Three-dimensional stratigraphic-sedimentological forward modeling of an Aptian carbonate reservoir deposited during the sag stage in the Santos basin, Brazil

Stratigraphic-sedimentological forward modeling is a useful technique to test the role of parameters that may act in the depositional processes of sedimentary rocks. The technique was applied to the Santos basin, Brazil, using the software program DIONISOS to test possible depositional scenarios for an Aptian section of a lacustrine carbonate platform developed during the late sag stage (uppermost pre-salt section) of the basin. Different parameters were tested in a set of numerical simulations with the aim of reproducing the carbonate facies spatial distribution and the overall stratigraphic stacking pattern of the platform, as observed in the available well data. Several models were simulated, and four of them are discussed in this paper. Based on the available descriptive data from 10 wells, Model 3 is considered to produce the best fit to explain the development of the 100-m thick Aptian carbonate platform, occurrences of grainstones and stromatolites as proximal and intermediate facies, respectively, and the overall carbonate stacking pattern. Thus, based on 3D stratigraphic-sedimentological forward modeling, the best set of environmental conditions able to explain the pattern of carbonate deposition observed in the study area are (1) a slow carbonate depositional rate (0.08 mm/y over an interval of 2.4 My), which is indicative of a larger microbial contribution, and (2) lake-level oscillations, which were essentially induced by arid climatic conditions. These results also enable new perspectives for the application of stratigraphic-sedimentological forward modeling as a predictive tool for hydrocarbon exploration in carbonates and for the development of depositional models of other sag carbonate platform settings.