Abstract:
An apparatus and method for protecting wellheads of a fixed-leg drilling and production platform which provide an alternative from the shutting in of producing wells as currently required. The apparatus provides a structural barrier for the production process systems of the platform, shielding such systems from heavy objects which may be dropped in the course of rig mobilization and skidding procedures. A method of installing an embodiment of the apparatus allows the barrier to be installed without shutting in the production wells.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention generally relates to fixed leg platforms used in relatively shallow water for producing mineral resources, specifically oil and gas. The present invention more specifically relates to various embodiments of an apparatus and a method of installing an apparatus which protects wellheads from being struck from objects or equipment which may fall and impact the wellhead and production processing equipment.  
         [0002]     Offshore hydrocarbon production in federal waters is regulated by the Minerals Management Service (the “MMS”). The MMS currently requires that wells be shut-in during various operations, including operations to install a drilling or work-over rig on the platform. Specifically, the applicable regulations require that all producing wells in the affected wellbay be shut in below the surface and at the wellhead when a drilling rig is moved between wells on the platform. The regulation also requires that wells be shut-in during rigging up and rigging down activities which occur within 500 feet of the affected platform or when a drilling unit is moved between wells on a platform or when a mobile offshore drilling unit moves within 500 feet of a platform.  
         [0003]     This regulation recognizes that many heavy components are lifted over the wellbay and over the wellheads and production piping therein during the mobilization and moving of a drilling rig, presenting the risk that a heavy component may be dropped onto the production piping of a wellhead resulting in damage to the facilities and the possible release of hydrocarbons. The regulation further provides that once enough of the drilling rig, such as the superstructure, is over the well of interest, the wells may be returned to production. However, for a variety of reasons, the moving of a drilling rig may be delayed, resulting in a prolonged period that one or more producing wells are shut-in. For example, in rough seas the work boat transporting rig components may be delayed while waiting for smoother seas to deliver the components to the platform.  
         [0004]     Shutting in producing wells is problematic for at least two reasons. First, production is lost or delayed when wells are shut-in. Bringing the wells back online can be time-consuming and may require substantial supervision to safely return the wells to production. Second, some wells are damaged from being shut-in, and do not always return to their previous flow rates after the wells are returned to production. For example, fine particles may be repositioned within the reservoir rock as a result of ebbing and surging flow associated with stopping and resuming of the production in a well. Loss of production is not only detrimental to the owner of the wells, but it also adversely impacts the royalties received by the federal government.  
         [0005]     The MMS regulations grant the MMS District Supervisor some discretion in the shutting in of producing wells. The regulations provide that the MMS District Supervisor may approve departures from the shut-in requirement by making application to the District Supervisor. Among other information, the District Supervisor may consider platform structural data and point load calculations showing that the production process systems can withstand the impact of a dropped object. The District Supervisor may also consider a lift sequence plan which describes the order of the lifts, and the lift positioning on the platform deck relative to the wellbay areas and production processing equipment.  
       SUMMARY OF THE INVENTION  
       [0006]     The embodiments of the apparatus disclosed herein and the disclosed method provide an alternative for departing from the MMS shut-in requirements by providing an effective structural barrier for the production process systems. Each embodiment is used on a fixed-leg offshore drilling and production platform, where the platform is of the type having one or more wellheads disposed on a production deck. Because there is limited space on a production platform, each wellhead is located in close proximity to the next adjacent wellhead, where the centerlines of the wellheads are usually only a few feet apart from one another. Hydrocarbon fluids, such as oil and gas, are produced through the wellheads and produced into the platform&#39;s production process system.  
         [0007]     The area immediately adjacent to the wellheads, both laterally and spatially, is known as the wellbay. The wellbay is usually separated from adjacent platform systems by one or more firewalls, which usually extend upwardly from the production deck to the drilling deck. The wellhead production trees and connected piping are contained within the wellbay area.  
         [0008]     The platform further comprises a pair of skid beams, herein designated the first skid beam and the second skid beam, which are generally horizontally disposed in parallel relation to one another and disposed above the production deck. The top surface of the skid beams usually extends above the drilling deck for receiving the components of a modular drilling rig or production rig, which are typically erected on a modular substructure attached to the skid beams. A modular drilling rig may be repositioned along the skid beams and along the drilling rig substructure to allow the drilling of additional wells from different locations within the wellbay without completely dismantling the drilling rig.  
