The Analyses of Fluid Flow and Reactive Transport Processes for a Supercritical Geothermal System
Guanhong FENG, Tianfu XU, Zhenjiao JIANG, Fugang WANG
[Jilin University, China]
Beyond the critical point of 373.96oC and 22.1MPa, water presents in supercritical state with high density and low viscosity, which is beneficial for geothermal resource development and utilization. According to Cladouhos et al (2018), at a 60kg/s mass injection rate the energy production of supercritical water at 400oC is almost 10 times larger than that at 200oC. Supercritical geothermal development is getting more attention recent days. However, higher temperature could result in more serious water-rock reactions, affecting the permeability and heat extracting behavior. There is little analysis on super-critical geothermal development, especially on geochemical aspect. In this work, we develop a multi-phase flow and reactive transport code for supercritical geothermal systems based on the existing structure of TOUGH2 and TOUGHREACT. IAPWS-IF97（International Association for the Properties of Water and Steam, 2007）is used for calculations of water thermodynamic properties. It can cover the T-P range up to 800oC and100MPa, and the temperature limit can even extend to 2000oC if pressure lower than 50MPa. For the reactive transport modeling, the largest challenging is the lack of equilibrium constants at high temperature ( more than 300oC) for minerals and aqueous species. In this work, SOLTHERM-2011.XPT is introduced, which is developed by Mark Reed and Jim Palandri. It provides the equilibrium constants for minerals and aqueous species under the condition of the density of water larger than 350 kg/m3. The Icelandic Deep Drilling Project (IDDP2) is taken as an example to illustrate flow and reactive processes and the heat extraction performance for cold water injection into a supercritical geothermal system.
|        Topic: Software for Geothermal Applications||Paper Number: 33009|