(19)

(11)

EP 0 980 462 A1

(12)

(43) Date of publication: 23.02.2000 Bulletin 2000/08 (21) Application number: 98924261.5 (22) Date of filing: 27.04.1998

(51) International Patent Classification (IPC)7: E21B 43/10, E21B 43/08 (86) International application number: PCT/EP9802/577 (87) International publication number: WO 9849/423 (05.11.1998 Gazette 1998/44)

(84) Designated Contracting States: DE DK GB IT NL (30) Priority: 28.04.1997 EP 97201267 (71) Applicant: SHELL INTERNATIONALE RESEARCHMAATSCHAPPIJ B.V. 2596 HR Den Haag (NL)	(72) Inventor: DONNELLY, Martin NL-1031 CM Amsterdam (NL)