(19)

(11)

EP 0 174 328 A1

(12)

(43) Date of publication: 19.03.1986 Bulletin 1986/12 (21) Application number: 85901042.0 (22) Date of filing: 01.03.1985

(51) International Patent Classification (IPC):  E21B 47/ 12( . ) G01D 1/ 16( . ) G01V 3/ 28( . ) G01B 7/ 287( . ) G01D 3/ 06( . ) (86) International application number: PCT/GB1985/000085 (87) International publication number: WO 1985/004005 (12.09.1985 Gazette 1985/20)

(84) Designated Contracting States: AT BE CH DE FR GB LI LU NL SE (30) Priority: 02.03.1984 GB 19840005532 (71) Applicant: HANSON RESEARCH LIMITED Clanfield Oxon OX8 2RX (GB)	(72) Inventor: ATHERTON, Eric, John Oxon, OX8 2RX (GB)