S li ity iimpact
Salinity
p t on solids
lid p
precipitatio
ipit tion during
d i g CO2 injection
i j ti to
t saline
li aquifers
q if
i Jiangha
in
Ji ghan Basin,
Basin
B i China
Chi
Yibing
ibi Ke,Yilian
Ke Yilian
ili Li,
Lii Telesphore
l h
Kabera
b a,
a Weii Zhang,
Zhang
h
Peng Cheng
Cheng,
h
Qii Fang,
Fang Sanxii Peng
S h l off E
School
Environmental
i
l Studies,
SStudies
di , China
Chi Uni
U iversity
i
i y off G
Geosciences
Geosciences,
i
,W
Wuhan
h 430074
430074,, P
P. R
R. Chi
China
I t d ti
Introduction
M d li g Setup
Modeling
S t p
Jianghan
g
Basin is one of the target
g CO2 storage
g sites.
sites However the
salinity
li i off the
h formation
f
i water in
i Jianghan
Ji h Basin
B i is
i higher
hi h compared
d to
other p
places This p
places.
paper
p uses numerical simulation to highlight
g g the
salinity
li i impact
i
affecting
ff i the
h dry
d out and
dry-out
d precipitation
i i i while
hil injecting
i j i
dryy supercritical
p
CO2 into Jianghan
g
basin ((China).
(China)) The aim of the
present study
d is
i on the
h quantitative
i i aspects off salt
l precipitation
i i i in
i the
h
vicinity
y of a CO2 injection
j
well, as induced byy formation dry-out
well,
dryy out from
water dissolution
di l i
i
into
the
h flowing
fl i
CO2 stream.
stream The
Th Jianghan
Ji h Basin
B i
formations p
properties
p
were used.
used In order to assess the effects a 1D
model
d l was developed
d l d which
hi h was considered
id d to be
b a homogenous
h
sandstone of about 100m thickness.
thickness Then a number of sensitivityy
simulations
i l i
were performed
f
d to analyze
l
the
h impact.
i
impact
Th 2
The
2-D
D model
d l
results showed that the effects of g
gravity
y override on g
gas saturation
di ib i
distributions
were strong and
d also
l reflect
fl
the
h effect.
effect
ff
M
More
d il and
details
d
mechanisms
h i
are needed
d d to
t be
b explored
l d in
i future
f t ’s research
future’s
h.
Our initial numerical simulations were done with ECO2N module
f
from
the
h TOUGH2 simulator.
simulator
i l
ECO2N designed
d i d for
f applications
li i
to
geologic
g
g sequestration
q
of CO2 in saline aquifers.
aquifers
q
It includes a
comprehensive
h i
d
description
i i
off the
h
thermodynamics
h
d
i
and
d
thermophysical
p y
properties
p
p
of H2O-NaCl-CO
O NaCl CO2 mixtures ((Pruess et al.,
al ,
2005))
2005).
The aquifer
q
is assumed as a homogeneous,
homogeneous
g
, isotropic,
isotropic
p , infinite-acting
infinite acting
g
one The
one.
h injection
i j i rate is
i constant at 50kg/s
k / for
f a time
i
period
i d off 1000
days
days.
y Parameters and schematic map
p are shown below.
below
Table 1.
1 Hydrogeological parameters used in the simulations
S dy A
Study
Area
Th Jianghan
The
Ji h Basin
B i lies
li in
i the
th south
south-central
th central
t l partt off the
th Hubei
H b i Province,
P i
the Jianghan Plain between Yangtzi River and Hanshui River,
River west to
Yi h
Yichang
city,
it eastt to
t Yingcheng
Yi h
city,
it south
th to
t Huhong
H h
city,
it and
d north
th to
t
the north of Jingzhou city (Fig.
(Fig 1).
1) It is a salt-lake rift basin developed
on the
th Zhongyangzi
Zh
i paraplatform
l tf
d i the
during
th Cretaceous
C t
and
d Tertiary
T ti
covering an area of 36350 km2.
Figure
g
2.
