Failure Analysis of a Sucker Rod from an Oil Well located Offshore Trinidad and Tobago

Nazim Mohamed; Frank  Byron; Clément  Imbert

Authors

Nazim Mohamed
Frank Byron
Clément Imbert

Keywords:

sucker rods, transgranular shear mode failure, Trinidad and Tobago, oil industry

Abstract

Failure analysis was performed on one of several fractured sucker rods that failed at the stress relief length of the pin-shoulder and the thread of the rods during the fit-up alignment and torque assembly of the rod strings and the couplings. Optical microscopy, scanning electron microscopy and microprobe analysis were utilized to characterize the mode(s) of failure and to analyse the fractured surfaces and inclusions. Brittle flat fractured surfaces were observed for more than 80% of the cross section of the rod. Multiple initiation points of failure propagated from the circumference of the rod which contained machine/grinding marks and a multitude of minute cracks. Microstructure close to the surface of the rod showed transverse cracks propagating from inclusions which were analysed to be manganese sulphide. Torsional load applied to the rod during the assembly added to the stress points on the surface. These surface defects then coalesced into one crack front which propagated in a transgranular shear mode of failure. The recommendations included discontinuing the use of the sucker rods and apprising the supplier of the rods of the material and assembly process deficiencies to seek redress.

Author Biographies

Nazim Mohamed

is an Associate Professor at The University of Trinidad and Tobago. He holds a B.Sc. in Applied Chemistry from the University of Portsmouth, England and a Ph.D. in Bioorganic Chemistry from McGill University, Canada. His areas of research include Rheology, Corrosion and Organic Chemistry.

Frank Byron

is a Corrosion Engineer/Metallurgist who holds a Ph.D. Degree from the Process Engineering Department of The University of Trinidad and Tobago (UTT). His research interests include Engineering Metallurgy, Principles and Methodologies of Failure Analysis, Corrosion Studies, Corrosion Prevention and Control Management, Mechanical testing, weld assessments, NDT and in-situ testing.

Clément Imbert

is a Professor Emeritus of The University of the West Indies (UWI). He holds a B.Sc. (Mechanical Engineering) (Hons.) from UWI, M.Sc. (Metallurgical Quality Control) from Brunel University, UK and Ph.D. in Mechanical Metallurgy from UWI, conducted in Canada at Concordia and McGill Universities. His main areas of research are in materials technology, manufacturing processes, inspection and engineering education.