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. ... Read more

Due to quick population growth and urbanisation in Kumasi, Ghana, groundwater depletion is accelerating, and land cover changes reduce the rate of natural infiltration. A promising measure to combat rapid aquifer depletion is implementing Managed Aquifer Recharge (MAR), by rooftop rainwater harvesting and pumping this into wells. The objective of this paper is to delineate the (qualitative) impact of precipitation through Managed Aquifer Recharge on the groundwater level, by analyzing groundwater level changes of sites with and without MAR around Kumasi. To achieve this, multiple groundwater level and flow models have been constructed over different time periods with varying temporal resolutions to show the short- and long-term effect of precipitation on the groundwater level on sites with and without MAR. A rapid increase of groundwater level is observed during rain events, followed by a decelerating curve of infiltration towards areas with lower elevations. This dissipation is much faster in areas with high hydraulic conductivity (hours) than with low hydraulic conductivity (weeks). The groundwater level is recharged by MAR less in the dry season than in the wet seasons. MAR has a highly positive influence on the groundwater recharge. It will be most crucial to implement MAR in high elevations, where the overburden has low hydraulic conductivity, as natural recharge is limited here. The lack of soil and hydraulic head data limited the reliability of the models. Therefore, it is recommended to extend the database in these and additional research areas, aiming to differentiate the effect of MAR and the natural infiltration on the hydraulic head level. ... Read more