Numerical modeling including hysteresis properties for CO2 storage in Tubåen formation, Snøhvit field, Barents Sea

In April 2008 the first injection of supercritical CO2 started into the Tubåen Formation from the Snøhvit field, Barents Sea. At full capacity, the plan is to inject approximately 23 Mtons of CO2 via one well during a 30 year period. The aim of this study was to simulation the 30 years of injection of supercritical CO2 and the following long term (5000 years) storage of CO2 in the Tubåen formation. The formation is at approximately 2600 meters depth and is at 98 °C and 265 bars. The simulations suggested that, because of limited lateral permeability, the bottom hole pressure increases rapidly to more than 800 bars if an annual injection rate of 766000 tons is used. This is significantly higher than the fracture pressures for the formation, and it is therefore suggested that the aim to inject 23 Mtons over the planed 30 years may be unrealistic. To prevent fracturing due to increasing pressure, the bottom hole pressure constraint is applied that leads to significant decrease in the amount of CO2 injected. With the hysteresis property applied, reservoir pressure behavior is the same in the base case (no hysteresis); however, the CO2 plume is distributed over a smaller area than in the base case. Similar to the case of hysteresis, the diffusion flow case shows the CO2 plume to be distributed over a smaller area than in the base case, but reservoir pressure decreases more than in the other two cases