套管钻井中套管屈曲变形的有限元分析

针对套管钻井过程中套管易发生屈曲变形问题,进行了有限元分析。结果认为当钻压为117.68kN,井斜角逐渐增大时,井斜平面内的套管屈曲变形逐渐趋于正弦曲线,并且由于重力的侧向分力增大,套管与井壁接触的压力和区域增加,加剧了套管磨损。当井斜角为3°,钻压较小时套管基本上平躺在下井壁,钻压增大时套管与井壁的环空间隙小,限制了套管的屈曲变形,但接触力的增大也使套管磨损加剧。解决套管磨损的方法有2种一是在管柱底部连接厚壁套管;二是在套管柱上安装刚性扶正器。

Finite element analysis of casing buckling in casing drilling

The casing buckling is analyzed with FEM in casing drilling. The analysis result shows that: when the bit load is 117.68 kN and the deviation angle increases,the casing buckling on the hole deviation plane tends to be a sinusoid,and the increase of the side force component of the gravity results in more serious wear of the casing since the contacting pressure and contacting range between the casing and borehole are increased. When the deviation angle is 3?and the bit load is rather small,the casing is generally laid horizontally on the borehole wall; while the bit load increases,the casing buckling is constrained,but the increase of the contacting force causes the more serious casing wear. There are two ways to solving the problem of casing wear: one is to connecting thick-walled casing at the string bottom,and the other is to install rigid stabilizer on the casing string.