Numerical simulation of reactive transport was validated in a core flooding experiment simulating conditions in a managed geothermal reservoir. Permeability was measured along a sandstone core prepared with anhydrite and subjected to a temperature gradient. Anhydrite was dissolved and precipitated in the cold upstream and hot downstream regions of the core, respectively. The numerical code SHEMAT was used to simulate coupled transport and chemical reactions at the temperature front (http://www.rwth-aachen.de/geop/shemat/). It comprises an extended version of the geochemical speciation code PHRQPITZ for calculating chemical reactions in brines of low‐high ionic strength and temperatures of 0–150°C. Permeability is updated to porosity via a novel, calibrated power‐law based on a fractal pore‐space model resulting in a large exponent of 11.3. Simulation results agree well with measured permeability. This both validates the model and demonstrates that the fractal relationship is crucial for a successful simulation of this type of reactive transport.
A gas chromatographic technique has been worked out which allows
one to determine the kinetics
of the formation and decomposition of sulfanes in the sulfur−hydrogen
sulfide system at high
temperature. Quantitative kinetic data are of great importance not
only for research in that
field but also for various practical applications like, for example,
the sulfur deposition problem
in sour gas reservoirs. Kinetic measurements have been carried out
at different constant
temperatures in the range of 120−270 °C in a chromatographic
reactor, containing sulfur-coated
glass beads and quartz powder, respectively. In order to determine
the kinetic parameters, a
numerical model of the gas chromatographic reactor has been developed.
Based on the results
obtained by fitting the experimental chromatograms to the model, a
simplified reaction scheme
is proposed. Preliminary results show that sulfane decomposition
in the sulfur/H2S system is
a rather slow reaction.
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