Predictability of properties of a fractured geothermal reservoir: the opportunities and limitations of an outcrop analogue study

Background The most essential requirements for a geothermal reservoir are sufficient temperature and permeability (e.g. Jung et al. 2002; Paschen et al. 2003; Schulz 2011; Schulz et al. 2009). Whereas the geothermal gradient for a given region is commonly constrained to a sufficient degree, estimates of porosities, fracture systems, permeabilities, and therefore the achievable convective heat flow in a planned fractured reservoir are subject to large uncertainties (Agemar et al. 2012; Domenico and Palciauskas 1973). Permeability provided by barren fractures, commonly referred to as structural permeability (e.g. Sibson 1996; Jolie et al. 2015), and thus the convective heat flow, may be substantially increased in fault-related reservoirs by locally enhanced fracture intensities and therefore create prime targets for geothermal exploration (Jung 2007; Paschen et al. 2003; Vidal et al. Abstract