Oil is the most important source of energy we have, accounting for over 33% of total energy
consumption, more than any other source. The critical nature of oil provokes questions on
how long it can last and what can be done to sustain supply. Production of oil has increased
significantly over the last four decades to meet rising demand. However, the source of this
has evolved - production from conventional oil sources has been gradually declining in recent
years while improved extraction from unconventional sources and increased production by
non OPEC countries have more than compensated for this fall.