Geochemical Feature of Natural Gas in Wu-Xia Area, Junggar Basin

The natural gas in Wu-Xia area is dominated by methane wet gas of high maturity with dry coefficient of 0.8801, V(iC4)/V(nC4) of 0.88, V(iC5)/V(nC5) of 0.99 in average. Its non-hydrocarbon gas contains high content of N2, less CO2, micro-O2 and free H2S. With increase of the depth, the relative density, dry coefficient, methane content, heavy hydrocarbon gas content and non-hydrocarbon gas content have 7 changing trends by regularity. The natural gas is characterized by δ13C1δ13C2δ13C3δ13C4 and the alkane gas is original organic genetic gas. The source rocks produce gases in low-matured and matured stages with Ro from 0.21% to 1.66%. According to the relationship between δ13C1 and δ13C2-δ13C1 as well as δ13C1 vs. V(C1)/V(C2+3), it is judged that the origin of natural gas belongs to associated gas of crude oil, and a small amount of associated gas of condensate oil may occur in Wu-32 Wellblock.