a sensitivity study on low salinity...
TRANSCRIPT
Modern Environmental Science and Engineering (ISSN 2333-2581) April 2017, Volume 3, No. 4, pp. 231-236 Doi: 10.15341/mese(2333-2581)/04.03.2017/003 Academic Star Publishing Company, 2017 www.academicstar.us
A Sensitivity Study on Low Salinity Waterflooding
Barham S. Mahmood1, Jagar Ali2, Shirzad B. Nazhat2, and David Devlin2
1. Department of Petroleum Engineering, Koya University, Kurdistan Region, Iraq
2. Department of Petroleum Engineering, Soran University, Kurdistan Region, Iraq
Abstract: It is widely accepted that different salinity brines injection may increase the oil recovery. However, the mechanisms by which low salinity flooding increases oil recovery are not yet fully understood. This work is to run simulation on ECLIPSE 100 simulator to show the effect of injecting low salinity into a reservoir. A three dimensional synthetic model was created to mimic a real reservoir. The effect of low salinity on oil recovery was observed by conducting sensitivity study on; injecting brine salinity, slug injection of low salinity, and endpoint saturations. A difference of 22% in oil recovery observed when the low salinity water is injected compared to the high salinity water only in the threshold range between 0 kg/m3 to 5 kg/m3.
Performing slug injection can reduce the requirement for low salinity water and recovers approximately the same percentage of oil. This can indeed give better cost saving when opting for low salinity injection.
The brine option in ECLIPSE 100 indicated to be very sensitive to the saturation endpoint and relative permeability. Thus, it is important to be aware of this during simulation of such augmented waterflooding, and input from experimental data is needed for accurate simulations.
Key words: improved oil recovery, low salinity waterflooding, Salinity, Slug injection, wettability
1. Introduction
The concept of injecting low-salinity water (LoSal)
into the oil reservoir is not a new topic. The first
observation of the LoSal effect on oil recovery goes
back to Martin (1957) and Bernard (1967), who
demonstrated that the injection of fresh water can
improve the macroscopic sweep efficiency in
sandstone containing clay due to mobilization of fine
clay particles [1, 2]. However, this work did not draw
the attention of the oil industries. Three decades later a
new phase of research activities initiated to optimize
the composition of injected water during waterflooding
and its effect on oil recovery enhancement. The
literature on low salinity waterflooding has
increasingly become rich in last few year [3-13] are
among the numerous studies which have been
Corresponding author: Jagar Ali, Researcher, research
areas/interests: reservoir simulation, history matching, petrophysics, reservoir characterization. E-mail: [email protected].
published during last 10-15 years. In these studies
many different microscopic mechanisms behind low
salinity waterflooding process have been proposed.
However, there is not an agreement on the primary
mechanisms that work to enhance oil recovery.
Tang and Morrow in their experiments on LoSal
waterflooding identified the movement of fine clay
particles. According to their understanding when
contacted with low salinity brine, clay particles detach
from the pore walls, as a result an intermediate wet
phase becomes unstable and attains the ability to detach
from the surface of the rock and expose the water wet.
They also reported that when the salinity of the injected
brine is less than 1550 TDS this causes a reduction in
permeability [5]. However, in the experiment
conducted by Lager et al. seems to have witnessed the
low salinity effect even without fines migration or
reduction in permeability [10].
The studies [8, 10-15] on LoSal waterflooding have
demonstrated experimentally the low salinity effect on
the pH value, claiming an increase of pH. This rise in
232
the pH could
dissolution a
a reduction i
in a highe
waterfloodin
waterflood.
reduces the
water and oi
toward more
Lager et a
(MIE) to b
improved oi
same view i
experiments
been observ
salinity brin
interaction
magnesium
connate brin
Mg2+, the M
adsorbed by
Expansion
possible mec
waterfloodin
layer effect
electrical d
interfaces; i
potential. T
repulsion be
to a desorpti
an increase i
Hence, th
Oil Simulato
and recorde
work and th
logical mann
2. Synthet
Three di
using ECLIP
by 50×50×6
d be due to tw
and cation ex
in the H+ ion
er pH. Con
ng would sta
In addition to
surface ten
il reservoir, a
e water wet
al. claimed m
be the major
il recovery b
is held by B
s on the Nort
ved that the
ne, the rock su
resulted in
Mg2+ ions.
