PRODUCTION SYSTEM

The present disclosure relates to an adapter assembly for connecting a flowline to a subsea tree at a subsea installation, a flowline connector assembly and a subsea production system.

BACKGROUND

In general, a subsea tree or a subsea Christmas tree (hereinafter referred to as a valve tree or simply a “tree”, commonly abbreviated XT orXMT) is a system of valves, flow paths and connectors installed on a subsea wellhead to control the flow of fluid from a reservoir. A flowline connector is commonly used to connect subsea flowlines to the subsea tree via suitable jumpers. Typically, an end of each flowline is generally lowered vertically to the subsea tree from a vessel, and the flowline is then laid out horizontally between the points to be interconnected, thereby providing safe and leak-proof connections between the subsea tree and flowlines extending to other components of, for example, a subsea production system.

Flowline connectors are typically connected to valve arrangements on one or more sides of the subsea tree. For example, flowlines can connect a manifold to a XT to convey gas/fluids to or from another component or a remote location. Connectors for such flowlines can be placed at sides of the XT pointing vertically downwards or upwards, or connectors arranged for horizontal connections. A given flowline and connection may transmit petroleum fluids, other well fluids, hydraulic fluids for XT systems, chemicals (e.g. for injection into the well), or other fluids.

Documents which may be useful for understanding the field of technology include US6481504B1 , US6098715A, US5593249A, US4615646A, US8672038 B2,

WO2017209785, and US8151890 B2.

In view of the trends in the petroleum industry to exploit more remote or harsh locations (e.g., in deepwater or arctic regions), and the desire to provide higher utilization of existing fields, there is a continuous need in the industry for improved technology in relation to subsea well arrangements and production systems. This includes, for example, aspects of operational reliability, design flexibility, or operational efficiency. It is an objective of the present invention to provide improvements over the state of the art in at least one of the abovementioned areas, or at least to provide alternatives to known technology. SUMMARY

In an embodiment, there is provided an adapter assembly for connecting a flowline to a subsea tree, the adapter assembly comprising: an adapter base; a first connection element connected to the adapter base and configured for connecting to a fluid line connector on the subsea tree; a flowline connector assembly with a second connection element configured for connecting to an end portion of the flowline, wherein the flowline connector assembly is attached to the adapter base; the adapter assembly configured for connecting to the subsea tree through the first connection element.

In an embodiment there is provided a subsea production system comprising a plurality of subsea trees, wherein at least one of the plurality of subsea trees is provided in a multi-slot template and at least another of the subsea trees is provided in a single-slot foundation, wherein at least one of the plurality of subsea trees comprises an adapter assembly. BRIEF DESCRIPTION OF THE DRAWINGS

The above and other characteristics will become clear from the following description of embodiments, given as non-restrictive examples, with reference to the attached schematic figures.

Figures 1a and 1b illustrate schematically an adapter assembly for a subsea tree.

Figure 2 illustrates an adapter assembly.

Figure 3 is a section view of various components of the adapter assembly.

Figure 4 is a perspective view of the adapter assembly. Figure 5 illustrates an adapter assembly having a frame for holding a subsea tree.

Figure 6 illustrates the adapter assembly attached to a subsea tree.

Figure 7 illustrates a subsea production system comprising a plurality of wells.

Figure 8 illustrates alternative embodiments of an adapter assembly and a subsea tree.

Figures 9-11 show views of an embodiment of an adapter assembly and a subsea tree.

Figure 12 shows an embodiment of an adapter assembly and a subsea tree.

DETAILED DESCRIPTION

The following description may use terms such as “horizontal”, “vertical”, “lateral”, “back and forth”, “up and down”, ’’upper”, “lower”, “inner”, “outer”, “forward”, “rear”, etc. These terms generally refer to the views and orientations as shown in the figures and that are associated with a normal use of the invention. The terms are used for the reader’s convenience only and shall not be limiting.

