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Transcript of Chemistry Lab Report
PET-570 Reservoir Chemistry Project
Student name: Chunlei zhang
Student number: 230286
Date:04/17/2015
Project1 EFFECT OF CARBONATE ON WATER CHEMISTRY
OBJECTIVE 1. To study the change in pH over a range of temperature for different water systems in presence
of CO2 gas phase and Calcite equilibrium phase.
2. To study the dissolution of calcite with temperature in different water systems.
GIVEN DATA
The ion composition of the individual Water/brines that we will use are given in Table 0:
Table 0
Ions DI Water Nacl Nacl+Ca SW
mmol/l mmol/l mmol/l mmol/l
Na+ 0.0 657.4 617.7 450.1
K+ 0.0 0.0 0.0 10,1
Ca+ 0.0 0.0 13.0 13.0
Mg2+ 0.0 0.0 0.0 44,5
Cl- 0.0 657.4 643.7 525,1
SO42- 0.0 0.0 0.0 24,0
HCO3- 0.0 0.0 0.0 2,0
CO32- 0.0 * * *
TDS,g/l 0.0 38.42 37.54 33,4
IS 0.0 0.657 0.657 0.657
DI water o Simulation result data for the DI water.
Table 1 simulation data for the DI water
Temp(℃) PH Conc. Of
Ca(mmol/kg) DI DI+CO2 DI+CAL
25 7 3.809 9.907 0.1241
50 6.632 3.894 9.336 0.1486
75 6.344 3.991 8.864 0.1726
100 6.12 4.094 8.47 0.1874
125 5.945 4.201 8.142 0.1879
150 5.813 4.311 7.876 0.1755
o Diagram of PH vs Temperature for DI Water Solution
Fig 1 PH vs Temperature for DI water solution
o Comments on the pH effects of CO2 and Calcite 1. The effect of CO2 to the water is donating the H+ by acting as acid to the
water base. With the following reactions. The concentration of H+ is
increasing at the same temperature compared pure water without CO2
which results in the reduction of PH number. While the solubility of CO2 Is
decreased with temperature rise, the concentration of CO2 is reducing and
the PH number is increasing even higher temperature can increasing the
concentration of𝐻+ .
𝐶𝑂2 + 𝐻2𝑂 ⇌ 𝐻2𝐶𝑂3 (1)
𝐻2𝐶𝑂3 + 𝐻2𝑂 ⇌ 𝐻𝐶𝑂3−1 + 𝐻3𝑂+ (2)
2. The effect of Calcite to the water is absorbing the H+ by acting as base to the
water. With the following reactions. The concentration of 𝑂𝐻− is increasing at
the same temperature compared pure water without Calcite which results in the
rise of PH number. While the solubility of Calcite Is decreased with temperature
rise, the concentration of 𝑂𝐻− is reducing and the PH number and concentration
of H+ is increasing.
𝐶𝑎𝐶𝑂3(𝑎𝑞) ⇌ 𝐶𝑂3−2 + 𝐶𝑎+2 (3)
𝐶𝑂3−2 + 𝐻2𝑂 ⇌ 𝐻𝐶𝑂3
−1 + 𝑂𝐻− (4)
3. As for the pure water, the reaction would move to right as the temperature
increasing. The concentration of 𝐻+ is increasing and the PH number becomes
smaller than lower temperature.
76.632 6.344 6.12 5.945 5.813
3.809 3.894 3.991 4.094 4.201 4.311
9.9079.336
8.8648.47 8.142 7.876
0
2
4
6
8
10
12
0 25 50 75 100 125 150 175
PH
Temperature(℃)
PH vs Temperature For DI Water Solution
DI DI with CO2 DI with Calcite
o The dissolution of Calcite (CaCO3) vs Temperature.
Fig 2. Concentration of Ca vs Temperature for DI water solution
As seeing from the diagram of conc. Of Ca, it would initially increase with the increasing
temperature. The solubility of calcite would decrease with temperature, however, the increasing
concentration of [H] would consume the 𝐶𝑂3−2(reaction 7). Under that conition the solubility of
calcite would increase which leave high [OH-] and lower [H]. At temperatue around 120, it reach the
peak. Then precipitation of Calcite (reaction 5) arising due to the temperature’s effect on the
solubility override the increasing solubility caused by the increasing concentration of [H+].
