Study On Advanced Purification Technology For Oil Recovery Wastewater From Polymer Flooding

Oil recovery wastewater from polymer flooding (ORWFP) is a kind of new produced water, which was produced with the application of polymer flooding technology in oilfield. It not only contains oil hydrocarbons, suspended solids and inorganic salts, et al, but also contains a large amount of high molecular weight polymer, usually is polyacrylamide (PAM) with molecular weight of 4×106⁵×106. It is refractory organic wastewater with high emulsification degree. At present, ORWFP treated by current treatment process can not meet the requirement of re-injection water standard in oilfield and cannot be reused. If discharged, it would pollute the environment. So how to effectively treat ORWFP has become a key problem in concerning oil field in China. On the basis of different end-results of ORWFP treated, different advanced treatment processes were studied; referring to the existed treating process.To meet the requirement of re-injecting of ORWFP treated, an advanced treatment process of modified fibrous ball filtration, O3/UV/H₂O₂ oxidation and ultrafiltration was studied. In the re-injection treatment process, oil and suspended solids in ORWFP were removed mainly by modified fibrous ball filtration unit. Experimental results indicated that modified fibrous ball filtration unit can be operated stably under higher filtering rates. Oil concentration in filtration effluent was not more than 7.27mg/L and removal efficiency of oil reached 77.56%. Fibrous filtration can noticeably reduce the suspended solids in ORWFP. Concentration of suspended solids in fibrous filtration effluent was no more than 6.81mg/L and its removal efficiency was 84.17%. Medium-diameter of particles in fibrous filtration effluent was 3.11μm, which was reduced 59.53% than that before fibrous filtration. PAM in ORWFP can not be elimination by fibrous filtration. Modified fibrous ball can be cleaned up by washing-back with mixture of air and water for 10 to 20 minutes and reused. The intensities of air and water flow in process of washing-back were 16.72L/m2.s and 5.22 L/m2.s, respectively. Although modified fibrous ball filtration gave better results in removal of oil and...