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摘要
The objective of the work is to develop a conceptual model (BioClass) for predicting both the biodegradation level and the corresponding chemical changes (FR. Patents No. 2.934.605 and No. 2.934.606). This model comprises two parts: a 0D compositional and quantitative simulator and the dynamic coupling of this 0D simulator with a basin model that considers the petroleum system history (e.g., time, temperature, fluid dynamics). The 0D model computes the hydrocarbon losses from the different chemical classes. It is based on four global stoichiometric equations that describe hydrocarbon biodegradation under aerobic, denitrifying, sulfate reducing and methanogenic conditions. These equations are applied on model compounds representing the main chemical classes of oils: C(6)-C(14) saturates. C(6)-C(14) aromatics, C(14+) n + iso-alkanes. C(14+) cycloalkanes and C(14+) aromatics. Each chemical class is defined by a relative biodegradation coefficient (K(bio)), which takes into account both the accessibility of the hydrocarbons to microbes and their intrinsic susceptibility to biodegradation. These coefficients were first optimised using a natural series of biodegraded oils from the Potiguar Basin (Brasil). The estimated total hydrocarbon loss (58-73%) was in excellent agreement with that from literature using metal concentration, such as Ni (Magnier et al., 2001). Then, BioClass 0D was applied successfully to a series of oil samples from the Williston Basin (Canada) for which the predicted loss ranged from 11-54%. This validated the basic concepts of the model to predict oil composition changes during biodegradation and the resulting hydrocarbon losses. Consequently, BioClass 0D provides a new biodegradation ranking based on the determination of the total hydrocarbon loss calculated from the residual oil composition. In parallel, BioClass 0D, which is totally independent of any geological parameter, will be coupled to transport of the oil and water in a basin simulator in order to predict the biodegradation rates of different chemical classes in oil samples. It will integrate critical factors that control hydrocarbon biodegradation, such as residence time and temperature.
- 出版日期2010-10
