Time-lapse 3-D seismic physical modelling

Abstract

Seismic physical modelling is used to study the effects of seismic wave propagation in isotropic and anisotropic media, and to improve methods of data acquisition, processing and interpretation. Until recently, the use of unconsolidated sands for seismic physical models had been unsuccessful due to the lack of control or understanding of the natural variations that occur throughout the models. Our research has allowed many of the drawbacks to be overcome. The use of sands allows fluids to be incorporated into the models for the first time, providing a much more realistic analogue of hydrocarbon reservoirs, and presents an opportunity to expand the role of seismic physical modelling. The computer controlled modelling system allows repeatable acquisition, which makes it an ideal environment to study some of the time variant characteristics of reservoirs that occur with production. This is demonstrated with a model whereby the migration of kerosene and air is monitored with time-lapse surveys. Time-lapse 3-D (or 4-D) seismic is becoming increasingly important in the management of hydrocarbon production, yet there is a lack of model data to support some of the fundamental conclusions being made. Subtle anomalies on difference sections may in fact be artefacts of the different acquisition footprints or manufactured from the complex data processing that is necessary to allow comparison of legacy data sets. The ability to perfectly repeat data acquisition on sand models bypasses these problems such that any anomalies seen on difference sections can be directly attributed to changes that have occurred within the model. The development of TL3-D seismic physical models will also provide a number of other advantages, which are: 1. Inexpensive, real seismic data. 2. The absence of complications from seasonal or climate factors. 3. Rapid data turn around in a matter of days, rather than having to revisit an area years later.