Patent Publication Number: US-10774608-B2

Title: Subsea system and methodology utilizing production receptacle structure

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present document is based on and claims priority to U.S. Provisional Application Ser. No. 62/454,111, filed Feb. 3, 2017, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     In a variety of subsea production operations, electric submersible pumping systems are deployed downhole to a subsea borehole to facilitate production of the desired production fluid, e.g. oil. In some applications, the electric submersible pumping system is conveyed downhole to a desired location and suspended from a power cable. The power cable may be supported by a suitable cable hanger located in, for example, a tubing hanger working in cooperation with a subsea tree. Supporting the electric submersible pumping system from the tubing hanger, however, renders retrieval of the electric submersible pumping system time-consuming and expensive. Additionally, existing systems for suspending electric submersible pumping systems cause difficulties with respect to changing and/or servicing the subsea tree. 
     SUMMARY 
     In general, the present disclosure provides a system and methodology for deploying equipment, e.g. an electric submersible pumping system, in a subsea production operation. According to an embodiment, a subsea tree assembly, e.g. a horizontal subsea tree assembly, comprises a spool body housing having a channel extending therethrough. A production receptacle structure is secured within the channel and provides a reduced internal profile for securing wellbore equipment. For example, the internal profile may be constructed to sealably receive a cable hanger used to support a power line by which an electric submersible pumping system may be suspended. The production receptacle structure also may be equipped with features such as a production stab for interfacing with a tubing hanger located below the production receptacle structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain embodiments will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate various implementations described herein and are not meant to limit the scope of various technologies described herein, and: 
         FIG. 1  is a schematic cross-sectional illustration of an example of a subsea installation comprising a spool body housing and a production receptacle structure secured therein, according to an embodiment of the disclosure; and 
         FIG. 2  is a schematic cross-sectional illustration of another example of a subsea installation comprising a spool body housing and a production receptacle structure secured therein, according to an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous details are set forth to provide an understanding of some illustrative embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
     The disclosure herein generally relates to a system and methodology for deploying equipment, e.g. deploying an electric submersible pumping system, in a subsea production operation. According to an embodiment, a subsea tree assembly, e.g. a horizontal subsea tree assembly, comprises a spool body housing having a channel extending therethrough. A production receptacle structure is positioned within the channel and provides a reduced internal profile for securing wellbore equipment. For example, the internal profile may be constructed to sealably receive a cable hanger used to support a power cable by which an electric submersible pumping system may be suspended. 
     The production receptacle structure also may be equipped with a production stab for interfacing with a tubing hanger located below the production receptacle structure. In some embodiments, the production receptacle structure also may utilize a control line coupler or a plurality of controlling couplers oriented to engage the tubing hanger. Additionally, the production receptacle structure may be removably mounted within the channel of the spool body housing and sealed thereto via a plurality of seals. The combined spool body housing and production receptacle structure may be mounted on a suitable subsea structure located over a well. By way of example, the subsea structure may be in the form of a tubing head spool or wellhead. 
     According to one example, the spool body housing is part of a horizontal tree assembly through which the channel extends generally vertically and has a given diameter. In some embodiments, the diameter may change along the length of the generally vertical channel. The production receptacle structure may be constructed in the form of a mandrel for use in suspending an electric submersible pumping system or other equipment located downhole in a borehole. 
     The production receptacle structure/mandrel may be secured within the generally vertical channel to occupy the given diameter. Additionally, the production receptacle structure may have various types of internal profiles extending therethrough, the internal profile providing a reduced diameter relative to the diameter of the channel. The internal profile may be configured and selected for the purpose of securing desired types of wellbore equipment, e.g. a cable hanger and a wellbore closure apparatus. 
     In pumping system embodiments, a cable may be coupled between the electric submersible pumping system and the cable hanger which is landed and sealed along the internal profile. The lower end of the production receptacle structure may have a variety of configurations and/or features to enable interfacing with a corresponding tubing hanger located therebelow. According to an embodiment, the production receptacle structure may comprise or cooperate with a production stab as well as one or more control line couplers oriented to engage corresponding features in a tubing hanger. Consequently, the production receptacle structure is able to stab into the top of, for example, a vertical monobore tubing hanger which, in turn, is landed in a tubing spool or wellhead. 
     Depending on the application, the lower end of the production receptacle structure, e.g. mandrel, may be machined and/or otherwise formed to engage various types of tubing hangers. This allows the horizontal tree assembly, with its production receptacle structure, to be constructed as a replacement assembly. For example, when a relatively more expensive vertical tree is no longer desired, the vertical tree can be removed from the wellhead/tubing head spool and the less expensive horizontal tree assembly can be delivered to the subsea location and secured to the wellhead/tubing head spool. The production receptacle structure enables straightforward coupling with the existing tubing hanger. 
