8.3.5 Integration of time-lapse seismic with reservoir flow model
Time-lapse data may be compared to results from a reservoir simulator with the aim of improving the flow model. Subsequent predictions of reservoir behaviour will then be more accurate. In the SACS case a particular phenomenon occurred due to the thin shale layers acting as temporary vertical CO2 migration barriers that could only be identified on the seismic data with CO2 captured underneath. In other words, assumptions had to be made a priori on the shape, the lateral extent and the continuity of these shale layers for the reservoir simulation model. For that reason in SACS a history match has been performed especially honouring the amount of CO2 at the different depth levels, but only globally (as good as possible) the detailed lateral distribution. Figure 25 shows the synthetic seismics of 2001 created from a realisation of the reservoir simulation model. More information on this topic can be found in Lygren et al., 2002. Other publications are in press.
CO2 volume estimation from seismic data - In geological CO2 sequestration projects pre- injection reservoir simulation should be carried out with a reservoir model which is based on the best available geological data. These simulations can predict the CO2 injection rate that could be maintained, the rise in reservoir pressure caused by the injection, the likely lateral migration of the injected CO2 and the potential for CO2 dissolution into the formation water. Pre-injection reservoir simulation was carried out at Sleipner (Korbol and Kaddour, 1995) but this did not form part of the SACS project, which was established after injection began. The pre-injection reservoir simulation indicated injection of CO2 would be a feasible option from an operational point of view. This was sufficient to allow the project to proceed.