         [0009]     The level of the platform at which the drilling rig substructure is placed is usually referred to as the drilling deck. The platform usually has a fixed crane which is used for lifting equipment off of supply boats and for repositioning equipment to various locations on the platform. A platform will frequently have a designated area for setting down equipment lifted off of supply boats by the crane. Often this designated area is a portion of the drill deck which is referred to herein as the “wing deck”.  
         [0010]     The skid beams may also be used for supporting well maintenance equipment in addition to well drilling equipment. As those skilled in the art are aware, hydrocarbon wells frequently require a rig for well maintenance, such as well clean out, casing repair, replacement of downhole production equipment, additional perforating, well stimulation, or other maintenance operations generally referred to as “work overs.” The substructure of a maintenance rig is typically erected on the skid beams in similar fashion as a modular drilling rig.  
         [0011]     An embodiment of an apparatus for protecting the wellhead and other production facilities during mobilization and operation of either well drilling or well maintenance equipment comprises a first support beam which overlays at least a portion of the first skid beam and a second support beam overlaying at least a portion of the second skid beam. The first support beam and the second support beam each have a top surface adapted for receiving either well drilling or well maintenance equipment, such as a drilling rig or a work-over rig. A first cross-member and a second cross-member span between the first support beam and the second support beam, where the first cross-member and second cross-member are generally in parallel relation to one another. Means for securing the ends of the first cross-member and the second cross-member to the first support beam and the second support beam are provided. At least one well cover panel spans between the first cross-member and the second cross-member. The well cover panel comprises a first side end and an opposing second side end. The well cover panel slidably overlays a portion of the first cross-member and to the second cross-member. The components of the disclosed apparatus have sufficient structural integrity to effectively shield wellheads and the associated production piping from items which may be inadvertently dropped during the relocation or operation of a drilling or workover rig.  
         [0012]     The apparatus itself may be assembled in such a manner that none of the components of the apparatus need be lifted directly over the wellheads or production piping, so that shutting in of the wells is not required for installation and placement of the apparatus. Therefore, a method of installing one or more embodiments of the apparatus is disclosed.  
         [0013]     An embodiment of the method comprises the steps of disposing a first support beam to overlay at least a portion of the first skid beam and disposing a second support beam in parallel relation to the first support beam, wherein the second support beam overlays at least a portion of the second skid beam. A first cross-member is placed so that it spans between the first support beam and the second support beam. Likewise, a second cross-member is placed so that it also spans between the first support beam and the second support beam. The first cross-member and the second cross-member are installed such that the first cross-member and second cross-member are adapted to slide in parallel relation to one another. A well cover panel is disposed between the first cross-member and the second cross-member, where the well cover panel is adapted to slide across a portion of the length of the first cross-member and a portion of the length of the second cross-member. The first support beam, the second support beam, the first cross-member, the second cross-member, and the well cover panel collectively comprise the wellhead cover assembly. The wellhead cover assembly is slid from a first position overlaying the wing deck to a second position overlaying the well bay. The well cover panel is slid to a position directly overlying the wellhead. Once the well cover panel is in place, the well drilling equipment or the well maintenance equipment may be installed on the platform. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  generally shows a fixed leg platform and how various items, including components of the disclosed apparatus, may be lifted by crane and deposited onto the platform deck.  
         [0015]      FIG. 2  schematically shows the disclosed apparatus and an erected modular drilling rig or work-over rig.  
         [0016]      FIG. 3A  shows a plan view of an embodiment of a wellhead cover assembly for positioning over a number of wellheads.  
         [0017]      FIG. 3B  shows an elevational view of the embodiment shown in  FIG. 3A .  
         [0018]      FIG. 4A  shows an embodiment of individual well cover panel.  
         [0019]      FIG. 4B  shows another embodiment of an individual well cover panel.  
         [0020]      FIG. 5A  shows an elevational view of an embodiment of a cross-member of the disclosed apparatus.  
         [0021]      FIG. 5B  shows a partial elevational view of a wellhead cover overlying the cross-member of  FIG. 5A .  
         [0022]      FIG. 6A  shows a plan view of an embodiment of the disclosed apparatus.  
         [0023]      FIG. 6B  shows a detailed view of how the support beams of the apparatus shown in  FIG. 6A  may be connected together.  
         [0024]      FIG. 7A  shows a plan view of an embodiment of a wellhead cover assembly for protecting a row of three wellheads.  
         [0025]      FIG. 7B  shows an elevational view of the embodiment of  FIG. 7A   
         [0026]      FIG. 8A  shows one means of attaching a cross-member to a support member.  
         [0027]      FIG. 8B  shows a cross-section along line  8 B- 8 B of  FIG. 8A .  
