(19)

(11)

EP 0 037 821 A1

(12)

(43) Date of publication: 21.10.1981 Bulletin 1981/42 (21) Application number: 80901950.0 (22) Date of filing: 17.10.1980

(51) International Patent Classification (IPC):  E21B 44/ 00( . ) E21B 47/ 022( . ) G01H 1/ 00( . ) E21B 7/ 04( . ) E21B 47/ 12( . ) (86) International application number: PCT/GB1980/000170 (87) International publication number: WO 1981/001168 (30.04.1981 Gazette 1981/11)

(84) Designated Contracting States: CH DE FR LI SE (30) Priority: 17.10.1979 GB 19790035980 (71) Applicant: STRUCTURAL DYNAMICS LIMITED Southampton, S01 2ET (GB)	(72) Inventors: MILES, Anthony Peter Southampton S04 5JG (GB) JAMES, John David Southampton S01 7BQ (GB) (74) Representative: Lupton, Frederick  THORN EMI Patents Limited, Central Research Laboratories, Dawley Road Hayes, Middlesex UB3 1HH Hayes, Middlesex UB3 1HH (GB)