(19)

(11)

EP 0 204 823 A1

(12)

(43) Date of publication: 17.12.1986 Bulletin 1986/51 (21) Application number: 86900445.0 (22) Date of filing: 04.12.1985

(51) International Patent Classification (IPC):  E21B 23/ 03( . ) E21B 43/ 12( . ) (86) International application number: PCT/US1985/002411 (87) International publication number: WO 1986/003544 (19.06.1986 Gazette 1986/13)

(84) Designated Contracting States: DE FR GB IT NL (30) Priority: 07.12.1984 US 19840679263 18.10.1985 US 19850789313 (60) Divisional application: 89114538.5 / 0345830 (60) Divisional application: 89114541.9 / 0351884 (71) Applicants: CRAWFORD, Douglass W. Atwood Akers Crowley, LA 70526 (US) CRAWFORD, William B. Atwood Akers Crowley, LA 60526 (US) DINNING, Robert W. Houston, TX 77055 (US)	(72) Inventors: CRAWFORD, Douglass W. Atwood Akers Crowley, LA 70526 (US) CRAWFORD, William B. Atwood Akers Crowley, LA 60526 (US) DINNING, Robert W. Houston, TX 77055 (US) (74) Representative: Baillie, Iain Cameron  c/o Ladas & Parry Altheimer Eck 2 D-80331 München D-80331 München (DE)