Adaptive scaling for an enhanced dynamic interpretation of 4D seismic data

In this study, importance is drawn to the role of engineering principles when interpreting dynamic reservoir changes from 4D seismic data. In particular, it is found that in clastic reservoirs the principal parameters controlling mapped 4D signatures are not the pressure and saturation changes per se but these changes scaled by the corresponding thickness (or pore volume) of the reservoir volume that these effects occupy. For this reason, pressure and saturation changes cannot strictly be recovered by themselves, this being true for all data interpretation. This understanding is validated both with numerical modelling and analytic calculation. Interestingly, the study also indicates that the impact of gas saturation on the seismic can be written using a linear term but that inversion for gas saturation can yield at best only the total thickness/pore volume of the distribution. The above provides a basis for a linear equation that can readily and accurately be used to estimate pressure and saturation changes. Quantitative updates of the static and dynamic components of the simulation
model can be achieved by comparing thickness or pore volume-scaled changes
from the simulator with the corresponding quantities on the inverted observations.