𝐶𝑎𝐶𝑂3(𝑠) ↔ 𝐶𝑎𝐶𝑂3(𝑎𝑞) (5)
𝐶𝑎𝐶𝑂3(𝑎𝑞) ↔ 𝐶𝑎+2 + 𝐶𝑂3−2 (6)
𝐶𝑂32− + 𝐻2𝑂 ↔ 𝐻𝐶𝑂3
− + 𝑂𝐻− (7)
NaCl – brine
o Simulation result data for the NaCl – brine
Table 2 simulation data for the DI water
TEMP(℃) PH Conc. Of Calcite
(mmol/KG) NACL NACL+CO2 NA+CAL
25 7 3.858 9.873 0.537
50 6.606 3.946 9.282 0.726
75 6.307 4.046 8.808 0.890
100 6.076 4.151 8.427 0.970
125 5.896 4.259 8.122 0.950
150 5.759 4.368 7.88 0.850
0.1241
0.1486
0.17260.1874 0.1879
0.1755
0
0.05
0.1
0.15
0.2
0.25
0 25 50 75 100 125 150 175
Co
n. o
f C
a(m
mo
l/kg
)
Temperature(℃)
Con. of Ca vs Temperature of DI Water
o Diagram of PH vs Temperature for NaCl brine Solution
Fig 3 PH vs Temperature for NaCl brine
For different of NaCl brine, the temperature has various effect. As for the NaCl brine, the PH
number is decreasing with the increased temperature since more H+ has been donated by
water with higher temperature. While for the NaCl brine with CO2, the PH number is
increasing since the solubility of CO2 is reducing as higher temperature. For the NaCl brine
with Calcite, the concentration of [H+] is increasing with the temperature due to the
reducing solubility of Calcite which can consume proton(reaction 5,6,7).
o The dissolution of Calcite (CaCO3) vs Temperature.
Fig 4. Concentration of Ca vs Temperature for DI NaCl Brine
As we can see from the above diagram (Fig 4), the dissolution of calcite in NaCl-Brine is bigger than
DI water at same temperature .Although, the solubility variation trend is similar to each other,
increasing with temperature initially.
76.606 6.307 6.076 5.896 5.759
3.858 3.946 4.046 4.151 4.259 4.368
9.8739.282
8.808 8.427 8.122 7.88
0
2
4
6
8
10
12
0 25 50 75 100 125 150 175
PH
Temperature(℃)
PH vs Temperature of Nacl BrineNaCl Brine NaCl with CO2 NaCl with Calcite
0.537
0.726
0.8900.970 0.950
0.850
0.1241 0.1486 0.1726 0.1874 0.1879 0.1755
0.000
0.200
0.400
0.600
0.800
1.000
1.200
0 25 50 75 100 125 150 175
Co
n. o
f C
a(m
mo
l/kg
)
Temperature(℃)
Con. of Ca vs Temperature of Nacl Brine
The reason of NaCl Brine is more soluble is because the adding ion Na+. It can form the complex -
[NaCO3-] (Molarity 2.96e10-4 @25℃) with 𝐶𝑂3−2 which results in move the ‘reaction 6’ to the right
side. Then more Calcite would dissolve into the NaCl brine.
NaCl+Ca2+ - brine o Simulation result data for the NaCl – brine
Table 3 simulation data for the NaCl+Ca2+ - brine
Temp(℃) PH Ca(aq)(mmol/kg) Ca(aq) fromCalcite
25 9.176 1.305E-02 5.00E-02
50 8.659 1.308E-02 8.00E-02
75 8.231 1.311E-02 1.10E-01
100 7.874 1.313E-02 1.30E-01
125 7.577 1.313E-02 1.30E-01
150 7.339 1.312E-02 1.20E-01
o Diagram of PH vs Temperature for NaCl+Ca2+ brine Solution
Fig 5 PH vs Temperature for NaCl+ Ca2+ and Nacl brine in equilibrium with Calcite
The diagram illustrate the PH number of calcite in equilibrium NaCl is bigger than that in NaCl+Ca.
