瓜胶压裂返排液重复利用的室内研究

瓜胶压裂液的返排液已成为油田水体的主要污染源之一。将压裂后的返排液处理后重新配制压裂液，不仅可以保护环境，还可以节约水资源，降低成本。为了简化处理流程，提高返排液处理量，引入定位除硼及金属离子的方法，最终实现返排液的重复利用。以官西-5井的压裂返排液为实验对象，分析了压裂返排液中无机离子、固体颗粒和残余硼对压裂液重复利用的影响。研究结果表明，11种无机离子对压裂液重复利用有不同程度的影响，并且总结得出了不同离子对压裂液配制影响的浓度限值；返排液经过高效破胶、絮凝、定位除硼及金属离子反应之后，石油类去除率达91.71%，浊度去除率达94.6%，色度去除率达95.8%，Ca2+、Mg2+、Fe2+和B浓度分别降至36.07、19.44、44.3和3.35 mg/L。研究了各种离子对返排液重复利用的影响，采用了定位除硼及金属离子的方法，根据返排液中残余硼及金属离子含量加入适量除硼剂和金属离子去除剂，将其浓度控制在影响范围内，该实验方法具有操作简便、处理量大，处理成本低等优点，便于现场推广应用。用处理后的返排液重新配制的瓜胶压裂液，在100℃剪切1 h后黏度仍保持在100 mPa s以上，满足《压裂液通用技术条件》要求，实现了压裂返排液的重复利用。 

Laboratory Study on Recycling of Flowback Fluid of Guar Gun Fracturing Fluid

Guar gum fracturing flowback fluid has become one of the main pollution sources to oilfield water. If the flowback fluid is used to re-mix fracturing fluid after treatment, it not only protects the environment from being polluted, but also saves water resource and reduces operation cost. To simplify the treatment process and to increase the volume of treatment, a method for the removal of boron and metal ions was introduced to realize the recycling of the fracturing flowback fluid. Sample of fracturing flowback fluid from the well Guanxi-5 was analyzed for the effect of inorganic ions, solid particles and residual boron on the recycling of the flowback fluid. The study showed that 11 inorganic ions in the flowback fluid affect its recycling to varying degrees. The concentration thresholds of these ions affecting the recycling process were summarized. Flowback fluid after gel breaking, flocculation, boron and metal ion removal, has its oil component removed by 91.71%, turbidity reduced by 94.6%, colourity reduced by 95.8%, and Ca2+, Mg2+, Fe2+ and B reduced to 36.07 mg/L, 19.44 mg/L, 44.3 mg/L and 3.35 mg/L, respectively. Boron remover and metal ions removers were added to control the concentrations of boron and metal ions within the acceptable ranges based on their concentrations in the flowback fluid. This experimental method, because of its advantages such as simplicity in operation, large volume of treatment and low cost, is easy to apply in field operation. A guar gum fracturing fluid made from a treated flowback fluid, has its viscosity remained above 100 mPa·s after shearing for 1 h under 100℃, satisfying the requirement of "General technical specifications of fracturing fluids," and realizing the recycling of fracturing flowback fluids.