Abstract:
An elevator for assembling a plurality of a large diameter pipe joints into a pipe string with a drilling rig is disclosed. The first one of a number of large diameter pipe joints is adapted to threadingly engage another large diameter pipe joint. The elevator is detachably securable to the upper end of the first joint, and is adapted to both lift and position the first joint while it is stabbed and tightened onto the string. The elevator is further adapted to co-operatively engage the rotary table of the drilling rig to rotatably tighten the second joint to the first joint as the second joint is added to the string.

Description:
BACKGROUND OF INVENTION 
   Flush joint (or “near flush joint”) pipe used for riser pipe in offshore drilling and/or used for conductor pipe for deep well drilling is often too large in diameter to be handled by conventional die-grip casing handling tools. The most commonly available die-grip tools for handling large pipe have a maximum diameter capacity of approximately 24 in. Riser pipe and conductor pipe can have a substantially larger diameter, frequently in excess of 36 in. 
   The present invention relates to special equipment and procedures for handling and running large diameter flush-joint pipe in offshore wells and/or other drilling sites requiring pipe having diameters exceeding the capacity of conventional running tools. 
   SUMMARY OF INVENTION 
   In one embodiment, an elevator for assembling a plurality of a large diameter pipe joints into a pipe string with a drilling rig is disclosed. A first one of the plurality of large diameter pipe joints is adapted to threadingly engage a second one of the plurality of large diameter pipe joints. The elevator is detachably securable to an upper end of the first joint and adapted to both lift and position the first joint while it is stabbed and tightened onto the string. After stabbing and tightening, the elevator is lowered with the joint where it is further adapted to co-operatively engage the rotary table of the drilling rig to rotatably tighten the second joint to the first joint as the second joint is added to the string. 
   Also disclosed is an elevator clamped to the joint with a bolt on collar, or it may be bolted around an annular groove formed in an external surface of the pipe joint. The collar may have a plurality of Keystone-shaped recesses that extend over corresponding keystone shaped projections attached to the external surface of a pipe joint. In addition the groove in the joint may frictionally engage a complimentary, annular, centrally extending projection developed along an inner circumferential surface of the collar. Also disclosed is the groove in the joint with a reverse angle shoulder adapted to engage and rest upon a similarly angled projection in the collar. 
   As the collar supports a weight of the string from the rotary table, a surface of the projection in the collar may be slightly spaced axially from a groove surface in the joint whereby the surface of the projection engaging the groove surface supports a substantial amount of the vertical load imparted to the collar by the weight of the string. 
   In addition, the elevator may have a plurality of lifting pad eyes for attachment to lift lines on the drilling rig, and rotary table lugs may extend from the lifting pad eyes to engage the rotary table. 
   Also disclosed is an elevator having two halves, each half comprising a plurality of bolt ears adapted to receive bolts for clamping the collar. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIGS. 1–3  are general views of bolt on elevators (collars) of the present invention. 
       FIG. 4  illustrates cylindrical rotary table of  FIGS. 1–3 . 
       FIG. 5  illustrates a rotary support table having openings of the type used in the present invention. 
       FIGS. 6–12  are views of various arrangements of bolt on elevators (collars) of the present invention. 
       FIGS. 13–16  are views of an alternate embodiment of bolt on elevators (collars) of the present invention. 
       FIGS. 17–20  are views of alternate keystone plates for the collars of  FIGS. 13–16 . 
       FIG. 21  is an enlarged view of the welding of the plates of  FIGS. 17–20 . 
       FIGS. 22–25  are views of a permanent lug plate of an alternate embodiment of the present invention. 
       FIG. 26  is a cross section illustrating a connecting fixture secured to a lug plate in accordance with the present invention. 
       FIGS. 27–37  represent various steps in the transfer of a pipe joint of the present invention from storage to a position ready for use. 
   

   DETAILED DESCRIPTION 
   A large diameter pipe joint  11  is moved from a storage location on a drilling rig to a vertical orientation in the drilling rig derrick to be run through the drilling rig floor RF,  12  into the sea or into the well bore below the rig. The lower end of the pipe joint  11  terminates as a threaded pin and the upper end terminates as a connector  11   a  in the form of an internally threaded box. Multiple pipe joints, such as the joint  11 , are assembled to form a continuous flush joint pipe string of pipe that extends from the rig and through the sea to the sea bottom or into a well bore below the rig. 