The reason is due to the previous adding Ca2+ .It can reduce the solubility of Calcite as well as
decrease the concentration of 𝐶𝑂3−2. Under this circumstance the concentration of [OH-] in NaCl+Ca
is lower than solution without Ca2+. Thus, the latter solution has smaller PH number.
o The dissolution of Calcite (CaCO3) vs Temperature.
9.1768.659
8.231 7.874 7.577 7.339
9.8739.282
8.808 8.427 8.122 7.88
0
2
4
6
8
10
12
14
0 25 50 75 100 125 150 175
PH
Temperature(℃)
PH for NaCl+Ca
PH for NaCl
Fig 6. Concentration of Ca vs Temperature for NaCl+Ca2+ Brine and NaCl
The lowest solubility for the NaCl+Ca2+ - brine system of Calcite is due to the adding Ca2+. It highly
reduce the solubility of Calcite compare to the other two solution system.
SW – brine
o The mineral precipitations for SW and SW+Calcite
Table 4 SI of mineral for SW and SW+Calcite
℃) SI of ion for SW
SI of ion for SW+Calcite
Calcite Dolomite Anhydrite Aragonite Dolomite
25 -0.35 0 -0.89 -0.5 0.7 50 -0.17 0.52 -0.7 -0.29 0.85 75 0.03 0.82 -0.48 -0.08 0.76
100 0.21 0.88 -0.24 0.11 0.47 125 0.35 0.68 0.01 0.26 -0.02 150 0.43 0.18 0.27 0.35 <0
0.050 0.080 0.110 0.130 0.130 0.120
0.537
0.726
0.890
0.970 0.950
0.850
0.1241 0.1486 0.1726 0.1874 0.1879 0.1755
0.00
0.20
0.40
0.60
0.80
1.00
0 25 50 75 100 125 150 175
Co
n. o
f C
a(m
mo
l/kg
)
Temperature(℃)
Conc. Of Ca for NaCl+Ca
Conc. Of Ca for NaCl
Conc. Of Ca for DI Water
o The PH number for SW and SW+Calcite
Fig 7. pH vs temperature for the SW - brine and SW - brine in equilibrium with Calcite.
When seawater is in equilibrium with calcite, the existing HCO3- in seawater play a role to buffer the
reaction 7 moving to right side. Then concentration of OH- is much smaller than without adding
HCO3- in seawater. Then the concentration of H+ is increasing. The PH number turns out not much
higher than seawater without calcite. Around 75℃ , actually the reaction 5 actually totally move to
left hand. There is no soluble Calcite. During this process, it consume the OH- with reaction 7, which
results in concentration rising of H+ compare with latter. The PH number is smaller than the
seawater after that temperature.
o dissolution of Calcite (CaCO3) vs Temperature
Fig 8. the dissolution of Calcite (CaCO3) vs Temperature
7 6.888 6.829 6.781 6.721 6.629
7.3097.029 6.805 6.627 6.488 6.377
0
1
2
3
4
5
6
7
8
0 25 50 75 100 125 150 175
PH
Temperature(℃)
PH for SW
PH for equlibrium of SW with Calcite
0.11
0.07
0.00 0.00 0.00 0.00
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0 25 50 75 100 125 150 175
Co
n. o
f C
a
Temperature(℃)
Around 75℃ , solubility of Calcite is reduced to Zero. The reason of this phenomenon is due to the
existing HCO3-. With temperature increasing, it acts as an acid buffer to maintain the PH varying in
small range. But the solubility of Calcite is continuously decreasing (reaction 5 moving to left hand).
Approximate 75℃ , it is become zero.
