The location of the burial history chart is along the cross section line within the pod of active source rock (Fig. 2B, E). At this location, the source rock must be thermally mature (active or spent) otherwise petroleum would be absent in the conduits or migration paths. The reconstruction of the burial history provides the basis for the times of the onset (O) of generation-migration-accumulation, the depletion (D) of the source rock, and the critical moment (CM).
The table showing all the oil and gas accumulations included in the folio sheet provides important information about the petroleum system (Fig. 2C; Table I). First, the discovery dates and sizes of the fields are useful for field-size distributions and discovery-rate modeling. Second, the complexity of the hydrocarbon plumbing system is suggested by the number of reservoir rocks. One reservoir rock for all fields indicates a simple plumbing system, whereas many reservoir rocks indicates a more complicated system. Third, the size of the petroleum system and the generation and expulsion efficiency can be determined by using the total volume of recoverable oil and gas for all fields. Finally, the reservoir rock with the highest percentage of oil or gas reserves is to be used in the petroleum system name. For example, if all the oil is in the Boar Sandstone, it is included in the name (Fig. 2D).
For example, the Deer-Boar(.) is a 1.2 billion barrel petroleum system with a simple plumbing system. This size designation using recoverable petroleum is most useful to the explorationist who is interested in (1) comparing the sizes of different petroleum systems to rank or plan an exploration program and (2) comparing the field-sizes in a petroleum system to determine the most likely prospect size and what volumes can be produced. However, the size (volume of recoverable petroleum) of the petroleum system needed for material balance equations is quite different. Here, three additional types of information are estimated: the inplace petroleum for each field, what is left behind along the migration path, and what was lost in surface seeps and exhumed accumulations. These estimates are made by the investigator. This volume of petroleum can then be compared to the estimated volume of petroleum generated in the active source rock.
