Research On Stripping For Decarbonization Of Carbon Dioxide Flooding Produced Water

For studying the treatment technology of CO2flooding produced water, andreducing the corrosion of oilfield equipment, the nitrogen gas stripping process wasresearched in this paper. The factors affecting CO2removal efficiency were analyzed,and the parameters were also optimized. Also studied the impact of the CO2oncoagulation process, and the mechanism was analyzed. Finally, through the simulationexperiments, we determined the order of process unit, and a cost analysis was alsocarried out.In nitrogen gas stripping experiments, we first studied the CO2solubility in thewater under different temperature and viscosity. The static experiments was carried outin different nitrogen ventilation, temperature, viscosity and oil content to research theregular of CO2removal, and the first order kinetics fitting was done. The study foundthat improving ventilation could speed up the nitrogen removal rate and reduceprocessing time; To control the water temperature at30℃, CO2removal effect wasbetter than that of20℃or40℃; A amount of HPAM could significantly influence onCO2removal rate, and the lower viscosity of the water help to quickly remove CO2from water; The difference of CO2removal under different oil content is not obvious,but the existence of oil could extend the CO2stripping time.The key factors were analyzed on the above phenomenon, and through thecomparison of different experiments, including pure water test, salt water test, oilywater test, found that the factors affecting the CO2removal efficiency was HCO3-andHPAM, oil also hindered the CO2removal. After adjusted the raw water pH to5, weobtained a good result of CO2removal. Finally we studied the adding of differentdiameter of polyhedral hollow ball packing to strengthen CO2removal effect. Theresults showed that it has certain effect on CO2removal by small ones. By studying onthe CO2stripping parameters, we came to a conclusion：the ventilation of3L/min, thewater temperature of30℃, adjusting the pH to5, adding the polyhedral hollow balldiameter of25mm.By coagulation test, we explored the effects of the CO2on coagulation effect. Wefirst conducted an orthogonal experiment to obtain the best coagulation parameters ofproduced water without CO2. Then, we carried out a coagulation experiment under thiscondition with CO2. We selected the Zeta potential and density and size of floc as evaluation standard. The results showed the best operation parameters: fast stir speed at300RPM lasting0.5min, slow stir speed at75RPM lasting10min, and the dose ofcoagulant at50mg/L. The oil removal rate was higher, and got more compact floc. Forthe coagulation test on oily water containing CO2, the oil removal efficiency and morecompact floc was obtained in neutral pH.Through the study of the optimization of continuous flow test, we selected testparameters for the gas water ratio of4.4:1, water temperature at30℃, raw water pHadjusted to5, adding of25mm polyhedral hollow ball packing. The content of CO2inthe effluent dropped below30mg/L, and pH was maintained at a neutral level.According to the pilot scale for the process, we made a technical and economicanalysis, and tons of water treatment cost was0.64yuan/ton.