Project 2 Compatibility between FW and Injection brine (SW) - Scale
formation
Given Data
The ion composition of the SW and FW are given in Table 2.1:
Table 2.1
Ions SeaWater SW Formation Brine FW
mg/l mmole/l mg/l mmole/l
Na+ 10347.4 450.1 26574.4 1156.0
K+ 393.3 10,10 272.7 7.0
Ca+ 520.0 13.0 4008.5 100.0
Mg2+ 1082.4 44.5 533.5 22.0
Ba2+ 0.0 0.0 540.8 03.sep
Sr2+ 0.0 0.0 1580.8 18.0
Cl- 18617.4 525.1 51292.4 1446.8
SO42- 2306.0 24.0 0.0 0.0
HCO3- 123.5 2.0 7,30 0.1
TDS,g/l 33.39 84.72
IS 0.657 1.591
SW
o The precipitation of mineral.
The precipitation of minerals can be attribute to saturation Index (SI) value. If SI value of less than zero
indicates dissolution and SI>0 indicated precipitation. The following minerals had positive SI value at
higher temperature.
1. Anhydrite
2. Aragonite
3. Calcite
4. Dolomite
o Plot the precipitate in mmol/kg conc. vs. temperature.
1). Anhydrite (CaSO4)
Table 2.2 Simulation Result of Anhydrite(CaSO4)
TEMP(℃) SI** logIAP logK soluble
Conc.Ca2+
(mol/L)
Total Conc.of Ca2+
(mol/kg)
precipation of CaSO4(S)
(mmol/kg)
25 -0.89 -5.16 -4.28 0.00263 0.00263 0.00000 50 -0.7 -5.27 -4.58 0.00232 0.00232 0.00000 75 -0.48 -5.39 -4.91 0.00202 0.00202 0.00000
100 -0.24 -5.5 -5.26 0.00178 0.00178 0.00000 125 0.01 -5.62 -5.63 0.00153 0.00155 0.01773 150 0.27 -5.73 -6 0.00100 0.00136 0.36458
𝐶𝑎𝑆𝑂4 ↔ 𝐶𝑎+2 + 𝑆𝑂42− (8)
According to the reaction of Anhydrite, then the precipitation would be emerge when the SI>0.
The total ion activity product is [𝐶𝑎+2][𝑆𝑂4
2−]
[𝐶𝑎𝑆𝑂4]=IAP. The activity of [𝐶𝑎𝑆𝑂4] is 1. Thus,
Total ion of [𝐶𝑎+2] is equal to (IAP) 0.5 which is equal to the molarity of CaSO4.
While the soluble concentration of CaSO4 can be computed by the equilibrium constant K.
The soluble concentration is K0.5. Then precipitation of CaSO4 is the difference, namely
conc. of precipation = 𝐼𝐴𝑃0.5 − 𝐾0.5
Fig 2.1. Conc. Of Anhydrite precipitation(CaSO4) vs Temperature
2). Aragonite (CaSO4)
1.77E-02
3.65E-01
0.00E+00
1.00E-01
2.00E-01
3.00E-01
4.00E-01
5.00E-01
0 20 40 60 80 100 120 140 160
Co
nc.
