CCUS (Carbon Capture, Utilization and Storage) technology is the key technology to reduce carbon dioxide emissions in fossil energy power generation and industrial production, and it is also the bottom technology to achieve carbon neutrality in China. Carbon dioxide geological storage is the core component of CCUS technology, which determines the development potential and direction of CCUS technology. Taking Songliao Basin as an example, this paper establishes the evaluation method and index system of carbon sequestration in oil and gas reservoirs, reveals the physical and chemical mechanism of CO2-water–rock in shale reservoirs, establishes the evaluation model of carbon sequestration potential based on storage mechanism, and evaluates the carbon sequestration potential of unconventional oil and gas reservoirs in Songliao Basin. The research results of this paper lay a foundation for the subsequent establishment of carbon dioxide storage potential evaluation method suitable for China’s geological characteristics and scientific evaluation of carbon dioxide storage and utilization potential in China’s major oil and gas enrichment areas.