双封隔器间环空压力计算模型研究

双封隔器分层密封结构的密闭环空较高的环空压力,可能造成油管抗外挤强度及生产套管抗内压强度不足,严重时可能造成油套管柱失效或封隔器的密封失效,影响气井的正常生产作业。为此,基于流体介质的热膨胀效应,并考虑油管的弹性变形和热膨胀对环空体积的影响,建立了双封隔器间环空压力计算模型。利用建立的计算模型进行了算例分析并研究了流体介质的体积膨胀系数、等温压缩系数和套管内径对密闭环空压力的影响。研究结果表明:在相同温度变化量下,体积膨胀系数的增大会导致环空压力的变化量呈线性增加;等温压缩系数的增大会导致压力变化量减小,且减小幅度逐渐变小;套管内径的增大会导致压力变化量增大,且增大幅度逐渐变小。双封隔器间环空压力的研究对井身结构设计、套管强度设计、测试安全性设计及安全生产等具有一定的参考价值。

A Model for Calculating the Annulus Pressure between Double Packers

To deal with the pressure in the sealed annulus in the separate-layer sealing structure of double packers,a model for calculating the annulus pressure between double packers is established based on the thermal expansion effect of fluid medium,combined with the influence of elastic deformation and thermal expansion of tubing on the annulus volume.And this calculation model is used for example analysis.In addition,the influence of volume expansion coefficient of fluid medium,isothermal compressibility coefficient and casing inner diameter(ID)on the sealed annulus pressure is studied.The results show that under the same temperature variation,the increase of volume expansion coefficient can result in the linear increase of annulus pressure variation.With the increase of isothermal compressibility coefficient,pressure variation decreases and its decreasing amplitude declines gradually.With the increase of casing ID,pressure variation increases and its increasing amplitude declines gradually.The study on the annular pressure between double packers can be used as the reference for casing program design,casing strength design,test safety design and safe production.