Integrated 3D forward stratigraphic and basin modeling of the Santos Basin, offshore Brazil: Implications of sedimentary depositional facies and CO2 migration for silicification of continental carbonate reservoirs

Silicification plays an important role in the quality of pre-salt reservoirs, resulting in significant heterogeneities that are difficult to predict. A better understanding of the distribution of silicified pre-salt reservoirs at the basin scale helps in mapping such heterogeneities and further optimizing responsible hydrocarbon exploration and production. Here we investigate a scenario involving the interaction of an internal silica source from Mg-rich clay (sedimentary depositional facies) and CO 2 -rich fluid upwelling along deep-rooted faults. These are some of the main controlling factors of silicification, as confirmed with conceptual and numerical geochemical modeling. We present a new modeling workflow integrating forward stratigraphic modeling (FSM), basin/thermal modeling, quantitative chemical modeling, and map-based analysis to derive silicification probability maps of the Barra Velha Formation in the Santos Basin (Brazil). FSM simulates, with a process-based approach, the sediment distribution in the Barra Velha Formation including Mg-rich clay. Basin/thermal modeling simulates the rock-fluid systems evolution, CO 2 migration, accumulation, and concentration in the formation. Geochemical modeling provides Mg-clay transformation ratios depending on Mg-clay content of rock matrix and CO 2 concentration. Combining all elements together enables calculation of basin scale silicification probability maps across the study area. Highest probability of silicification is found above uplifted areas known to include Mg-rich clay, intense faulting, and trapping structures. • New, integrative basin modeling workflow for silicification probability prediction. • Integration of forward stratigraphic, burial/thermal modeling and geochemical data. • Forward simulation of dissolved salt, CO 2 transport and CO 2 equilibrium. • CO 2 concentration and Mg-rich clay presence determine silicification probability.