2 Schematic of 1-D
1 D radial
injection
j
pproblem
Results off Base Case
C
Fig 1 Location map of the Jianghan Basin (From Li Guoyu et al.,
Fig.1.
al 2002)
Th Jianghan
The
Ji h
B i contains
Basin
t i
L t Cretaceous
Late
C t
t Quaternary
to
Q t
sedimentaryy deposits
p
upp to 10km thick.
thick There are two p
prominent
sedimentary
di
t
cycles
l
i l di
including
th Haiyang
the
H i
F
Formation
ti
off upper
Cretaceous, the Shashi Formation of Paleocene,
Cretaceous,
Paleocene, the Xingouzui
g
F
Formation
Formation,
ti
th Jingsha
the
Ji h Formation
F
ti
and
d the
th Qianjiang
Qi ji
F
Formation
ti
off
Eocene, the Jinghezhen
Eocene,
g
Formation of Oligocene,
Oligocene
g
, the Guanghuasi
g
F
Formation
ti off Miocene
Mi
t Pliocene
to
Pli
as well
ll as the
th Pingyuan
Pi
F
Formation
ti off
Pleistocene to recent.
recent
Th reservoir
The
i rocks
k in
i the
th Jianghan
Ji h Basin
B i include
i l d sandstone,
sandstone
dt
globulitic
l b liti
marl, fractured mudstone and basalt,
marl,
basalt, sandstone reservoir as the major.
major
j
Xi
Xingouzui
i Formation
F
ti
and
d Qianjiang
Qi ji
F
Formation
ti
i the
is
th predominant
d i t
ppetroliferous and saliniferous sandstone reservoir as shown in Fig.
Figg 1.
1
Th sediment
The
di
t supply
l is
i unidirectional
idi ti l and
d adequate,
adequate
d
t mainly
i l from
f
th
the
Jingmen
Jingmen,
g
, Hanshui and Dangyang
gy g ppalaeodrainage
g p
pattern in the north of
th basin
the
b i during
d i the
th Qianjiang
Qi ji
and
d Xingouzui
Xi
i Formation
F
ti deposits.
d
deposits
it
The target
g storage
g formation would be Xingouzui
g
Formation It
Formation.
di t ib t three
distributes
th
d lt sandd bodies
delta
b di in
i the
th Mashan,
M h
Mashan
H
Hougang
and
d
Hanchuan area from west to east in the north of the basin and they
y
connectt together
t th into
i t a reservoir
i development
d l
t zone in
i horizon
h i
and
d gett
thin to the south.
south The sand bodyy is widelyy distributed with the area of
11000 km
k 2, and
d the
th thickness
thi k
off the
th sandstone
dt
i generally
is
ll 20 to
t 140
meters in range,
range
g , with the maximum thickness upp to 237 meters.
meters
Silt t
Siltstone
i the
is
th main
i rock
k type,
t
type
with
ith the
th average porosity
it off 17% and
d
the average
g p
permeability
y of 98×10-33µ
µm2.
Th formation
The
f
ti
water
t in
i Xingouzui
Xi
i Formation
F
ti
i mainly
is
i l calcium
l i
chloride and sodium sulfate type.
type
yp As the burial depth
p deeper
p than
1000 the
1000m
1000m,
th water
t salinity
li it appears little
littl differences
diff
with
ith the
th increasing
i
i
depth
depth,
p , mainly
y between 100000 mg/L
g to 260000 mg/L.
mg/L
g
We use the average
g value of salinityy 0.2
0 2 in the base case modeling.
modeling
g
The gas saturation,
saturation solid saturation as function of the similarity variable
aaree sshown
how be
b low from
below
f o Figure
Figu e 3 aand
d Figure
Figu e 4.
4.
Pruess and Spycher (2007),
(2007) have shown that the numerical results for
the reference
tthe
efe e ce case follow
follow a ssimilarity
i ila itty so
solution,
luttio , w
where
he e tthe
the so
solution
luttio
remains
i invariant
i
i when
h plotted
l
d versus the
h similarity
i il i variable
i bl R2/t,
/ where
/t
h
R is
is a se
selected
lected
t d radial
ad
dial d
dista
distance
t ce w
while
hile t is
is ttime.
ti e. In
I tthis
this pape
paper,, we aalso
lso use
it to plot the results to check the accuracy of the numerical simulations.
simulations
The e aaree two
There
t
ssharp
ha p moving
ovi g fronts
f o tts sshown
how from
f o Figure
Figu e 3,
3 tthat
thatt is,
is, tthe
the
gas saturation front at ξf = R2/t ≈6.6×10
≈6 6×10-33m2/s and the dry-out front at
ξd =R
R2/t
/t≈6
/t≈6.9×10
6.9
9×10
10-66m2/s.
