Study On The Sand-carrying Performance Of Nano-worm-like Micellar Fluid

Viscoelasttic Surfactant(VES)can form worm-like mice lies up to micrometers.As the concentration of worm-like micelles exceeds the critical micelle concentration,these micelles are entangled with each other to form a network structure,showing higher viscoelusticity similar to polymer.The main advantage over polymers is that its viscoelasticity can recover by self-assembly after undergoing high shearing,which is called a Jiving polymer.The use of nanopartides to modify the worm-like micelle system can improve the stability of the worm-likc micelle solution.As a novel oilfield fracturing fluid,it can reduce the construction friction and enhance the sand carrying capacity.ZnO nanometer powders are utilized(to modify octadecy ltrimethy lammonium chloride(OTAC)under the sodium saticylatc(NaSal)counlerkm.and is supported by a combination of experiments and numerical simulations.The rheological properties of the nano-modified worm-like micelle solution shows that the optimized content of ZnO is 0.lwt%for the solution with 2.8wt%OTAC and 0.56%NaSal.Experimental results show that the zero shear rule of the na no-modified worm-like micelle is 2 times higher than that that of the worm-like micellar fluid without nunu-muuificaliun.At the range of angular frequency from 0.01 to 100 Hz,and the difference between the elastic modulus and the viscous modulus of the preferred system is the largest than other formuk.The Theological experimental data were fitted by the Giesekus and the Cross constitutive equation,respectively.Based on the Giesekus constitutive equation,the viscoelastic fluid numerical simulation and visual experiment method were used to investigate the sedimentation process of single panicles in nano-modifiwJ worm-like micelles The results show that negative wakes are generated at the tails of settling particle.When the panicle surface shear rate is greater than the critical shear rate,the appearance of a negative wake reduces the drag force of Lhe particles when ihcy settle in the nano-modified worm-like micelle fluid,and the settling velocity increases.As the particle surface shear rale is less than the critical shear rate,the combined effect of the stretching of the negative wake and the elastic zistss on the particle surface can cause the particle terminal velocity to increase first and then decrease with the increase of relaxation lime.Then,the sedimentation of iwo particles in the oano-modified worm-like micellar fluid is investigated.As two particle’s are settling horizontally,the negative wake arta incrcases with inert ming the distance between the particles,and the elastic stress on the surface of the particles increases,resulting in a decrease in the sedimentation velocity of the particles.When two particles are settling vertically,the upstream particle inhibit the sedimentation of the downstream particles,resulting in a decrease in the elastic stress of the upper particles as the distance between the particles is less than 1.5 times of the particle diameter.However,as the distance between the particles is larger than the particle diameter of 1.5,the upstream particle promote the sedimentation of the downstream particles.As a result,the particles will be arranged in the direction of flowing in the nano-modified worm-like micelles.At last,based on the Cross constitutive equation and Euler-granular multiphase flow model,the sand-carrying flow of the nano-modified worm-like micelle in fractures were investigated.The self-designed fracture slit facility was used to verify the model.The results show that the sand-carrying capacity of the nano-modified worm-like micelle is significantly better than water.The use of proppant with low sand ratio,low density and small particle size is beneficial to reduce the balance height of sand carrying in the cracks.Extend the paving distance between the inlet and the balance height of the proppant,reduce the risk of sand plugging,and improve the sand-carrying capacity of the fracturing fluid.