Energetic productivity dynamics of global super-giant oilfields

In addition to supplying fuels to society, the oil industry is a globally-significant consumer of energy. Oil sector energetic productivity - measured as output energy per unit of energy consumed - is a major driver of both industry economics and environmental impacts. Increasing climate change concerns necessitate detailed analysis of the energetic productivity of the oil sector. Using an engineering-based life cycle assessment (LCA) approach, we analyze decades-long historical trends of upstream oil production energy return on investment (EROI) for twenty-five globally significant oil fields (41 billion barrels recoverable). The net energy ratio (NER) and external energy ratio (EER) are used as two measures of oil field energetic productivity. We find that as depletion causes declines in oil output, the associated energy returns decline significantly, with some fields seeing NER declines exceeding 90%. This decrease is caused by reservoir exhaustion forcing increased energy costs in recovery and processing. Probabilistic simulation allows us to generalize from our dataset: over 25 years, this model predicts similar to 40% and similar to 20% declines in NER and EER medians, respectively. We also derive a general relationship for projecting evolving NER and EER trends. These results have implications for long-run climate/energy system modeling due to potential large increases in extraction energy as global oilfields age. These effects may result in significant underestimation of future energy demand in the global oil sector in long-run integrated assessment models. Lastly, we perform sensitivity analysis examining implications of model assumptions about electricity provision, flare management, and transport.