− | Most common is the breakdown of the heavier (C<sub>15+</sub>) fraction into saturated hydrocarbons (saturates), aromatic hydrocarbons (aromatics), lighter nonhydrocarbons (NSOs, polars, or resins), and heavier nonhydrocarbons (asphaltenes). Oils with terrestrial input often have high saturate/aromatic ratios, whereas those from carbonate sources have low saturate/aromatic ratios and high content of nonhydrocarbons. Saturate–aromatic ratios probably increase slightly with increasing maturity and decrease with biodegradation. | + | Most common is the breakdown of the heavier (C<sub>15+</sub>) fraction into saturated hydrocarbons (saturates), aromatic hydrocarbons (aromatics), lighter nonhydrocarbons (NSOs, polars, or resins), and heavier nonhydrocarbons (asphaltenes). Oils with terrestrial input often have high saturate/aromatic ratios, whereas those from carbonate sources have low saturate/aromatic ratios and high content of nonhydrocarbons. Saturate–aromatic ratios probably increase slightly with increasing maturity and decrease with [http://www.oiltracers.com/services/exploration-geochemistry/oil-biodegradation.aspx biodegradation]. |