CEES
Working Paper Series
#0101 Net Energy From the Extraction of Oil and Gas in the United States, 1954-1997
Cutler J. Cleveland
Center for Energy & Environmental Studies
Boston University |
Introduction
Depletion and technological change exert opposing forces on the cost of
delivering energy to society. One technique for evaluating the costs of
energy systems is net energy analysis, which compares the quantity of energy
delivered to society by an energy system to the energy used directly and
indirectly in the delivery process, a quantity called the energy return
on investment (EROI). Such an investigation involves aggregating different
energy flows. A variety of methods have been proposed, but none has received
universal acceptance. This paper shows that the method of aggregation has
crucial effects on the results of the analysis. It is argued that that economic
approaches such as the index or marginal product method are superior because
they account for differences in quality among fuels. The thermal equivalent
and quality-corrected EROI for petroleum extraction in the U.S. show the
same general pattern: a rise to a maximum in the early 1970s, a sharp decline
throughout the 1970s, a recovery in the 1980s, and then another modest decline
in the 1990s. However, the quality-corrected EROI is consistently much lower
than the thermal equivalent EROI, and it declines faster and to a greater
extent than the thermal-equivalent EROI. The results indicate that quality
corrections have important effects on the results of energy analyses. The
overall decline in the EROI for petroleum extraction in the U.S. suggests
that depletion has raised the energy costs of extraction. This is general
consistent with the overall pattern of oil extraction, i.e., both extraction
and the EROI for extraction show a decline since the early 1970s.