Abstract:
A method of installing equipment subsea comprising the steps of: assembling the equipment within a frame; submerging in the sea at least a part of an assembly comprising the frame and the equipment; coupling the at least partially submerged assembly to a vessel; transporting the at least partially submerged assembly proximate a subsea installation site; coupling the assembly to an installation device; and installing the equipment at the installation site using the installation device. A frame for supporting equipment is also disclosed wherein the frame is shaped to match the dimensions of the equipment to be supported. The frame comprises at least one clamp having a first half clamp member for releasably engaging a second half clamp member of a second structure and a full clamp member for clamping around and supporting the equipment. The first half clamp member and the full clamp member can be integrally formed.

Description:
FIELD OF THE INVENTION 
     The invention provides a method of installing equipment subsea and a frame for supporting equipment. In particular the invention relates to a method of installing equipment to connect two subsea installations and a frame suitable for supporting and transporting the equipment. 
     DESCRIPTION OF RELATED ART 
     Spool pieces (or jumpers) are lengths of tubular that are typically used in the hydrocarbon production industry to join terminations on two subsea installations. Each end of the spool piece is provided with terminations that mate with the terminations on the subsea installations. The spool pieces are often bespoke and are designed and constructed with the required dimensions according to the relative separation and orientation of the two subsea terminations. 
     Spool pieces typically have a greater relative length than diameter. As a result, the spool pieces have a relatively low structural strength and must be deployed in a manner that provides adequate support for the spool piece. Conventionally, the spool piece is attached to a lifting beam using multiple suspension points along its length, or built into a lifting frame for support, then lowered through the sea to the installation site. 
     BRIEF SUMMARY OF THE INVENTION 
     According to a first aspect of the invention, there is provided a method of installing equipment subsea, the method comprising the steps of:
         (a) assembling the equipment within a frame;   (b) submerging in the sea at least a part of an assembly comprising the frame and the equipment;   (c) coupling the at least partially submerged assembly to a vessel;   (d) transporting the at least partially submerged assembly proximate a subsea installation site;   (e) coupling the assembly to an installation device; and   (f) installing the equipment at the installation site.       

     According to step (a), the equipment can be assembled within the frame onshore. The method can include towing the frame across the shoreline and into the water. The method can include fully submerging the assembly comprising the frame and the equipment. 
     According to a second aspect of the invention, there is provided a frame for supporting equipment, wherein the frame is shaped to match the dimensions of the equipment to be supported and comprises at least one clamp, the clamp comprising a first half clamp member for releasably engaging a second half clamp member of a second structure and further comprising a full clamp member for clamping around and supporting the equipment. 
     The frame can comprise a structure of any shape or size with the functional requirement that it is arranged to support the equipment. For example, the frame can comprise a plurality of interconnecting struts. Alternatively, the frame could comprise a block that accommodates an amount of buoyant material. 
     The full clamp member can comprise two hinged jaws that are pivotable about the hinge between an open configuration in which a leading edge of each jaw is spaced from the leading edge of the other jaw and a closed configuration in which the leading edges of the jaws are brought together to thereby enclose the equipment within the full clamp member. 
     The full clamp member can be provided with a locking device to lock the jaws into secure engagement in the closed configuration. The locking device can comprise a hydraulically operable locking cylinder. 
     Preferably, the first half clamp member and the full clamp member are integrally formed. 
     The first half clamp member can comprise two leading edges that are arranged to engage two leading edges of the second half clamp member on the second structure. 
     The leading edges of the jaws of the full clamp member and/or the leading edges of the first and the second half clamp members can be provided with interlocking castellations. 
     The first half clamp member can be provided with a locking arrangement to lock the first half clamp member and the second half clamp member into secure engagement. The locking arrangement can comprise a passageway through each the leading edge of the first half clamp member extending through the leading edge of the second half clamp member wherein each passageway accommodates a retractable locking pin. 
     The second structure can include at least one second half clamp member arranged for engagement with the at least one first half clamp member of the frame. 
     The second structure can be arranged to carry the load of the frame when the second half clamp member and the first half clamp member of the frame are engaged in use. 
     The second structure can be a launch frame. The second structure can be provided with at least one substantially planar runner arranged to contact a surface in use. The at least one runner can be provided with an upturned end portion along at least one edge to facilitate movement of the second structure along a surface. 
