Reactive transport models couple a large number chemical reactions with mass transport. Certain applications, such as geothermal energy production and ore deposit modeling, require the additional calculation of heat transfer. In modeling carbon sequestration and hydraulic fracturing, moreover, it may be necessary to describe rock deformation resulting from mineral growth or abnormally high fluid pressure. Description of transport through the unsaturated zone and multiphase flow modeling, as applied to transport of petroleum and natural gas; non-aqueous phase liquids (DNAPL or LNAPL); and supercritical carbon dioxide requires increasingly complex models which are prone to considerable uncertainty.
In many cases the processes simulated in reactive transport models are highly related. Mineral dissolution and precipitation, for example, can affect the porosity and permeability of the domain, which in turn affect the flow field and groundwater velocity. Heat transport greatly affects the viscosity of water and its ability to flow. Below are many of the physical and chemical processes which can be simulated with reactive transport models.
Geochemical reactions:
*Acid-base reactions
*Aqueous complexation
*Mineral dissolution and precipitation
*Reduction and oxidation (redox) reactions, including those catalyzed by enzymes, surfaces, and microorganisms
*Sorption, ion exchange, and surface complexation
*Gas dissolution and exsolution
*Stable isotope fractionation
*Radioactive decay
Mass Transport:
*Advection
*Molecular scale diffusion
*Hydrodynamic dispersion
*Colloid-facilitated transport
Heat transport:
*Advection
*Conduction
*Convection
Medium deformation:
*Compression or expansion of the domain
*Fracture formation