Abstract. In this work, we have investigated the wettability of Bazhenov Formation rock samples using a nuclear magnetic resonance (NMR), the methods of vapor adsorption, and wetting contact angle. We have conducted the petrographic description of rocks using ultra-thin sections and scanning electron microscopy (SEM). In addition, we used data on the organic content (TOC) obtained by the Rock-Eval method and the results of lithological typing on thin sections for detailed analysis of NMR and contact angle methods results. Thus, for target rock, the groups with a similar rock wettability were highlighted by the lithological description of thin sections. The calculation of the wetting angle provided an initial assessment of the surface wettability of the rock and made it possible to establish the relationship between the wetting angle and the TOC, which is relevant for rocks of the Abalak-Bazhenov group. The NMR method described the core plug wettability proved to be less sensitive to the rock lithotype and organic matter (OM) texture in the rock and, therefore, used for the integral characterization of core plugs. Correlations of calculated wetting angle and adsorption wettability index vs. TOC and OM texture illustrated the dependence of rock wettability behavior on both the lithological
specifics and the OM properties.
By data of laboratory studies of mineral composition, analytical estimation of hydrophobicity of rocks by adsorption and NMR methods, pyrolytic studies of organic matter of Bazhenov Formation rocks, dependencies were determined between organo-mineral matrix composition and wettability of the solid surface. Influence of secondary effects on changes in hydrophobization of rocks were revealed. For carbonate minerals, catagenetic substitution of calcium cations for magnesium and iron results in polar changes in attitude of the rock to water fluids. Evaluation was made of the proportion of generated autochthonous and parautochthonous hydrocarbons of the oil series, heteroatomic compounds and kerogen in the overall balance of the organic component of the Bazhenov rocks, and an attempt was made to establish dependency of these proportions versus measured hydrophobicity of rocks. After dissolution of the light fraction of petroleum hydrocarbons, a decrease in combustion rate of the residual organic matter in air flow was observed for hydrophobic varieties. There are no obvious dependencies of surface hydrophobization versus mineral composition and organic matter of a rock in the ‘rock-water-oil’ system.
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