CLAYLESS DRILLING MUD FOR CONTROLLED DIRECTIONAL AND HORIZONTAL HOLES AND FOR EXPOSING PRODUCTIVE FORMATIONS (VERSIONS) Russian patent published in 2002 - IPC

FIELD: oil and gas production and drilling fluids. SUBSTANCE: water-based drilling mud contains, wt. %: starch, 0.5-2.5; sodium hydroxide, 0.04-0.2; water-soluble boron compound, 0.4-1.5; and can additionally contain water-soluble silicic acid salt, 0.1-0.6; and carbonate weighing agent, 10-15. According to another embodiment of invention, drilling mud contains, wt. %: starch, 0.5-2.5; multianionic cellulose, 0.1-0.3; sodium hydroxide, 0.04-0.2; surfactant, 0.3-1.0; water-soluble boron compound, 0.4-1.5; and can additionally contain water-soluble silicic acid salt, 0.1-0.6; and carbonate weighing agent, 5-25. EFFECT: lowered consistence values and raised values of rigidity and encapsulation property with no loss in lubricating ability, heat and biological resistance, and reservoir properties. 6 cl, 2 tbl, 2 ex