Analysis of the Energy Balance of Shale Gas Development

Interest has rapidly grown in the use of unconventional resources to compensate for depletion of conventional hydrocarbon resources ("easy hydrocarbon") that are produced at relatively low cost from oil and gas fields with large proven reserves. When one wants to ensure the prospects for development of unconventional resources that are potentially vast in terms of their energy potential, it is essential to determine the quality of that energy. Here we consider the development of shale gas, an unconventional energy resource of particularly strong interest of late, through analysis of its energy return on investment (EROI), a key indicator for qualitative assessment of energy resources. We used a Monte Carlo approach for the carbon footprint of U. S. operations in shale gas development to estimate expected ranges of EROI values by incorporating parameter variability. We obtained an EROI of between 13 and 23, with a mean of approximately 17 at the start of the pipeline. When we incorporated all the costs required to bring shale gas to the consumer, the mean value of EROI drops from about 17 at the start of the pipeline to 12 when delivered to the consumer. The shale gas EROI values estimated in the present study are in the initial stage of shale gas exploitation where the quality of that resource may be considerably higher than the mean and thus the careful and continuous investigation of change in EROI is needed, especially as production moves off the initial "sweet spots".