(19)

(11)

EP 0 665 980 A1

(12)

(43) Date of publication: 09.08.1995 Bulletin 1995/32 (21) Application number: 93924075.0 (22) Date of filing: 25.10.1993

(51) International Patent Classification (IPC):  G21B 1/ 00( . ) G21B 3/ 00( . ) (86) International application number: PCT/EP1993/003004 (87) International publication number: WO 1994/010688 (11.05.1994 Gazette 1994/11)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB GR IT LI LU NL PT SE (30) Priority: 26.10.1992 EP 19920402909 (71) Applicant: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V. NL-2596 HR Den Haag (NL)