Abstract:
A method to assemble a drilling rig includes providing a base structure of the drilling rig, stacking a rig floor including a derrick on the base structure, actuating lifting cylinders to lift the rig floor above the base structure, inserting at least one first upper box between the base structure and the rig floor, and retracting the lifting cylinders to set the rig floor atop the at least one first upper box.

Description:
BACKGROUND 
       [0001]    1. Field of the Disclosure 
         [0002]    Embodiments disclosed herein relate generally to drilling rigs. In particular, embodiments disclosed herein relate to drilling rig assembly methods and apparatus. 
         [0003]    2. Background Art 
         [0004]    A drilling rig is used to drill a wellbore in a formation. Drilling rigs may be large structures that house equipment used to drill water wells, oil wells, or natural gas extraction wells. Drilling rigs sample sub-surface mineral deposits, test rock, soil and groundwater physical properties, and may also be used to install sub-surface fabrications, such as underground utilities, instrumentation, tunnels or wells. Drilling rigs may be mobile equipment mounted on trucks, tracks, or trailers, or more permanent land or marine-based structures (such as oil platforms). The term “rig,” therefore, generally refers to a complex of equipment that is used to penetrate the surface of the earth&#39;s crust. 
         [0005]    Referring to  FIG. 1 , a conventional drilling rig  30  is shown. Drilling rig  30  includes a derrick  14 , which provides a support structure for a majority of the equipment used to raise and lower a drillstring  25  into and out of a wellbore. The drillstring  25  may be an assembled collection of drillpipe, drill collars, or any other assortment of tools, connected together and run into the wellbore to facilitate the drilling of a well (drillpipe  16  is shown in joints prior to being connected together). The drillstring  25  may be raised and lower into and out of the wellbore by the draw-works  7 , which includes a spool powered by a motor or other power source  5 . A drill line  12 , which may be a thick, stranded metal cable, is run from the draw-works  7  over a crown block  13  and down through a travelling block  11 . Typically, the crown block  13  remains stationary while the travelling block  11  moves vertically with the drillstring  25 . The combination of the crown block  13  and the travelling block  11  provides a significant mechanical advantage for lifting the drillstring  25 . Further, a swivel  18  may be attached to the travelling block  11  to allow rotation of the drillstring  25  without twisting the travelling block  11 . 
         [0006]    The drilling rig  30  further includes a rotary table  20  mounted in a rig floor  21 , which is used to rotate the drillstring  25  along with a kelly drive  19 . Kelly drive  19 , attached at an upper end to the swivel  18  and at a lower end to the drillstring  25 , is inserted through the rotary table  20  to rotate the drillstring  25  (drillstring rotation shown by arrow “R”). Kelly drive  19  may be square, hexagonal, or any other polygonal-shaped tubing and is able to move freely vertically while the rotary table  20  rotates it. Alternatively, drilling rig  30  may include a top drive (not shown) in place of kelly drive  19  and rotary table  20 . Additionally, blowout preventers (“BOPs”) may be located below the rig floor  21  and installed atop a wellhead  27  to prevent fluids and gases from escaping from the wellbore. An annular BOP  23  and one or more ram BOPs  24  are shown and are commonly understood in the art. 
         [0007]    During drilling operations, drilling fluid may be circulated through the system to carry cuttings away from the bottom of the wellbore as drilling progresses. Drilling fluid may be stored in mud tanks  1  before being drawn through suction line  3  by mud pumps  4 . Drilling fluid (drilling fluid route is indicated by arrows “F”) is then pumped from mud pumps  4  through a hose  6 , up a stand pipe  8 , through a flexible hose  9 , and down into the wellbore. Drilling fluid returning from the wellbore is routed through a flow line  28  to shakers  2 , which are used to separate drill cuttings from the drilling fluid before it is pumped back down the wellbore. 
         [0008]    When designing a drilling rig, numerous factors may be taken into account. For instance, referring still to  FIG. 1 , the crown block  13  must be located high enough to pull the drillstring  25  from the wellbore for assembly or disassembly. This may require that the derrick structure  14  be built having a substantial height to have the crown block  13  high enough above the wellbore. Additionally, the rig floor  21  must be high enough off the ground to allow the blowout prevention equipment, namely BOPs  23 ,  24 , to fit beneath the rig floor  21  when mounted on the wellhead  27 . Due to these design factors, among others, the size of drilling rigs is often very large. Due to the large size, assembly of the drilling rigs may often be difficult. 
