Abstract: The premium gas source rocks with content of organic carbon equal to or higher than 0.5% in Tarim basin are mostly found in Cambrian-Ordovician, Carboniferous-Permian and Triassic- Jurassie systems which have different horizontal distributions and various characteristics in lithology, sedimentology and organic geochemistry. It is indicated by present evaluation of hydrocarbon source types that there are two types of the products in Tarim basin, i.e. gas source rock where gas is only generated, and oil-gas source rock where both oil and gas are generated, being different from those of Sichuan basin and Erdos basin. The result shows that it is the three major factors, such as special sedimentary environment under special structural setting, types of organic matter in source rocks and degrees of thermal evolution, that control whether gas source rock developed or not and quality of it.

Key words: Tarim basin, Cas source rock, Spatial distribution, Organic geochemistry, Sedimentary facies, Organic matter type, Thermal maturity