WELL DRILLING AND COMPLETION COMPOSITION Russian patent published in 2001 - IPC

FIELD: drilling fluids. SUBSTANCE: composition relates to drilling oil and gas wells, in particular to reagents for chemical treatment of drilling fluids serving for exposing production horizons and completing wells. Proposed composition, containing water and polypropylene glycol monoalkyl ethers of general formula , in which R is C1-C4-alkyl and m>80, additionally contains polyalkylene glycols depicted by general formula , in which X is oxygen , nitrogen, or methylene; Y nitrogen or methylene; c, a, and b vary from 0 to 2; t, q, g, v, k, and j from 0 to 250; g+m>o; d=1-5; R¹, R², R³ are hydrogen or methyl; A, B, and G vary from 1 to 120; 3<(a+b+c)<5; which are, more particularly, ethylene oxide/propylene oxide copolymers with ethylene oxide level no higher than 50 mol % and molecular weight 6000 to 40000 or ethylene oxide/propylene oxide copolymers with propylene oxide level at least 85 mol % and molecular weight 300 to 6000. Composition more specifically contains, wt %: polypropylene glycol monoalkyl ether, 1-30; polyalkylene glycol with no higher than 50 mol % ethylene oxide, 0-45; polyalkylene glycol with at least 85 mol % propylene oxide, 30-90; water, the balance. Drilling composition may also contain 0.01 to 3 wt % phosphonic complexion. EFFECT: increased degree of inhibition of clay rocks, reduced filtration characteristics of drilling fluid and increased its aggregative stability in presence of mineral salts, and improved surfactant and lubricating properties over a wide temperature range. 2 cl, 4 tbl, 2 ex