         [0009]    Different methods have been employed to assemble drilling rigs and attempt to overcome the difficulty associated with assembling very large structures having on them a substantial amount of drilling equipment. One method used is known as “box on box,” which basically uses a crane to stack large box structures on top of one another up to a certain height. The crane is then used to lift the rig floor onto the stacked boxes. After the rig floor is installed, the remaining equipment, including the derrick and blocks, must be assembled. One drawback to this assembly method is that a substantial crane is required to lift the equipment during assembly, which due to often rough terrain in remote drilling locations becomes extremely costly or even unfeasible in certain conditions. Also, assembly of a majority of the drilling equipment occurs after the rig floor is installed, and thus, must take place at the rig floor height, which may be 25-40 feet (8-12 m) off the ground. 
         [0010]    Other methods used to assemble drilling rigs are known as “swing up,” “slingshot,” or some other form of parallelogram method. Using any of these methods, the drilling rig is, in a sense, collapsed because the rig floor sits on a base near the ground with the legs laid out horizontal. A hydraulic or wireline system then pulls the structure up (the rig floor is lifted off the ground and the legs are raised to a vertical position). However, these assembly methods typically incur unusually high loads, which may increase chances of mechanical failure. Additionally, active participation of rig personnel is required during assembly. Accordingly, there exists a need for a method and apparatus for a drilling rig capable of being assembled with minimal extra equipment (e.g., cranes) and minimal rig personnel participation during assembly. 
       SUMMARY OF THE DISCLOSURE 
       [0011]    In one aspect, embodiments disclosed herein relate to a method to assemble a drilling rig, the method including providing a base structure of the drilling rig, stacking a rig floor including a derrick on the base structure, actuating lifting cylinders to lift the rig floor above the base structure, inserting at least one first upper box between the base structure and the rig floor, and retracting the lifting cylinders to set the rig floor atop the at least one first upper box. 
         [0012]    In other aspects, embodiments disclosed herein relate to a drilling rig including a base structure, lifting cylinders, and a rig floor including a derrick and drilling equipment disposed thereon, wherein the lifting cylinders are configured to extend and retract to lift the rig floor and insert at least one upper box. 
         [0013]    Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1  is a cross-sectional schematic view of a conventional drilling rig. 
           [0015]      FIG. 2  is a perspective view of a base structure of a drilling rig in accordance with embodiments of the present disclosure. 
           [0016]      FIG. 3A  is a perspective view of a rig floor installed onto the base structure of  FIG. 2  in accordance with embodiments of the present disclosure. 
           [0017]      FIG. 3B  is a front view of an entire drilling rig installed onto the base structure as in  FIG. 3A  in accordance with embodiments of the present disclosure. 
           [0018]      FIG. 3C  is a side view of the drilling rig shown in  FIG. 3B  in accordance with embodiments of the present disclosure. 
           [0019]      FIG. 4A  is a perspective view of a first upper box inserted between the rig floor and base structure in accordance with embodiments of the present disclosure. 
           [0020]      FIG. 4B  is a front view of an entire drilling rig with a first upper box inserted between the drilling rig and the base structure in accordance with embodiments of the present disclosure. 
           [0021]      FIG. 4C  is a side view of the drilling rig shown in  FIG. 4B  in accordance with embodiments of the present disclosure. 
           [0022]      FIG. 5A  is a perspective view of multiple upper boxes inserted between the rig floor and base structure in accordance with embodiments of the present disclosure. 
           [0023]      FIG. 5B  is a front view of an entire drilling rig with multiple upper boxes inserted between the drilling rig and the base structure in accordance with embodiments of the present disclosure. 
           [0024]      FIG. 5C  is a side view of the drilling rig shown in  FIG. 5B  in accordance with embodiments of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    In one aspect, embodiments disclosed herein relate to drilling rig assembly methods and apparatus that use multiple box structures stacked on top of one another to elevate the drilling rig to a certain height. Referring initially to  FIG. 5A , a perspective view of a bottom portion of a fully assembled drilling rig  100  is shown in accordance with embodiments of the present disclosure. Drilling rig  100  includes a base structure  110 , multiple upper boxes  112 ,  114 , and  116  stacked thereon, and a rig floor  102  located atop upper boxes  112 ,  114 ,  116 . Drilling rig  100  also includes lifting cylinders  108  attached to base structure  110 . Drilling rig  100  is assembled according to the following sequence. 
         [0026]    Referring to  FIG. 2 , a perspective view of a base structure  110  of a drilling rig  100  is shown in accordance with embodiments of the present disclosure. Base structure  110  may be configured as a land based structure or as an offshore platform. Base structure  110  includes at least two bottom box structures that are positioned at ground level to form a base structure from which to assemble drilling rig  100 . The bottom box structures may be configured as parallelogram truss structures or solid beams. Initially, strongback beams  104 , which are beams or girders that act as secondary support members, may rest on top of the bottom box structures of base structure  110 . The combination of the stacked bottom box structures of base structure  110  and strongback beams  104  may be about 8-10 feet in height. Additionally, base structure  110  may include lifting cylinders, or hydraulic cylinders  108 , attached thereto. Hydraulic cylinders  108  may be welded or fastened using mechanical fasteners to base structure  110 . Those skilled in the art will understand that other types of lifting cylinders may also be used, including but not limited to, pneumatic cylinders, electric cylinders, and mechanical screws. 
