Patent Publication Number: US-8985219-B2

Title: System and method for connection and installation of underwater lines

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a non-provisional application of co-pending U.S. Provisional Patent Application 61/415,948, filed 22 Nov. 2010, the content of which is incorporated herein by reference for all purposes. 
     BACKGROUND 
     In many subsea oil and gas well applications, flying leads and stab plates are employed to connect hydraulic hoses and electrical cables between subsea production equipment, such as subsea trees and manifolds. The connections are formed with the assistance of a remotely operated vehicle (ROV). The flying lead generally comprises a length of umbilical having copper conductors, optical fibers and/or hoses which can range in length from a few meters to 200 or more meters. The flying lead may have a stab plate at one or both of its ends to serve as the interface between the umbilical and the structures where the lines, e.g. electrical, optical fiber and/or hydraulic, are terminated. 
     Stab plates typically are formed with a stainless steel plate and a population of hydraulic and electrical couplers/connectors. A stab plate also may comprise a locking mechanism, a termination bracket for holding the flying lead umbilical, and an ROV bracket. An ROV is employed to deliver the stab plate to a desired subsea location while gripping the ROV bracket. Once at the desired subsea connection location, the ROV is again employed to use a torque tool for connecting the stab plate to a corresponding stab plate, thus forming the subsea stab plate connection. 
     In many applications, ROVs are used to fly and lock the leads at the desired stab plate connection via an available tool system, such as a tool deployment unit (TDU) or a flying lead orientation tool (FLOT). Each of these types of systems uses a torque tool for locking down one stab plate to a corresponding stab plate, which can result in a complex and time-consuming procedure for forming the subsea connection. Further difficulties may arise in forming a successful subsea connection because existing stab plates can weigh in excess of 100 kg and sometimes in excess of 200 kg without including the weight of the umbilical. Operation of the ROV in performing these complex connection procedures with relatively heavy stab plates creates many difficulties, e.g. large loads acting on the components being connected. As a result, such operations require highly skilled ROV pilots. In some applications, additional difficulties arise from the time required for ROV integration with respect to the corresponding tooling and for calibration of the tools used by the ROV. 
     SUMMARY 
     In general, the present invention provides a technique which facilitates formation of a subsea connection. The technique comprises moving a free portion of a stab plate connection system into proximity with a fixed portion of the stab plate connection system at a subsea location. At the subsea location, the free portion is initially engaged with the fixed portion via an engagement mechanism, such as a docking probe. Subsequently, a local actuator is used to draw the free portion into an operating engagement with the fixed portion so that line couplers of the fixed portion are engaged with corresponding line couplers of the free portion. In some applications, the stab plate connection system also may comprise an ejection mechanism which may be selectively operated to disconnect and eject the free portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
         FIG. 1  is an illustration of a free portion of a stab plate connection system being moved toward a fixed portion of the stab plate connection system, according to an embodiment of the present invention; 
         FIG. 2  is an illustration similar to that of  FIG. 1  but with the free portion positioned in a preliminary engagement with the fixed portion, according to an embodiment of the present invention; 
         FIG. 3  is an illustration similar to that of  FIG. 2  but with the free portion drawn into full engagement with the fixed portion in which line couplers of the fixed portion are engaged with corresponding line couplers of the free portion, according to an embodiment of the present invention; and 
         FIG. 4  is an illustration of the free portion being ejected from the fixed portion, according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
     The present invention generally relates to a system and method for forming a subsea lead connection in which a plurality of lines, e.g. electrical, fiber-optic, and/or hydraulic lines, may be connected to subsea equipment. A stab plate connection system is provided and generally comprises a fixed portion or plate and a free portion or plate which may be selectively moved to a desired subsea location and connected with the fixed portion. 
     The design of the stab plate connection system enables construction of the free portion as a lightweight stab plate of, for example, less than 50 kg. The design also facilitates movement of the lightweight stab plate to substantial depth, e.g. 3000 m or more, via an ROV. Additionally, the free portion/lightweight stab plate may be installed without requiring the use of ROV installation tooling. For example, the free portion may be connected and disconnected from the fixed portion using a subsea control system or an ROV hot stab. Consequently, the installation process is much simpler for the ROV pilot when connecting, for example, large numbers of electrical and hydraulic lines for intervention on live wells from dynamically positioned vessels. The system also may comprise a unique emergency disconnect feature which allows the free portion to be ejected and reconnected, if required, without the need for recovering the free portion to a surface location for re-termination or refurbishment. The ability to immediately reinstall the free portion after ejection from the fixed portion facilitates use of this design with surface dynamically positioned vessels. 
