A dynamic model for liquid fossil fuel production based on gross product/EROI coupling
Résumé
Since 1940, many attempts to model world oil production have been proposed. These approaches, using increasing complexity, consider the growing and decay of production independently of external, time-varying, causes. It is here proposed to extend the production equation by modelling a dynamic dependency between oil production and its Energy Return On energy Invested (EROI). The model is based on mass and energy conservation and can be applied to all extracted liquid fossil fuels. After comparison with oil extraction and EROI dynamics, it highlights the existence of an external, controlling parameter: the investment rate, which account for the re-investment in newly operated liquid fuel sources. The dynamic of this parameter provides some possible explanations about the progress of the oil shocks and also some possible explanations about the peak prediction issues of the classical Hubbert model. Studying this evolution also suggests an attempt to control the fossil liquid fuel production in order to sustain a globally linear production, starting around 1943: at short time scale (shorter than 30-36 years), the investment rate evolved linearly. However, in order to keep a linearly growing production at long time scale, the investment rate had to evolve exponentially: this was achieved through a piecewize linear control, where the investment rate and its derivative doubled every 30-36 years.
The model also allows to highlight a major issue in liquid fossil fuel production: even if the gross product can be controlled and keeps growing linearly, the net product, which account for the energy delivered by the oil industry to the consumer, can decrease before the gross product peaks, due to the decay of EROI. At this point, the energy benefit of the oil industry will inevitably decrease and fossil liquid fuel production will slow down. Based on the present model and a sensibility study on its parameters, this tipping point will happen between 2032 and 2039. Net product of fossil liquid fuels could therefore keep growing linearly until this point, where a steep decay is expected. Hence production will be strongly asymmetric regarding the peak, contrary to the prediction suggested by Hubbert’s model.
Domaines
Milieux et Changements globauxOrigine | Fichiers produits par l'(les) auteur(s) |
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