Contribution of organic and mineral compounds to the formation of solid deposits inside petroleum wells

XPS analysis of petroleum well tubing adherence

“…3(b). 5 The XPS spectrum registered the elements C, O, N, S, Si, Fe, Ca, Na, Mg and Al, although not all the spectra are discussed. Figure 4 presents the Fe 2p core-level spectra of the scraped sample, inner layer and sputtered zones, respectively.…”

“…1 -4 However, most of such deposits contain not only heavy petroleum organic compounds but also minerals transported from the reservoir and co-precipitated together with the organic material. 5 A previous SEM study on the naturally adhered deposit morphology indicates that it is roughly constituted by a black, hard corrosion product layer (inner layer) under a black, brittle organic deposit layer (outer layer), as shown schematically in Fig. 1(a).…”

“…This fraction contains calcite, dolomite, aragonite, barium sulphate and sodium chlorite, as indicated by x-ray diffraction (XRD) and FTIR, which is an indication of the reservoir rock origin of these minerals. 5 Morphological and chemical transformations of a metallic surface as a consequence of its exposure to a petroleum environment has been associated with acidic corrosion in the presence of H 2 S and CO 2 gases, therefore iron compounds such as oxidized magnetite, pyrrhotite and iron hydroxides identified by Mössbauer spectroscopy in a previous work in the black inner layer scraped from the steel surface may be related to such phenomena. 6 This black material, naturally preserved under a layer of organic material, shows a low background in an XRD diffractogram when the steel surface is not exposed to the atmosphere.…”

“…1(a). 5,6 Most of the outer layer separates easily from the inner layer. The chemical information obtained by means of Fourier transform infrared spectroscopy (FTIR) indicates an abundance of linear and cyclic hydrocarbons, aromatic rings and carbonyl and amino groups on the inner layer surface.…”

“…The chemical information obtained by means of Fourier transform infrared spectroscopy (FTIR) indicates an abundance of linear and cyclic hydrocarbons, aromatic rings and carbonyl and amino groups on the inner layer surface. 5 Solvent fractionation of the outer layer gave a residue of a toluene-insoluble fraction of 5.55 wt.%. This fraction contains calcite, dolomite, aragonite, barium sulphate and sodium chlorite, as indicated by x-ray diffraction (XRD) and FTIR, which is an indication of the reservoir rock origin of these minerals.…”