根据地质、地化资料及热模拟实验结果,并应用物理化学理论,对莺歌海盆地CO_2气的成因及其主气源作了综合研究.认为本区CO_2气属壳源型岩石化学成因,其生成、分布、富集主要受控于泥底辟的发育演化;认为3100m以下莺歌海组二段及黄流组富含碳酸盐的砂泥岩是CO_2主气源. Based on the geologic and geochemical data and thermal simulation results and the application of physicochemical theory, a comprehensive study on the genesis and main gas source of CO_2 gas in Yinggehai Basin is made. Its formation, distribution and enrichment are mainly controlled by the development and evolution of mud diapirs. It is concluded that the carbonate-rich sandstone and mudstone in the second member of Yinggehai Formation and Huangliu Formation below 3100m is the main source of CO 2 gas.