Modelling fluid flow through fractured rock: Examples using TVZ geothermal reservoirs

Geothermal resources are often hosted within volcanic, plutonic, and basement-type lithologies. As such their matrix permeability can be very low and the transport and circulation of geothermal fluids will be dominated by fractures. Understanding the flow of hydrothermal fluid through fractured rock is thus essential to the efficient utilisation of New Zealand\u27s deeper geothermal resources which are hosted in greywacke basement and lavas. In this study we investigate the nature of fluid flow for a variety of simple, single-and multiple-fracture arrangements and widths within Taupo Volcanic Zone (TVZ) greywacke basement and andesite hosted reservoirs, making use of known permeabilities. We present preliminary numerical models of fluid flow through a metre-scale sample of rock for a variety of simple fracture networks, with emphasis on the perturbation of the total flow across the sample with respect to that of a non-fractured sample. Later work will focus on the changes in fracture properties that influence the flow through these samples due to far field stresses and varying mechanical behaviour of the reservoir rock and its fractures, and upscaling these results from metre-scale experiments to kilometre-scale reservoirs. Future research will also test the effect on fluid flow of known fracture spacing and width distributions of TVZ geothermal reservoirs