10.4122/1.1000000659
Kuehn, Michael
Michael
Kuehn
m.kuehn@geophysik.rwth-aachen.de
Vosbeck, Katrin
Katrin
Vosbeck
vosbeck@iml.rwth-aachen.de
Back, Martin
Martin
Back
martin.back@uni-bayreuth.de
Clauser, Christoph
Christoph
Clauser
c.clauser@geophysik.rwth-aachen.de
Stanjek, Helge
Helge
Stanjek
stanjek@iml.rwth-aachen.de
Peiffer, Stefan
Stefan
Peiffer
s.peiffer@uni-bayreuth.de
Kuehn, Michael
Michael
Kuehn
m.kuehn@geophysik.rwth-aachen.de
CO2 storage through mineral trapping in geothermal reservoirs
XVI International Conference on Computational Methods in Water Resources
2006
2006
Costs for carbon dioxide sequestration into deep saline aquifers can be transformed
into a benefit when combined with ecologically desirable geothermal heat or power
production. The produced energy can be used and marketed. Aim is a scientifically
and technically feasible new technology to achieve a safe and economically
attractive long-term storage of CO2 trapped in minerals. We develop, study, and
evaluate a novel approach not only to sequester CO2 by physical trapping within a
reservoir, but to convert dissolved CO2 into the geochemically more stable form of
calcite.
Due to the geological situation exploitation of geothermal energy in Germany is
mainly provided from deep aquifers. The common arrangement of bore holes is the
well doublet, consisting of one well for hot water production and one well for
cooled water re-injection. The cooled water is loaded with dissolved CO2, and after
re-injection into the reservoir this cold water becomes enriched in calcium e.g.
due to dissolution of anhydrite (CaSO4). Subsequently CO2 precipitates as calcium
carbonate (CaCO3), provided that alkalinity is present either by the dissolution of
feldspars in the aquifer or by surface water treatment with fly ashes.
Processes are studied both in laboratory and by numerical simulations. The latter
are essential to quantify the entire process of CO2 storage and to deepen the
understanding of the detailed chemical processes. Reaction modelling and reactive
transport simulations are done on multiple scales since the combination of all
scales is not feasible in numerical models up to now. The relevant scales studying
CO2 storage in combination with geothermal energy production reach down from the
reservoir scale (ca. 10 km) to the micro scale (ca. 1 cm). Results from larger
scale models provide constraints for smaller scale scenarios. For processes which
cannot be resolved on the larger scale, due to restrictions of discretization of
the applied numerical mesh, functionalities are derived from the smaller scale. To
be predictive and capable of quantifying amounts of storable CO2 numerical
investigations on the reservoir scale are vital. Simulations on the borehole scale
are necessary, because the near vicinity of wells is vulnerable to permeability
decrease as a result of mineral reactions. Laboratory experiments are used to
calibrate the numerical tools and simulations on the micro scale allow further
investigation of the overall process of mineral dissolution and precipitation.
Simulation results as well as laboratory experiments prove that anhydrite can be
successfully transferred into calcite and thus are evidence for the feasibility of
the new technology.