METHOD OF PREPARING METAL-CONTAINING LIGNOSULFONATE DRILLING REAGENT Russian patent published in 2001 - IPC

FIELD: drilling fluids. SUBSTANCE: lignosulfonate (100 wt parts) preliminarily acidified with sulfuric acid to pH 1.5-3.5 is mixed with half design amount of ferric sulfate (1.5-5.0 wt parts), which is dissolved at 35-40 C. Then design amount of sodium dichromate (4.0-9.0 wt parts) and the rest of ferric sulfate are consecutively added and entirely dissolved at stirring for 3-4 h at 60-95 C, after which sodium hydroxide is added to pH 4-5. EFFECT: increased effect of reagent on filtration and structural- mechanical (thinning) properties of drilling fluid and increased heat resistance thereof to 180 C at lower toxicity due to lesser amount of chromium(VI). 4 tbl