Brockway, P. E., Owen, A., Brand-Correa, L. I., & Hardt, L. (2019). Estimation of global final-stage energy-return-on-investment for fossil fuels with comparison to renewable energy sources. Nature Energy.
The Brockway et al. paper is the primary contemporary measurement of energy return on investment (EROI) at the finished-fuel (rather than well-head) stage. At the finished-fuel stage the global EROI for fossil fuels is about 6 to 1 and declining, approaching what the authors call a net-energy cliff. Earlier well-head measurements had returned much higher figures (Gagnon et al. 2009 report global oil-and-gas EROI for publicly traded companies falling from 30 to 1 in 1995 to about 18 to 1 by 2006). The 2019 paper’s central contribution is that the final-stage measurement is the physically relevant one, since it captures the energy actually available for economic work after processing, refining, and delivery.