     According to at least one embodiment, the free portion has a very simple design utilizing a junction box and couplers. The design enables a deck crew to change or maintain couplers, e.g. hydraulic and electric connectors, from a position above the plate when laid flat on a surface deck. In this embodiment, the work can be performed without damaging the lines or couplers because the couplers are fully protected within a syntactic foam body. This type of buoyancy designed body helps keep the in-water weight to a minimum and also helps protect the junction box and couplers from impact forces. 
     Referring generally to  FIG. 1 , an embodiment of a subsea system  20  is illustrated as having a stab plate connection system  22 . The stab plate connection system  22  comprises a fixed plate or portion  24  and a free plate or portion  26  which may be engaged with the fixed portion  24  to provide a subsea lead connection which couples control lines to a variety of subsea equipment. The fixed portion  24  is part of or affixed to a subsea installation  28  positioned at a subsea location  30 . The free portion  26  is coupled to an umbilical  32  having a plurality of lines  34 , such as hydraulic lines, electrical lines, and/or fiber optic lines. When a connection is to be formed at the subsea location  30 , the free portion  26  is moved to the subsea location by a suitable device, such as a remotely operated vehicle (ROV)  36 . 
     In  FIG. 1 , free portion  26  is illustrated as being delivered by ROV  36  for engagement with the fixed portion  24 . The ROV  36  requires no special tooling for making the connection between free portion  26  and fixed portion  24  but simply grabs the free portion  26  with an ROV manipulator arm  38 . For example, free portion  26  may comprise an ROV bracket or handle  40  which is simply grabbed by arm  38  for transport of free portion  26  to fixed portion  24  at the subsea location  30 . 
     In the embodiment illustrated, fixed portion  24  comprises a lower plate member  42  and a middle plate member  44  secured to subsea installation  28 . The fixed portion  24  also comprises an upper plate  46  which is illustrated as a part of an ejector mechanism  48 . The upper plate  46  is movable to facilitate engagement of control line couplers  50  of fixed portion  24  with corresponding control line couplers  52  of free portion  26 . Ejector mechanism  48  also is designed to selectively move upper plate  46  in a manner which ejects free portion  26  from fixed portion  24 , as discussed in greater detail below. It should be noted that corresponding couplers  52  terminate the various control lines  34 , and couplers  50  provide corresponding terminations of control lines  54  which are routed from fixed portion  24  to various subsea equipment, as desired for a given subsea application. Couplers  50  and corresponding couplers  52  may comprise a variety of connection devices for connecting electrical, optical fiber, hydraulic, and/or other types of control lines. 
     In the specific example illustrated, ejector mechanism  48  may comprise a spring biased ejector mechanism having one or more springs  56  oriented to bias upper plate  46  to the position illustrated in  FIG. 1 . By way of example, a plurality of springs  56  may be located around telescoping rods or members  58  extending from lower plate member  42  to upper movable plate  46 . The springs  56  bias the rods  58  toward the extended position illustrated. 
     The stab plate connection system  22  further comprises an engagement mechanism  60  which may be selectively positioned to extend beyond movable plate  46  to facilitate easy, preliminary engagement with free portion  26 . The engagement mechanism  60  cooperates with an actuator  62  which may be in the form of a hydraulic actuator mounted to fixed portion  26 , e.g. mounted to lower plate  42 . By way of example, actuator  62  is controlled by a subsea control system  64  and/or an ROV standard hot stab  66 , as illustrated in  FIG. 2 . 
     In  FIG. 2 , the free portion  26  has been released, e.g. dropped, onto the engagement mechanism  60  to establish a preliminary engagement between fixed portion  24  and free portion  26 . The engagement mechanism  60  allows the ROV  36  to release the free portion  26  before the free portion  26  is fully engaged with the fixed portion  24 , i.e. before couplers  50  are engaged with corresponding couplers  52 . This greatly simplifies the ROV pilot operations because no additional ROV tools, e.g. torquing tools, are required. Engagement mechanism  60  may be designed to simplify the installation of free portion  26  by providing a tapered shape  68  which cooperates with a corresponding tapered recess  70  in free portion  26 . The tapered shape  68  and corresponding tapered recess  70  also may be designed with features, e.g. eccentrics or complementary portions, to properly orient the free portion  26  with respect to the fixed portion  24  when the free portion  26  is dropped onto engagement mechanism  60 . 
