Numerical Simulation of In-situ Combustion in a Fracture-Porous Medium System - Selected Topics of Computational and Experimental Fluid Mechanics - page 316

Currently, a large amount of petroleum is in naturally fractured reservoirs. This has
leaded to develop theoretical and experimental works for gaining knowledge about
the effects that fractures have on the thermal and hydrodynamic performance of the
ISC (Awoleke et al. 2010 ; Greaves et al. 1991 ; Schulte and de Vries 1985 ). Most of
these works agree that the oxygen transport is one of the main phenomena to sustain
and propagate the combustion front. Thus, oxygen dispersion from fracture to matrix
plays a crucial role for the ISC inside the porous medium. Despite the theoretical
and experimental research that has been done, the ISC behavior in fracture systems
is no clear nowadays.
In this work, we simulated one experiment of the ISC process in a combustion tube
filled with a homogeneous system (Kumar 1987 ) obtaining an excelent fitting. Later,
the simulation model was modified in order to include fractures. This model was
compared against the conducted simulation by Tabasinejad et al. ( 2006 ) obtaining
also excellent fitting. The last model was used to evaluate the effect of air flow rate
and the oxygen diffusion from fractures to porous medium.

2 Governing Equations, Boundary and Initial Conditions

The general model, for multicomponent multiphase flow (gas, oil and water) in
porous media used in this work, is presented below:

Mass conservation equation

w ˆ

S a ˁ ʱ ˉ i ʱ ∂

ʱ = g , o ,

( 1 − ˃ ) =−∇·

w ˁ ʱ

D ∇ ˉ i ʱ −∇· (ˁ i ˉ i ʱ u

ʱ )

ʱ i

∂ t

ʱ = g , o ,

ʱ = g , o , w ˉ i ʱ q ʱ

+ r i ʱ + i = 1 ,..., n c .

ʱ = g , o , w

(1)

Energy equation

ʱ = g , o , w ˆ

− ˆ) ˁ s C s T

∂
∂

S a ˁ ʱ U ʱ + ( 1

t

+∇·

w ˁ ʱ u ʱ H ʱ −∇· (

k T ∇ T ) = q c − q L (2)

ʱ = g , o ,

where

kk r ʱ
μ ʱ

u ʱ =− ( ∇ p ʱ − ˁ ʱ g ) (3)

n c n c

A i ˉ i = B i ˉ i (4)

i = i = 1 1