A method for erecting a drilling rig and an apparatus therefor having a mast, a base, a floor support, legs arranged between the base and the floor support, a primary lifting ram in engagement with the mast, and a floor support lifting ram, is disclosed. The method involves raising the mast with the primary lifting ram, raising the floor support with the floor support lifting ram to an intermediate height, engaging the primary lifting ram with the floor support and raising the floor support from the intermediate height to full working height with the mast lifting ram.

BACKGROUND 
       [0001]    This disclosure relates to a method and apparatus for erecting a drilling rig and particularly, but not exclusively, to land rigs for drilling and servicing oil and gas wells. 
         [0002]    A variety of drilling rigs may be used in drilling and various wellbore operations; for example, and not by way of limitation, U.S. Pat. Nos. 3,340,938; 3,807,109; 3,922,825; 3,942,593; 4,269,395; 4,290,495; 4,368,602; 4,489,526; 4,569,168; 4,837,992; 6,634,436; 6,523,319, the entire contents of which are hereby incorporated by reference herein for all purposes. 
         [0003]    In many land drilling operations, land rigs may be delivered to a site, assembled and then disassembled. Land rig components may be easily transported and assembled. Costs associated with land rigs and associated equipment, can be calculated on a per hour or per day basis, and, therefore, efficient takedown, transport, and setup operations may be desirable. See example patent/applications U.S. Pat. No. 3,922,825; U.S. Pat. No. 3,942,593; U.S. Pat. No. 6,634,436; WO 2009/001133; WO 2009/106860; and WO 2009/106897, the entire contents of which are hereby incorporated by reference herein for all purposes. 
       SUMMARY 
       [0004]    In accordance with the present disclosure, there is provided a method for erecting a drilling rig having a mast, a base, a floor support, legs arranged between the base and the floor support, a primary lifting ram in engagement with the mast and a floor support lifting ram, the method comprising raising the mast with the primary lifting ram, characterised in that the method further comprises raising the floor support with the floor support lifting ram to an intermediate height, engaging the primary lifting ram with the floor support and raising the floor support from the intermediate height to full working height with the mast lifting ram. Preferably, the intermediate height is between ground level and a working height. It should be noted that the mast is lifted with the floor support structure. The present disclosure is particularly useful for drilling rigs with very high rig floor substructure heights. 
         [0005]    Advantageously, the primary lifting ram has a lower end and an upper end the method further comprising moving the upper end from engagement with the mast to engagement with the floor support. Preferably, the lower end of the primary lifting ram is rotatably connected to the base, the method further comprising rotating the primary lifting ram between engagement with the mast and engagement with the floor support. 
         [0006]    Preferably, the base has a central portion, a front portion and a rear portion, the primary lifting ram is rotatably connected to the base in the central portion. Advantageously, the base has a central portion, a front portion and a rear portion, the floor lifting ram is rotatably connected to the base preferably, in the rear portion. Each of the front, central and rear portions are preferably each approximately a third of the length of the base. 
         [0007]    Preferably, the floor support and the base are locked together, the method further comprising unlocking the floor support from the base after the mast is raised and before the floor support is raised. The floor support and base preferably comprise a lock to lock the base and the floor support together whilst the mast is being raised. The lock may comprise a pinned connection wherein each of the base and floor support may comprise lugs with holes therein for receiving a pin. Alternatively or additionally, the floor lifting ram may be provided with a hydraulic lock or a pinned connection to pin cylinders and pistons together to inhibit the floor support from moving relative to the base whilst the mast is being raised. Preferably, the primary lifting ram and the floor lifting ram comprise hydraulically actuated concentric telescoping cylinders, although they may be of the following: pneumatic; part pneumatic and part hydraulic; mechanical comprising, for example, a toothed cog or cogs running along a toothed track or a screw jack; electrical comprising, for example a linear actuator power. 
         [0008]    Preferably, the method further comprises disengaging the floor support lifting ram from the floor support after the floor support has been engaged by the primary lifting ram and preferably, before the primary lifting ram raises the rig floor to the final working height. 
