Φ139.7 mm×9.17 mm N80 LC套管螺纹黏结原因分析

Analysis of Causes for Thread Gulling Failure of Φ139.7 mm×9.17 mm N80 LC Casing

摘要: 为找出下套管时Φ139.7 mm×9.17 mm N80 LC套管接头发生螺纹黏结的原因，分析该套管的化学成分、力学性能、金相组织，检测3对全新套管的螺纹参数，并进行上卸扣试验，最后分析螺纹黏结形貌。试验结果表明：该套管的材料理化性能及螺纹参数符合API Spec 5CT—2011、API Spec 5B—2008及Q/SY 1572.1—2013标准要求；现场螺纹清洗不当及作业不规范是套管螺纹发生黏结的根本原因。

Abstract: In order to find out the causes for the thread gulling failure of the Φ139.7 mm×9.17 mm N80 LC casing connection as occurred during the casing in hole operation, relevant analysis are conducted involving chemical composition, mechanical properties, and metallographic structure of the failed casing.And the thread parameters of three completely-new casings as coupled are checked, and screw-down test is also made.Finally the thread gulling morphology is analyzed.The test results show that the material physiochemical properties and thread parameters of the casing are up to API Spec 5CT-2011, API Spec 5B-2008 and Q/SY 1572.1-2013.It is identified that the root causes for the thread gulling failure are improper thread cleaning and irregular operation as conducted at site.