Modeling and Interpretation of Time-lapse Seismic in Reservoir Simulation Models

Using an integrated approach of reservoir simulation, rock physics and seismic modelling the present study analyses the influence of changes in the distribution of fluids in a reservoir on time-lapse seismic sections. The forms and occasions in which these changes can be detected are studied to help in the characterization of the fluid dynamics inside the reservoir. To analyse these effects reservoir production simulations were conducted in a geological model of the Namorado sandstone reservoir in Brazil´s Campos basin. Through a Gassmann fluid substitution approach time-lapse impedance maps were created for the reservoir, and synthetic seismic sections computed. Interpretation of both water injecting and gas injecting situations were conducted in order to quantify the differences between oil-water and oil-gas substitutions and investigate the different ways they affect seismic amplitudes. Linear relations were found between the thickness of banks of injected fluid and seismic amplitudes. With this, interpretation of seismic sections becomes ambiguous and the distinction of areas of water from areas of gas saturation becomes tricky without knowing fluid thickness.