(19)

(11)

EP 2 007 966 A2

(12)

(88) Date of publication A3: 21.02.2008 (43) Date of publication: 31.12.2008 Bulletin 2009/01 (21) Application number: 07759460.4 (22) Date of filing: 27.03.2007

(51) International Patent Classification (IPC):  E21B 17/18(2006.01) (86) International application number: PCT/US2007/065014 (87) International publication number: WO 2007/112387 (04.10.2007 Gazette 2007/40)

(84) Designated Contracting States: AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC MT NL PL PT RO SE SI SK TR Designated Extension States: AL BA HR MK RS (30) Priority: 27.03.2006 US 786456 P 26.03.2007 US 691445 (71) Applicant: Potter Drilling, Inc. Redwood City, CA 94063 (US)	(72) Inventors: POTTER, Jared Michael San Carlos, California 94070 (US) POTTER, Robert Marshall Rio Rancho, New Mexico 87124 (US) BASLER, James Robert Redwood City, California 94061 (US) WIDEMAN, Thomas Waller Milton, Massachusetts 02186 (US) (74) Representative: Manitz, Gerhart  Manitz, Finsterwald & Partner GbR Martin-Greif-Strasse 1 80336 München 80336 München (DE)