   In assembling the pipe string, a pipe elevator (collar)  13  is attached to the upper end area  14  of an individual joint of the pipe to assist in bringing the pipe to the vertical running position. In one form of the Invention, the elevator  13  provides one of the attachment fixtures for the lines  16  and  17  used to lift and/or move the pipe to the vertical orientation. Additional positioning and restraint lines, such as the snub line  18  are attached to a fixture  20  that is removably secured to an attachment plate  21  bonded to the pipe. Once the joint  11  is in its vertical position, the elevator  13  supports the joint  11  vertically so that it may be added to a string of the pipe  22  extending through the rotary table  24  on the drilling rig floor  12 . 
   One embodiment of the elevator  13  is a bolt-on collar with an internal annular projection. ( FIGS. 4 ,  6 – 12 ). The collar is bolted around an annular groove machined into the external surface of an internally threaded connector  11   a  at the top of the joint  11 . The connector  11   a  may be welded onto the tubular body of the joint  11  to provide an internally threaded box connection at the upper end of the joint or it may be otherwise secured to, or formed at, the end of the tubular body. The groove is machined or otherwise suitably formed in the outer surface of the connector  11   a . Machining is preferred to provide uniform surface contact between the elevator projection and the connector groove. 
   A second embodiment of the elevator is a bolt-on collar having axially extending Keystone-shaped recesses that extend over corresponding Keystone shaped projections welded to the external surface of the internally threaded connector. ( FIGS. 13–16 ). The terms “collar” and “elevators” are used interchangeably in the description of the present invention. 
   An elevator  25  is connected to the top of the assembled pipe string  22  extending below the rotary table. The elevator  25  rests on the rotary table  24  to support the string  22 . The elevator  25  is identical to the elevator  13  that supports the joint of pipe  11  being added to the string. 
   The new joint  11  being added to the string is threaded into the string  22  by rotating the suspended string  22  with the rotary table  24  while holding the new joint stationary with a snub line  18  secured to the removable handling fixture  20 . The rotary  24  is rotated in a counter-clockwise direction to cause the right hand threads of the joint  11  and the string  22  to engage. The opposite end of the snub line  18  is secured to a stationary point (not illustrated) on the rig. 
   Once the joint  11  is properly engaged to the string  22 , the lift lines  17  extending between the uppermost collar  13  and the top drive or traveling block of the rig (not illustrated) are raised to lift the joint  11  and attached string  22 . Lifting the string  22  permits the lower collar  25  to be removed from the string. Once the collar is removed, the string  22 , including the newly added joint  11 , is then lowered until the upper collar  13  is resting on the rotary table  24  where it may support the entire string full. The process is repeated until the full string of pipe is run into the well. 
     FIG. 4  illustrates cylindrical rotary table lugs  26  and  27  that extend downwardly from lifting pad eyes  28  and  29 , respectively, of the elevator  13 . The cylindrical rotary table lugs  26  and  27  are received in openings  30  and  31  respectively formed in the top surface of the rotary table  24 . The engagement of the lugs  26  and  27  in the openings  30  and  31  transmits the rotary motion of the rotary table  24  to the collar  13 , which in turn transmits the rotation to the connector  11   a  at the top of the joint  11 . 
     FIG. 5  illustrates a conventional rotary support table  35  having openings  36 – 39  of the type used to receive the rotary table lugs extending from the elevator  13 . 
     FIGS. 6 and 7  illustrate, in perspective view, two halves  13   a  and  13   b  of the elevator  13 . Bolt holes  40 – 47  are provided in bolt ears extending radially from the two elevator halves for receiving bolts (not illustrated) used to securely clamp the elevator halves  13   a  and  13   b  about a pipe connection such as the connector  11   a . The rotary table lug  26  extends axially away from the elevator half  13   a  while the rotary table lug  27  extends axially from the collar half  13   b.    
     FIG. 8  illustrates the rotary lug  27  projecting from the bottom surface of the collar half  13   b.    
   As illustrated by joint reference to  FIGS. 4 ,  9  and  11 , when the pipe connector  11   a  of the joint  11  is engaged by the collar  13 , the pipe joint  11  is supported by an annular, centrally extending projection  50  developed along the inner circumferential surface of the clamp  13   a  and  13   b  of the collar  13 . The external circumferential bearing surface  51  of the projection  50  conforms to the internal circumferential bearing surface  52  formed within an annular recess  54  formed about the external surface of the connector  11   a . The cross-section of the connector  11   a  and the cross section of the projection  50  extending from the elevator  13  have conforming profiles. 
   With the collar securely bolted about the pipe connector  11   a , the elevator projection surface  51  engages the groove surface  52  to effect a large radially directed gripping force against the connector  11   a . The gripping force works with the surface friction between the two contacting surfaces to prevent relative rotation between the elevator and the connector during the process of adding joints to the string. 
