(19)

(11)

EP 1 581 720 A1

(12)

(43) Date of publication: 05.10.2005 Bulletin 2005/40 (21) Application number: 03778206.7 (22) Date of filing: 08.12.2003

(51) International Patent Classification (IPC)7: E21B 33/126 (86) International application number: PCT/CA2003/001890 (87) International publication number: WO 2004/053289 (24.06.2004 Gazette 2004/26)

(84) Designated Contracting States: AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LI LU MC NL PT RO SE SI SK TR Designated Extension States: AL LT LV MK (30) Priority: 06.12.2002 US 431227 P 09.10.2003 CA 2444648 (71) Applicant: Tesco Corporation Calgary, Alberta T2H 2B7 (CA)	(72) Inventor: SLACK, Maurice, William Edmonton, Alberta T6J 5C1 (CA) (74) Representative: Williams, Ceili et al Stevens Hewlett & Perkins Halton House 20/23 Holborn London EC1N 2JD London EC1N 2JD (GB)