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BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to installing or running wellbore tubulars such as casing into a wellbore and, more particularly, to a modular handling tool system for holding and lowering the wellbore tubulars into the wellbore. 
     2. Description of the Background 
     A string of wellbore tubulars such as casing, depending on the length and type of tubular elements, may weigh hundreds of thousands of pounds. Despite this significant weight, the casing string must be carefully controlled as it is interconnected and lowered into the wellbore. To further complicate this function, wellbore tubulars, such as casing, come in a wide range of diameters and weights. In some cases, the casing may have a relatively thin wall that can be crushed if too much force is applied thereto. 
     Pneumatic and/or hydraulic casing tools are large gripping devices used for holding and lowering the wellbore tubulars, such as casing, into the previously drilled open hole. These gripping tools may weigh several tons depending on the size and type of slips used therein. The casing tools are typically used in sets comprising one elevator slip assembly and one spider slip assembly. The elevators slip assembly is translationally moveable with respect to the spider slip assembly. The elevator slip assembly is carried by the traveling block. The spider slip assembly may be a flush mount spider used on the drill floor with a rotary drive such as by replacing the master bushing. On the other hand, the spider assembly construction may need to provide a top mount spider that is mounted on the top of the rotary table or drill floor and which may be used with a scaffold or the like. Pneumatic and/or hydraulic control equipment is provided to operate the slips in the elevator slips assembly and in the spider assembly. Numerous pneumatic/hydraulic control lines are used to interconnect and operate the elevator slips assembly and the spider assembly. 
     To limit any downtime costs due to damage, maintenance, or repairs, it is generally desirable to provide on the rig site location backup or redundant gripping tools for both the elevator slip assembly and also for the type of spider slip assembly used. Thus, at least four tools are generally necessary at the rig site. The rental costs for having four large, rather complicated, tools on location can be substantial although such costs are preferable to the possibility of having one tool damaged without a spare on location. Due to the size and availability, considerable time may be needed to obtain a replacement. To save costs, it would be desirable to reduce such redundancy requirements while still maintaining the system reliability afforded by 100% redundancy. 
     Various prior art exists that is related to such gripping tools including U.S. Pat. No. 5,909,768, issued Jun. 8, 1999, to Castille et al., which discloses an exemplary apparatus for optimally gripping and releasing a tube. The apparatus has an elevator with a set of slips for optionally gripping and releasing a tube and a spider with a set of slips for optionally gripping and releasing the end of the tube. The elevator and spider slips are in communication with each other by pressurized conduits. The conduits form a pressure circuit to supply pressure to release one set of slips only when the other set of slips is gripping the tube, wherein the apparatus has improved response time. The spider may be hydraulically or pneumatically actuated and the elevator may be pneumatically operated. The spider may be flush mounted. 
     Other prior art patents may include U.S. Pat. Nos. 3,215,203; 3,708,020; 3,722,603; 4,676,312; 4,842,058, and 5,343,962. 
     The above referenced prior art does not disclose means for eliminating the need for having two backup tools at the rig site. It would be desirable to provide 100% redundancy for both the spider and the elevator without the need for two backup tools at the rig site. Eliminating even the fourth backup tool would clearly provide a significant 25% economy for both the vendor and the customer. Those skilled in the art have long sought and will appreciate the present invention which addresses these and other problems. 
     SUMMARY OF THE INVENTION 
     The present invention was designed to provide more efficient operation to thereby reduce drilling costs due to decreased equipment needs on location or in the provider&#39;s warehouse. Manufacturing costs are reduced due to lower cost of building duplicate items rather than multiple items. Therefore, it is an object of the present invention to provide an improved handling system for holding and lowering wellbore tubulars, especially large tubulars such as casing, into the wellbore. 
     Another object of the present invention is to provide a handling system with 100% redundancy using fewer components. 
     Yet another object of the present invention is to provide a handling system with few different components. 
     Yet another object of the present invention is to reduce storage costs. 
