(19)

(11)

EP 2 268 891 A2

(12)

(88) Date of publication A3: 05.11.2009 (43) Date of publication: 05.01.2011 Bulletin 2011/01 (21) Application number: 09720550.4 (22) Date of filing: 06.03.2009

(51) International Patent Classification (IPC):  E21B 37/00(2006.01) E21B 21/00(2006.01) (86) International application number: PCT/IB2009/005119 (87) International publication number: WO 2009/112948 (17.09.2009 Gazette 2009/38)

(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 MK MT NL NO PL PT RO SE SI SK TR Designated Extension States: AL BA RS (30) Priority: 12.03.2008 US 36018 (71) Applicant: M-I Drilling Fluids UK Limited Aberdeen AB10 1UD (GB)	(72) Inventors: BALLARD, David, Antony Aberdeenshire AB39 2PQ (GB) POPPLESTONE, Andy Aberdeen AB39 2DY (GB) (74) Representative: Giovannini, Francesca et al Osha Liang 32, avenue de l'Opéra 75002 Paris 75002 Paris (FR)