Light Hydrocarbon Geochemistry of Oils in the Alpine Foreland Basin: Impact of Geothermal Fluids on the Petroleum System

Figure 6

Cross-plot of the methylcyclohexane/toluene (Mch/T) ratio versus the cyclohexane/benzene (Ch/B) ratio. Ratios are calculated from chromatographic peak areas. Solubilities (mg/l at 20°C) of different compounds in water are given in brackets. Because aromatic compounds are more soluble in water, water washing results in an increase in Mch/T and Ch/B ratios. The theoretical evaporation trend, assuming simple mixtures of two compounds, is indicated (vapor pressure at 20°C for Mch: 48.3 hPa, Tol: 29.1 hPa, Ch: 104 hPa, B: 100 hPa after [18]). Signature for kerogen type after Schaefer et al. [19]. Note that land plant-rich type III kerogen yields hydrocarbons with high contents of aromatic compounds resulting in very low Mch/T and Ch/B ratios. Dotted line delineates typical Mch/T and Ch/B values from unaltered oils in the Rocky Mountain area [20], Gulf of Mexico (Pleistocene), California (Miocene), Louisiana (Lower Cretaceous [21]), North Slope (Alaska [22]), Mexican Gulf Coast Basin [23], North Central Sinai [24], and SW Barents Sea [25].