Research On Comprehensive Treatment Technology Of Shale Oil Gas Pressure Cracking And Liquid Discharge

With the development of global economy,all the countries need more and more oil,coal and natural gas.In order to ease the contradiction between supply and demand of natural gas in China,shale gas and other unconventional energy resources are gradually entering people’s field of vision.People often take various measures in the exploitation of shale oil and gas,such as drilling,fracturing,acid washing etc.The produced fracturing wastewater is the main pollution from oil and natural gas enterprises.Because there are large amounts of the chemicals in the fracturing wastewater,such as surface active agent,guar gum,clay stabilizer,dispersant ect,which have caused great harm to the ecological environment,the wastewater should be treated before reutilization or emission.According to the characteristics of fracturing wastewater,the suspended solids and colloidal in waste liquid were removed by coagulation sedimentation or electric flocculation and coagulation.Thus it can reduce the chroma and turbidity greatly.Then the chemical oxygen demand(COD)of wastewater was reduced by chemical oxidation treatment in order to achieve recycling standard of enterprise.The wastewater obtained may be further treated by ultrasonic ozone catalytic oxidation.The hydroxy radicals(.OH)produced in the process could oxidate the organic compounds in the wastewater so that the wastewater can meet the discharge standard.This paper systematically investigates the following factors on wastewater treatment efficiency:(1)the coagulations,optimal dosage,reaction time and the initial pH in the coagulation sedimentation;(2)the electrode plates,voltage,reaction time and the initial pH in the electric flocculation;(3)the oxidants,optimal dosage,reaction time and the initial pH in the chemical oxidation;(4)reaction time,the current of ozone generator and the flow of ozone in the ultrasonic ozone catalytic oxidation ect.The results show that the COD removal ratios of 6 kinds of coagulants all reached 80%.Sludge settlement ratio of coagulants was about 20-25%and the dosage was below 2500 mg/L in the coagulation experiment.The results showed the coagulants had favorable treatment effects.In the electric flocculation,the COD removal ratio reached above 85%by using the best electrode plate,which indicate the good effect.In the chemical oxidation,the wastewater treated by two methods above were oxidated with calcium hypochlorite(the dosage:0.2%).The COD removal ratio was about 50%with the COD 100 mg/L.The optimal conditions in the ultrasonic ozone catalytic oxidation are:initial pH 7～10,current of ozone generator 1 A,reaction time 30 min.According to the experimental conditions above,two programs of thetreatment of the wastewater have been set,its treatment effect can reach the enterprise’s standard,and successfully realize the industrialization operation.