中文摘要：

在深水测试过程中，测试管柱下入井后其受力和变形无法观测，密封插管长度的不合理设置会造成封隔器密封失效及井下管柱永久变形等严重事故。为保障深水测试作业安全高效实施，对深水井下管柱轴向变形原理和规律进行研究，形成密封插管安全长度确定方法，并以我国南海某深水井为对象进行实例分析。计算结果表明，不同作业工况下测试管柱轴向变形相差较大，开井作业测试管柱的伸长量随着测试产量的增加而增加，温度和压力是深水井下测试管柱轴向变形的主要影响因素；建议选择关井后密封插管相对开井作业的上移距离为密封插管安全长度的参考值，考虑井底温度和压力预测结果的可靠性，实例井需选用长度至少为2．29m的密封插管。

英文摘要：

After the test string runs in hole absolutely during the deepwater testing, its force and deformation are unobserved. If the length of seal intubation is not reasonable, serious accidents may happen, such as the seal failure of packer and permanent deformation of downhole string. In order to ensure the security and efficiency of deepwater testing, the principles and rules of axial deformation for deepwater downhole string are studied based on the features of deepwater testing technology and devices. Accordingly, a method to determine the safe length of seal intubation is established. This method was applied to a deepwater well in the South China Sea. The calculation re- sults show that the axial deformation of test string is different depending on operation modes. The axial deformation of downhole string increases with the increase of test production in the flowing test mode. The temperature and pres- sure are the main factors for axial deformation of test string. The displacement of test string between shut-in well mode and flowing test mode is suggested as the reference value of safe length for seal intubation. Considering the re- liability of the prediction of bottomhole temperature and pressure, the recommended value of calculation example is 2.29 m based on the proposed theory and method.