Figures 1a and 1b illustrate an adapter assembly 100 for a subsea tree 10. The adapter assembly 100 is connected at a bottom portion of the subsea tree 10 as illustrated in Figs 1a and 1b. Referring initially to figures 1a and 1b, the adapter assembly 100 comprises an adapter base 20, a first connection element 30, a flowline connector assembly 40 and flowloops 50, between the first connection element 30 and the flowline connector assembly 40.

The adapter base 20 is a frame that supports a tie-in connection system and hubs with transmitting flowloops 50. The flowloops 50 may be a fluid connection comprising a single fluid conduit, or may comprise a plurality of fluid conduits. The adapter base 20 may be interchangeable and customizable for each type of tie-in system. The adapter base 20 plate can have shimming capabilities in order to make mounting adjustments and relaxing tolerances. The first connection element 30 is supported by the adapter base 20 and connected to the subsea tree 10 with a substantially vertical connection. The first connection element 30 interfaces with a corresponding fluid line connector 31 on an underside of the subsea tree 10. The flowline connector assembly 40 is preferably positioned or attached at an outer perimeter, for example on a side, of the adapter base 20 as illustrated in Figs 1a and 1b. The flowline connector assembly 40 comprises a second connection element 42 (not shown in Figs 1a and 1b but described below) which connects to an end portion of a subsea flowline (shown as 67-70 in Fig. 7).

In one embodiment, the flowline connector assembly 40 is oriented for horizontal connection (tie-in) towards the flowline, as shown in Fig. 1a. In that embodiment, the second connection element 42 is arranged horizontally. Alternatively, the the flowline connector assembly 40 is oriented for vertical connection (tie-in) towards the flowline, as shown in Fig. 1b. In that embodiment, the second connection element 42 is arranged vertically.

The flowloops 50 transmit fluid flow between the vertical connection at the underside of the subsea tree 10 to the flowline connector assembly 40. The number and type of fluid conduits in the flowloops 50 may vary depending on the required functionality of the connection.

Figure 2 is an illustration of an adapter assembly 100 according to one embodiment. As depicted in Fig. 2, the adapter base 20 holds the first connection element 30, the flowline connector assembly 40 and the flowloops 50 between the first connection element 30 and the flowline connector assembly 40. The first connection element 30 is arranged fixed on the adapter base 20 and the flowline connector assembly 40 is in this embodiment fixed at a side end of the adapter base 20.

Figure 3 is an exploded view of various components of the adapter assembly 100. The adapter base 20 can be a substantially rectangular frame type structure and may include suitable means or holes for connecting the first connection element 30 and the flowline connector assembly 40 to it. The adapter base 20 can have different shapes, and the dimensions of the adapter base 20 may be varied depending on required functionality of flowline connection.

The first connection element 30 is fixed in a vertical orientation on the adapter base 20. The first connection element 30 can then be connected vertically to a corresponding fluid connector 31 (see Fig. 1) at the underside of the subsea tree 10. The transmitting flowloops 50 extend from the first connection element 30 to the flowline connector assembly 40 as illustrated in Figs 1-3.

The flowline connector assembly 40 can have a metal body structure and includes a seond connection element 42 which can be connected to an end portion of a subsea flowline. Further, the flowline connector assembly 40 can include suitable support means or holes for supporting and holding the flowloops 50 from the first connection element 30.

A multiple quick connector (MQC) 48 or stab plate may be provided on the flowline connector assembly 40 for other fluid transfer or other functions, such as control.

The MQC 48 may, for example, be ROV-accessible. Optionally, or additionally, the second connection element 42 may itself be multibore, with the first and second connection elements 30,42 being arranged to transmit different types of fluids between the tree 10 and the subsea flowline.