         [0009]    Advantageously, the primary lifting ram extends whilst raising the mast, the primary lifting ram following an arc as it extends passing over vertical. Preferably, the primary lifting ram starts at an acute angle with the ground of preferably between ten and fifty degrees, most preferably, between twenty-five and thirty-five degrees and advantageously thirty degrees. Advantageously, the primary lifting ram finishes with an angle of preferably between fifty and ninety degrees from horizontal and most preferably, seventy degrees. Preferably, the floor support lifting ram starts at an angle of forty degrees and finishes at an angle of approximately sixty degrees. 
         [0010]    Advantageously, the method further comprises installing at least one or more of the following before raising the rig floor support commences: a rig floor center section; a pipe rack; an iron roughneck; pipe handling equipment; a drawworks; and a dog house. 
         [0011]    Preferably, the method further comprises installing at least one or more of the following before raising the mast commences: racking board; stabbing board; crown block; top drive track. 
         [0012]    The present disclosure also provides an apparatus, such as a drilling rig under construction comprising a mast, a base, a floor support, legs arranged between the base and the floor support, a primary lifting ram connected to the base and a floor lifting ram connected to the base characterised in that the primary lifting ram is connected to a central portion of the base. The central portion of the base is preferably between the legs and advantageously, beneath the floor support when erected and preferably, beneath the floor support or substantially in line with or within one meter of a front of the floor of the support before erection of the mast commences. 
         [0013]    Preferably, the apparatus further comprises an engaging member on the floor support for receiving an upper end of the primary lifting ram. The engaging member may be a pin welded to the floor support and advantageously, the engaging member may be fixed to any member fixed to the floor support, such as a mast shoe or a lug. Preferably, the connections between the lifting rams and the base, mast and floor support are rotatable connection and advantageously comprise a pin and most advantageously, lugs, preferably with holes therein. 
         [0014]    Advantageously, the mast is pivotably connected to the floor support, most preferably on a mast shoe. 
         [0015]    The present disclosure also provides a drilling rig under construction for use in the method of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    For a better understanding of the present disclosure, reference will now be made, by way of example, to the accompanying drawings, in which: 
           [0017]      FIG. 1  is a side schematic view of a land rig in accordance with the present disclosure, the land rig shown erected, with parts removed to show otherwise hidden detail; 
           [0018]      FIG. 2  is a front schematic view of the land rig shown in  FIG. 1 , with parts removed to show otherwise hidden detail; 
           [0019]      FIG. 3  is a top view of part of the land rig shown in  FIG. 1 , with the mast removed to show otherwise hidden detail; 
           [0020]      FIG. 4  is a side schematic view of part of the land rig shown in  FIG. 1 , at a first stage of erection; 
           [0021]      FIG. 5  is a side schematic view of part of the land rig shown in  FIG. 1 , at a second stage of erection; 
           [0022]      FIG. 5 a    is an enlarged part of  FIG. 5 ; 
           [0023]      FIG. 6  is a side schematic view of part of the land rig shown in  FIG. 1 , at a third stage of erection; 
           [0024]      FIG. 7  is a side schematic view of part of the land rig shown in  FIG. 1 , at a fourth stage of erection; 
           [0025]      FIG. 8  is a side schematic view of part of the land rig shown in  FIG. 1 , at a fifth stage of erection; and 
           [0026]      FIG. 9  is a side schematic view of part of the land rig shown in  FIG. 1 , at a sixth stage of erection. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]      FIGS. 1, 2 and 3  show a land rig  10  in accordance with the present disclosure which includes a substructure  12  and a mast  14 . 
         [0028]    The substructure comprises two side structures  16  and  18 . Each side structure  16  and  18  has a base  20  and  22  and a floor support structure  24  and  26 . Legs  30  and  32 , a strut  36  and telescopic locking legs  28  and  34  are arranged between the base  20  and the floor support structure  24  on an outer side  37  of the side structure  16 . A similar arrangement of legs, generally identified by reference numeral  38  is on an inner side  39  of the side structure  16 . Similarly, an arrangement of legs  40  is arranged between base  22  and floor structure support  26  on the outer side  41  of the side structure  18  and a similar arrangement of legs, generally identified by reference numeral  42  is on an inner side  43  of the side structure  18 . 
