Analysis of Cause for Collapse and Pull-over of 13Cr Tubing Used in a Certain High-pressure Gas Well

Investigated here in the article is the cause for the failure of collapse and pull-over of the 13Cr tubing as used in a certain high-pressure gas well.The cause is identified via the investigation as follows.Although the said tubing is up to the requirements as specified under applicable standard in terms of chemical composition and mechanical property,the tubing is subjected to the stress corrosion in the well,and the stress corrosion crack gets the wall thickness of the tubing reduced,and thus collapse resistance of the tubing is reduced too.And in this case,once formation sand production happens,the tubing is blocked,which makes the external pressure borne by the tubing is greater than the internal pressure,and also gets the difference between the external pressure and the internal pressure exceeds the collapse strength of the tubing’s remaining wall so as to get the collapse inevitably happens, and then follows the pull-over.