Experiments to Reactions of Organic Compounds with Hematitic Reservoir Rocks

Angela Meier¹, Reinhard Gaupp¹, Bernhard M. Krooss², Ralf Littke², Bernd Ondruschka³, Peter Scholz³, and Doerte Stachel^4
1Institute of Earth Sciences, Friedrich-Schiller-University, Jena, Germany
²Institute of Geology and Geochemistry of Petroleum and Coal, RWTH Aachen University, Aachen, Germany
³Institute of Chemical Engineering and Environmental Chemistry, Friedrich-Schiller-University, Jena, Germany
⁴Otto-Schott-Institute of Glass Chemistry, Friedrich-Schiller-University, Jena, Germany

Within the scope of this project, we investigate the interaction of petroleum compounds with hematite grain-coatings on mineral surfaces and their effects on porosity, permeability and pore structure of clastic reservoir rocks. We evaluate the hypothesis that liquid hydrocarbons in hematitic reservoirs can generate reactive organic acids and/or carbon dioxide during post-emplacement thermal evolution. The results can allow a better understanding of mechanisms of reductive bleaching and porosity enhancement in red sandstones by the presence of liquid hydrocarbons.

Flow cell experiments were designed with red bed sandstones from the Upper Rotliegend from the North German Basin (Germany) under elevated temperature and pressure conditions and different reactant fluids. The water-wet sandstone samples and fluids are characterised prior and after experiments. Initial short-term experiments started with deionised water. Mineral reactions are monitored by analysis of the ionic species in the post experimental fluids by ICP-MS/-OES and titration methods. They showed a significant concentration of silicon, calcium, potassium, aluminium and carbonate species. Further short- and long-term experiments were accomplished with organic fluids consisting of a mixture of n-alkanes in the range of C6 to C10 and a long-chain n-alkane (C16). In case of the n-alkane mixture with short-chain hydrocarbons no changes are identified.

Experiments with hexadecane showed a significant reduction of the red bed sandstone samples and oxidation of the organic molecules. Comparisons of mineral surface geometries in different resolutions by Scanning Electron Microscopy (SEM), Vertical Scanning Interferometry (VSI) and Atomic Force Microscopy (AFM) prior and after the experiments indicate changes which are caused by reactions with organic reactants.

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