         [0029]    The two side structures  16  and  18  are spaced by spacer pole(s)  44  connected between bases  20  and  22 . A rig floor center section  45  sits between and is supported by the floor support structures  24  and  26 . 
         [0030]    The mast  14  comprises two front mast legs  46  and  47  and two rear mast uprights  48  and (not shown). Structural latticework  49  is arranged between the front legs  46  and  47  and the two rear mast uprights  48  and (not shown). Structural latticework may also be arranged between the two front mast legs  46  and  47  and between the two rear mast uprights  48  and (not shown), although structural latticework is arranged not to obstruct the V-door opening, so that tubulars and downhole tools can be moved from storage off-rig into pipe setback  50  and to mouse hole  51   a  and well center  52 . A rat hole  51  is provided for a Kelly (not shown) for use in a rotary table (not shown). One side of the mast  14  may be substantially free of latticework to allow tubulars and other equipment move freely to and from alignment with well center  52  and on and off rig. 
         [0031]    Pinned connections are provided at each foot of the front mast legs  46  and  47 . Each foot is pinned to lugs  46   b  and  47   b  of mast shoes  46   c  and  47   c  supported by the side structures  16  and  18 . Each shoulder  48   a  and (not shown) of the two rear mast uprights  48  and (not shown) has a lower strut  49   a  angled to return to foot  46   a  and  47   a . A gin pole  48   b  and (not shown) is arranged between shoulder  48   a  and (not shown) and lug  49   d  and  50   d  of mast shoes  49   c  and  50   c  respectively. 
         [0032]    A wireline  53  is arranged around a reel  54  of a drawworks  55  arranged on the rig floor  45  or on a skid  56  supported between the floor support structures  24  and  26 . The wireline  53  passes over a crown sheave or block  57  to a travelling block  58  for raising and lowering a top drive  60  on a track  61  over well center  52 . Racking board  62  and stabbing board  63  are hinged to the mast  14  and supported by racking board support poles  64  and stabbing board poles  65  respectively. A mud flow line  65 a is arranged along front mast leg  47 . Tubulars, such as drill pipe  66  and casing  67  is conveyed from an off-rig storage stock pile (not shown) to pipe setback  50  using a pipe conveyor  68  and pipe handling equipment  71  and  72 . The pipe handling equipment  71  and  72  are arranged on front corners of the rig floor center section  45 . Other tools, such as iron roughnecks  69  and  70  are arranged on the rig floor center section  45  about well center  52  and mousehole  51  for making up stands of drill pipe. 
         [0033]      FIG. 4  shows a first stage of erection of the land rig  10  shown in  FIGS. 1 to 3 . The two side structures  16  and  18  have been off-loaded from one or more trucks. Each base  20  and  22  of each side structure  16  and  18  is arranged on the ground and placed parallel and in concert with one another at a predetermined spacing. Fixing the spacer pole  44  between the two bases  20  and  22  confirms the two side structures  16  and  18  are spaced correctly. Each floor support structure  24  and  26  is arranged on top of respective base  20  and  22 . The floor support structures  24  have a width and an underneath provided with a lug  80  and (not shown) attached on each side. A top lug  81  of leg  30  is rotatably pinned to lug  80 . Top lug  82  of the telescopic leg  28  is also rotatably pinned to lug  80 . Bottom lug  83  of leg  30  is rotatably pinned to a foot lug  84  in a middle portion  85  of the base  20 . A bottom lug  86  of telescopic locking leg  28  is rotatably pinned to a foot lug  87  in rear portion  88  of the base  20 . The telescopic locking leg  28  is in a retracted position. The floor support structures  24  a front end lug  90  and (not shown) on each side of a front end. The front end lug  90  has a top lug  91  of telescopic locking leg  34  rotatably pinned thereto. Bottom lug  92  of telescopic locking leg  34  is rotatably pinned to a foot lug  93  on a front portion  94  of the base  20 . A top lug  95  of leg  32  is rotatably pinned to a pin  96  in a side wall  97  floor support structures  24  and a bottom lug  98  of leg  32  is rotatably pinned to a foot lug  99  fixed to the front portion  94  of the base  20 . 
