Reservoir Petrofacies: a Tool for Quality Characterization and Prediction

De Ros, Luiz Fernando¹, Karin Goldberg² (1) Universidade Federal do Rio Grande do Sul, Porto Alegre/RS, Brazil (2) Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil

The intrinsic quality of petroleum reservoirs (porosity, permeability) is controlled by depositional structures, textures and composition, by diagenetic processes and products (volume or intensity, habits and distribution), as well as by pore types and distribution. Reservoir petrofacies can be systematically defined by the combination of these attributes. The concept of reservoir petrofacies is useful and operational for the characterization of reservoirs and for the prediction of their quality during exploration. The determination of reservoir petrofacies is initiated by the recognition of preliminary petrofacies through a systematic description of the listed attributes in samples collected along a representative distribution, followed by recognition of the attributes with larger impact on porosity and permeability. The preliminary petrofacies are then checked against petrophysical and petrographic quantitative parameters by using statistical or neural network tools. Threshold values are defined for the influent textural and compositional attributes that constrain the significant reservoir petrofacies. Reservoir petrofacies defined by this methodology are consistent in terms of petrophysical porosity and permeability, seismic and log signatures. Consequently, they can be used for sensible calibrations and for tri-dimensional representations of the quality of reservoirs. Reservoir petrofacies can be linked to stratigraphic and structural framework parameters for the development of coherent models of reservoir quality prediction.