Quantification and Prediction of the 3D Pore Network Evolution in Carbonate Reservoir Rocks

• Published in: Oil & gas science and technology 2012-01, Vol.67 (1), p.161-178
• Main Authors: De Boever, E., Varloteaux, C., Nader, F.H., Foubert, A., Békri, S., Youssef, S., Rosenberg, E.
• Format: Article
• Language: English
• Subjects: Applied geology; Dissolution; Earth Sciences; Environmental Sciences; Evolution; Geophysics; Global Changes; Mathematical models; Networks; Permeability; Physics; Porosity; Reservoirs; Rocks; Sciences of the Universe; Three dimensional
• ISSN: 1294-4475; 1953-8189
• DOI: 10.2516/ogst/2011170

This study presents an integrated approach that allows the reconstruction and prediction of 3D pore structure modifications and porosity/permeability development throughout carbonate diagenesis. Reactive Pore Network Models (PNM-R) can predict changes in the transport properties of porous media, resulting from dissolution/cementation phenomena. The validity and predictability of these models however depend on the representativeness of the equivalent pore networks used and on the equations and parameters used to model the diagenetic events. The developed approach is applied to a real case of a dolostone rock of the Middle East Arab Formation. Standard 2D microscopy shows that the main process affecting the reservoir quality is dolomitisation, followed by porosity enhancement due to dolomite dissolution and secondary porosity destruction by cementation of late diagenetic anhydrite. X-ray μ-CT allows quantifying the 3D volume and distribution of the different sample constituents. Results are compared with lab measurements. Equivalent pore networks before dolomite dissolution and prior to late anhydrite precipitation are reconstructed and used to simulate the porosity, permeability characteristics at these diagenetic steps. Using these 3D pore structures, PNM-R can trace plausible porosity-permeability evolution paths between these steps. The flow conditions and reaction rates obtained by geochemical reaction path modeling can be used as reference to define PNM-R model parameters. The approach can be used in dynamic rock typing and the upscaling of petrophysical properties, necessary for reservoir modeling. Cette étude présente une approche intégrée qui permet la reconstruction et la prédiction des modifications de structure 3D de pores ainsi que le développement de la porosité/perméabilité tout au long de la diagenèse des carbonates. Des modèles de réseau de pores réactifs peuvent prédire les changements en matière de propriétés de transport de milieux poreux, résultant des phénomènes de dissolution/cimentation. La validité et prédictibilité de ces modèles dépendent toutefois de la représentativité des réseaux de pores équivalents utilisés et des équations et paramètres utilisés pour modéliser les événements diagénétiques. L’approche développée est appliquée au cas réel d’une roche dolomitique de la formation arabe moyen orientale. La microscopie 2D standard montre que le processus principal affectant la qualité de réservoir consiste en la dolomitisation, sui