The geochemical features of natural gas in Kuqa depression and the discussion on the gas source

The natural gas found in Kuqa depression is mostly composed of hydrocarbons. Dry gas was mainly distributed in Kelasu structural belt, wet gas mainly in Yiqikelike structural belt and condensate gas mainly in frontal uplift area. The values of δ 13 C 2, δ 13 C 3 and δ 13 C 4 are on the heavy side, for example, the values of δ 13 C 2 are generally around 23‰, which indicates typical humic source rock derived gas. According to component and carbon isotope of the natural gas, the natural gas in Kuqa depression could be classified into 2 groups: humic wet gas and humic dry gas. By overall approach, the gas in Kuqa depression is mainly derived from the source rocks of Triassic and Jurassic, and the Jurassic source rock is more than Triassic source rock in the contribution to gas accumulation.