Reservoir characterization using electrofacies analysis in the sandstone reservoir of the Norne Field (offshore Norway)

Abstract

The Norne Field reservoir sandstone comprises Early–Middle Jurassic interbedded sandstones and shales to massive sandstones with some thin continuous cemented interlayers. A detailed characterization of the geological heterogeneities through electrofacies analysis, together with the simulation grid refinement, has been used to derive representative facies and petrophysical models (porosity, net-to-gross (NtG) and permeability). An electrofacies database was created comprising six rock types, ranging from cemented carbonates through shales and into clean sandstones. In the absence of available cored sections, the electrofacies scheme was validated by the geological and petrophysical reports of 26 wells using gamma-ray, neutron and density logs. An artificial neural network algorithm enabled the probabilistic discrimination of the different types of electrofacies, with a sampling rate of 0.125 m. This high-resolution electrofacies database, together with a high-resolution geomodel grid, enabled us to map the fine-scale heterogeneities mainly materialized by decimetre shales and cemented layers that could represent stratigraphic barriers to vertical fluid displacement. The high-resolution datasets created in this study will form the working basis on which to perform a probabilistic and multi-objective history matching guided by production and 4D seismic data, and assisted by geostatistical parameterization techniques.