     The at least one clamp can be carried by a support formed as part of the frame. The at least one second half clamp member can be carried on a support formed as part of the second structure. The frame can be provided with a plurality of supports carrying clamps to support the equipment along its length. The second structure can be provided with a plurality of corresponding supports carrying the second half clamp members. 
     The frame can comprise two or more feet for supporting the frame on a surface in use. The feet can be substantially coplanar. The frame can be constructed to transfer the load through the feet when the frame is upright and supported on a surface in use. 
     The frame can further comprise a lifting portion provided with at least one lifting point, selected such that the frame can be suspended in the sea from the at least one lifting point. Preferably, the lifting point is selected such that the frame remains substantially level relative to the seabed when suspended from the at least one lifting point in the sea. 
     The frame of the first aspect of the invention can comprise any of the features and corresponding method steps according to the second aspect of the invention described above. 
     Thus, according to step (a), the method can include supporting the equipment on the second structure, coupling the frame to the second structure and the equipment and towing the second structure into the water. 
     Following step (b), the method can include detaching the second structure from the frame. This step can include releasing the second half clamp member portion from the first half clamp member. The method can include parking the assembly on the seabed prior to releasing the second half clamp member from the first half clamp member. 
     The method can include actuating the locking arrangement to thereby release the first half clamp member from the second half clamp member. This can be achieved using a remotely operated vehicle or a diver. 
     The method can also include attaching a recovery line to the second structure and recovering the second structure following detachment from the frame. The method can include reconfiguring the second structure for use with another item of equipment to be installed subsea. 
     According to step (c), the vessel can be provided with a lifting mechanism and the lifting portion of the frame can be attached to the lifting mechanism that is actuable to couple the frame to the vessel. The lifting mechanism can comprise a heave-compensated winch. 
     According to step (c), the method can include locking the frame to the vessel. Locking members can be provided on the vessel for this purpose. 
     Preferably, according to step (d), the method includes transporting the equipment below the splash zone of the sea. 
     The method can further include sheltering the equipment and the frame during transportation through the sea. The method can include constructing sidewalls on a part of the vessel that is arranged to be submerged in use, to thereby define a recess beneath the vessel. The method can include sheltering the frame and equipment within the recess. The method can include deviating the flow away from the assembly and around the submerged part of the vessel in use. 
     The method can include adding buoyancy to at least one of: the vessel; the equipment; and the frame. 
     The method can include providing an opening in the hull of the vessel to accommodate at least part of the frame within the opening. The vessel can be a substantially flat-bottomed vessel such as a barge or pontoon. 
     Prior to step (e) the assembly can be parked proximate the installation site, pending coupling the assembly to the installation device. 
     According to step (e), the method can include coupling the assembly to an installation vessel and can include coupling the assembly to a crane provided on the installation vessel. 
     Following step (f), the method can include releasing the frame from the equipment. The method can include pivoting the jaws of the full clamp member to the open configuration and thereby releasing the equipment. 
     The method can further include recovering the frame. The frame can be recovered using the installation device. The frame can be transported to shore using the vessel. The method can further include reconfiguring the frame for use with another item of equipment to be installed subsea. 
     The equipment to be installed subsea can comprise a subsea connector with end terminations for connecting two subsea installations. 
     “Subsea” or “sea” as used herein is intended to refer to any body of liquid that may contain water (fresh water or salt water or otherwise) and “seabed” is intended to refer to a lower surface of the “sea” as defined herein. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
       One embodiment of the invention will now be described with reference to and as shown in the accompanying drawings, in which: 
         FIG. 1  is a side view of a frame assembly carrying a spool piece; 
         FIG. 2  is a side view of detail A in  FIG. 1 . 
         FIG. 3  is a front end view of the frame assembly of  FIG. 1 ; 
         FIG. 4  is a plan view of the frame assembly of  FIG. 1 ; 
         FIG. 5  is a sectional view of a pontoon and part of the frame assembly of  FIG. 1 ; 
         FIG. 6  is a sectional view of the pontoon perpendicular to the  FIG. 5  view; 
         FIG. 7  is a plan view of the pontoon of  FIG. 5  showing part of the frame assembly therebeneath; 
         FIGS. 8-17  are consecutive steps illustrating the method according to the first aspect of the invention; 
         FIG. 18  is a side view of detail A of  FIG. 2  with a half clamp member removed; 
         FIG. 19  is a side view of  FIG. 18  with a full clamp member in an open configuration thereby freeing the spool piece; and 
         FIG. 20  is an end view of the full clamp member of  FIG. 19  in the open configuration. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A spool piece  20  according to the present embodiment is a small bore pipeline that is shaped and manufactured with the required dimensions to connect a particular pipeline end termination  110  to a subsea manifold  112  (shown in  FIGS. 13 to 17 ) to allow fluid communication therebetween. The spool piece  20  is manufactured with two end portions  22 ,  24  that carry the necessary end terminations in the correct orientation for interconnection with the pipeline end termination  110  and the subsea manifold  112 . 
