Study On The Applied Technology Of The Innocuous Treatment Of Drilling Wastewater In Oilfield

In this paper the drilling wastewater from the exploitation of petroleum and natural gas in domestic oilfield is treated with combined technology of chemical coagulation and microeletrolyte,the main research content contain as follows:1. The research and analysis of drilling wastewater: The drilling wastewater in zhongyuan oilfeild were investigated and analysized, the drilling wastewater of ten wells were collected, the first kind of pollutant(the poisonous inorganic heavy metal ion) and the second kind of pollutant(the suspensible solid and the organic compand decompanded difficultly by biologic and chemical method of drilling wastewater were analysized mainly.The results of the research and analysis showed that the value of pH of drilling wastewater is 7-10,the density of drilling wastewater is within 1.0-1.12 g/cm³,the turbidity value is within 374-16000mg/L, it belongs to high or middle turbidity wastewater. The chemical oxygen demand of drilling wastewater is within 1000-60000mg/L, it is more than 5-200 times of the standard value. The colour and iustre of drilling wastewater is high,and it is dust-colour or black-brown.the several poisonous metal ions are paranormal.The drilling wastewater has the characterizations that the chroma,the turbidity, COD_Cr and stabilization are all high.2. The Study on chemical cogulation process of drilling wastewater:the drilling wastewater is dealed with chemical cogulation process and the inorganic coagulants are filtrated and appraised ZB and ZB1 which are inorganic single medicament and mulripe are regarded as coagulant, then the systemal study is made.The drilling wastewater high turbitidy and high COD_Cr is regarded as experimental sewage and the influence of the categories and dosage of inorganic coagulants, the organic flocculants and gelling agents are studied,And the influenc of the value pH,the adding sequence of agents ,the agitation speed on solid-liquid seperation speed and the the coagulation effects are determinded.The best chemical agents of chemical enhanced solid-liquid seperation are screened out:1500³000mg/L ZA(inorganic acid)+ 5000mg/L ZB1(inorganic coagulant)+ 800mg/L lime white(gelling agent)+ 40mg/L ZC(organic agent)o The aim of the chemical coagulation is removing suspendible solid oil substance and chroma and COD But the dealed water cant meet the requirement of the GB8978-1996 wastewater drainage standard, so the deeper removing of chroma and COD is needed.3. The study on the technology of micro-electrolysis for drilling wastewater: Thedepth treatment of the treated drilling wastewater dealed by coagulation were explored, and used secondary coagulation, super filtr, catalytic oxidation and micro-electrolysis to filtrate and appraise. It was found that the method of micro-electrolysis has the advantages of treating effect and cost. The method of micro-electrolysis was systemitically studied,and the influence of the pH value,the dosage of iron scraps,the dosage the reactive carbon,the quality rate of iron and carbon and the reaction time to the removing of CODq and chroma, the dynamic experiment of micro-electrolysis is made.The flowing time of solution.the size of particals.the life of volume bed and flowing velocity of solution on the value of CODcr of ceitflow were determined.The dynamic parameters of micro-electrolysis was ascertained by indovr amplificatory tests.The iron-carbon micro-electrolysis was applied on the deeper treatment of drilling wastewater. the optimal formula and technologic coodion are as follows: The pH value of wastewater is 1.0 , the quality rate of iron scraps and reactive carbon is 0.67, the reactive time is 1.0h,the flowing time in column bed is 20 min., After the reaction the pH value was dejusted to 11¹2, the quantity of macromolecule organic folcculation is 10mg/L>the sedimentation time is within 20³0min, the pH value of filtrated wasewater was regulated to be within 6-9 by watery vitriol.4. Determining the toxicity of rechemental mud of the drilling wastewater: The toxicity of rechemental sludge from coagulation and micro-electrolysis were analysized and determined. The result shows that the contents of the main contamination are low and accord with the standart of dangerous waste <>GB5085.3^ 5085.1-1996> and the contents are lower than country <> Supreme permission value that GB18599-2001 stipulates, so well drilling firm moisture dreg mud is it separate to dehydrate by high-speed centrifugal separator or person who press board frame pigeonhole person who strain press after dehydrating, can bury on the spot, store or pile up for a long time , will not cause danger to the peripheral ecological environment.5. The spot test of coagulation/micro-electrolysis of drilling wastewater: The spot test is made for 204 times, the total capacity of treating drilling wastewater is more than 3000m3. The treated wastewater is inspected by the environmental monitor centre that the indexes accord with the standard of wastewater emission GB8978-1996. 6. The value of chromaticity and CODCr of drilling wastewater were mainly removed with coagulation and micro-electrolysis two process.lt can solve the problem thoroughly of environmental emission standard of drilling wastewater and the technics is simple.The coagulation and micro-electrolysis two process isespecially suitable for treating the complicated system of drilling wastewater of high turbidity, high chromaticity and high CODcr.The experimental results show that the applicable scope of the coagulation and micro-electrolysis two process is wide.The method solves the difficult problems of the drilling wastewater to guarantee the sanitary production of artesian well.