Study On Treatment Of Sludge Floccutated By Flocculants Of Oilfield Wastewater

With the measure of oil extraction and injection enhancing, oil recovery increased vastly, and produced liquid and produced oil water also increased vastly. These led to sludge which floccutated by flocculants of oilfield wastewater increased. When produced much sludge, the ability of treating wastewater in factory of wastewater treatment was restricted; and caused the encumbrance of environment. In order to choosing right treatment of treating sludge, the properties of sludge were studied in this paper. It could decrease the volume of sludge and the harm to environment.In this paper, different flocculants which were aluminum sulfate, polyaluminium chloride(PAC) and poly aluminum ferric chloride(PAFC) were used in treating wastewater which were producted from ASP flooding which were weak base ASP flooding and strong base ASP flooding. Physical property of these sludge were analysed and compared; They had the similar property: water cut were over 98%; high oil cut; density were lighter than water. And then filtration performance by gravity,nature settleability and dewaterrability were studied in this paper. The nature settleability and dewaterrability of PAC sludge were better than other sludge; filtration performance by gravity of PAFC sludge was better than any other sludge; these three properties of aluminum sulfate sludge were worst in these sludge.The measure which were chemical washing, chemical flocculation and washing-flocculation were used in this paper in order to treating weak base aluminum sulfate sludge.The best process condition of chemical washing was that temperature was 35℃; pH was 9; dosage of reagent Tsg was 0.4g/L; dosage of dombinational surfactant(Na₂CO₃:SP-169=3:1) was 5g/L; the shortest reaction time was 20min. And then sludge oil cut decreased by 53.7%, from 1410.5mg/L to 757.4mg/L. But sludge water cut didn't variation. Filtration performance by gravity,nature settleability and dewaterrability of sludge treated by chemical demulsification were studied under this condition, but the effect was not obviousness. The best process condition of chemical flocculation was that temperature was 40℃; pH was 7; the shortest reaction time was 20min; dosage of reagent Tsg was 10g/L; dosage of HPAM was 0.15g/L. And then sludge water cut decreased from 98.91% to 55.56%. But sludge oil cut didn't variation. Filtration performance by gravity, nature settleability and dewaterrability of sludge treated by chemical flocculation were studied under this condition, the effect was obvious improved.The best process condition of washing-flocculation was that temperature was 40℃; pH was 9; dosage of dombinational demulsifier(Na₂CO₃:SP-169=3:1) was 4.5g/L; after it reacted 15min, 9g/L reagent Tsg was dosed and 0.125g/L HPAM was dosed, and then reacted 17.5min. Water cut of weak base aluminum sulfate sludge was decreased from 98.91% to 45.32%; Oil cut was decreased by 46.44%, from 1410.5mg/L to 655.0mg/L. Water cut and oil cut of sludge which were treated were decreased a lot. Density of sludge increased from 0.902～0.976g/cm³ to 1.104～1.147g/cm³, and separated from water was more easier. Filtration performance by gravity, nature settleability and dewaterrability of sludge treated by chemical flocculation were studied under this condition, the effect was obvious improved.