nes containe
Mg2+ ions w
y the clay part
n of the elec
chanism to im
ng. Ligthelm
t, which is
double layer
ncreases in t
This in turn y
etween the cla
ion of oil com
in water wetn
his research w
or. A differen
d. The input
his will help
ner.
tic Model a
imensional s
PSE 100. The
grids. Each g
A Sen
wo chemical r
xchange. This
ns in the liquid
sequently, th
art performin
o the fact tha
nsion betwee
also, it chang
multi-compon
r mechanism
by LoSal wa
BP. After carr
th Slope core
interaction
urface and th
a sharp re
Although bo
ed a similar
was believed
ticles in the ro
ctrical double
mprove oil re
m et al. discu
the expansio
between th
the absolute
yields increa
ay particles an
mponents from
ness [14].
will use ECL
nt sensitivity c
ts based on p
p to run the
nd Propert
simulations
e synthetic mo
grid measures
nsitivity Study
reactions: Car
s process lead
d phase, resul
he low sali
ng as an alka
at LoSal floo
en the forma
es the wettab
ent ion excha
m leading to
aterflooding.
rying out sev
e samples, it
among the
he crude oil.
eduction of
oth injected
composition
d to be stron
ock matrix [1
e layer is ano
ecovery by Lo
ussed the do
on of the i
he clay and
level of the
ased electros
nd the oil, lead
m the surface
LIPSE 100 B
case will be te
previous rese
simulations
ties
were perfor
odel is sector
s 3 m × 3 m ×
y on Low Sal
rbon
ds to
lting
inity
aline
ding
ation
bility
ange
the
The
veral
t has
low
This
the
and
n of
ngly
10].
other
oSal
uble
ionic
oil
zeta
tatic
ding
e and
Black
ested
arch
in a
rmed
rized
3 m
in X
hete
to 5
0.30
hav
diag
wel
they
volu
T
wat
kg/m
for
acti
curv
diff
LSA
a co
The
with
high
corr
extr
for
wei
rela
wer
(Fig
3. S
T
perf
Fig.synt
inity Waterflo
X, Y and Z d
erogeneous, t
525 mD and
05. Two acti
ve been adde
gonally with
lls are compl
y are set to
ume rate (RE
The active ph
ter. The salin
m3 (TDS), thi
regular sea w
ivated, two d
ves should b
ferent salini
ALTFNC key
onstant that re
e value of the
h a constant
h salinity
responding c
reme of low
any fraction
ighting factor
ative permeab
re taken from
g. 2) [16].
Sensitivity
The main s
formed in thi
. 1 Permeabthetic model.
ooding
directions, re
the permeabi
the porosity
ive wells; a p
ed to the mo
respect to e
leted from th
be controlle
ESV), with a f
hases in the re
nity of connat
is is approxim
water. When th
different sets
be assigned
ties; high
yword is auto
epresents the
e weighting f
weighting fr
properties
constant of “
salinity floo
n ranging b
r is used, resp
bility profile
m Kossac Chu
Analyses
sensitivity s
s paper are th
bility distribut
espectively. T
lity range is
range is betw
producer and
odel and they
each other (F
he top to the
ed by the re
flow rate of 1
eservoir mode
te water was
mately the sam
he LOWSAL
s of relative
with respect
and low s
omatically us
assigned spe
factor ranges
raction of “0
to be a
“1” represen
ods. Interpola
etween 0 an
pectively. In th
for high and
uck, Schlumbe
studies that
he injection o
tion and well
The model is
between 275
ween 0.23 to
d an injector,
y are located
Fig. 1). Both
e bottom and
eservoir fluid
100 m3/day.
el are oil and
set to be 35
me salinity as
LT keyword is
permeability
t to the two
alinity. The
sed to choose
cific salinity.
