(19)

(11)

EP 0 183 816 A1

(12)

(43) Date of publication: 11.06.1986 Bulletin 1986/24 (21) Application number: 85903023.0 (22) Date of filing: 13.06.1985

(51) International Patent Classification (IPC):  E21B 17/ 00( . ) E21B 47/ 12( . ) E21B 17/ 16( . ) (86) International application number: PCT/GB1985/000265 (87) International publication number: WO 1986/000112 (03.01.1986 Gazette 1986/01)

(84) Designated Contracting States: AT BE CH DE FR GB IT LI LU NL SE (30) Priority: 16.06.1984 GB 19840015409 23.11.1984 GB 19840029590 (71) Applicant: GENESIS (U.K.) LIMITED West Tullos Aberdeen AB1 4AW (GB)	(72) Inventor: NICHOLSON, Harlan, Leon Milltimber, Aberdeen AB1 0EH (GB)