4D Analysis

Changes in subsurface conditions as a result of production (e.g. reservoir compaction) needed to be quantified for further field development.

A 4D AVO and rock physics inversion was conducted to investigate the effects of fluid depletion.


  1. A rock physics model was derived for the upper (Figure 1) and lower (Figure 2) reservoir to investigate the relationship between elastic and petrophysical parameters. The difference in the rock physics trends are the result of effects such as differing lithology and fluid content and differential compaction.
  2. A simultaneous 4D AVO inversion was performed to estimate the baseline acoustic impedance, Vp/Vs and density (Figure 3) and associated changes (Figures 4 and 5). The changes in elastic properties highlight the spatial extent of production effects.
  3. A 4D rock physics inversion was performed to investigate the changes in petrophysical parameters as a result of production. The map illustrating the change in water saturation (Figure 7) highlights the spatial extent of the water flood.