Abstract:
Methods and apparatus for handling blowout preventer stacks. In one embodiment the handling system includes a cart, or skid, providing a base platform, a tilting frame, and a lifting frame. The stack is attached to the lifting frame, which is slidingly supported by the tilting frame, which pivots relative to the cart. The cart provides for positional adjustment of the stack in a first horizontal direction, while positional adjustment in a second, perpendicular horizontal direction is provided by a lateral adjustment mechanism coupling the tilting frame and the cart. The lifting frame can be moved vertically relative to the cart and also provides for rotational adjustment of the stack about its central axis.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority to U.S. Provisional Patent Application No. 06/467,508, filed May 2, 2003, and entitled “BOP Handling System,” which is hereby incorporated by reference herein for all purposes. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   The embodiments of the present invention relate generally to systems for handling blow out preventer (BOP) stacks. More particularly, the embodiments provide a system for transporting and handling a BOP stack during installation and removal from a wellhead. 
   Rigs used for drilling hydrocarbon wells are large, complex pieces of machinery. While drilling rigs used offshore are often integrated into a single, large platform, almost all rigs used to drill wells on land are designed to be disassembled, transported between drilling sites, and reassembled. Although some rigs may be designed to be moved by helicopter or airplane, the majority of rigs are moved by trucks and trailers. Thus, many land rigs are designed to disassemble into components suitable for transport. 
   The process of assembling a land rig for drilling operations is known as “rig up.” During rig up, all of the various components of the drilling rig are assembled and tested prior to any drilling activity taking place. The rig up procedure may last anywhere from a couple of days to more than a week, depending on the type of rig being assembled and any problems encountered during the process. Because, drilling the well can not commence until rig up is complete it is desirable to minimize the time spent assembling the drilling rig. 
   The entire rig up process must be performed in reverse in order to disassemble, or “rig down,” the rig for transportation to another location. The rig down procedures further add to the downtime that the rig spends between drilling wells. The amount of downtime spent between drilling wells is often limited by the contracts under which the rigs are operated such that any time beyond a certain limit will not be paid for by the rig lessee. Thus, any equipment or procedures available, which limit the amount of time needed for rig up and rig down activities, are desirable. 
   One of the most time consuming and labor intensive tasks during rig up and rig down is the handling of the blow out preventer (BOP) stack. BOP&#39;s are essentially large diameter, high pressure valves used to control flow out of the wellbore, a BOP stack often includes several individual BOP&#39;s assembled in series. In oilfield vernacular, the terms BOP, BOP stack, and stack are all used in referring to the BOP stack. The BOP is installed at the wellhead (beneath the drill floor) and all equipment and fluids traveling into or out of the well during drilling pass through the BOP. The BOP is the last line of defense in preventing the uncontrolled release of wellbore fluids at the surface, known as a blowout, and are therefore a critical piece of safety equipment on the rig. On large land rigs, the BOP may have a 13″ or greater bore diameter and be rated for working pressures up to and exceeding 10,000 psi. 
   In normal operations, several individual BOP&#39;s are stacked on top of one another to form a “BOP stack.” Typical stacks are tens of feet high and weigh in at tens of thousands of pounds. On most land rigs the stack is at least partially disassembled during transport because the rig has no practical means of transporting the fully assembled stack. The heavy-duty connections between individual BOP&#39;s within a stack often take hours to make or break, adding to the time needed for rig up or down. 
   Once the BOP is assembled, it must be positioned under the rig floor directly over the wellhead. This is often a delicate, time consuming operation because the large, heavy BOP stack must be moved underneath the already erected rig. The BOP must be centered on the axis of the well, which runs from the rotary table on the drill floor into the wellhead, thus potentially requiring position adjustment in two directions on the horizontal plane. The BOP stack must also be able to adjust vertically to compensate for differences in elevation of the wellhead. Furthermore, because the BOP stack normally attaches to the wellhead by a flange, which has a bolt pattern that must align with a corresponding bolt pattern on the BOP, the BOP must be allowed to rotate about its vertical axis in order to find the correct alignment with the wellhead. 
   Most BOP handling systems and methods currently being used involve transferring the BOP stack from one piece of equipment to another, such as from a skid to an overhead lifting system. Many of these overhead lifting systems, such as cranes or trolleys, involve lifting and suspending the BOP, which, like lifting any large load, consumes significant amounts of time and resources to perform safely. 
