Extensive reservoir modeling analysis and VSP processing are undertaken for a pilot steam injection project in Oman to understand the relationship between reservoir properties and seismic properties and how that changes with steam injection. Effects of different permeability distributions in steam-flooded reservoir models are analyzed in terms of their seismic response. A full-wave walkway time-lapse VSP is designed and processed to investigate possible 4D anomalies. Fluid substitution modeling (Gassmann’s substitution) is used to calculate modified petrophysical properties after initial steam injection. Prediction results in a 5 percent lower VP and 2 percent lower density. Predicted modifications in petrophysical parameters are sufficient to produce observable 4D effects in PP VSP. Time-lapse anomalies get enhanced when the near- surface VSP data are excluded. In this case, multiple and shear-wave suppression may actually compromise the observed 4D effects. Use of the muted upgoing wave–field for migration enhances the 4D amplitudes, but compromises the lateral resolution. The predicted PP time-lapse results and time-lapse attribute maps are similar to real field VSP results. The PS reflections in the present case are restricted to produce any measurable changes (for smaller angle gathers). I predict that a 6 percent decrease in density (due to steam saturation) may be sufficient for the Oman oil field to produce measurable changes in both PP and PS amplitudes for walkway VSP.

Extensive reservoir modeling analysis and VSP processing are undertaken for a pilot steam injection project in Oman to understand the relationship between reservoir properties and seismic properties and how that changes with steam injection. Effects of different permeability distributions in steam-f...