The Research On Organic Matter Degradation Technology Of Oilfield Fracturing Wastewater

Petroleum is one of the most widely used fossil energy, which is non-renewable.At present, oilfields only carried secondary and tertiary oil recovery Fracturingtechnology is the most important measures of oilfield stimulation, besides, thethickener of water-based fracturing fluid hydroxypropyl guargum is the most widelyapplied to oilfields. In general, the fracturing fluid is used for groundwater recharge,with the mined oil water content increased, the part of the fracturing fluid will efflux tothe ground. The characteristics of flowback fluid are deep color, strong acidity, highCOD_Crvalue and refractory. If it’s not treated direct discharge, Will cause seriouspollution to the surrounding environment.For the composition and characteristics of fracturing flowback fluid（referred asfracturing wastewater）, this subject based on the principle of micro-electrolysis, andFenton reagent oxidation, respectively, in this thesis we adopted above two methodsunder different reaction conditions observed COD_Crremoval rate variation, and usingorthogonal experiment to explore optimal reaction conditions; According to theprinciple of neutralization, coagulation, micro-electrolysis, Fenton reagent oxidation,then aimed at rising COD_Crremoval rate, we proposed a combined processes---"neutralization-Coagulation-Fe/C, micro-electrolysis-Fenton reagent method,"andoptimize the experimental conditions of each process.First, we did water quality detection by using the representative well fracturingwastewater of LongDong area (COD_Cr:5168mg/L). Second, conducted a deep researchon the Fenton system and Fe/C Micro electrolysis, through single factor experimentswe get the optimum reaction conditions is as follows:（1）single-Fenton system reagent fracturing wastewater, the optimum reaction conditions is pH value of3, H₂O₂amountof0.25mol/L Fe²⁺amount of40mmol/L, reaction temperature of50°C, the reactiontime was80min, COD_Crremoval rate is68.9%;（2）Fe/C micro-electrolysis experiment:the pH value was2, the reaction time was20min, the iron-carbon ratio was5:1, COD_Crremoval rate could reach52.7%. At last, using our “Ca（OH）₂neutralization,coagulation, Fe/C micro-electrolysis and Fenton reagent method” for fracturingwastewater treatment, and optimize each process unit. Through a large beakerexperiment we conclude that the optimal reaction conditions for each unit is asfollows:（1）neutralization test: Ca （OH）₂amount is3g;（2）coagulation experiments: pHvalue of8,100mg/L PAC;（3） Fe/C micro-electrolysis experiment: influent pH valuebetween1and2, with residence time of20min;（4） Fenton oxidation experiment: H₂O₂amount of0.25mol/L, reaction time is about2.0².5h. The removal rate of COD_Cris97.7%. Finally, on the basis of above work, our group sampled different well field ofeastern Gansu for our confirmatory experiment in laboratory. The experiment dividedthe oil-well into new and old, and treated the water samples with single process andour combination methods, the removal rate of COD_Cris all over75%.The main innovation of this thesis are: proposed a "neutralization-Coagulation-Fe/C micro-electrolysis-Fenton reagent method" to deal the high concentration organicfracturing wastewater, with better performance, provides an effective idea for thefracturing wastewater treatment.