Abstract:
A subsea wellhead assembly positions a flow module between an outboard flowline of a subsea tree and a tubing hanger spool flowline. The subsea production assembly includes a wellhead, a tubing hanger spool disposed on the wellhead, and a subsea tree disposed on the tubing hanger spool. Production fluid may flow from the wellhead through the tubing hanger spool, and then through the tree. A tubing hanger spool frame mounts to and extends laterally from the tubing hanger spool and supports a downstream flowline having an upward facing hub. A tree frame mounts to and extends laterally from the subsea tree and supports an upstream flowline having an upward facing hub. A flow module having downward facing flowlines that couple to the hubs so that the weight of the flow module is distributed between the frames of the tubing hanger spool and the subsea tree.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates in general to subsea production apparatuses and, in particular, to an improved flow module placement between a subsea tree and a tubing hanger spool. 
         [0003]    2. Brief Description of Related Art 
         [0004]    A conventional subsea wellhead assembly includes a wellhead housing that supports one or more casing hangers located at upper ends of strings of casing extending into the well. A tubing hanger spool or “THS” is landed on the wellhead assembly. A production tree or “tree” is landed on the THS for controlling the production of well fluids. The tree usually carries a choke and valves to control the flow of well fluids and sensors to monitor the flow of well fluids. 
         [0005]    The subsea tree will control the flow of hydrocarbons out of the wellhead, and direct the hydrocarbons to associated equipment, such as manifolds, flowlines, and the like for further operation. Subsea trees may have a flow module, such as a choke bridge module, manufactured as an integral component of the subsea tree and used to control fluid flow out from the tree to external components. Generally, these flow modules are installed along with the subsea tree, but positioned within the tree so that the flow module may be retrieved without having to retrieve the full tree. Portions of the tree, such as flow meters, or chokes that control the flow of hydrocarbons through the outboard flowlines, may wear and fatigue at rates faster than the remaining portions of the subsea tree. Using a flow module containing these components puts more of the retrievable portions of the tree on a recoverable module that allows you to retrieve those portions for repair without disturbing the well completion and associated barrier valves. 
         [0006]    In some vertical tree installations, the subsea trees sit on top of a tubing hanger spool. An outboard flowline then runs from the flow module on the subsea tree to a tubing hanger spool flowline. The tubing hanger spool flowline then runs to external equipment such as a manifold or a facility. This outboard flowline from the flow module is generally quite long and must wind through the subsea tree in order to connect with the tubing hanger spool flowline. As a result, there is a significant pressure drop through the outboard flowline from the flow module. In addition, the longer outboard flowline from the flow module leads to a greater heat loss from the well fluid into the surrounding environment. This can lead to an increase in the viscosity of the well fluid. An increased well fluid viscosity necessitates additional work input to move the fluid through the outboard flowline from the flow module. Furthermore, the length of the outboard flowline from the flow module increases the total area from which leaks can form; thus the longer outboard flowline from the flow module increases the likelihood of leak development. The length of the outboard flowline from the flow module may also cause an increase in the cost of production. This results from both the increase in the amount of material needed to construct the line and the increased labor cost to construct the lengthy outboard flowline from the flow module. Thus, there is a need for an improved flow module placement between a subsea tree and a tubing hanger spool that overcomes these problems. 
       SUMMARY OF THE INVENTION 
       [0007]    These and other problems are generally solved or circumvented, and technical advantages are generally achieved, by preferred embodiments of the present invention that provide an improved flow module placement between a subsea tree and a tubing hanger spool, and a method for the same. 
         [0008]    In accordance with an embodiment of the present invention, a subsea production assembly is disclosed. The subsea production assembly includes a wellhead having an axis, and a tubing hanger spool disposed on the wellhead axially above the wellhead so that production fluid may flow from the wellhead through the tubing hanger spool. A tubing hanger spool frame mounts to and extends laterally from the tubing hanger spool. A downstream flowline having an upward facing hub is supported by the tubing hanger spool frame. The assembly includes a subsea tree disposed on the tubing hanger spool axially above the tubing hanger spool so that production fluid may flow from the tubing hanger spool through the tree. The tree has a tree frame mounted to and extending laterally from the subsea tree. An upstream flowline is supported by the tree frame and connected to the tree, the upstream flowline having an upward facing hub. The assembly includes a flow module having downward facing flowlines that couple to the hubs, such that flow from the tree passes in a flow path from the upstream flowline through the flow module and the downstream flowline. The weight of the flow module is distributed between the frame of the tubing hanger spool and the frame of the subsea tree. 
