XPS analysis of petroleum well tubing adherence

Undesired material adhered to the internal surface of the tubing wall of some petroleum wells is critical for crude oil production. Field samples of steel with petroleum solid adherence were characterized by means of x-ray photoelectron spectroscopy, x-ray diffraction and atomic absorption spectroscopy. The deposit naturally adhered on the steel surface is structurally formed by a thin, black and hard corrosion product layer (inner layer) similar to15 mum thick under a thick, black and brittle organic deposit layer (outer layer) similar to0.01 m thick composed mainly of hydrocarbons. This outer layer contains small amounts of barium sulphate (BaSO4) co-precipitated with organic compounds, which may contribute to the deposit's lack of cohesion. On the contrary, the inner layer of the deposit is firmly adhered to the steel substrate and contains clay minerals and iron compounds embedded in the hydrocarbon layer. Copyright (C) 2003 John Wiley Sons, Ltd.