Petroleum system

	Exploring for Oil and Gas Traps
Series	Treatise in Petroleum Geology
Part	Traps, trap types, and the petroleum system
Chapter	Petroleum systems
Author	Leslie B. Magoon, Edward A. Beaumont
Link	Web page
Store	AAPG Store

The first step in petroleum system analysis is petroleum system definition. This section discusses what the concept of a petroleum system is; how to identify and name a system; how the components relate geographically, stratigraphically, and temporally; and how to map a petroleum system.

The petroleum system is a unifying concept that encompasses all of the disparate elements and processes of petroleum geology. Practical application of petroleum systems can be used in exploration, resource evaluation, and research. This chapter discusses its application to petroleum exploration.

What is a petroleum system?

A petroleum system encompasses a pod of active source rock and all genetically related oil and gas accumulations. It includes all the geologic elements and processes that are essential if an oil and gas accumulation is to exist.

Petroleum describes a compound that includes high concentrations of any of the following substances:

Thermal and biological hydrocarbon gas found in conventional reservoirs as well as in gas hydrates, tight reservoirs, fractured shale, and coal
Condensates
Crude oils
Natural bitumen in reservoirs, generally in siliciclastic and carbonate rocks

System describes the interdependent elements and processes that form the functional unit that creates hydrocarbon accumulations.

Elements and processes

The essential elements of a petroleum system include the following:

Source rock
Reservoir rock
Seal rock
Overburden rock

Petroleum systems have two processes:

Trap formation
Generation–expulsion–migration–accumulation of hydrocarbons

These essential elements and processes must be correctly placed in time and space so that organic matter included in a source rock can be converted into a petroleum accumulation. A petroleum system exists wherever all these essential elements and processes are known to occur or are thought to have a reasonable chance or probability to occur.