TITLE:
Characterization of Microscale Heterogeneities in the Sedimentary Deposits of the Morro Pelado Member, Rio do Rasto Formation, Paraná Basin: Implications for Reservoir Quality
AUTHORS:
Alexandra Nicole Sanchez Hidalgo, Manoela Bettarel Bállico, Celso Peres Fernades, Monica Oliveira Manna, Rodrigo Nagata, Anderson Camargo Moreira, Iara Frangiotti Mantovani, Maiara Silva Baltazar, Ezequiel Galvão de Souza
KEYWORDS:
Morro Pelado Member, Pore System, Reservoir
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.14 No.1,
January
15,
2026
ABSTRACT: This article presents the petrophysical and depositional characterization of the Morro Pelado Member of the Rio do Rasto Formation. Sandstones from eolian and fluvial depositional system were analyzed to understand the variability of the pore system. For this purpose, petrographic analyses, mercury intrusion porosimetry (MIP), and X-ray computed microtomography (Micro-CT) were integrated, enabling a multiscale assessment of the petrophysical characteristics. The results revealed highly heterogeneous pore systems, with total porosity ranging between 0.33% and 25.53% and permeability values oscillating from less than 3 mD to over 2400 mD. The best reservoirs were identified in fluvial sandstones, particularly in the facies of lateral accretion bars and aggradational sandy bedforms, associated with high primary porosity, good pore connectivity, and low carbonate cement content. In contrast, the eolian sandstones behave as unconventional reservoirs, with systems dominated by micropores, narrow pore throats, and low connectivity. In the overbank deposits, high-productivity reservoirs were observed in terminal splays, contrasting with matrix- and carbonate cement-rich units. Permeability anisotropy and the presence of dual porosity stood out as essential factors in controlling subsurface flow. The integrated analyses reinforce the need for applying multiscale models in the petrophysical characterization of the unit, considering the contribution of isolated microporosity and the role of sedimentary structures in orienting preferential flow paths. The obtained results highlight the potential of the Morro Pelado Member as a heterogeneous siliciclastic reservoir, with relevance for hydrogeological studies.