Anaerobic oil degradation evolves in the presence of water and pH-buffering/oxidizing minerals. Microbial mediated degradation reactions or hydrolytic disproportionation of light hydrocarbons lead to the formation of methane, carbon dioxide, carboxylic acid and hydrogen. Concurrent mineral dissolution/precipitation and CO2 partial pressures indicate the intensity of oil degradation and coupled inorganic reactions.
Below are modelling examples of our case study about the Gullfaks field (van Berk et al., 2009). The results allow the retracing of measured data and highlight plausibilty of the model.
We apply hydrogeochemical batch modeling (using the PHREEQC computer code; U.S. Geological Survey) to consider oil degradation as controlling factor for