ASPHALTENE ADSORPTION ON CLAYS AND CRUDE-OIL RESERVOIR ROCKS

The adsorption of asphaltene on different clay minerals (kaolinite, il lite, montmorillonite) and mineral oil reservoir rocks was studied. In toluene solution, specific adsorption was observed on kaolinite and a decrease in adsorption was found in the order illite-montmorillonite. In toluene/n-heptane mixtures a two-stage isotherm was recorded on th e surface of the adsorbents. Surface modification by the adsorption of asphaltenes was characterized by a variety of structure-probing metho ds such as N-2-adsorption, X-ray diffraction (XRD), small-angle X-ray scattering (SAXS) measurements, and FTIR spectroscopy. The hydrophobiz ing effect of asphaltene on clays was also checked by immersion microc alorimetry. According to XRD studies, no intercalation of asphaltene o ccurs in toluene and toluene/n-heptane mixture on montmorillonites. SA XS scattering curves measured on kaolinite samples deviate from each o ther in the angle range close to primary scattering, because of the pr eferential adsorption of asphaltene. The aggregation of clays by aspha ltene also manifests itself in a decrease of specific surface areas de termined by N-2-adsorption. (C) 1998 Elsevier Science B.V.