Tuning and Partial Saturation Effects on Reflection Responses at Sleipner Field

Calculating the normal incidence reflection responses of a stack of layers representing Utsira reservoir, we show that the seismic amplitudes are strongly affected by the partial saturation of CO₂ and brine in the high porosity sandstone layers. The anelasticity in these layers are taken into account using advanced rock physics models featuring uniform or patchy saturation. The difference in amplitude of the reflection response is significant between a stack of layers consisting of purely elastic layers and an equivalent stack of layers consisting of anelastic sands (partially saturated in brine and CO₂) and thin elastic shales. We conclude that neglecting partial saturation effects can be problematic when interpreting quantitatively seismic amplitudes using AVO or spectral decomposition methods.