Use of Simultaneous Seismic Facies Analysis in 4D Inversion Interpretation Workflow

4D inversion results generally consist in cubes of property changes, such as differences in P-impedance (or P-velocity), in S-impedance (or S-velocity) and in density. A further step is to associate these elastic parameters to reservoir petrophysical parameters, such as porosity and absolute permeability, for fluid flow reservoir simulation purpose. Seismic facies analysis based on 4D inversion results is a key point to start addressing this demand. In this work, a pattern recognition approach, commonly used on the basis of 3D elastic inversion results, is extended to the 4D case. A unique pass is used to take into account both baseline and monitor information. By using this pattern recognition technique, variations of the seismic signature are identified, and related to possible 4D effects. A brand new seismic facies appears on the monitor data. This facies was interpreted thanks to the separation of pressure and saturation effect allowed by the use of P- and S-attributes. The resulting seismic facies maps fostered reservoir engineers to further analysis of pressure evolution in the reservoir.