Impact of Geodynamics on Diagenetic By-products - An Input to Petro-acoustic Modeling of Pre-salt Carbonates

Diagenesis of the atypical presalt carbonate deposits is controlled by hydrothermal CO2-rich fluids circulation. In low CO2 pressure conditions, most of the reservoirs are plugged by Mg-clays (no reservoir). When the CO2 pressure is increasing, the Mg-clays can be leached and replaced by dolomitic rhombs, creating a good reservoir network. Precipitation of siliceous cement is also a by-product of the presence of the CO2, mainly in cooler areas. All these different fluids/rock alterations steps can be fossilized at different stages observed on thin sections. In-house coupled stratigraphical and diagenetical forward modeling of continental carbonates has been launched. First results are very promising and let possible to model carbonate springs in aerial conditions, which was not possible with the current forward modelling tools. This integrated approach will be used to experiment different geological scenarios (sedimentological and diagenetical) as imput to forward seismic modelling for derisking exploration and appraisal of the pre-salt play.