Study Of The Wastewater Treatment Technology Of The Qi-Li-Cun Oil Field Wastewater

The oily wastewater from the combination station in Qi-Li-Cun oil production plant of Yanchang oilfield contains large amount of suspension of solid particles, sulfide, oil and harmful microorganisms, and without the pretreatment before injection processing, these substances will cause the reinjection system occurring serious corrosion and scaling problems, as well as the underground reservoir damage problem.The reservoir structure of the local area belongs to the ultra low permeability reservoir. To ensure the regular and persistent reinjection production, the requirements of the injection water quality is very high in the procedure of reinjection production. Therefore, in this thesis, by evaluation and optimized the injection treatment chemicals (including flocculant, slow agent, scale inhibitor, bactericide, etc.), we screen out the suitable water treatment agent and its dosage, and then analyze the feasibility of injection water after treatment through the core damage evaluation test.Based on the evaluation of joint station of oily wastewater treatment process and medicament screening, we determine the dosing sequence and dosage as follows. First, the pH of oily wastewater is adjusted to pH 7.0-7.5 with NaOH solution; then under continuous stirring conditions, the 50～60mg/L dosage H2O2 with concentration of 30% was added for desulphurization of iron removal treatment; the 100～110mg/L and 1.0～2.0mg/L flocculants PAC and coagulant aid PAM (relative molecular weight for 12 million) are added sequentially into oil field wastewater in the settlement tank, respectively. The optimum dosage of the corrosion inhibitor, antiseptic and scale inhibitor were 70mg/L,70～80mg/L and 50mg/L, respectively.The determination of oily wastewater treatment processes is as follows. First, the oily wastewater treated by the steps of flocculation and sedimentation, and through natural oil removal step oil and suspended oil and suspended solids in the oily wastewater of are removed; after adjusting water tank and water treatment machine, through the walnut shell+ change of fiber and multi medium secondary filtering device filter, the suspended solid particles in wastewater is removed further. After further deoxidization, sterilization, and filth treatment, treated water is transported by purification tank to water injection system.Core evaluation experiments show that through the technology processes and dosing regimen which is determined in this study, treated waste water has good compatibility with underground water, and less negative impact on the underground reservoir. Field test also suggests that the optimization scheme of oily wastewater treatment process and determine the dosing regimen can make the treated wastewater quality meeting the requirements of the reinjection water quality.