Genesis Types and Migration of Middle and Lower Assemblages of Natural Gas in the Eastern Belt around the Penyijingxi Sag of the Junggar Basin, NW China

This study analyzes the geochemical characteristics of natural gas composition, carbon isotope, and light hydrocarbon in eastern belt around Penyijingxi sag Junggar Basin. The result shows that content is dominated by alkane gas, with low contents heavy non-hydrocarbon components. overall isotopic composition alkanes a trend as δ13methane (C1) < δ13ethane (C2) δ13propane (C3) δ13butane (C4), all δ13C1 values are <−30‰, which typical gases organic origin. mainly coal-derived from Lower Urho formation, mixed small amount oil-associated Fengcheng formation. vertical migration resulted mixing at different stages same origin, should be origin isotope inversion. diffusion carboniferous oil reservoirs has led to differences among wells. These may indicate shallow layers favorable stratum for next step exploration sag.