New Insights into Fracture-Modelling of Naturally Fractured Basement Reservoir - A Case-Study from Norwegian North Sea

For the last two decades there has been increasing interest for exploring altered and naturally fractured basement rocks underlying the Norwegian Sea. Authors have carried out outcrop and core analyses showing that these altered basement rocks could generally be subdivided into five different facies, controlled by natural fracture types, orientation, cementation, aperture, and degree of physio-chemical alteration. The main interpretation challenges of these basement rocks during drilling are facies variations over short distances, uncertainty related to natural fracture attributes and productivity. The main purpose of the present work is to present an integrated workflow using advanced logging-while-drilling (LWD) data and surface data interpretations to understand and define the basement facies architecture for facilitating future well-placement decisions. By using 3D advance seismic attributes, 2D and 3D ultra-deep azimuthal resistivity (UDAR), conventional log data and X-ray Fluorescence (XRF) elemental cross-plots diagram for igneous rocks based on the relationship between SiO2 vs Na2O+K2O) three main basement units were observed. However, by integrating image interpretation and Nuclear magnetic resonance (NMR) data, the basement was further subdivided into different facies types. Interpreted fractures with their attributes were compared with seismic attributes, and stochastic fracture network analysis was carried out.