WEIGHTED DRILLING FLUID Russian patent published in 2019 - IPC C09K8/20 

FIELD: oil and gas industry.

SUBSTANCE: invention relates to oil and gas industry, in particular to water-based drilling fluids used in drilling in complex geological conditions, for example, drilling of exploratory and production wells in conditions of abnormally high pressures AHPR. Weighted drilling fluid contains, wt%: structure-forming agent – clay 3–6; reagent high molecular weight sodium-carboxymethyl cellulose stabilizer KMC-1100 0.3–0.8; potassium chloride KCl 3–7; potassium hydroxide KOH 0.2–0.3; lignosulphonate reagent – condensed sulphite-spirit syrup CSSS-2M 2–2.5; ferrochrome lignosulphonate FCLS-M 1–2.5; antifoaming agent Santi F 0.2–0.3; lubricating additive DSB-4TTP 1.5–2.0; barite weighting agent KB-3 30–50; water-soluble salt filler – sodium or potassium formate 12–15; ferriferous filler – haematite or iron-ore concentrate of FOC 10–25; water – balance.

EFFECT: improving drilling efficiency under conditions AHPR, improved quality of drilling mud of high density by reducing filtration, improving rheological and sedimentation properties.

1 cl, 2 tbl, 4 ex