         [0028]      FIG. 9A  shows another means of attaching a cross-member to a support member.  
         [0029]      FIG. 9B  shows a cross-section along line  9 B- 9 B of  FIG. 9A .  
         [0030]      FIG. 9C  shows a top view of  FIG. 9B .  
         [0031]      FIG. 10  shows a means of securing the support beams to the skid beams.  
         [0032]      FIG. 11A  shows a side view of the locking device shown in  FIG. 10 .  
         [0033]      FIG. 11B  shows a front view of the locking device shown in  FIG. 10 .  
         [0034]      FIG. 12  shows a schematic of a platform deck, showing the wing deck area and the well bay area.  
         [0035]      FIG. 13  shows a schematic of an embodiment of the disclosed apparatus being assembled at the wing deck area.  
         [0036]      FIG. 14  shows a schematic of an embodiment of the disclosed apparatus after it has been slide into position over the well bay area.  
         [0037]      FIG. 15  shows how a leapfrog crane may be positioned in relation to the platform crane to assemble an embodiment of the apparatus. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0038]     Referring now specifically to the drawings,  FIG. 1  generally shows a production platform  10 . The platform  10  may comprise a drill deck  12  and production deck  14 . The platform may further comprise crane  16 , which may be used, among other things, for offloading materials and supplies from delivery vessels, such as workboat  18  shown in  FIG. 1 . For fixed leg production platforms such as that depicted in  FIG. 1 , hydrocarbon wells are typically drilled by a drilling rig which is erected on the drill deck  12 . After drilling is initiated for each well, the wellhead for each well is typically located at the production deck  14 . After drilling has been completed for a well, various piping fixtures are attached to its wellhead for receiving oil, gas and other fluids which may be produced from the underlying hydrocarbon reservoir and produced through the wellhead into the platform&#39;s production processing system. Usually, separation facilities on the platform separate gas from the liquids and separate water from the oil. Gas and oil may then be shipped off of the platform via pipeline or tanker.  
         [0039]     Because combustible fluids are usually produced through the wellheads, the wellheads and attached piping are usually separated from other platform facilities by one or more firewalls  21 . The space in which the wellheads and the attached piping are located is generally referred to as the wellbay  20 . The wellbay  20  commonly extends from the level of the drill deck  12  of the platform down to the level of the production deck  14 , and wellheads  26  in the wellbay are accessed from above by either a drilling rig, workover rig or a wireline unit. Wellheads  26  and firewalls  21  are schematically shown in  FIGS. 12 and 13 .  
         [0040]     When a modular drilling rig  22  is installed on a production platform  10 , the rig is designed to be positioned or “skid” over to the desired “slot” of the wellbay  20  without dismantling of the rig. As shown in  FIG. 2 , a rig  22  can usually be skidded along the length of the platform along the skid beams  28 ,  30 . In addition, a rig  22  can usually skid along the width of the platform along substructure beams  31 . The capability of the rig  22  to be moved both length-wise and width-wise above the well bay  20  allows the rig to set up over each wellhead location. Typically, in new well operations, once the rig  22  is over the desired location, the rig will drill an “open hole” to a relatively shallow depth, and surface conductor will be installed and cemented into the open hole. Once the surface conductor is in place, a wellhead is attached to the surface conductor, and blowout preventer equipment attached to the wellhead.  
         [0041]     Because of the risks of injury and pollution associated with the uncontrolled release of hydrocarbons, the wellheads and associated piping located in the wellbay  20  must be protected from items which may fall and damage the structural integrity of the wellheads or attached piping. The risk of falling equipment may be greater during operations associated with erecting or moving a modular drilling rig  22  or workover rig on the platform  10 . When a rig  22  is initially erected on a platform  10 , the usual practice is to lift the rig components off of a workboat with crane  16 . Because various rig components are extremely heavy, if the components are dropped onto either a wellhead or associated piping, the structural integrity of those items may be compromised. For this reason, current MMS regulations require that the wells on the platform be closed in at the surface (i.e. at the platform level) as well as being shut-in at the subsurface safety valve during various activities, including erection of a rig and skidding of a rig.  
         [0042]     On many platforms, the drill deck  12  adjacent to the well bay  20  comprises removable sections of relatively thin steel plate arranged in a grid pattern, where each section may be removed for accessing the wellhead  26  located below at the production deck  14 . These sections are typically rated at 250 pounds per square foot. However, the removable sections are not typically of sufficient strength to prevent penetration by a heavy falling object, such as a falling drilling rig component. Therefore, these removable sections are generally not sufficient protection for the wellheads and related piping during rig erection or rig skidding operations.  
