Abstract: The condensate gas reservoirs in Tarim basin are characterized by great numbers, w ide distribution and lots of reserves, being the most enriched area in condensate gas reservoirs of China mainland. In this paper, based on the mechanism of condensate -gas reservoirs' formation and genesis of phase state, the authors analyzed the properties of reservoirs' formation in Tarim basin, and made a comparison with Sichuan, Erdos and Turpan-Hami basins, then pointed out that the condensate -gas reservoirs have two mechanism of formation and three types of phase state geneses. The key factor of condensate- gas reservoirs accumulation is that diversified hydrocarbon source rocks are in advantage stage of thermal evolution, and the late-stage heavily subsidence as well as late-stage gas migration accumulation provides important conditions of temperature, pressure, preservation for the condensate-gas reservoirs formation. Furthermore, the asynchronous evolution of hydrocarbon generation and accumulation makes for over. mature dry gas wet into condensate gas reservoirs.

Key words: Tarim basin, condensate -gas reservoir, geochemistry characteristics, phase state, oil and gas accumulation