J55套管的膨胀性能研究

膨胀管技术是21世纪石油钻采行业的核心技术之一，掌握膨胀管在径向膨胀过程中发生永久塑性变形的力学性能变化是膨胀管选材的核心。为此，采用膨胀锥自上而下对J55套管（Φ114.3 mm） 进行了膨胀工艺试验，测定并比较了9.3%的径向膨胀后与膨胀前的力学性能。研究结果揭示了J55套管的膨胀性能：套管的长度减小约4.4%，壁厚减小约6%，不均匀变形程度增加；由于加工硬化，套管的洛氏硬度和抗拉强度增加，而断后伸长率和断面收缩率出现不同程度下降，但均满足API SPEC 5CT标准。断口SEM形貌进一步表明膨胀前后均属于韧性断裂，膨胀后断口上的韧窝小而浅，且分布不均匀，断面较膨胀前的更为平整。该试验成果为膨胀管的材质研究、加工质量控制与工程应用提供了数据支持。

Expansion property of J55 casing

The expandable tubular technology is one of the core technologies in oil drilling and production sector in the 21st century.The essential of the expandable tubular material selection is to know how the change of mechanical performance like the permanent plastic deformation occurs when the expandable tubular is under radial expansion.In view of this,expansion tests were thus conducted on the J55 casing(114.3 mm),which was expanded by an expansion mandrel from top to bottom.The mechanical properties of the casing radially expanded by 9.3% were measured and compared with those before the expansion.The results indicate that the length of J55 casing is decreased by about 4.4%,the wall thickness reduced by 6%,and the degree of inhomogeneous deformation aggravates.Due to the work hardening,the Rockwell hardness and tensile strength of the casing increase,but its elongation and shrinkage on cross section both decrease to different degrees;however,all indexes can meet the requirement of the API SPEC 5CT standard.Furthermore,the SEM fracture surface indicates that the ductile fracturing occurs on J55 casing before and after the expansion.The dimples on the fracture surfaces of expanded J55 casing are small and shallow,and in uneven distribution;the fracture surfaces are smoother than the ones without expansion.This test will provide reference for the selection of expandable tubular materials,quality control in casing manufacturing,and the actual application in fields.