HYDROCARBON-BASED DRILLING FLUID Russian patent published in 1997 - IPC

FIELD: oil and gas production; drilling fluids. SUBSTANCE: invention focuses on drilling fluid used when advancing through unstable clays, mudstones, salts as well as through zones with abnormally high formation pressures containing carbon oxides and hydrogen sulfide. Increased barite-capacity (density) of solution, decreased viscosity and strength of structure and reduced filtration loss are caused by that hydrocarbon-based drilling fluid contains diesel fuel or kerosene fraction, or petroleum, and also caustic lime, water, high-oxidation bitumen, sulfonol, an oil-containing sulfonate additive, and barite modified by sodium tripolyphosphate. Owing to sulfonate additive, barite-capacity of solution increases from 39.18 to 50 vol.% and thence density increases from 2200 to 2520 kg/cu.m, Engler viscosity decreased by a factor of 1.5 (52 and 35 s), static shear stress by a factor of 25 (303 and 12 dPa), and filtration loss is 5.2 times reduced. EFFECT: improved performance characteristics of fluid. 4 tbl