页岩气压裂返排液再利用处理技术研究

Study on treatment technology of reusing shale gas fracturing flowback fluid

页岩气压裂返排液具有黏度高、悬浮物质量分数高、成分复杂等特点,对其进行回用处理可减轻环境污染、节约水资源。以延长页岩气为对象,进行"氧化-絮凝"工艺处理页岩气压裂返排液的研究。结果表明,以硫酸亚铈作催化剂且质量浓度为100 mg/L、双氧水质量分数为0.3%及硫酸亚铁质量浓度为140 mg/L时,可使返排液黏度由原来18.09 mPa·s降低到2 mPa·s以下;调整氧化处理后的返排液pH为7.5,在PAC质量浓度为600 mg/L,PAM质量浓度为20 mg/L时进行絮凝处理,处理后水中悬浮物由处理前的2 490 mg/L降低到0.9 mg/L,含油量由处理前的37.25 mg/L降低到4.32 mg/L。处理后水质满足平均空气渗透率≤0.01μm^2的地层回注要求。

Shale gas fracturing flowback fluid has characteristics such as high viscosity,high content of suspended substances,complex composition,etc.Recycling and reusing this kind of fluid can reduce pollution to the environment and save water.Taking shale gas in Yanchang as an example,the＂oxidation-flocculation＂process is applied to treat shale gas fracturing flowback fluid.The result shows that the viscosity of flowback fluid can be reduced from the original 18. 09 mPa·s to below 2 mPa·s when the adding amount of cerium（ Ⅲ） sulfate catalyst is 100 mg·L^（-1）,the content of Fenton reagent is 0. 3% hydrogen peroxide and the concentration of ferrous sulfate is 140 mg·L^（-1）.The flowback fluid after adjustment and oxidation treatment has a pH of 5,and then is flocculated under the conditions that the dosages of PAC and PAM is 600 mg·L^（-1） and 20 mg·L^（-1）,respectively.The content of suspended substances in the water after flocculation decreases to 0. 9 mg·L^（-1） from 2 490 mg·L^（-1） before flocculation,and that of oil decreases to 4. 32 mg·L^（-1） from 37. 25 mg·L^（-1）. After＂oxidation-flocculation＂ treatments,the water quality can meet the reinjection requirements with an average air permeability less than or equal to 0. 01 μm^2 and can also be used repeatedly to formulate fracturing fluids.