Borehole imaging challenges and added value in fracture reservoir characterisation

Borehole Image logging (BHI) are becoming very essential tools for fracture reservoir characterization. These tools physically detect fractures and measure fracture properties (orientation, dipping magnitude, etc.,). This paper provides an overview of some challenges in interpreting image log data from conventional fractured reservoirs, heavy oil, tight gas and unconventional fractured reservoirs. The papers also highlight causes of the match and the mismatches between core and image log data from different reservoirs. Most of the mismatches and discrepancies between core and image logs result from: 1) lack of resistivity (conductivity) contrast between host rock and fracture fill; 2) size of fractures, 3) overall image and core quality; 4) hydrocarbon and fluid impact on images. The greatest degree of mismatch between core vs. BHI fracture counts was observed in tight gas reservoirs and heavy oil fracture reservoir analysis. In summary, core calibration and proper understanding of image interpretation pitfalls associated with different reservoir types is important for better understanding vertical and lateral fracture connectivity and modelling.