ORIGIN OF OIL AND GAS Inorganic Theories. The followers of the inorganic theory base their statements on the assumption that as hydrocarbons, resembling petroleum, have been produced'in the laboratory by the action of carbonic acid upon alkali metals, that similar reactions,may take place at great depths and that hydrocarbon compounds may be produced by the reaction of water .charged with carbon, dioxide, upon metals and alkalies at high tem perature.
This Carbide theory meets the requirements of the chemist, but the conditions under which oil and gas are actually found have been disregarded. It is possible that carbides exist at great depth, and no doubt heat is also present, but the fact that known pools lie in a zone where no trace of either may be found is against this theory. Rocks forming oil and gas reservoirs show without a doubt that they have never been subjected to great heat. Igneous and metamorphic rocks, which may be the source of the necessary carbides and also permit the presence of the necessary heat, have nowhere been found to contain oil or combustible gas in commercial quantities, although they would be considered as the probable place for the origin of petroleum according to this view. Present oil pools are not found in the existing igneous and metamorphic rocks, but separated from them, sometimes by great thicknesses of fine grained rocks, and the possibility of the oil and gas migrating towards the surface, great distances, through these practically impervious strata, is out of the question.
Another inorganic theory is known as the Cosmic theory, which is based on the finding of small amounts of hydrocarbons in meteorites, but as this theory has no other foundation it may be dismissed without further discussion.
Some hydrocarbons have also been found in connection with volcanic emanations, and a theory based on these findings places the source of the hydrocarbons at great depth, and the present accumulations are claimed to be subsequent infiltrations and impregnations from such depths. The followers of this theory ' point to the fact that gas pressure increases with depth, which is believed to be due to the fact that the source is very deep.
Organic Theory. Although it may be admitted that certain amounts of hydrocarbons may have been formed according to the inorganic theory, the commercial deposits point to entirely different probabilities, with which most oil and gas geologists are in accord. There are several variations of the organic theory, but in each case organic matter is claimed to be the origin of oil and gas. Certain classes claim vegetable matter to be the source of petroleum and gas, while others attempt to show that animal matter is the most probable source, and there are also many who point to the possibility of both animal and vegetable matter being the organic materials from which the hydrocarbons have been formed. Petroleum and natural gas compounds may easily be derived by the destructive distillation of organic matter.
. Decay of vegetation at ordinary temperature gives rise to light, carbureted hydrogen if air is excluded, and the action of bacteria causing organic decay is also admitted.
Geological conditions show that the factors at hand are: water, pressure and time, which combined with the organic remains in the rocks are sufficient to permit the formation of oil and gas. Commercial accumulations that are found are in all cases in accord with this theory.
One of the most important facts bearing on the organic theory has been brought forth by the examination of oils under the petrographic microscope. It has been observed that oils when studied between Nicol• prisms will rotate a ray of polarized light, and it is claimed that only oils derived from organic matter can possess this property. No doubt studies along these lines are of great importance to settle finally the origin of oil and gas so that it may be accepted without further question.
The common conception among oil and gas geologists, with few exceptions is, that oil and gas arc of organic origin, produced under relatively low temperature, high pressure and with the possible assistance of bacteria.