The possibility of discovering deep-seated-source CO2 and CH4 gas fields is discussed, and a suggestion of looking for deep-seated-source CO2 gas fields in the area of alkali-olivine basalt on borders of the Shengli oilfield and deep-seated-source CH4 gas fields in the area of kemberite or al-kali basalt containing mantle-derived xenoliths in surrounding areas of the oilfield has been made in this paper.