Study On Improving The Viscoelasticity Of Cleaning Fracturing Fluid

The performance of fracturing fluid is directly related to the effect of hydraulic fracturing.There are certain requirements for suspension performance,stability and formation permeability in oil and gas development.The clean fracturing fluid has high viscoelasticity and no residue.Because of its excellent sand carrying property and lower reservoir damage,it has attracted wide attention.However,there is still a poor temperature tolerance.In this paper,the temperature resistance of erucic acid amide hydroxysulfonated betaine(EAAHSB)and erucic acid amidopropyl betaine(EAAPB)at 80?was compared.It was found that the viscosity of EAAHSB could be maintained at 52 m Pa·s at 4%concentration,which had better temperature resistance and viscosifying properties than EAAPB,but it needed stirring for a long time to dissolve in the preparation process,and the solubility was insufficient at higher concentration.For the pure betaine system,the temperature tolerance of fracturing fluid system can only be satisfied at a higher concentration.Hydrophobically associating polymers can participate in the construction of wormlike micelles.Strong interactions such as winding and bridging occur between them,which can greatly improve the viscosity and temperature resistance of the composite system.In this paper,the effect of AP-P4 and AP-C16 hydrophobic associating polymers on betaine clean fracturing fluid was studied comparatively.It was found that the effect of AP-P4 was better than that of AP-C16.The temperature resistance,thixotropy and shear resistance of 1.5%EAAPB+0.1%AP-P4 composite system were improved compared with 1.5%EAAPB.Moreover,the system also has good sand carrying and breaking properties.The settling rate is only 0.037 mm s^-1 at 30%sand ratio,and the viscosity of breaking fluid is less than 8 m Pa·s.The surface area of nanoparticles is quite high.Surfactant molecules of clean fracturing fluid can be adsorbed on the surface of nanoparticles,thus bridging the worm-like micelles and increasing the viscosity.It is found that SiO₂ is more advantageous to increase the viscosity of fracturing fluid than BaTi₃,and the optimum concentration is 0.1%.At this concentration,the zero-shear viscosity of the system is the largest and the viscoelastic effect of the system is the best.It was found that nanoparticles did not affect the gel breaking performance of the system,and the viscosity of the gel breaking fluid was less than 6 m Pa·s,and the minimum settling velocity could reach 0.036 mm s^-1 at 30%sand ratio.