         [0043]     The disclosed apparatus creates a steel shield over the wellbay  20  at approximately the level of the drill deck  12 . This shield should provide an acceptable departure from the MMS requirement that a platform&#39;s wells be shut-in during rig erection or skidding operations. In addition, the method of installing the disclosed apparatus itself avoids heavy lifts over the wellbay  20 , such that the wells need not be shut-in during the installation of the apparatus.  
         [0044]     On most platforms there is usually open deck space on the drill deck  12  between the first line of wells in the wellbay  20  and the nearest edge of the platform, which is usually sixteen feet or greater. This area of open deck will henceforth be referred as the wing deck  24 . The wing deck  24  is adjacent to the well bay  20 , but does not directly overlie the wellheads  26  and associated piping. Therefore, materials may usually be deposited on the wing deck  24  by the crane  16  without shutting in any wells. Thus, the wing deck  24  is often used by the crane operator for setting down materials and supplies delivered to the platform by boat  18 . The wing deck  24  may also be used for gathering and assembling the components of the disclosed wellhead protection apparatus.  
         [0045]     As shown in  FIG. 1  and explained in greater detail below, the platform crane  16  may be used to offload components of the apparatus from workboat  18  and set those components down on the wing deck  24 . Once on the wing deck  24 , an embodiment of the apparatus may be assembled and then—with the assistance of the crane, winch, or jacks—slid over the wellheads  26  located in the wellbay  20 . Alternatively, as explained below, pre-assembled components of the apparatus may be delivered to the platform  10 , placed on the wing deck  24 , and likewise positioned over the wellheads  26 .  
         [0046]     The apparatus is constructed using existing platform skid beams  28 ,  30 . The skid beams  28 ,  30  are generally disposed in parallel relation to one another as shown in  FIG. 1 . The skid beams  28 ,  30  may be several feet in height and the flanges on each side of the beams may have a width of over twenty inches. The top flange  29  of each skid beam  28 ,  30  generally extends above the drill deck  12 . The skid beams are usually supported by the platform legs  33  as shown in  FIG. 3   b . On most fixed leg platforms, the skid beams  28 ,  30  are used for installing the components of a modular drilling rig  22 . As discussed below, the top flange  29  of the skid beams  28 ,  30  generally has a plurality of longitudinal slots which may be utilized for moving and securing rig components to the skid beams.  
         [0047]     One embodiment of the protection apparatus comprises a first support beam  32  which overlays at least a portion of the first skid beam  28  as generally depicted in  FIG. 3A . Likewise, a second support beam  34  overlays at least a portion of the second skid beam  30 . The support beams  32 ,  34  may either comprise single beam lengths as depicted in  FIG. 3A , or may comprise a plurality of beam lengths assembled together as depicted in  FIG. 6A .  
         [0048]     The first support beam  32  and the second support beam  34  serve as foundational supports for the rig  22  instead of skid beams  28 , 30 , so the first support beam and the second support beam each have top surfaces, including slots configured as those in the skid beams, such that the first support beam and the second support beam are adapted to receive modular components of either a drilling rig, workover rig, or other well maintenance equipment. The apparatus further comprises a first cross-member  36  and a second cross-member  38  spanning between the first support beam  32  and the second support beam  34 , the first cross-member and second cross-member in general parallel relation to one another.  
         [0049]     At least one well cover panel  40  spans between the first cross-member  36  and the second cross-member  38 . The well cover panel  40  may be configured to slidably overlay the first cross-member  36  and the second cross-member  38 , as shown in  FIG. 7A . Utilizing the crane  16 , jacks, winch, or other known mechanical means, well cover panel  40  may be slid or lifted along cross-members  36 ,  38  to expose and allow access to the wellhead located beneath the panel.  
         [0050]      FIG. 7A  also shows how the apparatus may be assembled on a sectional basis to form a wellhead cover assembly  42 . The wellhead cover assembly comprises first support beam  32 ′, second support beam  34 ′, first cross-member  36 , second cross-member  38 , and one or more well cover panels  40 . As further shown in  FIG. 7A , the well cover panel may slidably overlay the first cross-member  36  and to the second cross-member  38   
         [0051]     As shown in  FIGS. 4A and 4B , a well cover panel comprises a first side  43  and an opposing second side  44 . The well cover panel  40  may further comprise opening  45  which would allow limited access to the wellhead beneath the panel. For example, wireline operations might be conducted through opening  45  without the need for removing the entire well cover panel  40 . Well cover panel  40  may further comprise cover  47  adapted to fit over and close opening  45 . The well cover panel may further comprise a first slide member  46  which overhangs the side of the first cross-member  36 , as depicted in  FIG. 5B .  
