Characters of pre-salt lacustrine carbonate reservoir, Santos Basin, Brazil

Exploration in pre-salt lacustrine carbonate rocks has been one of the hottest topics for recent years in oil-gas industry.However, the study of the characters of such type of reservoir remains relatively poor.Based on drilling-cores, thin sections, physical property data, etc., this paper comprehensively investigated reservoirs petrological characteristics, porosity space types, physical properties, diagenesis and their effects.It shows that microbilite and bioclastic limestone are dominant reservoir rocks.The former consists of stromatolite and oolite and the latter of coquina.The major porosity types in microbialite include secondary porosity, such as dissolved pores, intercrystalline pores, interparticle pores, and diagenetic-altered pores.And the coquina is dominated by moldic pores, dissolved pores, vugs and intercrystalline pores.Pre-salt lacustrine carbonate usually has medium-high porosity and permeability.It also suggests that both dolomitization and dissolution have positive influences on reservoir properties.The reservoir rocks are mainly iformed under meso-diagenesis, except a few which may remain in the stage of early diagenesis.