of
pre
pic
ipat
ion
(mm
ol/
kg)
Temp(℃)
Table 2.3 Simulation Result of Anhydrite(CaSO4)
TMEP (℃)
SI** logIAP logK soluble Conc.Ca2+
(mol/kg)
Total Conc.of Ca2+
(mol/Kg)
precipation of CaSO4(S)
(mmol/kg)
25 -0.5 -8.83 -8.34 3.84592E-05 3.84592E-05 0.00
50 -0.29 -8.83 -8.54 3.84592E-05 3.84592E-05 0.00
75 -0.08 -8.9 -8.81 3.54813E-05 3.54813E-05 0.00
100 0.11 -9.06 -9.17 2.60016E-05 2.95121E-05 0.00035
125 0.26 -9.32 -9.59 1.60325E-05 2.18776E-05 0.00058
150 0.35 -9.72 -10.07 9.22571E-06 1.38038E-05 0.00046
Fig 2.2 Conc. Of Aragonite precipitation (CaSO4) vs Temperature
3). Calcite (CaCO3)
Table 2.4 Simulation Result of Calcite (CaCO3)
TMEP (℃)
SI** logIAP logK soluble
Conc.Ca2+
(mol/kg)
Total Conc.of Ca2+
(mol/kg)
precipation of CaSO4(S)
(mmol/kg)
25 -0.35 -8.83 -8.48 3.84592E-05 3.84592E-05 0.00000
50 -0.17 -8.83 -8.66 3.84592E-05 3.84592E-05 0.00000
75 0.03 -8.9 -8.93 3.42768E-05 3.54813E-05 0.00120
100 0.21 -9.06 -9.27 2.31739E-05 2.95121E-05 0.00634
125 0.35 -9.32 -9.68 1.44544E-05 2.18776E-05 0.00742
150 0.43 -9.72 -10.15 8.41395E-06 1.38038E-05 0.00539
3.51E-03
5.85E-03
4.58E-03
0.00E+00
2.00E-03
4.00E-03
6.00E-03
8.00E-03
0 20 40 60 80 100 120 140 160
Co
nc.
of
pre
pic
ipat
ion
(mm
ol/
kg)
Temp(℃)
Fig 2.3 Conc. Of Calcite precipitation (CaCO3) vs Temperature
4). Dolomite (CaMg(CO3)2)
conc. of precipation = 𝐼𝐴𝑃0.25 − 𝐾0.35
Table 2.5 Simulation Result of Dolomite (CaMg(CO3)2)
temp SI** logIAP logK soluble Conc.Ca2+
(mol/kg) Total Conc.of Ca2+
(mol/kg)
precipation of CaSO4(S)
(mmol/kg)
25 0 -17.09 -17.09 5.33949E-05 5.33949E-05 0.00E+00 50 0.52 -17.11 -17.63 3.91291E-05 5.27837E-05 1.37E-02 75 0.82 -17.26 -18.08 3.01995E-05 4.84172E-05 1.82E-02
100 0.88 -17.6 -18.48 2.39883E-05 3.98107E-05 1.58E-02 125 0.68 -18.14 -18.82 1.97242E-05 2.91743E-05 9.45E-03 150 0.18 -18.94 -19.13 1.65006E-05 1.84077E-05 1.91E-03
Fig 2.4 Conc. Of Dolomite precipitation(CaMg(CO3)2)vs Temperature
1.20E-03
6.34E-03
7.42E-03
5.39E-03
0.00E+00
2.00E-03
4.00E-03
6.00E-03
8.00E-03
0 20 40 60 80 100 120 140 160
Co
nc.
of
pre
pic
ipat
ion
(mm
ol/
kg)
Temp(℃)
0.00E+00
1.37E-02
1.82E-021.58E-02
9.45E-03
1.91E-03
0.00E+00
6.00E-03
1.20E-02
1.80E-02
2.40E-02
3.00E-02
0 20 40 60 80 100 120 140 160
Co
nc.
of
pre
pic
ipat
ion
(mm
ol/
kg)
Temp(℃)
Formation Water o The precipitation of mineral.
With the temperature increasing, the SI for all the mineral is smaller than zero. Then there is no
precipitation for the formation water with temperature range 25-150℃
Compatibility of brines o Precipitation of Minerals:
The precipitation of minerals can be attribute to saturation Index (SI) value. If SI value of less
than zero indicates dissolution and SI>0 indicated precipitation. The following minerals had
positive SI value at higher temperature.
1. Anhydrite
2. Aragonite
3. Calcite
4. Barite
5. Celestite
6. Dolomite
7. H2O(g)
o Plot the precipitate in mmol/kg conc. vs. temperature.