/ According
A
di
t the
to
th two
t
moving
i
f t the
fronts,
th
displacement process could be divided into three regions.
regions In the region
ξξ<ξξd, tthe
the gas satu
saturation
t attio ca
can reach
each to
t 0.9
0 9469
0.9469
69 w
while
hile aall
ll tthe
the liquid
liquid
dp
phase
hase
has been removed.
removed The rest saturation is occupied by the precipitated
salt.
sa
ltt. The
The two
t
phase
p
hase region
egio locates
locates
t att ξd<ξ<ξ
ξ ξf, as a intermediate
i te
t
ed
diate
t region.
egio .
The supercritical carbon dioxide and the saline water coexist there.
there
Whe ξξ>ξξf, in
When
W
i tthis
this region,
egio , CO2 haven’t
have ’tt yett reached.
eached.
d
The solid saturation should be constant throughout.
throughout This remarkable
featu
feature
t e ca
can be
b p
proved
oved
d d
di ecttly from
directly
f o tthe
the ssimilarity
i ila itty p
property
ope tty ((Pruess,
(P uess,
2009) The simulation results show variable solid salt saturation in the
2009).
dry-out
d
y outt zone,
o e, w
which
hich cou
could
ldd be
b tthe
the result
esultt o
off numerical
u e ical instability
i stab
t bilitty
problems (Zeidouni et al.,
al 2009).
2009) From Figure 4,
4 we can got the value of
solid
so
lid
dp
precipitation
ecipittattio 0.053
0 05312.
0.05312.
I p t off Salinity
Impact
S li ity on
S lid P
Solid
Precipitation
ipit ti
Salinity
y varies ggreatlyy in Jianghan
g
Basin Three sensitivityy tests were
Basin.
conducted
d
d by
b changing
h i the
h salinity
li i from
f
the
h base
b
base-case
case off 20wt.%
20 % to
20wt
10wt % , 15 wt.%
10wt.%
wt % and 25 wt.%.
wt % These salinities were selected byy taking
g
account off the
h variable
i bl range between
b
the
h lowest
l
range off salinity
li i and
d
the highest
g
concentration of salinity.
salinityy The effect of changes
g in salinity
y on
solid
lid precipitation
i i i versus the
h similarity
i il i variable
i bl would
ld be
b discussed
di
d
hereunder
hereunder.
Fi
Figure
5 clearly
l l delineates
d li
that
h as the
h salinity
li i increases,
i
increases
the
h solid
lid
pprecipitation
p
increases The increasing
increases.
g multiple
p of solid pprecipitation
p
is
slightly
li h l bigger
bi
than
h those
h
off salinity.
salinity
li i It
I ’s also
It’s
l revealed
l d that
h reducing
d i
salinityy by
y a factor 2 reduces solid saturation overproportionately
p p
y by
ya
f
factor
off 2.23
2 23 by
b Pruess
P
(2009) It
(2009).
I can be
b concluded
l d d that
h solid
lid
pprecipitation
p
depends
p
strongly
g y on aqueous
q
pphase salinity.
salinityy With the
i
increase
off salinity,
salinity
li i the
h brine
b i viscosity
i
i increases.
i
increases
Th increase
The
i
i brine
in
bi
viscosityy means the decreasing
g mobility
y of the brine in the zone of twotwo
phase
h
fl
flow
reduces
d
the
h displaced
di l d brine
b i by
b CO2 gas,
gas and
d increases
i
the
h
evaporated
p
brine Thus for higher-salinity
brine.
higher
g
salinityy brine,
brine, the solid saturation of
the
h porous medium
di
i the
in
h completed
l d dry
d out zone has
dry-out
h a higher
hi h ratio
i
than that for the lower-salinity
lower salinityy brine.
brine However,
However, we should note that the
i
increasing
i
salinity
li i reduces
d
the
h brine
bi
vapor pressure (i.e.
