Abstract: Based on the method of reservoir geochemistry, the formation of the condensate pool in Triassic in Jilake has been studied. By the study of gas compostion and the light carbon in condensate oil, it is suggested that the source of gas and condensate oil are sapropelic, and the condensate gas was formed by dry gas entering the oil. The study of reservoir bitumen showed that the source is not only the carbonate in middle and late ordovician, but also the carbonate in cambrian. The process of condensate pool formation is analyzed in detail. It is concluded that there are three periods in acculumation and one period in destroy in the process of condensate pool formation. The strata was reversed in Himalayan, and then the gas redistribution was formed the condensate pool.

Key words: gas composition, carbon isotope, light hydrocarbon, reservoir bitumen, Jilake gas field