页岩气井生产套管变形分析及选材建议

Casing deformation analysis and material suggestion for production casing in shale gas well

压裂过程中,四川区域页岩气井的生产套管出现了大量的变形损坏,严重影响生产。统计发现套管变形主要位于入靶点附近和水平段,且以管体缩径和剪切变形为主。基于不同变形处的套管受力特征,结合实物试验和理论计算,研究不同壁厚、钢级、轴向拉力和弯曲度下的抗挤强度变化规律。结果表明,随轴向拉力的增大,抗挤强度减小;同一轴向拉力下,随弯曲度增大,抗挤强度减小。从选材角度,提高壁厚和屈服强度均可以提高抗外挤强度,降低套管变形率。实际应用中,应综合考虑施工等条件,确定合适的方式。

During fracturing,there has been a lot of production casing deformation in shale gas well,Sichuan,which severely affects production. The statistical analysis reveals that the casing formation has located near target points and horizontal section,mainly with the form of the casing drawing down and shear defromation. Based on the mechanics characteristic of the different casing deformation positions,combined with full scale test and theoretical calculation,the anti-collapse strength changing rule with the different wall thickness,steel grade,axial tension and dogleg angle are studied. The results show that the anti-collapse strength decreases with the increase of axial tension; Under the condition of the same axial tension,the anti-collapse strength decreases with the increase of dogleg angle. Form the view of material selection,in order to decrease the casing deformation ratio,there are two methods to increase the anti-collapse strength with the methods of increasing wall thickness and yield strength. However,in practical application,the appropriate method can be selected based on the comprehensive consideration of construction conditions.