Petrophysical characterization of Lagoa Salgada' stromatolites – A Brazilian pre-salt analog

Abstract

Over the last decade, giant hydrocarbon reservoirs were discovered in lacustrine (Barremian-Aptian) and lagoonal (Aptian) carbonate reservoir systems, under Aptian evaporites, in the Santos and Campos basins. These pre-salt carbonate reservoirs contributed to placing Brazil among the world's top ten petroleum producers, and intense scientific interest has arisen to improve the characterization and understanding of these formations. The study of outcrop analogs is one of the most common techniques employed for such a goal. Several studies have pointed out that the Lagoa Salgada stromatolites are a potential analog of one of the important reservoir facies of pre-salt rocks. In this work, we used Mercury Intrusion Porosimetry (MIP) data obtained on these stromatolites for evaluating porosity, pore size distribution, surface area, tortuosity, permeability, and pore compressibility. These results provided insight into the pore system of these rocks and allowed a comparison to pre-salt reservoir data. This comparison highlighted that such permo-porosity and pore compressibility behaviors of two facies of these outcrop rocks are analogous to the Brazilian pre-salt stromatolites.