         [0009]    In accordance with another embodiment of the present invention, another subsea production assembly is disclosed. The subsea production assembly includes a wellhead having an axis, and a tubing hanger spool disposed on the wellhead axially above the wellhead so that production fluid may flow from the wellhead through the tubing hanger spool. A tubing hanger spool frame mounts to and extends laterally from the tubing hanger spool. A downstream flowline having an upward facing hub is supported by the tubing hanger spool frame, the upward facing hub secured to the tubing hanger spool frame. A subsea tree is disposed on the tubing hanger spool axially above the tubing hanger spool so that production fluid may flow from the tubing hanger spool through the tree. A tree frame mounts to and extends laterally from the subsea tree. An upstream flowline is supported by the tree frame and connects to the tree, the upstream flowline having an upward facing hub secured to the tree frame. The assembly includes a choke bridge module having downward facing flowlines that couple to the hubs, such that flow from the tree passes in a flow path from the upstream flowline through the choke bridge module and the downstream flowline. The weight of the choke bridge module is distributed between the frame of the tubing hanger spool and the frame of the subsea tree. The hub of the downstream flowline is at a lower elevation than the hub of the upstream flowline. The tree frame includes a hub supporting portion that supports the hub of the upstream flowline that is at a higher elevation than, but not directly above, the tubing hanger spool frame. The tubing hanger spool frame includes a hub supporting portion that supports the hub of the downstream flowline and is at a lower elevation than, but not directly below, the tree frame. Any weight transferred to the upward facing hubs by the choke bridge module is further transferred to the tubing hanger spool frame and the subsea tree frame. 
         [0010]    In accordance with yet another embodiment of the present invention, another subsea production assembly is disclosed. The subsea production assembly includes a wellhead having an axis, and a tubing hanger spool disposed on the wellhead axially above the wellhead so that production fluid may flow from the wellhead through the tubing hanger spool. A tubing hanger spool frame mounts to and extends laterally from the tubing hanger spool. A downstream flowline having an horizontally facing hub is supported by the tubing hanger spool frame, the horizontally facing hub secured to the tubing hanger spool frame. The assembly includes a subsea tree disposed on the tubing hanger spool axially above the tubing hanger spool so that production fluid may flow from the tubing hanger spool through the tree. A tree frame mounts to and extends laterally from the subsea tree. An upstream flowline is supported by the tree frame and connects to the tree, the upstream flowline having an horizontally facing hub secured to the tree frame. The downstream flowline horizontally facing hub and the upstream flowline horizontally facing hub are on a same side of and face horizontally away from the tree. The assembly includes a choke bridge module having downward facing flowlines with horizontal terminations that couple to the hubs, such that flow from the tree passes in a flow path from the upstream flowline through the choke bridge and the downstream flowline. The weight of the choke bridge module is distributed between the frame of the tubing hanger spool and the frame of the subsea tree. The hub of the downstream flowline is at a lower elevation than the hub of the upstream flowline. The tree frame includes a hub supporting portion that supports the hub of the upstream flowline that is at a higher elevation than, but not directly above, the tubing hanger spool frame. The tubing hanger spool frame includes a hub supporting portion that supports the hub of the downstream flowline and is at a lower elevation than, but not directly below, the tree frame. Any weight transferred to the horizontally facing hubs by the choke bridge module is further transferred to the tubing hanger spool frame and the subsea tree frame. 
         [0011]    In accordance with still another embodiment of the present invention, a method for assembling a subsea production assembly is disclosed. The method begins by landing and setting a tubing hanger spool on a subsea wellhead, the tubing hanger spool including a tubing hanger spool flowline having a tubing hanger spool hub at a first location. The method then runs, lands, and sets a subsea tree on the tubing hanger spool, the subsea tree including a subsea tree flowline having a subsea tree hub located proximate to the first location. The method then runs, lands, and sets a flow module on the subsea tree and the tubing hanger spool, such that the weight of the flow module is partially supported by the subsea tree and partially supported by the tubing hanger spool. 
