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→Predicting and recognizing biodegradation
* Biodegradation occurs most rapidly in oil [[accumulation]]s exposed to active meteoric water circulation because the water supplies the oxidants or nutrients.
* Biodegradation occurs most rapidly in oil [[accumulation]]s exposed to active meteoric water circulation because the water supplies the oxidants or nutrients.
* Because biodegradation apparently does not significantly affect asphaltenes and many high-molecular-weight aromatics, severe biodegradation does not destroy the oil entirely.
* Because biodegradation apparently does not significantly affect asphaltenes and many high-molecular-weight aromatics, severe biodegradation does not destroy the oil entirely.
* For aromatic oils, biodegradation results in loss of only 10–20% of the mass of the oil.<ref name=ch11r14>Horstad, I., Larter, S., Mills, N., 1992, A quantitative model of biological petroleum degradation within the Brent Group reservoir in the Gullfaks field, Norwegian North Sea: Organic Geochemistry, vol. 19, nos. 1–3, p. 107–117., 10., 1016/0146-6380(92)90030-2</ref>
* For aromatic oils, biodegradation results in loss of only 10–20% of the mass of the oil.<ref name=ch11r14>Horstad, I., S. Larter, and N. Mills, 1992, A quantitative model of biological petroleum degradation within the Brent Group reservoir in the Gullfaks field, Norwegian North Sea: Organic Geochemistry, vol. 19, nos. 1–3, p. 107–117., 10., 1016/0146-6380(92)90030-2</ref>
* Because many oils have a high fraction of saturate molecules<ref name=ch11r34 /> it is possible that over 50% of the mass of the oil and gas may be removed.
* Because many oils have a high fraction of saturate molecules<ref name=ch11r34 /> it is possible that over 50% of the mass of the oil and gas may be removed.
* Condensates and dry gases are also affected by biodegradation.<ref name=ch11r36>Walters, C., C., 1990, Organic geochemistry of gases and condensates from Block 551A High Island South Addition offshore Texas, Gulf of Mexico, in Schumacher, D., Perkins, B., F., eds., Gulf Coast Oils and Gases—Their Characteristics, Origin, Distribution, and Exploration and Production Significance: Proceedings of the Ninth Annual Research conference, GCS-SEPM, October 1990, p. 185–198.</ref>
* Condensates and dry gases are also affected by biodegradation.<ref name=ch11r36>Walters, C. C., 1990, Organic geochemistry of gases and condensates from Block 551A High Island South Addition offshore Texas, Gulf of Mexico, in D. Schumacher, and B. F. Perkins, eds., Gulf Coast Oils and Gases—Their Characteristics, Origin, Distribution, and Exploration and Production Significance: Proceedings of the Ninth Annual Research conference, GCS-SEPM, October 1990, p. 185–198.</ref>
* Most biodegraded oils are characterized by higher viscosity and lower API gravity than unaltered petroleum, but biodegraded high-wax oils may have lower viscosity.
* Most biodegraded oils are characterized by higher viscosity and lower API gravity than unaltered petroleum, but biodegraded high-wax oils may have lower viscosity.
* Sulfur and nitrogen concentration increases in most biodegraded oils.
* Sulfur and nitrogen concentration increases in most biodegraded oils.