     A feature of the present invention is a plurality of interchangeable gripping sections. 
     An advantage of the present invention is reduced operational and manufacturing and storage costs. 
     These and other objects, features, and advantages of the present invention will become apparent from the drawings, the descriptions given herein, and the appended claims. However, the invention is not limited to these objects, features, and advantages. 
     Therefore, the present invention provides for a handling system for holding and lowering wellbore tubulars for use with a rig having a traveling block and a rig floor. The system comprises at least two gripping modules that may preferably be substantially identical so as to be interchangeable with each other. The at least two gripping modules each have a bowl section and each have a plurality of slips moveable within the bowl section. An elevator adaptor is provided that has at least one connector for coupling to the traveling block. The elevator adapter is attachable with either one of the at least two gripping modules while another of the at least two gripping modules may be attachable to the rig floor. The elevator adaptor preferably defines a bore therein for receiving either one of the at least two gripping modules. The connector for the elevator module may further comprise lifting ears. 
     A third gripping module may preferably be provided for use in substituting with either of the at least two gripping modules so as to provide system redundancy. 
     A top mount module may be mountable to the rig floor and is attachable to either of the at least two gripping modules. The top mount body preferably defines a bore therein for receiving either of the at least two gripping modules. 
     The at least two gripping modules each preferably have a weight supporting shoulder or flange or ring extending radially outwardly for supporting a weight of the wellbore tubulars. The elevator adaptor has an engagement surface for contacting the weight supporting shoulder of either of the at least two gripping modules. 
     A plurality of slips is preferably longitudinally moveable within each of the at least two gripping modules. A sloping bottom surface within each of the at least two gripping modules is angled with respect to an axis through each of the at least two gripping modules. The sloping surface forms a stop surface for supporting and preventing further longitudinal movement of the plurality of slips toward a gripping position. 
     Thus, a plurality of rings are preferably within each of the at least two gripping modules. A plurality of slips are provided for each of the at least two gripping modules with each slip having substantially sawtooth set of camming surfaces for camming engagement with the plurality of rings. 
     A method is for a wellbore tubular handling system for installing wellbore tubulars in a wellbore. The method may preferably comprise providing at least two gripping modules for gripping wellbore tubulars, selecting either of the at least two gripping modules for attachment to the traveling block, and selecting either of the at least two gripping modules for attachment to the rig floor. In one preferred embodiment, the method comprises supplying at least three gripping modules at the rig for gripping wellbore tubulars such that the at least three gripping modules are interchangeable for attachment to either the traveling block or the rig floor. One of the at least three gripping modules provides redundancy for the other two of the at least thee gripping modules. The attachment to the traveling block further comprises providing an elevator module for interconnection between the traveling block and either of the at least two gripping modules. 
     In one example of operation, the attachment to the rig floor further comprises a top mount module for interconnection between the rig floor and either of the at least two gripping modules. However, the attachment to the rig floor could also comprise a flush mount adaptor ring for interconnection between the rig floor and either of the at least two gripping modules. 
     In operation, the method may typically comprise providing at least three gripping modules that are substantially identical so as to be interchangeable with each other, supplying the rig with the at least three gripping modules, and also supplying the rig with a tool for attaching any one of the three gripping modules for use with the traveling block. 
     Thus, one preferred embodiment of the handling system of the present invention comprises a plurality of identical or substantially identical gripping modules such that each of the plurality of gripping modules may be interchangeable with respect to each other. A first of the plurality of substantially identical gripping modules may be mountable to the traveling block. A second of the plurality of substantially identical gripping modules may be mounted such that the traveling block is translationally moveable with respect thereto for cooperation with the first of the plurality of substantially identical gripping modules in holding and lowering the wellbore tubulars. In one embodiment, an elevator/top mount module is provided that may be used either with the elevators or as a top mount module. Thus, the elevator/top mount module may be connectable to either the rig floor or to the traveling block. The elevator/top mount module may receive either the first or the second of the plurality of substantially identical gripping modules 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial elevating view of a drilling rig showing an elevator supported by links from a traveling block and a spider slip assembly supported by the rig floor; 
     FIG. 2A is a split elevational view, partially in section, of an elevator module supporting an interchangeable gripping module; 
     FIG. 2B is a top view, partially in section, of the elevator and interchangeable gripping module of FIG. 2A; 
     FIG. 3 is a split elevational view, in section, of a flush mounted interchangeable gripping module; 
     FIG. 4 is a split elevational view, in section, of a top mounted interchangeable gripping module; and 
     FIG. 5 is an elevational view, of a shroud used for guiding the pipe within the interchangeable gripping module of the present invention. 
