historical accuracy - Are the events in Black Gold based on fact?

No, the movie is based on the 1957 novel "South of the Heart: a novel of modern Arabia" by Hans Ruesch.

As far as I could find out the novel is not depicting any actual events or wars. The principalities "Hobeika" and "Salmaah" did not actually exist, and the conflict between them is unlikely to be based on a real one according to this german historical movie site.

The daily life of the people in this region around 1930 are very likely to be historically accurate though.