Using Decision Support Models to Analyse the Performance of EGS Systems

Abstract

In this study we present a techno-economic performance assessment model for deep geothermal projects. These models are a public deliverable of the European project Enhanced Geothermal Innovative Network for Europe (ENGINE), which has been completed spring 2008. The models have been implemented in EXCEL and as part of dedicated decision support system, using best practices for asset evaluation from the Oil and Gas industry. This approach allows to take into account natural uncertainties and decision trees to evaluate sensitivities and different scenarios.

In the model approach, fast model calculations for the techno-economic evaluation are used to calculate the performance of the geothermal systems, investigating sensitivities of the performance due to both natural uncertainties beyond control (e.g. flow characteristics, subsurface temperatures), engineering options (bore layout and surface facilities options) and economic uncertainties (e.g. electricity price, tax regimes). Fast models for the temperature evolution of the water in the well and fractures are based on fast analytical solutions, based on streamline approximations. This allows to calculate in a matter of seconds the performance and its sensitivity to uncertainties and the effect of various engineering options.

For doublet systems in deep (enhanced) geothermal systems we use analytical methodologies developed for the Soultz project. Results show that the performance of the system is primary sensitive to subsurface temperature, flow rates which can be sustained in the fractured rock, and the number of fractures involved in the fluid flow. We also are capable to forecast effects of improved explorative approaches and technological performance as well as governmental incentives on viability of prospects. The tools are available at http://engine.brgm.fr/DecisionSupportSystem.asp.