(19)

(11)

EP 2 386 012 A2

(12)

(88) Date of publication A3: 28.10.2010 (43) Date of publication: 16.11.2011 Bulletin 2011/46 (21) Application number: 10729430.8 (22) Date of filing: 06.01.2010

(51) International Patent Classification (IPC):  E21B 43/16(2006.01) E21B 43/243(2006.01) E21B 43/24(2006.01) (86) International application number: PCT/US2010/020182 (87) International publication number: WO 2010/080780 (15.07.2010 Gazette 2010/28)

(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 MK MT NL NO PL PT RO SE SI SK SM TR (30) Priority: 07.01.2009 US 143052 P (71) Applicants: M-I LLC Houston, TX 77072 (US) M-I Drilling Fluids UK Limited Aberdeen AB10 1UD (GB) M-I Drilling Fluids Canada, Inc. Calgary, Alberta T2P 2W2 (CA)	(72) Inventors: WILLIAMS, Steve CH-1295 Mies (CH) ALDUS, David Calgary, AB T2P 2W2 (CA) FOUT, Gary, E. Cypress, TX 77429-4593 (US) (74) Representative: Giovannini, Francesca et al Osha Liang 32, avenue de l'Opéra 75002 Paris 75002 Paris (FR)