The present application is based upon and claims priority from U.S.

Provisional Patent Application No. 62/367,488 filed on July 27, 2016.

BACKGROUND OF THE DISCLOSURE

The present disclosure is directed to a Christmas tree for a subsea hydrocarbon production system. More particularly, the disclosure is directed to a Christmas tree having a compact configuration which is both lighter and simpler to manufacture than conventional subsea trees.

SUMMARY OF THE DISCLOSURE

In accordance with the present disclosure, a subsea Christmas tree is provided which comprises a valve block having a generally axially extending production bore, a first production branch which extends generally laterally through the valve block from the production bore to a side of the valve block, the first production branch comprising a first end which is connected to the

production bore and a second end which is located on the side of the valve block, and a second production branch which extends generally laterally through the valve block from a first side of the valve block to a second side of the valve block, the second production branch comprising a first end which is located on the first side of the valve block and a second end which is located on the second side of the valve block; at least one flow component which is connected to the valve block, the flow component comprising a first end which is in fluid communication with the second end of the first production branch and a second end which is in fluid communication with the first end of the second production branch; and an outlet hub which is connected to the second end of the second production branch, the outlet hub being connected to or formed integrally with the valve block.

In one aspect of the disclosure, the first production branch extends from the production bore to the first side of the valve block. Thus the second end of the first production branch is located on the first side of the valve block.

In another aspect of the disclosure, the at least one flow component comprises a production flow loop which includes an inlet that is connected to the second end of the first production branch and an outlet that is connected to the first end of the second production branch. In a further aspect of the disclosure, the Christmas tree also comprises at least one of a production flow meter and a production choke which is positioned in the flow loop. For example, the Christmas tree may comprise both a production flow meter and a production choke positioned in series in the production flow loop.

In yet another aspect of the disclosure, the production flow meter and/or the production choke form part of a flow module which is connected to the valve block. In this embodiment, the flow module may be retrievable independently of the valve block.

In one aspect of the disclosure, the inlet and outlet of the production flow loop are respectively connected to the second end of the first production branch and the first end of second production branch through a single multi-bore hub and connector arrangement.

In another aspect of the disclosure, the inlet of the production flow loop is connected to the second end of the first production branch through a first hub and connector arrangement and the outlet of the production flow loop is connected to the first end of the second production branch through a second hub and connector arrangement.

In a further aspect of the disclosure, the Christmas tree further comprises a production master valve which is positioned in the production bore below the first production branch; a production wing valve which is positioned in the first production branch; and a production shut down valve which is positioned in the second production branch . In this embodiment, the production master valve, the production wing valve and the production shut down valve are mounted in the valve block.

In another aspect of the disclosure, the valve block further comprises a generally axially extending annulus bore and an annulus outlet which extends through the valve block from the annulus bore. In this embodiment, the Christmas tree may also comprise an annulus master valve which is positioned in the annulus bore below the annulus outlet, and an annulus wing valve which is positioned in the annulus outlet. Furthermore, the annulus master valve and the annulus wing valve may be mounted in the valve block.

In a further aspect of the disclosure, the valve block further comprises a crossover bore which extends through the valve block from one of the production bore and the first production branch to one of the annulus bore and the annulus outlet. In this embodiment, the Christmas tree may also comprise a crossover valve which is positioned in the crossover bore. Furthermore, the crossover valve may be mounted in the valve block.

The present disclosure is also directed to a subsea Christmas tree comprising a valve block which comprises a production bore, a first production branch in fluid communication with the production bore, and a second production branch; at least one flow component which is connected to a first side of the valve block, the at least one flow component being in fluid communication with the first production branch and the second production branch; and an outlet hub which is connected to a second side of the valve block, the outlet hub being in fluid communication with the second production branch.

In one aspect of the disclosure,, the first production branch extends from the production bore to the first side of the valve block and the second production branch extends from the first side of the valve block to the second side of the valve block.

In another aspect of the disclosure, the at least one flow component comprises at least one of a production flow loop, a production flow meter and a production choke.

In yet another aspect of the disclosure, the at least one flow component forms part of a flow module which is connected to the valve block.

In a further aspect of the disclosure, the flow module is retrievable independently of the valve block.

In another aspect of the disclosure, the first production branch and the second production branch are connected to the flow module through a single multi-bore hub and connector arrangement.

In yet another aspect of the disclosure, the first production branch is connected to the flow module through a first hub and connector arrangement and the second production branch is connected to the flow module through a second hub and connector arrangement.

