Exploring the limits – Integrated drill cuttings analysis for fractured (basement) reservoirs

Summary A thorough drill cuttings study was conducted for a fractured basement reservoir, focusing on fracture analysis. The aim of this study was to provide input to a conceptual fractured basement reservoir model, progress the understanding of lithological controls on fracturing, and to investigate how the connected hydrocarbon volume from fractures and/or potential matrix are distributed at the well scale. A thorough macroscopic cuttings screening combined with insights from all available log, production and seismic data led to a selection of 45 cuttings samples, which were thoroughly analyzed with thin section microscopy, X-ray diffraction (XRD) and X-ray fluorescence (XRF). Our study shows that cuttings can provide a valuable source of subsurface information at a low cost – also with regard to fracture description. Outcomes show that a stereomicroscopic cuttings screening proved to be most suitable for fracture frequency detection. Thin section analysis combined with geochemical measurements were crucial to understand cement generations, related fracture conductivity and porosity types. Furthermore the study highlighted the linkage between lithology/metamorphic facies/hydrothermal alteration and microfracturing along with methodology limitations such as scaling, cavings and mud additives.