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(11)

EP 0 973 992 A1

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(43) Date of publication: 26.01.2000 Bulletin 2000/04 (21) Application number: 97922678.4 (22) Date of filing: 05.05.1997

(51) International Patent Classification (IPC)7: E21B 7/15, E21B 47/00, E21B 49/00 (86) International application number: PCT/US9707/613 (87) International publication number: WO 9837/301 (27.08.1998 Gazette 1998/34)

(84) Designated Contracting States: DE FR GB IT NL (30) Priority: 07.05.1996 US 646211 21.02.1997 US 804022 29.04.1997 US 845945 (71) Applicant: EXXON RESEARCH AND ENGINEERING COMPANY Florham Park,New Jersey 07932-0390 (US)	(72) Inventors: ROSENSWEIG, Ronald, E. Summit, NJ 07901 (US) HINTON, Stephen, M. Chester, NJ 07930 (US) (74) Representative: Fletcher Watts, Susan J. et al ESSO Engineering (Europe) Limited,Patents and Licences,Mailpoint 72,Esso House,Ermyn Way Leatherhead,Surrey KT22 8XE Leatherhead,Surrey KT22 8XE (GB)