         [0012]    An advantage of a preferred embodiment is a shorter flow path from the flow module to external production devices. This leads to a reduction in the pressure drop across the system, and a reduction in the amount of heat lost through the outboard flowlines. In addition, the shorter flowline provides fewer opportunities for leaks to occur. Still further, the disclosed embodiments allow for production of the subsea production assembly at a reduced cost. This arises as a result of the significant decrease in the amount of material needed to connect the flow module to the external production devices, and a decrease in the man-hours needed to construct the tree and flow module. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, are attained, and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof which are illustrated in the appended drawings that form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and are therefore not to be considered limiting of its scope as the invention may admit to other equally effective embodiments. 
           [0014]      FIG. 1  is a schematic representation of an embodiment of the present invention. 
           [0015]      FIG. 2  is a schematic top view representation of the embodiment of  FIG. 1 . 
           [0016]      FIG. 3  is a schematic representation of an alternative embodiment of the present invention. 
           [0017]      FIG. 4  is a schematic top view representation of the embodiment of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings which illustrate embodiments of the invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout, and the prime notation, if used, indicates similar elements in alternative embodiments. 
         [0019]    In the following discussion, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be obvious to those skilled in the art that the present invention may be practiced without such specific details. Additionally, for the most part, details concerning rig operation, well drilling, downhole well completion, and the like have been omitted inasmuch as such details are not considered necessary to obtain a complete understanding of the present invention, and are considered to be within the skills of persons skilled in the relevant art. 
         [0020]    Referring to  FIG. 1 , a subsea production system  11  includes a subsea wellhead  13 , a tubing hanger spool  15 , a subsea tree  17 , and a flow module  19 . Subsea wellhead  13  is disposed within a wellbore located at a sea floor. Tubing hanger spool  15  is positioned on subsea wellhead  13  and is coupled to subsea wellhead  13  such that a tubing hanger (not shown) and an associated tubing string (not shown) may be suspended from tubing hanger spool  15 . The tubing string may run down into the wellbore to a production zone to serve as a production flowline for hydrocarbons produced from the subsea strata. 
         [0021]    Tubing hanger spool  15  may include a tubing hanger spool frame  35  supporting tubing hanger spool  15  and a tubing hanger spool flowline  31 , so named due to its proximity to tubing hanger spool  15 . Tubing hanger spool flowline  31  may couple to additional flowlines  49  that in turn couple to subsea manifolds, facilities (not shown), or the like. An opposite end of tubing hanger spool flowline  31  may terminate at an upward facing hub  33  proximate to an exterior of tubing hanger spool frame  35 . Frame  35  is supported by tubing hanger spool  15  and extends laterally from tubing hanger spool  15 . A person skilled in the art will understand that upward facing hub  33  may comprise a male or female piping connection of any suitable variety to receive an outboard flowline  39  of flow module  19 . 
         [0022]    Subsea tree  17  lands on and secures to tubing hanger spool  15  such that hydrocarbons produced from the wellbore may flow from tubing hanger spool  15  into the flowlines of subsea tree  17 . Subsea tree  17  may include a series of valves  21  that may operate to direct or shut off the flow of fluid through subsea production system  11 . Subsea tree  17  includes a tree frame  23 , shown schematically in  FIG. 1 . Tree frame  23  is supported by and extends laterally from subsea tree  17 . Subsea tree  17  also includes an inboard flowline  25 . Inboard flowline  25  may extend from valves  21  to a point on tree frame  23  proximate to an exterior of subsea tree  17 . Outboard flowline  25  may terminate in an upward facing hub  27 . Upward facing hub  27  may comprise a male or female piping connection adapted to receive an inboard flowline  29  of flow module  19 . Preferably, upward facing hub  33  and upward facing hub  27  may be located on the same exterior side of subsea production system  11 . Upward facing hub  27  is located a higher elevation than upward facing hub  33  is this embodiment. In other embodiments, upward facing hub  27  may be at a lower elevation than upward facing hub  33  or at the same elevation as upward facing hub  33 . 