In one embodiment, the flowline connector assembly 40 comprises a guide pin 46 arranged to assist with the connection of a subsea flowline to the flowline connector assembly 40. The subsea flowline may have an end connector which is lowered from a vessel and requires alignment with the flowline connector assembly 40 before making up the fluid connection. (I.e. before engaging the second connection element 42.) A guide pin 46 on the flowline connector assembly 40 can engage with a corresponding receptcacle on the subsea flowline end connector to align the respective units before making up the fluid connection. Optionally, the subsea flowline may have a guide pin, and a pin receptacle is arranged on the flowline connector assembly 40. The guide pin and receptacle may be substantially vertically arranged, as can be seen in Fig. 2. To aid installation, the receptacle may comprise an inlet section having an increased cross-section, such as a funnel or cone-shaped inlet, to guide the guide pin into the receptacle. The guide pin 46 may thus be inserted into the funnel (not shown here), which provides for easy guiding and positioning of the flowline relative to the flowline connector assembly 40.

Optionally, a guide pin could be placed at a structure under the XT, i.e. on a structure onto which the XT lands. Hoever if sufficient accuracy for connection can be achieved by other means, such as with ROV assistance, a guide pin may not be necessary. The guide pin 46 (or receptacle) may be arranged on a foldable unit 44 as illustrated in Fig. 2. The foldable unit 44 is movable between a first, extended position in which the foldable unit 44 with the guide pin 46 extends outwardly from the base 20 and a second, retracted position in which the foldable unit with the guide pin 46 is retracted towards the base 20. The extended position is illustrated in Fig. 2, while the retracted position is illustrated in Fig. 4.

The foldable unit 44 can, for example, be a frame type structure which can be rotatably fixed to the flowline connector assembly 40, as illustrated. Alternatively, the foldable unit 44 can be a slidable or telescopically extendable structure. In this embodiment, the foldable unit 44, having the guide pin 46, may thereby be folded towards the second connection element 42 as illustrated in Fig. 4, thereby reducing the dimensions of the adapter assembly 100 for easier transportation and installation. For example, during installation through a moon pool on a vessel, the footprint of the assembly and tree may be smaller by retracting the foldable unit 44. Figure 5 illustrates an embodiment of the adapter assembly 100. In Fig. 5, the adapter assembly 100 comprises a frame for holding the subsea tree 10. As depicted in Fig. 5, the adapator base 20 comprises a frame 14 which includes mounting brackets 14a, 14b, 14c and 14d, along the corners of the frame 14. The frame 14 can be a base frame which can be clamped on to the subsea tree 10 through the mounting brackets 14a-14d. The mounting brackets 14a-14d can be a part of the frame 14 and used for fixing or clamping the adapter assembly 100 to the subsea tree 10.

In an embodiment, the frame 14 may be a part of the adapator base 20. It should be noted that the frame 14 may be welded to the adapter base 20, or fixed to it by other means. Alternatively, the frame 14 may be a separate frame which is attached to the subsea tree 10 together with the base 20.

The frame 14 can be attached at the bottom of the subsea tree 10. The mouniting brackets 14a-14d are clamped to the tail structure of the subsea tree 10, to hold the subsea tree as illustrated in Fig. 5 and 6. Optionally, other types of connectors may be used to fix the frame 14 to the tree 10, such as bolts, clamps or the like. The frame 14 allows the subsea tree 10 to stand on its own on a flat surface, such as a vessel deck, with the frame 14 fixed through the mouniting brackets 14a-14d during transportation and installation of the tree 10. Figure 6 illustrates the adapter assembly 100 attached to the subsea tree 10. As depicted in Fig. 6, the adapter assembly 100 is attached at the bottom portion of the subsea tree 10. Thus, the adapter base 20 and the frame 14 holds the subsea tree 10.

The frame 14 extends about at least a part of an outer perimetry of the tree 10, and has a central opening 14’ (see Fig. 5) adjacent to a central part of the underside of the tree 10. This allows the tree to be installed onto a wellhead in the ordinary manner without interference from the frame 14, i.e. where the underside of the tree 10 is fixed onto a wellhead (or other well structure).

The frame 14 may extend around the entire perimetry of the tree 10, as is the case in the embodiment shown in Figs 5 and 6, or it may extend around only parts of the perimetry of the tree 10. For example, a beam section 14e (see Fig. 5) opposite the flowline connector assembly 40 may be omitted such that only two parallel “legs” 14f,14g extend outwardly from the base 20 side to support the tree 10.

In an embodiment, one or more tension rods 16 (see Fig. 6) may be used as a support due to applied tie-in loads during connection of the adapter assembly 100 to the subsea tree 10.

Thus, the adapter assembly 100 is connected at the bottom portion of the subsea tree 10, which facilates the subsea flowline to be connected to the flowline connector assembly 40 monuted on the adapter base 20 of the adapter assembly 100. With the first connection element 30 on the adapter base 20, fixed vertically to the subsea tree 10 and the flowloops 50 which are extended horizontally from the first connection element 30 to the flowline connector assembly 40, the flowline connector assembly 40 can be connected to an end portion of the subsea flowline through the second connection element 42. Access to fluid connectors on the underside (or, in other embodiments, the side) of the tree can therefore be provided more easily for connection to a subsea flowline.

The frame 14 may be configured to provide a stable support for the tree 10 when stored on, for example, a deck of a vessel. This can be achieved by providing the frame 14 with an extension such that the tree 10 can rest entirely on the frame 14 and on the base 20 when transported or stored. This avoids the need for other support structures between the tree 10 and the underlying surface (e.g. purpose- made support structures for the tree 10), for example when transporting it on a vessel.

The adapter assembly 100 of the invention thus provides a simple and convenient way of attaching to a subsea tree 10 that must be connected to and/or mounted on further equipment located on the seabed.

Figure 7 illustrates a subsea production system 200 comprising a plurality of wells. The subsea production system 200 is distributed on a sea floor 66 in the manner known in the art. The system 200 comprises a plurality of subsea trees 10a-g respectively connected to a well. Four trees 10a-d are arranged in a four-slot template 60, whereas three trees 10e-g are arranged individually as satellite trees, each having their own foundation 61-63. The foundations 61-63 may, for example, be a suction anchor base.

Each tree 10a-g feeds the production fluids into a manifold 64 through appropriate conduits (“jumpers”) 67-70, while the manifold 64 again directs the produced fluids to a remote location such as to shore or to a platform via a transport line 65.

The template 60 and the individual foundations 61-63 may have somewhat different requirements with respect to additional flowline connections to the trees 10a-g. Particularly, fluid connectors at the underside of the tree may not be easily accessible in a single-tree foundation 61-63. This may require a different tree design to be used in the satellite wells, compared to the tree design used for those wells in the template 60. (Or may require a more complex or more expensive design of the foundations 61-63.)

Fig. 8 illustrate alternative embodiments of the assembly 100 and tree 10 in terms of the orientation of the connection elements 30,42. In subfigures A-C, there is shown horizontal to vertical connections, in subfigures D-F there is shown horizontal to horizontal connections, in subfigures G-l there is shown vertical to horizontal connections, and in subfigures J-L there is shown vertical to vertical connections.

As illustrated in subfigures A, D, G and J, the adapter base 20 may extend below the tree 10 so that the tree 10 is fully supported on the adapter base 20. Optionally, as illustrated in subfigures B, E, H and K, the adapter base 20 may be provided only partially under the tree 10, or on the side of the tree 10. Subfigures C, F, I and L illustrate various embodiments having an adapter base 20 and a skid 14. By providing an adapter assembly 100 as described in the embodiments above, one may avoid (or reduce) the need for design changes to the trees that are used for example on the single-slot satelites. This allows the same fundamental tree design to be used on all wells, while still having the required connectivity, which is advantageous in terms of installation cost, maintenance, and replacements (for example in that a single spare tree is suitable for all wells).

Figures 9-11 show further perspectives of an assembly 100 with a tree 10 arranged thereon, where the reference numerals correspond to those used in the embodiments described above. Figure 12 illustrates an assembly 100 with a tree 10 arranged thereon, where the reference numerals correspond to those used in the embodiments described above. The assembly 100 as shown in Fig. 12 comprises a diver tie-in as part of the flowline connector assembly 40.

While the invention has been described with reference to the embodiment(s) mentioned above, it is to be understood that modifications and variations can be made without departing from the scope of the present invention, and such modifications and variations shall remain within the field and scope of the invention.