Based on the studies of produced waters composition at the fields of Timano-Pechora oil&gaz bearing province, the range of initial boron working concentrations has been determined (10-20 mg/l). Phase equilibrium for stages of boron extraction by Yarresin B and re-extraction by acid and alkali has been studied. Box-type extracting unit has been tested, which enables to reach acceptable rate of extraction within wide range of water and organic phase flows ratios. Optimum phase ratios, number of actual extraction and re-extraction stages have been determined.