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An important question for the Carbon Capture, Storage, and Utility program is “can we adequately predict the CO 2 plume migration?” The Sleipner project in the Norwegian North Sea provides more time-lapse seismic monitoring data than any other sites for tracking CO 2 plume development, but significant uncertainties still exist for some reservoir parameters. In order to simulate CO 2 plume migration and assess model uncertainties, we applied two multi-phase compositional simulators to the Sleipner Benchmark model for the uppermost layer (Layer 9) of the Utsira Sand and calibrated our model against the time-lapsed seismic monitoring data at the site from 1999 to 2010. Approximate match with the observed plume was achieved by introducing lateral permeability anisotropy, CH 4 in the CO 2 stream, and adjusting reservoir temperatures. Model-predicted gas saturation, thickness of the CO 2 accumulation, and CO 2 solubility in brine – none of them used as calibration metrics – were all comparable with interpretations of the seismic data in the literature. Hundreds of simulations of parameter sensitivity (pressure, temperature, feeders, spill rates, relative permeability curves, and CH 4 ) showed that simulated plume extents are sensitive to permeability anisotropy, temperature, and CH 4 but not sensitive to the other analyzed parameters. However, adjusting a single parameter within the reported range of values would not reproduce the north–south trending CO 2 plume. It took a combination of permeability, CH 4 , and temperature adjustments to match simulated CO 2 plume with seismic monitoring data. On the other hand, even with a range of uncertain modeling parameters, the predicted fate of CO 2 fell within a narrow band, ∼93 ± 2% structural/hydrodynamic trapping and ∼7 ± 2% solubility trapping. The calibrated model is not unique. Other possibilities for reproducing the elongated plume such as a slight tilting of the caprock surface to the south and subtle geological features in the Layer 9 were not experimented with in this study, but are worthy of exploration for future studies. While it appears that we were able to reproduce the north–south elongated CO 2 plume, which is a modest improvement over previous models, the adjustments of parameters need to be verified with new observations. [ABSTRACT FROM AUTHOR]