Multiple Controls on Petroleum Biodegradation and Impact on Oil Quality

摘要: Biodegradation of oils in nature is important reservoirs cooler than approximately 80°C. Oils from shallower, tend to be progressively more biodegraded those deeper, hotter reservoirs. Increasing levels biodegradation generally cause a decline oil quality, diminishing the producibility and value as API gravity distillate yields decrease; addition, viscosity, sulfur, asphaltene, metals, vacuum residua, total acid numbers increase. For specific hydrocarbon system (similar source type level maturity), general trends exist for oil-quality parameters vs. present-day reservoir temperatures <80°C. However, other controls on may also have significant effects, making predrill prediction quality difficult some areas. It has long been observed that fresh, oxygenated waters contact with can extensive aerobic biodegradation. More recently, it recognized anaerobic sulfatereducing fermenting bacteria degrade petroleum. Highly saline formation inhibit bacterial degradation effectively shield deterioration. The timing charge(s) post-charge temperature history major effects quality. Reservoirs undergoing current charging hydrocarbons overwhelm ability oil, resulting better-than-anticipated Fresh charge containing previously degraded will upgrade Calibrated methods risking, based detailed evaluation local biodegradation, need developed play prospect basis.