Reactions of petroleum compounds with hematite grain-coatings and their effects on diagenesis and pore structure of clastic reservoir rocks

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The aim of this project is the investigation of the interaction of petroleum compounds with hematite coatings on mineral surfaces in reservoir rocks and their effects on porosity (and permeability). Numerous petrological studies have documented typical sequences of diagenetic events in red beds leading to substantial alterations of the pore structure and, in consequence, changes in the poro-perm properties of reservoir rocks. These reaction sequences comprise, as the most conspicuous features, reductive bleaching of certain domains resulting in Fe2+ mobilisation, oil impregnation and formation of enhanced porosity (dissolution of cements and clasts) in neighbouring rock volumes. The concept of the present approach is that oxidation of petroleum compounds by reaction with hematite within reservoirs provides acidic species (e.g. carboxylic acids) which cause further diagenetic reactions resulting in the enhancement of porespace in the vicinity of formerly oil-stained reservoir intervals. The proposed study allows the integration of extensive field evidence, inorganic and organic geochemical laboratory data, and experimental work. Details of this reaction sequence involving organic and mineral matter will be investigated in laboratory tests under elevated temperature and pressure conditions. Specific sampling techniques will be developed to analyse carboxylic acids and other expected organic species generated in this process. Mineral reactions will be monitored by analysis of ionic species in the pore water sampled during the experiment and by comparison of petrographic-mineralogic features of the sample sandstones prior and after experiments.