Permeability variation in fluvial sandstones of the Marizal formation (Aptian, Tucano Basin, NE Brazil)

Resumo

This work aims at the study of the permeability distribution in relatively homogeneous fluvial sandstones, analogues for underground reservoirs of water and hidrocarbons. Outcrops of ancient sedimentary deposits mapped as the Banzaê Member of the Aptian Marizal Formation, fluvial in origin, in the Tucano Basin, NE-Bahia, were analysed with emphasis in petrophisical data acquired in the field using a portable handheld air permeameter (Tiny Perm II) from deposits previously interpreted as compound bar and abandoned channel deposits. The analyzed data allowed the recognition of distintct permeability distributions in architectural elements previously assumed as sedimentologicaly and petrographicaly indistinguishable. A third dataset could not be reconcilied with the above previous interpretations, pointing to the need of further detailment of those deposits. However, the general distribution of permeability values in the studied context are covariant with primary sedimentological properties, highlighting the relationship between underground reservoir origin and its petrophisical properties.