0023] There is a desire for alternative and / or improved ways of transferring load from a wellhead system to a subsea foundation structure.

[0024] According to a first aspect, an assembly (e.g. a connecting assembly) is provided for connecting a well head system to a subsea foundation structure, the assembly comprising a first component and a second component. The first component has a first opening and the second component has a second opening, which is configured for insertion of a wellhead system therethrough. The second component comprises a (e.g. first) recess for receiving at least part of the first component therein, wherein the second component comprises a housing portion that is configured to extend away from the first component, when the first component has been received in the recess of the second component.

[0025] The assembly may be referred to as being a ‘connecting assembly’. The first component may be referred to as being (or comprising) a ‘plate’, or a ‘ring’ or a ‘connecting component’. It may also comprise an additional part, which may be referred to as an ‘intermediary component’, as detailed further below.

[0026] The second component may be referred to as being a ‘receptacle’, or as a ‘conductor housing receptacle’, or as a ‘connecting component’. The second component may comprise a substantially laterally / radially outwardly extending ring (or ‘plate’, or ‘flange’) at an upper end of the housing portion. The second component may comprise a substantially laterally / radially inwardly extending ring (or ‘flange’) at a lower end of the housing portion. These three parts of the second component may be formed as one integral unit or one or more of them may be formed separately to the respective others, and connected thereto in any suitable manner.

[0027] The first component may be for securing the wellhead system to the subsea foundation structure. For example, the first component may be configured to lock, clamp, fix, or otherwise secure at least part of the wellhead system, relative to the second component. For example, the first component may be configured to secure at least part of the wellhead system in (or, within) the housing portion of the second component. For example, the first component may be configured to lock, clamp, fix, or otherwise secure at least part of the wellhead system, relative to the subsea foundation structure. The first component may be configured secure at least part of the wellhead system to the second component, and hence relative to the subsea foundation structure with a pretension. The may allow loads exerted on the wellhead system to be effectively transferred to the assembly (e.g. to the first component and / or second component) and then into the subsea foundation structure. Because the assembly is configured so that the first component is received within a recess of the second component, there will be a lateral - i.e. ‘side-to-side’ or ‘radial’ - connection between at least part of the first and at least part of the second component. That connection may be a direct connection, with an outer surface of the first component abutting or otherwise contacting a surface defined by the recess in the second component, or it may be an indirect connection, for example with one or more interconnecting components located between the first and second components. Regardless of whether the lateral connection between the two components is direct or indirect, it can enable transfer of load from the first component to the second component in a lateral - i.e. ‘side-to-side’ or ‘radial’ - direction. Therefore, any movement and / or other forces - such as, but not limited to, shear forces and / or bending moments - that the first component is subjected to can be transferred from the first component to the second component, and on towards the subsea foundation structure and on to the seabed or other surrounding area, in a lateral - i.e., ‘sideways’ or ‘radial’ - direction. In other words, the geometrical fit between the first component and the second component may enable lateral load transfer from the wellhead system to the subsea foundation structure. This means that, when the second component is comprised within, or otherwise connected to, the subsea foundation structure, and a wellhead system is inserted into the assembly, the load(s) experienced by the wellhead system, which will in whole or in part be exerted by the wellhead system on the assembly, can be dissipated out of the first component, into the second component and beyond, in a reliable and efficient manner.

[0028] The above-described lateral load transfer in the present assembly is a significant advantage over known assemblies, which rely on substantially abutting (plane to plane) contact and transfer of load between components of connecting assemblies, such as those shown in Figures 1 to 3 herein. Those known assemblies therefore rely on surface roughness of the abutting surfaces, and / or on using large numbers of physically large mechanical fasteners, such as nuts and bolts, to connect the components of those assemblies together and to withstand the significant load transfer that occurs between those components. Those nuts and bolts (or other large mechanical fasteners) therefore limit the size of the load that can safely be transferred by such known assemblies - and therefore limit the size of the load that the corresponding wellheads can be subjected to. By contrast, the receiving of the first component in the recess of the second component of the assembly provided herein, and the ensuing lateral load transfer, enables much larger loads to be transferred, safely and efficiently. This means that larger loads can be safely applied to the corresponding wellhead systems, within the limits of the wellhead system. In other words, the improved interaction between the first and second components herein reduces the chances of the wellhead-to- structure interface being the weakest and limiting feature of the whole well system. This is highly useful, to enable the wellhead systems to meet modern safety and operational standards, and to operate more efficiently.

[0029] Whilst the present assembly may use mechanical fasteners - such as but not limited to bolts - to enhance the security of the connection of the first component to the second component, and vice versa, it may not rely on those bolts for handling significant load transfer, because the load transfer may occur laterally in the present assembly, between overlapping respective surfaces of the first and second components. Therefore, the mechanical fasteners, such as bolts, used in the present assembly may be smaller than the bolts used in known assemblies, and may be used in fewer numbers. For example, the number of bolts used for the present assembly may be between one third to two thirds of the number used for a known assembly of a similar size and type. For example, the present assembly may use approximately half the number of bolts that previously would have been used for a known assembly of a similar size and type. In some embodiments, there may be no mechanical fasters, e.g. no bolts, between the first component and second component. This may be because sufficient load transfer and securement between the first component and the second component may be achieved from the fitting of the first component in the recess of the second component such that mechanical fasteners, such as bolts, between the first and second components is not required.

[0030] The mechanical fasteners, such as bolts, that may be used with the present assembly may be smaller in (lateral) diameter than the bolts typically used in known assemblies of a similar size and type. Moreover, the mechanical fasteners, such as bolts, that may be used with the present assembly may protrude less from the upper surfaces of the assembly (in a vertical direction, when the assembly is correctly installed for connection of a wellhead system to a subsea structure) than the nuts / bolts typically used in known assemblies of a similar size and type. The mechanical fasteners, such as bolts, that may be used with the present assembly may be inserted from an underside of the second component, and may extend through the second component and at least partially through the first component, such that their distal ends finish just above, or flush with, or lower than, an uppermost surface of the first component (using the directionality when the assembly is correctly installed for connection of a wellhead system to a subsea structure). Therefore, the mechanical fasteners may not protrude at all from, or may protrude only a little from, an upper surface of the first component, when the assembly is in situ. This may provide an advantage over known assemblies, in which large and bulky nuts and / or bolt-heads typically sit on top of an upper surface of the component(s) that connect a wellhead system to a subsea structure.

[0031] The mechanical fasteners, such as bolts, may be secured to the first and / or second component by a threaded connection. The mechanical fasteners, such as bolts, may be secured to the other of the first and / or second component by a nut. For example, the one or more bolts (if present) may be screwed into the first component (e.g. into one or more respective threaded holes therein) and protrude from the bottom of the first component. The attaching of the bolts to the first component by a threaded connection may be performed onshore. When the first component (with the one or more bolts secured thereto) is located over and around the wellhead system and landed on the second component, the one or more bolts may be received in and extend through one or more respective holes in the second component. One or more nuts may be used to secure the one or more bolts, and hence first component, in place on the second component. The nuts may be screwed onto the bolts on the underside of a flange portion of the second component. Viewed from above, when the first component is installed and secured to the second component, the fasteners may not be visible. This may allow the fasteners (e.g. one or more nuts and bolts) to be in a hidden / tucked away location so that they are unlikely to be in the way of or snag on other equipment used on or near the wellhead.

[0032] It will be appreciated that, when the present assembly is installed for connection of a wellhead system to a subsea structure, and when a wellhead system is received in the assembly, an upper part of the well head system may remain exposed, above the first component, and a lower part of the wellhead system may be surrounded by the housing portion of the second component, below the first component. The upper, exposed part of the wellhead system (e.g. upper end of a high-pressure wellhead housing) may provide a connection surface for external components such as a large connector - such as but not limited to a hydraulic connector, a mechanical connector, a clamp or an electrically actuated connector - or a BOP, or an Xmas tree, or a rig or a riser to connect to.

[0033] Because the first component of the present assembly is configured to be received in - i.e., to ‘sit in’ - a recess defined within the second component, there can be at least partial overlap of the thickness / depth of the first component with the thickness / depth of the second component (in a vertical direction, when the assembly is correctly installed for connection of a wellhead to a subsea structure). Therefore, the first component may ‘sit’ lower, relative to the top of the subsea structure, than is possible with known assemblies of a similar size and type. As a result, the vertical position of a wellhead system received by the assembly may be optimised with respect to load transfer and requirement for free space around and below the High-Pressure Wellhead, compared with known assemblies of a similar size and type. As a result, the loads (such as turning moments) experienced by the wellhead system, assembly, and subsea structure may be reduced through positioning the wellhead system as low as possible. Moreover, there is the potential for reduced bolting requirement for the assembly, as compared to known assemblies. For example, the present assembly, may use fewer, and / or smaller, mechanical fasteners, which may not need to protrude above the upper surface of the assembly in order to provide a secure connection. This may allow additional space in the area upwards of the assembly and below top of wellhead housing, for other parts that may be required, such as (but not limited to) hydraulic piping, flow loops and other features on connecting equipment, that may extend into this area.

[0034] Because the present assembly enables lateral load transfer between the first and second components, the assembly may be overall more durable than known assemblies are. Notably, the safe operating life of the first component may be longer than the safe operating lives of connecting components of known assemblies of a similar size and type. This is because, at least in part, the present assembly may not rely on high compressive forces being exerted by large bolts, urging two connecting components together whilst transferring load therebetween. Such high compressive forces from large bolts, experienced by known assemblies, cause significant wear and tear and necessitate the frequent checking and replacement of connecting components in those known assemblies. By contrast - and because it has changed the principle of force coupling, vis-a-vis the force coupling in known assemblies - the present assembly may transfer higher loads than known assemblies of similar size / type, and the parts, including but not limited to the first component, may last longer, and may be used multiple times, whereas in known assemblies, connecting component parts often have to be replaced after a single use.

[0035] A radially (or, laterally) innermost surface of the first component may be radially (or, laterally) inward of a radially innermost surface of the second component. In other words, the first component may be radially / laterally closer to the wellhead system (and hence closer to the central axis of the wellhead system), than the second component is, when the wellhead system is inserted into the assembly, for connection to the subsea foundation structure. A radially (or, laterally) outermost surface of the second component may be radially (or, laterally) outward of a radially outermost surface of the first component. Therefore, loads experienced by the wellhead system may be transferred from it to the first component, in a lateral direction, and on from the first component to the second component, also in a lateral direction, and onwards to the (rest of the) subsea structure.

