Study On Separation Performance Of Shale Gas Desander

Sand production in gas wells is a common problem in shale gas production.In the process of shale gas exploitation,a large amount of fracturing sand and formation sand are taken out of the wellhead,which not only causes erosion and blockage of surface gathering and transportation equipment,but also greatly threatens the safety of gas well production and equipment.In view of the above problems,based on the full investigation of the gas well operation site,this paper introduces the types,principles,advantages and disadvantages of the cyclone desander used in a shale gas well,and analyzes the adaptability of the desander.Based on the theory of multiphase flow separation,the structure model of cyclone desander is established.The flow field of desander is simulated by CFD numerical simulation software,and the influence of flow field characteristics and various parameters on separation performance is analyzed.Because there are many influencing parameters,multi-factor and multi-level analysis is used to obtain the parameters that have the greatest influence on the degree of separation,and the scheme is optimized.The relationship between separation efficiency and parameters is derived by linear regression and multiple stepwise regression.The main research contents and conclusions of this paper are as follows :(1)The types and characteristics of the main sand removal equipment in the current domestic shale gas production process and the adaptability of the equipment are studied.The numerical simulation method of gas-solid separation is discussed.A three-dimensional model is established for the sand remover used in a certain operation site,and the model is meshed by FLUENT Meshing.The RNG k-ε turbulence model and the DPM multiphase flow discrete phase model are selected as the Fluent numerical simulation method to simulate the internal flow field.(2)The gas flow field inside the cyclone desander is analyzed.The results show that there is a double vortex structure in the flow field of the cyclone desander,and the two are bounded by the zero axial velocity envelope surface.The centrifugal motion of the particles plays a decisive role in the separation performance,so the tangential velocity in the velocity field plays a major role in the separation.The radial velocity has little effect on the flow field,the pressure field distribution is symmetrical,and there is a negative pressure zone near the central axis.Due to the existence of turbulence in the flow field,the particles escape and the separation efficiency is reduced.Through the trajectory cloud map,the movement of single particles and particle groups with different particle sizes is tracked.The particle trajectory is stable,and the escape phenomenon of small particle groups is serious.As the particle size increases,the separation effect is significantly improved.(3)The influencing factors of the cyclone desander are divided into structural parameters and operating parameters,such as the length of the cylindrical section of the desander,the length of the lower cone section,the inlet flow rate,and the particle size.The single factor experiment method is used to carry out multiple sets of experimental simulations.It is concluded that the increase of the insertion depth of the overflow pipe and the length of the lower cone section is beneficial to the improvement of the separation performance.The cylindrical section is proportional to the separation efficiency within a certain range,and the increase of the diameter of the overflow port reduces the separation efficiency.For operating parameters,inlet velocity and particle size are positively correlated with separation efficiency.Excessive particle concentration will cause flow field disorder and poor separation effect.(4)The orthogonal experiment was designed,and the experimental results were analyzed.The range analysis and variance analysis were used to evaluate the influence of each parameter on the separation performance.The optimal scheme was selected by combining the two analysis methods,and the optimal parameters were obtained.The results show that the insertion length of the overflow pipe,the length of the cylindrical section,the diameter of the overflow port,the particle size and the particle concentration have a significant effect on the separation performance.The structural parameters are optimized as the length of the cylindrical section 430 mm,the length of the lower cone section 790 mm,the insertion depth of the overflow pipe 140 mm,and the diameter of the overflow port 80 mm.At the same time,the separation efficiency of the desander reaches the optimal value when the inlet velocity is 18.4m / s,the particle size is 20μm,and the particle concentration is 6.14 kg / s.The regression analysis method is used to obtain the relationship between the operating parameters and the structural parameters on the separation efficiency.By comparing and selecting the multiple stepwise regression equation,the fitting of the equation is good,which has important reference value for the future improvement of the desander structure and the adjustment of the working conditions in the actual production process.