     In a wide variety of servicing and replacement procedures, the procedure may be performed without removing or affecting the tubing hanger. The production receptacle structure of the horizontal tree, for example, may simply be moved into engagement with the existing tubing hanger. The ability to remove, service, and replace the subsea tree without affecting the tubing hanger enables more rapid and less expensive replacement of or servicing of subsea equipment, e.g. servicing of the electric submersible pumping system. The structure of the horizontal tree combined with the production receptacle structure/mandrel also may help reduce the height and weight of current subsea installations used for through-tubing electric submersible pumping systems. Effectively, the production receptacle structure can be used to convert the bottom of a horizontal tree into the bottom of a functional vertical tree. 
     According to a procedural example, the horizontal tree containing the production receptacle structure may be landed on a tubing spool that houses a vertical tubing hanger following removal of the original vertical tree. By way of example, this type of procedure can be done to provide a tree with a larger bore, e.g. a larger internal profile, which allows passage of an electric submersible pumping system through the tree when the original tree would not allow such passage. Instead of building a new vertical tree with larger valves able to pass the pumping system, the simpler, less expensive horizontal tree (with production receptacle structure) can simply be deployed as a replacement tree. 
     Referring generally to  FIG. 1 , an example of a subsea well installation  20  is illustrated. In this embodiment, the subsea well installation  20  comprises a well structure  22  which may be mounted generally along a sea floor  24 . By way of example, the illustrated well structure  22  comprises a tubing head spool or a wellhead having an internal profile  25  into which a tubing hanger  26  is landed. The tubing hanger  26  may be sealed and locked in place along internal profile  25 . A tubing  28 , e.g. production tubing, may be suspended from the tubing hanger  26  such that the tubing  28  extends down into a casing bore  30 , e.g. a cased wellbore. In this example, tubing hanger  26  is a vertical tubing hanger landed in the tubing head spool/wellhead  22 . 
     In the embodiment illustrated, the subsea well installation  20  further comprises a horizontal tree assembly  32  which may be landed on the well structure  22  and secured thereto by a suitable connector device  34 . By way of example, the horizontal tree assembly  32  comprises a spool body housing  36  having a channel  38  extending therethrough. As illustrated, the channel  38  may extend generally vertically through the spool body housing  36  when the horizontal tree assembly  32  is landed on well structure  22 . 
     The channel  38  has a given diameter sized to receive a production receptacle structure  40 , e.g. a mandrel. Depending on the application, the diameter of the channel  38  may change to provide, for example, an abutment  42  or other features used to hold the production receptacle structure  40  at a desired position within the channel  38 . For example, the production receptacle structure  40  may have a corresponding abutment  44  oriented to engage abutment  42  when the production receptacle structure  40  is inserted into channel  38 . By way of example, the production receptacle structure  40  may be assembled into the horizontal tree assembly  32  at a surface manufacturing facility, e.g. a land-based facility or offshore platform, or it may be landed into channel  38  subsea. 
     The production receptacle structure  40  also may comprise seals  46  positioned at desired locations along its exterior to ensure the appropriate sealing between the production receptacle structure  40  and the surrounding spool body housing  36 . In some embodiments, the production receptacle structure  40  is removable from spool body housing  36 —although a locking mechanism (or mechanisms)  48  may be used to ensure the production receptacle structure  40  remains secured in channel  38  during operation. By way of example, locking mechanism  48  may comprise a split ring positioned in corresponding grooves of housing  36  and structure  40 . 
     In the embodiment illustrated, the production receptacle structure  40  has an internal passage  50  extending therethrough. The internal passage  50  is defined by an internal profile  52  which has a reduced diameter compared to the diameter of channel  38 . The internal profile  52  is appropriately sized and may comprise features, e.g. a profile abutment  54 , which helps support wellbore equipment  56 . By way of example, the wellbore equipment  56  may comprise a suspension apparatus  58 , e.g. a cable hanger, and a cable plug  60 . The cable plug  60  forms a second barrier along passage  50 . Equipment  56  such as the cable hanger  58  and cable plug  60  may comprise seals  62  to ensure sealing between the equipment  56  and the surrounding production receptacle structure  40 . In some embodiments, locking mechanisms  64 , e.g. lock rings, also may be used to secure the equipment, e.g. cable hanger  58  and/or cable plug  60 , along internal profile  52 . It should be noted that in some embodiments, the cable hanger  58  may be in the form of a plug without an electrical pass through. For example, the cable hanger  58  and/or cable plug  60  may be in the form of wireline plugs or other types of devices positioned along internal profile  52 . 
