Petroleum system case studies provide an important link in understanding the petroleum system concept. Petroleum system case studies from different petroleum provinces of the world demonstrate practical problems that are typical of a petroleum system investigation. Well-documented case studies provide not only an understanding of the present-day distribution of hydrocarbons but also the basis to evaluate petroleum exploration risk in a play or prospect and to carryout petroleum research effectively.

The case studies in the next two units describe and characterize 25 petroleum systems. Some studies address the migration of hydrocarbons from the pod of active source rock to the trap and show the difficulty of determining not only the hydrocarbon migration path but also the loss of petroleum during migration. The case studies also address generation-accumulation efficiency and size so that conclusions can be drawn as to what essential elements and processes most affect efficiency and size. This overview shows that the most prolific petroleum system is not necessarily the most efficient. By comparing several petroleum systems on either an efficiency or size scale and then comparing the essential elements and processes of each system, a general impression is gained of how each system functions.