The Saudi oil bombshell by Michael T Klare

Essentially, Simmons' argument boils down to four major points:

Most of Saudi Arabia's oil output is generated by a few giant fields, of which Ghawar - the world's largest - is the most prolific.

These giant fields were first developed 40 to 50 years ago, and have since given up much of their easily extracted petroleum.

To maintain high levels of production in these fields, the Saudis have come to rely increasingly on the use of water injection and other secondary recovery methods to compensate for the drop in natural field pressure.

As time goes on, the ratio of water to oil in these underground fields rises to the point where further oil extraction becomes difficult, if not impossible. To top it all off, there is very little reason to assume that future Saudi exploration will result in the discovery of new fields to replace those now in decline.