(19)

(11)

EP 0 910 724 A1

(12)

(43) Date of publication: 28.04.1999 Bulletin 1999/17 (21) Application number: 97932768.0 (22) Date of filing: 02.07.1997

(51) International Patent Classification (IPC):  E21B 43/ 38( . ) (86) International application number: PCT/EP1997/003445 (87) International publication number: WO 1998/002637 (22.01.1998 Gazette 1998/03)

(84) Designated Contracting States: AT BE CH DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE (30) Priority: 12.07.1996 GB 19960014675 (71) Applicant: Baker Hughes Limited London WC2H 9EH (GB)	(72) Inventor: SKILBECK, Frank Newent, Gloucester GL18 1TW (GB) (74) Representative: Finck, Dieter, Dr.Ing., et al  v. Füner Ebbinghaus Finck Hano Mariahilfplatz 2 - 3 81541 München 81541 München (DE)