1). Anhydrite (CaSO4)
Table 2.6 Simulation Result of Anhydrite (CaSO4)
temp(℃) SI** logIAP logK soluble
Conc.Ca2+
(mol/kg)
Total Conc.of Ca2+
(mol/kg)
precipation of CaSO4(S)
(mmol/kg)
25 -0.7 -4.97 -4.28 0.003273 0.00327341 0.000
50 -0.5 -5.07 -4.58 0.002917 0.00291743 0.000
75 -0.27 -5.18 -4.91 0.00257 0.0025704 0.000
100 -0.02 -5.29 -5.26 0.002265 0.00226464 0.000
125 0.23 -5.4 -5.63 0.001531 0.00199526 0.464
150 0.49 -5.51 -6 0.001 0.00175792 0.758
Fig 2.5. Conc. Of Anhydrite precipitation(CaSO4) vs Temperature
2). Aragonite (CaSO4)
Table 2.7 Simulation Result of Anhydrite(CaSO4)
Temp(℃) SI** logIAP logK soluble
Conc.Ca2+
(mol/kg)
Total Conc.of
Ca2+ (mol/kg)
precipation of CaSO4(S) (mmol/kg)
25 -0.32 -8.66 -8.34 4.67735E-05 4.6774E-05 0.000
50 -0.16 -8.7 -8.54 4.46684E-05 4.4668E-05 0.000
75 0 -8.82 -8.81 3.89045E-05 3.8905E-05 0.000
100 0.11 -9.06 -9.17 2.60016E-05 2.9512E-05 0.004
125 0.15 -9.44 -9.59 1.60325E-05 1.9055E-05 0.003
150 0.07 -10 -10.07 9.22571E-06 0.00001 0.001
Fig 2.6 Conc. Of Aragonite precipitation (CaSO4) vs Temperature
3). Barite (BaSO4)
4.64E-01
7.58E-01
0.00
0.20
0.40
0.60
0.80
1.00
0 20 40 60 80 100 120 140 160
Co
nc.
of
pre
pic
ipat
ion
(mm
ol/
kg)
Temp(℃)
3.51E-03
3.02E-03
7.74E-04
0.00E+00
1.00E-03
2.00E-03
3.00E-03
4.00E-03
5.00E-03
0 20 40 60 80 100 120 140 160
Co
nc.
of
pre
pic
ipat
ion
(mm
ol/
kg)
Temp(℃)
Table 2.8 Simulation Result of Barite (BaSO4)
temp SI** logIAP logK soluble
Conc.Ca2+
(mol/kg)
Total Conc.of Ba2+
(mol/kg)
precipation of CaSO4(S) (mmol/kg)
25 3.39 -6.58 -9.97 1.03514E-05 0.00051286 0.503
50 3 -6.68 -9.68 1.44544E-05 0.00045709 0.443
75 2.76 -6.78 -9.54 1.69824E-05 0.00040738 0.390
100 2.63 -6.9 -9.53 1.71791E-05 0.00035481 0.338
125 2.59 -7.02 -9.6 1.58489E-05 0.00030903 0.293
150 2.61 -7.14 -9.75 1.33352E-05 0.00026915 0.256
Fig 2.7 Conc. Of Barite precipitation (BaSO4) vs Temperature
4). Calcite (CaCO3)
Table 2.9 Simulation Result of Calcite (CaCO3)
temp SI** logIAP logK soluble
Conc.Ca2+
(mol/kg)
Total Conc.of Ca2+
(mol/kg)
precipation of CaSO4(S)
(mmol/kg)
25 -0.18 -8.66 -8.48 4.67735E-05 4.6774E-05 0.000
50 -0.04 -8.7 -8.66 4.46684E-05 4.4668E-05 0.000
75 0.11 -8.82 -8.93 3.42768E-05 3.8905E-05 0.005
100 0.21 -9.06 -9.27 2.31739E-05 2.9512E-05 0.006
125 0.24 -9.44 -9.68 1.44544E-05 1.9055E-05 0.005
150 0.15 -10 -10.15 8.41395E-06 0.00001 0.002
0.5030.443
0.3900.338
0.2930.256
0.00E+00
2.00E-01
4.00E-01
6.00E-01
8.00E-01
0 20 40 60 80 100 120 140 160Co
nc.
