GLOBAL SENSITIVITY AND UNCERTAINTY ANALYSIS OF PETROLEUM SYSTEM MODELS IN THE SANTOS BASIN

This study applies Alterna, a machine-learning platform for uncertainty propagation and global sensitivity analysis, to the Água Viva play in the Santos Basin. The three-dimensional petroleum system model comprises 17 horizons, 11 chronostratigraphic levels, and three source-rock intervals: one interval of the Itajaí-Açu Formation (Post-salt) and two intervals of the Piçarras Formation (Pre-salt). Thermal calibration used temperature and vitrinite-reflectance data from wells in the Caravela Field. A no-migration configuration isolated the response of transformation ratio and generated hydrocarbon mass to uncertainties in basal heat flow, kerogen reactivity, salt thermal conductivity, and total organic carbon. Training scenarios were projected into a latent space, and regression models learned the projection coefficients, producing a surrogate model capable of reconstructing spatial results for additional parameter combinations. The trained model generated mean, P10, P50, P90, and standard-deviation maps and quantified parameter influence through Sobol indices. In both pre-salt and post-salt source rocks, basal heat flow and kerogen reactivity exerted substantially greater control on transformation ratio than salt thermal conductivity. Generated mass in the lower pre-salt interval was mainly controlled by total organic carbon, whereas its contribution was minor in the upper interval. In the post-salt, the influence of total organic carbon was spatially modulated by salt thickness, particularly along the southeastern north-south sector; thinner salt areas also showed significant contributions. Alterna therefore enables rapid, transparent, and reproducible exploration of numerous uncertainty scenarios and identifies the variables that control petroleum generation. Full petroleum system simulations, including hydrocarbon generation, expulsion, migration, and accumulation, are being conducted to evaluate the sealing effectiveness of post-salt rocks and the role of migration pathways through salt windows in hydrocarbon accumulation, thereby reducing exploration uncertainty.