8.3.6 Reservoir simulation in SACS: Verifying the seismic and geological interpretations and predicting the long-term fate of CO2
Further objectives of reservoir simulation in a CO2 sequestration project are likely to be:
1. Verify and improve the seismic and geological interpretations of the reservoir around the
injection site and re-run simulations of the migration of the injected CO2 during and shortly after the injection period.
2. Use the history matched reservoir model of the area around the injection site to build a large-scale model to predict the long-term fate of CO2.
These objectives require history matching and thus should take place during the monitoring of the CO2 sequestration operation.
In the SACS project, two new reservoir models were built to achieve these latter objectives. The first describes the formation near the injection site. It covers an area of approximately 7 km2 and consists of a large number of small grid blocks. This model was iteratively calibrated and adjusted in the light of interpretations of the seismic images of the CO2 accumulations from the repeated seismic surveys performed three and five years after the start of injection.
The second model covers an area of 128 km2 and is being used to predict the migration of CO
2
over a period of several thousand years under the assumption that there is no migration
through the upper seal, which is revealed from the current study (Section 7.3.3). This model has to rely on a coarser grid due to computational constraints.