    
    
     While the present invention will be described in connection with presently preferred embodiments, it will be understood that it is not intended to limit the invention to those embodiments. On the contrary, it is intended to cover all alternatives, modifications, and equivalents included within the spirit of the invention. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring first to FIG. 1 for general background, there is shown the pertinent portion of a drilling rig  10  which is rigged to run well casing with a prior art elevator slip assembly  12  suspended from links  28  and a traveling block  26  (indicated in dashed lines), having a bottom casing guide  16 . Spider assembly  18  is mounted to rig floor  24  and may or may not have a bottom guide  20  and atop spider guide  22 . Casing joint  34  is being assembled as part of a casing string. Casing joint  34  forms a type of wellbore tubular string which may typically be permanently cemented in place within an open hole wellbore. Casing joint  34  may typically have a collar  36  atone end thereof. 
     Also shown in FIG. 1, the elevator and spider may be of the type that is air actuated, or partially air actuated, from an air supply  42  which passes through a conduit or hose  38  to elevator  12  and through a conduit or hose  40  to the spider  18 . Interconnected between the elevator  12  and the spider  18  are typically a plurality of conduits or hoses such as hoses or conduits  44  and  46 . 
     In FIG.  2 A and FIG. 2B, slip-type elevator assembly  50  in accord with the present invention is disclosed. Slip-type elevator assembly  50  includes elevator module  52  and an interchangeable gripping module  54 . In the handling system of the present invention, a plurality of interchangeable gripping modules  54  are used as discussed subsequently. Gripping module  54  is received into bore  56  of elevator module body  59 . Bore  56  is preferably conveniently cylindrical for receiving a cylindrical mating portion of gripping module  54  below shoulder  60 . The outer surface of elevator module body  59  may also preferably be cylindrical for lower manufacturing costs. Load supporting shoulder  60  of gripping module  54  engages load support surface  58  of elevator module  52  for supporting the heavy load of the casing string which may weigh hundreds of thousands of pounds. In a preferred embodiment, shoulder  60  is effectively formed by an increased diameter of gripping module  54  extending upwardly of load supporting shoulder  58  when gripping module  54  is positioned within elevator module  52  as illustrated in FIG.  2 A. Other means besides load supporting shoulder  60  for supporting the weight may be provided such as bars, rings, flanges, and the like which could also be received by mating surfaces on elevator module  52 . 
     Elevator module  52  may or may not include baseplate  62  which may be made integral to elevator module body  59 . Casing guide  64  may be provided at the bottom of elevator module  52  with a sloped guide surface  66  for guiding the casing into gripping module bore  68 . Elevator module has lifting ears  70  for connecting to links  28  that attach to traveling block  26 . Bolts or other fasteners such as bolt  72  may be used for securing elevator module  52  with respect to gripping module  54 . 
