Patent Publication Number: US-6983811-B2

Title: Reamer shoe

Description:
BACKGROUND OF THE INVENTION 
   (1) Field of the Invention 
   The present invention relates to a reamer shoe for use in drilled well bores as are typically utilised in oil and gas production. 
   (2) Description of Related Art 
   After boring a region of an oil or gas well it is normal to run tubing or “casing”, into the well bore to act as a lining. The casing is typically run into the well bore from the surface and the length of casing is often referred to as a “casing string”. The lining of the bore can then be strengthened by introducing cement between the external surface of the casing and the internal surface of the well bore. 
   It is common for the casing to meet obstructions as it is run through the well bore. These may be ledges which form in the well bore material during boring, formation washouts, or debris formed by unstable sections of the well bore wall collapsing. Such obstructions halt the progress of the casing procedure and increase the risk of the casing string jamming in the bore. To prevent or minimise the effect of these obstructions a reamer shoe is conventionally mounted on the lower end of the casing string. The reamer shoe typically has a plurality of reaming members around the circumference of the shoe body, which remove any irregularities or obstructions from the wall of the bore and thereby facilitate the subsequent passage of the casing string and aid cementing. 
   In conventional reamer shoes, the reaming members extend parallel to the length of the shoe. Whilst this arrangement allows the reaming members to come into contact with the entire circumference of the bore well on rotation of the shoe, complete circumferential coverage of the bore well is not achieved when the shoe is reciprocated. 
   An attempt has been made to mitigate this problem in International Patent Application PCT/GB99/00093 in the name Downhole Products plc. This Application discloses a reamer shoe with reaming members which extend longitudinally and helically around, as opposed to longitudinally and parallel to, the shoe body. More specifically the reaming members extend helically around the body of the shoe in an opposite direction to the intended direction of rotation. 
   While this arrangement of reaming members gives full 360° coverage during both reciprocating and rotation, the efficiency of said members is very much dependent on the speed and also the direction of rotation. It will be appreciated that the quality of reaming action will be compromised at relatively high rotational speeds. In addition, the reaming action of the shoe is designed to be most efficient when the reaming members extend in the opposite direction to rotation; therefore if the shoe was rotated in the same direction as the reaming members extend, either intentionally or accidentally, the risk of the reaming members “biting” into the wall and hence becoming stuck in the bore would be increased. It would therefore be a distinct advantage to provide a reamer shoe which is equally effective on rotation and reciprocation, and which provides an efficient reaming action regardless of the speed and direction of rotation. 
   It is an object of the present invention to provide a reamer shoe for reaming a bore in preparation for receiving casing, wherein said reaming shoe is equally effective on rotation or reciprocation. 
   It is a further object of the present invention to provide a reamer shoe for reaming a bore in preparation for receiving casing, wherein said reaming shoe is efficient at cleaning a bore when rotated, regardless of the speed or direction of rotation. 
   DETAILED DESCRIPTION OF THE INVENTION 
   It is a yet further object of the present invention to provide a reamer shoe for reaming a bore in preparation for receiving casing, which is effective on rotation or reciprocation, regardless of direction or speed, and which is capable of covering the full 360° circumference of the bore. 
   BRIEF SUMMARY OF THE INVENTION 
   According to the present invention there is provided a reamer shoe for mounting on a tubing string, the reamer shoe having a reaming area supporting a plurality of reaming members with each of the reaming members being afforded a simple geometric shape, wherein the plurality of reaming members have complete circumferential coverage of the shoe body but the individual reaming members are non-continuous and do not fully extend either longitudinally along or circumferentially around the reaming area on the shoe body. 
   Optionally the reaming members are diamond shaped. 
   Alternatively the reaming members are square or circular although any other simple geometrical shape may be employed. 
   Preferably the reaming members are shaped in such a manner that they are separated by void areas which permit the relative by pass of fluid over the reaming area, between the reaming members. 
   Preferably the reamer shoe has a plurality of flow by areas or flow ports to allow lubrication of the shoe. 
   Preferably the reaming members are made of a hard wearing and resistant material such as tungsten carbide or polycrystalline diamond, although any other suitable material may be used. 
   Preferably the reaming members are securely attached to the shoe body by a standard technique such as welding or mechanical locking although any other suitable fixing means could be used. 
   Preferably the reamer shoe has connection means for mounting the reamer shoe on a tubing string. 
   Most preferably said connection means are threaded end connections which can mate with corresponding connection means on the casing. 
   Preferably the reaming shoe has an internal diameter which is at least equal to, or greater than the internal diameter of the casing. 
   Preferably the reamer shoe comprises a stabiliser or centraliser. 
   Preferably the dimensions of the reamer shoe are not restricted and could be adapted to be suitable for use with any casing equipment. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An example embodiment of the invention will now be illustrated with reference to  FIG. 1  which illustrates a reamer shoe in accordance with the present invention. 
   

   Referring to  FIG. 1  a reamer shoe, generally depicted at  1 , is comprised of a cylindrical body  2  which can be mounted on the lower end of a casing string (not shown). Typically mounting is achieved using threaded end connections  3  and a respective fit thread protector  4  located at the rear of the body  2  which mate with the casing. 
   The reamer shoe  1  further comprises a reaming area  5  which supports a plurality of reaming members  6 . The reaming members  6  are constructed from a hard resistant material such as polycrystalline diamond compact or tungsten carbide, or a combination of the two materials. 
   The reaming members  6  do not fully extend either longitudinally along or circumferentially around the reaming area  5  on the shoe body  2  that is, they are non continuous, and are afforded a diamond shape in the present embodiment, although this is not restricted and any other geometrical shape such as circles or squares could be employed. 
   As the reaming members  6  are non-continuous, each individual member is separated from the surrounding reaming member by void space  7 . This void space  7  functions to allow the by-pass of fluid which is passed through the bore well (not shown) over the reaming area  5 . The body  2  also has an additional flow by area  8  and flow port  9  to allow fluid by pass to lubricate the surfaces of the reaming shoe  1 . The body  2  also comprises a stabiliser or centraliser  10  which functions to maintain the reaming shoe  1  in the centre of the well bore (not shown). 
   In use, the reamer shoe  1  is mounted on the casing string (not shown) relatively close to the first section of the string. Upon reaching an obstruction or irregularity in the bore wall the tool may be reciprocated or rotated as required, in order to remove or push aside the obstruction in preparation for receiving casing. The casing operation can then be continued. 
   The present invention is inherent with significant advantages in that the geometrical design of the reaming members increases the efficiency of the reaming process regardless of whether the shoe is rotated or reciprocated. The tendency to “bite” into the wall of the bore and become stuck, which is often seen with conventional reaming blades which extend around the body of the shoe, is minimised. 
   A further advantage is that, unlike the reaming members known to the art, which conventionally extend parallel to or helically around the reamer shoe, the reaming members of the present invention are geometric and non continuous, and therefore have no direction as such. On rotation, the reaming members of the present invention are therefore effective regardless of whether the shoe is rotated in a clockwise or anti-clockwise direction. 
   Further modifications and improvements may be incorporated without departing from the scope of the invention herein intended.