f Thermal and Petroleum Systems Evolution in the Outboard Campos and Santos Basins, Offshore Brazil: Insights from 3D Basin Modelling

Our knowledge of the evolution of passive margins has greatly improved over the last two decades. Field studies and observations from new seismic and well data have led to the development of new concepts on crustal architecture and rifting mechanisms in many continental margins. The continual search for new or overlooked petroleum domains has led exploration efforts towards more distal regions and consequently broadened our range of petroleum exploration.

The prolific Atlantic margins of the Campos and Santos Basins, offshore Brazil, are prominent areas where these new concepts were crafted and led to exploration success. Recent drilling activities offshore Campos and Santos, focused mainly on exploration leases acquired during recent ANP licensing rounds, illustrate the push towards more distal exploration. Although results have been mixed, some recent exploration wells have confirmed the presence of working petroleum systems in the outer basins and potential for liquid accumulations.

Here we present a regional 3D petroleum systems model constructed and calculated for an extensive area across Campos and Santos Basins ( Fig. 1 ).

The model integrates regional interpretation of seismic data with a meticulous mapping of crustal domains along the margin. A comprehensive compilation of present-day temperature and thermal maturity data was used for calibration purposes.

To assess the impact of the new models of margin development on the evolution of petroleum systems in the outer reaches of the Brazilian continental margins, the entire lithosphere was considered in temperature computations. The effect of radiogenic heat production is poised to be very different with respect to more proximal domains, but we can also anticipate a significant thermal imprint related to extreme crustal thinning (hyperextension) and various igneous events associated with attenuation and break-up. Special care was thus taken to properly define the thermal basement of our model. Thorough mapping of crustal domains along the area of interest was performed integrating seismic and potential fields data.

Sensitivity of several input parameters was tested, including different thermal scenarios and variations in source distribution, organic richness, and petroleum generation kinetics. This modelling exercise allowed us to move forward and become predictive in the assessment of the petroleum prospectivity of the study area. Model predictions highlight the potential for liquid petroleum in the outboard pre-salt play and have allowed us to identify new exploration opportunities in the area.