(i e the
h water
dissolution in ggas pphase),
phase)), which is not favorable to the increase in brine
salinity
li i during
d i the
h displacement
di l
process
process.
For the several cases compared
p
to base-case,
base case, the dry-out
dryy out areas in all
f
four
cases occur at similar
i il areas on the
h xx-axis
axis
i (ξ
(ξ=R
R2/t)
/ ) with
i h occurring
i in
i
an almost similar ppattern as base-case.
base case Solid saturation is the volume
f
fraction
i off precipitated
i i d salt
l in
i the
h original
i i l pore space (Garcia,
(G i 2003;
(Garcia
2003
Pruess, 2005).
Pruess,
2005)) The fraction of the original
g
ppore pporosityy that remains
after
f salt
l precipitation
i i i is
i what
h is
i available
il bl for
f fluid
fl id flow
fl
( f
(referred
d to as
active flow pporosityy ((Garcia,
(Garcia, 2003).
2003)) Hence ggreater salinity
y means lesser
active
i flow
fl
porosity
i which
hi h in
i turn reduces
d
the
h permeability
bili off the
h
medium as discussed byy Verma and Pruess ((1988).
(1988)) Greater salt
precipitation
i i i may also
l reduce
d
porosity
i and
d impair
i
i permeability
bili off the
h
reservoir in the vicinity
y of the wellbore which could lead to reduction in
i j i i which
injectivity
hi h may affect
ff
storage operations
i
if it
i injection
i j i
times
i
pperpetuate
p
((Zeidouni et al.,
al , 2009).
2009)) In addition,
addition, pporosity
y reduction of the
reservoir
i may affect
ff
the
h overall
ll storage potential
i l since
i
i affects
it
ff
CO2
migration
g
distance within the reservoir ((Han and McPherson et al.,
al ,
2008) Increase
2008).
I
i brine
in
b i salinity
li i leads
l d to a decrease
d
i CO2 solubility
in
l bili
and higher
g
ppressures around the injection
j
well(Figure
( g
6)) may
6).
y induce
movement effects
ff
within
i hi the
h formation
f
i
l di
leading
to increased
i
d risk
i k off
opening
p
g upp of ppre-existing
pre existing
g fractures and faults causing
g ppossible CO2
l k
leakage
leakage.
H
Hence
i should
it
h ld be
b considered
id d for
f future
f
CO2 sequestration
i
pprojects
j
in Jianghan
g
Basin
Basin.
Fi
Figure
5.
5 Solid
S lid saturation
t ti att different
diff
t
salinities
li i i as function
i of the
h similarity
i il i
variable
Figure
Fig
g re 3.
3 Simulated
Sim lated ggas saturation
sat ration as a
f ti
function
off the
th similarity
i il it variable.
i bl The
Th
thick
hi k solid
lid line
li represents a spatial
i l profile
fil
at a simulation time of 8.64x10
8 64x107s,
s while
the thick dashed and dashdot lines
represent
p
a time series of data for ggrid
bl k att a radial
blocks
di l distance
di t
off R = 0.99
0 99 m
and
d 5.99m
5 99
Figure
g
4 Solid saturation ((fraction of
4.
ppore volume containing
g solid
pprecipitate)
ecipittate)
t ) as function
fu cttio
ooff tthe
the
similarity
i il i variable
i bl
Fi
Figure
6 Fluid
6.
Fl id pressure at different
diff
salinities as function of the similarity
variable
W have
We
h
got the
h values
l
off solid
lid saturation
i from
f
the
h modeling
d li results
l
shown in figures.
figures
g
In addition,
addition, the theoretical pprecipitation
p
of all the
di l d salt
dissolved
l could
ld be
b calculated
l l d (Pruess,
(P
(Pruess
2009)
2009):
Ss,a
ρaq*Xs/ρρs
s a=ρ
Sh
Shown
f
from
T bl 2,
Table
2 though
h
h solid
lid saturation
i
and
d the
h theoretical
h
i l
pprecipitation
p
of all the dissolved salt increases overproportionately
p p
y to
the
h increase
i
off salinity,
salinity
li i the
h precipitation
i i i percent does
d
not change
h
as the
h
salinity
y increases and varyy in a small range.
range
g
T bl 2.