of
pre
pic
ipat
ion
(mm
ol/
kg)
Temp(℃)
Fig 2.8 Conc. Of Calcite precipitation (CaCO3) vs Temperature
5). Celestite (SrSO4)
Table 2.10 Simulation Result of Celestite (SrSO4)
temp SI** logIAP logK soluble
Conc.Ca2+
(mol/kg)
Total Conc.of
Ca2+ (mol/kg)
precipation of CaSO4(S) (mmol/kg)
25 0.86 -5.8 -6.66 0.00047 0.00126 0.791
50 0.91 -5.9 -6.8 0.00040 0.00112 0.724
75 0.96 -6 -6.97 0.00033 0.00100 0.673
100 1.04 -6.11 -7.15 0.00027 0.00088 0.615
125 1.13 -6.23 -7.36 0.00021 0.00077 0.558
150 1.24 -6.34 -7.58 0.00016 0.00068 0.514
Fig 2.9 Conc. Of Celestite precipitation (SrSO4) vs Temperature
0.000 0.000
0.005
0.006
0.005
0.002
0.00E+00
2.00E-03
4.00E-03
6.00E-03
8.00E-03
1.00E-02
0 20 40 60 80 100 120 140 160
Co
nc.
of
pre
pic
ipat
ion
(mm
ol/
kg)
Temp(℃)
0.7910.724
0.6730.615
0.5580.514
0.00E+00
2.00E-01
4.00E-01
6.00E-01
8.00E-01
1.00E+00
0 20 40 60 80 100 120 140 160
Co
nc.
of
pre
pic
ipat
ion
(mm
ol/
kg)
Temp(℃)
6). Dolomite (CaMg(CO3)2)
Table 2.11 Simulation Result of Dolomite (CaMg(CO3)2)
Fig 2.10 Conc. Of Dolomite precipitation (CaMg(CO3)2) vs Temperature
o Problems caused by precipitation of Minerals-Scale Formation:
1) Severe problem in the reservoir The damage of precipitation to reservoir mainly result in reducing the permeability. It could not only
reduce the production rate but also lower down the water-injection capacity.
2) Prevention of Scale Formation:
One of the most effective ways to prevent precipitation of minerals by avoiding mixing of incompatible
water. The following procedures can be used for the above incompatibility of SW and FW.
1. Diluting the offending ion to below solubility limit.
2. Removing Ba+2, Sr+2 or Ca+2 ions by ion exchange in the case of freshwater.
3. Sequestering or chelating the Ba+2, Sr+2 or Ca+2 ion.
Calcium Carbonate scale formation can be prevented by one of the following ways:
1. Lowering the pH.
2. Removing the calcium ion by one of the following means:
0.000
0.002
0.005
0.003
0.000 0.000
0.00E+00
1.00E-03
2.00E-03
3.00E-03
4.00E-03
5.00E-03
6.00E-03
0 20 40 60 80 100 120 140 160Co
nc.
of
pre
pic
ipat
ion
(mm
ol/
kg)
Temp(℃)
temp SI** logIAP logK soluble
Conc.Ca2+
(mol/kg)
Total Conc.of Ca2+
(mol/kg)
precipation of CaSO4(S)
(mmol/kg)
25 -0.38 -17.47 -17.09 0.00004 0.00004 0.000
50 0.07 -17.55 -17.63 0.00004 0.00004 0.002
75 0.28 -17.8 -18.08 0.00003 0.00004 0.005
100 0.2 -18.28 -18.48 0.00002 0.00003 0.003
125 -0.23 -19.06 -18.82 0.00002 0.00002 0.000
150 -1.06 -20.19 -19.13 0.00001 0.00001 0.000
1.) Ion exchange
2.) Chemical Treatment; Peptization, Sequestering or chelating.
3.) Dilution to lower the solubility limit.
REFERENCES
1. PE570 Reservoir Chemistry Curriculum- Spring 2014 by Professor Skule Strand and Professor
Tina Puntervold.
2. PHREEQC manual or Guide.
3. PET 565- Core Scale Modelling and Water Chemistry curriculum- Spring 2014 (UiS) bu Pål
Ø stebø Andersen.