Study On Erosion And Structure Optimization Of The Nozzle For Oil And Gas Well

The nozzle is a very important component of controlling flow and pressure in the high pressure oil and gas wells,this kind of oil and gas wells have high velocity,high pressure and complicated flow state,which can easily cause erosion of nozzle.The frequent replacement of nozzles caused by erosion damage has brought serious trouble to the safe production of gas walls.Based on the analysis of throttle theory,experiment and numerical simulation,the erosion and structure optimization of throttle nozzle are proposed in this paper.Firstly,the flowing law of natural gas or fluid flowing through throttle nozzle is analyzed based on Fluid mechanics theory for the natural gas or oil well and the calculation formula of throttling pressure drop of the nozzle under the condition of fracturing and blowout is obtained,in addition,Effect of different wellhead pressure,different flow rate and nozzle size on throttling pressure drop of nozzle are analyzed.The results show that the throttling pressure drop is linearly related to the length of the nozzle for the liquid flowing through the nozzle.When the diameter of the nozzle is more than 8 mm,the influence of the nozzle length on the throttling pressure drop is very small,and the throttling pressure drop and the nozzle diameter show a power function relation.The effects of erosion angle and flow velocity on the erosion rate of 42 CrMo steel,kentanium and ceramics are investigated by the self-made jet erosion experiment device.The morphologies of surface on the erosion angle and jet velocity were investigated by SEM.The experimental results show that The erosion mass loss of 42 CrMo steel increases firstly and then decreases with the increasing angle,and reaches the maximum at 30°.The erosion rate of kentanium and ceramics increases with increasing impact angle.An erosion calculation formula of kentanium and ceramics for fracturing and blowout condition is obtained by fitting the test dates.The liquid-solid two phase flow field distribution and erosion of the nozzle under the condition of fracturing and blowout condition is analyzed by the CFD numerical simulation method.The calculated model of erosion is applied to FLUENT software.The flow field and erosion change of the nozzle is analyzed by changing the nozzle diameter and length,the nozzle structure is optimized according to the flow field simulation results.The simulation results show that the throttling pressure drop has a linear relationship with the nozzle length and a power function relation with the nozzle diameter.When the length of the nozzle is constant and the diameter of the nozzle is changed,the bigger the nozzle diameter,the smaller the pressure drop.The smaller the diameter,the more obvious the pressure drop is;and when the diameter of the nozzle is constant and the length of the nozzle is changed,the bigger the nozzle length,the bigger the pressure drop,but the trend is not obvious.The erosion rate of power rate fluid is much higher than that of water medium.Compared with the constant diameter nozzle,the flow resistance of the nozzle with variable diameter structure is smaller for the same throttling pressure drop,the flow rate of the variable diameter nozzle is larger and the erosion is smaller.The maximum erosion rate of nozzle appears at the nozzle inlet.