Field exposures are often used to provide useful information about sub-surface reservoirs. This paper discusses general lessons learnt about the use of deformed Devonian and Carboniferous meta-sedimentary rocks in the Harz Mountains, Germany, as analogues for a proposed enhanced geothermal reservoir (EGS) at Göttingen. The aims of any analogue study must be clarified, including agreeing with people from other disciplines (especially reservoir modellers) about the information that can and cannot be obtained from surface exposures. Choice of an analogue may not simply involve selection of the nearest exposures of rocks of a similar age and type, but should involve consideration of such factors as the quality and geological setting of the analogue and reservoir, and of any processes that need to be understood. Fieldwork should focus on solving particular problems relating to understanding the EGS, with care being needed to avoid becoming distracted by broader geological issues. It is suggested that appropriate questions should be asked and appropriate analyses used when planning a study of a geothermal reservoir, including studies of exposed analogues.

A glossary of commonly used terms related to the geometric forms and geological settings of basement highs is presented to assist cross‐disciplinary understanding, qualifying prefixes for the termbasementare discussed and a scheme for characterising basement highs is presented. This scheme is designed to standardise, and to add rigour to, description of basement highs. It will thereby enhance basement high comparisons and assist understanding of basement highs across technical disciplines. The scheme enables systematic characterisation of: the geometry of a basement high; the lithologic units and structures in, above and around it; timings; tectonics and origins of the basement high and play elements relating to resource prospectivity. Use of this scheme is demonstrated using the southern Rona Ridge (West of Shetland, UK Continental Shelf). The tectonic, isostatic, erosional and stratigraphic processes that form basement highs are also discussed, and examples in proven petroleum systems are presented.

Inferences have to be made about likely structures and their effects on fluid flow in a geothermal reservoir at the pre-drilling stage. Simple mechanical modelling, using reasonable ranges of values for rock properties, stresses and fluid pressures, is used here to predict the range of possible structures that are likely to exist in the sub-surface and that may be generated during stimulation of a potential geothermal reservoir. In particular, Mohr diagrams are used to show under what fluid pressures and stresses different types and orientations of fractures are likely to be reactivated or generated. The approach enables the effects of parameters to be modelled individually, and for the types and orientations of fractures to be considered. This modelling is useful for helping geoscientists consider, model, and predict the ranges of mechanical properties of rock, stresses, fluid pressures, and the resultant fractures that are likely to occur in the sub-surface. Here, the modelling is applied to folded and thrusted greywackes and slates, which are planned to be developed as an Enhanced Geothermal System beneath Göttingen.