     Gripping module  54  includes a bowl section  74  with rings or sloping inner surfaces  76  that are used for supporting and urging camming slips  78  into and out of gripping arrangement with the casing, such as casing joint  34 . Bowl section  74  may preferably be longitudinally split or in sections that are constrained or held together in operation by any one of elevator module  52 , the rotary table bore, or top mount body  144  as discussed subsequently. In a presently preferred embodiment, bowl section  74  includes at least three internal load rings  80 ,  82 , and  84  which form multiple camming surfaces. Using relatively long slips  78 , very roughly between about one and two feet long, and supported by internal load rings  80 ,  82 , and  84 , the handling system of the present invention can handle full rated loads, up to for instance 500 tons, even without crushing thin wall tubulars. In a presently preferred embodiment, lower load ring  84  includes a separate support ring  86  that provides N additional strength by supporting slip  78  at end  88  as shown in the right half of the split view of FIG.  2 A. The left side of FIG. 2A shows slips  78  in a non-gripping or retracted position while the right side of FIG. 2A shows slips  78  in the gripping or extended position. 
     Slips  78  include a slip shoe  90  which may be mounted by bolts  92  to a sliding support  94  which operates by cams or sloping surfaces of the load rings to move between the retracted (tubular released) and radially inwardly extended (tubular gripped) position as it slides longitudinally generally parallel to axis  96  of gripping module  54 . In the split view of FIG. 2A, movement of sliding support  94  would be between the upward disengaged position (left split view), and the downward engaged position (right split view), respectively. An additional support ring  98  may be provided at the bottom of bowl section  74  to provide additional strength and support. 
     Gripping module  54  includes a slip operating mechanism which may be hydraulically or pneumatically controlled and is supported within upper housing section  100 . A plurality of cylinders  102  are provided for operating mandrels  104 . Mandrels  104  interconnect with control arms  106  which are pivotally connected to slips  78 . Thus, upward and downward linear motion produced by cylinders  102  is used by camming surfaces, such as camming surfaces  105  on slips  78  and camming surfaces  107  on bowl section  74  to produce radially outwardly and radially inwardly movement of slips  78  for releasing and gripping wellbore tubulars such as casing joint  34 . Preferably, camming surfaces  105  and  107  have a substantially sawtooth profile due to their being several rows to permit spreading the camming pressures over numerous camming surfaces. Thus, each gripping module  54  includes a bowl section  74 , slips  78 , and a slip operating mechanism. 
     FIG. 3 shows an interchangeable gripping module  54  as may be provided in flush mount spider assembly  110  for use with a rotary table disposed on the rig floor. Gripping module  54  may replace the master bushing in the rotary table on the rig floor. For different types of rotary tables, adapters may be used. Depending on the type of rotary table, a flush mount gripping module  54  may be substantially inserted within the rotary table but upper portions thereof such as upper housing  100  and parts of bowl section  74  may or may not extend above the rig floor. As with slip-type elevator  50 , significant weight must be supported by flush mount assembly  110 . In flush mount assembly  110  using National rotary table  114 , shoulder  60  of gripping module  54  engages upper surface  122  of National rotary table  114  adjacent bore  124  that extends through the rotary table to the wellbore. One or more bolts or other fasteners, such as bolt  126 , may be used to further secure gripping module  54  to the rotary table. For use with other rotary tables such as Continental rotary table  112 , an adapter  128  may preferably be provided. In this configuration, weight from shoulder  60  is transferred to the adapter shoulder  130  which then applies the weight to the rotary table and/or rig floor. 
     The split view of FIG. 3 also shows slips  78  in a retracted or released position as at  116  and an extended or gripping position as at  118 . It will be noted that the gripping module  54  of FIG. 3 for use as spider assembly  110  is identical or substantially identical to gripping module  54  of FIG. 2 so that gripping modules  54  are conveniently and economically interchangeable with respect to each other. 