         [0027]    Now referring to  FIG. 3A , a perspective view of a rig floor  102  including one or more pieces installed onto the base structure  110  of the drilling rig  100  is shown in accordance with embodiments of the present disclosure. Rig floor  102  is shown installed onto base structure  110  and strongback beams  104 . Strongback beams  104  may be attached to rig floor  102 , e.g., welded or fastened with mechanical fasteners. Rig floor  102  may be positioned on base structure  110  squarely so that load points  103  of the rig floor  102  are aligned with cylinders  108  of base structure  110 . As shown in  FIGS. 3B and 3C , the rig floor  102  may include a derrick  106  (shown in  FIGS. 3A and 3B ) and all required drilling equipment installed thereon prior to being assembled onto base structure  110  (derrick and drilling equipment installed at ground level rather than at a final rig floor height). Thus, the rig floor  102  may be considered a completed rig floor with all required drilling equipment installed thereon prior to stacking the rig floor on the base structure and no further assembly may be required after the rig floor is elevated to a final height. 
         [0028]    As shown in  FIGS. 4A-4C , after the rig floor  102  is installed onto the base structure  110 , the cylinders  108  may be actuated and arms  109  of the cylinders  108  extended to contact load points  103  of rig floor  102  and elevate the rig floor  102 . After the arms  107  of cylinders  108  are fully extended, a gap may exist between the base structure  110  and the rig floor  102 . Full extension of arms  107  may be about 8 feet (about 2.5 m), thus, the gap between the base structure  110  and rig floor  102  is about 8 feet (about 2.5 m). A first upper box  112  may then be inserted into the gap created between the base structure  110  and rig floor  102 . First upper boxes  112  may also be approximately 8 feet (about 2.5 m) in height, and thus, when arms  109  of cylinders  108  are retracted, rig floor  102  immediately rests on top of first upper boxes  112 . 
         [0029]    Referring now to  FIGS. 5A-5C , a drilling rig  100  having multiple upper boxes  112 ,  114 , and  116  is shown in accordance with embodiments of the present disclosure. Additional upper boxes may be added in the same manner as the first upper box (previously described) to elevate the rig floor  102  to a desired height. To insert additional upper boxes, arms  109  (shown in  FIG. 4A ) of the cylinders  108  may be extended to contact load points  105  of first upper box  112 . Arms  109  may be completely extended, which as before, leaves a gap between the first upper box  112  and base structure  110  into which a second upper box  114  may be inserted. Subsequently, arms  109  of cylinders  108  may be retracted. Load points  105  and  107  may be hinged or slid so that they may collapse into the upper box on which they are mounted (upper box  112  and  114 , respectively) and no longer protrude outside the upper box. The load points may collapse or otherwise moved out of position so that they do not interfere with extension of arms  109  of cylinders  108 . In alternative embodiments, an additional upper box may be inserted between an elevated rig floor and the first upper box, which is stacked atop the base structure. 
         [0030]    To insert a third upper box, load points  107  of second upper box  114  may be hinged open to align with cylinders  108 . Arms  109  are completely extended, which elevates second upper box  114  and leaves a gap between the second upper box  114  and the base structure  110  into which a third upper box  116  may be inserted. Subsequently, arms  109  of cylinders  108  may be retracted. In alternative embodiments, an additional upper box may be inserted between an elevated rig floor and the second upper box, which is stacked atop the first upper box. 
         [0031]    As previously mentioned, the desired height of the drilling rig  100  may be determined by the room needed below the rig floor  102  to install blowout preventer equipment. Also, the crown block at the top of the derrick must be far enough above the ground to be able to pull the drillpipe. Those skilled in the art will understand the height requirements to meet these criteria. In certain embodiments disclosed herein, a drilling rig having a rig floor stacked on three upper boxes and a base structure (bottom boxes) may have its rig floor at a height of about 38-40 feet (8-12 m). 
         [0032]    Advantageously, embodiments of the present disclosure provide a method of assembling a drilling rig, which requires substantially less intervention from rig personnel as well as heavy lifting equipment, including larger cranes. The assembly method allows a drilling rig to be assembled in more remote locations where heavy equipment would be unable to travel. Remote drill sites may be more accessible using a drilling rig assembled using methods in accordance with embodiments disclosed herein. Therefore, rig assembly costs may be reduced and productivity costs may be increased. 
         [0033]    While the present disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the disclosure as described herein. Accordingly, the scope of the disclosure should be limited only by the attached claims.