Modelling Feedback of Chemical Reactions on Flow Fields in Hydrothermal Systems

Abstract

Coupled reactive transport models of hydrothermal systems provide new insights and deeper understanding of the processes occurring due to fluid flow, heat transfer, solute transport, and chemical reactions. Basic concepts of species transport (diffusion, dispersion, and advection) and chemical precipitation and dissolution reactions are discussed, and five end-member types of reactive transport environments are introduced. One of these reactive transport environments, named 'reactions within thermal gradients', is used to demonstrate how free thermal convection can lead to redeposition of minerals and, due to the feedback of reaction on the flow field, a change of the convection pattern. The direct consequence of changing the flow field is a significant variation of the temperature distribution within the modelled area. With the example it is shown how reactive transport simulation can be applied for the detailed study of fossil and recent hydrothermal systems.

Copper precipitation as consequence of steel corrosion in a flow-through experiment mimicking a geothermal production well

“…However, none of the currently existing models satisfy all of these requirements (Kühn 2004;Zhu and Anderson 2002). Therefore, especially simplified models have to be applied due to limited data sets (Kühn 2009;Walter et al 1994). The simplification within the presented study is the approach to quantify the development of the iron and copper concentrations in solution of the laboratory experiments just by a kinetically controlled corrosion and dissolution reaction of iron and a thermodynamically governed precipitation of copper as secondary phase.…”

“…Even though the Debye-Hückel theory for calculating ion activities in solution is inaccurate for highly saline brines, there was no choice because the Pitzer formalism applicable for those brines is not available for redox reactions (Kühn 2009). However, it was shown before that the ferrous and ferric system can be accurately described based on Debye-Hückel even in geothermal brines (Kühn et al 1998).…”

Reconstruction of rocks petrophysical properties as input data for reservoir modeling

“…The simulations were performed by the Simulator for HEat and MAss Transport (SHEMAT code V.7.1) [ Clauser , ]. SHEMAT solves coupled problems involving fluid flow, heat transfer, species transport, and water‐rock interaction [e.g., Gessner et al ., ; Kühn , ; Kühn and Gessner , , b] in a wide variety of thermal and hydrogeological problems [e.g., Kühn et al ., ; Kühn and Stöfen , ; Kühn and Günther , ].…”

Coupled Process Models of Fluid Flow and Heat Transfer in Hydrothermal Systems in Three Dimensions

“…Titley 1990). However, hydrogeologists rarely incorporate time-dependent permeability in quantitative analyses of groundwater flow and transport (see Kühn 2009, this volume for application of time dependent permeability).…”