套管试压对固井第一界面水力密封失效的影响

Research on Effect of Casing Pressure Test to Cement-Casing Interface Hydraulic Sealing Property

过高的套管试压将引起水泥环应力破坏,导致水泥环丧失密封性能。从研究套管试压对全井固井第一界面的影响角度出发,根据弹性力学理论,开发了第一界面剪应力分布拟三维有限元数值计算程序,并以LG-11井为例分析了套管试压引起的第一界面水力密封失效机理。计算结果表明:套管高压将导致油气井井口部分区域第一界面出现滑脱,对井底第一界面基本没有影响;随着试压压力增大,滑脱区域逐渐增大。计算结果与LG-11井试压前后测井解释结果一致。

Extra high pressure of casing pressure test aggravates the sealing property of cement sheath by stress damage.To study the effect of casing pressure test on the full cement-casing interface,a P3D FEM calculator program of the shear stress of cement-casing interface is developed based on elastic mechanic theory.The mechanism of fail sealing of the cement-casing interface caused by casing pressure test is analyzed through the well LG-1 l.The results show that,high casing pressure leads the cement-casing interface in wellhead decollement,but no effect on the bottom.Also the decollement section is enlarged by higher test pressure.The result of calculation is consistent with well log interpretation in well LG-I 1.