Petrophysical characterization using well log resistivity and rock grain specific surface area in a fractured carbonate pre-salt reservoir in the Santos Basin, Brazil

• Published in: Journal of petroleum science & engineering Vol. 183; p. 106372
• Main Authors: da Rocha, Herson Oliveira, da Costa, Jéssica Lia Santos, Carrasquilla, Antonio Abel Gonzaléz, Carrasco, Alfredo Moisés Vallejos
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-12-2019
• Subjects: Aptian carbonate reservoir; Brasilian pre-salt; Estimate permeability; Petrophysical properties; Specific surface image; Petrophysical properties; Estimate permeability; Aptian carbonate reservoir; Brasilian pre-salt; Specific surface image
• ISSN: 0920-4105; 1873-4715
• DOI: 10.1016/j.petrol.2019.106372

One of the most significant problems in the characterization and recovery of Aptian carbonate reservoirs, especially the Brazilian pre-salt, has been the lack of precise estimates of permeability. The heterogeneity of the permeability of the carbonate reservoirs occurs owed great different of the pore form occurred mainly by diagenetic processes. In this study, propose a joint and integrated methodology to estimate the permeability in the reservoir. To achieve this goal, porosity-permeability core data, image logs, applying the Rock Types concepts, analysis of the results of well log Nuclear Magnetic Resonance (NMR), modeling the well logs resistivity (laterolog and induction), as well as estimating the specific surface of the rock using images of section 2D from the pugs, to quantitatively estimate the permeability of the reservoir based on the petrophysical properties of the rocks. In the study it was possible to identify different pore systems distributed in eight Hydraulic Flow Units (HFU) determined from the pore groove radii. The Nuclear Magnetic Resonance (NMR) log it served to separate area of the spectrum corresponding to the small pores from the area corresponding to the large pores. The resistivity logs were analyzed with the purpose of estimating the direction (vertical, horizontal and dipping) and thickness of the fractures, which were also modeled with the purpose of identifying the invasion of the drilling fluid. The specific surface area was obtained by image processing algorithms. The results showed an acceptable precision of this methodology to estimate the permeability in carbonate reservoirs that have in their composition fragments of stromatolites and associated bioclastics, found partially or totally dolomitized.
•The Hydraulic Flow Units with the highest velocity zones coincide with the fractured.•Dissolution improves reservoir quality in both spherulites and stromatolites.•The presence of fractures does not affect the quality of the reservoir studied.•The digital image analysis allows estimation of the petrophysical parameters.•The radial resistivity image identified the drilling mud in the fracture zones.