Geothermal energy relies heavily on accurate interpretation of subsurface data to optimize the prediction of the yield and lifetime of a reservoir. Subjective bias remains an overlooked source of uncertainty, even though its significant influence on subsurface data interpretation has been repeatedly proven. This thesis aims to address this subjective bias by providing structured justification for image log and outcrop fracture interpretations. The GRT-1 well at Rittershoffen, France, and the Buntsandstein outcrops in the Vosges region, France, are used as case studies.

A standardized protocol is introduced to provide a structured summary of the expected fractures in the system based on their driving geological processes. The interpreted fractures of three separate interpretations of the GRT-1 well are then linked to these driving processes, after which a composite log of the matching fractures between these is developed. The most prominent and reliable fracture drivers are determined to be the Early Oligocene ENE/SWS extension and the Miocene NW/SE compression. The majority of the picked fractures could be linked to at least one fracture driving process. An overlap in far-field driving processes might indicate reactivation of older fractures.

The protocol offers a promising framework to structure the interpretation of image logs and outcrops. Consequently, discussions on the reliability and justification of the interpretations can be held more constructively, resulting in a more reliable fracture characterization. It is recommended that the protocol be both tested across diverse geological settings and refined to enable more detailed predictions of expected fracture systems.