In a further aspect of the disclosure, the Christmas tree further comprises a production master valve which is positioned in the production bore below the first production branch; a production wing valve which is positioned in the first production branch; and a production shut down valve which is positioned in the second production branch. Thus, the production wing valve and the production shut down valve are mounted in the valve block.

In another aspect of the disclosure, the valve block further comprises a generally axially extending annulus bore and an annulus outlet which extends through the valve block from the annulus bore. In this embodiment, the Christmas tree may further comprise an annulus master valve which is positioned in the annulus bore below the annulus outlet, and an annulus wing valve which is positioned in the annulus outlet. Furthermore, the annulus master valve and the annulus wing valve may be mounted in the valve block.

In a yet another aspect of the disclosure, the valve block further comprises a crossover bore which extends through the valve block from one of the production bore and the first production branch to one of the annulus bore and the annulus outlet. In this embodiment, the Christmas tree may also comprise a crossover valve which is positioned in the crossover bore. Furthermore, the crossover valve may be mounted in the valve block.

The present disclosure is also directed to a method for controlling the flow of fluid from a hydrocarbon well. In one aspect, the method comprises the steps of mounting a valve block over an upper end of the well; directing the fluid through the valve block to a flow component which is connected to the valve block; directing the fluid through the flow component; and then directing the fluid back through the valve block to an outlet hub which is coupled to the valve block.

In an aspect of the disclosure, the flow component may comprise at least one of a production flow loop, a production flow meter and a production choke.

Thus, it may be seen that a novel and beneficial feature of the compact tree of the present disclosure is the incorporation of a second production branch through which the production fluid re-enters the valve block after it passes through the flow module. Thus, rather than utilizing external flow loops to route the production fluid to a tree outlet hub, the production fluid is routed to another side of the tree via the second production branch. The elimination of external flow loops minimizes the weight of the tree and simplifies the manufacturing process (e.g., welding) associated with installing flow loops on a subsea tree. Also, the outlet hub is preferably directly attached to the valve block so as to transfer at least a portion of the loads associated with an attached flowline through the structure of the valve block, instead of through a separate fabricated structure which is attached to the tree, thus reducing the weight, size and overall cost of the tree assembly.

These and other objects and advantages of the present disclosure will be made apparent from the following detailed description, with reference to the accompanying drawings. In the drawings, the same reference numbers may be used to denote similar components in the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic representation of a prior art vertical Christmas tree;

Figure 2 is a schematic representation of a first embodiment of the

Christmas tree of the present disclosure;

Figure 3 is a schematic representation of a second embodiment of the Christmas tree of the present disclosure;

Figure 4 is a schematic representation of a third embodiment of the Christmas tree of the present disclosure;

Figure 5 is a perspective view of another embodiment of the Christmas tree of the present disclosure;

Figure 6 is another perspective view of the embodiment of the Christmas tree shown in Figure 5; and

Figs. 7-18 are three dimensional depictions of another embodiment of the Christmas tree of the present disclosure taken from various angles.

DETAILED DESCRIPTION

As background for the present disclosure, an example of a prior art Christmas tree will be described with reference to Figure 1 . The prior art tree, generally 10, comprises part of a subsea hydrocarbon production system that also includes a wellhead 12 which is positioned at the upper end of a well bore 14, a tubing hanger 16 which is landed in the wellhead, and a production tubing string 18 which extends from the tubing hanger into the well bore. The tubing hanger comprises an axially extending production bore 20 which is connected to the tubing string 18 and an axially extending annulus bore 22 which is connected to a production annulus 24 surrounding the tubing string.

The tree 10 is installed on the top of the wellhead 12 and is locked thereto using a conventional hydraulic connector 26. The tree 10 includes a production bore 28 which is connected to the tubing hanger production bore 20 and an annulus bore 30 which is connected to the tubing hanger annulus bore 22. The production bore 28 is connected to a lateral production outlet 32 which in turn is connected via a production flow loop 34 to a flowline connector 36. Similarly, the annulus bore 30 is connected to a lateral annulus outlet 38 which in turn is connected via an annulus flow loop 40 to the flowline connector 36. The flowline connector 36 connects the production flow loop 34 to a production flowline 42 and the annulus flow loop 40 to an annulus flowline 44. The production flowline 42 and the annulus flowline 44 may in turn be connected to, e.g., a conventional bridge module or manifold module (not shown). Also, the production outlet 32 and the annulus flow loop 40 may be connected via a crossover line 46.

The tree 10 comprises a number of valves for controlling fluid flow through the hydrocarbon production system. In particular, a production swab valve ("PSV") 48 is located in the production bore 28 above the production outlet 32, an upper production master valve ("UPMV") 50 is located in the production bore below the production outlet, a lower production master valve ("LPMV") 52 is located in the production bore below the UPMV, and a production wing valve ("PWV") 54 is located in the production outlet between the production bore and the production flow loop 34. In addition, an annulus swab valve ("ASV") 56 is located in the annulus bore 30 above the annulus outlet 38, an annulus master vale ("AMV") 58 is located in the annulus bore below the annulus outlet, an annulus wing valve ("AWV") 60 is located in the annulus outlet between the annulus bore and the annulus flow loop 40, and a crossover valve ("XOV") 62 is located in the crossover line 46 between the production outlet and the annulus flow loop.

During the production mode of operation of the tree 10, the UPMV 50, LPMV 52 and PWV 54 are opened and the PSV 48 and XOV 62 are closed. In this configuration, the produced fluid will be directed from the production bore 28 into the production outlet 32 and from there into the production flow loop 34 and the production flow line 42. In addition to the PSV 48, a tree cap 64 or similar device is locked and sealed to the top of the tree 10 to provide a second pressure barrier between the production bore 28 and the environment. The UPMV 50 and the LPMV 52 typically remain open except in the event of an emergency, when the well is shut down, or when needed to provide a pressure barrier between the well bore and the environment, such as when the tree cap 64 is removed in preparation for the installation of intervention equipment. A first embodiment of the ultra-compact Christmas tree of the present disclosure is shown in Figure 2. The tree of this embodiment, generally 100, comprises a valve block 102 which is configured to be mounted on a wellhead 104 (or tubing head or similar such component). The wellhead 104, which is located at the top of a well bore, supports a tubing hanger 106 which is connected to the top of a production tubing string 108 that extends into the well bore. The tubing hanger includes a generally axially extending production bore 1 10 which is connected to the tubing string 108 and a generally axially extending annulus bore 1 12 which communicates with a production tubing annulus 1 14 surrounding the tubing string.

The tree 100 comprises a production bore 1 16 which extends axially through the valve block 102 and is connected to the tubing hanger production bore 1 10, a production outlet (or "first production branch") 1 18 which extends laterally through the valve block as is connected to the production bore, and a production branch (or "second production branch") 120 which extends laterally through the valve block 102. The production branch 120 is not limited to the configuration and arrangement shown in Fig. 2 and can, for instance, pass at oblique angles through the valve block 102 and exit at other points of the valve block 102, including other sides of the valve block 102. The tree includes a number of valves for controlling fluid flow through the valve block 102, such as a production master valve ("PMV") 122 which is located in the production bore 1 16 below the production outlet 1 18, a production wing valve ("PWV") 124 which is located in the production outlet, a production swab valve ("PSV") 126 which is located in the production bore above the production outlet, and an optional production shut down valve ("PSDV") 127 which is located in the production branch 120.

In one embodiment of the disclosure, the PMV 122 and PWV 124 are failsafe-closed, remotely (such as electrically or hydraulically) actuated, and preferably gate valves, although other types of valves, such as ball valves, may provide suitable alternatives. The PSV 126 and PSDV 127 may in one embodiment comprise manually (such as ROV) operated valves, but in other embodiments the PSV and/or the PSDV may be fail-safe-closed, hydraulically or electrically operated valves, similar to the PMV 122 and the PWV 124. While the production bore 116 may be located at the centerline of the valve block 102, the actuators for the valves (not shown) may extend from different sides of valve block 102. Thus, the physical size of the tree 100 can be minimized.

The tree 100 also includes one or more flow components which may in an illustrative embodiment of the disclosure be incorporated into a flow module 128 which is positioned on a side of the valve block 102. As depicted, the flow components include a production loop 130 having an inlet 132 which is connected to the production outlet 1 18 and an outlet 134 which is connected to the production branch, as well as a production flow meter 138, which may comprise a multi-phase or a single phase flow meter, and a production choke 140 for regulating the production flow and balancing the production flow with the production flow from other trees that may be manifolded together with the tree 100. The tree 100 is not limited, however, to the flow components and their associated arrangement shown in Figure 2.

