|Abstract:|| Tracer methods represent techniques commonly used for the characterization and for the monitoring of
transport processes in geo-reservoirs (e.g., CO2 storage, geothermal systems, oil recovery, etc.).
Our current research efforts focus on the development of a new class of reactive tracers, i.e. KIS tracers
useful for the characterization of fluid-fluid interfacial areas during supercritical CO2 injection into deep
saline aquifers. The amount of fluid-fluid interfacial areas is important for the quantification of reactions
at the fluid interface, which can implicitly lead to optimized injection strategies, a better assessment of
the extent of the CO2 plume and of the storage efficiency. The work involves multi-disciplinary
collaboration including laboratory experiments, synthesis of new tracer compounds and numerical
modelling at pore- and continuum-scale.
The presentation focuses on the development of a conceptual, mathematical and numerical model for
the KIS tracers in porous media. The presented modeling approach overcomes the drawback of the
current standard multiphase multicomponent models, which ignore kinetics of mass transfer over the
interfacial area between the CO2 and brine and consider only the volumetric fraction of the fluids or
their mass and molar fractions, respectively. In this model, the concept of a specific interfacial area
obtained from pore network modeling is used to complement the constitutive relationships between
capillary pressure and saturation. It is a two-phase four component flow and transport model with a
kinetic mass transfer of tracers between the two fluids and taking the dissolution of CO2 in brine into
account. The modeling approach uses parameters obtained from experimental lab work. Their
implications are investigated by sensitivity analyses to narrow the physical range of reaction rates for
further experiments and molecular tracer design.