Abstract: Numerical Modeling of Secondary
Oil Migration
: Definition of Oil Pathways in Laboratory Scale
Souto Filho, João de Deus - Petrobras/E&P
The process of secondary petroleum migration
is developed at pore scale and is controlled essentially by capillary,
buoyancy and hydrodynamic forces. The intensity of these forces depends
on permoporous system characteristics and fluid physico- chemical properties.
In recent years, petroleum
migration
has been studied in laboratory simulations
and by computer modeling. The data and results presented in this paper
were obtained as one part of a larger study to determine a regional petroleum
migration
model for the Açu Formation, Potiguar basin, Brazil (Souto
Filho, 1994). A procedure for numerical modeling in laboratory scale, in
order to support regional oil
migration
studies, is presented. The numerical
modeling approach focused on matching the oil saturation profiles at different
times, tested by a direct comparison of the results with experimental data.
Figure 1 shows the equipment used in the laboratory study (acrylic columns
96 cm long, with 2.91 cm inner diameter; and high density plastic pipe
200 cm long, with a 3.72 cm inner diameter). The experiments were prepared
with the technique used by Catalan, et al. (1992), using quartz sand grains
of fluvial deposits. Table 1 lists the physical properties of porous media,
fluids and the mean
migration
rate of the oil front obtained for the different
grain size. We studied the vertical and lateral
migration
process. In both
cases
migration
was found to take place along restricted pathways, and
we confirm the Catalan, et al. (1992) results observing an imbibition front
often formed at the bottom of the oil zone. As a second objective of this
work, we replicated the qualitative appearance of oil
migration
front and
fluid distribution observed in the experiments, using 2-D and
3-D
numeric
models. The
migration
was assumed to occur as a diphasic fluid flow governed
by Darcy's law. The oil saturation profiles presented in Figure 2 confirm
that using appropriate relative permeability and capillary pressure curves,
the secondary oil
migration
process can be accurately simulated numerically.
The results show that numerical simulation is a powerful technique to analyze
the evolution of pathways and to identify the main factors that control
the secondary
migration
process in permoporous systems.
Experiment Permeability Oil Density Oil Volume
Initial Oil Migration
(Darcy) (g/cm3) Injected (cm3) Height (cm) Rate (cm/b)
CS-02** 57.600 0.859 46.0 24.5 25.3
CS-05* 24.360 0.861 47.0 25.5 11.6
CS-05e** 34.700 0.861 47.0 23.5 32.6
IMS-02** 0.821 35.0 23.0 08.5
IMS-04* 29.460 0.821 45.0 25.0 09.5
IFS-02**1 10.050 0.821 42.0 25.0 01.3
CS = Coarse Sand; MS = Medium Sand; FS = Fine Sand; (*) Smooth Pipe; (**) Rough Pipe.
Obsengion: The CS-05e* experiment was made by glass spheres.
Table 1 - Experimental Conditions and Migration
Rates for Vertical Oil
Migration
Experiments.
AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil