Erosion Prediction Of Bypass Crossover Sub In Horizontal Wells

Fracturing is an important measure for the stimulation of low-permeability reservoirs in oilfields to improve oil recovery.The double-sealed and single-stuck fracturing technology can realize multi-staged fracturing of horizontal wells and effectively transform reservoirs.However,the flow rate and the proppant volume were consecutively increased with the development of reservoir reconstruction.When the fracturing fluid entrained proppant is injected into the formation through the bypass crossover sub.When the fluid flows through this crossover tool,the flow direction is changed,and the solid proppant in fracturing fluid will impact the sub surface consecutively and cause serious erosion,even the failure of the tool.Therefore,the numerical simulation is used to simulate the solid-liquid flow inside the bypass crossover sub.Combined with the erosion models,the internal flow field and the erosion of the bypass crossover sub are analyzed based on different operating conditions.According to the actual fracturing operating conditions,the bypass crossover sub model was established to calculate the internal flow field.The realizable k-? turbulence model was selected to simulate the turbulent flow.The two phases were calculated after adding the discrete phase model.Considering the coupling effect between two phases and the effect of particle impingement,the particle tracking model is used to calculate the motion of particle.Finally,three different erosion models,Arabnejad model,Oka model and E/CRC Zhang model,were used to simulate the erosion of target wall.The LDA test was carried out for testing velocity of the internal flow field of the bypass crossover sub.The velocity distribution law of the flow field at the bypass crossover sub hole region was obtained.The flow field under different Reynolds numbers was measured.The experimental data and the numerical results were compared and analyzed.The numerical simulation results are in good agreement with the experimental test results,which verifies the reliability of the numerical simulation method.The flow field of bypass crossover subs in the central and the eccentric position were simulated under different flow rates.The distribution of flow field and proppant concentration were analyzed.Three different erosion models,Arabnejad,Oka and E/CRC Zhang erosion models,were used to simulate the crossover sub.The simulation results of erosion were compared with the sub after fracturing.The results show that the erosion prediction of bypass crossover sub in the central position is different from the sub in the eccentric position.Oka erosion model predicted the highest erosion rates.E/CRC Zhang predicted the lowest erosion rates.Numerical results predicted by Oka model was close to actual fracturing outcome.Therefore,Oka erosion model was selected to further investigate the fluid flow characteristics and the factors affecting erosion characteristics of sub tool.The erosion characteristics was analyzed based on different flow rates,particle sizes and the viscosity of fracturing fluid.The results show that the vortical structure keep constant as the flow rate is increased,while the strength of eddy is increased hugely.The erosion is more severe as the flow rates are increased,which the mass flow rate is constant.The flow rate is the key factor of influencing erosion behavior.The difference of pressure drop between the central location and the eccentric location is increased as the flow rate increases.The maximum erosion rates increase gradually with the increase of particle sizes,however,the average erosion rate is not relatively increased.The severe erosion region is similar with the increase of fracturing fluid viscosity.The erosion rate does not change significantly with the fracturing fluid viscosity.This paper can provide a reference for the study of the erosion prediction of the bypass crossover sub.At the same time,it also provides a certain reference for the optimal design of the double-sealed and single-stuck fracturing tool.