The petroleum system is becoming accepted as a unifying concept in which various research focused at finding new hydrocarbon reserves can be conducted more efficiently. Proposed definitions of the petroleum system vary, however, the system is basically understood as a group of discovered and/or undiscovered genetically related hydrocarbon accumulations that emanated from a contiguous body of source rocks and that occupy a specific rock volume. The petroleum system map, which shows source rocks and the genetically related accumulations and cross sections which show the stratigraphic position of the accumulations, clearly demonstrate the explorationist's interpretation of the origin and migration route of hydrocarbons.
Three petroleum systems are compared to more graphically demonstrate how the concept is used in exploration, research and resource appraisal. The systems, from most to least explored, occur in northern China in the Jizhong subbasin, in northern Alaska in the Colville basin, and in the Bering sea in the Anadyr basin. Even though the amount of information varies for each basin, the petroleum system can be meaningfully portrayed.
The exploration geologist can use the petroleum system map and cross sections to develop plays to find undiscovered commercial quantities of hydrocarbons within the system, or the system map and cross sections can be used as an analog for another area which contains a little explored system. The research geologist can investigate and model how a system works, either in total or in part, which helps in locating new plays and in decreasing exploration risk. The appraisal geologist can evaluate the petroleum system map from a historical view to study discovery rate process or compare similar systems that have different levels of exploration to determine the ultimate yield of the little explored system.
A conceptual understanding of a petroleum system as a set of oil and/or gas fields occurring in a specific geologic setting and relating to a particular mature source rock is intuitively familiar to most geologists; nevertheless, several attempts have been made to formalize the term in order to make it more applicable to petroleum geology, research and exploration.
Without formally defining the term, Dow (1974) was first to introduce and use ‘oil system’ to explain the relation of mature source rock to oil accumulations.
Perrodon (1983) used the term petroleum system, and later Perrodon and Masse (1984) defined the petroleum system as an organized set of geological events in space and in time that results in the formation of a petroleum province. In Meissner et al. (1984), a hydrocarbon machine (or petroleum system) is a rock seq