Fig. 1

Model geometry and boundary conditions. A Schematic geological cross-section of a TVZ geothermal reservoir loosely based on Rotokawa (McNamara et al. 2016; Milicich et al. 2020); Wairakei (Sepulveda et al. 2012); and Ohaaki (O’Sullivan et al. 2021) geothermal reservoirs. Thick grey arrows are potential upflows and lateral flows in the reservoir. All formations are pervasively fractured. The diagram is oriented NW–SE, i.e. perpendicular to the Taupō Rift and hence perpendicular to the dominant fracture and fault strike. Pervasive fractures are represented on small squares in each rock types. B DFN geometry (physical extent 1 km × 1 km) and pressure boundary conditions. Dashed grey lines represent drillholes deviated 20° from the vertical, similar to those in which borehole images used in this paper were collected