Although there are more than 40,000 oil and gas fields of all sizes in the world, slightly less than 80 percent of the proven reserves are concentrated in eight countries, of which only Canada and Russia are not OPEC members.
By Dave Brown - Exclusive to Oil Investing NewsCountless pockets of oil reserves exist on earth and natural seeps of crude oil are not especially rare on the earth's surface; however the oil leaking from the ground is usually a highly degraded substance, close to tar. There are more than 40,000 oil and gas fields of all sizes in the world, but 94 percent of known oil is concentrated in fewer than 1500 giant and major fields. The largest of these fields are located in Siberia and the Middle East. The Canadian Athabasca deposit is the only large oil sands reservoir in the world that is suitable for large-scale surface mining, although most of it can only be produced using more recently developed in-situ technology. Slightly less than 80 percent of the proven reserves are concentrated in eight countries, of which only Canada and Russia are not OPEC (Organization of Petroleum Exporting Countries) members. The top ten countries with proven reserves are as follows: Saudi Arabia, Canada, Iran, Iraq, Kuwait, Venezuela, United Arab Emirates, Russia, Libya and Nigeria. There remains some skepticism about the reliability of OPEC official reserves estimates, which are not provided with any form of verification or audit that meet external reporting standards. Geological Requirements There are four requirements necessary to form an oil deposit: 1) there must be a source rock, 2) there must be a heating event, 3) there must be a reservoir rock, and 4) there must be a trapping mechanism. The source rock must contain abundant organic matter. The best source rocks are organic-rich shales, limestones and sandstones that contain 0.5 % to 5 % organic matter. The organic material liquefies during the heating event, converting to hydrocarbons in the process. Oil deposits are generally formed in relatively younger rock formations, especially those that have not undergone metamorphic processes. Heating is required to form oil, but if too much occurred (such as during a metamorphic event), the majority of the petroleum has escaped.