储气库套管-水泥环-地层的匹配关系

Matching relationship between casing-cement sheath-stratum in gas storages

为了防止储气库井筒内注气增压过程中水泥环本体产生塑性变形,卸载时产生微环隙导致井筒密封失效,运用ABAQUS建立储气库套管-水泥环-地层组合体弹塑性力学模型,模拟储气库井筒内气压变化过程,结合水泥环和地层弹性模量等影响因素分析储气库套管-水泥环-地层之间匹配关系的变化规律。结果表明:以水泥环本体不发生塑性应变为标准,以套管抗内压强度为限制条件,可为不同类型套管匹配最佳的水泥环厚度;当套管尺寸一定时,地层和水泥环弹性模量越小,水泥环厚度越大,套管承压越大,储气库井筒密封失效的可能性越小。

In the process of pressurization by injecting gas in the wellbore of gas storage,the cement sheath suffers plastic deformation.And during unloading,micro-annular is produced,which leads to the seal failure of the wellbore.The elastic plastic mechanics model for casing-cement sheath-stratum system was established using ABAQUS.Then,the change process of the gas pressure in the wellbore was simulated.Finally,combined with elastic modulus of cement sheath and stratum,the change laws of the matching relationship between casing-cement sheath-stratum in gas storages were analyzed.It is indicated that different types of casing can be matched with the optimal cement sheath thickness by taking no plastic strain in the cement sheath as the criterion and the internal pressure strength of the casing as the constraint.What’s more,when the casing size is fixed,the smaller the elastic modulus of stratum and cement sheath,the thicker the cement sheath,the greater the casing pressure and the less possible the wellbore seal failure of gas storage.