The term Reserves means the amounts yet to produce from known discoveries as of the reference date, but the numbers are confused by differing definitions and other distortions (see references). Many published numbers are unreliable. Here, we refer to what are termed "Median Probability Reserves (or P50 Reserves)", which means that the risks that the actual number will turn out higher or lower than the estimate are equally matched. Most published reserves are described as Proved, but are often far from that.
The Middle East (Gulf) has more than half the world's reserves with 439 Gb, followed far behind by Eurasia with 114 Gb, and trailed by Latin America (74 Gb). In terms of individual countries, Saudi Arabia heads the list with 189 Gb, followed by the FSU with 84 Gb. Several other countries with comparable amounts come next in line : Iraq (68 Gb); Abu Dhabi (62 Gb); Kuwait (60 Gb) and Iran (53 Gb). Figure 4 illustrates the wide range in the published estimates.