(19)

(11)

EP 2 235 318 A1

(12)

(43) Date of publication: 06.10.2010 Bulletin 2010/40 (21) Application number: 08866416.4 (22) Date of filing: 25.11.2008

(51) International Patent Classification (IPC):  E21B 21/08(2006.01) E21B 21/00(2006.01) E21B 44/00(2006.01) (86) International application number: PCT/US2008/084630 (87) International publication number: WO 2009/085496 (09.07.2009 Gazette 2009/28)

(84) Designated Contracting States: AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MT NL NO PL PT RO SE SI SK TR Designated Extension States: AL BA MK RS (30) Priority: 19.12.2007 US 4175 14.11.2008 US 271000 (71) Applicant: BP Corporation North America Inc. Warrenville, IL 60555 (US)	(72) Inventor: ALBERTY, Mark, W. Houston TX 77082 (US) (74) Representative: Hamer, Christopher K. et al Mathys & Squire LLP 120 Holborn London EC1N 2SQ London EC1N 2SQ (GB)