Because of the complicated genetic types of gas

accurate identification of the sources of the nature gas has great significance to gas exploration in the Fangzheng Fault Depression.First

the genetic types of natural gas were classified based on the gas components

alkane carbon isotopes and in combination with the actual geological conditions.Then

the thermal maturity of gas was correlated with source rocks in different tectonic units to reveal the gas sources based on identification of organic types and thermal evolution degree. The results show that the gas of this area can be divided into three types.Type A is dry gas and its genetic type is catalytic transitional zone gas generated by lacustrine mudstone in the Xin'ancun-Wuyun Formations.Type B is wet gas and its genetic type is thermal coal-related gas generated by coal measure mudstones.Type C is also wet gas and its genetic type is petroliferous gas generated partly by humic organic ma-tter.It is associated with the oil generated by humic organic matters and is of hybrid sources.Differential structural activity on two sides of Yihantong fault is the main factor leading to the different geochemical characteristics and accumulation patterns of natural gas between the east and west sags.