Effect of Chemicals on Gel Breaking of Associative Structure Fracturing Fluid

Supermolecules used in fracturing fluids form associative structures, making the gels of the fracturing fluids very difficult to break. Studies on the effects of several additives on the gel breaking performance of fracturing fluids at 90℃ were conducted. The fracturing fluids used have supermolecular associative structures in them, and the additives tested include organic solvents, peroxide, diesel oil, kerosene, alcohols and mixture of these additives. It is found that at 90℃, addition of 0.5% ethylene glycol monobutylether and 0.5% triethanolamine in a fracturing fluid reduces the viscosity of the fracturing fluid by 80 mPa·s and 77 mPa·s, respectively, and the minimum viscosity of the fracturing fluid maintains at 30 mPa·s. Addition of 0.1% sodium persulfate in a fracturing fluid reduces the viscosity of the fracturing fluid to 4.312 mPa·s in 120 min, showing remarkable potential in gel breaking. Addition of 0.6% diesel and 0.6% kerosene in a fracturing fluid, breaks the gel in 50 min and 40 min, respectively. Interaction between poly fatty alcohols and the association polymers will reduce the viscosity of the fracturing fluid; addition of 1.0% n-octanol reduces the viscosity of fracturing fluids containing supermolecular associative structure to 24 mPa·s. Mixture of chemicals can also reduce the time for gel breaking. For instance, a mixture of 0.03% FeSO4 and 0.1% ammonium persulfate reduces the time by 60 min, and so does the mixture of 0.05% FeS and 0.1% ammonium persulfate. Using the methods described above, gels of fracturing fluids containing supermolecular associative structures can be broken, with no intervention from crude oil.