[0036] Using the directionality of the assembly when it is correctly installed, for connection of a well head system to a subsea foundation structure, an uppermost surface of the first component may be located above an uppermost surface of the second component and a lowermost surface of the second component may be located below a lowermost surface of the first component.

[0037] It will be appreciated that directional terms such as ‘above’, ‘below’, ‘upper’, ‘lower’, ‘inner’, ‘outer’, and so on are relative terms, which are used herein to aid understanding. Unless otherwise specified, these terms are used to define the (relative) locations of various parts when the assembly is installed.

[0038] The first component may be a plate, such as but not limited to a metal plate, such as but not limited to a steel plate. The first component may be a ring, such as a (substantially) conical ring. The first component may be annular. The first component may comprise an upper (or ‘uppermost’) surface, which may be (but is not limited to being) substantially circular (or oval, or elliptical) in outer cross section, and a lower (or ‘lowermost’) surface, which may also be (but is not limited to being) substantially circular (or oval, or elliptical) in outer cross section, and an outer edge or rim, which may be referred to as an ‘outer wall’, which connects the upper and lower surfaces to one another. The outer wall may extend substantially perpendicular to the upper and lower surfaces of the first component, and therefore may be described as being substantially cylindrical. Alternatively, the outer wall may extend at a nonperpendicular angle to the upper and lower surfaces of the first component - thereby being sloped or inclined, relative to the vertical, when the assembly is installed correctly for connecting a wellhead system to a subsea structure - and therefore may be described as being substantially frusto-conical. Alternatively, the outer wall of the first component may adopt any other suitable profile. The outer wall of the first component may have at least a portion, e.g. a lower portion, that extends substantially perpendicular to the upper and lower surfaces of the first component. This may comprise a portion of the outer wall that in use is received in the recess in the second component.

[0039] The first opening, defined in the first component, may be provided substantially at a lateral or radial centre of the first component, or it may be provided offset from that centre, or at another location. The first opening may be, but is not limited to being, substantially circular in cross section. The first opening may extend from the upper surface to the lower surface of the first component - i.e. , it may create a hole, or passageway, through the first component. The radially outer extent of the first opening may define an inner edge, or inner rim, of the first component, which may be referred to as an ‘inner wall’, which connects the upper and lower surfaces of the first component to one another. That inner wall may be cylindrical or may be frusto-conical or may adopt any other suitable profile. For example, the inner wall may be stepped or undulating, such that the first opening may not have the same diameter, or width, across the entire thickness / depth of the first component. The inner wall of the first component may be shaped to be complementary with a portion of an outer surface of the wellhead system. This portion of the outer surface of the wellhead system may be the portion with which the first component may engage when the assembly is installed with a well head system therein.

[0040] The upper surface of the first component may be substantially planar. The first component may have the same thickness across its radius (except at the location of the first opening). Alternatively, the first component may comprise a first region and a second region, wherein the first region is thicker than the second region, or vice versa. For example, each of the first and second regions of the first component may be defined by a respective annulus, wherein the annulus defining the first region is radially outward of the annulus defining the second region, or vice versa.

[0041] The first component is configured to be received in the (e.g. first) recess of the second component, thus allowing the creation of an overlap between the two components. Less than all of the first component may be received in the recess of the second component. In other words, a part or parts of the first component may be received in the second component. A lowermost surface of the second component may be configured to sit below a lowermost surface of the first component, when the assembly is in situ, in connection with the subsea foundation structure. The second component may be wider than - i.e., may have a greater diameter (or lateral extent) than - the first component, wherein the recess occupies less than the full width - i.e., less than the full diameter (or lateral extent) - of the second component.

[0042] The first opening, in the first component, may be configured to surround at least part of the wellhead system, when the wellhead system has been inserted through the second opening and when the first component has been received in the recess of the second component. In practice, the first component may be configured to be received into the recess of the second component after the wellhead system has been inserted into the second opening of the second component. Therefore, the first component may be configured to be fitted over the inserted wellhead system (with an upper part of the wellhead system going through the first opening in the first component), in order for the first component to be received in the recess of the second component. The first component may be used to secure (e.g. fix, lock, clamp etc), the wellhead system relative to the first component and / or relative to the subsea foundation structure.

[0043] The second component may be annular. The second component may be substantially circular (or oval, or elliptical) in outer cross section. The second component may comprise an upper (or ‘uppermost’) surface, which may be (but is not limited to being) substantially circular (or oval, or elliptical) in outer cross section, and a lower (or ‘lowermost’) surface, which may also be (but is not limited to being) substantially circular in outer cross section, and an outer edge or rim, which may be referred to as an ‘outer wall’, which connects the upper and lower surfaces of the second component to one another. The outer wall may extend substantially perpendicular to the upper and lower surfaces of the second component, and therefore may be described as being substantially cylindrical. Alternatively, the outer wall may extend at a non-perpendicular angle to the upper and lower surfaces of the second component - thereby being sloped or inclined, relative to the vertical, when the assembly is installed correctly for connecting a wellhead to a subsea structure - and therefore may be described as being substantially frusto-conical. Alternatively, the outer wall of the second component may adopt any other suitable profile. The second component may be configured to be substantially concentric with the first component, when the first component is received in the recess of the second component. The housing portion of the second component may be configured to be substantially concentric with the first and / or second openings, when the first component is received in the recess of the second component.

[0044] The recess may be provided in an upper surface of the second component. The recess may be referred to as being a ‘step’ or a ‘concavity’ within an upper surface of the second component. The recess may be said to define a ‘receiving volume’ of the second component, for receiving the first component.

[0045] The (e.g. first) recess may comprise one continuous recess, or it may comprise multiple recess portions, which may be separated or spaced from one another in / on an upper surface of the second component. In embodiments in which the recess comprises multiple recess portions, the portions may be sized, shaped, and / or otherwise configured to receive one or more complementary respective portions or parts of the first component. The recess (or the or each recess portion) may occupy less than the whole surface area of an upper surface of the second component. The recess (or the or each recess portion) may be substantially symmetrical about a central axis of the second component, or it may be non-symmetrical about, and / or offset from, such a central axis.

[0046] The second component may comprise a flange portion, wherein the recess is defined in the flange portion of the second component. The flange portion may extend substantially laterally outwards from an upper part of the housing portion of the second component.

[0047] The recess may occupy less than the full lateral extent of the flange portion. Therefore, an upper surface of the flange portion of the second component may be substantially non- planar, or may be ‘stepped’, in order to define the recess therein. In other words, there may be a first upper surface portion of the flange portion, and a second upper surface portion of the flange portion, the second upper surface portion being laterally outward of the first upper surface portion, and a wall - which may be referred to as a (e.g. first) ‘recess wall’ - connecting the first upper surface portion to the second upper surface portion. The first upper surface portion of the flange portion may be stepped down, or lower, relative to the second upper surface portion. In other words, the (shortest) distance from the first upper surface portion of the flange portion to its lower surface may be less than the (shortest) distance from the second upper surface portion of the flange portion to its lower surface. The first upper surface portion of the flange portion may therefore define the lateral extent of the recess, which is configured to receive the first component. The first upper surface portion, recess wall, and second upper surface portion of the flange portion may be continuous with one another and may together define a ‘stepped’ profile of the upper surface of the flange portion. The size and / or shape of the recess, and so of the first upper surface portion of the flange portion, may be complementary to the size and / or shape of the first component.

[0048] The system may be designed so that the presence of the recess in the second component does not weaken it, nor diminish the ability of the present assembly to transfer large loads from a wellhead system to a subsea foundation structure. To the contrary, the recess may enable higher load transfers - and / or, enables the assembly and the subsea structure to receive lower effective loads, from the same external forces - because it enables the second component to receive the first component, and so to allow lateral load transfer therebetween, and to enable the first component and the wellhead system to sit lower / deeper into the (or, relative to the) subsea structure, than has been possible to date with existing connecting assemblies. Thus, the present assembly may have the potential to meet the ever-increasing standards for load transfer from a wellhead to a subsea foundation structure, to account for the increased sizes and forces from components that connect to the wellhead, such as BOP’s, Xmas trees, rigs, risers and so on.

[0049] The second opening, defined in the second component, may be provided substantially at a lateral or radial centre of the second component, or it may be provided offset from that centre, or at another location. The second opening may be, but is not limited to being, substantially circular in cross section. The second opening may be configured to align and overlap, at least in part, with the first opening, when the first component is received in the recess of the second component. For example, an upper part of the second opening (using the directionality of the assembly when in situ for connecting a wellhead to a subsea structure) may align with a lower part of the first opening in the first component, when it is received in the recess of the second component. The second opening may extend from the first upper surface portion of the second component to a lower surface of the second component - i.e., it may create a hole, or passageway, through the second component. The radially outer extent of the second opening may define an inner edge, or inner rim, of the second component, which may be referred to as an ‘inner wall’, which connects the upper and lower surfaces of the second component to one another. That inner wall may be cylindrical or may be frusto-conical or may adopt any other suitable profile. For example, the inner wall may be stepped or undulating, such that the second opening may not have the same diameter, or width, across the entire thickness / depth of the second component.

[0050] The second opening in the second component may have a larger diameter than the first opening in the first component. The diameter of the first opening may be substantially equal to the outer diameter of the wellhead system with which it engages during use (this for example may be the conductor housing or the high-pressure wellhead housing).

[0051] The lower surface of the second component may be substantially planar, or it may have a stepped or undulating or other non-planar profile. For example, there may be a thinner area (which may be annular) surrounding the second opening in the second component compared to the radially outermost portion of the second component.

[0052] At least part of an outer surface of (at least part of) the first component may be arranged to abut at least part of the (e.g. first) recess wall (or, of a wall around a recess portion) of the second component, when the first component is received by the second component. In addition, some or all of a lower surface of the first component (or, the lower surfaces of more than one respective parts of the first component) may abut / contact an upper surface of at least a part (or parts) of the second component, when the first component is received by the second component. In other words, some or all of an outer part of the first component may directly touch a part or parts of the second component.

