(19)

(11)

EP 0 852 654 A1

(12)

(43) Date of publication: 15.07.1998 Bulletin 1998/29 (21) Application number: 97933787.0 (22) Date of filing: 29.07.1997

(51) International Patent Classification (IPC):  E21B 23/ 00( . ) E21B 34/ 06( . ) E21B 29/ 00( . ) (86) International application number: PCT/GB1997/002043 (87) International publication number: WO 1998/004806 (05.02.1998 Gazette 1998/05)

(84) Designated Contracting States: DE DK FR GB IT NL (30) Priority: 29.07.1996 GB 19960015905 (71) Applicant: PETROLEUM ENGINEERING SERVICES LIMITED Dyce, Aberdeen AB2 OGP (GB)	(72) Inventor: RUBBO, Richard, Paul Aberdeen AB15 9NN (GB) (74) Representative: Pacitti, Pierpaolo A.M.E., et al  Murgitroyd and Company 373 Scotland Street Glasgow G5 8QA Glasgow G5 8QA (GB)