Silurian, Middle Carboniferous, Middle Jurassic and Sarmatian shales as well as Devonian bituminous limestones are thought to be main the source rocks in the study area. The thermal maturation level of the source rocks was computed using burial history curves for 175 wells. Maps of isoreflectance show that all the source rocks are mature in the north of the study area. The onset of oil generation from most of the source rocks took place during Sarmatian and Pliocene times, after most traps were formed. The calculations suggest that the volumes of hydrocarbons available to be reservoired are much greater than the volumes discovered to date.