(19)

(11)

EP 0 870 101 A1

(12)

(43) Date of publication: 14.10.1998 Bulletin 1998/42 (21) Application number: 96944608.0 (22) Date of filing: 17.12.1996

(51) International Patent Classification (IPC):  E21B 36/ 02( . ) (86) International application number: PCT/EP1996/005754 (87) International publication number: WO 1997/024510 (10.07.1997 Gazette 1997/30)

(84) Designated Contracting States: AT BE CH DE DK ES FI FR GB GR IE IT LI LU NL PT SE (30) Priority: 27.12.1995 US 19950009344P (71) Applicant: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V. 2596 HR Den Haag (NL)	(72) Inventors: KARANIKAS, John, Michael Houston, TX 77027 (US) MIKUS, Thomas Houston, TX 77077 (US) VINEGAR, Harold, J. Houston, TX 77096 (US) WELLINGTON, Scott, Lee Houston, TX 77077 (US)