The contents of mercury(Hg) in natural gases can vary from less than 1 to n×10

3

μm/m

3

.The main affecting factors are the types of the parent matter

the tectonic background and deep geological process.The content of Hg in coal type gas generated from typeⅢorganic matter is relatively higher.On the contrary

that of oil type gas generated from type Ⅰto Ⅱorganic matter is relatively lower.So the concentration of Hg in natural gas is regarded as geochemical index in determining the source rock of the gas.Research result shows that the concentration of Hg in natural gas is affectde by tectonic movement of basins and deep geological process.The contents of Hg in the natural gases from tensile active basins located in East China is relatively higher;that of natural gases from stable basins in Central China is relatively lower;that of natural gases from sub stale basins in Northwest China is between the above mentioned two.This variation of Hg contents in oil type gas is particularly considerable.The Hg contents in natural gas bear positive correlation with the

3

He/

4

He ratio

indicating that Hg may be partly originated from deep earth degassing or be affected by deep geological action.