IMPROVED COMPOSITIONS OF FOAM DRILLING FLUID ON OILY BASE, METHOD FOR THEIR OBTAINING AND APPLICATION Russian patent published in 2011 - IPC E21B21/14 C09K8/38 

FIELD: mining.

SUBSTANCE: well drilling method involves addition of effective amount of foam-forming composition to hydrocarbon base liquid in order to create foam hydrocarbon drilling fluid - FHDF, where foam-forming composition includes foam-forming agent and stabilising quantity of polymer, which is enough for formation of foam that is stable at temperature of at least 350°F; pumping of FHDF to drilling string during drilling; pumping of organophilic gas to the well or near distal end of drilling string or in/or near drilling bit at the speed which is enough for obtaining the drilling fluid having the required reduced weight of fluid column, and foam removal from the well. Well drilling method involves circulation of hydrocarbon drilling fluid system including hydrocarbon fluid and effective amount of foam-forming composition added to oil or gas well, where foam-forming composition consists of foam-forming agent and stabilising polymer which is sufficient for formation of foam stable at temperature of 350°F; addition of organophilic gas to the liquid at the speed which is enough for formation of the foam drilling fluid having the required reduced weight of fluid column, in which there increased is entrainment flow rate of fluid, increased amount of drilling slurry and other drilling by-products from the well and removal of foamed drilling fluid from the well.

EFFECT: increasing viscosity of base oil at low shift speeds and reduced speed of gravitational drainage through plateau border between foam cells.

26 cl, 2 ex, 3 tbl, 1 dwg