Interpretation and evaluation of post-stack 4D seismic time-shifts

A review and analysis of post-stack time-lapse time-shifts has been carried out that covers published literature supplemented by in-house datasets available to the authors. From these data conclusions are drawn regarding the effectiveness of post-stack time-shifts for overburden and reservoir monitoring. Time-shift data are classified into those originating from geomechanical effects and those due to fluid saturation changes. A variety of field examples are shown that display the range and magnitude of variation in each class. The underlying physical mechanisms creating these time-shifts are then described, and linked to a series of generic and field-specific rock physics calculations that accurately predict their magnitudes. Conclusions are drawn regarding the reliability of this attribute for monitoring purposes, and the extent to which further research development is required.