In the production mode of operation of the tree 100, the PMV 122 and the PWV 124 will be in the open position and the PSV 126 will be in the closed position. Thus, production fluids entering the valve block 102 through production bore 1 16 will be directed into the production outlet 1 18, through the flow module 128, and back through the production branch 120. From the production branch 120, the production fluids will be directed into a flowline (not shown) which is connected in a conventional manner to an outlet hub 136 located on a side of the valve block 102.

In the illustrative embodiment of the disclosure shown in Figure 2, the flow components positioned at the side of the valve block 102, such as the flow meter 138 and the choke 140, are incorporated into the flow module 128, which is at least partially responsible for monitoring and controlling the production flow through the tree 100. The flow module 128 may be an independently-retrievable module which is attached to valve block 102 using one or more hubs and connectors, or it may be permanently mounted to or even formed integrally with the valve block 102. In the embodiment of the disclosure shown in Figure 2, for example, the flow module 128 is connected to the valve block using a

conventional multi-bore hub and connector arrangement 142. Although a horizontally connected flow module 128 is shown in Figure 2, the flow module may alternatively be attached to the tree using a vertically-oriented multi-bore hub. If the flow module 128 is permanently mounted to or formed integrally with the valve block 102, then the flow meter 138 and/or the choke 140 may be or include retrievable components to allow them to be repaired or serviced without necessitating the retrieval of the entire tree 100 - although the tree will ideally be sufficiently light to be retrieved without the need for extensive topside equipment. In that case, the entire tree 100 may be retrieved if any of its components need servicing.

As is conventional with vertical-type Christmas trees, the tree 100 also includes an annulus bore 144 which extends through the valve block 102 and is connected to the tubing hanger annulus bore 1 12, an annulus outlet 146 which extends through the valve block and is connected to the annulus bore, and a crossover bore 148 which extends through the valve block between the annulus bore and the production bore (or between the annulus bore and the production outlet, or between the annulus outlet and the production bore, or between the annulus outlet and the production outlet). Together with the tree production bore 1 16, the tubing hanger production bore 1 10, the production tubing 108 and the production annulus 114, the annulus bore 144, the annulus outlet 146 and the crossover bore 148 allow for fluid circulation during well completion and shut-in operations.

In the embodiment of the disclosure shown in Figure 2, the tree 100 includes an annulus master valve ("AMV") 150 which is located in the annulus bore 144 below the annulus outlet 146, an annulus wing valve ("AWV") 152 which is located in the annulus outlet, an annulus swab valve ("ASV") 154 which is located in the annulus bore above the annulus outlet, and a crossover valve ("XOV") 156 which is located in the crossover passage 148. As with the production valves described above, the annulus valves may be hydraulically, electrically or manually actuated. In one embodiment of the disclosure, the AMV 150, the AWV 152 and the XOV 156 are remotely actuated (hydraulic or electric) valves and the ASV 154 is a manually (ROV) actuated valve. Similar to the production valve actuators, the annulus valve actuators (not shown) may be located on different sides of the valve block 102.

It should be noted that, although the compact tree 100 is shown with a particular arrangement of production and annulus passages and valves, any of the compact tree embodiments described herein could comprise different configurations of production and annulus passages and different types of valves and closure devices, depending on the application for which the compact tree is designed. In this regard, reference is made to ANSI/API Specification 17D, "Design and Operation of Subsea Production Systems - Subsea Wellhead and Tree Equipment" (2013), which is hereby incorporated herein by reference, for examples of different tree configurations which the compact tree of the present disclosure may be designed to comprise.

Another embodiment of the ultra-compact tree of the present disclosure is shown in Figure 3. The compact tree of this embodiment, generally 100a, is similar in most respects to the compact tree 100 described above. In the present embodiment, however, the flow module 128 is mounted directly to the valve block 102 and the inlet 132 and outlet 134 of the production loop 130 are directly connected to the production outlet 1 18 and production branch 120, respectively. As with the tree 100a, the flow module 128 may be independently-retrievable, permanently mounted to or formed integrally with the valve block 102, and the flow meter 138 and/or the choke 140 may be or include retrievable components to allow them to be repaired or serviced without necessitating the retrieval of the entire tree 100a.