   Thus, there remains a need in the art for systems to increase the efficiency and safety of handling a BOP stack during rig up and rig down procedures. Therefore, the embodiments of the present invention are directed to methods and apparatus for providing for a BOP handling system that seeks to overcome the limitations of the prior art. 
   SUMMARY OF THE PREFERRED EMBODIMENTS 
   The preferred embodiments provide a system for handling a blow out preventer stack during transportation and installation. The handling system is a single unitized system that provides support for the stack while transporting in a horizontal position. During installation, the handling system moves the stack to a vertical position and provides for positional adjustment of the stack vertically, in two horizontal directions, and rotationally about the central axis of the stack. Hydraulic cylinders provide the forces needed to adjust the position of the stack. During handling and installation, the stack is never supported by an overhead lifting appliance or moved between one handling device and another. 
   In one embodiment the handling system includes a cart, or skid, providing a base platform, a tilting frame, and a lifting frame. The stack is attached to the lifting frame, which is slidingly supported by the tilting frame, which pivots relative to the cart. The cart provides for positional adjustment of the stack in a first horizontal direction, while positional adjustment in a second, perpendicular horizontal direction is provided by a lateral adjustment mechanism coupling the tilting frame and the cart. The lifting frame can be moved vertically relative to the cart and also provides for rotational adjustment of the stack about its central axis. 
   In certain embodiments, the cart is a wheeled cart adapted to ride on a set of rails. During transport the cart is secured on a transport skid having integral rails. The transport skid is offloaded and aligned with a set of rails installed underneath a rig. The cart is then rolled from the transport skid onto the rails until it underneath the rig and aligned with the wellhead. The stack is raised to vertical by the tilting frame and can then be adjusted and attached to the wellhead.’ 
   In other embodiments, the cart has flat skids. Once the cart is offloaded, it is slid under the rig and aligned with the wellhead. No rails are required to move the cart under the rig. The stack can then be raised to vertical and installed on the wellhead. 
   Thus, the present invention comprises a combination of features and advantages that enable it to provide for a unitized stack handling system that allows a BOP stack to be transported, handled, and installed by a single piece of equipment safely and efficiently. These and various other characteristics and advantages of the preferred embodiments will be readily apparent to those skilled in the art upon reading the following detailed description and by referring to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more detailed understanding of the preferred embodiments, reference is made to the accompanying Figures, wherein: 
       FIG. 1  is a side elevation view of one embodiment of a BOP handling system; 
       FIG. 2  is rear elevation view of the BOP handling system of  FIG. 1 ; 
       FIG. 3  is a plan view of the rotating support frame of the BOP handling system of  FIG. 1 ; 
       FIG. 4  is a plan view of one of the support frames of the BOP handling system of  FIG. 1 ; 
       FIG. 5  is a side elevation view of the BOP handling system of  FIG. 1 , shown in the shipping position; 
       FIG. 6  is a top view of the BOP handling system of  FIG. 1 , shown in the shipping position; 
       FIG. 7  is a first elevation view of a BOP being installed on a rig; 
       FIG. 8  is a top view of the BOP installation of  FIG. 7 ; and 
       FIG. 9  is a second elevation view of the BOP of  FIG. 7  being installed on a rig. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the description that follows, like parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawing figures are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. The present invention is susceptible to embodiments of different forms. There are shown in the drawings, and herein will be described in detail, specific embodiments of the present invention with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce the desired results. 
   In particular, various embodiments of the present invention provide a number of different methods and apparatus for handling a BOP stack during installation of a drilling rig. The concepts of the invention are discussed in the context of BOP handling for land rigs but the use of the concepts of the present invention is not limited to this particular application and may be applied to any BOP, or other heavy equipment, installation application. The concepts disclosed herein may find application with other rig types, such as jack-ups, floating rigs, and offshore platforms, as well as other applications to which the concepts of the current invention may be applied. 
   One embodiment of a BOP handling system  20  is shown in  FIGS. 1–6 .  FIGS. 1 and 2  show a BOP  10  vertically positioned for drilling or testing.  FIGS. 3 and 4  show details of portions of the handling system  20 .  FIGS. 5 and 6  show BOP  10  horizontally positioned for shipping. 
