Geoscience Reference
In-Depth Information
Table 4.3
Summary of selected studies comparing multi-scale factors on petroleum reservoir performance
Shallow
Marine
a
Faulted Shallow
Marine
b
Fault
modelling
e
Fluvial
c
Tidal Deltaic
d
Sequence model
V
V
V
Sand fraction
S
S
V
S
n/a
Sandbody geometry
S
S
n/a
Vertical permeability
S
S
V
n/a
Small-scale heterogeneity
S
S
n/a
Fault pattern
n/a
S
n/a
n/a
S
Fault seal
n/a
S
n/a
n/a
S
V
Most significant factor,
S
Significant factor,
n/a
not assessed
a
Kjønsvik et al. (
1994
)
b
England and Townsend (
1998
)
c
Jones et al. (
1993
)
d
Brandsæter et al. (
2001a
)
e
Lescoffit and Townsend (
2005
)
Gravity-dominated
Fluid
segregation
Sequence
REV
Capillary trapping
and S
or
Lithofacies
REV
Lamina REV
Viscous
fingering and
channeling
Capillary-dominated
Viscous-dominated
10
-12
10
-11
10
-10
10
-9
10
-8
10
-7
10
-6
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
10
1
10
2
10
3
10
4
Measurement Volume [m
3
] (log scale)
Fig. 4.29
Sketch illustrating the expected dominant fluid forces with respect to the important heterogeneity length-
scales
context of oilfield developments. An ambitious
study of the structurally complex Gullfaks field
(Jacobsen et al
2000
) demonstrated that 25
million-cell geological grid (incorporating struc-
tural and stratigraphic architecture) could be
upscaled for flow simulation and resulted in a
significantly improved history match. Both strat-
igraphic barriers and faults were key factors in
achieving improved pressure matches to historic
well data. This model was also used for assess-
ment of IOR using CO
2
flooding.
Multi-scale upscaling has also been used to
assess complex reservoir displacement pro-
cesses, including gas injection in thin-bedded
reservoirs
alternating-gas (WAG) injection on the
Veslefrikk Field (Kløv et al
2003
), and depres-
surization on the Statfjord field (Theting et al
2005
). These studies typically show of the order
of 10-20 % difference in oilfield recovery factors
when advanced multi-scale effects are
implemented, compared with conventional
single-scale reservoir simulation studies. For
example, Figure
4.31
shows the effect of one-
step and two-step upscaling for the gas injection
case study (illustrated in Fig.
4.30
). The coarse-
grid case without upscaling gives a forecasting
error of over 10 % when compared to the fine-
grid reference case, while the coarse-grid case
with two-step upscaling gives a result very close
to the fine-grid reference case.
(Fig.
4.30
)
(Pickup et al
2000
;
Brandsæter
et
al.
2001b
,
2005
), water-
