High-resolution stratigraphy and characterization of reservoir-critical heterogeneities in the giant Tupi Field, pre-salt Santos Basin, Brazil

Abstract

The large oil discoveries that have occurred in recent decades in the pre-salt section of the South Atlantic sedimentary basins have promoted a significant volume of scientific research regarding the origin of these deposits. Most of the current studies of this stratigraphic interval focus on regional aspects or sedimentological and diagenetic processes. However, few studies encompass the geological characteristics of the pre-salt deposits from a reservoir-scale perspective. This work addresses the construction of a detailed reservoir-oriented stratigraphic framework for the giant Tupi Field. Discovered in 2006 following a successful exploratory campaign in the southeastern Brazilian deep-water, the Tupi Field's main reservoirs are sag-phase carbonates from the Aptian-aged Barra Velha Formation. These rocks accumulated in alkaline to highly alkaline lacustrine settings, which allowed the development of unusual syngenetic elements, such as magnesian clays, calcitic spherulites, and calcitic shrubs. The reservoirs' depositional organization was essentially conditioned by climatic oscillations and tectonic activity, which controlled sedimentation rates and accommodation styles through space and time. The high-resolution stratigraphic framework established in this article supports a detailed understanding, at different scales, of the Tupi Field's sedimentological evolution and its main vertical and lateral facies distribution. These aspects have, in turn, provided essential inputs for reservoir characterization and constrained critical heterogeneities of the 3D geocellular model, even in reservoirs affected by diagenetic processes.