--> Frontier Basin Exploration Through Integration of BSR-Derived Geothermal Gradient and CSEM Anomaly-Seismic Co-Rendering — Foz do Amazonas Basin, Brazil
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Frontier Basin Exploration Through Integration of BSR-Derived Geothermal Gradient and CSEM Anomaly-Seismic Co-Previous HitRenderingNext Hit — Foz do Amazonas Basin, Brazil

Abstract

Abstract

Exploration interest has greatly increased in the Brazilian Foz do Amazonas Basin (FdA) following recent oil discoveries in the conjugate margins. This study aims to de-risk exploration potential by Previous HitqualitativeNext Hit and Previous HitquantitativeNext Hit integration of exploration leads identified in two independent, but complimentary data sources; 3D Controlled Source Electromagnetic (CSEM) and modern 2D seismic. Furthermore, in order to address high risk petroleum system elements inherent in such a frontier basin, geothermal gradient modelling is carried out using exploration and Ocean Drilling Program (ODP) wells, as well as gradients calculated from Bottom Simulating Reflectors (BSRs) to assess present-day source maturity.

Previous HitQualitativeNext Hit CSEM-seismic integration was carried out using map, vertical and three dimensional displays with identified CSEM anomalies superimposed on play type distribution and all available seismic data types. Previous HitQuantitativeNext Hit integration was accomplished by cross-plotting different seismic attributes extracted over different windows against CSEM resistivity values.

For source Previous HitrockNext Hit maturity, BSR-derived gradients were calibrated with well data to create both cool-case (15°C/km) and warm-case (19°C/km) grids to determine the type of hydrocarbon which different areas were likely to be currently generating. ODP gradients were discounted; they were higher than the other datasets due to gas expansion recorded within cores. Primary hydrocarbon sources are syn-rift Aptian lacustrine oil-prone and Cenomanian-Turonian marine oil and gas-prone. The cool-case shows oil generating within Cenomanian-Turonian and Aptian intervals over most of the area. The warm-case favours gas-condensate generation to the southeast and oil to the northwest, away from the focus of the Amazonian Fan.

Previous HitQuantitativeTop CSEM-seismic integration indicates the resistive events are likely to be generated by hydrocarbon presence. In addition, deeper anomalies observed within the Cretaceous slump/ponded fan sequence deposits similar to the Zaedyus discovery in French Guiana, were confirmed by subsequent CSEM 3D inversions. Geothermal gradient modelling indicates these are most likely to be oil-prone.

The integration of geothermal gradient modelling together with modern seismic and CSEM data has provided a powerful exploration tool for de-risking potentially very large exploration leads identified by independent, but complimentary, data sources in this unexplored frontier basin.