Petrophysical Characterization and porosity-permeability log calculation by Dual-Energy CT scan: Morro do Chaves Formation, Sergipe-Alagoas Basin, Brazil

Abstract

Considered important analogues of pre-salt reservoirs in hydrocarbon-producing basins throughout eastern Brazilian shore, the coquinas of the Morro do Chaves Formation (Barremian-Aptian of the Sergipe-Alagoas Basin) were studied in this work from a petrophysical standpoint using advanced characterization methods for cores recovered from four wells (2-SMC-01-AL, 2-SMC-02-AL, 2-SMC-03-AL e 2-SMC-01-AL) drilled in the Atoll Quarry, which is located in city of São Miguel dos Campos, Alagoas State, Brazil. To understand the relationships between lithological and diagenetic heterogeneities that control the distribution of permeability-porosity properties of this rock type, the cores underwent Dual-Energy X-ray imaging, which determines bulk density and photoelectric factor data to define seven rock types and generate effective porosity curves for the studied wells. Permeabilities in wells were modeled based on the Flow Zone Index (FZI) concept, and each reservoir interval based on the Global Hydraulic Elements (GHEs) approach. Results were calibrated with laboratory measurements in plugs, and porosity was classified by petrographic analysis by Digital Image Analysis (DIA). All wells were correlated and four internal flooding surfaces identified, with a regressive surface (RS) dividing the Morro do Chaves Formation into an upper section with better reservoir characteristics and a lower one with worse ones.