Time-lapse FWI prediction of CO₂ saturation and pore pressure

Qi Hu, Kristopher A. Innanen

The estimation of CO₂ saturation and pore pressure from time-lapse seismic data requires a physical model relating the variations in reservoir properties to the changes in seismic attributes. We propose a complete rock physics workflow combing Macbeth's model and Gassmann’s equations to predict elastic properties as a function of porosity, mineralogy, saturation, and pressure. We validate this workflow using a published dataset. In particular, we demonstrate the advantages of Macbeth's model in predicting the effect of pressure changes. Furthermore, we propose a full waveform inversion (FWI) algorithm incorporating the proposed model for the prediction of the time-evolution of CO₂ saturation and pore pressure. This approach allows for direct updating of reservoir properties from seismic data. We derive static rock properties, such as porosity and clay content, from baseline data and use them as input to predict dynamic reservoir properties (saturation and pressure) from monitor data. We illustrate the potential of the approach using a synthetic time-lapse dataset.