     By way of example, engagement mechanism  60  may comprise at least one docking probe, such as an individual ISO 13628-8 standard docking probe. The engagement mechanism  60  also may cooperate with a latch  72  operated via a variety of mechanisms, such as an internal hydraulic cylinder connected to latch fingers. In some applications, the latches have internal springs which allow the fingers to retract if there is a loss of hydraulic pressure; however other applications are designed to work without such spring-loaded fingers. In one example, hydraulics used to operate actuator  62  are also plumbed to latch mechanism  72  to allow the latch mechanism  72  and actuator  62  to latch and then retract in sequence using the same hydraulic function. The hydraulic function may be operated and controlled by one or both of the subsea control system  64  and the standard hot stab connection  66 . 
     Actuator  62  is designed to selectively draw free portion  26  into full operational engagement with fixed portion  24 , as illustrated in  FIG. 3 . For example, actuator  62  may be designed with a hydraulic cylinder  74  which is activated via control system  64  and/or hot stab connection  66  to retract engagement mechanism  60  and draw movable plate  46  and free portion  26  toward middle plate member  44 . It should be noted that other types of actuators, e.g. electrical actuators, also may be employed to control the movement and engagement of free portion  26  with fixed portion  24 . The actuator  62  draws corresponding couplers  52  into engagement with couplers  50  of fixed portion  24  to form the subsea connection with control lines  34  of umbilical  32 . 
     As illustrated, the connection mechanism, e.g. actuator  62  and engagement mechanism  60 , is local to and connected into the fixed portion  24 , thus eliminating the need for carrying a torque tool or installation tooling on the ROV. For example, FLOT and TDU systems may be avoided. As a result, many hours of installation time are saved by avoiding ROV set up time otherwise required for procedures such as torque tool mounting, adjustment and calibration. The design also reduces the vessel time otherwise required to form stab plate connections. Actuator  62  and engagement mechanism  60  also enable the stab plate connection system  22  to be oriented at a variety of angles ranging between horizontal and vertical. For example, the free portion  26  may be moved into engagement with fixed portion  24  along a line forming an angle greater than 0 degrees with respect to a line normal to the sea floor. 
     To facilitate proper engagement of couplers  50  with corresponding couplers  52 , middle plate member  44  may be constructed as a floating plate. In other words, the middle plate member  44  may float to adjust itself within predetermined tolerances of the system, thus preventing any misalignment between couplers  50  and corresponding couplers  52  when connecting electrical lines, hydraulic lines, fiber optic lines, or other types of control lines  34 . Similarly, the couplers  50  may be mounted to middle plate member  44  as floating couplers with predetermined tolerances that also help ensure proper line connections. As illustrated, the middle plate member  44  may be used to securely mount the docking probe or other engagement mechanism  60 . The design and arrangement enables a substantially greater number of electrical, fiber optic, and/or hydraulic lines to be connected compared with conventional stab plates. For example, 10×12 way connections (or greater) may be formed due to the design of and controlled engagement of fixed portion  24  and free portion  26 . 
     Referring again to  FIG. 3 , the free portion  26  may be in the form of a stab plate comprising multiple corresponding couplers  52  which serve as terminations for service control lines  34 . The couplers  52  and lines  34  may be hydraulic, electrical, optical fiber, or various combinations of control lines. By way of example, the corresponding couplers  52  may comprise female couplers designed for engagement with male couplers  50  or vice versa. In this embodiment, the corresponding couplers  52  are mounted on a termination junction box  76  protected by a syntactic buoyancy portion  78 , such as a buoyant syntactic foam body. The umbilical  32  may be terminated either in the junction box or distributed to the various corresponding couplers  52  via a bracket bend restrictor  80 . The termination junction box  76  may be filled with oil and pressure compensated against ambient pressure. Additionally, the overall free portion  26  may be shaped for easy ROV flying and easy engagement with the docking probe or other engagement mechanism  60 . 
     Use of junction box  76  enables, for example, termination of multiple electrical and/or optical fiber cables by mounting the junction box on the free portion  26 , which is formed as a stab plate. The multiple control line connectors are bulkheaded to the junction box. This allows the free portion  26  to be constructed as a subsea multi-plug, and the umbilical  32  may be constructed as a much smaller, molded tether. In other words, the junction box serves as an umbilical termination junction box coupled to a molded cable umbilical  32 . The smaller, molded tether not only reduces weight but also reduces stiffness and facilitates installation. In some embodiments, the junction box may be designed for electrical and/or optical fiber lines and used in combination with hydraulic lines and couplers mounted external to the junction box  76 . 
