(19)

(11)

EP 2 776 656 A1

(12)

(43) Date of publication: 17.09.2014 Bulletin 2014/38 (21) Application number: 12846993.9 (22) Date of filing: 06.11.2012

(51) International Patent Classification (IPC):  E21B 21/08(2006.01) E21B 21/12(2006.01) E21B 10/60(2006.01) (86) International application number: PCT/US2012/063716 (87) International publication number: WO 2013/070609 (16.05.2013 Gazette 2013/20)

(84) Designated Contracting States: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR (30) Priority: 08.11.2011 US 201161556986 P (71) Applicant: Chevron U.S.A. Inc. San Ramon, CA 94583 (US)	(72) Inventors: ARMISTEAD, George Taylor San Ramon, California 94583 (US) BERGERON, Henry Anthony San Ramon, California 94583 (US) (74) Representative: Nash, David Allan  Haseltine Lake LLP Redcliff Quay 120 Redcliff Street Bristol BS1 6HU Bristol BS1 6HU (GB)