HYDROCARBON-BASED EMULSION DRILLING MUD Russian patent published in 2003 - IPC

FIELD: oil and gas production. SUBSTANCE: objective of invention is physicochemical action on formation during primary exposure of productive oil pools. Drilling mud contains, wt %: liquid petroleum product 25-60, surface-active emulsifier 1.0-2.5, hydrophobized dispersed chalk 3-10, mineralized water phase (base component), and additionally co-emulsifier, in particular chemically modified silica with 40-70% degree of substitution of surface silanol groups by alkyl-aryl radicals, 0.6- 1.5. Above-indicated alkyl-aryl radicals are, in particular, methyl, ethyl, propyl, or phenyl. Chalk is hydrophobized by mechanically mixing it with 0.5-1.0% of chemically modified silica having 99.8-99.9% hydrophobicity and particle size 0.005 to 0.1 mcm. EFFECT: decreased water loss, prevented clogging of pore space of borehole environment during primary exposure of productive formation. 4 cl, 3 tbl, 14 ex