Abstract:

CO₂ geological storage are very important technology for the sustainable development for the industries with difficulties in reducing CO₂ emissions. Compared with some countries that have succeeded in large CO₂ geological storage projects with storage capacity of over a million tons per year, China’s CO₂ geological storage projects are still in early stage, most projects in the size of 100,000 tons per year. China still lacks experience in CO₂ storage site selection, injection and monitoring of large(>1 m tons CO₂/year) CO₂ geological storage projects. We classify the storage space into two types in term of their geological type, e.g. structural traps (anticline, fault and fracture) and lithologic traps (sandstone and carbonate reef). Based on the study of 15 large CO₂ geological storage projects around the world, four classes of indices for site determination were summarized, storage size, injecting capacity, safety and economic evaluation. The site selection principle and parameters for CO₂ geological storage sites with an annual storage capacity of one million tons are defined. In terms of basin types and geological characteristics of China, different CO₂ storage strategies need to be adopted. For instance, for large cratonic basins, such as the Ordos and Songliao basins, which contain wide distribution of sandbodies, and large-scale anticline and lithologic traps, they provid the potential for large-scale deep saline aquifers or depleted petroleum reservoir storage site. For the fault-bound basins such as the Bohai Bay and China offshore basins, well-developed faults or fault-related traps provide only small storage capacity and they are easily influenced by sealing effectiveness. It is thus necessary to adopt the strategy of comprehensive evaluation of trap groups with dynamic evaluation of fault activity; as for the superimposed basin in western China, the structural thrust belts on the basin margin have generally intensive tectonic stress, and great difficulty in CO₂ injection. This brings high risk for CO₂ injection and storage. Instead, the paleouplifts and slopes in the basin center may represent effective storage sites. Therefore, the evaluation strategy for basins in western China would need to consider zoning and stratification.

Key words: CO₂ geological storage, million-ton scale, type of confinement, location strategy