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The Super Giant Discoveries in the Pre-Salt Hydrocarbon Province of Santos Basin, Brazil

Mello, Marcio R.1; Azambuja Filho, Nilo C.1; Bender, Andre 1; Coelho, Alexandre L.1
1 HRT & Petroleum, Rio de Janeiro, Brazil.

In most areas of the deep and ultra deep waters from Santos Basin, Brazil, exploration has just begun with the discovered, in the last two years, of more than 20 billion bbls of oils of reserves with the Tupi, Jupiter, Guará, Carioca, Paraty, Caramba, Bem-Te-Vi and Iará oil fields.

The discoveries of low sulfur, pre-salt, lacustrine light oil (31 to 37 degree API), supergiant accumulations ocurred in the stromatolites, coquinas and clastic basal reservoirs sequences of the pre-salt rift and sy-rift sequences.

The 3D petroleum system simulation was based on a very detailed mapping using a 20.000 Km2 PSDM seimic data provided CGGVeritas and also on much geological and geochemical information extracted from HRT’s BrazilGeoData library. The objective was to assess the interplay among source, reservoirs, seals and trap geometries, thermal evolution of source rocks, hydrocarbon types, charge, timing of migration, accumulation and preservation and oil quality, and a volumetric quantitation of the accumulated reservoirs.

The main results indicate the presence of an overcharged source rock system, (e.g. Talcstevensitic (SR-1) and Coquinas (SR-2) lacustrine sources) reaching almost 90% tranformation in the main depocenter systems. Also, low pressure and low temperature values occur, below salt, in the main carbonate reservoirs from the Upper Lagoa Feia formation in the deepest part of the Basin and are critical in preserving the oil prone nature of the whole hydrocarbon province.

The charge and accumulation simulaton model, only for the pre-salt province, suggest a potential reserves, in the Cluster area studied, much larger than reported, getting numbers close to 40 to 60 Billion bbls of reserves.

The main exploration and production risk, however, lies in the reservoir rocks, composed by stromatolites, coquinas and vulcanoclastics that occurrs alternating themselves and sum more than 400 m in thickness and extend for more than 1500 Km, from Southern Santos up to Northern Espírito Santo Basin, presenting porosities ranging from 8% to 20% and permeability ranging from 20MD to 500MD.

The supergiant accumulations of light oil and condensates are trapped below a salt layer, ranging from 200m to 2000m, that acted as the BEST preservation element possible (seal, cushion and temperature drainer).

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009