s from 0 to 1
0”, indicating
assigned. A
nts the other
ation is made
nd 1, and a
his study, the
d low salinity
erger advisor
have been
of brine with
placement in
s
5
o
,
d
h
d
d
d
5
s
s
y
o
e
e
.
g
A
r
e
a
e
y
r
n
n
Fig. 2 Relasalinities [16]
different sal
endpoint sa
interpolation
4. Results
4.1 Injection
To study t
recovery, eig
injection of b
set a base ca
of brines wi
Table 1 Effe
Fig. 3 Field
ative permeab.
inities, the ef
aturations an
n.
and Discus
n of Brine wit
the effect of b
ght different c
brine with 35
ase oil recover
ith 10, 5, 4, 3
ect of Brine sa
Brine salinity
Oil recover
oil efficiency (
A Sen
bility profile f
ffect of slug s
nd the relati
ssions
th Different S
brine salinity
cases were ex
kg/m3 TDS w
ry. Subsequen
3, 2, 1, and 0
linity on oil re
(Kg/m3)
ry (%)
(FOE) with bri
nsitivity Study
for high and
size, the effec
ive permeab
Salinities
on improving
xamined. Init
was carried ou
ntly, the injec
kg/m3 TDS w
covery.
0
59
ine salinities of
y on Low Sal
low
ct of
bility
g oil
ially,
ut to
ction
were
und
Fig
oil
TD
star
reco
mai
In o
wet
satu
resu
wat
cut
4.2
D
the
LoS
proh
pro
slug
dem
1
56
f 35, 10, 5, 4, 3
inity Waterflo
dertaken. The
. 3. As expect
recovery for
S. This is bec
rt at salinities
overy is expe
inly due to the
other words, l
ttability shif
uration (Sor)
ult in a m
ter-flooding,
is observed.
Effect of Slug
During the Lo
amount of w
Sal water fo
hibitive and
fits. In this s
g sizes on o
monstrates the
2
51.7 4
, 2, 1, and 0 kg
ooding
e results are d
ted, there was
the injection
cause the low
less than 5 k
erienced, whe
e reduction in
low salinity b
ft that mini
and water r
more efficien
hence, slow
g Size
oSal process,
water injected
or the entire
has the pot
ensitivity stu
oil recovery
e results of di
3 4
47 42
g/m3.
displayed in
s no observed
n of brines ab
salinity effec
kg/m3 TDS. A
en LoSal wat
n water produ
rine injection
imizes the
relative perm
nt oil displ
er developm
it is importan
into a reserv
e production
ential to affe
udy, the effec
was conduc
ifferent scena
5 1
37 3
233
Table 1 and
d incremental
bove 5 kg/m3
cts were set to
An increase in
ter is injected
uction (Fig. 4)
n creates a net
residual oil
meability that
lacement by
ment of water
nt to consider
voir. Injecting
life is cost
fect company
ct of different
cted. Fig. 5
arios of
10 35
37 37
3
d
l 3
o
n
d
).
t
l
t
y
r
r
g
t
y
t
5
234
Fig. 4 Field
injecting low
11, 12, 13 an
by injecting
results demo
oil recovery
indication on
and the amo
better to illu
Table 2.
When the
37613 Rm3,
approximate
Fig. 5 Oil re
water cut (FW
w salinity brin
nd 15 time st
brine with a
onstrate a stro
y on slug size
n the relation
unt of fluids b
ustrate it by vo
e injected brin
the increme
e value of
ecovery for diff
A Sen
WCT) with diff
ne with 0 kg/m
eps of 30 day
salinity of 35
ong dependen
es. However,
nship between
being injecte
olume calcula
ne volume ro
ental oil recov
8.8%. Whe
fferent slug size
nsitivity Study
ferent brine sal
m3 TDS for 6
ys each, follo
5 kg/m3 TDS.
nce of increme
there is no c
n the oil recov
d. Therefore,
ation as show
se from 1747
very recorded
ereas, when
es during low s
y on Low Sal
linities injectio
, 10,
owed
The
ental
clear
very
, it is
wn in
71 to
d an
the
inje
Rm
4.3
Per
T
con
high
rela
inje
add
mad
salinity injectio
inity Waterflo
on.
ected brine vo
m3, the increm
Effect of
rmeability Int
Table of low
ncentration (L
h salinity an
ative permeab
ected brine s
dition to of the
de, as shown
on with brine s
ooding
olume increa
mental oil reco
Endpoint Sa
terpolation
w-salt weigh
SALTFNC) i
nd low salinit
bility that hav
salinities. In
e base case, tw
in Table 3. C
salinity of 0 kg
ased from 376
overy was on
aturations a
hting factors
indicates the a
ty saturation
ve been used
this sensitiv
wo other LSA
ase one was c
g/m3 TDS.