     The cable hanger  58  may be positioned and secured along the internal profile  52  for suspending downhole equipment such as the illustrated electric submersible pumping system  66 . The electric submersible pumping system  66  (and/or other downhole equipment) may be suspended within tubing  28  via a power line  68  having a suitable conductor or conductors  70  able to deliver electrical power from a power source down through tubing hanger  26  to the electric submersible pumping system  66  (and/or other downhole equipment). In the illustrated example, the power line  68  is in the form of a power cable  72  secured to cable hanger  58 , however the power line  68  may be constructed in other configurations, e.g. coiled tubing with internal conductors. As illustrated, the power line  68  may be routed up through cable hanger  58 , cable plug  60 , and a debris cap  74  to a suitable power source, such as a surface-based power source. The cable hanger  58  and the cable plug  60  may be used as redundant seals to prevent unwanted escape of fluids along the internal passage  50 . Depending on the type of conductors  70  routed into production receptacle structure  40 , the debris cap  74  may be replaced or supplemented with an open water cap, a flying lead attachment cap, a tree adjacent flying lead connection, or other suitable device. 
     A lower end  76  of the production receptacle structure  40  may have a variety of configurations for engagement with tubing hanger  26 . In some embodiments, the production receptacle structure  40  comprises or works in cooperation with a production stab  78  oriented to stab into the tubing hanger  26  located therebelow. The production receptacle structure  40  also may comprise or work in cooperation with other features, such as at least one control line coupler  80 , e.g. a plurality of control line couplers  80 , also oriented to stab into tubing hanger  26 . Each control line coupler  80  is coupled with a corresponding control line  82 , e.g. an electrical or hydraulic control line. The control lines  82  may be routed below tubing hanger  26  to desired downhole equipment and also to an external connection  84 , e.g. a block mounted valve, which may be located along an exterior of spool body housing  36  or at another suitable location. The control line or control lines  82  may be routed from production receptacle structure  40  to spool body housing  36  between seals  46  and/or through a special seal region  85  and then on to one or more of the external connections  84 . 
     The production stab  78 , control line couplers  80 , and/or other features of lower end  76  may be configured and oriented for engagement with many types of tubing hangers  26 . Consequently, the production receptacle structure  40  can simply be stabbed into engagement with the existing tubing hanger  20  when horizontal tree assembly  32  is landed on the well structure  22 . 
     In some embodiments, the horizontal tree assembly  32  may comprise a lateral arm  86 , e.g. a horizontal arm, having a production flow passage  88 . In some embodiments, the lateral arm  86  comprises a wing block. The production flow passage  88  may be placed in fluid communication with a corresponding passage  90  located through a side wall forming production receptacle structure  40 . The corresponding passage  90  is in fluid communication with internal profile  52 . Consequently, operation of electric submersible pumping system  66  produces well fluid up through tubing  28 , through tubing hanger  26 , into internal passage  50 , out through corresponding passage  90 , and through production flow passage  88  of lateral arm  86 , to a corresponding flow tubing  92 . 
     At least one valve  94 , e.g. a production valve, may be positioned in lateral arm  86  to provide selective control over fluid moving along production flow passage  88 . In some embodiments, redundant valves  94 , e.g. a pair of valves  94 , may be placed in lateral arm  86  along production flow passage  88  to provide redundant capability for shutting off flow through passage  88 . The valves  94  serve as control barriers located along a controllable flow path. 
     Depending on the parameters of a given operation, the subsea installation  20  and horizontal tree assembly  32  may have a variety of configurations and features. In some embodiments, for example, an annulus flow capability with respect to the annulus surrounding production tubing  28  may be facilitated by providing an annulus flow run passage  96  routed through the spool body housing  36 . By way of example, the annulus flow run passage  96  may be placed in fluid communication with channel  38  below production receptacle structure  40  and with internal profile  52  at, for example, a location between cable hanger  58  and cable plug  60 . A corresponding annular flow passage  98  may be located laterally through the wall forming production receptacle structure  40 . 
     Additionally, suitable valves  100  as well as an external fluid coupling  102  may be located along the annular flow passage  98 . In some embodiments, an additional flow run passage  104  may be located in the wall of production receptacle structure  40  to provide communication between passage  98  and internal profile  52  at a location above cable plug  60 . Various other features also may be incorporated into components of the overall subsea well installation  20  to accommodate various subsea operations. For example, such features may include a crossover passage from annulus to production for circulation. 
