In recent years oil production from unconventional sources (i.e. tar sands, tight or shale oil) grew, due to increasing oil demand and the decreasing availability of oil from conventional sources.
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Oil Production Through the Years
According to data published by the Energy Information Administration (EIA), global oil production increased steadily until the year 2005. However, after then and up to the present day, the production remained constant, despite an increase in oil demand. This phenomenon is normally referred to as “peak oil.”
The period up to 2005, with production matching demand, is called the “elastic phase”; the following period, with production lower than the demand, is referred to as the “inelastic phase”.
Conventional and Unconventional Sources
We can produce oil from both conventional and unconventional sources.
- Conventional sources are reservoirs whose characteristics (i.e. pressure, porosity and permeability) allow the oil to flow freely.
- Unconventional sources, on the other hand, are those in which the oil does not flow freely, and requires the use of special technologies to be extracted. Consequently, oil produced from unconventional sources is more expensive to produce.
As mentioned above, oil production has remained constant in the last few years. The production from conventional sources, however, dropped by about 5 % per year, due to the decreasing availability of these sources. For unconventional sources, on the contrary, there was an increase in production.
Energy Return on Investment (EROI)
Although the increase of unconventional oil allowed the global production to stay constant, its use had an effect on energy production. Unconventional oil, in fact, has a lower Energy Return on Investment (EROI), as the extraction is more complex and hence more expensive. Basically, more energy is necessary to extract the oil, that in turn will generate energy.
Despite the lower EROI, oil producers are employing unconventional sources more and more, to try to keep up with the increasing oil demand.
Prof. James Murray, from the University of Washington (US), reported on the characteristics of some unconventional sources in an article published in EOS, Transactions of the American Geophysical Union in July 2013. Together with his coworkers, he also analyzes the implications these sources may have on the US and world economies.
This work complements a previous paper he published in 2012 in Nature.
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