Petroleum/Crude oil is a thick liquid consisting of hundreds of combustible hydrocarbons with some sulfur, oxygen, and nitrogen. It is found in the following countries and continents: Saudi Arabia (26%), Iraq, Iran, Kuwait, United Arab Emirates (9-10 each), Venezuela & Mexico (9), Africa (7), Russia (6), Asia (4, 3 in China), US (3), Western Europe (2). Identified global reserves could last 53 years at the current consumption rate, and 42 years if the usage rate increases by 2% per year. Undiscovered oil might add an extra 20-40 years to the identified sources.

It is found in the following countries and continents: Saudi Arabia (26%), Iraq, Iran, Kuwait, United Arab Emirates (9-10 each), Venezuela & Mexico (9), Africa (7), Russia (6), Asia (4, 3 in China), US (3), Western Europe (2).

The advantages of using oil as an energy source are:
1) The ample supply for 42-93 years
2) Low cost (with huge subsidies)
3) High net energy yield
4) Easily transported within and between countries
5) Low land use
6) Technology is well developed
7) Efficient distribution system.

The advantages of using oil extracted from oil shale and tar sands are: 1) moderate existing supplies, 2) large potential, 3) easily transported within and between countries, and 4) efficient distribution system in place.

Oil also produces other products such as gases (like NG), gasoline, aviation fuel, heating oil, diesel oil, naphtha, grease, wax, and asphalt through the refining process.