Geochemical characteristics and formation process of natural gas in Kela 2 gas field

On the basis of a large amount of natural gas components and the carbon isotope as well as some other analysis data in Kela 2 gas field, the geochemical characteristics, source, origin, and formation process of natural gas have been discussed. The components of gas in the field tend to be "dry", and the drying coefficient is close to 1.0. The carbon isotope tends to be heavier, for instance, the average of 13C1 is 27.36‰ and that of 13C2 is 18.5‰. Comprehensive analysis shows that humic natural gas in the Kuqa petroleum system comes mainly from Triassic and Jurassic source rocks, and the contribution of Jurassic source rocks to the pool maybe is more than that of Triassic rocks. The main cause that the gas tends to be dry and bears heavier isotope composition lies in the fact that Kela 2 natural gas is the accumulation of late production of humic source rocks, and it is affected by the abnormal high pressure as well. Considering the hydrocarbon generating and structural history, we can regard the gas pool formation processes as twice filling and twice adjusting (destroying), that is, the filling and destroying process in the early Himalayan movement and the filling and adjusting in the late Himalayan movement.