Effect of outer boundary condition, reservoir size, and CO 2 effective permeability on pressure and CO 2 saturation predictions under carbon sequestration conditions

A TOUGH2 simulation was conducted to investigate how the change of key model parameters affects pressure and CO 2 saturation response to CO 2 injection into a deep CO 2 storage reservoir. Given a domain of 100 × 100 km and a formation permeability of 10 −13 m 2 , outer boundary condition does not have a significant impact on pressure increase and CO 2 saturation results. In a simulation period of 30 years of CO 2 injection + 100 years of post CO 2 injection, with a total CO 2 injection volume of 6.3×10 7 m 3 at T = 47°C and P = 10.5 MPa (equivalent mass of 30 million tonnes of CO 2 ), there is no pressure difference between the no flow boundary case and the open boundary case given a domain size of 100 x 100 km (a total storage formation pore volume of 10 11 m 3 at T = 47°C and P = 10.5 MPa), and the maximum CO 2 plume radius difference is 0.5%. However, given a domain size of 10 × 10 km, outer boundary condition significantly affects pressure simulation results. At t = 130 years, the pressure increase in the no flow boundary case is 56.5 times of the pressure increase in the open boundary case at the cell 50 m away from the injection well. For the 10 × 10 km case, the impact of outer boundary condition on CO 2 saturation results is relatively small. The change in formation permeability significantly affects pressure increase results, while the change in CO 2 relative permeability model only affects pressure increase results at cells close to the CO 2 injector. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd