Mechanical Research And Software Development Of Tubing String In High Production Gas Well

At present,the mechanical analysis and strength check of the tubing string are mostly based on static mechanic.However,the impact of the high-speed airflow on the tubing string in the high-productivity gas well will cause the tubing vibration and stress change,leading to degraded strength and even tubing string failure.Therefore,tubing string dynamics is also a very important research content.In order to investigate the mechanical property and working state of tubing string under dynamic loading,the dynamic and static mechanical analysis of the tubing string are conducted.The main research contents and achievements are as follows:(1)According to the actual force of the tubing string in the production process,the mechanical-mathematical model of packer-tubing string deformation is established,considering piston effect,spiral buckling effect,ballooning effect,temperature effect and friction effect.The complex mechanical deformation of the tubing string is obtained under these five effects with the changing of production and oil pressure.(2)Based on the theory of modal analysis,the mathematical model and finite element model of longitudinal vibration of tubing string are established,and the mutual verification is carried out.By modifying the parameters of the finite element model,the main factors influencing the natural frequency of the longitudinal vibration of tubing string are obtained.The main factors considered in this dissertation are string length,string size,composite pipe string,packer restraint,string buckling and so on.At last,the longitudinal resonance of the tubing string is verified by harmonic response analysis.(3)Based on the principle of transient dynamics,the finite element model of tubing string in the high-productivity gas wells is established using APDL language of ANSYS software.The longitudinal response displacement,velocity of different sizes of tubing string are analyzed at different time.The axial force,Von Mises stress and tubing string buckling state changes are analyzed in the vibration process.(4)According to the mechanical model of the dynamic and static established in this dissertation,a mechanical evaluation software is developed for high-productivity gas well.With the software,real-time diagnosis of mechanical properties of tubing string can be realized,and safety gas production and oil pressure can be obtained in the production process.The mechanical evaluation software provides a theoretical basis for safety operation of tubing string in high-productivity gas well.