The original concept of petroleum system was put forward by an American petroleum geologist Dow in 1972

and then it was supplemented and improved by Porrodon

Demaison

Meissner and others.The petroleum system consists of a effective source rock mass associated with all relative natural hydrocarbon systems and necessary geological elements for oil and gas pools.The petroleum system

together with sedimentary basin

pool-forming assemblage and play

constitute a petroleum investigation series.So the petroleum system does not belong to the category of new theory

but really a new method suitable for oil and gas researches.The object of the research is a petroleum unit of certain origin.The petroleum system could be divided into generation subsystem

migration subsystem and accumulation(preservation)subsystem due to different geological elements and functions.The petroleum systems in China are usually complex systems.When introduce and apply the method of this system

one should neither apply it indiscriminately

nor revise it without considering our own geological condition.