Origin of petroleum

There are two origin for Petroleum, which are:

1 Inorganic

2 Organic

Inorganic Origin:

In late 19th Century, when hydrocarbon first recognized the following proposal put forwarded:

Ø  Alexander von Humboldt, 1804 was the first to propose an inorganic hypothesis, he observed petroleum springs in the Bay of Cumaux (Cumana) on the northeast coast of Venezuela and quoted “petroleum is the product of a distillation from great depth and issues from the primitive rocks beneath which the forces of all volcanic action lie ”.

Ø  Dmitri Mendeleev, a Russian scientist, father of the periodic table, proposed: when mettalic carbide deep within the earth reacted at high temperature to water to form acetylene (C2H2) on condensation form heavier hydrocarbon.

Ø  Abraham Gottlob Werner in the 18th century believed basaltic sills to be solidified oils or bitumen.

Ø  In the mid-19th century. The prolific French chemist Marcelin- Pierre Berthelot described in 1860 experiments where n-alkanes formed during the acid dissolution of steels.

Ø  W. Sokoloff, 1890, proposed a cosmic origin for petroleum, it was precipitated as a rain from original nebular matter, that presently ejected form the earth.

Ø  Russian geochemists proposed that telluric currents deep in the Earth’s crust combine water, graphite, iron and sulfur as a giant battery that were “cooked” into hydrocarbons. V.B. Porfirev (1974) even postulated that all known oilfields were formed in this way during the Neogene.

Ø  Another hypothesis was formulated by T. Gold. In his view, the components of the early atmosphere are still stored in and slowly degassed from the Earth’s mantle, mostly in the wake of earthquakes.

      Objection to inorganic theory:

Ø  Optical rotatory power is a characteristics of Organic Matter

Ø  Petroleum has homologue series of H/C, hardly to be formed by inorganic agencies.

Ø  The lack of association with volcanism, also is a great objection because 8-10% found in igneous and metamorphic and this is due to migration.

Ø  If petroleum were to be cosmic origin then would have been distributed uniformly in earth crust. So relatively the Precambrian/Cambrian rocks contains less petroleum as compared to younger rocks.

2.Organic Origin:

There following are compelling reasons favor the organic origin of Petroelum (and are basis  for Current theory):

Ø  Availability of Carbon and Hydrogen: A vast complex variety of hydrocarbon containing carbon and hydrogen found in the sediments can also be found in remains of animals and plants.

Ø  Presence of Porphyrin Pigments: Many oils found, contains pigment name Porphyrin (C H N ): a pigment formed from red colouring blood (hemin) and green colouring chlorophyll in plants, which is the strong evidence for organic origin.

Ø  Presence of Nitrogen: found in petroleum indicating organic source.

Ø  Optical Activity: Petroleum shows rotation in plane of polarization of the light, which is due to the presence of chelostrol (C26H45OH) and can be found in both vegetable and animal matter                                                                                                                                         

v Characteristic of petroleum:

Ø  Nearly all petroleum occurs in marine sediments, from Precambrian to Pleistocene.

Ø  Petroleum contains complex hydrocarbons, which chiefly composed of 11-15% hydrogen and 82-87% carbon by weight.

Ø  The formation of petroleum is low temperature, anaerobic (reducing environment) phenomena and temperature never exceeds 200 degree Celsius, as indicated by a compound “Porphyrine (C20H12N4)”.

Ø  The fluctuation of condition (P and T) within reservoir is secondary phenomena due to erosion or deformation of area.

Ø  The oil pool indicate that some petroleum has migrated from its place while other has not.

Ø  The time required for the formation and concentration is less than 1 million years.