Research Projects and Publications

Numerical Modelling of Cold Water Injection into Supercritical Geothermal Reservoirs

Author:  Riley S. Newman
Year: 2018
Supervisors:  Juliet Newson, Michael O’Sullivan and John O’Sullivan


As concern grows regarding the environmental impacts of human-induced climate change, there is a rising clamour for reducing the pervasive global dependence on fossil fuels in favour of renewable energy sources and the promotion of sustainable exploitation of the Earth’s resources. Geothermal energy is a renewable energy resource found in the reservoirs of high temperature geothermal systems. In broad terms a high temperature geothermal system is comprised of a multitude of processes which redistribute heat and mass via fluid flow, driven by thermal energy from hot magmatic heat sources deeper in the subsurface. Despite the necessity of the heat source for the existence of an exploitable geothermal resource, the nature of these geothermal roots is not well understood. The increased interest in geothermal heat sources is not merely based on improving the scientific understanding of these natural systems, but also due to the hypothesised increased power production potential of supercritical fluids found proximate geothermal heat sources. In response to burgeoning interest in understanding supercritical geothermal resources, developing numerical models that represent the complex interplay of thermal and fluid movement in these systems is of utmost importance. The aim of this study is to apply the improved supercritical air-water equation-of-state of the AUTOUGH2 numerical simulator to an artificial supercritical geothermal reservoir. A radially symmetric numerical model is used to investigate the response to cold water injection of a geothermal reservoir with conditions analogous to the first measured conditions in the second well of the Iceland Deep Drilling Project (IDDP-2). The IDDP-2 well was completed in January of 2017 and subsequently stimulated with cold water injection. Deep wells such as IDDP-2 represent potential opportunities for revitalising aging geothermal fields with deep re-injection or creating enhanced geothermal systems by injecting working fluids into fractured supercritical domains. Understanding the response of a supercritical reservoir to cold injection, and the processes occurring near the wellbore are the first steps towards achieving these advances in geothermal energy utilisation worldwide.