超深气井完井管柱屈曲行为研究

超深高温高压气井由于井筒温度高、压力高,井下管柱屈曲风险高,易造成管柱失效或冲蚀加剧等问题。通过超深高温高压气井管柱静力学分析发现热生产和热关井两个工况下管柱屈曲风险最大。鉴于此,针对热生产与热关井工况建立了用于分析两种苛刻工况下全井段油管柱屈曲问题的有限元力学模型,定量得出两种工况下全井段油管柱的屈曲形态、横向位移、油管柱-套管接触力、弯矩与扭矩等力学参数。研究结果发现:在热生产工况下,油管柱发生了不稳定的屈曲形态,在油管柱屈曲段的上部与下部位置,油管柱与套管的接触较为密集;在热关井工况下,油管柱相对只发生了轻微的纯正弦屈曲。所建立的模型可用于油管-套管屈曲损伤失效分析,可为优化现场生产工艺和延长油管柱寿命提供理论依据。

Study of the Buckling Behavior of Completion Strings for Ultra-Deep Gas Wells

Due to high wellbore temperature and pressure,ultra-deep high temperature and high pressure(HTHP)gas wells have a high downhole string buckling risk that are very likely to cause string failure and worsened washout etc.problems.It is found that the string buckling risk under thermal production and shut-in conditions are the greatest through the statics analysis of strings for ultra-deep HTHP gas wells.Given this,finite element method(FEM)mechanical models were established specific to the problem of tubing buckling covering all intervals under two harsh operating conditions:thermal production and shut-in,which can be used to obtain quantitatively the buckling form,lateral displacement,tubing string-casing contact force,bending moment and torque etc.mechanical parameters of the tubing string covering all intervals under these two operating conditions.The results show that:under the thermal production condition,instable buckling occurred on the tubing string,the tubing and casing has intensive contact with each other at the upper and lower parts of the buckled section of the tubing string;under the shut-in condition,only trivial pure sinusoidal buckling occurred on the tubing string.The models established in this paper can be used to analyze the tubing-casing buckling damage and failure analysis and provide a theoretical basis for optimizing field production techniques and prolonging the life of tubing string.