DRILLING FLUID FOR WELL CONSTRUCTION IN DIFFICULT CONDITIONS, MAINLY FOR DRILLING EXTENDED-REACH WELLS AND HORIZONTAL WELLS Russian patent published in 2010 - IPC C09K8/28 

FIELD: chemistry.

SUBSTANCE: invention relates to drilling oil and gas wells and more specifically to drilling fluids used in difficult hydrogeological conditions, mainly for drilling extended-reach and horizontal wells, including tailing-in. The drilling fluid contains the following in wt %: drilling mud powder 1.0-4.0, stabiliser reagent - mixture of a product from modifying fatty acids with potassium alkali and nonionic surfactant containing not less than 1.5 mg-eq/l esters of organic acids in terms of dry residue, and from oxyethylated cellulose in mass ratio of 1:(1-2.0) respectively, 0.5-0.85, hydrocarbon water-repellent phase - mixture of dioxane alcohols with weight fraction of hydroxyl groups in the range of 15-36%, 2.0-5.0, potassium chloride 1-15, potassium silicate 0.5-2.0 and water - the rest. The invention is developed in subclaims.

EFFECT: optimisation of structure rheological and filtration properties of the drilling fluid with low content of the clay phase due to reduction of the pseudoplasticity index and rate of dynamic filtration, with simultaneous improvement of lubricant, anti-sticking and inhibiting properties of the drilling fluid and its resistance to effect of contaminants.

5 cl, 3 tbl, 1 ex