(19)

(11)

EP 0 717 809 A1

(12)

(43) Date of publication: 26.06.1996 Bulletin 1996/26 (21) Application number: 95911137.0 (22) Date of filing: 16.09.1994

(51) International Patent Classification (IPC):  E21B 43/ 017( . ) (86) International application number: PCT/GB1994/002028 (87) International publication number: WO 1995/008044 (23.03.1995 Gazette 1995/13)

(84) Designated Contracting States: BE DE DK ES FR GB GR IE IT MC NL PT SE (30) Priority: 17.09.1993 GB 19930019258 (71) Applicant: CONSAFE ENGINEERING (UK) LIMITED East Tullos Industrial Estate, Aberdeen AB1 4AX (GB)	(72) Inventor: ROBERTSON, John Gordon London Links, Fife KY8 6HH (GB) (74) Representative: Moreland, David, Dr., et al  Fitzpatricks, 4 West Regent Street Glasgow G2 1RS Glasgow G2 1RS (GB)