Abstract:
An apparatus for facilitating the connection of tubulars using a top drive, said apparatus comprising a motor ( 4, 4 ′) for rotating a tool ( 30 ) for drivingly engaging a tubular, and means ( 3 ) for connecting said motor ( 4, 4 ′) to said top drive, the apparatus being such that, in use, said motor ( 4, 4 ′) can rotate one tubular with respect to another to connect said tubular.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of U.S. patent application Ser. No. 09/762,606, filed May 21, 2001, now U.S. Pat. No. 6,705,405 which is the National Stage of International Application No. PCT/GB99/02708, filed Aug. 16, 1999, which claims benefit of Great Britain Patent Application No. GB9818360.1, filed Aug. 24, 1988. Each of the aforementioned related patent applications is herein incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   FIELD OF THE INVENTION 
   This invention relates to an apparatus for facilitating the connection of tubulars using a top drive and is more particularly, but not exclusively, intended for facilitating the connection of a section or stand of casing to a string of casing. 
   SUMMARY OF THE INVENTION 
   In the construction of oil or gas wells it is usually necessary to line the borehole with a string of tubulars known as a casing. Because of the length of the casing required, sections or stands of say two sections of casing are progressively added to the string as it is lowered into the well from a drilling platform. In particular, when it is desired to add a section or stand of casing the string is usually restrained from falling into the well by applying the slips of a spider located in the floor of the drilling platform. The new section or stand of casing is then moved from a rack to the well centre above the spider. The threaded pin of the section or stand of casing to be connected is then located over the threaded box of the casing in the well and the connection is made up by rotation there between. An elevator is then connected to the top of the new section or stand and the whole casing string lifted slightly to enable the slips of the spider to be released. The whole casing string is then lowered until the top of the section is adjacent the spider whereupon the slips of the spider are re-applied, the elevator disconnected and the process repeated. 
   It is common practice to use a power tong to torque the connection up to a predetermined torque in order to make the connection. The power tong is located on a platform, either on rails, or hung from a derrick on a chain. However, it has recently been proposed to use a top drive for making such connection. The normal use of such a top drive maybe the driving of a drill string. 
   A problem associated with using a top drive for rotating tubulars in order to obtain a connection between tubulars is that some top drives are not specifically designed for rotating tubulars are not able to rotate at the correct speed or have non standard rotors. 
   According to the present invention there is provided an apparatus for facilitating the connection of tubulars using a top drive, said apparatus comprising a motor for rotating a tool for drivingly engaging a tubular, and means for connecting said motor to said top drive, the apparatus being such that, in use, said motor can rotate one tubular with respect to another to connect said tubulars. 
   Other features of the invention are set out in claims  2  et seq. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention and in order to show how the same may be carried into effect reference will now be made, by way of example, to the accompanying drawings, in which: 
       FIG. 1  is a front perspective view of an apparatus in accordance with the present invention; and 
       FIG. 2  is a rear perspective view of the apparatus of  FIG. 1  in use. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1  there is shown an apparatus which is generally identified by reference numeral  1 . 
   The apparatus  1  comprises a connecting tubular  2 , a suspension unit  3  and a hydraulic motor  4  and  4 ′. The hydraulic motor  4 , 4 ′ has a stator  5  and a rotor  6  and is driven by a supply of pressurised hydraulic fluid (the fluid supply lines are not illustrated in the Figures). The suspension unit  3  suspends the hydraulic motor  4 , 4 ′ from the connecting tubular  2 . 
   The suspension unit  3  comprises a plate  7  which is fixed to the connecting tubular  2  by a collar  8 . The plate  7  has two projections  9  and  10  which have holes  11  and  12  for accommodating axles  13  and  14 , which arc rotationally disposed therein. The axles  13  and  14  are integral with a rigid body  15 . A slider  16  is arranged on runners  17  and (not shown) on the rigid body  15 . Arms  18  and  19  are connected at one end to the slider  16  via spherical bearings  20  and at the other end to each side of the stator  5  via spherical bearings  21  and  21 ′. The arms  18  and  19  are provided with lugs  22  and  22 ′ to which one end of a piston and cylinder  23 ,  24  is attached and are movable thereabout. The other end of each piston and cylinder  23 ,  24  is attached to lugs  25 ,  26  respectively and is movable thereabout. A mud pipe  27  is provided between the plate  7  and the stator  5  for carrying mud to the inside of a tubular therebelow. The mud pipe  27  comprises curved outer surfaces at both ends (not shown) which are located in corresponding recesses in cylindrical sections  28 ,  29 , thus allowing a ball and socket type movement between the plate  7  and the stator  5 . 
   Referring to  FIGS. 1 and 2 , the apparatus  1  is suspended from a top drive  110  via connecting shaft  2 . A tool  30  for engaging with a tubular is suspended from beneath the rotor  6  of the hydraulic motor  4 . Such a tool may be arranged to be inserted into the upper end of the tubular, with gripping elements of the tool being radially displaceable for engagement with the inner wall of the tubular so as to secure the tubular to the tool. 
   In use, a tubular (not shown) to be connected to a tubular string held in a spider (not shown) is located over the tool  30 . The tool  30  grips the tubular. The apparatus  1  and the tubular are lowered by moving the top drive so that the tubular is in close proximity with the tubular string held in the spider. However, due to amongst other things manufacturing tolerances in the tubulars, the tubular often does not align perfectly with the tubular held in the spider. The suspension unit  3  allows minor vertical and horizontal movements to be made by using alignment pistons  31  and  32  for horizontal movements, and piston and cylinders  23  and  24  for vertical movements. The alignment piston  31  acts between the rigid body  15  and the plate  7 . The alignment piston  32  acts between the slider  16  and the arm  19 . The alignment pistons  31  and  32  and pistons and cylinders  23 ,  25  are actuated by hydraulic or pneumatic means and controlled from a remote control device. 
   The piston and cylinders  23 ,  24  are hydraulically operable. It is envisaged however, that the piston and cylinders  23 ,  24  may be of the pneumatic compensating type, i.e. their internal pressure may be adjusted to compensate for the weight of the tubular so that movement of the tubular may be conducted with minimal force. This can conveniently be achieved by introducing pneumatic fluid into the piston and cylinder  23 ,  24  and adjusting the pressure therein. 
   Once the tubulars are aligned, the hydraulic motor  4  and  4 ′ rotate the tubular via  15  gearing in the stator  5  thereby making up the severed connection. During connection the compensating piston and cylinders  23 ,  24  expand to accommodate the movement of the upper tubular. The alignment pistons  31  and  32  can then be used to move the top of the tubular into alignment with the top drive. If necessary, final torquing can be conducted by the top drive at this stage, via rotation of the pipe  27 , and the main elevator can also be swung onto and connected to the tubular prior to releasing the slips in the spider and lowering the casing string. It will be appreciated that the suspension unit  3  effectively provides an adapter for connecting a top drive to the tubular engaging tool  30 .