The Paper describes some of the element of petroleum system

1. Faustin Hategekimana
A00015902
PET301 Assignment
American University of Nigeria
Petroleum System and its elements
Definition: Petroleum system is the essential elements and processes as well as all genetically
related hydrocarbons occurring in petroleum shows, seep, and accumulations whose provenance
is a sing pod of active source rocks. I.e. the combination of all processes in which oil or gas is
formed. Those processes and elements are the presence of petroleum mature rock, its migration
pathway, reservoir rock, trap and seal.
Elements of petroleum system
As mentioned in the definition, those are the essential elements of petroleum system:
- Source rock
- Reservoir rock
- Seal rock
- Migration route
- Trap
- Seal
1. Source Rock: It is an organic matter rich which can gradually generate oil and gas
This generation depends on three main factors:
- The presence of organic matter rich enough to generate hydrocarbon
- Adequate temperature
- Sufficient time to bring the source rock into maturity
- Pressure and presence of bacteria and catalyst

2. 2. Reservoir Rock: It is a subsurface body of rocks with sufficient porosity and
permeability to store and transmit fluids.
Most of reservoirs rocks are sedimentary rocks due to their higher porosity and permeability
than other igneous and metamorphic rocks. They are formed also in under temperature and
pressure in which hydrocarbons can be preserved.
3. Migration pathway: It is the movement of hydrocarbons from their source rocks into
reservoir rocks. The movement of new hydrocarbons from their source rocks into
reservoir rocks is called primary migration or expulsion, while further movements are
called secondary migration.
The migration is always taking place from the lower area into the higher area because of the
relative buoyancy of hydrocarbon by comparing it to the surrounding rock. Migration can also
occur locally or at a long distance in large basins.

3. 4. Seal: I t is an impermeable rock that acts as a barrier to further migration of hydrocarbon
liquids. Those rocks are mainly shale, mudstone, anhydride, and salt.
5. Trap: It is the arrangement of rocks suitable for containing hydrocarbon in which that
hydrocarbon will not migrate. Those traps can be structural traps such as folds and faults.
Stratigraphic traps such as rocks having unconformities and other sedimentary features.
Apart from those elements described above, there are some others like temperature, pressure
and time. Temperature and pressure are very important in the making of heavy oils. In a
reservoir, oil and gas are produced from the kerogen in the source rock through a
succession of chemical reactions. These reactions are governed by the usual kinetics
of chemical reactions and hence, the transformation depends primarily on
temperature and time. Pressure appears to be only important as an influence on oil
migration rather than oil formation, although, as we have seen, burial depth is
important to obtain the requisite temperatures.

4. Reference
http://www.landforms.eu/orkney/Geology/Oil/OIL%20petroleum%20system.htm#Petroleum_Sy
stem_
http://www.earthscienceworld.org/images/search/results.html?Keyword=Migration#null
http://www.msnucleus.org/membership/html/jh/earth/petroleum/lesson3/petroleum3a.html
http://www.peeri.org/OV/gas_isotope1.htm
https://cdn-assets.answersingenesis.org/doc/articles/pdf-versions/Origin_of_Oil.pdf