Geochemical and Process Engineering Challenges for Geothermal Power Generation

Abstract

Handling of the geothermal fluid, which is typically a complex mixture of salt solution and dissolved gases, is one of the main challenges for designing and operating reliable and efficient geothermal power plants. In the geothermal fluid loop, undesired mineral precipitation and fluid-material interactions must be prevented and the design and dimensioning of all components must be adapted according to the characteristics of the geothermal fluid. This paper outlines geochemical and process engineering aspects as well as research activities in these fields and introduces the Groß Schönebeck site, which is a central site for geothermal research.

The element-release mechanisms of two pyrite-bearing siliciclastic rocks from the North German Basin at temperatures up to 90 °C under oxic and anoxic conditions

“…Conditions close to the oxic case may either occur in shallow aquifers, or close to the well in deeper aquifers if oxygen leaks into the groundwater during ATES operation. However, nitrogen pressurization, which is common in ATES systems (e.g., Frick et al 2011;Seibt et al 2010), should keep solute oxygen concentrations low. Oxygen leaking into the aquifer would furthermore be consumed by oxidizable solute species, e.g., Fe 2+ , thus reducing solute oxygen available for pyrite dissolution.…”

“…If the ATES system is built in an aquifer that serves as drinking water supply as well, the release of toxic elements such as heavy metals need to be avoided (Bonte et al 2013a, Possemiers et al 2014. Altered water properties may promote corrosion or induce subsequent fluid-rock interactions (Allen et al 1984;Frick et al 2011;Palmer et al 1992). To avoid aquifer damage by clogging, corrosion or contamination, legal regulations in several countries limit the groundwater temperature change to a maximum of 3 to 11 K, as the effects of large temperature variations on dissolution, desorption and microbial communities are still poorly understood (Hähnlein et al 2010).…”

Thermal–hydraulic measurements and modelling of the brine circuit in a geothermal well

“…Production of geothermal fluid Geothermal energy can be exploited by pumping hot geofluid from a deep reservoir to the surface by an pump installed in the wellbore (Frick et al, 2011). The well completion consists of steel pipes cemented to the formation in telescope-like layout (Fig.…”

Geothermal energy – The global opportunity

“…In some areas, geothermal fluids are "mined" for the elements they contain 38 . Managing potentially highly saline fluids that may also contain gas can be a further challenge having developed a geothermal reservoir as their composition may change following changes in pressure and temperature during the process of energy extraction 7 . The presence of some dissolved constituents can heighten environmental concerns associated with the mobilisation of elements from the target formation at depth to higher levels because stresses on the well casing that were exacerbated by poor cementation 45 .…”