Table
2 Theoretical
Th
ti l precipitation
i it ti off all
ll the
th dissolved
di l d salt
lt andd precipitation
i it ti percentt
I order
In
d to
t explore
l
salinity
li it impact
i
t on solid
lid precipitation
i it ti within
ithi gravity
it
effects, we carried on several simulation modeling
effects,
g into a 2D R-Z
R Z system
y
with
i h different
diff
i i i l salinities,
initial
salinities
li i i 20wt.%,
20 % 10wt.%
20wt
10 % , 15 wt.%
10wt
wt % and
d 25 wt.%.
wt %
The thick of the aquifer
q
is assumed as 10 meters.
meters Parameters setting
g are
similar
i il with
i h those
h
i 11-D
in
D case.
case The
Th gas saturation
i distribution
di ib i with
ih
initial salinity
y 0.2
0 2 is shown in Figure
g
7 Effects of ggravity
7.
y override on
gas saturation
i distribution
di ib i are strong (Pruess,
(P
(Pruess
2009) Figure
2009).
Fi
8 and
d 9 are
solid pprecipitation
p
distributions near the well with 20wt.%
20wt % and 25wt.%
25wt %
salinities
salinities.
li i i The
Th distributions
di ib i
are similar.
similar
i il The
Th average solid
lid saturation
i in
i
the dry-out
dryy out regions
g
is 0.0537
0 0537 and 0.0705
0 0705 respectively.
respectively
p
y With higher
g
salinity
salinity,
li i the
h value
l off solid
lid precipitation
i i i can reach
h higher.
hi h
higher
Fi
Figure
7.
7 distribution
di t ib ti off gas saturation
t ti with
ith initial
i iti l salinity
li it 0.2
02
Figure 8.
8 distribution of solid saturation Figure 9.
9 distribution of solid saturation
with initial salinity 00.2
2
with initial salinity 00.25
25
C
Conclusions
l i
F
For
11-D
D radial
di l flow
fl
under
d
th similarity
the
i il it property
t constraints
t i t
mentioned above,
above, the simulations have pprovided the following
g results:
Th
Three
diff
different
t zones: ζd =R
R2/t
/t=66.9×10
6 9×10-66 m2/s
/ a zone where
h
complete
l t
dryy out of aqueous
dry-out
q
pphase has occurred,
occurred, the liquid
q
pphase has been
removed
d by
b dissolution
di l ti into
i t the
th flowing
fl i CO2, the
th gas saturation
t ti in
i this
thi
region
g
is slightly
g y less than 1.
1 The dryy out zone is followed byy an
i t
intermediate
di t zone ζd≤R2/t≤ζf, finally,
fi ll there
th
i an outer
is
t region:
i
ζf
=R2/t>6.6×10
/t>6 6×10-33 m2/s.
/s From the obtained results it was shown that
precipitation
i it ti occurs only
l behind
b hi d a sharp
h
d outt front;
dry-out
dry
f t
The numerical simulation results indicate that solid saturation (fraction
(
off pore space filled
fill d by
b precipitate)
i it t ) in
i the
th dry
d outt region
dry-out
i is
i constant;
t t
As the salinityy increases,
increases, the solid pprecipitation
p
increases The
increases.
i
increasing
i multiple
lti l off solid
lid precipitation
i it ti is
i slightly
li htl bigger
bi
th those
than
th
off
salinity
salinity.
y
T dimensional
Two-dimensional
Two
di
i l simulations
i l ti
off CO2 injection
i j ti
results
lt showed
h
d the
th
following
g results: Effects of ggravity
y override on ggas saturation
di t ib ti
distributions
are strong
t
and
d solid
lid precipitation
i it ti distributions
di t ib ti
are similar.
similar
i il
With higher
g
salinity
salinity,
y, the value of solid pprecipitation
p
can reach higher.
higher
g
A k
Acknowledges
l dg
This pproject
j is funded through
g the Stanford Global Climate and Energy
gy
P j t (GCEP).
Project
(GCEP) We
W would
ld also
l like
lik to
t acknowledge
k
l d
supportt and
d
encouragement
g
from the pproject
j
ggroup
p in School of Environmental
St di China
Studies,
Chi University
U i
it off Geosciences.
G
i