Charakterisierung sorbierter Ölkomponenten auf Tonmineralien und Quarzkörnern in Ölsanden : ein Beitrag zur Benetzbarkeit von Reservoirgesteinen in Öllagerstätten

The wettability of an oil reservoir strongly influences the recovery rate during primary production and the feasibility of Enhanced Oil Recovery. In order to achieve an insight into the chemical nature of the oil components sorbed onto mineral surfaces, unconsolidated Canadian (Athabasca, Cold Lake) and U. S. oilsands (Tar Sand Triangle) were exhaustively extracted with dichloromethane by Soxhlet to remove the non-sorbed, so called free oil. The oils of these reservoirs are strongly altered by degradation (biodegradation and water washing). After the extraction between 0.8 - 4 wt% TOC still remained onto the clays (grainsize fraction 63 $\mu$m). The sorbed oil on the clays were investigated in situ by spectroscopy and pyrolysis. Clays and quartz were extensively extracted with polar solvent mixtures to release the sorbed oil. The extractable sorbed oil and the corresponding free oil were fractionated inchemically defined compound classes by adsorption chromatography. The fractions were characterized by means of GC, GC/MS and IR-spectroscopy. The sorbed oil is highly enriched in oxygen functions bearing components, which partly show a polyfunctional character. The sorbed oil is quantitatively and qualitatively different from the free oil. Qualitative differences could be shown by analyses of single components (e. g. carboxylic acids and alcohols). The surprising existence of n-alkanes in the sorbed oil, which are not detected in the free oil, is explained by occlusion in the sorbed organic layer. The existence of sterols could be shown in the free and the sorbed oil though not being reported in literature to date. Clays and quartz show a different behavior of sorption. Opposite to the general accepted idea, of smectites showing the highest capacity to sorb organics, the highest amount of sorbed oil was found in the kaolinite-/illite-rich samples. Different mechanisms of oil sorption onto the mineral surfaces, possibly driven by entropy, are discussed