Research On Numerical Analysis Method Of Collision And Fragmentation Of Sand-carrying Fracturing Fluid Particle Group And Coupling Vibration Of Pipeline

With the continuous and rapid development of my country’s economy,the demand for energy is increasing day by day,and the exploitation of conventional oil and gas resources is difficult to meet.The exploitation of unconventional oil and gas resources will surely become the main way of oil and gas supply.Unconventional oil and gas resources are difficult to exploit,and targeted exploitation technologies such as artificial reservoir reconstruction and hydraulic fracturing are required.In the application of hydraulic fracturing technology,the sand-carrying fracturing fluid in the surface high-pressure manifold and the wellbore is a solid-liquid two-phase non-Newtonian fluid with a high Reynolds number.Non-uniform fluid supply of fracturing trucks,variation of formation fracture pressure,turbulent flow due to changes in local channel structure,the collision and accumulation of sand particles,etc.,will cause the fluid pressure in the pipeline to fluctuate,resulting in abnormal vibration of the pipeline,resulting in local cracking of the pipeline and connection thread thorns,erosion and fracture failure of some tools,as well as sand grinding and crushing,etc.The research on the numerical analysis method of particle group collision and fragmentation of sand-carrying fracturing fluid and coupled vibration of pipeline has a clear engineering application prospect.The field coupling problem has strong academic value and can provide theoretical support for the two-phase flow-induced vibration control of flow pipelines and high-pressure manifolds.An indoor solid-liquid two-phase flow and pipeline coupling vibration experimental system was built.The effects of the diameter ratio of the reducer,the length of the reducer,the fluid flow rate and the sand ratio on the vibration of the pipeline were experimentally studied.The coupled vibration results of the solid-liquid two-phase flow and the variable-diameter pipeline are obtained,which provides experimental verification for the numerical analysis method of the two-phase flow of the sand-carrying fracturing fluid and the coupled vibration of the pipeline.A numerical analysis method of two-phase flow coupled with sand-carrying fracturing fluid was established.Establishment of time-domain discrete particle motion trajectory equation by central difference method,introduce interpolation function,the weighted average of the velocity before and after the particle collision is solved by the momentum theorem.Through the speed convergence criterion,the initial value speed is corrected and the number of iterative solutions is automatically adjusted.The particle collision force is calculated by elastic theory.According to the normal and tangential stress,the particle collision and crushing criterion is proposed,so that the numerical calculation time of the established particle collision model does not depend on the calculation step size.Use the target particle motion trajectory as the diagonal of the search grid to form a variable space search grid,and create a collision search list.The reverse collision search is carried out along the particle running trajectory,so that the calculation accuracy and efficiency of the particle collision search algorithm are not affected by the calculation time step.Create particle-fluid coupling convergence conditions according to the transfer method of fluid-particle coupling physical parameters.For the local non-convergence region,divide the sub-computation domain.The judgment conditions are activated through the sub-computation domain,the solution area is automatically selected,and the coupling calculation time step is corrected,so that the solution scale of the fluid-particle coupling numerical analysis method can be controlled.Through two-particle and multi-particle collision examples,the accuracy and efficiency of the reverse iterative algorithm for particle collision search are verified.The accuracy and efficiency of the sub-domain solution algorithm are verified by the single particle settling example in finite fluid and the particle following example;the accuracy of the particle crushing criterion is verified by the proppant crushing example.A numerical analysis method of two-phase flow of sand-carrying fracturing fluid and coupled vibration of pipeline is established.Considering the interaction of particle collision and fragmentation and the change of fluid flow field on the pipeline vibration,the finite element method is used to solve the pipeline dynamics.The parameter transfer and convergence conditions of the coupling vibration between the two-phase flow of the sand-carrying fracturing fluid and the pipeline are given,and the numerical solution algorithm of the coupling between the two-phase flow and the pipeline is proposed.Numerical simulation of indoor solid-liquid two-phase flow and pipeline coupled vibration experimental conditions.The result shows,The higher the fluid flow rate,the larger the particle-sand ratio,the larger the variable diameter pipe length,and the smaller the variable diameter ratio.The larger the amplitude of the pipeline vibration acceleration,the vertical direction is slightly larger than the horizontal direction,and the vibration frequency is between 7.9Hz and 14.5Hz.The error between the numerical simulation results and the experimental results of the pipeline vibration acceleration amplitude and vibration frequency is less than 15.0%.Using the numerical calculation method of the two-phase flow of sand-carrying fracturing fluid and the coupled vibration of the pipeline,the influence of the changes of flow parameters and structural parameters on the vibration amplitude at the inlet,middle and outlet of the pipeline is analyzed.The results show that the order of influence on the vibration amplitude of the variable-diameter pipeline from large to small is flow rate,diameter ratio,variable-diameter length,and sand ratio.,fluid viscosity,sand ratio,particle size.