A Workflow for 4D Seismic Analysis Based on Carbonate Rock Physics Applied to Brazil Pre-Salt

Summary We propose a workflow to evaluate 4D seismic signals around Water-Alternating-Gas (WAG) injection wells in a Brazilian pre-salt carbonate field. Using a carbonate rock physics modeling approach introduced previously, we forward model 4D seismic responses in the form of 4D attributes and compare these with attributes from expected 4D signals to quantify the impact of different fluids (water, oil and gas with C02 content) on the reservoir 4D seismic detectability for a high-fidelity OBN acquisition system. We explore the uncertainties in the saturation scenarios via a cascading analysis of multiple WAG injection switches through time. We illustrate some non-unique 4D responses that complicate 4D analyses and infer the minimum saturation changes required for 4D seismic detection in this carbonate reservoir using OBN data.