GAS GEOCHEMICAL CHARACTERISTICS OF PLATFORM-BASIN REGION IN TARIM BASIN

Based on the analysis of gas samples of the Tarim basin,the gas geochemical characteristics of the platform-basin region are summarized systematically.The hydrocarbon composition of natural gases is mainly wet gas in the platform-basin region of the Tarim basin,and dry gas in some areas.The wet gas is distributed in central Tarim basin,Mandong-Yingjisu,Yingmaili,Donghetang,Harderson and Jiefangqudong-Jilake.And Bachu and Lunnan-Sangtamu have both wet gas and dry gas.As for non-hydrocarbon components,nitrogen gas and carbon dioxide are dominant.Most areas in Bachu,central Tarim,Mandong-Yingjsu,Donghetang-Yingmaili,Harderson are characterized by the medium-high content of N2,and natural gases in Hetian River and Donghetang have high content of CO2.The carbon isotope distribution of natural gas is characterized by light at the central part and heavier in the peripheral areas.The carbon isotope value of methane is lower than -40‰ in central Tarim,Donghetang-Yingmaili and Harderson,and higher than-40‰ in Hetian River,Mandong-Yingjili,Lunnan-Jilake.The carbon isotope value of ethane is generally higher than-30‰.