Deposition of petroleum heavy organic compounds on a low carbon steel tubing

Reduction of petroleum wells production is often observed and related to the presence of solid deposits adhered on the internal wall of the tubing. A piece of tubing with organic material adhered on its surface was recovered from a Mexican southeastern region well. Its composition and morphology was studied applying scanning electron microscopy with X-ray energy dispersion spectroscopy (SEM-EDXS), X-ray diffraction (XRD) and reflection Fourier Transform Infrared Spectroscopy (FT-IRS). High-condensed hydrocarbons with hydroxyl and carboxyl functional groups and 6.4 wt% total sulfur were found. The adhered-material morphology suggests vitreous solid structure usually identified in polycyclic aromatic compounds. Iron (II, III) oxides and nonstoichiometric sulfides are present; the last, as a corrosion product obtained in petroleum with low H₂S concentration. Pyrrhotite (Fe_1-x S), which exhibits a nonstoichiometric structure, was reported as the active phase of iron oxide catalysts in hydrogen interchange processes.