     FIG. 4 shows one possible top mount spider arrangement  140  using the same or another gripping module  54 . Top mount spider arrangement  140  is designed to set on top of the rotary table when the rotary is of a size and/or construction other than those for which gripping module  54  is designed for or may otherwise be adapted to for flush mount purposes. Base member  142  may be secured to the rotary table and/or rig floor. Top mount body  144  preferably defines bore  146 , which as also shown in the above embodiments, receives a preferably cylindrical portion of gripping module  54 . One or more bolts or other fasteners, such as bolt  149 , may be used to secure gripping module  54  within top mount body  144 . Bore  68  extends through gripping module  54  and leads to the wellbore through bore  148  in base member  142  and the hole in the rotary table. Top mount spider arrangement  140  supports the significant weight of the casing string which may be held by slips  78 . Base  142  supports lower ring  98  at surface  152 . Support surface  154  supports shoulder  60  of gripping module  54 . Support arms  150 , which may be of various construction, may be used for positioning, mounting, and/or convenient lifting as desired of top mount spider arrangement  140 . In one embodiment, top mount body  144  could also be used either with the elevators or as a top mount for added redundancy when a top mount spider construction is used. 
     FIG. 5 shows shroud  160  used in guiding the casing string through gripping module  54 . Shroud  160  and the top  162  and bottom  164  of windows  166  are shown most clearly in FIG. 5 although the respective top  162  and bottom  164  are also indicated in FIG. 2A, FIG. 3, and FIG.  4 . Slips  78  extend through windows  166  in the engaged position for gripping the casing as discussed above. In the disengaged or open position, slips  78  are flush or slightly recessed with respect to shroud  160 . 
     The interchangeability of gripping modules  54  with each other for use as either an elevator slips or a spider is one of the significant advantages of the present invention. In operation, when the tool handling system of the present invention is sent on a job, three gripping modules  54  will be provided with one elevator module, such as elevator module  52  discussed above. If required, an additional one top mount module is also provided. Since only two gripping modules  54  will actually be used at any one time, the third gripping module  54  will provide 100% redundancy for the spider and the elevator without the need for a fourth tool. This reduces the equipment required by approximately 25% to provide a significant economy for both the vendor and the customer. Moreover, the construction disclosed herein with three internal load rings and long heavy-duty slips allows the handling system of the present invention to handle large loads even with thin wall tubulars without crushing them. 
     The present invention is effectively a three-in-one handling tool system. The modular tool system can be used as a: 1) flush mount spider; 2) a top mount spider; and/or 3) a slip-type elevator. To briefly summarize, the tool system consist of a split bow module, such as gripping module  54 , that includes the slips and the slip operating mechanism. An elevator module, such as elevator module  52 , is provided. A top mount module, such as top mount body  144 , may also be provided as necessary for providing a top mount spider construction. The gripping or split bowl module  54  will fit into the rotary table or elevator module  52  or top mount body  144 . Thus, each split bowl or gripping module  52  can be utilized for three separate functions. Elevator module  52  mimics the rotary table bore so as to contain the split bowl or gripping module  54  and has integral lifting ears  70  to enable it to function as an elevator. Top mount body  144  is designed to set on top of the rotary table when the rotary is of a size other than the one the gripping module  54  was preferably designed for. Top mount body  144  also mimics the function of the rotary table in constraining the bowl or gripping module  54  and may or may not be made with an integral baseplate, such as baseplate  142 . 
     The foregoing disclosure and description of the invention is illustrative and explanatory thereof, and it will be appreciated by those skilled in the art, that various changes in the size, shape and materials, the use of mechanical equivalents, as well as in the details of the illustrated construction or combinations of features of the various three-in-one elements may be made without departing from the spirit of the invention.

Summary:
A wellbore tubular handling system and method is provided for operation in holding and lowering tubulars, such as casing strings, at a rig site. The handling system utilizes a plurality of interchangeable gripping modules for use with both the elevator slips and the spider. Because the gripping modules are completely interchangeable, only one additional gripping module is needed to provide redundancy at the well site to thereby reduce the equipment normally required. An elevator module receives the interchangeable gripping module therein. An interchangeable gripping module may also preferably be flush mounted in many standard rotary table types. Alternatively a top mount spider module is provided to receive a gripping module for other rig floor and/or rotary table constructions. The gripping module has three inner support rings and slips between approximately one and two feet in length to permit load support while protecting any thin walled casing that is used in the casing string.