[0053] For example, at least part of an outer rim (or outer wall) of the first component may be arranged to abut at least part of the recess wall of the second component, when the first component is received by the second component. In other words, some or all of the outer rim, or outer wall, of the first component may touch the recess wall of the second component. In addition, some or all of the lower surface of the first component may (e.g. directly) abut / contact the first upper surface portion of the flange portion of the second component, when the first component is received by the second component. The assembly may be configured such that the second component supports the first component from below and / or there is direct contact between the first component and the second component when the first component is landed on and / or secured to the second component. Because at least part of the outer rim of the first component may abuts at least part of the recess wall of the second component, lateral load transfer may be enabled, between the two plates. The first component and the second component may be configured such that there is a tight fit between at least part of the first component and at least part of the second component when the first component is received in the (first) recess of the second component. For example, the outer rim of the first component may be substantially the same shape and / or size as the recess wall. For example, when the parts are substantially circular, the outer rim of the first component may have a diameter that is approximately the same size as the inner diameter of the recess wall.

[0054] The first component may comprise (or consist of) a single part, such as a plate or annular ring or cone as described above. In some embodiments, the first component may comprise more than one part. For example, it may comprise one or more projections or formations, which may for example be located on an underside of the first component. For example, the one or more projections or formations may be configured to be received in the recess (or, in respective recess portions) of the second component.

[0055] For example, the first component may comprise a first ‘insert’ (or ‘ring’, or ‘plate’) and an intermediary component, configured to locate between at least part of the first insert and at least part of the second component, when the first component is received by the second component. In other words, the intermediary component may sit between at least part of an outer surface of the first insert and at least part of a surface of the second component. In such scenarios, the ‘recess’ in the second component may comprise or include a groove, and the intermediary component may comprise, for example, a seal ring, which sits between the groove of the second component and the first insert. In such embodiments, the first insert may also (or instead) include an indentation or groove, configured to receive and engage with the intermediary component. Thus, the intermediary component may help to provide a lateral load path between the wellhead system and the subsea structure, via the first and second components. The first component and / or the second component may be formed from any suitable material such as, but not limited to, metal. For example, one or both components may be formed from steel.

[0056] The second component may further comprise a support ring, in connection with the housing portion, distal to the flange portion of the second component. The support ring may be configured to extend laterally / radially inwards from a lower part of the housing portion. When the assembly is located in situ for connecting a wellhead system to a subsea foundation structure, the support ring may therefore be located at a lower end of the second component, distal (i.e. , opposite) to the flange portion. The support ring may have a third opening defined in it, which may be concentric with the volume defined by the housing portion and / or with the second opening in the (flange portion of) the second component. The support may be substantially annular. The (solid part of) the support ring may be substantially planar in radial profile, or it may it may have a non-planar, such as an undulating or stepped, radial profile.

[0057] The assembly may further comprise an adaptor ring (e.g. a lower adaptor), configured to fit laterally inwards of at least part of the housing portion and to engage with the support ring. For example, the adaptor ring may sit onto at least part of, and / or be received in at least part of, the support ring. The adaptor ring may therefore be laterally / radially closer to the wellhead system than at least part of the support ring is, when a wellhead system is received in the assembly. An outer profile of the adaptor ring may be configured to complement an inner profile of the support ring, and / or an inner profile of the housing portion. An inner profile of the adaptor ring may be configured to complement an outer profile of a wellhead system (or of a housing or casing within the wellhead system), which is to be received by the assembly and connected to the subsea foundation structure.

[0058] Although the term ‘ring’ is used herein, this should not be regarded as limiting the support ring or the adaptor ring to being substantially circular in cross section. Either or both may be substantially circular in cross section, or to have any other suitable cross-sectional shape. The adaptor ring may be configured to contact - either directly or indirectly - a lower / distal part of the wellhead system (e.g. a lower part of the conductor housing), when it is received in the assembly. The adaptor ring may therefore be configured to transfer loads exerted on it, from the distal part of the wellhead system, to the support ring.

[0059] The second component may be configured to be connected to, or comprised within, the subsea foundation structure. For example, it may be connected to or be comprised within an upper part of the subsea foundation structure, which may comprise a top frame of the subsea foundation structure. The part of the subsea foundation structure that the second component is comprised within, or connected to, may not itself be wholly located within the seabed. In other words, the part of the subsea foundation in which the second component is configured to be located in use may be (at least partially) above seabed level.

[0060] For example, the support ring may be connected to, or integral with, the subsea foundation structure. The adaptor ring and support ring may therefore combine with one another, to transfer loads from the distal end of the wellhead system to the subsea foundation structure.

[0061] If the second component extends above the height of the top frame of the subsea foundation structure, the subsea foundation structure may additionally comprise one or more support parts. This may occur if the assembly needs to accommodate a wellhead system that has a longer vertical extent than the vertical extent of the top frame of the subsea foundation. This may result in the assembly comprising a second component that has a longer vertical extent than the top frame of the subsea foundation. These one or more support parts may be for allowing the transfer of loads from the top portion of the second component (i.e. the portion that extends beyond the top of the top frame) to the top frame of the subsea foundation structure. The support parts may for example be triangular shaped support parts. The triangular support parts may be connected to the outside of an upper part of the second component (e.g. an upper portion of the housing of the second component) by a substantially vertical inner surface and / or connected to part of the upper surface of the support frame by a substantially horizontal radially extending surface. The one or more support parts may each be connected, such as welded, between a part of the subsea foundation structure, e.g. the top frame of the foundation, and an upper portion (e.g. an upper portion of the housing) of the second component. When the second component extends above the height of the top frame of the subsea foundation structure there may be the advantage that unwanted material, e.g. debris, can be more easily cleared away from the opening / top of wellhead system during and / or after drilling. This clearing of unwanted material may be facilitated by the presence of triangular support parts as described above.

[0062] The assembly may be configured so that, when the first component is received in the second component and the second component is connected to, or comprised within, the subsea foundation structure, an upper surface of the first component remains exposed, above the seabed. The upper surface of the first component may therefore be located above the subsea foundation structure, or at least above the parts of the subsea foundation structure that themselves are located within the seabed.

[0063] A conductor housing may be provided, wherein the conductor housing is configured to be located laterally / radially inward of an inner surface of the housing portion of the second component. The conductor housing may be regarded as being part of the wellhead system.

[0064] The conductor housing (if present) may be configured to surround at least (another) part of the wellhead system (e.g. the high pressure wellhead housing) comprised within a wellhead system, when the wellhead system is received in the assembly. An outer profile of the conductor housing may be configured to complement an inner profile of the second component of the assembly. An inner profile of the conductor housing may be configured to complement an outer profile of another part of the wellhead system that is to be received by the assembly and connected to the subsea foundation structure. At least part of an inner surface of the conductor housing may be configured to abut, or otherwise contact, an outer surface of another part of the wellhead system (e.g. high pressure wellhead housing) when the wellhead system is inserted into the assembly.

[0065] The conductor housing (if present) may be configured to locate laterally / radially inward of at least one of: the first opening in the first component; and / or the second opening in the second component. An upper part of the conductor housing (using the directionality of the assembly when correctly installed for connection of a wellhead to a subsea structure) may be configured to extend, at least partially, through the second opening in the second component, and possibly also at least partially through the first opening in the first component. An upper part of the conductor housing may therefore be configured to sit between another part of the received wellhead system and a laterally inner surface of the first component and / or between another part of the received wellhead system and a laterally inner surface of the second component. The conductor housing may therefore assist with lateral transfer of loads from another part of the wellhead system to the first component and possibly also to the second component.

[0066] An inner surface of the first component and / or an inner surface of the second component may be configured to contact an outer surface of the wellhead system, when it is inserted into the assembly. An inner surface of the first component and / or an inner surface of the second component may be configured to contact an outer surface of a conductor housing, if present.

[0067] The first component may comprise a first plurality of holes, configured to receive a corresponding plurality of mechanical fasteners for mechanically fastening the first component to the second component. The second component may comprise a second plurality of holes, configured to also receive the plurality of mechanical fasteners for mechanically fastening the first component to the second component. The assembly may be configured for the mechanical fasteners to be inserted from an underside of the second component, through the first and second pluralities of holes, for mechanically fastening the first component to the second component. Thus, the mechanical fasteners may not have to extend above an upper surface of the first component, when the assembly is in situ for connecting a wellhead to a subsea foundation structure.

[0068] The first component and / or the second component may include one or more (respective) features not specifically detailed herein, such as for example formations, grooves, indentations, holes, and so on, for engaging with any suitable mechanical fasteners. Such features and mechanical fasteners, if present, may help to secure the first component to the second component and / or the second component to the subsea foundation structure and / or the first component to the subsea foundation structure. The assembly may include a wellhead, or a wellhead system, or a wellhead housing, received therein. The wellhead system may comprise a conductor housing and / or a high pressure wellhead housing.

[0069] The first and second components of the assembly may be manufactured by any suitable method(s), using any suitable material(s). The first and second components may be manufactured and / or supplied separately to one another.

[0070] The second component may comprise a second recess. The second recess may be for receiving another part of the first component therein. The second recess may be radially inward and / or lower (in a vertical direction) than the first recess. The second recess may also be on the upper surface of the second component (in addition to the first recess). When the second component comprises the first recess and the second recess, the upper surface of the second component may have two steps thereon that act as the two respective recesses.

[0071] The assembly may comprise a third component.

[0072] The second recess (if present) of the second component may be for receiving at least part of the third component therein. The second recess (if present) of the second component may be for receiving at least part of the third component therein. Thus the second component may comprise a first recess for receiving at least part of the first component therein and / or a second recess for receiving at least part of the third component and / or another part of the first component therein. By providing the second component with a second recess (for the third component and / or another part of the first component) the lateral load transfer from the wellhead system into the subsea foundation via the second component may be improved.

[0073] The housing portion of the second component may be configured to extend away from the third component (in addition to the first component) when the third component has been received in the second recess of the second component (and when the first component has been received in the first recess of the second component). Thus in another aspect the present invention may provide an assembly for connecting a wellhead system to a subsea foundation structure, the assembly comprising: a first component; a second component; and a third component; the first component having a first opening; the second component having a second opening, which is configured for insertion of a wellhead system therethrough; the second component comprising a first recess for receiving at least part of the first component therein and / or a second recess for receiving at least part of the third component therein; wherein the second component comprises a housing portion that is configured to extend away from the first component and / or the third component, when the first component has been received in the first recess of the second component and / or when the third component has been received in the second recess of the second component.

[0074] The second recess of the second component (e.g. the recess for receiving at least a portion of the third component) may (additional to the first recess) be defined in the flange portion of the second component.

