Sebastian Held

Assessment of performance and parameter sensitivity of multicomponent geothermometry applied to a medium enthalpy geothermal system

The determination of reservoir temperatures represents a major task when exploring geothermal systems. Since the uncertainties of classical solute geothermometry are still preventing reliable reservoir temperature estimations, we assess the performance of classical geothermometers and multicomponent geothermometry by applying them to fluids composed from long-term batch-type equilibration experiments and to fluids from natural geothermal springs in the Villarrica area, Southern Chile. The experiments, weathering two reservoir rock analogues from the Villarrica area, highlight a strong impact of reservoir rock composition on the fluid chemistry and, consequently, on calculated in situ temperatures. Especially temperatures calculated from classical solute geothermometry are strongly affected. Multicomponent geothermometry is obviously more robust and independent from rock composition leading to significantly smaller temperature spreads. In a sensitivity analysis, the dilution of geothermal fluid with surficial water, the pH and the aluminum concentration are anticipated to be the factors causing underestimations of reservoir temperatures. We quantify these parameters and correct the results to obtain realistic in situ conditions. Thus, enabling the application of the method also on basis of standard fluid analysis, our approach represents an easy-to-use modification of the original multicomponent geothermometry leading to very plausible subsurface temperatures with significantly low scattering.

Case Study: Soultz-sous-Forêts

The second case study is given for Soultz-sous-Forets site in France, which represents an enhanced hydrothermal type of EGS reservoirs. Input files for the simulations are available from https://docs.opengeosys.org/books/geoenergy-modeling-iii. Please note that the Soultz data provided can only be used for the scope of this tutorial book and that especially commercial purposes are not allowed.

Open-Source Software

Software used in the later benchmark examples and case studies are introduced. All of them are open-source and freely available for scientific research purposes.

Case Study: Groß Schönebeck

In the following two chapters, we demonstrate how the numerical simulation can be applied to actual reservoir analysis. The first case study is given for the Gros Schonebeck research site in Germany, which represents a hot sedimentary aquifer type of EGS reservoirs. Input files for the simulations are available from https://docs.opengeosys.org/books/geoenergy-modeling-iii.