Study On Produced Water Quality Adjustment Technology With Less Sludge By Sodium Hydroxide

Water quality modification technology is used to treat oilfield produced water,which has good treatment effect and can control corrosion.but,the alkalinity regulator used in water quality modification technology is composed of sodium hydroxide and calcium hydroxide mixed system,and there are some problems:the large dosage of compound alkali,the large amount of scale buildup and sludge in sewage plant and the high cost of water treatment and so on.especially sludge production,which needs to be solved urgently.Therefore,it is of great significance to study the new water quality modified formula with low sludge quantity.In this paper,the pan er sewage plant in Shengli Oilfield was used as the experimental object to study the relationship of sludge production and scale buildup with compound alkali in the process of water quality modification,finally,got the new water quality modification formula,through field application test,reached the purposes of reducing the sludge production,fouling,and reducing water treatment costs.Research showed that the amount of sludge and scale is related to the compound alkali formula.in the paper,by changing the ratio of sodium hydroxide and calcium hydroxide in the compound alkali,and compared the modified effect,with the content of calcium hydroxide in the compound alkali decreasing,the The sludge quantity tends to decrease,when there is no calcium hydroxide in the compound alkali,the amount of sludge is the least,and the amount of scale tends to decrease with the decrease of the content.The main reason is that the calcium hydroxide is soluble in water,and has a coagulant capacity,so most of calcium hydroxide will precipitate as sludge,and calcium hydroxide can bring more Ca²⁺to the water,which can increase scale.Finally,sodium hydroxide was used as the alkalinity regulator in the purposes of reducing the sludge production.The sewage in pan er sewage plant was used as the experimental object with sodium hydroxide as the alkalinity regulator in water quality modification,setting different dosing concentration of sodium hydroxide and comparing the sludge quantity、the water’s pH,the ion content of scaling and the water quality after treatment,finally,the water quality modified formula with less sludge for Pan er sewage plant:30%NaOH 600 mg·L^-1+Coagulant（SLP-30D）13 mg·L^-1.Through field application test,adjusted the formula in the laboratory properly to determine the final water quality modified formula with less sludge which is suitable for Pan er sewage plant:30%NaOH 800 mg·L^-1+Coagulant（SLP-30D）13 mg·L^-1,the pH of output water can reach 7.5-7.85,the average corrosion rate is 0.065 mm·a^-1,and the other water injection control indexes all reach the water injection requirement（SY/T5329-2012）.Compared with the old formula,the amount of sludge was reduced by67.2%,the scaling problem in the station was reduced,the scaling was reduced by about76.9%,the cost of the water treatment chemicals was decreased by 7.1%,overall,the costs of water treatment was saved by about 1.23 million yuan per year compared with the old formula.