Modern Organic Theory:- Petroleum is now believed to be a material resulting from the decay and slow decomposition of marine animals and vegetable matter in prehistoric forests. Changes in earth’s crust had buried this material underground where it had been subjected to intense pressure during the ages. The organic matter ultimately was decomposed either under the influence of radioactive substances or by bacterial agency resulting in the formation of petroleum. This theory explains satisfactorily nearly all the facts about petroleum.
a)   The presence of chlorophyll and haemin in petroleum.
 

b)   The presence of coal deposits near oil fields suggesting its vegetable origin.
 

c)   The presence of nitrogen and sulpur compounds along with optically active compounds in petroleum.
 

d)   The presence of resins also suggests that oil must have been formed from vegetable substances.
 

e)   The presence of helium gas in natural gas suggests that radioactive substances must have helped in the decomposition or organic matter.