(19)

(11)

EP 0 425 511 A1

(12)

(43) Date of publication: 08.05.1991 Bulletin 1991/19 (21) Application number: 89906382.0 (22) Date of filing: 18.05.1989

(51) International Patent Classification (IPC):  E21B 33/ 038( . ) F16L 37/ 00( . ) (86) International application number: PCT/GB1989/000544 (87) International publication number: WO 1990/014495 (29.11.1990 Gazette 1990/27)

(84) Designated Contracting States: FR (71) Applicants: MOBIL OIL CORPORATION New York New York 10017 (US) FSSL LIMITED Aberdeenshire AB4 9RF (GB)	(72) Inventors: HICKOK, Doyle, Dean London W9 1BN (GB) APPLEBY, David Aberdeen AB1 5JT (GB) MANK, James, Leon Buckinghamshire HP13 5PX (GB) (74) Representative: Jones, Alan John, et al  CARPMAELS & RANSFORD 43 Bloomsbury Square London, WC1A 2RA London, WC1A 2RA (GB)