Hydrocarbon Alteration - A Case Study from the Vienna Basin

The discovery of oil and gas, some 150 years ago, has triggered an intensive and extensive hydrocarbon exploration in the Vienna Basin. In the present study biomarker data from oils and potential source rocks are used for oil-source rock correlations. Furthermore, in combination with element concentrations in-situ hydrocarbon alteration is characterized. Biomarker data was acquired using GC/FID and GC/MS approach and element concentration was acquired using the triple quadruple ICP-MS approach. Oil-source and oil-oil correlation reveal that all oils are generated from a single source (Mikulov Marl). Oils from shallow Miocene reservoirs have been affected by biodegradation, whereas oils from deep carbonate reservoirs suffered from Thermochemical Sulfate Reduction (TSR). The degree of biodegradation has been quantified using the Biomarker Biodegradation Scale, which is strongly correlated with API gravity, sulfur and nickel concentrations. TSR resulted in high H2S concentrations, a minor, but distinct increase in sulfur in the aromatic fraction, but no increase in total sulfur concentrations.