Securing the Supplies of Fossil Fuels - Energy and Climate: How to Achieve a Successful Energy Transition - page 93

sedimentary basins of the planet), if they were exploited with the same
recovery yield, represent a further 140Gt.
Increasing the recovery yield from 35 to 50% (through the use of new
technologies) would make it possible to increase present proven reserves
by 65Gt and resources resulting from future discoveries by 60Gt.
With these assumptions, a total amount of 265Gt (or 1850 billion
barrels), might therefore be added to the present proven oil reserves.
The resources of nonconventional crude oil are huge and amount to
460Gt, but for the time being only a comparatively small share of these
resources may be exploited.
These values can seem reassuring but two important points should
not be forgotten. First, the world consumption rate has considerably
increased during recent years: more oil has been consumed since 1980
(a period of 26 years) than during the whole previous period (more
than a century!). From the supply point of view, the amounts of oil
resulting fromnewdiscoveries do not correspond to the consumption rate
by a long way. Very few giant fields have been discovered in recent years,
whereas presently exploited giant fields deliver half of the total world
production. Thus, the discovery of the four biggest fields each supplying
more than 1 million barrels per year occurred before the 1980s.
Secondly, large uncertainties exist concerning the exact level of proven
reserves. The values which are published depend upon the declarations of
producing countries which may have an interest in overestimating the
level of their reserves.
The uneven geographical distribution of oil reserves creates a geopolit-
ical risk for the security of supplies, which is reinforced by the growing
dependence of consuming countries.
Towards a more technological oil
An oil field can be exploited only during a limited period of time. The pro-
ductionof anoil field starts by increasing, then reaches a productionplateau
and finally declines over a period of time which can be of variable length.
The moment when the maximum of the world oil production might
be reached ('peak oil') is often debated and has been frequently high-
lightedasanimminentriskbyASPO( Association for the Study of Peak
Oil & Gas ).
By considering the evolution curve of the quantity of oil discovered over
the past years, the American geologist KingHubbert was able to show that
production followed the same curve with a time shift of 33 years.