         [0034]    A primary lifting ram  100  is arranged between the two sides of side structure  16 . The primary lifting ram  100  has an outer cylinder  100   a  with a lower ram lug  101  fixed thereto. The lower ram lug  101  is rotatably arranged on a lower ram axel  102  fixed between the two sides of side structure  16  in the central portion  83  of base  20 . An upper ram lug  103  is fixed on an inner cylinder  104  of primary lifting ram  100 . The primary lifting ram  100  may have one or more concentric intermediate cylinders  105  for telescoping a predetermined distance. The upper ram lug  103  is rotatably pinned to a mast lug  106 . The mast lug  106  is advantageously located on the front leg  46 , preferably at a point below and advantageously between the center of gravity  108  and the foot of the front mast leg  46 . The center of gravity symbol identified by reference numeral  108  shows the position of the center of gravity of the mast  14  and anything else attached thereto at this stage of erection, such as the crown block  57 , gin poles  49   b  and racking and stabbing boards  62  and  63 . 
         [0035]    A primary lifting ram  110  is located between sides of side structure  18  in a similar manner to the primary lifting ram  100  in side structure  16 . A further mast lug (not shown) is fixed on the other front mast leg  47  and an upper ram lug  111  (see  FIG. 3 ) is rotatably pinned thereto. A lower ram lug  112  is similarly rotatably pinned to a foot lug (not shown). Front mast legs  46  and  47  are rotatably pinned to lugs  46   b  and  47   b  respectively and the mast lies substantially horizontally. A top portion of the mast  14  rests on a dolly (not shown), part of a truck (not shown) or other suitable rest. The gin poles  49   b  and (not shown) are connected to a lower portion of the mast  14 . 
         [0036]    The primary lifting rams  100  and  110  may, for example be 18″ (457 mm) two stage cylinder having outer cylinder  100   a  with a first stage bore size of 18″ (457 mm), an intermediate cylinder  105  with a second stage bore size of 15″ (381 mm). The primary lifting rams  100  and  110  may, for example have a full extend length  46 ′ (14 m), working pressure 2600 psi (180 bar). The primary lifting rams  100  and  110  are preferably driven by hydraulic fluid flowing into the cylinders  124 , 125  and  126  and advantageously by a common supply, such that the primary lifting rams operate in unison. 
         [0037]    Referring to  FIG. 5 a   , there is shown an enlarged view of part of the apparatus shown in  FIG. 5 , wherein a locking lug  115  is fixed to the underneath of the floor support structure  24 . A further locking lug  116  is provided on a rear end of the base  20 . A pin  117  is provided to lock the base  20  to the floor support structure  24 . 
         [0038]    The primary lifting rams  100  and  110  are activated simultaneously to extend from a fully refracted position. As the primary lifting rams  100  and  110  extend, the mast  14  is raised about pinned connection  46   c  and  47   c . The primary lifting rams  100  and  110  sweep across an arc of preferably eighty degrees, starting from a two o'clock position (approximately thirty degrees from horizontal) anti-clockwise as viewed in  FIGS. 4 to 6 , through a twelve o'clock position, over-vertical to a twenty minutes past eleven o'clock position (approximately seventy degrees from horizontal) when the primary lifting rams  100  and  110  are fully extended, whereupon feet of gin poles  49   b  and (not shown) meet the mast shoes  49   c  and  50   c  and are pin connected together. 
         [0039]    Upper ends of the primary lifting rams  100  and  110  are disconnected from the mast lugs  106  and (not shown), retracted and rotated about pin connection  101 , 102  to lie down on the base  20 , as shown in  FIG. 7 . 
         [0040]    Pin  117  of the locking lug  115  is removed to unlock the base  20  from the floor support structure  24 . 
