Modeling of high temperature, high pressure geothermal energy production system

A significant source of renewable energy is hot water/steam at high pressure from reservoirs in the earths crust, which can be utilized for e.g. electricity production. The project has instigated solid particle generation from dissolved minerals (SiO2 particles generated from dissolved H4SiO4) when temperature and pressure is reduced in process equipment. Mathematical models for particle formation and subsequent growth have been established, and have been combined with theoretical models for deposition of such particles onto solid surfaces such as in pipes and valves. As part of the project, a test rig for measuring SiO2 particle deposition from superheated steam onto a tube wall was developed, and a test program was performed with the purpose of validating the developed models. The measurements are in qualitative agreement with the models, but there is a further need to improve on the measurement accuracy and further develop the prediction models.

Med de etablerte metodene for mineralutfelling ved trykkavlastning er det mulig å kvantifisere ved hvilke trykk utfelling kan forventes, samt partikkelkonsentrasjoner og størrelsesfordeling. Dette vil gi bidrag i systemdesign og tekniske løsninger for utstyr for kraftproduksjon/varmeekstrahering fra damp fra dype geotermiske brønner.

High pressure and high temperature hydrothermal geothermal resources represent a large energy source that can be utilized for e.g. power production both onshore and offshore, benefiting from Norway's leading competence in drilling and subsea oil/gas production. Due to high pressure and high temperature, the water chemistry may contain significant amounts of dissolved minerals which may precipitate during cooling/pressure relief and deteriorate or damage vital components in the power production system. The major goal of the project is to provide knowledge and predictive methods for the precipitation behavior, and propose mitigation methods. This will in turn enable the design of robust power production systems. Different power production systems, based on direct use of the well fluid or indirect use by heat exchange will be analyzed with respect to feasibility and efficiency. Major project activities are: - Modeling of the well fluid properties as function of pressure and temperature (significantly higher than today's conventional hydrothermal systems), particularly with respect to mineral and gas solubility, - Experimental validation of vital fluid properties, - Feasibility analysis of power production systems having direct well fluid usage in the turbine or indirect usage through heat exchangers. Available information from the Iceland Deep Drilling Project will be used in the project. The outcome of the project will provide vital knowledge on the well fluid behavior in a power production system such as potential problems associated with mineral/salt precipitation, corrosive components, solidified particle erosion, which is required for the successful development of robust end efficient power production systems.