   In a preferred embodiment of the Invention, illustrated in  FIGS. 9 and 10 , with the collar  13  securely clamped about the connector  11   a  and supporting the weight of the pipe string  22  from the rotary table, the projection surface  51  is slightly spaced axially from the groove surface  52   a . The result is that the projection surface  51   b  engaging the groove surface  52   b  supports a substantial amount of the vertical load imparted to the collar by the weight of the string  22 . 
   A modified form of the invention is illustrated in  FIGS. 11 and 12 . A projection  60  extending from the elevator  13  is adapted to be received within an annular recess  62  formed in the external surface of the connector  11   a . The projection  60  and recess  62  are similar to the projection and recess of  FIGS. 9 and 10  with the exception of the change in dimensions and cross sectional profile of the components. 
   The dimension A of the projection  60  is less than the dimension B at the entry to the groove  62  so that the elevator  13  can be closed circumferentially about the connector  11   a  with the projection  60  received within the groove  62 . The recess  62  has a surface  64  formed as a reverse angle shoulder adapted to engage and rest on a similarly angled surface  65  on the annular projection  60 . 
   When the elevator  13  is gripped around the connector  11   a , circumferential surfaces  68  on the connector  11   a  and  69  on the elevator  13  are brought together with a strong radially directed bearing force exerted by the bolts holding the elevator halves together. The resulting bearing pressure and surface friction between the surfaces  68  and  69  prevent the elevator  13  from rotating relative to the connector  11   a  when the connector and its associated pipe joint  11  are being added to the pipe string  22 . 
   The inclined angles of the contact surfaces  64  and  65  cooperate with the weight of the string  22  to pull the elevator  13  radially inwardly to enhance the circumferential gripping force exerted by the elevator against the pipe connector  11   a . The inclined surfaces  64  and  65  also cooperate to hold the collar circumferentially about the pipe section  11   a  in the event of failure of the bolts or other parts of the elevator. 
   A feature of the form of the Invention Illustrated in  FIGS. 11 and 12  is that the string weight pulls the elevator  13  into compression rather than forcing it into tension. Breakage or loss of the bolts holding the elevator halves together or partial breakage of parts of the elevator will not necessarily release the pipe from its support at the rotary table because of the trapping action provided through the mating inclined surfaces between the elevator projection and the connection groove. 
   The form of the invention illustrated in  FIGS. 9–12  is a preferred design in that it requires no radial protrusions on the external surface of the pipe joints and is inexpensive to fabricate and employ. The system of  FIGS. 9–12  also permits the pipe to be handled without requiring an increase in the outside diameter of the flush joint pipe. 
   The elevator  13  described in  FIGS. 9–12  is inexpensive to fabricate and one such elevator may be attached to each joint of pipe before the pipe is delivered to the location where it is to be run into the well. This procedure allows the elevator to be secured to each pipe joint in a controlled environment, ensuring that the bolts are propery torqued up and that the collar is properly secured to the connector  11   a . Placing the elevator on the pipe before it is delivered to the well location reduces the amount of time required to maneuver the pipe from its on-site storage location and run the pipe into the well. Personnel safety is also enhanced in that the collar application may be performed in the controlled environment of an indoor shop rather than the extreme, outside environment of an offshore drilling rig. 
     FIG. 13  illustrates an elevator, indicated generally at  70 , similar to the elevator  13  previously described but intended to be used with pipe joints having permanent external radial protrusions adapted to be received within accommodating recesses in the elevator  70 . The elevator  70  is designed for reuse at the well site. When an elevator  70  is removed from its support of the string  22 , it is used to secure and remove a new joint from the storage rack and add the new joint into the string. 
   The elevator  70  is similar to the elevator  13  except that the central internal circumferential projection of the elevator  13  is replaced by Keystone shaped recesses  72  and  74  adapted to engage similarly shaped Keystone plates or projections  76  and  78  permanently secured to the external surface of the pipe section  11   a .  FIGS. 15 and 16  illustrate elevator halves  70   a  and  70   b  in position about a pipe connector  11   a  to which Keystone projections  76  and  78  have been permanently welded. 
     FIG. 17  is an elevation illustrating a Keystone plate that is welded to the external surface of the connector  11   a .  FIG. 18  is a top view of the Keystone plate, illustrating its arcuate shape, taken along the line  18 — 18  of  FIG. 17 .  FIG. 19  is a side elevation of the Keystone plate taken along the line  19 — 19  of  FIG. 17 . 
   Four internally threaded bolt holes  81 – 84  are provided on the broad part of the Keystone plate  76 . The bolt holes are used to secure handling fixtures that secure lines used in positioning and making up the pipe joints. The fixtures are removed before the joint is lowered into the well. Three weldment areas  86 ,  87  and  88  are provided for providing welding contact lines for welding the Keystone plate  76  to the external surface of the connector  11   a  or the pipe joint  11 . The lower end of the plate  76  is tapered as indicated at  90  to reduce the probability of hanging up the pipe joint to which it is secured as the pipe joint is lowered into the well. 
