Dynamic Analysis Of Multiphysics Coupling Of Fracturing Fluid And Sand And Pipe

With the development of oil and gas resources exploitation technology,hydraulic fracturing technology has gradually become the key technology to develop unconventional oil and gas resources.During the fracturing process,the solid-liquid two-phase fracturing fluid in the pipeline(column)will cause fluid pressure fluctuation due to the non-uniform fluid supply of the plunger pump,the flow pattern transition of the local flow channel,particle collision and instantaneous accumulation,which will lead to abnormal vibration and erosion damage of surface pipelines and downhole pipelines.Therefore,the coupled vibration and erosion analysis of solid-liquid two-phase fracturing fluid and pipeline(column)not only has strong academic value,but also has prospect of engineering application.The purpose of this paper is to establish the multi-physical field coupling analysis theory of fracturing fluid turbulence dynamics,particle group kinematics and pipeline(column)vibration,which can provide theoretical support for fracturing construction design,pipeline(column)vibration control and erosion prediction.Firstly,according to the structure and process parameters of pipeline(column)in field fracturing construction,the experimental device of pressure loss and induced pipeline vibration of solid-liquid two-phase fracturing fluid is designed and built.In this paper,the effects of fluid velocity,sand ratio,concentration of thickener and diameter ratio on pressure loss and vibration of contraction and expansion pipe were studied experimentally,the calculation method of hydraulic pressure loss of sand fracturing in contraction and expansion pipe and the data of coupling vibration of contraction and expansion pipe are obtained,which provide a basis for the verification of subsequent theoretical methods.Secondly,it is assumed that the pipeline does not vibrate,the fracturing base fluid and quartz sand in the pipeline are selected as the research objects.Considering the factors such as fluid-particle interaction force,particle-group collision,coupling solution efficiency and solution accuracy,and the method is based on the two-fluid model and discrete element method,the formulas for calculating the physical parameters of the transfer between particles and fluids,the iteration convergence conditions and the time-marching algorithm are deduced,and the dynamic analysis model and calculation method for fluid-particle group coupling are established.The accuracy of the CFD-DEM method is verified by comparing with the existing examples and experimental results,which provides an effective calculation method for revealing the motion,collision and accumulation of particles in solid-liquid two-phase flow,and enriches the theory of coupled dynamics of particles and fluid.Thirdly,by calculating and analyzing the particle-group and fluid coupling dynamics of different fracturing fluid velocities and sand ratios in straight pipe,expansion pipe,elbow pipe and T-shaped pipe,the following conclusions are obtained: For straight pipes,the greater the inlet velocity and sand ratio,the more severe the collision of particles in the pipes,and the greater the fluid pressure loss.For the contraction-expansion pipes,the larger the inlet velocity is,the larger the sand ratio is,the smaller the diameter ratio is,the larger the sudden contraction angle is,the more serious the collision and accumulation of particles in the sudden contraction section is,the greater the fluid pressure loss and the erosion rate of the sudden contraction section is.For the bent pipes,the larger the inlet velocity,the larger the sand ratio and the smaller the curvature ratio,the more obvious the phenomenon of increasing speed and reducing pressure inside the elbow,the greater the fluid pressure loss and the erosion rate outside the elbow.For T-tube,the greater the inlet velocity,the larger the sand ratio and the smaller the diameter ratio,the greater the fluid pressure loss and the branch pipeline erosion rate.The inlet and outlet forms of T-tube have significant effects on fluid flow field and particle group motion characteristics.Finally,based on the dynamic solution algorithm of fluid-particle group coupling and the sub-domain solution algorithm of fluid-pipeline coupling,the effects of particle collision,accumulation on fluid flow field and pipeline displacement field in two-phase flow are considered,as well as the effects of pipeline motion and fluid flow on particle concentration field,the physical quantity transfer method,iterative convergence condition and time advance algorithm for fluid-particle group-pipeline multi-physical field coupling are established,and the dynamic solution algorithm for fluid-particle group-pipeline multi-physical field coupling is given.Through the calculation and analysis of the coupled vibration of the pipeline,particle group and fluid in the simulation experiment,the results show that: In this paper,the relative error between numerical simulation and experimental results is less than 15%.The results show that the higher the velocity of two-phase flow,the larger the sand ratio and the smaller the diameter ratio,the larger the vibration acceleration amplitude of the pipeline;the larger the vibration acceleration amplitude of the vertical pipeline than that of the horizontal pipeline;the largest vibration acceleration amplitude is in the middle position,the second is in the entrance position and the smallest in the outlet position;High sand ratio can introduce high frequency vibration with low amplitude.The purpose of this paper is to establish the theory of multi-physical field coupling analysis of fracturing fluid turbulence dynamics and particle-group kinematics with pipeline(column)vibration.A fine numerical model and an efficient calculation method are proposed to provide theoretical support for fracturing engineering design,pipeline(column)vibration control and erosion prediction,and to promote the rapid development of large-scale fracturing technology and other new technologies.