Fast repeat-modelling of time-lapse seismograms

In order to plan surveys for seismic time-lapse studies, seismograms are us ually simulated for a set of earth models corresponding to different stages of the oil production process. This can be expensive because, for reasons of accuracy, finite-difference (FD) modelling is very often applied. We present the Born repeat-modelling technique (BRM), which is a combinatio n of FD modelling and perturbation theory. Production effects are considere d as small perturbations of the earth model, and the Born approximation is used to compute the change in the wavefield due to production-induced modif ications to the reservoir properties. This is very efficient in the situati on described above. We give a detailed description of the proposed modelling scheme and discuss its applicability. The theoretical foundations of BRM are presented for on shore seismic experiments, and an extension to the case of marine (pressure ) seismograms is derived. In addition, the performance of BRM is demonstrat ed with several numerical examples.