     The stab plate connection system  22  also employs the ejector mechanism  48  to facilitate separation and the potential re-engagement of free portion  26  and fixed portion  24 . In the embodiment illustrated, ejector mechanism  48  employs the upper plate member  46  as an ejector plate which is spring-loaded against springs  56  when the corresponding couplers  52  are drawn into engagement with couplers  50  via actuator  62 . The actuator  62  may be selectively actuated to release latch mechanism  72 , thus enabling springs  56  to eject free portion  26  from fixed portion  24 , as illustrated in  FIG. 4 . In other applications, the actuator  62  may be designed to selectively move plate  46  in an opposite direction to eject free portion  26  with or without the assistance of springs  56 . 
     In some applications and environments, ejection mechanism  48  may be used in certain emergency situations. For example, the ejection mechanism  48  may be employed when the free portion umbilical  32  is in the form of a tether extending from a surface, dynamically positioned vessel and a “run-off” occurs. The design of ejector mechanism  48  allows a suitable control system, e.g. the subsea control system  64  and/or the control provided via ROV hot stab  66 , to disconnect the free portion  26  from the fixed portion  24  under controlled circumstances, e.g. to release latch mechanism  72  via actuator  62  or separate hydraulic plumbing. In other words, the disconnection is accomplished without breaking threaded connections or other traditional types of connections that would require recovery of the components to a surface location for refurbishment. 
     The disconnect and ejection mechanism  48  also may be designed to protect couplers  50  on fixed portion  24  from damage when free portion  26  is initially dropped or placed onto engagement mechanism  60 . The movable plate member  46  and engagement mechanism  60 , e.g. docking probe, prevents any clashing between free portion  26  and couplers  50 . Once free portion  26  is positioned on engagement mechanism  60 , the full engagement of couplers  50  with corresponding couplers  52  is achieved through controlled movement via actuator  62 . In some applications, the movement of free portion  26  into full engagement with fixed portion  24  is completely visible to the ROV. Additionally, any slight misalignment between couplers  50  and corresponding couplers  52  may be eliminated with the floating middle plate member  44 . 
     Although ejection mechanism  48  may be constructed in a variety of forms, the illustrated embodiment employs a plurality of the guide rods  58  which are equally spaced, spring-loaded, and independent of the one or more engagement mechanisms  60 . When engagement mechanism  60  is retracted via actuator  62 , latching mechanism  72  secures free portion  26  and both movable plate member  46  and free portion  26  are drawn to middle plate member  44 . This motion compresses springs  56  and effectively loads the ejector mechanism  48 . The movement is continued by actuator  62  until the couplers  50  are fully engaged with corresponding couplers  52  and the stab plate connection system is fully connected. The movable plate  46  remains sandwiched between free portion  26  and the middle plate member  44  until the ejection sequence is initiated. 
     If ejection of the free portion  26  is desired, an appropriate control signal is sent to actuator  62  which releases latch mechanism  72 . (It should be noted separate actuators may be used to control latch mechanism  72 ) In the illustrated embodiment, the plurality of springs  56  has enough stored energy to separate the couplers  50  and corresponding couplers  52  and to force free portion  26  away from fixed portion  24 , as illustrated in  FIG. 4 . However, the free portion  26  is immediately available for re-engagement with engagement mechanism  60  so that actuator  62  can draw the free portion  26  into full engagement with the fixed portion  24 . As described above, the ejection is achieved without breaking any fasteners or other components that would require recovery to the surface for refurbishment. 
     Depending on the specifics of the subsea application and environment, the slab plate connection system and methodology may be employed with a variety of subsea equipment types for many subsea applications. The shape and hydrodynamics of the free portion  26  may be adjusted to facilitate flying of the free portion as it is moved through water to the desired subsea location. The specific type of docking probe(s) or other engagement mechanism may be adjusted according to the parameters of the subsea application and available equipment. Additionally, the types of control systems, actuators, ejection mechanisms, couplers, and other components may be changed or adjusted for specific applications and/or environments. Similarly, the number and arrangement of control lines and couplers, e.g. connectors, may vary substantially depending on the specific subsea operation undertaken. As a result, the size and type of the umbilical is selected according to the parameters of the application. 
     Although only a few embodiments of the present invention 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 invention. Accordingly, such modifications are intended to be included within the scope of this invention as defined in the claims.