Environmental Engineering Reference
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results fairly follow the tendency of experimental data in spite of simplifications
assumed in the mathematical model. Other comparisons of relevant variables such
as: oil, water and oxygen production, combustion front location and produced oil
gravity were carried out with good agreement. However, such comparisons were
omitted here for the sake of brevity.
4 The Matrix-Fracture Case
Comparison of temperature profiles for the benchmark case, and that one where
1mm adjacent fracture is added, are plotted in Fig.
2
. As one
small
fracture is con-
sidered, heat transport is not strongly affected by the channelization phenomenon as
effective thermal properties, as heat capacity and thermal conductivity, do not vary
significantly in the matrix and fracture. However, effective transport properties, as
mass dispersion and permeability, are very contrast. This leads to one marked effect
of fracture over phase flows and oxygen availability, as shown later.
Figure
3
shows the oxygen and oil fluxes at the porous-fracture boundary as func-
tion of time, when a fracture is adjacent to the porous matrix (the heterogeneous
case). Larger values indicate that coke combustion is taking place at that position.
As convention, a positive flux indicates that there is mass transport from the matrix
to the fracture, and the opposite is true. At the vicinity of combustion front, there is
high oxygen consumption, because of the coke combustion, and more oxygen must
be feed from the fracture, where there is more oxygen available than in the matrix
(see Fig.
4
).
At surroundings of the combustion front, significant oxygen concentration gradi-
ents take place and, as this is the driving force for diffusive mechanisms, then the
matrix microstructure (tortuosity and porosity) plays a crucial role to facilitate y the
Fig. 2
Comparison of temperature profiles between the benchmark case and the fracture case
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