     A frame assembly is shown generally at  10  in  FIG. 1 . The frame assembly  10  is provided in two parts: a spool frame  30 ; and a second structure in the form of a launch frame or sledge  12 . 
     The sledge  12  is constructed according to the specific dimensions of the spool piece  20 . The sledge  12  has runners  14  that are arranged to lie parallel to the surface of the ground or the seabed  94  in use. The runners  14  have upturned ends  13  to the front and rear of the sledge  12 , to facilitate movement of the sledge  12  over a surface. A plurality of upstanding supports  16  project perpendicular to the runners  14 . Each of these supports  16  is arranged at the requisite height and position corresponding to the shape of the spool piece  12  to be carried within the frame assembly  10 . An upper end of each support  16  carries a half clamp member  18  in the form of a hollow semi-cylindrical portion. The inner diameter of the half clamp member  18  is shaped to accommodate a portion of the spool piece  20 . The edges of the half clamp member  18  are provided with castellations  19  having a transverse cylindrical passageway (not shown) extending therethrough for receiving an hydraulically operable locking pin  38  that is extendable and retractable through the passageway. The sledge  12  is also provided with appropriately located pad eyes (not shown) for attaching towlines and recovery lines thereto. 
     The spool frame  30  is also manufactured according to the specific dimensions of the spool piece  20 . The spool frame  30  comprises three lengths of substantially co-planar parallel feet  31 . The feet  31  are arranged to contact the surface or the seabed on which the spool frame  30  is parked in use, in order to maintain the spool frame  30  in an upright orientation. The feet  31  support upstanding struts  33  that are substantially perpendicular to the plane of the feet  31 . The upstanding struts  33  are connected to cross-wise struts  39  that are arranged substantially perpendicular to the struts  33 . A plurality of supports  32  project downwardly from the cross-wise struts  39 . The supports  32  are parallel to the struts  33 . 
     Each spool frame support  32  carries a clamp. The clamp comprises a half clamp member  34  that is integrally formed with a full clamp member  36 . Each half clamp member  34  is substantially hollow and semi-cylindrical and has ends which are provided with castellations  35  that interfit with the castellations  19  provided on the half clamp member  18  of the sledge  12 . Similarly, the castellations  35  have a centrally disposed cylindrical passageway extending therethrough to accommodate the hydraulically operable locking pin  38  to thereby lock the castellations  19  of the half clamp member  18  to the castellations  35  of the half clamp member  34 . 
     The full clamp member  36  is substantially cylindrical, hollow and arranged to enclose the spool piece  20 . The full clamp member  36  (see  FIG. 20 ) comprises an upper jaw  36   u  and a lower jaw  36   l  that is pivotable about a hinge  39  relative to the upper jaw  36   u . The leading edges of the jaws  36   u ,  36   l  are provided with interlocking castellations  37 . The jaws  36   u ,  36   l  are pivotable between an open configuration in which the leading edges are spaced apart to thereby release or allow insertion of the spool piece  20  within the clamp, and a closed configuration in which the edges are brought together to retain the spool piece  20  within the jaws  36   u ,  36   l . The full clamp member  36  is lockable in the closed configuration by means of a hydraulic locking arrangement  40 . 
     The spool frame  30  has a lifting portion  41  having lift points arranged thereon to ensure an even lift of the frame assembly  10 . Two winches  44 ,  45  are provided on opposing sides towards the front end of the spool frame  30 . Two further winches  46 ,  47  on opposing sides are provided towards the rear end of the spool frame  30 . A remotely operated vehicle (ROV) docking station  48  is centrally disposed along one side of the spool frame as shown in  FIGS. 3 and 4 . The ROV docking station  48  has an ROV operable panel for a supplying power and operating a control system. Several camera and light assemblies  52  are also attached around the spool frame  30  to provide visual feedback to surface. 
