(19)

(11)

EP 1 809 858 A1

(12)

(43) Date of publication: 25.07.2007 Bulletin 2007/30 (21) Application number: 05804239.1 (22) Date of filing: 04.11.2005

(51) International Patent Classification (IPC):  E21B 33/06(2006.01) (86) International application number: PCT/GB2005/004272 (87) International publication number: WO 2006/048669 (11.05.2006 Gazette 2006/19)

(84) Designated Contracting States: AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI SK TR (30) Priority: 04.11.2004 GB 0424401 25.06.2005 GB 0512995 (71) Applicants: Bamford, Anthony S. Montrose DD10 9JT (GB) Hydril Company L.P. Parkway East Houston, TX 77032 (US)	(72) Inventors: Bamford, Anthony S. Montrose DD10 9JT (GB) Hydril Company L.P. Parkway East Houston, TX 77032 (US) (74) Representative: McKechnie, Neil Henry et al Kennedys Patent Agency Limited 185 St Vincent Street Glasgow G2 5QD Glasgow G2 5QD (GB)