         [0023]    Flow module  19  may land on upward facing hub  27  and upward facing hub  33  such that inboard flowline  29  of flow module  19  may couple to upward facing hub  27  and an outboard flowline  39  of flow module  19  may couple to upward facing hub  33 . Flow module  19  may couple to both tree frame  23  and tubing hanger spool frame  35  such that a portion of the weight of flow module  19  may be supported by tree frame  23 , and a portion of the weight of flow module  19  may be supported by tubing hanger spool frame  35 . 
         [0024]    During subsea assembly, tubing hanger spool  15  along with tubing hanger spool frame  35  and tubing hanger spool flowline  31 , may be run down in a conventional manner, landed, and set on wellhead  13 . Similarly, subsea tree  17  and valves  21  along with tree frame  23  and inboard flowline  25  may be run in a conventional manner, landed, and set on tubing hanger spool  15 . Preferably, upward facing hub  33  and upward facing hub  27  may be in proximity to one another. Flow module  19  may then be run to subsea production system  11  in a separate trip. Inboard flowline  29  of flow module  19  may be connected to upward facing hub  27 , and outboard flowline  39  of flow module  19  may be connected to upward facing hub  33 . Thus, increased proximity of upward facing hub  27  and upward facing hub  33  may reduce the length of the inboard and outboard flowlines  29 ,  39  of flow module  19 . 
         [0025]    Referring to  FIG. 2 , wellhead  13 , tubing hanger spool  15 , and subsea tree  17  are all coaxial with an axis  12  of wellhead  13 . Tree frame  23  is positioned axially over tubing hanger spool frame  35 . Flow module  19  may be run to the subsea location and positioned to land partially on tree frame  23  and partially on tubing hanger spool frame  35  as shown. Preferably, tree frame  23  may include a frame portion  41  extending beyond an edge  43  of tubing hanger spool frame  35 . Frame portion  41  may be in the same plane as tree frame  23 . Similarly, tubing hanger spool frame  35  may include a frame portion  45  extending beyond an edge  47  of tree frame  23 . Frame portion  45  may be in the same plane as tubing hanger spool frame  35 . Preferably, frame portion  41  of tree frame  23  may extend from tree frame  23  in a plane parallel to frame portion  45  of tubing hanger spool frame  35 . Frame portion  41  may be axially above, but may not be directly over frame portion  45 . In this manner, a portion of flow module  19  may extend below tree frame  23  to land on tubing hanger spool frame  35 . Flow module  19  may secure to both tree frame  23  and tubing hanger spool frame  35  at frame portion  41  and frame portion  45 , respectively. Thus, flow module  19  is supported by both tree frame  23  and tubing hanger spool frame  35 . A person skilled in the art will understand that tree frame  23  and tubing hanger spool frame  35  may be formed of any suitable material. For example, both tree frame  23  and tubing hanger spool frame  35  may be constructed of steel beams, plates, or the like. 
         [0026]    As shown in  FIG. 2 , upward facing hub  27  of inboard flowline  25  may terminate on frame portion  41  of tree frame  23 . Upward facing hub  27  may be positioned so that inboard flowline  29  of flow module  19  may stab into upward facing hub  27  during landing of flow module  19 . Similarly, upward facing hub  33  of tubing hanger spool flowline  31  may terminate on frame portion  45  of tubing hanger spool frame  35 . Upward facing hub  33  may be positioned so that outboard flowline  39  of flow module  19  may stab into upward facing hub  33  during landing of flow module  19 . By configuring the position of flow module  19  as illustrated herein, a significant reduction in the length of the combined outboard flowline  39  from flow module  19  and tubing hanger spool flowline  31  to a terminal of additional flowlines  49  for connection to external production devices, such as a manifold or other subsea device, is accomplished. This provides a significant advantage over prior art designs that necessitated that the outboard flowline  39  must wind through subsea tree  17  before connecting to tubing hanger spool flowline  31 . 
