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CO2 STORAGE

	 Numerical simulations with COMSOL                      FIGURE 3. Time evolution of the different underground trapping mechanisms for the 3
and iCP proved to be very useful for                     locations of the injection wells.
system understanding, showing that
even small changes in the injection well                 FIGURE 4. Reactive fingering of CO2-rich brine due to density instabilities.
location can lead to significantly different
distributions by the trapping mechanisms.                    ABOUT AMPHOS 21
By injecting CO2 farther from the top of
the storage formation, the migration                           AMPHOS 21, a COMSOL Certified Consultant, is the developer of the software interface
of the supercritical plume becomes                             iCP (interface COMSOL-PHREEQC), which provides a flexible and efficient platform for the
higher and the “fast” capillary trapping                       simulation of complex Thermo-Hydro-Chemical-Mechanical (THCM) applications. The iCP
is enhanced, thereby increasing the                            interface allows the powerful multiphysics modeling capabilities of COMSOL Multiphysics®
retention and safety of the CO2 storage.                       to be combined with the leading geomechanical simulator PHREEQC (developed at
	 Solubility trapping, however, is                             the USGS1). This ability is unique among the available coupled reactive solute transport
mostly a function of time and is almost                        software, offering a powerful solution for the accurate modeling of applications in this
independent of the injection location.                         field. More information and technical details about the software are available in a recent
Figure 3 shows the time evolution of the                       article in the journal Computers & Geosciences2.
performance of different underground                           AMPHOS 21 models and simulations for the oil and gas industry:
trapping mechanisms for the three                              •	 4D modeling of porosity and permeability of reservoirs (diagenesis, operation phase, etc)
studied locations of the injection wells.                      •	 Reactive gas flow in shale plays at different scales (from nano to reservoir scale)
	 As shown in Figure 3, the configuration                      •	 Assessment of the effect of geochemical processes in EOR-type application
of denser CO2-enriched brine overlying                         •	 Well integrity studies: degradation of cement under HPHT conditions
relatively lighter water leads to a
convective flow and to the formation
of gravity fingers of dense fluid that
sink deep into the resident brine. Given
the non-linear feedback between
geochemical processes (mineral dissolution
and/or precipitation), porosity and
permeability changes, and density driven
flow, geochemical reactions may affect
fingering and convection patterns. More
importantly, geochemical reactions may
change the total storage potential of the
target geological formation.
	 Detailed studies are also being
conducted to analyze the interaction
between flow and geochemical processes
associated with the dissolution of CO2 in
brine in a carbonated reservoir. Figure
4 shows an example of the reactive
fingering of acidic CO2-rich brine that
leads to non-uniform calcite dissolution
patterns and results in preferential flow
paths that control flow dynamics at later
times. The high-density (CO2-rich) brine
on the top of the reservoir leads to the
sinking of acidic brine that dissolves
calcite and precipitates gypsum. v

REFRENCES

1 Parkhurst, David L., Appelo, C.A.J. “USGS Water-
Resources Investigations Report.” In User’s Guide to
PHREEQC (Version 2). Denver, Colo. U.S. Geological
Survey, 1999.
2 Nardi, A., Idiart, A., Trinchero, P., de Vries, L.M.,
Molinero, J. Interface COMSOL-PHREEQC (iCP), an
efficient numerical framework for the solution of
coupled multiphysics and geochemistry. Computers
& Geosciences 69 (2014): 10-21.
3 Sainz A., Nardi A., Abarca E., Grandia F. Evolution
of trapping mechanisms in deep geological CO2
storage. The International Carbon Conference, vol.
66. www.or.is/sites/ default/files/icc.pdf

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