WATER-BASED DRILLING FLUID FOR BORING OR TREATING HOLE PASSING THROUGH POROUS AND PERMEABLE FORMATION Russian patent published in 2006 - IPC C09K8/04 E21B43/22 

FIELD: drilling engineering.

SUBSTANCE: invention relates to well-boring or, in general, to performing operations requiring circulation of fluid in bored hole, said fluid being in contact with porous and permeable walls of catcher rock. Water-based drilling fluid containing common ingredients such as filtrate reducer, viscosity raising agent, weighting agent, and emulsion other than "oil in water" further contains less than 1 g/L of one or several compounds selected from group of partial esters of polyatomic alcohols with fatty acids C₈-C₁₀, wherein chain length is selected such that partial ester would possess sufficient dispersity in water, compatibility with other ingredients, would not form emulsion with stratal oil, and would be sufficiently adsorbed on porous stratal rock.

EFFECT: reduced and prevented damage to catcher rock.

10 cl, 2 dwg, 10 tbl, 8 ex