         [0027]    Subsea production system  11  of  FIG. 1  may include horizontally facing hubs  34 ,  28  in place of upwardly facing hubs  33  and  27 , respectively, as shown in  FIG. 3 . As illustrated in  FIG. 3 , horizontally facing hub  34  may be located at an end of tubing hanger spool flowline  31  and be adapted to receive outboard flowline  39 . A person skilled in the art will understand that horizontally facing hub  34  may comprise a male or female piping connection of any suitable variety to receive outboard flowline  39  of flow module  19 . Preferably, tubing hanger spool flowline  31  will terminate horizontally on tubing hanger spool frame  35  so that the terminus of tubing hanger spool flowline  31  faces outward away from tubing hanger spool  15 . Horizontally facing hub  28  may comprise a male or female piping connection adapted to receive inboard flowline  29  of flow module  19 . Preferably, inboard flowline  25  will terminate horizontally on tree frame  23  so that the terminus of inboard flowline  25  faces outward away from subsea tree  17 . In addition, horizontally facing hub  34  and horizontally facing hub  28  may be located on the same exterior side of subsea production system  11 . As shown, horizontally facing hub  28  is located a higher elevation than horizontally facing hub  34  is this embodiment. A person skilled in the art will understand that horizontally facing hub  28  may be located at the same elevation as horizontally facing hub  34  or at a lower elevation than horizontally facing hub  34 . In the illustrated embodiment, outboard flowline  39  and inboard flowline  29  will have horizontal terminations so that ends proximate to horizontally facing hubs  34 ,  28  may be coupled to horizontally facing hubs  34 ,  28  to allow for fluid flow between inboard flowline  25  and inboard flowline  29 , and outboard flowline  39  and tubing hanger spool flowline  31 . Preferably, horizontally facing hubs  34 ,  28  face the same horizontal direction and the terminations of outboard and inboard flowlines  39 ,  29  of flow module  19  face in the same horizontal direction, but opposite that of horizontally facing hubs  34 ,  28  to allow flowlines  39 ,  29  to stab into hubs  34 ,  28 . 
         [0028]    As shown in  FIG. 4 , horizontally facing hub  28  of inboard flowline  25  may terminate on frame portion  41  of tree frame  23 . Horizontally facing hub  28  may be positioned so that inboard flowline  29  of flow module  19  may stab into horizontally facing hub  28  during landing of flow module  19 . Similarly, horizontally facing hub  34  of tubing hanger spool flowline  31  may terminate on frame portion  45  of tubing hanger spool frame  35 . Horizontally facing hub  34  may be positioned so that outboard flowline  39  of flow module  19  may stab into horizontally facing hub  34  during landing of flow module  19 . This may be accomplished in part by running flow module  19  to a subsea location proximate to subsea production system  11 . Preferably, ends of outboard flowline  39  and inboard flowline  29  are proximate to horizontally facing hub  34  and horizontally facing hub  28 , respectively. Flow module  19  may then be shifted horizontally to stab ends of outboard flowline  39  and inboard flowline  29  into horizontally facing hubs  34 ,  28 , respectively. In so doing, a portion of the weight of flow module  19  will be transferred to both frame portion  45  and frame portion  41 . As shown in  FIG. 4 , horizontal shift assistance mechanisms (HSAMs)  51 ,  53  may be secured to frame portion  41  and frame portion  45 , respectively. HSAMs  51 ,  53  may comprise hydraulic cylinders, mechanical slide screws, or the like. HSAMs  51 ,  53  will couple to flow module  19  in a manner that allows HSAMs  51 ,  53  to exert a horizontal force that may shift flow module  19  horizontally to make up the flow connection between outboard flowline  39 , and horizontally facing hub  34 , and inboard flowline and horizontally facing hub  28 . By configuring the position of flow module  19  as illustrated herein, a significant reduction in the length of the combined outboard flowline  39  from flow module  19  and tubing hanger spool flowline  31  to a terminal of additional flowlines  49  for connection to external production devices, such as a manifold or other subsea device, is accomplished. This provides a significant advantage over prior art designs that necessitated that the outboard flowline  39  must wind through subsea tree  17  before connecting to tubing hanger spool flowline  31 . 
         [0029]    Accordingly, the disclosed embodiments provide numerous advantages. For example, the disclosed embodiments, provide a shorter flow path from the flow module to external production devices. This leads to a reduction in the pressure drop across the system, and a reduction in the amount of heat lost through the outboard flowlines. In addition, the shorter flowlines provide fewer opportunities for leaks to occur. Still further, the disclosed embodiments allow for production of the subsea production assembly at a reduced cost. This arises as a result of the significant decrease in the amount of material needed to connect the flow module to the external production devices. 
         [0030]    It is understood that the present invention may take many forms and embodiments. Accordingly, several variations may be made in the foregoing without departing from the spirit or scope of the invention. Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.