Methodology for estimation of CO2 storage capacity in reservoirs

The CO2 storage in reservoirs is one of the most effective ways of reducing the greenhouse gas emission, which is based on the mechanisms of structural and stratigraphic trapping, residual gas trapping, dissolution trapping and mineral trapping. The CO2 storage capacity in oil reservoirs includes theoretical, effective, practical and matched storage capacities. In the estimation of the CO2 storage capacity in both waterflooding and CO2 flooding oil reservoirs, theoretical and effective storage capacities can be obtained by the material balance and analogy methods. The theoretical storage capacity represents the physical limit of what the reservoir system can accept. The effective storage capacity represents a subset of the theoretical capacity and is obtained by applying a range of technical cut-off limits to a storage capacity assessment which incorporate the cumulative effects of reservoir and fluid parameter. When the material balance method is used, the amount of CO2 dissolution is not negligible. In using the analogy method, the key is to determine CO2 utilization factor. Examples show that the method is simple and convenient for the estimation of the CO2 storage capacity in China.