       FIGS. 5-7  show a flat-bottomed vessel such as a barge or a pontoon  60  that is provided with tankage of sufficient buoyancy to carry the spool frame  30  and the attached spool  20 . The pontoon  60  has a moonpool  62  or opening in the hull that allows access to the sea therebelow. On the deck of the pontoon  60 , a tower  64  is constructed around the moonpool  62 . A heave compensated winch  72  is fixed to the deck of the pontoon  60  and has a winch line  76  attached thereto running through a pulley  74  supported by the tower  64 . Two spool locks  66  are provided on opposing sides of the moonpool  62  to securely lock the spool frame  30  to the pontoon  60 . A flow deviator  70  is provided beneath the front end of the pontoon  60  facing the direction of travel of the pontoon  60 . The flow deviator  70  has sidewalls  82  that extend along a portion of two opposing sides of the pontoon  60 . The flow deviator  70  and the sidewalls  82  define a recess  80  in which a portion of the spool frame  30  and the spool  20  can be stored during transportation. 
     Prior to deployment, the necessary spool piece  20  dimensions and end termination orientations are determined and the spool piece  20  is constructed onshore. Similarly, the bespoke spool frame  30  and sledge  12  is constructed according to the dimensions of the spool piece  20 . 
     The spool piece  20  is then arranged on the half clamp members  18  provided on the upstanding supports  16  of the sledge  12 . The jaws  36   u ,  36   l  of the full clamp member  36  are pivoted about the hinge  39  to ensure that the jaws  36   u ,  36   l  are moved to the open configuration. The spool frame  30  is then lowered in place over the spool piece  20  such that the downwardly extending supports  32  are aligned with the axis of the upstanding supports  16  of the sledge  12  and the castellations  19  on the half clamp member  18  and the castellations  35  on the half clamp member  34  intermesh. The half clamp members  18 ,  34  can be locked into secure engagement by actuating the hydraulic locking pin  38  to engage the centrally disposed passageway extending through the castellations  19 ,  35 . The lower jaw  36   l  of the full clamp member  36  is pivoted about the hinge  39  from the open configuration to the closed configuration to intermesh the castellations  37 . The hydraulic locking arrangement  40  can be actuated to close and lock the jaws  36   u ,  36   l  of the full clamp member  36 . This ensures that the spool  20  is securely located within the frame assembly  10 . The spool frame  30  is arranged on the sledge  12  such that the load is transferred to the sledge  12 . The winch line  76  from the heave-compensated winch  72  on the pontoon  60  is pre-attached to the lifting portion  41  of the spool frame  30 . 
     A towline  96  is attached to the front of the sledge  12  and a recovery line  98  is attached to the rear of the sledge  12 , as shown in  FIG. 8 . A tug (not shown) is attached to the other end of the towline  96  and the frame assembly  10  is pulled such that the runners  14  move along the shore, across the shoreline and into the sea  90 . The tug then pulls the frame assembly  10  along the seabed  94  to a pre-prepared site in water that is sufficiently deep (approximately 20-30 metres) for the pontoon  60  to be parked above the frame assembly  10 . The pontoon  60  is manoeuvred over the frame assembly  10  such that the frame assembly  10  is positioned directly below the recess  80 . The slack in the winch line  76  that was pre-attached to the lifting portion  41  is continuously taken up by the heave compensated winch  72  via the pulley  74  attached to the tower  64  (see  FIG. 9 ). 
     A work class ROV  100  is flown towards the frame assembly  10  and engages with the hydraulic locking mechanism to retract the pins  38  from the passageway through the castellations  19 ,  35  ( FIG. 18 ). This releases the half clamp member  18  of the sledge  12  from the half clamp member  34  of the spool frame  30 . Thus, the sledge  12  is detached from the spool frame  30  and the spool piece  20 , which is retained by the clamps  36  in the closed configuration. The winch  72  is activated to lift the spool frame  30  and spool piece  20  within the recess  80  such that the lifting portion  41  is accommodated in the moonpool  62  ( FIG. 10 ). The spool frame  30  is retained in this position by spool locks  66  provided on the pontoon  60 . The sledge  12  is then recovered using the pre-installed recovery line  98  and returned to the onshore build site where it can be reconfigured for use with another spool piece. 
