Abstract: In order to quickly evaluate oil and gas preservation conditions, reservoir fluid properties and bit wear degree during exploration and development in Baiyun Sag, carbon isotope logging technology was introduced. By analyzing carbon isotope value of methane and ethane, carbon isotope ratio of methane in reservoir-cap rock and CO production, a comprehensive evaluation method based on carbon isotope logging technology for cap sealing capacity evaluation, reservoir fluid identification and bit wear evaluation was established. The results show that the method has certain feasibility, can provide a basis for subsequent exploration and development decision-making, and has a good application prospect.