Research and Application of Fracture Failure Control Technology for 13Cr Tubing in High Temperature and High Pressure Gas Wells

Abstract

There have been many failures happening to S13Cr-110 oil tubing serving in high-temperature and high-pressure gas wells in Tarim Oilfield. A series of investigations were conducted for root-cause analysis, including the macroscopic and microscopic morphology observation of the fracture surface, the service condition evaluation, the quality check of the fractured tubing, and the state analysis of the tubing outer surface. It is concluded that the fracture of the tubing is mechanistically of stress corrosion cracking (SCC), and is closely related to the application of phosphate-based completion fluid. Further tests indicated that S13Cr tubing specimens failed in the form of SCC in the environment of phosphate completion fluid contaminated with mud and oxygen. And formate completion fluid is compatible with super 13Cr tubing. At present, 55 high temperature and high pressure gas wells in Tarim Oilfield have used formate completion fluid, so far there has been no tubing string fracture.