The BBC World Service has taken a look at the issue in a four part programme (on the web and in archived streaming audio) – Profit and Loss: The Story of African Oil. It looks at two countries where oil wealth has spectacularly failed to bring prosperity to most of the populations of the countries (Gabon and Nigeria) and two countries hoping to do better with their newfound income – Chad and Sao Tome.
Also see “earlier stuff”:https://blog.org/archives/000864.html on a similar topic (which is not too encouraging).