电化学工艺处理油田聚合物型压裂返排液

Electrochemical treatment process of polymer fracturing flowback fluid in oilfield

压裂技术已逐渐成为油田增产的主要手段。随着更加严格的《陆上石油天然气开采工业污染物排放标准》的即将颁布,新疆玛湖油田在未来几年可能会面临大量聚合物型压裂返排液外排的压力。基于高效、低成本的处理要求,开发了“电絮凝预处理+电化学氧化”工艺处理压裂返排液。结果表明:当电絮凝预处理条件为阴阳极板均为铝板、极板间距为0.5 cm、电流密度为10 mA/cm^(2)、通电时间为15 min时,压裂返排液COD去除率达到65.4%,浊度达到4 NTU。对电絮凝预处理后的压裂返排液进行电化学氧化处理,在阳极为镀钌铱钛板、阴极为不锈钢板、电流密度为25 mA/cm^(2)、电源脉冲频率为4 000 Hz、占空比为65%、pH=7.2、反应时间为90 min的条件下,新疆玛湖油田压裂返排液COD可以降至80 mg/L以下,油质量浓度降至1.0 mg/L以下,氨氮降至0.5 mg/L以下,悬浮物降至30 mg/L以下。处理后压裂返排液水质指标满足陆上排放标准要求且成本较低,具有良好的工业应用前景。

Fracturing technology has gradually become the main mean of oilfield stimulation. As more stricter Emission Standard of Pollutants for Onshore Oil and Gas Exploitation and Production Industry is to be issued,the Mahu oilfield in Xinjiang is likely to face the pressure of polymer fracturing flowback fluid efflux in the next few years. Based on the requirements of high efficiency and low cost,a process combined of electric flocculation pretreatment and electrochemical oxidation was developed to treat fracturing flowback fluid. The results showed that with the electrocoagulation pretreatment condition of the anode and cathode plates both aluminum plates,the distance between the plates 0.5 cm,the current density 10 mA/cm^(2),and the electrification time 15 min,the COD removal rate of fracturing flowback fluid reached 65.4%and turbidity reached 4 NTU. The fracturing flowback fluid after electrocoagulation pretreatment was treated by electrochemical oxidation. Under the conditions of ruthenium-iridium plated titanium plate as anode,stainless steel plate as cathode,current density of 25 mA/cm^(2),pulse frequency of 4 000 Hz,duty cycle of 65%,pH=7.2,and reaction time of 90 min,COD of fracturing flowback fluid of Xinjiang Mahu oilfield could be reduced to less than 80 mg/L,oil mass concentration to less than 1.0 mg/L,ammonia nitrogen to less than 0.5 mg/L,suspended matter to less than 30 mg/L. The water quality index of the treated fracturing flowback fluid met the requirements of the onshore discharge standard and the cost was low,which had an excellent industrial application prospect.