Petrophysical, Mineralogical and Elastic Property Characterization of Halocene Carbonates from Salgada Lagoon, Brazil

Approximately 60% of oil and 40% of gas world reserves are in carbonate reservoirs. These reservoirs are heterogeneous with a textural variety and typically fractured, leading to low recovery factors and also complex relationship between rock properties and geophysical data. Studies of these reservoirs have become very important in Brazil after 2005, when Petrobras announced a large carbonate reserve in pre-salt region of Santos basin. Then, reservoir characterization requests a better understanding of the relationship between geology, petrophysical and acoustic properties. In this work, we made a mineralogical and petrophysical characterization of Halocene carbonates from Salgada lagoon, RJ, Brazil. Measurements of XRD and SEM showed that the stromatolite is composed mainly by high-magnesian calcite, with a small amount of aragonite and quartz. The thin section observation revealed the presence of skeletal material, quartz and regions that suggest recrystallization. The velocity and the bulk density were estimated from mineralogical and petrophysical information and compared with empirical equations. The velocity x porosity and density x velocity crossplots showed that this rock has a behavior close to a limestone. In a future work, these results will be compared to velocities obtained from rock physics models and from an experimental rock physics system.