613 to 39580
nly 1.2%.
and Relative
versus salt
amount of the
profiles and
for different
ity study, in
LTFNC were
conducted
0
e
t
e
d
t
n
e
such that wh
data from th
high salinity
kg/m3. In ca
is used when
to the base c
Table 2 Oil
Total P
Injection t
(time step
6
10
11
12
13
15
Table 3 Diff
Salt conce(kg/m
0
1
4
5
35
45
Fig. 6 Illustr
hen a salinity
he low salinity
y profiles wh
ase two, less d
n injected dif
case.
recovery and
V 1
time T
ps) (
ferent tables o
Base case
entration m3)
5
5
rates the oil re
A Sen
y below 5 kg
y profiles wer
hen salinity o
data from low
fferent brine
pore volume (P
12942
Time T
(day)
30
30
30
30
30
30
f low-salt weig
F1 F2
1 1
0.8 1
0.2 1
0 0
0 0
0 0
ecovery for diff
nsitivity Study
g/m3 occurs,
re used, yet u
of brine abov
w salinity pro
salinity com
PV) injected fo
(Rm3)
Total time
(day)
180
300
330
360
390
450
ghting factors v
Salt conce(kg/m
0
1
4
5
35
45
ferent low-salt
y on Low Sal
only
using
ve 5
files
mpare
A
reco
Thi
wat
pro
pro
to th
or different slu
Rate
(Rm3/day)
100
100
100
100
100
100
versus salt con
Case I
entration m3)
5
5
t weighting fac
inity Waterflo
As shown in
overy compar
is can be pr
ter-flooding p
file is used. A
files the oil re
he same degr
ug sizes with in
Inject
(Rm
174
291
320
349
376
395
ncentration for
F1 F2
1 1
1 1
1 1
0 0
0 0
0 0
tors versus.
ooding
Fig. 6, case
red to both th
redicted as
performance i
A reduction in
ecovery was
ree as in case
njection brine s
t vol. Injec
m3)
71 0.
17 0.
29 0.
40 0.
13 0.
80 0.
the synthetic m
Salt conce(kg/m
0
1
4
5
35
45
one gave th
he base case a
the effect o
is high when
n the amount
found to decr
one.
salinity of 0 kg
ct PV Tot
15
26
28
31
33
35
model.
Case II
ntration m3)
5
5
235
he highest oil
and case two.
of the LoSal
the optimum
of the LoSal
rease, but not
g/m3 TDS.
tal recovery
(%)
46.2
52.5
53.5
53.7
55
56.2
F1 F2
1 1
0.6 1
0.4 1
0 0
0 0
0 0
5
l
.
l
m
l
t
A Sensitivity Study on Low Salinity Waterflooding
236
5. Conclusions
Sensitivity studies of LoSal water-flooding on a
synthetic model were carried out using ECLIPSE 100.
The obtained results are based on the properties used in
the simulation model, clearly showed a significant
salinity dependence. An increase in oil recovery can be
observed in conjunction with a reduction in the salinity
of injected brine, where only in the threshold range
between 0 kg/m3 (0.0 ppm) to 5 kg/m3 (5000 ppm).
Furthermore, continuous LoSal injection gives higher
oil recovery. However, when economic aspects were
considered, slug injection can reduce the requirement
for LS water and approximately recovers, the same
percentage of oil. Moreover, the simulation results,
also, indicate that the potential recovery in low salinity
waterflooding was very sensitive to endpoint saturation.
Therefore, it is important to be aware of such input data
in order to obtain accurate simulation results.
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