The Resources of the Earth - Thanatia: The Destiny of the Earth's Mineral Resources - page 153

2500

Mtoe

2000

1500

1000

500

0

North America S. & Cent.

America

Europe & Eurasia Middle East Africa Asia Pacific

Natural Gas: Production Natural Gas: Consumption

Fig. 6.10 Natural gas production and consumption at the end of 2010. Elaborated from data
included in BP (2011)

recovery rates from existing reservoirs and have made profitable the development
of fields previously regarded as uneconomic (Smith and Robinson, 1997). Masters
et al. (1994) estimated that conventional oil reserves had a corresponding range of
additionally recoverable resources between 38 and 141 Gtoe.
Estimates of gas reserves and resources meanwhile are being revised contin-
uously. The International Gas Union (IGU) estimated that additional reserves,
including gas yet to be discovered could be as high as 200 Gtoe (IGU, 1997). Gre-
gory and Rogner (1998) suggested an optimistic estimate for ultimately recoverable
reserves of an additional 500 Gtoe.

6.6.6.3 Non-conventional fossil fuels

Oil that requires extra processing such as that derived from shales, heavy oils, and
oil (tar) sands, is classified as non-conventional. Collectively these types contributed
to around 3% of the world oil production in 2005 (66 Mtoe). A figure which could
reach 110 Mtoe by 2020 (Morse and Glover, 2000) and up to 140 Mtoe by 2030 (IEA,
2005). Resource estimates are uncertain but could be over 830 Gtoe according to
the IPCC (2007b) or even over 1,445 Gtoe following the estimations published in
WEC (2007).
Methane, for instance, stored in a variety of geologically complex, unconven-
tional reservoirs, such as tight gas sands, fractured shales, coal beds, and as methane
clathrates 13 is even more abundant than conventional gas. Indeed global coal bed

13 Methane clathrate is a crystal solid similar to ice, in which methane molecules are trapped in