Composition Determination of Corrosion Products from Downhole Tubular of a Sour Gas Well Using new XRD and WDXRF Procedures and Configurations

Abstract—Corrosion study and control of downhole tubing and casing are critical for the economical and safe operation of oil and gas wells. Chemical composition investigation of corrosion products plays a key role in the identification of the corrosion mechanism and the determination of its root cause. In this study, the analytical techniques of X-ray diffraction (XRD) and wavelength dispersive X-ray fluorescence (WDXRF) spectrometry were used to determine the chemical composition of corrosion products formed on the pulled-out-of-hole (POOH) flow coupling and full joints of a sour gas well in Saudi Arabia. The samples were in the form of metal cuts and could not be prepared with the routine method for XRD and WDXRF analysis. These unconventional samples were handled using an adapted XRD configuration: X-ray point focus rather than line focus and an open eulerian cradle. With the new setup, XRD phase identification and quantification were successfully performed. It was found that the outer diameter surface of the pulled flow coupling and full joints consisted mainly of iron oxides whereas the inner diameter surface consisted mainly of iron sulfides. The XRD findings were further confirmed by WDXRF analysis. The findings suggested that the corrosion products were formed under different conditions.