Exploring Utilization Scenarios for Supercritical Wells Using 3D Geothermal Reservoir Modelling
Alina YAPPAROVA, Benoit LAMY-CHAPPUIS, Sigrun TOMASDOTTIR, Gunnar GUNNARSSON, Thomas DRIESNER
[ETH Zurich, Switzerland]
The IDDP 1 and 2 wells detected supercritical resources beneath the conventional, high-enthalpy geothermal resources at Krafla and Reykjanes, Iceland. However, developing such resources has remained a major technical challenge and it is at present unclear what the optimal utilization strategy might be - direct production of superheated steam, injection in order to enlarge the resource by recharging from superheated zones below, or multi-well operation schemes. Numerical reservoir simulation could help assessing this question but current industry standard software tools are not yet ready to perform such simulations. Including deep magmatic heat sources and resulting temperature-dependent permeability distributions have remained challenging, and therefore heat and fluid fluxes at bottom boundary are often used in reservoir models of high temperature geothermal fields. We have augmented the Control Volume Finite Element Method (CVFEM) scheme of the CSMP++ software framework (Weis et. al., 2014) that has previously been used to perform 2D simulations of supercritical resources (Scott et al., 2015). The augmented version can simulate full 3D geothermal reservoir processes including explicit representation of underlying hot magma bodies, depth and temperature dependent host rock permeability and can extend to 5-10km below the surface. This allows for more detailed and geologically constrained models. Moreover, a simple semi-analytical Peaceman well model (Chen, 2007) has been implemented in the CVFEM scheme in order to be able to simulate different utilization scenarios. The need for a well model is necessitated by the fact that the reservoir pressure undergoes most rapid changes in the immediate vicinity of the well, and without such model only extreme mesh refinement near the well can capture those changes. The 3D CVFEM scheme with an embedded well model has been applied to explore the possible utilization scenarios for deep geothermal wells tapping supercritical resources in Iceland. This paper presents a summary of the pros and cons of different utilization scenarios and discusses the remaining uncertainties of the modelling approach, many of which relate to unknown material properties (permeability, existence of feed zones etc.) at superheated conditions.
|        Topic: Software for Geothermal Applications||Paper Number: 33031|