   Referring now to  FIG. 1  and  FIG. 2 , a BOP stack  10  is shown installed on a BOP handling system  20 . The BOP handling system  20  generally includes a cart  30 , tilting frame  40 , and lifting frame  50 . In the general operation of the handling system  20 , cart  30  provides for positional adjustment of BOP  10  in a horizontal direction indicated as arrow  22 . Tilting frame  40  supports BOP  10  as it is moved, by tilting cylinder  32 , from a horizontal shipping position to a vertical working position, and allows for the positional adjustment of BOP  10 , by lateral positioning cylinders  42 , in a horizontal direction perpendicular to arrow  22 . Lifting frame  50  allows for the positional adjustment of BOP  10 , by lift cylinders  52 , in the vertical direction of arrow  24  as well as rotational adjustment about BOP axis  12 , by rotation cylinders  54 . 
   Cart  30  serves as the base for handling system  20  and is formed on a generally rectangular skid-type structure  36  constructed of structural shapes and/or plate. Cart  30  is preferably configured and sized so as to be transported by truck, such as on a flatbed trailer. Cart  30  may include wheels  34  adapted to interface with a rail system (not shown) to reduce the force needed for horizontal positional adjustment of BOP  10 . Cart  30  also includes tilting cylinder mounts  33 , a tilting frame mount  35 , and lateral positioning cylinder mounts  37 . 
     FIG. 1  shows BOP  10  in a vertical position for drilling or testing operations. Tilting cylinders  32  have been fully extended to raise tilting frame  40 . Although once BOP  10  is attached to a wellhead or test flange it will be secured in the vertical position, tilting frame  40  may also be locked in place by the attaching a cable or bar (not shown) between tilting frame  40  and cart  30 . Referring now to  FIG. 5 , the BOP handling system  20  is shown with BOP  10  in a horizontal position for transporting. Tilting cylinders  32  are retracted so that tilting frame  40  is moved from a vertical position to a horizontal position where it is laying on cart  30 . 
   Tilting frame  40  is preferably constructed from structural shapes and/or plate and includes a vertical frame  44  that is pivotally attached to cart  30  at tilting frame mount  35 . Tilting frame  40  also includes tilting cylinder mounts  46  and lift cylinder mounts  48 . The base  60  of tilting frame  40  includes interface plates  62  that receive shaft  64 , which is retained by end mounts  65  attached to cart  30 . In alternate embodiments, shaft  64  can be fixed to end mounts  65  and rotate within plates  62  or shaft  64  may be fixed to plates  62  and rotate within end mounts  65 . 
   Tilting frame mount  35 , in conjunction with lateral positioning cylinder mounts  37  and lateral positioning cylinders  42 , also provides for lateral adjustment of the position of BOP  10  in the direction indicated by arrow  61 . As best seen in  FIG. 6 , lateral positioning cylinders  42  are attached between cylinder mounts  37  and adjustment frame  68 , which receives shaft  64  and fits between two interface plates  62 . As cylinders  42  extend and retract, adjustment frame  68  is moved, causing tilting frame  40  to move up to a distance  66  between the outermost interface plate  62  and end mounts  65 . 
   Referring back to  FIG. 1 , lifting frame  50  is also constructed from structural shapes and/or plate and is adapted to slidingly engage tilting frame  40  and be vertically supported by lift cylinders  52 , which are attached at cylinder mounts  53 . Lifting frame  50  includes a vertical structure  51  to which lower support frame  55 , middle support frame  56 , and upper support frame  57  are attached. The support frames  55 ,  56 ,  57  attach to BOP  10 , preferably at the BOP&#39;s flange connections, and supports the BOP during transportation and installation. Upper support frame  57  also supports rotating support plate  58 , which is rotated relative to upper support frame  57  by rotation cylinders  54 . 
   Referring now to  FIG. 3 , a top down view of middle support frame  56  is shown. Middle support frame  56  is identical to lower support frame  55  except that lower support frame  55  includes structure tying the frame to vertical frame  44  while middle support frame  56  is attached directly to vertical frame  51 . Middle support frame  56  includes base portion  70  and an arcuate hinged door  72  that combine to form a circular enclosure  71  for accommodating BOP  10 . Hinge  74  allows door  72  to be moved from an open position  73  wherein the door can be held open by pin connection  76 . In the closed position, bolted connection  78  securely attaches door  72  to base  70 . 
