页岩气压裂返排液电化学处理现场试验研究

Field test research on electrochemical treatment of shale gas fracturing flowback fluid

页岩气压裂返排液盐度高、有机物含量丰富,在回用和外排前需进行深度处理。构建了2 m^(3)/h的电絮凝-电化学氧化集成工艺装置,在某页岩气开采平台开展了压裂返排液现场处理试验,该平台水质波动大。结果表明,在长周期运行过程中,经优化后的电絮凝-化学絮凝联用工艺可降低系统电耗和排泥量,电化学氧化深度降解COD符合一级反应动力学模型。当采用电絮凝电流35 A、电化学氧化电流60 A、停留时间均为10 min、辅助聚合氯化铝(PAC)投加量350 mg/L、Na_(2)CO_(3)投加量550 mg/L时,压裂返排液中悬浮物、硬度和COD均稳定达到100 mg/L以下,满足《页岩气储层改造第3部分:压裂返排液回收和处理方法》(NB/T 14002.3—2015)的回用要求和后续外排脱盐处理需求。药剂投加量较常规化学絮凝法可降低70%以上,污泥产生量降低约30%,直接运行成本约28元/m^(3)。整套工艺具备良好的抗冲击能力,污染物去除效率高,成本较低,为油气开发中的压裂返排液处理工程建设提供了技术支撑。

The shale gas fracturing flowback fluid has high salinity and rich organic matter content,which requires advanced treatment before reuse and discharge. An integrated electrocoagulation-electrooxidation process unit of 2 m^(3)/h was constructed. The field treatment test of fracturing flowback fluid was carried out on a shale gas exploitation platform and the water quality of the platform fluctuated greatly. The results showed that the optimized electrocoagulationcoagulation combined process could reduce the power consumption and sludge discharge of the system in the process of long cycle operation,and the deep degradation of COD by electrochemical oxidation conformed to the first-order reaction kinetic model. Under the comdition of 35 A electrocoagulation current,60 A electrooxidation current,10 min residence time,350 mg/L PAC dosage and 550 mg/L Na_(2)CO_(3) dosage,SS,hardness and COD of the fracturing flowback fluid were stable to below 100 mg/L. It met the reuse requirements and subsequent desalination requirements of Shale Gas Reservoir Stimulation Part 3:Recycling and Disposal Methods of Fracturing Flowback Water(NB/T 14002.3—2015). Compared with the conventional chemical flocculation method,the dosage of chemicals could be reduced by more than 70%,the amount of sludge could be reduced by about 30%,and the direct operating cost was about 28 yuan/m^(3). The entire process had good impact resistance,high pollutant removal efficiency and low cost,which provided technical support for the construction of fracturing flowback fluid treatment projects.