A third embodiment of the compact tree of the present disclosure is shown in Figure 4. The compact tree of this embodiment, generally 100b, is similar in most respects to the compact tree 100 described above. In the present embodiment, however, the flow module 128 is connected to the valve block 102 via conventional first and second hubs and connector arrangements 158, 160. As shown in Figure 4, the first hub and connector arrangement 158 connects the production outlet 1 18 with the inlet 132 of the production loop 130, and the second hub and connector arrangement 160 connects the production branch 120 with the outlet 134 of the production loop. In this embodiment, as well as in the embodiment of Figure 2, the hubs and connectors may be oriented vertically to facilitate the retrieval and installation of the flow module 128 from a surface vessel using a wireline or cable. Also, as with the previous embodiments, the flow module 128 may be independently-retrievable, permanently mounted to or formed integrally with the valve block 102, and the flow meter 138 and/or the choke 140 may be or include retrievable components to allow them to be repaired or serviced without necessitating the retrieval of the entire tree 100b. As an alternative to the flow module 128 described above, the flow meter 138 and/or the choke 140 (and/or any other flow monitoring and/or flow control component) may be mounted in respective housings which are connected to or formed integrally with the valve block 102 using conventional means. In such an embodiment, the production loop 130 would be routed from the production outlet 1 18, through the component or components, and then back to the production branch 120.

A novel and beneficial feature of the compact tree of the present disclosure is the incorporation of the production branch 120 through which the production fluid re-enters the valve block 102 after it passes through the flow module 128. Rather than utilizing external flow loops to route the production fluid to a tree outlet hub, the production fluid is routed to another side of the tree via the production branch 120. The elimination of external flow loops minimizes the weight of the tree and simplifies the manufacturing process (e.g., welding) associated with installing flow loops on a subsea tree. Also, the outlet hub 136 is preferably directly attached to the valve block 102 so as to transfer at least a portion of the loads associated with an attached flowline through the structure of the valve block, instead of through a separate fabricated structure which is attached to the tree, thus reducing the weight, size and overall cost of the tree assembly. Similar to hubs 142, 158 and 160, outlet hub 136 may also be a horizontal hub, as shown in the Figures, or a vertically-oriented hub (not shown).

Referring also to Figures 5 and 6, the ultra-compact tree of the present disclosure also comprises a conventional subsea connector 160 for securing the valve block 102 to the wellhead 104, and a mandrel 162 which is connected to or formed integrally with the valve block 102 and extends from the top of the tree to provide vertical access to the production bore 1 16 and the annulus bore 144. The mandrel 162 may include both internal and external locking profiles to allow installation and service equipment to attach and seal to the top of tree 100. The tree 100 may also include additional valves, such as chemical injection valves 164, which in one embodiment are manually (e.g., ROV) operated valves but may also be remotely actuated (e.g., electrically or hydraulically) valves.

Figures 7-18 are three dimensional depictions of an embodiment of the ultra-compact tree 100 taken from various views to show certain features of the present disclosure. Figure 8 is a view of the tree 100 showing the valve block 102, the outlet hub 36, the connector 160, the mandrel 162 and the actuators for certain of the production and annulus valves. In Figure 8, the valve actuators are shown to extend from generally opposite sides of the valve block 102. Figure 9 is a view of the tree 100 showing the flow module 128 connected to the valve block 102 via the hub and connector 142. Figure 9 also shows the outlet hub 136, which in this embodiment of the tree 100 is located generally diametrically opposite the flow module 128, and the actuators for certain of the production and annulus valves. Figures 10-12 are additional views of the tree 100, and in particular the outlet hub 36 and the actuators for certain of the production and annulus valves. Figures 13-15 are views of the flow module 128, including the flow meter 138 and the choke 140. Figure 15 also shows the hub and connector 142 for connecting the flow module 128 to the valve block 102.

Figures 16 and 17 are views of the tree 100 showing the valve block 102 and the actuators for certain of the production and annulus valves. The actuators for the PMV 122 and the AMV 150 may comprise, for example, a hydraulic actuator of the type disclosed in applicant's co-pending International Patent Application No. PCT/BR2015/050033, published on October 1 , 2015 under International Publication No. WO 2015/143524 A2, which is hereby incorporated herein by reference. Moreover, these actuators may comprise a composite return spring 166 of the type described in applicant's co-pending International Patent Application No. PCT/BR2015/050255 filed on December 14, 2015, which is hereby incorporated herein by reference.

It should be recognized that, while the present disclosure has been presented with reference to certain embodiments, those skilled in the art may develop a wide variation of structural and operational details without departing from the principles of the disclosure. For example, the various elements shown in the different embodiments may be combined in a manner not illustrated above. Therefore, the following claims are to be construed to cover all equivalents falling within the true scope and spirit of the disclosure.