Investigation On Erosion Characteristics Of Four Way Pipe For The Heavy Oil Thermal Production Wellhead Equipment

The four-way pipe used in heavy oil thermal recovery wellhead often causes leakage failure due to the erosion of gas carrying sand,which leads to resource waste and environmental pollution.The research on the erosion characteristics of the four-way pipe plays an important role in preventing the failure of the four-way pipe without warning and ensuring the safety and environmental protection of the heavy oil thermal recovery process.Based on the failure accident of four-way pipe in the process of heavy oil thermal recovery in an oilfield in Xinjiang,the failure mechanism of four-way pipe is analyzed firstly.Based on the establishment of erosion model suitable for four-way pipe material,the erosion mechanism of particles in fourway pipe is numerically simulated,and the prediction model of maximum erosion rate of fourway pipe is established.Firstly,based on the analysis of metallographic structure,mechanical properties,chemical composition analysis of materials,micro analysis of erosion morphology and qualitative and semi quantitative analysis of surface corrosion products of the four-way pipes which are failed in the actual production of Xinjiang Oil field.The erosion characteristics of ZG(J)35Cr Mo for four-way pipe under different impact angles and fluid velocities were studied by multiphase flow erosion test equipment.The results show that: the surface of the pipe material is slightly decarburized.and the chemical element silicon exceeds the standard,but the plasticity,toughness and impact resistance of the material change little.and there are obvious erosion marks,pits,loose pores and corrosion slag on the inner wall of the pipe,which indicates that the failure of the four-way pipe is not caused by the change of physical and chemical properties of the material,but by the erosion corrosion caused by the dominant role of erosion.The erosion rate of ZG(J)35Cr Mo material increases exponentially with the increase of fluid velocity.The erosion rate model of ZG(J)35Cr Mo material considering the impact angle and fluid velocity is established to provide basic data for the simulation of four-way pipe erosion characteristicsSecondly,based on the erosion rate model of ZG(J)35Cr Mo material,the flow field distribution,particle trajectory and erosion characteristics in the four-way pipe were studied by numerical simulation.The results show that the fluid velocity of the shoulder of the four-way pipe is low,the pressure is high,and the particles are concentrated,which indicates that the particles have great erosion effect on the shoulder of the four-way pipe.With the increase of fluid velocity,the maximum erosion rate increases exponentially,the erosion area on the shoulder decreases,and the erosion area on the top of the vertical pipe increases.With the increase of mass flow rate,the maximum erosion rate increases linearly,the maximum erosion area shifts to the right side of the shoulder,and the erosion area at the top of the vertical pipe decreases.With the increase of particle size,the maximum erosion rate first decreases and then increases,and the erosion area of the cross pipe increases gradually: from the shoulder to the top of the vertical pipe,and the erosion on the top of the vertical pipe intensifies.With the increase of particle density,the maximum erosion rate gradually decreases to stable,the erosion area of cross pipe increases,and the erosion at the top of vertical pipe increases.With the increase of sphericity,the maximum erosion rate decreases gradually,especially in the range of0.4 ～ 0.6,and the erosion area shifts from the horizontal pipe outlet to the shoulder and extends to the top of the vertical pipe.Finally,the geometric model of erosion wear of four-way pipe with defects is established.and the influence of different defect sensitive parameters(defect bottom side length and defect depth)on the erosion rate of four-way pipe with defects in straight pipe section and shoulder position is studied,which provides inspiration for understanding the dynamic development process of four-way pipe erosion perforation.The results show that the shoulder defect has a great influence on the erosion of the four-way pipe.The maximum erosion rate of the four-way pipe with shoulder defect is 5.896 times higher than that without shoulder defect when the flow velocity is in the range of 5～20m/s.The maximum erosion rate decreases with the increase of defect depth.The maximum erosion rate increases first and then decreases with the increase of defect area.