     Referring generally to  FIG. 2 , another embodiment of subsea well installation  20  and horizontal tree assembly  32  is illustrated. In this embodiment, the electric submersible pumping system  66  is again suspended from cable hanger  58  via power line  68 , e.g. power cable  72 . However, the electrical lead/conductor  70  is routed laterally through spool body housing  36  and production receptacle structure  40  before entering cable hanger  58  between a pair of the seals  62 . The electrical lead/conductor  70  may be routed through an external electrical coupler  105  located along the exterior of spool body housing  36 . 
     Additionally, a wellbore closure apparatus  106  is positioned along internal profile  52  above cable hanger  58  so as to provide a redundant seal along internal profile  52 . In some embodiments, the wellbore closure apparatus  106  may comprise cable plug  60 . In the illustrated embodiment, however, the wellbore closure apparatus  106  comprises a valve  108 , e.g. a workover valve, which may be selectively opened to allow flow along internal profile  52  or closed against flow along internal profile  52 . For example, the valve  108  may be closed during a production mode in which electric submersible pumping system  66  is operated to produce a well fluid. When in the closed position, the wellbore closure apparatus  106  works in cooperation with cable hanger  58  to provide redundant control barriers along a potential leak path. In some embodiments, the valve  108 , when opened, may be of sufficient size to accommodate passage of electric submersible pumping system  66  and cable hanger  58  therethrough during deployment. Additionally, the wellbore closure apparatus  106  may comprise other types of devices, such as a wireline plug. In some embodiments, the cable hanger  58  may be in the form of a wireline plug. By way of example, devices  58 ,  106  may be in the form of two plugs deployed along passage  50  to provide suitable barriers without electrical conductor  70  passing therethrough. 
     Embodiments described herein provide an electric submersible pumping system completion approach utilizing the production receptacle structure  40  to house cable hanger  58  instead of using other features, e.g. tubing hanger  26 . If a cable hanger is placed in the tubing hanger, damage to the tubing hanger profile can result in costly retrieval of the tubing hanger. In contrast, embodiments described herein reduce or eliminate the risk of damage to the tubing hanger by positioning cable hanger  58  in production receptacle structure  40 . As a result, repairs or servicing of the present system involve the much less expensive operation of retrieving the tree assembly  32  (or possibly even the production receptacle structure  40  itself). Use of the production receptacle structure  40  can facilitate many types of operations, including servicing of the electric submersible pumping systems. The production receptacle structure  40  may be configured to interface with many types of horizontal trees, including off-the-shelf horizontal trees, with no modification or limited modification of the horizontal tree. 
     The production receptacle structure  40  and corresponding spool body housing  36  also may be used as a solution for completion scenarios other than electric submersible pumping system completions. For example, the production receptacle structure  40  can provide a location to suspend, seal off, or lockdown related equipment such as plugs, e.g. wireline plugs, or well suspended conduits. Depending on the application, the production receptacle structure  40  may contain many types of control line couplers, including electrical couplers and hydraulic couplers, oriented for stabbing into the tubing hanger  26  located therebelow. 
     Additionally, the production receptacle structure  40  may be placed into the horizontal tree assembly  32  at the factory, offshore, or subsea. Once installed, the production receptacle structure  40  provides a new profile for suspension equipment and/or well control devices. 
     According to an operational example, the horizontal tree assembly  32  described herein may be constructed to facilitate deployment of electric submersible pumping systems  66 . In such an embodiment, the production receptacle structure  40  may be constructed for engagement with an existing vertical tubing hanger  20 . This allows, for example, an existing vertical tree which is not ready for an electric submersible pumping system to be removed and easily replaced by the horizontal tree assembly  32 . As described above, the horizontal tree assembly  32  is readily configurable to provide two barriers along the lateral production passage  88  of lateral arm  86  via two production valves  94 . 
     In some embodiments, the production receptacle structure  40  may have an upper seal profile configured to accept a workover riser connection or stab. The workover riser may be referred to as a blowout preventer (BOP) unit riser system or a lightweight intervention riser system. Additionally, the configuration of horizontal tree assembly  32  enables the use of many types of electric submersible pumping systems  66  suspended by, for example, power cable  72  and installed through the production tubing  28  rather than being attached to and the suspended from the production tubing  28 . The workover riser is able to provide a pressure contained conduit from the surface to the well for purposes of installing the through-tubing electric submersible pumping system  66 . 
     The production receptacle structure  40  and its internal profile  52  may have various features to facilitate landing, locking, and sealing of internal equipment, such as cable hanger  58  and cable plug  60 . Depending on the application, various valves  94 ,  106  may be located in the vertical and horizontal passages. Accordingly, the overall subsea well installation  20  as well as the horizontal tree assembly  32  may have a variety of configurations and features to accommodate many types of subsea operations. 
     Although a few embodiments of the system and methodology have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.