Green Oxidation And Promotion For Treatment Of Waste Fracturing Fluid Produced By Oilfield

In oilfield operations,fracturing technology is one of the most important technologies of increasing oil production and is widely applied in various different reservoirs;hydraulic fracturing is a very complex process,with the extensive use of fracturing technology,the fracturing liquid is also thus used widely,so the problem of waste fracturing fluid produced in the fracturing process attracts more and more attention.Waste fracturing fluid is with the characteristics of stable structure,high COD value,and being difficult to be degraded by nature.Therefore,if waste fracturing fluid is not treated and discharged,it can cause irreversible damage to the environment.The thesis puts forward that regarding potassium ferrate as the core green strong oxidant,combining green processes like microwave and electro-chemical oxidation,to treat oilfield waste fracturing fluid,the treating process is consistent with the using principles that green chemistry aims to reduce and even fully eliminate raw materials,which are not conducive to human health and environment.The thesis researched the combined treatment technology of waste fracturing fluid pretreatment(microwave-calcium hypochlorite premodulation treatment,COD value is less than 1260mg/L),waste fracturing fluid oxidation treatment(potassium ferrate oxidation-coagulation,COD value is less than 350mg/L)and waste fracturing fluid advanced treatment(electrochemical deep oxidation-coagulation,the COD value is less than 150mg/L),the indicator of waste liquid COD,pH,viscosity and suspended solids reaches National Second Level Standard for Discharging Water(GB 8978-1996).For pretreatment technology: the best condition of microwave treatment is 700 w microwave power,2min reaction time and 2 pH,and 2500mg/L calcium hypochlorite dosage is most favorable at calcium hypochlorite modulation stage;For oxidation treatment of waste fracturing fluid: the optimum condition of potassium ferrate oxidation is 3500mg/L initial concentration,24 ℃,30 min reaction time,400r/min stirring intensity and PH=10 in initial solution.at coagulation stage,the best condition is 1300mg/L polymerization aluminum chloride dosage,50mg/L cationic polyacrylamide dosage,400r/min stirring speed,and PH=10;for waste fracturing fluid advanced treatment: it is better to reach 4V electronic voltage,60 min reaction time,10 initial pH,and 400r/min at electrochemical deep oxidation stage.By adopting combined treatment technology pretreatment-oxidation treatment-advanced oxidation process,COD removal rate under optimum condition can reach 34.2%,81.7% and93.9% respectively,COD value reduces from 1869mg/L to 112.6mg/L,viscosity drops down to 1.23 cp from 4.5cp,and suspended solids drop from 589mg/L to 19.7mg/L.