Statistical measurements of 103 gas samples from the Tarim Basin indicate that the oil-type gas and the coal-derived gas dominate the basin and that the former contains much more nitrogen than that of the latter.The gas with abnormal high concentration of nitrogen(more than 20%) occurs in the Paleozoic gas reservoirs of Tazhong

Donghetang

and Hade regions

and the Mesozoic gas reservoirs of Lunnan region(in the Paleozoic craton area).The gas with the lowest N

2

content(N

2

<

5%) are mainly coal-derived and are distributed in the Cenozoic strata of the basin and the Mesozoic strata of southwestern Tarim and Kuqa depressions.In the Tabei area

the N2 contents in natural gas are considerably varied.Gases with low nitrogen concentration are mostly coal-derived;while those with high nitrogen concentration are often oil-type gas

in which the origins and contents of nitrogen are changed with the different thermal stages of sapropelic source rocks.The nitrogen molecular in Yakela gas may be explained by the mixture of organic nitrogen formed by sapropel-type kerogen during over-mature stages and a little amount of inorganic nitrogen derived from deep crust.