         [0052]     As shown in  FIG. 5B , first cross-member  36  may comprise a drain  48  attached to the side of the first cross-member. First slide member  46  may be disposed inward of the drain as shown in  FIG. 5B . The drain  48  may catch rain, seawater, rinse water, or effluent of drilling mud, oil, etc., diverting the liquids to a deck drain, separator, or other desired location. The well cover panel  40  may also comprise raised edge  49 . The raised edge  49  would act to channel any liquids to drain  48 . Cross-members  36 ,  38  may be disposed between the support beams  32 ,  34 , such that the cross-members have a slightly higher elevation at the center of the span of the cross-members to improve drainage away from the center of the wellbay  20 .  
         [0053]     It is to be appreciated that an embodiment of the disclosed apparatus may be constructed using a variety of different steps. For example, if support beams  32 ,  34  are previously attached to the skid beams  28 ,  30 , first cross-member  36  and the second cross-member  38  may be slid between the support beams from the wing deck  24  to a location overlying the wellbay  20 . This step may be modified by previously attaching connecting members  50  between cross-members together so that the cross-members  36 ,  38  may be slid as a unit between the support beams  32 ,  34  with the cross-members maintained in parallel relation to one another. Upon being slid to the desired location, the ends of the first cross-member  36  and the second cross-member  38  are secured to the first support beam  32  and the second support beam  34 . The ends may be fastened with conventional fastening means, such as welding or bolting.  
         [0054]      FIGS. 8A, 8B ,  9 A and  9 B show different means for attaching the ends of the cross-members  36 ,  38  to support beams  32 ,  34 . For example, as an alternative to welding the ends of the cross-members  36 ,  38  to support beams  32 ,  34 , the ends  52  of a cross-member may be adapted, as shown in  FIG. 8B , to abut the support beam and fastened to a fastener flange  54  with fastener  55 . Fastener flange  54  is attached to the support beam  32 ,  34 . The ends  52  of the cross-member  36 ,  38  may be tapered as shown in  FIG. 8B . As shown in  FIG. 5B , support beams  32 ,  34  may have guide  57  attached to the side of each beam to assist in aligning the support beams with the respective skid beams  28 ,  30  upon which the support beams will lay.  
         [0055]     Alternatively, as shown in  FIG. 9B , the ends  52 ′ of a cross-member  36 ′,  38 ′ may comprise a tapered end  56  which either has pin  58  attached to or set through the tapered end. Pin  58  is set within receiving flange  60  attached to support beam  32 ′, which may be formed in an upwardly facing “U” as shown in  FIG. 9B  for ease of connecting cross-member  36 ′,  38 ′ to support beam  32 ′. Of course, the materials and diameter of pin  58  should be selected as required to support the distributed weight of the apparatus and the impact loads which the apparatus might be expected to receive. Pin  58  may either be welded to tapered end  56 , or inserted in or through an opening in tapered end  56 .  
         [0056]     It is to be appreciated that the embodiment shown in  FIG. 9B , as compared to the embodiment shown in  FIG. 8B , will raise the bottom of the support beams  32 ′,  34 ′ higher off of the drill deck  12 , which allows the support beams to bend more before impacting the drill deck. For example only, a W14×109 beam impacted by a 15,000 pound load dropped from a height of twenty-four inches may cause the beam to be deflected approximately seven to eight inches at the center of the beam.  
         [0057]     Support beams  32 ,  34  are to be sized according to the loading requirements of rig  22 , and would typically be a W24×104 beam. Cross-members  36 ,  38  would typically be W14×109 beams. The well panels  40  should be of sufficient strength to resist a 20,000 load over an area of 100 ft 2  if dropped from a height of 2 feet above the panel. Therefore, the weight of the components of the apparatus will require that each component is set into place with mechanical assistance in the form of either the platform crane  16 , leapfrog crane  17 , the use of hydraulic or mechanical jacks, winches or other such devices known in the art.  