[0075] The third component may comprise a third opening. The third opening, in the third component, may be configured to surround at least part of the wellhead system, when the wellhead system has been inserted through the second opening and when the third component has been received on (e.g. in the second recess) of the second component.

[0076] The third component may be configured to be substantially concentric with the first and / or second component, when the first, second and / or third component are installed.

[0077] The third component may in use be located radially between the first component and / or second component and part of the received wellhead system.

[0078] The third component may be for providing an adaptor, spacer and / or interface between the wellhead system (i.e. conductor housing and / or a high-pressure wellhead) and the first component and / or second component. The third component may provide a direct interface between the outer surface of the wellhead system (e.g. an outer surface of the conductor housing) and the first component and / or second component. The inner wall of the third component may be shaped to be complementary with a portion of an outer surface of the wellhead system. The third component may comprise a shoulder and / or landing surface (e.g. a recess) on which a portion of the wellhead system (e.g. a protrusion on the outer surface of the wellhead system) may be received. The third component may comprise a tapered radially inner surface. The opening of the third component may have a larger diameter at the top of the third component and the opening of the third component may have a smaller diameter at the bottom of the third component. This may be so that the third opening is arranged to directly receive and support the wellhead system when installed.

[0079] This the third component may be for providing a landing surface for the wellhead system (e.g. the conductor housing may be directly landed in the third component).

[0080] In use, at least part of the radially outer surface of the third component may directly contact at least part of the radially inner surface of the first component and / or at least part of the radially inner surface of the second component. In use, at least part of the radially inner surface of the third component may directly contact at least part of the radially outer surface of the wellhead system (e.g. at least part of the radially outer surface of the conductor housing).

[0081] The third component may allow the assembly to accommodate wellhead systems of different designs without having to change the first component and / or second component. For example, a different third component may be used, with a different respective inner radius and / or a different inner profile shape - but with the same outer profile - to enable a variety of different wellhead systems to successfully engage with the first component and / or second component and hence with the assembly, and so with the subsea foundation structure. Thus the third component may be regarded as an adaptor. The third component may be for adapting the assembly so that it can correctly and / or securely connect a wellhead system to a subsea foundation. Thus the third component may allow the first component and second component to be adapted to be used with many different wellhead system designs. The third component may be referred to as an upper adaptor compared to the adaptor ring (e.g. a lower adaptor) described above. The third component may thus be referred to as a spacer and / or (upper) adaptor. When installed the third component (e.g. upper adaptor) may be at or towards the upper part of the assembly and the adaptor ring may be at or towards the bottom part of the assembly. For example, the third component may be provided at or above the top part of the housing portion of the second component and the adaptor ring may be provided at or below the bottom part of the housing portion of the second component. The third component may have an internal profile that is complementary to the outer profile of the received wellhead system, e.g. the outer surface of the conductor housing. This may allow the assembly to have a reliable interface with the wellhead system.

[0082] The third component may provide a load path for forces from the wellhead system to first component and / or the second component.

[0083] The second recess may be more radially inward and lower than the first recess.

[0084] When the assembly is installed, the third component may overlap in a vertical direction the connection / interface between the first component and the second component.

[0085] The assembly may comprise a locking ring. The locking ring may be located radially (e.g. directly) between the first component and the wellhead system (e.g. between the first component and the conductor housing). The locking ring may be located vertically above or below the third component (if present). The locking ring may interface with a corresponding groove on the radially outer surface of the wellhead assembly (e.g. with a groove on the radially outer surface of the conductor housing). The locking ring may be for securing the wellhead head system in the connection assembly (together with the first component). The locking ring may be used to prevent upwards movement of the wellhead system relative to the connection assembly and / or subsea foundation structure. This may for example be used to prevent movement of the wellhead due to well growth and / or otherwise arrest upwards movement of the wellhead system (e.g. at least the conductor housing).

[0086] The assembly may comprise a third component (which as described above may have an interface, spacing and / or adapting function) and a separate locking ring. Alternatively, the assembly may not comprise both a third component and a separate locking ring. In some assemblies the third component may be configured itself to be a locking ring (e.g. the third component may be for securing the wellhead system in the connection assembly and / or to arrest upward movement of the wellhead assembly relative to assembly and / or the subsea foundation structure). This may be achieved by the outer surface of the wellhead system (i.e. outer surface of the conductor housing) having a groove in which the radially inner surface of the third component may be received. The third component may be a flexible (e.g. collet) ring or multipiece part. The third component may be arranged so that it can be forced into the groove on the outer surface of the wellhead system to thereby grip the outer surface of the wellhead system. The assembly may be arranged so that when assembled the third component is forced radially inward (e.g. onto the radially outer surface of the wellhead system) when the first component is located around the third component and secured to the second component. The third component may have the dual function of acting as a locking ring to secure the wellhead system in a vertical direction and to provide a lateral load path for forces exerted on the wellhead to the first and / or second component.

[0087] It has been realised that an assembly for connecting a wellhead system to a subsea foundation structure, that comprises a first component for securing at least part of the wellhead system to the subsea foundation structure, and a second component, and a third component, wherein the third component is arranged to in use be located between at least part of the first component and / or second component and at least part of the wellhead system can have certain advantages, irrespective of whether the first and / or second recess described above are provided.

[0088] Thus in another aspect, there may be provided an assembly for connecting a wellhead system to a subsea foundation structure, the assembly comprising a first component, a second component and a third component; wherein the first component is for securing at least part of the wellhead system to the subsea foundation structure; wherein the second component has an opening, which is configured for insertion of a wellhead system therethrough; and wherein the third component is arranged to in use be located between at least part of the first component and / or second component and at least part of the wellhead system.

[0089] The assembly of this aspect may have one or more or all of the above described features, including optional features, (with or without the presence of the recess in the second component) described in relation to the first aspect. For example, this arrangement may have a first component, second component and / or third component and other features as described in detail above. According to a second aspect, a method is provided of connecting a well head system to a subsea foundation structure using a connecting assembly, the connecting assembly comprising a first component and a second component. The first component has a first opening. The second component has a second opening and comprises a (e.g. first) recess for receiving at least part of the first component therein. The second component comprises a housing portion that is configured to extend away from the first component, when the first component has been received in the recess of the second component. The method comprises locating the second component within, or connecting the second component to, the subsea foundation structure, inserting a wellhead system through the second opening, and inserting the first component into the recess of the second component, wherein the first component is configured to surround at least part of the wellhead system, when the first component has been inserted into the recess of the second component.

[0090] The first component may be configured for securing the wellhead system to (and / or, within) at least part of the subsea foundation structure.

[0091] The connecting assembly recited in the method of the second aspect may be the assembly of any of the above described aspects, including the first aspect (including one or more or all of the optional features disclosed above in relation to the above aspects). The assembly of the above aspects (including the first aspect) may be configured to, and / or used to, perform the method of the second aspect (optionally including one or more or all of the optional features). Thus, the method may be performed using the assembly and vice versa the assembly may be used to, and / or configured to, perform the method.

[0092] Thus, in view of the third component described above, the method may comprise landing the third component on the second component. This may comprise inserting the third component into the second recess of the second component. This step of landing the third component on the second component may be performed before the step of inserting a wellhead system through the second opening. When the wellhead system is inserted into the assembly a distal end may be supported / landed on the second component (e.g. via the adaptor ring). A top end of the wellhead system may be supported by (and optionally landed on) the third component. A top end of the wellhead system may be supported by the first component. As described above, the third component may comprise a third opening. The method may comprise inserting the wellhead system through the third opening.

[0093] The first opening of the first component may be configured to surround at least part of the third component (if present), when the first component has been inserted into the recess of the second component.

[0094] The step of inserting the first component into the first recess of the second component may comprise locating the first component over and around the wellhead system and / or the third component.

[0095] The method may further comprise attaching one or more mechanical fasteners to the first component and to the second component, to mechanically fasten the first component to the second component. For example, the mechanical fasteners may be inserted at least partially through one or both components. The mechanical fasteners may be inserted from an underside of the second component, through the second component and at last partially through the first component. The mechanical fasteners, e.g. one or more bolts, may be connected to the first and / or second component by a threaded connection. The one or more bolts may extend through respective holes in the other of the first and second component and may be secured to the other of the first and second component by one or more respective nuts.

[0096] The mechanical fasteners may be used to apply a pretension (e.g. in a vertical direction) between the first component, second component and / or third component. This pretension may allow the wellhead system to be connected securely (and / or rigidly with respect to the typical forces expected on a subsea well) to the subsea foundation structure. This may allow effective transfer of loads (e.g. lateral loads) from the wellhead system to the subsea foundation structure.

[0097] Similarly to the connecting assembly above, it has been realised that a method of connecting a wellhead system to a subsea foundation structure using a connecting assembly, wherein the connecting assembly comprises a first component for securing at least part of the wellhead system to the subsea foundation structure, and a second component, and a third component, wherein the third component is arranged to in use be located between at least part of the first component and / or second component and at least part of the wellhead system can have certain advantages, irrespective of whether the first and / or second recess described above are provided.

[0098] Thus in yet another aspect, there may be provided a method of connecting a well head system to a subsea foundation structure using a connecting assembly, the connecting assembly comprising a first component, a second component and a third component; wherein the first component is for securing at least part of the wellhead system to the subsea foundation structure; wherein the second component has an opening which is configured for the insertion of a wellhead system therethrough; wherein the third component is arranged to in use be located between at least part of the first component and / or second component and at least part of the wellhead system; the method comprising: locating the second component within, or connecting the second component to, the subsea foundation structure; inserting a wellhead system through the second opening; locating the first component over and around the wellhead system and third component.

[0099] The method of this aspect may have one or more or all of the above described features, including optional features, (with or without the presence of the first or second recess in the second component) described in relation to the first and second aspect. For example, the connecting assembly used in this method may have a first component, second component and / or third component as described in detail above.

[0100] The method may comprise securing the first component to the second component.

[0101] According to a third aspect, a method is provided of manufacturing an assembly as described above in relation the above aspects (including but not limited to the first aspect), or a connecting assembly that may be used according to the method of the above aspects (including but not limited to the second aspect). According to a fourth aspect, a connector is provided, for connecting a well head system to a subsea foundation structure, the connector comprising an opening, configured to receive a wellhead system therein, and a housing portion, configured to surround at least part of the wellhead system, once it has been inserted through said opening. The connector further comprises a flange portion, surrounding the opening and extending substantially laterally outwards from the opening, the flange portion comprising a recess for receiving at least part of an insert, for securing the received wellhead system to and / or within the connector.

[0102] According to a fifth aspect, a connector is provided, for connecting a wellhead system to a subsea foundation structure. The connector is configured to receive at least a part of a wellhead system. The connector comprises a recess that is configured to receive an insert, for securing the received wellhead system to and / or within the connector.

[0103] The connector of the fourth insert and / or the connector of the fifth aspect may further comprise an insert, which may comprise a plate or ring, within the recess. The insert may fit around an upper part of the wellhead system. One or more mechanical fasteners may further be provided for securing the insert in place in the recess. The connector of the fourth aspect may be referred to as being a second component and it may be used in conjunction with a first component, as described in relation to any of the preceding aspects.

[0104] According to a sixth aspect, an assembly is provided for connecting a well head system to a subsea foundation structure, the assembly comprising a first component and a second component. The second component has an opening, which is configured for insertion of a wellhead system therethrough. The second component comprises a recess for receiving at least part of the first component therein. The first component is for securing the wellhead system to the subsea foundation structure.

[0105] One or more or all of the above described features of the above aspects (including optional features) are applicable to the other aspects including the third, fourth and fifth aspects detailed above. In overview, an assembly and method may be provided herein that may enable improved transfer of loads, and the transfer of increased loads, from a wellhead system to a subsea foundation structure, and / or into the seabed or other surrounding location. This for example may be achieved by the presence of one or more recesses in the second component and / or the provision of a third component between the first component and / or second component and the wellhead system.

[0106] The subsea foundation structure may comprise a suction anchor.

[0107] The subsea foundation structure may form the foundation and support of a subsea well for exploration and / or hydrocarbon production. However, the assembly and method described herein may also be used in conjunction with other subsea foundation structures including, but not limited to, piles, mats, gravity anchors, and other anchor types.

[0108] When the second component comprises a recess for receiving at least part of the first component therein, it may be possible for the assembly to rely on geometric shaping, and / or an improved contact fit between two respective components, in order to allow transfer of the load that is experienced by the first component, towards the subsea foundation structure and onwards towards the seabed, via the second component. The first component may be configured to be directly or indirectly connected to, or otherwise in contact with, a wellhead system and therefore may experience significant loads, such as but not limited to bending loads and shear forces, due to the connection of the wellhead system to external components such as a BOP or Xmas tree, or to rigs and / or risers, which can be extremely heavy and may be subject to vibration and / or other movement during use. The second component may be comprised within, or in connection with, the subsea foundation structure.

[0109] When at least part of the first component is accommodated within a recess or groove of the second component, loads that are experienced by the first component may be transferred laterally, or radially, from the first component to the second component, and may be absorbed more efficiently by the subsea structure and the surrounding seabed than is possible with known (pre-existing) assemblies. The subsea well itself may therefore be better protected from any detrimental effects that the loads exerted on the wellhead might otherwise cause. Moreover, if present, other mechanical attachments between the first and second components, such as bolts extending through the two components, may be reduced, in size and / or in number, and the need for surface roughness and the creation of friction between the two components may be reduced, or even eradicated, as compared to known assemblies.

[0110] The first component may be a unitary component or it may comprise multiple parts that may be separable from one other. For example, the first component may comprise a first part - which may be an upper part, when the first component is received in the second component - and it may further comprise an intermediary component that is configured to locate between the first part of the first component and the second component.

[0111] The second component may be a unitary component or it may comprise multiple parts, or portions, at least some of which are separable from the respective others. For example, two or more parts, or portions, of the second component may be welded together, or connected or formed together in any other suitable way.

[0112] Part or all of any of the aspects, examples, and / or embodiments described herein may be combined with one another in any suitable manner. Features that have been described in relation to one aspect, example, and / or embodiment herein, including but not limited to those features that have been described as being optional, may be implemented as part of one or more respective other aspects, examples and / or embodiments.

[0113] Figures

[0114] Certain example embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings in which:

[0115] Figure 1 is a side view of a known suction anchor foundation;

[0116] Figure 2 is a cross sectional of the suction anchor foundation of Figure 1 ;

[0117] Figure 3 is a cross sectional view of an upper part of a suction anchor, of a similar type to that shown in Figures 1 and 2, with a known connection to a wellhead system;

[0118] Figure 4 is a cross sectional view of an upper part of a suction anchor, with an improved connection assembly for connecting it to a wellhead system, as described herein;

[0119] Figure 5 is a cross sectional view of a first component and an upper part of a second component of the improved connection assembly described herein; Figure 6 is a cross sectional view of the first component and the upper part of a second component of Figure 6, with mechanical fasteners;

[0120] Figure 7a is an isometric view of a first component of an improved connection assembly;

[0121] Figure 7b is a view from above of the first component of Figure 7a;

[0122] Figure 7c is a cross-sectional view along the dashed line in Figure 7a;

[0123] Figure 8a is an isometric view of a second component of an improved connection assembly;

[0124] Figure 8b is a side view of the second component of Figure 8a;

[0125] Figure 8c is a cross-sectional view along the dashed line in Figure 8b;

[0126] Figure 8d is an isometric cross-sectional view along the dashed line in Figure 8b;

[0127] Figure 9 is a cross sectional view of an alternative connection assembly for connecting a wellhead system to a subsea foundation structure;

[0128] Figure 10 is an isometric cross-sectional view of the connection assembly shown in figure 9; and

[0129] Figure 11 is simplified version of the connection assembly shown in figures 9 and 10.

[0130] Detailed description

[0131] The assembly and method provided herein, which may enable improved transfer of loads, and the transfer of increased loads from a wellhead system into a subsea foundation structure - and / or the decrease in effective load felt as by the subsea foundation structure, from the same external loads applied to the wellhead system - can be better understood in relation to Figures 4 et seq, detailed below. The load transfer is described herein for the specific example of a wellhead system comprising a high-pressure wellhead housing, a conductor housing and a suction anchor. However, this should not be regarded as limiting. The present invention also encompasses applying the same principles to the transfer of load from any type of wellhead system to any / other types of subsea foundation structure such as (but not limited to) other anchor types, mats, piles (including but not limited to monopiles) and templates etc.

[0132] Figure 4 shows an improved connection assembly 201 , shown in situ for connecting a wellhead system, which in this example includes a high-pressure wellhead 216 and conductor housing 218, to a subsea foundation structure, which in this example is a suction anchor 200. The assembly 201 comprises a first component that comprises a flange ring 230, which is received by a recess formed in an upper surface of a second component 223. The second component 223 may be referred to as being a ‘receptacle’ 223 or as a ‘conductor housing receptacle’ 223. The conductor housing receptacle 223 comprises three parts: an upper flange portion, referred to herein as a ‘receptacle support ring 224’, a housing portion that is referred to herein as a substantially cylindrical collar 220, extending substantially downwards from a radially inner part of the receptacle support ring 224, and an inner pipe support ring 210, which is provided at a lower end of the collar 220, and extends substantially laterally / radially inwards therefrom. These three parts of the conductor housing receptacle 223 may be welded together or may be formed as an integral unit or may be connected or connectable to one another by any other suitable method.

[0133] The flange ring 230, in this example, is configured to form a secure connection between a received wellhead system and the conductor housing receptacle 223, and so to form a secure connection between the wellhead system and the suction anchor 200.

[0134] The conductor housing receptacle 223 is shown in this example as being received in, and held fast within, an upper surface of a top frame 221 of the suction anchor 200. The top frame 221 and suction anchor 200 are similar to the corresponding features of known assemblies, such as those shown and described above in relation to Figures 1 to 3, and so will not be described in detail herein. The top frame 221 and suction anchor 200 are both part of a subsea foundation structure which surrounds a subsea well. The central pipe 208 of the well can also be seen in Figure 4.

[0135] The inner pipe support ring 210 is configured to engage with an upper part of the central pipe 208 of the well. For example, the inner pipe support ring 210 may engage with the top of the central pipe 208 and help to physically support it, and keep it in place during operation of the well.

[0136] An adaptor ring 228 is provided, located radially inwards of, and sitting in engagement with (but physically separable from), the inner pipe support ring 210. A radially inner part of the adaptor ring 228 engages with (a lower part of) a conductor housing 218, which in turn contacts (for example, grips) an outer surface of the wellhead housing 216. The adaptor ring 228 therefore occupies a (lower part of a) lateral gap that exists (in this example) between the conductor housing receptacle 223 and the conductor housing 218. In other examples, the conductor housing 218 may be omitted, and a high-pressure housing 216, may be received directly in the conductor housing receptacle 223.

[0137] The adaptor ring 228 may, as the name suggests, be used to effectively adapt the inner profile of the conductor housing receptacle 223, and to thereby form a better fit between the present assembly 201 and a wellhead system that is to be received. For example, a different adaptor ring 228 may be used, with a different respective inner radius and / or a different inner profile shape - but with the same outer profile - to enable a variety of different wellhead systems to successfully engage with the assembly 201 , and so with the subsea foundation structure.

[0138] The conductor housing receptacle 223 may comprise any suitable shape or shapes, including one or more suitable indentations, projections or other mechanical features, in order to engage with any part of a wellhead system that is to be received and connected to the subsea foundation structure.

[0139] The improved assembly 201 of Figure 4 herein provides improved transfer of loads, and the transfer of greater loads, from the wellhead system to the subsea foundation structure, and on to the seabed or other setting, as compared to known connection assemblies. It also enables the reduction of the effective load felt by the subsea foundation structure, as a result of the same external loads being applied to the wellhead system. This is largely due to the interaction of the flange ring 230 and the conductor housing receptacle 223 - i.e., the interaction of the first component 230 and the second component 223 of the present assembly 201 - which can be understood in more detail in relation to Figures 5 and 6 herein. In overview, the receptacle supporting ring 224 (i.e., the flange portion of the conductor housing receptacle 223) includes a stepped-down area, or recess, into which the flange ring 230 can locate, such that at least a part of an outer wall of the flange ring 230 interfaces with a wall of the recess in the receptacle support ring 224. This enables lateral / radial transfer of load from the flange 230 ring to the receptacle support ring 224, and therefore enables lateral transfer of load from the wellhead system to the subsea foundation structure. In this example embodiment, each part of the conductor housing receptacle 223 has a substantially circular outer cross-sectional profile, and as shown in Figure 4. However, this is not essential and may vary in other embodiments. The conductor housing receptacle 223 can be made to complement a receiving portion in an upper part of a subsea foundation structure, for connection thereto. The conductor housing receptacle 223 can in fact be integral to the subsea foundation structure - such as being comprised within a top frame of a subsea foundation structure.

[0140] Figure 5 shows an upper part of an improved connection assembly 501, similar to that shown in Figure 4, with a first component 530 fitting into a recess in an upper part 524 of a respective second component (with only the upper part 524 of the second component shown). Figure 6 shows another similar improved connection assembly 601 (with only the first component 630 and an upper part of the second component 624 shown) and a plurality of mechanical fasteners passing through a respective plurality of holes in each of the two components, to bolster the mechanical connection therebetween. Figures 7a to 7c show various views of a first component of an improved connection assembly and Figures 8a to 8d show various views of a second component of an improved connection assembly as described herein.

[0141] As can be seen in Figure 5, and as can be better seen in Figures 8a to 8d herein, the upper part of the second component 523 comprises a flange portion, or receptacle support ring 524, and has a stepped upper surface, with a first upper surface portion 504 and a second upper surface portion 506. In this example, both the first upper surface portion 504 and the second upper surface portion 506 are annular, and substantially concentric with one another, with the first upper surface portion 504 being radially inward of, and lower than, the second upper surface portion 506. The first upper surface portion 504, and a wall 508 (which may be referred to as a ‘recess wall’) around the perimeter thereof, therefore defines the recess 531. The first component 530 of the assembly - i.e., the flange ring 530, which is also shown in Figures 7a to 7c - can be received by, and sit within, the recess 531 , with at least part of an outer wall of the flange ring 530 being in contact with the wall 508 of the recess 531. The recess wall 508 in the example Figures herein is shown as being substantially perpendicular to the first upper surface portion 504, but this may vary in other embodiments. For example, the recess wall may slope, so as to take on a frusto-conical profile, or it may have any other suitable profile. In the example of Figure 5, the underside, or lower surface 550, of the receptacle support ring 524 is also non-planar, and has an undulated profile such that the lower surface of a radially-innermost part of the receptacle support ring 524 is raised relative to the lower surface of the radially-outermore part(s) of the receptacle support ring 524. However, this is not essential, and will not be present in all embodiments. For example, the underside of the receptacle support ring 524 is shown as having a substantially flat profile in Figures 8a to 8d.

[0142] An opening - such as the substantially central opening 514 shown in Figures 5 and 8a to 8d - is present in the receptacle support ring 524, and enables a wellhead system to be inserted therethrough, when the second component (which may be referred to as a conductor housing receptacle) 523 is in situ, in connection with a subsea foundation structure. Such an opening may however not be at a radial centre of the conductor housing receptacle, in all embodiments.

[0143] Although not shown in Figures 5 and 6, a collar 520 (i.e. , the housing portion of the conductor housing receptacle 523) extends substantially downwards from a radially inner part of the receptacle support ring 524. This is shown in Figures 8a to 8c. Thus, a wellhead system that is inserted through the opening 514 will be at least partially surrounded by the collar 520.

[0144] In practice, a wellhead system may be inserted through the opening 514, and on towards the collar 520 of the conductor housing receptacle 523. A lower part of the inserted wellhead system may be configured to contact the inner pipe support ring portion 510 of the conductor housing receptacle 523 (also not shown in Figures 5 and 6, but visible in Figure 8c and Figure 8d). As shown in those Figures, an upper surface of the inner pipe support ring 510 may be non-planar, in some embodiments. For example, in Figures 8c and 8d it has a stepped, or undulating, profile. For example, it may be sized and / or shaped to fit with an external surface of a wellhead system and / or with a surface of an adaptor ring or a surface of a conductor housing, either or both of which may sit between the conductor housing receptacle 523 and a wellhead system that is received therein.

[0145] The flange ring 530 also comprises a respective opening 516, which in this example is located substantially at its radial centre. The opening 516 in the flange ring 530 is sized and located so as to coincide, at least in part, with the opening 514 in the receptacle support ring 524, when the flange ring 530 is received in the recess 531 thereof.

[0146] After the wellhead system has been inserted through / into the conductor housing receptacle 523, the flange ring 530 can then be inserted over the top of the wellhead system (with the upper parts of the wellhead system passing through the opening 516 therein) and can be received in the recess 531 in the upper surface of the receptacle support ring 524. The flange ring 530 can thus also surround (part of) the wellhead system and can sit (at least partially) into the upper part of the conductor housing receptacle 523.

[0147] An outer wall of the flange ring 530, 630 is shown as directly touching the recess wall of the receptacle support ring 524, 624 in Figures 5 and 6. In other embodiments, there may be an intermediary component between at least part of the flange ring and at least part of the receptacle support ring. Such an intermediary component may provide grip, or sealing, between the two components, and may enable lateral load transfer therebetween. Either the flange ring and / or the receptacle support ring may comprise a suitable groove or indentation for interacting with such an intermediary component.

[0148] In the example shown in Figures 5 and 6 herein, an underside, or lower surface, of the flange ring 530, 630 is non-planar, and has an undulated profile such that the lower surface of a radially-innermost part of the flange ring 530, 630 is raised relative to the lower surface of the radially-outermore part(s) of the flange ring 530, 630. Specifically, in this example, the region of the flange ring 530, 630 that is radially inward of an inner radius of the receptacle support ring 524, 624 is thinner than the region of the flange ring 530, 630 that coincides (in a lateral / radial direction) with the receptacle support ring 524, 624. However, this is not essential, and will not be present in all embodiments - it is not, for example, shown in the example of Figures 7a to 7c. An opening - such as the substantially central opening 516 shown in Figures 5 to 7c herein - however will be present, and enables the flange ring 530, 630 to be inserted over a wellhead system, into the recess in the conductor housing receptacle 523. Such an opening may however not be at a radial centre of the flange ring in all embodiments. The examples of Figures 5 to 7c show a plurality of holes 534, 634 in an upper surface of the flange ring 530, 630. In fact, those holes 534, 634 extend through the flange ring 530 and a corresponding plurality of holes 536 are provided through the receptacle support ring 524, to enable mechanical fasteners such as bolts to be inserted therethrough, to bolster the mechanical connection between the two components. Relatively few holes may be provided, as compared to known / previous connecting assemblies. This is exemplified in Figure 6, in which relatively few, relatively small, holes 634 are provided, for mechanical fasteners (in this case, bolts 538) to be inserted therethrough. These bolts can be inserted from an underside of the receptacle support ring 524, 624, such that they do not extend upward of the flange ring 530, 630, when it is received in the receptacle support ring 524, 624. These bolts 538 are much smaller, in all three dimensions, as compared to the bolts typically used in known / previous connecting assemblies. Therefore, the area above the flange ring 530, 630 - which can include an upper part of a received wellhead system - will be unimpeded by the bolts 538, and so will be more accessible to external components that need to connect to, or that otherwise need to be located in the vicinity of, the wellhead system.

[0149] Figures 9 and 10 show another connection assembly 801, shown in situ for connecting a wellhead system, which includes a conductor housing 818 and / or a high-pressure wellhead 816, to a subsea foundation structure, which in this example is a suction anchor 800.

[0150] The assembly 801 comprises a first component 830. This component 830 may be referred to an outer ring 830 and / or a securing component 830.

[0151] A lower portion of the securing component 830 is received in a first recess 812 formed in an upper surface / portion of a second component 823.

[0152] The second component 823 may be referred to as being a ‘receptacle’ 823, a wellhead receptacle’ 823 an / or as a ‘conductor housing receptacle’ 823. The conductor housing receptacle 823 comprises three parts: an upper flange portion, referred to herein as a ‘receptacle support ring 824’, a housing portion that is referred to herein as a substantially cylindrical collar 820, extending substantially downwards from a radially inner part of the receptacle support ring 824, and an inner pipe support ring 810, which is provided at a lower end of the collar 820, and extends substantially laterally / radially inwards therefrom. These three parts of the conductor housing receptacle 823 in this figure are shown as formed as an integral unit but they may alternatively be separate parts that are welded together, connected or connectable to each other, or otherwise held relative to one another by any other suitable method.

[0153] The connection assembly 801 additionally comprises a third component 850. The third component 850 in use is located radially between the first component 830 and an upper part of the second component 823 and part of the received wellhead system 816, 818. This third component 850 is for providing an adaptor, spacer and / or interface between the wellhead system (i.e. conductor housing 818 and / or a high-pressure wellhead 816) and the first component 830. As shown the third component 850 can provide a direct interface between the outer surface of the wellhead system (i.e. in this case the conductor housing 818) and the first component 830.

[0154] The third component 850 may allow the assembly 801 to accommodate wellhead systems of different designs without having to change the first component 830. For example, a different third component 850 may be used, with a different respective inner radius and / or a different inner profile shape - but with the same outer profile - to enable a variety of different wellhead systems to successfully engage with the first component 830 and hence with the assembly 801, and so with the subsea foundation structure. In this sense the third component 850 may be regarded as an adaptor. In other words, the third component 850 may be used to adapt the assembly 801 so that it can correctly and / or securely connect a wellhead system to a subsea foundation, depending on the wellhead system used, without necessarily having to change the first component 830 or second component 823. Thus the first component 830 and second component 823 may be adapted to be used with many different wellhead system designs simply by providing a suitable adaptor 850. This may be an upper adaptor 850 compared to the adaptor ring 828 described below. The third component may thus be referred to as a spacer and / or (upper) adaptor 850.

[0155] The third component 850 can have an internal profile that is complementary to the outer profile of the received wellhead system. This may allow the assembly 801 to have a reliable interface / connection with the wellhead system. The third component 850 provides a load path for forces from the wellhead system to first component 850 and / or the second component 823.

[0156] A lower portion of the third component 850 is received in a second recess 814 formed in an upper portion / surface of the second component 823.

[0157] The second recess 814 is more radially inward and lower than the first recess 812.

[0158] The first component (i.e. securing component) 830 is configured to form a secure connection between the received wellhead system 816, 818 and the second component (i.e. the conductor housing receptacle) 823, and so to form a secure connection between the wellhead system and the suction anchor 800. This may be achieved at least by the securing component 830 being secured by mechanical fasteners, such as bolts 838, to the receptacle 823.

[0159] In this assembly 810, the bolts 838 are secured by threaded connection to threaded holes in the first component 830 and extend through holes in the second component 823. The bolts 838 and hence first component 830 are secured to the second component 823 by nuts on each bolt on the underside of the receptacle support ring 824 of the second component 823.

[0160] The assembly 801 additionally comprises a locking ring 840. The locking ring 840 is located radially between the first component 830 and the wellhead system (i.e. conductor housing 818). The locking ring 840 is located vertically above the third component 850. The locking ring 840 interfaces with a corresponding groove on the radially outer surface of the wellhead assembly (in this case the conductor housing 818). When the first component 830 is installed over the wellhead system and secured to the second component 823, the locking ring 840 is forced into engagement with the groove on the outer surface of the conductor housing 818. The locking ring 840 is for securing the wellhead head system in the connection assembly 801 (together with the first component (i.e. securing component)) 830. In particular the locking ring 840 may be used to prevent upwards movement of the wellhead system relative to the connection assembly 801 and / or foundation 800. This may for example be used to prevent movement of the wellhead due to well growth. Although in this assembly 801 there is a third component 850 acting as a spacer and / or upper adaptor and a separate locking ring 840, the function of the locking ring may be achieved using the third component 850. This may be achieved by the outer surface of the wellhead system (i.e. outer surface of the conductor housing 818) having a groove in which the radially inner surface of the third component 850 can be received. The third component 850 may be provided by a flexible (e.g. collet) ring or multipiece part that can be forced into the groove to thereby grip the outer surface of the wellhead system. This gripping action of the third component 850 onto the radially outer surface of the wellhead system may be achieved by forcing the first component 850 over the wellhead and third component 850 and then securing the first component 830 to the second component 823 such as by means of one or more bolts 838 and nuts.

[0161] The conductor housing receptacle 823 is shown in this example as being received in, and fixed (e.g. welded) within, an upper surface of a top frame 821 of the suction anchor 800. The top frame 821 and suction anchor 800 are similar to the corresponding features of known assemblies, such as those shown and described above in relation to Figures 1 to 3, and so will not be described in detail herein other than the presence of additional triangular support part 822. These additional triangular support parts 822 are provided because the length of the conductor housing receptacle 823 is longer than the top frame 821. These additional triangular support parts 822 are welded to the top of the top frame 821 and are provided to ensure that loads can be effectively transferred from the wellhead system 816, 818 into the top frame 821, suction anchor 800 and hence ultimately into the seabed despite the fact that the second component 823 in this assembly is longer than the top frame 821. The top frame 821 , triangular support parts 822 and suction anchor 800 are all part of a subsea foundation structure which surrounds a subsea well. These are used to provide a secure and stable foundation for a subsea well and are fixed securely to the seabed such that loads can be effectively transferred from the foundation into the seabed.

[0162] A central pipe 808 of the well can also be seen in Figures 9 and 10.

[0163] The inner pipe support ring 810 is configured to engage with an upper part of the central pipe 808 of the well. For example, the inner pipe support ring 810 may engage with the top of the central pipe 808 and help to physically support it, and keep it in place during operation of the well. For example, the central pipe 808 may be fixed (e.g. welded) to the bottom of the pipe support ring 810 such that the central pipe 808 effectively is hung from the inner pipe support ring 810.

[0164] A lower adaptor ring 828 is provided, located radially inwards of, and sitting in engagement with (but physically separable from), the inner pipe support ring 810. A radially inner part of the adaptor ring 828 engages with (a lower part of) a wellhead (e.g. a conductor housing 818) received in the receptacle 823. The adaptor ring 828 therefore occupies a (lower part of a) lateral gap that may exist between the conductor housing receptacle 823 and the wellhead system, in particular in this case the conductor housing 818.

[0165] The adaptor ring 828 may, as the name suggests, be used to effectively adapt the inner profile of the conductor housing receptacle 823, and to thereby form a better fit between the present assembly 801 and a wellhead system that is to be received. For example, a different adaptor ring 828 may be used, with a different respective inner radius and / or a different inner profile shape - but with the same outer profile - to enable a variety of different wellhead systems to successfully engage with the assembly 801, and so with the subsea foundation structure.

[0166] The assembly 801 of Figures 9 and 10 (similarly to the assembly of Figure 4) provides improved transfer of loads, and the transfer of greater loads, from the wellhead system to the subsea foundation structure, and on to the seabed or other setting, as compared to known connection assemblies as described in detail above. This ability of effective load transfer is largely due to the interaction of the first component 830, third component 850 and the second component (i.e. conductor housing receptacle) 823. The receptacle supporting ring 824 (i.e., the flange portion of the conductor housing receptacle 823) includes two steppeddown areas, or recesses, into which the first component 830 and third component 850 can locate, such that at least a part of an outer wall of the first component 830 and outer wall of the third component 850 each interface with a wall of a respective recess in the receptacle support ring 824. This enables lateral / radial transfer of load from the third component 850 and / or first component 830 to the receptacle support ring 824, and therefore enables lateral transfer of load from the wellhead system (secured in the receptacle 823 by the first component 830) to the subsea foundation structure. The presence of the third component 850 in assembly 801 compared to the assembly 201 of figure 4 may allow the provision of a more adaptable and / or reliable connection between the wellhead system and the foundation 800. This may allow the more effective transfer of loads from the wellhead system to the foundation (irrespective of whether the first and second recesses are present).

[0167] The assembly 801 may be put together and hence the wellhead system 816, 818, secured to the foundation 800 by the following steps. A foundation comprising the suction anchor 800, top frame 821 and support parts 822 together with the second component 823 all securely and rigidly (e.g. with respect to the forces experienced by a typical subsea well) connected together is provided. An adaptor ring is located on the inner pipe support ring 810 of the second component 823. The third component 850 is seated in a radially inner recess 814 of the receptacle support ring 824. The wellhead system (comprising a conductor housing 818 and / or a high pressure housing 816) is received in the second component 823 and interfaces directly with the adaptor ring 828 and third component 850. The first component 830 is located over the top of the wellhead system 816, 818. The first component 830 may then be secured to the second component 823 by mechanical fasteners, e.g. bolts 838 and nuts. This connection and securing of the first component 830 to the second component 823 may result in a pre-tensioning (e.g. rigid clamping) of the assembly 801. This may clamp at least part of the wellhead system (e.g. conductor housing 818) into the second component 823 and hence foundation with a pretension such that forces exerted on the wellhead assembly during use can be effectively transferred to the second component 823 and hence foundation (and so ultimately to the seabed) during operation (e.g. drilling or producing) of the well.

[0168] The wellhead system may be secured into the second component 823 before or after the foundation is secured to the seabed.

[0169] A simplified version of the assembly (comprising a third component 850) shown in figures 9 and 10 is shown in figure 11. This shows the assembly 801 with the wellhead assembly (i.e. conductor housing 818 and high pressure wellhead housing 816), locking ring 840 and other features of the subsea foundation structure removed for the purpose of the other features being able to be seen more clearly. The other corresponding features are labelled with the same reference numerals for ease. Specifically, as described in more detail above the connection assembly 801 comprises a first component 830, second component 823 and third component 850. The first component 830 is for securing a wellhead system to the subsea foundation structure. The second component 823 is made up of the receptacle support ring 824, cylindrical collar 820 and inner pipe support ring 810 and is for receiving at least part of the wellhead system therein. An inner pipe 808 hangs from the inner pipe support ring 810. The third component 850 in use is located radially between the first and / or second component 830, 823 and the wellhead system and provides a spacer, interface and / or adaptor between the wellhead system at least the first component 830.

[0170] The assembly additionally comprises a lower adaptor 828 as described above.

[0171] The subsea foundation structure comprises suction anchor 800, support frame 821 and additional support parts 822.

[0172] One notable difference between the arrangement of figure 11 and that shown in figures 9 and 10 is that the third component 850 does not have a landing shoulder / recess for the wellhead system. This is an optional feature that may or may not be provided depending on factors such as the precise wellhead system design and the force requirements.

[0173] The improved assemblies described herein allow the provision of a compact and robust solution for improved transfer of load - in a lateral direction - from a wellhead system to a subsea foundation structure. This may be achieved by the presence of one or more recesses in a second component and / or the provision of a third component as described above. The component parts are relatively simple and cost effective to manufacture, and yet enable the transfer of greater loads than has been possible to date, with known connection assemblies, in a manner that causes less component wear than is typically experienced with such known assemblies. Moreover, the improved assembly described herein may enable parts of a wellhead system to sit deeper / lower, relative to a subsea foundation structure, than has previously been possible. Therefore, the effect of loads exerted on upper / exposed parts of the wellhead system, such as by external components, will be reduced, and may be absorbed and mitigated more easily, as compared to when those loads are exerted on known / previous connecting assemblies. The improved connection assembly therefore may allow meeting of current and expected-future safety standards and load-bearing standards, in a manner and to an extent that has not previously been achievable by known connecting assemblies of a comparable size and type.

[0174] The second component - often referred to above as the “conductor housing receptacle” - of the present assembly can be sized and shaped to fit into, or otherwise connect with, known subsea foundation structures and also with future subsea foundation structures. As will be appreciated from the foregoing description, because the recess may be provided in a radially-inner portion of (i.e. , in the upper / flange portion of) the conductor housing receptacle, its outer dimension and / or shape can remain the same as in known assemblies. Therefore, the present solution can be retrofitted to existing structures, as well as being implemented in new structures. And the radially-inner features of the second component, including the size and shape of the recess, can be designed and manufactured (or, where appropriate, resized or restructured) to complement any desired first component, with which it is to connect. In embodiments, the second component will be operable to cooperate with a variety of different respective first components - for example, with flange rings of different respective depths. One or more additional components, such as but not limited to conductor housings and / or to intermediary components such as lock rings or seals, may also be used to bridge a gap between, or otherwise to bolster a connection between, the second component and a first component.

[0175] The first component of the present assembly - often referred to above as the “flange ring” - can be received into the recess of the conductor housing receptacle by being mechanically lowered or otherwise installed, using any suitable means. The flange ring may be large and very heavy - for example, approximately 0.5 tonnes to 3 tonnes, for example 1 tonnes, in weight - and so the flange ring and conductor housing receptacle can be sized and shaped to fit together neatly and readily, without the need for much, if any, direct human intervention. Therefore, the risk of fingers being trapped, or any other injuries being incurred, is reduced, as compared to known assemblies.

[0176] The solution provided herein is scalable, both in terms of physical size of the components involved and in terms of the possibility of manufacturing them on a large numerical scale. Therefore, the solution is practical and affordable, whilst also being highly desirable, as detailed above. It meets and exceeds rigorous safety standards, thus enabling safe and scalable operation of subsea wells, in which a wellhead system connects to a subsea foundation structure.

[0177] The following clauses set out features of the invention that may or may not be claimed in the present claim set. These clauses may form the basis of future claims in the present application or applications derived therefrom.

[0178] 1. An assembly for connecting a wellhead system to a subsea foundation structure, the assembly comprising: a first component; a second component; and a third component; the first component having a first opening; the second component having a second opening, which is configured for insertion of a wellhead system therethrough; the second component comprising a first recess for receiving at least part of the first component therein and / or a second recess for receiving at least part of the third component therein; wherein the second component comprises a housing portion that is configured to extend away from the first component and / or the third component, when the first component has been received in the first recess of the second component and / or when the third component has been received in the second recess of the second component.

[0179] 2. An assembly for connecting a wellhead system to a subsea foundation structure, the assembly comprising: a first component; a second component; and a third component; wherein the first component is for securing at least part of the wellhead system to the subsea foundation structure; wherein the second component has an opening, which is configured for insertion of a wellhead system therethrough; and wherein the third component is arranged to in use be located between at least part of the first component and / or at least part of the second component and at least part of the wellhead system. 3. An assembly according to clause 1 or 2, wherein the third component provides a load path for forces from the wellhead system to first component and / or the second component.

[0180] 4. An assembly according to clause 1 , 2 or 3, wherein the second component comprises a second recess, and wherein the second recess is for receiving another part of the first component and / or at least part of the third component therein.

[0181] 5. An assembly according to clause 4, wherein the second recess is radially inward and / or lower than the first recess.

[0182] 6. An assembly according to clause 4 or 5, wherein the second component comprises two recesses such that at least a part of an outer wall of the first component and at least part of the outer wall of the third component each interface with a wall of a respective recess in the second component.

[0183] 7. An assembly according to any preceding clause, wherein the third component comprises a third opening, wherein the third opening is configured to surround at least part of the wellhead system, when the wellhead system has been inserted through the second opening and when the third component has been received on of the second component.

[0184] 8. An assembly according to any preceding clause, wherein the third component is for providing a direct interface between an outer surface of the wellhead system and a radially inner surface of the first component and / or second component.

[0185] 9. An assembly according to any preceding clause, wherein, in use, at least part of a radially outer surface of the third component directly contacts at least part of the radially inner surface of the first component and / or at least part of the radially inner surface of the second component.

[0186] 10. An assembly according to any preceding clause, wherein, in use, at least part of the radially inner surface of the third component directly contacts at least part of the radially outer surface of the wellhead system.

[0187] 11. An assembly according to any preceding clause, wherein third component is for providing a landing surface for at least part of the wellhead system.

[0188] 12. An assembly according to any preceding clause, wherein when the assembly is installed, the third component overlaps in a vertical direction a connection between the first component and the second component.

[0189] 13. An assembly according to any preceding clause, wherein the third component is for providing the dual function of acting as a locking ring to secure the wellhead system in a vertical direction and to provide a lateral load path for forces exerted on the wellhead to the first and / or second component.

[0190] 14. A method of connecting a well head system to a subsea foundation structure using a connecting assembly, the connecting assembly comprising a first component; a second component; and a third component, wherein the first component has a first opening, wherein the second component has a second opening and comprises a first recess for receiving at least part of the first component therein and / or a second recess for receiving at least part of the third component therein, wherein the second component comprises a housing portion that is configured to extend away from the first component, when the first component has been received in the recess of the second component, wherein the method comprises: locating the second component within, or connecting the second component to, the subsea foundation structure, inserting a wellhead system through the second opening, inserting the first component into the recess of the second component and / or inserting the third component into the second recess of the second component wherein the first component is configured to surround at least part of the wellhead system, when the first component has been inserted into the recess of the second component.

[0191] 15. A method of connecting a well head system to a subsea foundation structure using a connecting assembly, the connecting assembly comprising a first component, a second component and a third component; wherein the first component is for securing at least part of the wellhead system to the subsea foundation structure; wherein the second component has an opening which is configured for the insertion of a wellhead system therethrough; wherein the third component is arranged to in use be located between at least part of the first component and / or second component and at least part of the wellhead system; the method comprising: locating the second component within, or connecting the second component to, the subsea foundation structure; inserting a wellhead system through the second opening; locating the first component over and around the wellhead system and third component.

[0192] 16. The method of clause 14 or 15, wherein the connecting assembly comprises the assembly of any of clauses 1 to 13.

Claims

Claims:

1. An assembly for connecting a well head system to a subsea foundation structure, the assembly comprising a first component and a second component; the first component having a first opening; the second component having a second opening, which is configured for insertion of a wellhead system therethrough; the second component comprising a recess for receiving at least part of the first component therein; wherein the second component comprises a housing portion that is configured to extend away from the first component, when the first component has been received in the recess of the second component.

2. The assembly of claim 1 , wherein the first opening is configured to surround at least part of the wellhead system, when the wellhead system has been inserted through the second opening and when the first component has been received in the recess of the second component.

3. The assembly of claim 1 or claim 2, wherein the second component includes a flange portion, wherein the recess is defined in the flange portion of the second component.

4. The assembly of claim 3 wherein the recess occupies less than the full lateral extent of the flange portion of the second component.

5. The assembly of claim 3 or claim 4 wherein the flange portion of the second component comprises: a first upper surface portion, which defines the lateral extent of the recess; a second upper surface portion, the second upper surface portion being laterally outward of the first upper surface portion; and a recess wall connecting the first upper surface portion to the second upper surface portion.

6. The assembly of claim 5 wherein the first component has an outer edge, at least part of which is arranged to abut at least part of the recess wall, when the first component is received in the recess of the second component.

7. The assembly of any of claims 1 to 6, wherein the first component comprises a first insert and an intermediary component, wherein the intermediary component is configured to locate between at least part of the first insert and at least part of the second component, when the first component is received by the second component.

8. The assembly of claim 7, wherein the first insert comprises a groove that is configured to receive at least part of the intermediary component.

9. The assembly of any preceding claim, wherein the second component includes a flange portion in connection with the housing portion, and comprises a support ring in connection with the housing portion, distal to the flange portion.

10. The assembly of claim 9, further comprising an adaptor ring, configured to fit laterally inwards of at least part of the housing portion and to engage with the support ring.

11. The assembly of any of claims 1 to 10 wherein at least part of the second component is configured to be comprised within, or connected to, the subsea foundation structure.

12. The assembly of claim 11 , the assembly being configured so that, when the first component is received in the recess of the second component, and when the second component is connected to, or comprised within, the subsea foundation structure, an upper surface of the first component remains exposed, above the seabed.

13. The assembly of any preceding claim wherein an inner surface of at least one of: the first component or the second component is configured to contact an outer surface of a wellhead system, when the wellhead system is inserted into the assembly.

14. The assembly of any preceding claim, the first component comprising a first plurality of holes, configured to receive a corresponding plurality of mechanical fasteners for mechanically fastening the first component to the second component.

15. The assembly of claim 14, the second component comprising a second plurality of holes, configured to also receive the plurality of mechanical fasteners for mechanically fastening the first component to the second component.

16. The assembly of claim 15, wherein the assembly is configured for the mechanical fasteners to be inserted from an underside of the flange portion of the second component, through the first and second pluralities of holes, for mechanically fastening the first component to the second component.

17. A method of connecting a well head system to a subsea foundation structure using a connecting assembly, the connecting assembly comprising a first component and a second component; the first component having a first opening; the second component having a second opening; the second component comprising a recess for receiving at least part of the first component therein; wherein the second component comprises a housing portion that is configured to extend away from the first component, when the first component has been received in the recess of the second component; the method comprising: locating the second component within, or connecting the second component to, the subsea foundation structure; inserting a wellhead system through the second opening; and inserting the first component into the recess of the second component; wherein the first opening is configured to surround at least part of the wellhead system, when the first component has been inserted into the recess of the second component.

18. The method of claim 17, wherein the connecting assembly comprises the assembly of any of claims 1 to 16.

19. The method of claim 17 or claim 18 further comprising attaching one or more mechanical fasteners to the first component and to the second component, to mechanically fasten the first component to the second component.

20. The method of any of claims 17 to 19 further comprising providing a subsea foundation structure, and locating the second component within, or connecting the second component to, the provided subsea foundation structure.

21. A method of manufacturing an assembly as claimed in any of claims 1 to 16.

22. An assembly for connecting a wellhead system to a subsea foundation structure, the assembly comprising: a first component; a second component; and a third component; wherein the first component is for securing at least part of the wellhead system to the subsea foundation structure; wherein the second component has an opening which is configured for insertion of the wellhead system therethrough; and wherein the third component is arranged to in use be located between at least part of the first component and / or second component and at least part of the wellhead system.

23. The assembly of claim 22, wherein the third component is for providing a load path for forces from the wellhead system to the first component and / or second component.

24. The assembly of claim 22 or 23, wherein the third component comprises a third opening, wherein the third opening is configured to surround at least part of the wellhead system, when the wellhead system has been inserted through the second opening and when the third component has been received on the second component.

25. The assembly of claims 22, 23 or 23, wherein the third component is for providing a direct interface between an outer surface of the wellhead system and a radially inner surface of the first component and / or second component.

26. The assembly of any of claims 22 to 25, wherein when the assembly is installed, the third component overlaps, in a vertical direction, a connection between the first component and the second component.

27. The assembly of any of claims 22 to 26, wherein the third component is for providing the dual function of acting as a locking ring to secure the wellhead system in a vertical direction and to provide a load path for forces exerted on the wellhead to the first and / or second component.

28. The assembly of any of claims 22 to 27, wherein the assembly is assembly of any of claims 1 to 16.

29. A method of connecting a well head system to a subsea foundation structure using a connecting assembly, the connecting assembly comprising: a first component; a second component; and a third component; wherein the first component is for securing at least part of the wellhead system to the subsea foundation structure; wherein the second component has an opening which is configured for the insertion of a wellhead system therethrough; wherein the third component is arranged to in use be located between at least part of the first component and / or second component and at least part of the wellhead system; the method comprising: locating the second component within, or connecting the second component to, the subsea foundation structure; inserting a wellhead system through the second opening; locating the first component over and around the wellhead system and third component.

30. The method of claim 29, wherein the connecting assembly comprises the assembly of any of claims 1 to 16 or of any of claims 22 to 28.