Environmental Engineering Reference
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the possibility of success. To study the phenomenon at core-scale, combustion
tubes and simulators are used to investigate the formation and propagation of a
combustion front.
In ISC experiments there are several phenomena with engineering interests. One
of them concerns the oxygen transport into the reservoir in order to reach zones with
fuel for further reaction and heat releasing. Using in-situ combustion tubes, experi-
mental efforts have been done to understand the main mechanisms and phenomena
controlling the ISC. To quote some examples, Moore and coworkers have developed
extensive investigations at lab-scale and simulations for various types of operations,
geometrical configurations and oils (Alamatsaz et al.
2011
; Montes et al.
2010
).
In reservoirs with heterogeneous characteristics such as fractured systems, the
transport of phases and components is different in comparison with homogeneous
media. Due to phases move preferably by fractures, fluids breakthrough appears
and oxygen transport from fractures to the porous matrix plays a crucial role for
the propagation of the combustion front. To broaden the understanding of ISC in
fractured systems, some theoretical (Fatemi and Kharrat
2008
; Schulte and Vries
1985
) and experimental (Awoleke et al.
2010
; Greaves et al.
1991
) efforts have been
made. Nevertheless, the complex nature of ISC involving simultaneous heat, mass
and momentum transfer between phases, thermodynamic restrictions and chemical
reactions, suggests further investigations for the sake of gaining more knowledge
applicable to actual field-scale reservoir conditions.
Based on published works so far, it seems that fractures in ISC processes hin-
der the propagation of the combustion front and eventually the burning process is
extinguished. The oxygen availability in the burning zone may play a crucial role,
and such a feature is highly influenced by the contrast of fluids mobility between the
porous matrix and fracture. Thus, in this work we focus on the numerical investi-
gation of the effect that one fracture adjacent to one porous matrix has over an ISC
process. The study is carried out at 2D lab-scale (combustion tube), and profiles of
most relevant variables are presented and discussed.
2 Theoretical Model
In this study a three-phase, six-component ISC model was implemented. Table
1
shows components and phases taken into account in the model.
The mathematical model comprises the mass balance for oil- (
o
)
,gas-(
g
)
and
water-phases (
w
)
as follows,
∂ (ˆˁ
ʱ
s
ʱ
)
∂
+∇·
(ˁ
ʱ
u
ʱ
)
=
q
ʱ
,ʱ
=
o
,
g
,
w
,
(1)
t
ˆ
ˁ
where
and
s
are density and saturation, respectively.
q
is the
mass source/sink due to exchange between phases or chemical reactions. The phase
velocity
u
is computed according to Darcy's Law,
is porosity, and
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