         [0058]     The choice of fastening means for attaching support beams  32 ,  34  to the skid beams  28 ,  30  and for attaching the cross-members  36 ,  38  to the support beams  32 ,  34  is dependent upon the particular platform design, with the object of eliminating or minimizing the lifting of heavy members and components over the wellbay  20 . Support beams  32 ,  34  may be single length beams which are attached to skid beams  28 ,  30  before other components of the apparatus are installed. The support beams  32 , 34  may be attached to the skid beams  28 ,  30  by known means of connecting two I-beams flange to flange, including welding, threaded fasteners or other known means.  
         [0059]     Alternatively, the cross-members  36 ,  38  may be attached to a plurality of support beams  32 ′,  34 ′ which are attached to one another end-to-end as indicated on  FIGS. 6A, 6B , and  7 A. In this embodiment, the support beams  32 ′,  34 ′ are in short sections, such as three to four feet. As shown in  FIG. 7A , the ends of each support beam  32 ′  34 ′ may be configured to have a male end  35  or a female end  37 , where the female end has a narrowed opening preventing the withdrawal of a larger portion of the male connector. As shown in  FIG. 6A , these connectors allow the support beams to be locked together on an end-to-end basis by lowering the male end  35  into the female end  37 , or lowering the female end over the male end. This feature allows a plurality of assembled wellhead cover assemblies  42  to be individually placed into position on skid beams  28 ,  30 , but once placed into position, the wellhead cover assemblies may be locked together as shown in  FIG. 6A . The support beams  32 ′,  34 ′ may also be attached end-to-end by other known fastening means such as threaded fasteners and welding.  
         [0060]     Because an assembled wellhead cover assembly  42  may be slid along the skid beams  28 ,  30  by either a crane (in combination with block and tackle), jacks, or other mechanical means, as opposed to lifting the wellhead cover assembly over the wellbay  20 , the apparatus may be installed without making any crane lifts over the wellbay. The wellhead cover assemblies  42  may be assembled at a site remote from the platform and delivered by workboat  18  in an assembled configuration as indicated on  FIG. 1 . The completed assemblies may then removed from the work boat  18  by either the platform crane  16  or a leapfrog crane  17 , and set upon wing deck  24  or other location at which the lift may be made without swinging a load over the wellbay  20 . Depending upon the location of the wing deck(s)  24  of the platform and the reach of the platform crane  16 , it may be necessary to utilize a leapfrog crane  17  to place the wellhead cover assembly  42  at the desired location. Alternatively, the wellhead cover assemblies  42  may be assembled entirely on the platform, such as on the wing deck  24 , and placed in position as discussed above.  
         [0061]     Once a wellhead cover assembly  42  is placed at the desired location along the skid beams  28 ,  30 , the support beams  32 ′,  34 ′ are fastened to the skid beams. Conventional fastening means, such as welding and threaded fasteners may be used for this purpose. Alternatively, a temporary locking device may be used, which facilitates attachment and detachment of the support beams  32 ′,  34 ′ from the skid beams  28 ,  30 . The skid beams  28 ,  30  usually have a series of slots  62  in the top flange  29 . The slots  62  are generally used for attaching and skidding modular rig components to the skid beams  28 ,  30 . The slots generally have dimensions of approximately two inches in width by six inches in length. As shown in  FIG. 10 , slots  62  may be used in conjunction with a generally corresponding and overlapping slot  64  in the bottom flange  66  of support beam  32 ′. Slide lock  68  may then be used to lock support beam  32 ′ to skid beam  28  by inserting the bottom member  70  through both slot  62  and slot  64  and then sliding the lock such that bottom flange  66  and top flange  29  are sandwiched between the extended portion of bottom member  70  and the extended portion of top member  72  of the slide lock.  
         [0062]     It is to be appreciated that because support beams  32 ,  34  (and  32 ′,  34 ′) will take the place of the skid beams  28 ,  30  for contact with the substructure of drilling rig  22 , the support beams may also have a series of slots  62 ′ in the top flange similar to the slots  62  in the skid beams to accommodate the installation and skidding of the rig components.  
         [0063]      FIGS. 12 through 14  generally show the sequence of how assembled wellhead cover assemblies may be placed on the wing deck  24  and then slide into place over the well bay  20 .  FIG. 15  shows how a leapfrog crane  17  may be positioned to lift materials of a workboat  18  in the event the platform crane  16  does not have sufficient reach to lift the materials off of the boat and place the materials at the wing deck  24 .  
         [0064]     While the above is a description of various embodiments of the present invention, further modifications may be employed without departing from the spirit and scope of the present invention. For example, the size, shape, and/or material of the various components may be changed as desired. Thus the scope of the invention should not be limited by the specific structures disclosed. Instead the true scope of the invention should be determined by the following claims.