Research on the compositions

carbon isotope

and geochemical properties of light hydrocarbons of natural gases in Gubei buried-hills of Jiyang depression suggests that gases there are of three genetic types: oil-related gas

coal-related gas

and mixed gas.Natural gases in Well Bo-601 and Boshen-6 belong to oil-related gas

that in Well Yi-155 and Gubeigu-1 are coal-related gas

and that from Well Gubeigu-2

Bogu-4

and Yi-32 belong to mixed type.Study in combination with the geologic characteristics reveal that the carbon isotope and light hydrocarbon show certain regularities in the study area.From the first row to the fourth row of buried-hills(from west to east)

the carbon isotope become progressively heavier

the values of indexes of methylcyclohexane and benzene gradually increase

and the genetic types of natural gases shift from oil-related gas to coal formed gas.It is suggested that the distribution of natural gases in the area are obviously controlled by the gas source rocks and faults in the study area.Oil-related gas is mainly concentrated in the first row of buried-hills

mixed gas is predominantly distributed in the region near the Gubei fault in southern part of the second and the third row of buried-hills

while coal-related gas is preserved in the northern part(regions far away from the Gubei fault)of the second and the third rows of buried-hills

and the fourth row of buried hills.