Sewage purification method for oil production

Abstract

The invention relates to a purification and treatment technique field for polluted air. The oil extraction wastewater purification method of the invention is that: activated magnesia oxide 50 to 500mg / L is directly added to pretreated thick oil wastewater (oil content lower than 30mg / L, suspension lower than 1000mg / L); the mixture enters into an eddy reactor, after mixing and reaction for 1 to 15 minutes, inorganic aluminum salt and organic flocculating agent are added to water out and then enter into a sludge reactor; the sludge reactor generates return sludge by 1 to 6 times of the water in through top return pump or a lifting and stirring device, the return sludge fully mixes with water in for 10 to 60 minutes and comes into a clarification and precipitation device; after 30 to 90 minutes of clarification and precipitation, silicon dioxide and suspensions are removed, and the water out enters into the next stage treatment device, sludge is discharged from a sludge groove, thus reaching the target of silicon removing and water purification.

Description

technical field [0001] The invention relates to the technical field of purification and treatment of oilfield sewage after oil recovery in an oilfield. Background technique [0002] Oilfield production fluid contains a large amount of sewage (10-90%), which becomes oilfield production water after separation from crude oil. Produced water from heavy oil fields (ie, heavy oil sewage) is generally reused in steam injection boilers after advanced treatment. After advanced treatment, the silica content is required to be below 50mg / L. At present, the process of silica treatment for heavy oil sewage is usually to first adjust the pH value of the pretreated sewage (oil content less than 16m / / L, suspended solids less than 30mg / L) to 10.2-10.5, and then add magnesium oxide or magnesium chloride , after sedimentation and clarification in clarification tanks or sedimentation tanks, silica in sewage is removed. Calcium oxide or sodium hydroxide is generally used to adjust pH. This de...

AI Technical Summary

Problems solved by technology

This desiliconization technology mainly has the following disadvantages: (1) the sewage after treatment is in an unstable state, and it is very easy to scale. Once the control is not good, the subsequent treatment device will not be able to operate; It is necessary to invest a large amount of pH regulator, silicon remover (dosing amount is 15 times that of removing silicon dioxide), coagulant (total amount is 1000-2000mg / L), and on the other hand, a large amount of sludge is produced after precipitation (dosage amount (3) this: the process treatment chemical cost is higher, generally 30% of the operating cost; (4) ) This process has strict requirements on the pretreatment of heavy oil sewage

Based on the above reasons, the current silicon removal system for heavy oil sewage is difficult to operate, which seriously restricts the development of advanced treatment and reuse technology for heavy oil sewage, and affects the further improvement of oilfield production and economic benefits.