IMPROVEMENT OF PRODUCED WATER QUALITY TREATMENT BY CHEMICAL METHOD

The final period of oil field development is characterized by a gradual reduction in oil production and intensive growth of the produced water volume, with the water cut of the well products reaching 95 % and more. This is due to the fact that waterflooding is a common enhanced oil recovery method. Yet, serious requirements are imposed on the injected water quality. Significant content of residual oil and mechanical impurities in water causes deterioration of injection efficiency, production losses, extra costs for bottom-hole zone maintenance and costs for maintenance of main process equipment. To date, quite a lot of technologies for produced water cleaning from oil products have been developed; however, not much of these yield required quality indicators. Therewith, reequipment of oil treatment facilities with the introduction of new treatment equipment involves significant capital and time expenditures. This paper considers a chemical method of produced water cleaning from residual oil allowing the water treatment quality improvement and oil loss reduction as exemplified by oil treatment facilities of one of the Rosneft Group producing companies. The method involves the use of «deoilers» – chemical reagents designed to clean produced water from oil residues and mechanical impurities. The results of research of deoiler effect on water treatment quality showed that application of all tested chemicals reduces the residual oil content in treated water. Thus, under the existing treatment parameters (temperature and settling time) and the facility process mode, the required water quality indicators as per OST 39-225-88 are achieved. However, feeding the captured oil to the pipeline upstream the oil settling tanks causes increased residual water content in the treated oil. To minimize the risk of disrupted conditions of facility, the optimum ratio of captured oil when using deoilers for water treatment to the incoming fluid was determined with captured oil making maximum 0.5 % of the total incoming volume.