Petroleum Systems are currently being studies within the general framework of plate tectonics. This new approach has led to the definition of three types of system in the context of the dynamic evolution of sedimentary basins. These three types are "initial rift", "continental platform", and "orogenic-deltaic" Petroleum Systems. The richness and efficiency of a petroliferous basin often depends on an association between two, or perhaps all three, of these types of system. Foreland basins are perhaps the best example. Plate-tectonics theory suggests that a mobile lithosphere is the rule rather than the exception. The transfer of both fluids and materials may occur within a sedimentary basin as a result of horizontal or vertical displacement of the lithosphere. Petroleum Systems therefore appear to be a direct consequence of crustal mobility. When hydrocarbons migrate out of a source rock, they may either be dispersed within another lithological unit and effectively "vanish", be lost by seepage into the atmosphere, or be trapped by some sort of permeability barrier. In the latter case, the resulting hydrocarbon accumulation can be described as a temporary concentration, whose duration essentially depends on the intensity of the incoming fluid flow and the resistance of the permeability barrier (s). The study of a particular Petroleum System within a global geodynamic framework enables the richness (or otherwise) of the oil province in question to be assessed.