         [0041]    Each floor lifting ram  120  and (not shown) is arranged within each side structure  16  and  18 . Each floor lifting ram  120  and (not shown) has a lower cylinder  124  of small diameter having a lower end provided with a lower lug  121  rotatably pinned to a side of the rear portion  88  of the base  20 . Each floor lifting ram  120  and (not shown) also has an intermediate cylinder  125  and an upper cylinder  126  of large diameter. The upper cylinder has an upper end provided with an upper lug  122 , which is rotatably pinned to a mast shoe lug  123  fixed to or formed integrally with the mast shoe  46   c.    
         [0042]    The floor lifting rams  120  and (not shown) may, for example be 18″ (457 mm) two stage cylinder having outer cylinder  100   a  with a first stage bore size of 18″ (457 mm), an intermediate cylinder  105  with a second stage bore size of 15″ (381 mm). The lifting rams  100  and  110  may, for example have a full extend length of 28′ 6″ (8.7 m), working pressure 2600 psi (180 bar). The floor lifting rams  120  and (not shown) are preferably driven by hydraulic fluid flowing into the cylinders  124 , 125  and  126  and advantageously by a common hydraulic supply, such that the lifting rams operate in unison. 
         [0043]    The floor lifting rams  120  and (not shown) are activated simultaneously to raise the floor support structures  24  and  26  and everything supported thereby or thereon to an intermediate height, such as  5 m. At this stage, any or all of the following may be on or supported by the floor support structures  24  and  26 : drawworks  55 , pipe setback  50 , iron roughnecks  69 ,  70 , top drive  60 , top drive tracks  61 , center floor section  45 , dog house (not shown), rotary table (not shown) etc.. 
         [0044]    Referring to  FIG. 8 , each of primary lifting rams  110  and  120  is swung about pinned connection  101 ,  102 . The upper lug  103  is connected to a pin connection  127  in a side wall of the floor support structure  24  and similarly an upper lug of primary lifting ram  120  is connected to a pin connection in a side wall of the floor support structure  26 . 
         [0045]    The floor lifting rams  120  and (not shown) are disconnected from the floor support structures  24  and  26  by removing upper lug  122  from mast shoe lug  123 . 
         [0046]    The primary lifting rams  100  and  110  are activated simultaneously to raise the floor support structures  24  and  26  and everything supported thereby or thereon to working height, for example 10 m. Telescopic legs  28  and  34  are locked in their extended position by pins located through holes (not shown). The primary lifting rams  100  and  110  are then disconnected from the floor support structures  24  and  26 . The strut  36  is added and fixed between the central portion  83  of the base  20  and the floor support structure  24 . Similarly, a further strut (not shown) is added between base  22  and floor support structure  26 . All of the primary and floor lifting rams  100 ,  110 ,  120  and (not shown) can now to laid down on the bases  20  and  22  or removed therefrom. 
         [0047]    The mast  14  may be any suitable known type, such as a single-piece, multi-piece, and/or telescoping type. 
         [0048]    It will be appreciated by those skilled in the art that the techniques disclosed herein can be implemented for automated/autonomous applications via software configured with algorithms to perform the desired functions. These aspects can be implemented by programming one or more suitable general-purpose computers having appropriate hardware. The programming may be accomplished through the use of one or more program storage devices readable by the processor(s) and encoding one or more programs of instructions executable by the computer for performing the operations described herein. The program storage device may take the form of, e.g., one or more floppy disks; a CD ROM or other optical disk; a read-only memory chip (ROM); and other forms of the kind well known in the art or subsequently developed. The program of instructions may be “object code,” i.e., in binary form that is executable more-or-less directly by the computer; in “source code” that requires compilation or interpretation before execution; or in some intermediate form such as partially compiled code. The precise forms of the program storage device and of the encoding of instructions are immaterial here. Aspects of the invention may also be configured to perform the described functions (via appropriate hardware/software) solely on site and/or remotely controlled via an extended communication (e.g., wireless, internet, satellite, etc.) network. 
         [0049]    While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. Many variations, modifications, additions and improvements are possible. For example, various combinations of the features provided herein may be provided. 
         [0050]    Plural instances may be provided for components, operations or structures described herein as a single instance. In general, structures and functionality presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the inventive subject matter.