METHOD OF PREPARING REAGENT FOR TREATMENT OF DRILLING MUDS

oil and gas production. SUBSTANCE: in a method of preparing compositionally and qualitatively stable lignosulfonate reagents for efficiently controlling properties of drilling muds by polycondensation of lignosulfonates with formaldehyde and condensation agent in aqueous medium with acid catalyst on heating followed by neutralization of reaction mixture with alkali metal hydroxides and subsequent drying, polycondensation is carried out stepwise. First, lignosulfonates interact with formaldehyde to raise viscosity to 130-140 s and then cocondensation agent is added and post-polycondensation proceeds to achieve viscosity 160-180 s, weight ratio of lignosulfonates to formaldehyde being 1:(0.09-0.15) and formaldehyde-to-cocondensation agent molar ratio (0.6-1.0):(0.002-0.01). Cocondensation agent is selected from group including: phenol, phenolsulfonic acid, 2-naphthol, 2- naphtholsulfonic acid, dihydroxydiphenyl sulfate, dihydroxydiphenylmethane, sulfomethylated dihydroxydiphenylmethane, and urea. As 2-naphtholsulfonic acid, product prepared by sulfonation of 2-naphthol with sulfuric acid in production of synthetic tanners can be used, and, as lignosulfonates, modified metal-containing lignosulfonates, containing chromium and/or iron, in particular up to 3.2% chromium, up to 7% iron, and up to 7% aluminum, chromium+aluminum up to 7.5%, molar ratio Fe/Cr being (0.8-1.0):(0.25-0.3) and Al/Cr (0.8-1.0):(0.13- 0.15). EFFECT: improved working characteristics. 12 cl, 3 tbl, 3 ex