Net Energy Analysis of Gas Production from the Marcellus Shale

Total production of dry natural gas in the USA increased to 24.4 Tcf in 2013, a 35 % increase from 2005 levels. This increase was largely a result of the rapid development of shale resources in the lower 48 states. The Marcellus play alone accounted for nearly 15 % of the total dry gas produced in 2013. In this study, we calculate the energy return on investment (EROI) using a hybrid life-cycle analysis approach bounded by three process stages: (1) EROI P&P , which includes production and processing energetic costs; (2) EROI P,P&T , which considers production, processing, and transportation; and (3) EROI GRID , which includes the energetic costs associated with electricity generation. Most significantly, the inclusion of electricity generation within the EROI analysis makes possible a functional unit comparison to alternative sources of energy into the power grid. Well pad preparation and well drilling had the largest energy costs of all the upstream process stages, accounting for nearly 75 % of production and processing costs. However, the largest energy consumer among the process stages is the cost associated with electricity production, and our model assumes 43 % power plant efficiency, accounting for nearly 94 % of the total energy costs of producing electricity from natural gas. Defined by process stage, our analysis calculated an EROI P&P of 39.7, a EROI P,P&T of 24.9, and an EROI GRID of 10.7. The EROI GRID value of 10 is the same as that calculated for photovoltaic systems, indicating that shale gas, when burned for electricity, provides similar net energy benefits to society as an average PV system.