The Complex Setting of Deepwater Espiacute;rito Santo basin, Brazil - Implications for Hydrocarbon Prospectivity

Husmo, Tore¹; Castro, Alvaro A.; Marcussen, Øyvind; Janocko, Michal; de Souza, Fernando Gomes de; Araujo, érika; Ramalho, Franceline O.; Basta, Gustavo; Correia, Rafael F.; Sampaio, Renata; Cunha, Rogério; Diniz, Sabrina; and Conde, Valeria
¹[email protected]

Great water depth, complicated geology, disappointing drilling results and problematic seismic data imaging has challenged exploration of the deepwater Espiacute;rito Santo basin, Brazil. We will present recent understanding on the larger scale controls on post-salt clastic deposition in a terrain dominated by gravity induced salt tectonics. In other presentations the shelf to slope depositional controls and processes have been discussed, and we will here demonstrate the variety of settings that occasionally make post-salt play models work, and other times not.

From regional studies it is clear that the shelf margin of this passive margin basin has been essentially stable through time, and clastic material has been transported form shelf to basin floor by two major and some minor transport systems, delivering massive amounts of sands to essentially the same location in the basin. The presence of Aptian salt along this passive continental margin triggered listric faulting and movements of raft blocks already from the late Albian time, leaving significant gaps in the strata very similar to what is observed from the offshore Angola conjugate margin. The relative movement as measured from seismic data increases towards the south, and can explain the increased amount of displaced salt onto oceanic to transitional crust in the same direction. Frequent observations of major south to north thrusting may be caused by segment rotation of individual raft blocks. These movements complicate both structural and depositional paleoreconstructions.

Early exploration drilling campaigns failed to find hydrocarbons in deep water. Predicting presence of both reservoir and mature source rocks were major issues, and seismic data quality was highly variable. New discoveries from 2010 onwards sparked new interest in the area. More recently, traps under shallow salt have been drilled, and the results are still being evaluated. A variety of plays and trap types are identified, but low prospect probability, combined with high operational and development costs, have led to high commercial thresholds. Active exploration is ongoing in deep water Espiacute;rito Santo. Thorough integrated studies help to mitigate risk for plays and prospects, to mature more prospects for drilling and identify attractive open areas in this complicated setting.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013