Research On Effluent Treatment Technology Of Weiyuan Shale Gas Fracturing Effluent

Fracturing operation is one of the main ways to increase oil and gas production at present.After fracturing operation,a large amount of flow-back fluid is returned to the ground.If it is discharged directly without treatment,it will bring great harm to the local environment and waste a lot of water resources.In this paper,after the analysis of the components of unconventional shale gas fracturing flow-back fluid in Weiyuan gas field,the processes of chemical coagulation,electric flocculation and chemical oxidation were explored according to the characteristic of water quality.The research shows that for the separate chemical flocculation of the wastewater,when the concentration of PAC is1300 mg/L and the dosage of CPAM is 20 mg/L,the COD of water sample treated by chemical flocculation process is 134 mg/L and the removal rate of COD is 92.8%.The optimal operating parameters of the electroflocculation reactor are:the electrification time is 30 min,the current density is 9 m A/cm~2,and the p H is 7.After treatment,the COD decreases from 1742 mg/L to 36 mg/L,the removal rate of COD is 99%,turbidity decreases from 834 NTU to 3 NTU,and the removal rate of turbidity nearly reaches100%.The separate oxidation experiment can not meet the on-site reutilization standard.According to the data obtained,the design of the process scheme is carried out.The designed two schemes,chemical flocculation&oxidation and electrical flocculation,can all meet the GB 8978-1996 first-level discharge standard.