Bias in borehole image fracture interpretation - comparing five independent interpretations of one image log

Borehole images are commonly used to characterize fractures in the subsurface, but interpretations however might be prone to interpreter bias. In this study, we compare five independent interpretations of a single borehole image log from the Geneva Basin, and assess the agreement/disagreement among interpreters regarding fracture frequency and orientation. We then relate the agreement/disagreement with the geology encountered by the borehole and the technical quality of the imagelog. The results show that certain lithologies such as bioclastic limestone favour consistent frequency interpretations. In general, there is little agreement on fracture orientation, but the highest agreement is where the dip of bedding surfaces is low (