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.