Buried Cretaceous Delta of the Barreirinhas Basin, Offshore Brazil: Potential Source of Structural and Stratigraphic Traps in Deepwater Sandstone?

Reuber, Kyle; Mann, Paul; Saunders, Mike

The Barreirinhas Basin, offshore Brazil is a major focus for recent oil and gas exploration. Previous exploration efforts in the basin were focused on structural traps at the shelf edge that have yielded no major discoveries to date. In this complex structural framework of the Barreirinhas Basin, I use 6,500 km of recently acquired seismic reflection data to show mapping evidence for a wedge-shaped, seaward tapering basin floor fan as a component of a larger 15,500 km2 deltaic system, which ranges in thickness from 1,000-3,000 m in 1,000-2,500 m of water. The basin floor fan deposits of Campanian age are located in the same area as the modern Mearim River, which presently has limited flow and a small delta. These deposits may have been part of a larger drainage network that included a sediment bypass into deeper water across the steep, strike-slip-controlled equatorial margin of Brazil. Isochron maps of the mounded basin floor fan units show well defined fan and lobate shapes whose apices project to plus or minus 200 km to the location of the modern Mearim River. By the deposition of basin floor fans in Campanian time, the underlying source rocks of Albian-Cenomanian age (Caju Group) were deposited as a sheet like mass. Overburden above the Caju Group totals 3-4 km of mainly clastic rocks, and previous exploration efforts have calculated these source rocks to be in the oil window. The proposed play in the Barreirinhas basin is compared to similar successful oil plays on its conjugate margin in Ghana, West Africa.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013