Proved oil reserves at the end of 2008 are estimated to have been 1258.0 thousand million (billion) barrels. That represented an increase of 17.7% over the 1997 figure of 1068.5 billion barrels, despite estimated cumulative production of 290 billion barrels during the intervening ten years, ie global reserves additions amounted to around 480 billion barrels between end-1998 and end-2008.
...The reserve numbers published in the BP Statistical Review of World Energy are an estimate of proved reserves, drawn from a variety of official primary sources and data provided by the OPEC Secretariat, Cedigaz, World Oil and the Oil & Gas Journal and an independent estimate of Russian oil reserves based on information in the public domain. Oil reserves include field condensate and natural gas liquids as well as crude oil. They also include an estimate of Canadian oil sands 'under active development' as a proxy for proved reserves. This inclusive approach helps to develop consistency with the oil production numbers published in the Review, which also include these categories of oil. _Source
In fact, proved oil reserves have increased since the beginning of the use of petroleum as an economic resource. One reason for this is that the total amount of hydrocarbon resources distributed throughout the Earth's crust are unknown -- and likely to be far higher than anyone has estimated. Whenever economic conditions require that new exploration should be carried out, new reserves are discovered. In addition, new technologies are constantly developed which convert unproved reserves into proved reserves.
Well over 70% of the Earth's crust remains to be explored for hydrocarbon (including oil, coal, gas, kerogens, bitumens, peats, clathrates, heavy oils, etc etc). The truly giant oil fields may not have been discovered yet. Technology for oil exploration and production is still in the early stage of development, and geologic theory of oil reservoirs is due for radical overhaul.
The oil fields that are being tapped currently are generally only a few hundreds of millions of years old at most. Most of the truly ancient oil fields have been submerged beneath other forms of rock -- besides being under the seafloor -- which are not thought to be fertile ground for oil drilling. The classical theories of oil exploration are suitable for low-hanging fruit. As the old geological theories are subsumed by more realistic approaches, ever new proved reserves of oil will emerge.
It is a race against time, of course. Within 20 years, microbial fuels will be both price competitive and approaching a scale to rival the modern oil industry. BTL, CTL, GTL, BitTL, KerTL, clathrates-to-liquids, etc. will be performed in situ and on-site, using advanced nano-catalytic technologies combined with microbial assist. It will be a new world of energy, but a world with a far lower demand for liquid fuels, as small modular reactors take over the electrical sector.
By. Al Fin