   Referring now to  FIG. 4 , upper support frame  57  is shown including rotating support plate  58  and rotation cylinders  54 . Upper support frame  57  includes base portion  80  and an arcuate hinged door  82  that combine to form a circular enclosure  81  for accommodating BOP  10 . Hinge  84  allows door  82  to be moved from an, open position  83  and a closed position where bolted connection  88  securely attaches door  82  to base  80 . Bolts or pins  86 , protrude from the upper surface of upper support frame  57  and interface with slots  59  in rotating support plate  58 . 
   When BOP  10  is in the vertical position, and not installed on the wellhead or a test flange, the weight of BOP  10  rests on support plate  58 . Rotation cylinders  54  are actuated in an opposing manner such that the extension of one cylinder is coincident with the retraction of the other cylinder. This opposing actuation causes support plate  58  to rotate about the center of enclosure  81 . Because BOP  10  is being supported by plate  58 , the BOP also rotates about its central axis. This rotation is critical to allow the alignment of the bolt pattern on the base flange of BOP stack  10  to align with the bolt pattern on the wellhead flange. 
     FIGS. 7–9  show a BOP  130  being installed on a rig beneath a drill floor  100 , which is supported by rig structure  110 .  FIG. 7  shows BOP  130  installed on a BOP handling system  120 . Handling system  120  includes a cart  140 , a tilting frame  150 , a lifting frame  160 , a rotating support  170 , and a lateral shifting system  180 . Cart  140  may preferably be wheeled and adapted to be transported on a transport skid  190  that has integral rails adapted to interface with the wheels of cart  140 . In alternate embodiments, cart  140  may be a simple skid and not utilize a transport skid  190 . 
   Handling system  120 , with BOP  130  installed, is transported, such as by truck, on transport skid  190 . Cart  140  rides on rails integrated into skid  190  and is fixed to the skid during transport to prevent cart  140  from rolling. Once handling system  120  arrives at a drilling site, the system, including BOP  130  and transport skid  190  is offloaded and aligned with installation rails  200  in place under drill floor  100 . Transport skid  190  may be placed at either end of rails  200 . 
   Cart  140  is released from transport skid  190  and handling system  120  is rolled to the proper position under the drill floor, as is shown in  FIG. 8 . Air tuggers, winches, or other equipment may be used to move handling system  120  to the proper position. In those embodiments in which cart  140  is not wheeled, system  120  is simple dragged along the ground until it is properly positioned under the drill floor. 
   Once cart  140  is satisfactorily positioned, tilting cylinder  152  is extended to rotate tilting frame  150  from a horizontal horizontal to a vertical position, as shown in  FIG. 9 . Once BOP  130  is vertical, lifting frame  160  can be used to adjust the vertical position of the BOP relative to the wellhead or test flange. Lateral shifting system  180  provides adjustment of the position of BOP  130  in a horizontal direction perpendicular to the direction cart  140  moves, and cart  140  can be further moved to fine tune the position of BOP relative to the wellhead or test flange. Rotating support  170  is provided to allow rotational alignment between the mating bolt patterns of BOP  130  and the wellhead or test flange to which it connects. Retaining member  154  can be connected between cart  140  and tilting frame  150  to further support BOP  130  once installation is complete. 
   In the preferred embodiments, the position of BOP  130  is achieved through hydraulic control of the various positioning functions. In this manner, a single control panel could be provided allowing a single operator to position BOP  130  from a remote location. BOP handling system  120  also eliminates the need for shifting the load of BOP  130  between different lifting or handling appliances and the BOP is never suspended from an overhead lifting appliance. 
   Another advantage of BOP handling system  120  is that, since BOP  130  is transported and installed fully assembled, the connections between components of the BOP stack do not have to be made or broken during a rig move. Additionally, the hydraulic hoses and plumbing supplying hydraulic functions on BOP stack  130  can also remain installed, potentially simplifying the connection of the BOP to the rig control system. 
   The embodiments set forth herein are merely illustrative and do not limit the scope of the invention or the details therein. It will be appreciated that many other modifications and improvements to the disclosure herein may be made without departing from the scope of the invention or the inventive concepts herein disclosed. Because many varying and different embodiments may be made within the scope of the present inventive concept, including equivalent structures or materials hereafter thought of, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.