     The pontoon  60  is then towed to the region of the spool piece  20  installation site. As the spool frame  30  and attached spool piece  20  is towed through the sea  90 , since the spool piece  20  is submerged and stored in the recess  80  beneath the pontoon  60 , the spool piece  20  is transported beneath the splash zone, thereby substantially protecting it from damage by wave action. The spool piece  20  is also protected during transportation by the flow deviator skid  70  and the protective sidewalls  82 . 
     At the installation site, the pontoon  60  is tied up to a deployment vessel (not shown). The deployment vessel is then manoeuvred into the required position above the installation site. The heave-compensated winch  72  accounts for changes in the tension of the winch wire  76  due to the heave of the pontoon  60  at sea  90 . The spool frame  30  and the spool piece  20  are lowered from the pontoon  60  onto the seabed  94  ( FIG. 11 ) where the spool frame  30  and attached spool piece  20  is wet parked and the winch wire  76  is disconnected. The pontoon  60  is then held pending recovery of the spool frame  30 . 
     An installation winch line  102  from the installation vessel is attached to the lifting portion  41  of the spool frame  30  to couple the spool frame  30  to an installation device (not shown) in the form of an abandonment and recovery winch (or crane) to complete the installation operation ( FIG. 12 ). Because the spool frame  30  and the spool piece  20  are submerged in the sea  90  their effective weight is reduced. Optionally, the weight of the spool frame  30  can be further reduced by incorporating buoyancy within the spool frame  30  and/or the spool piece  20 . The reduction in the effective weight of the spool frame  30  and the spool piece  20  combined with the fact that the operation to install the spool piece  20  commences subsea, means that the load capacity and necessary reach of the crane is greatly reduced compared with conventional operations. The vessel lifts the spool frame  30  from its wet parked position on the seabed and locates the spool frame  30  and spool piece  20  above the installation site. Alternatively, the installation device can be in the form of a winch rather then a crane to further reduce the costs of the installation operation. 
     A first ROV (not shown) is docked on the ROV panel  48  of the spool frame  30  to power and control the four corner winches  44 ,  45 ,  46 ,  47  and the light and camera assemblies  52 . A second ROV (not shown) flies winch lines  118  to pre-laid clump weights  114 ,  115  in the region of the installation site to thereby connect the winches  44 ,  45  to the clump weights  114 ,  115 . The second ROV then flies winch lines  118  between the winch  46  and the pipeline end termination  110  and between the winch  47  and the subsea manifold  112  to thereby couple the spool frame  30  to the installation targets ( FIG. 13 ). The spool frame  30  is manoeuvred using the winch line  102  coupled to the surface vessel in combination with the four corner winches  44 ,  45 ,  46 ,  47  ( FIG. 14 ). Visual feedback is provided by the light and camera assemblies  52  and the second ROV. The position of the spool frame  30  is thus adjusted until the spool piece  20  end termination  24  is immediately adjacent the pipeline end termination  110  and the other spool piece  20  end termination  22  is immediately adjacent the subsea manifold  112  ( FIG. 15 ). The connections between the end terminations are then made up by the second ROV. The end terminations  22 ,  24  of the spool piece  20  and/or the pipeline end termination  110  and the subsea manifold  112  can be provided with guides to facilitate connection of the spool piece  20  despite any misalignment. In this way, the spool piece  20  is guided into position relative to the pipeline end termination  110  and the subsea manifold  112  whilst accounting for some axial and/or radial and/or angular misalignment. 
     The second ROV releases the hydraulic locking pins  40  to pivot the lower jaws  36   l  about the hinges  39  to thereby move the full clamp members  36  into the open configuration and release the spool piece  20  from the spool frame  30  ( FIGS. 16 ,  17 ,  19 ). The second ROV then releases the winch lines  118  from their attachment points on the pipeline end termination  110 , the subsea manifold  112  and the clump weights  114 ,  115 . The first ROV is also released from the control panel  48 . 
     The spool frame  30  is again wet parked on the seabed  94  and the installation winch line  102  attaching the spool frame  30  to the installation vessel is detached. The pontoon  60  is reconnected to the spool frame  30  via the winch line  76  and the spool frame  30  is recovered into the recess  80  of the pontoon  60 , which then transports the spool frame  30  to shore where the spool frame  30  can be reconfigured for use with another spool piece. 
     Modifications and improvements can be made without departing from the scope of the invention. For example, the spool piece can connect three or more subsea installations. Additionally, the spool pieces can be provided to connect any type of subsea structure.