METHOD OF PREPARING POLYMER-CLAY DRILLING FLUID Russian patent published in 2004 - IPC

FIELD: oil and gas production.

SUBSTANCE: invention relates to drilling fluids used for boring vertical, inclined, and horizontal boreholes. Fluid is prepared by mechanically by stirring clay, Na₂CO₃, salt-resistant polymer (Dk-Drill or PraeStol-2540) and process water, for which purpose, first polymer solution is prepared and then clay is added. Fluid additionally contains carboxymethylcellulose (0.25-0.35%) and aluminum sulfate as stabilizing and structurization agent. Polymer solution is prepared by successively adding Na₂CO₃, carboxymethylcellulose, and polymer to water, while aluminum sulfate and clay are added in the form of suspension with density 1100-1120 kg/m³, which is weighted with chalk to desired density 1160-1350 kg/m³ and additionally treated with Na₂CO₃ and carboxymethylcellulose. Volume ratio of polymer solution to volume of suspension ranges from 1:0.75 to 1:5. Thus prepared frilling fluid contains, wt %: Na₂CO₃ 0.3-0.5, carboxymethylcellulose 0.25-0.35, salt-resistant polymer 0.05-0.15, Al₂(SO₄)₂ 0.012-0.015, water - the balance.

EFFECT: increased lifetime, improved technical and economical characteristics as well as quality of exposing productive formations.