(19)

(11)

EP 0 527 858 A1

(12)

(43) Date of publication: 24.02.1993 Bulletin 1993/08 (21) Application number: 91909159.0 (22) Date of filing: 10.05.1991

(51) International Patent Classification (IPC):  E21B 33/ 035( . ) E21B 43/ 017( . ) E21B 33/ 037( . ) (86) International application number: PCT/GB1991/000747 (87) International publication number: WO 1991/018182 (28.11.1991 Gazette 1991/27)

(84) Designated Contracting States: DE DK GB NL (30) Priority: 11.05.1990 GB 19900010627 (71) Applicant: JP KENNY CALEDONIA LTD. Aberdeen AB1 4BG (GB)	(72) Inventor: BROWN, Philip, Gwyn The Rowans 25 Marchbank Road Aberdeen AB1 9DJ (GB) (74) Representative: Moore, Anthony John  Gee & Co. Chancery House Chancery Lane London WC2A 1QU London WC2A 1QU (GB)