The Sleipner Project, with an injection history of more than 25 years and a total volume of over 20 Mt (million metric tons of CO2) injected, is a prime example of a successful SCS project. However, even this project experienced unexpected events.
The pre-injection analysis of reservoir heterogeneity from well data identified multiple one-meter-thick shales within a 300 m thick reservoir sequence. As injection proceeded, the shales acted as baffles, limiting the upward movement of CO2 from the injection point to the top of the reservoir.
Instead of accumulating below the caprock (top seal) in Layer 9 as expected, a substantial portion of the injected CO2 became trapped beneath underlying baffles and migrated laterally. This is evidenced by the enhanced reflection amplitudes in the Figure below due to CO2 invasion into multiple layers. This underestimation of reservoir heterogeneity is benefiting the project as it results in a larger storage volume and less buoyancy pressure against the caprock.