     FIG. 21  illustrates welding W extending around the contact lines provided by the weldment areas. The welding W along the internal weldment areas secures the Keystone plate  76  to the pipe connector  11   a  without requiring placement of welding material along the external surfaces  92  and  94  of the Keystone. The external surfaces  92  and  94  are thus allowed to mate exactly with the engaging surfaces of the Keystone recesses in the elevator  70 . 
   The provision of Keystone shapes for the elevator recesses  72  and  74  and the permanently secured pipe connector projections  76  and  78  facilitates placement of the elevator about the pipe section  11   a  and also equalizes the distribution of support forces exerted on the elevator when the elevator is holding the entire string weight. 
     FIGS. 22–25  illustrate a permanent lug plate  21  to be welded to a pipe joint  11  to assist in handling and making up the pipe joint.  FIG. 22  is a front elevation of the lug plate  21 .  FIG. 23  is a top view taken along the line at  23 — 23  of  FIG. 22  illustrating the curvature of the lug plate.  FIG. 24  is a side view taken along the line  24 — 24  of  FIG. 22  illustrating the bottom taper  101  of the lug plate.  FIG. 25  is a front elevation of the lug plate  21  welded onto a pipe joint  11 . 
   The lug plate  21  is provided with four internally threaded bolt holes  102 – 105 . A weldment area  106  cut into the lug plate  21  provides an increased welding contact line for welding the lug plate to the pipe joint  11 . Welding W along the external lug edge and along the edges of the weldment area  106  is illustrated in  FIG. 25  securing the lug plate  21  to a pipe joint  11 . 
     FIG. 26  is a cross sectional view illustrating a connecting fixture  20  secured to the lug plate  21  welded to the pipe  11 . Two of four bolts  110  and  112  are illustrated seated in the bolt holes  104  and  105 , respectively. The connecting fixture  20  is provided with a circumferentially extending arm  20   a  and a pad eye plate  20   b  with a pad eye opening  20   c . The arm  20   a  assists in distributing reaction forces exerted through the restraining line  18  as the joint  11  being added to the string  22 . The pad eye  20   c  provides an attachment point for the restraining and/or control line  18  used in the positioning and/or makeup of the connection. 
     FIGS. 27 through 37  illustrate various steps in the transfer of a joint  11  from its storage location to a vertical orientation in preparation for being added to a string of pipe to be run into the well.  FIG. 27  illustrates positioning lines  16  and  18  secured respectively to a connecting fixture  120  secured to a Keystone projection  76  and the connecting fixture  20 . The connecting fixture  120  is similar to the connecting fixture  20  and is bolted into place in the bolt holes  81 – 84  of the Keystone plate. The lines  16  and  18  are illustrated lifting the joint  11  from its horizontal storage location in preparation to moving the pipe to the drilling rig floor. 
     FIG. 28  illustrates the elevator  70  being positioned about the pipe  11 . The elevator  70  is suspended from lines  122  and  123  respectively connected to one of the two elevator halves  70   a  and  70   b . The lines  122  and  123  hold the elevator  70  in the open position illustrated in  FIG. 29 . A stop in the hinge  70   c  prevents the elevator from opening further to facilitate placement of the elevator about the pipe  11 . 
     FIGS. 30 and 31  illustrate the elevator  70  loosely bolted around the pipe joint  11  prior to being moved axially into engagement with the Keystone projections  76  and  78 .  FIGS. 32–34  illustrate the elevator  70  being rotated around the pipe joint  11  by releasing the line  122  and raising the line  123  to align the Keystone projections on the pipe with the Keystone recesses in the elevator. 
     FIG. 35  illustrates the lift lines  17  being secured to the lift eyes  28  and  29  extending radially from the sides of the elevator  70 . Once the lift lines  17  are properly attached to the lift eyes  28  and  29 , the fixture  120  may be released from the Keystone projection  76  by removing the four bolts (not illustrated) holding the fixture to the Keystone projection. Once the joint  11  has been added to the string, the fixture  20  may be removed from the attachment pad  21 . The provision of removable handling fixtures  120  and  20  on the Keystone plate and on the pipe body, respectively, provides safe and secure attachment points for moving and making up the connection and also permits the rapid removal of the fixtures to reduce the outside dimensions of the pipe joint for facilitating its introduction into the well. 
     FIGS. 36 and 37  illustrate the pipe joint  11  being moved to its vertical position with the use of the lift lines  17  and the snub line  18 . 
   Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention.