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PET-570 Reservoir Chemistry Project Student name: Chunlei zhang Student number: 230286 Date:04/17/2015

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Page 1: Chemistry Lab Report

PET-570 Reservoir Chemistry Project

Student name: Chunlei zhang

Student number: 230286

Date:04/17/2015

Page 2: Chemistry Lab Report
Page 3: Chemistry Lab Report

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

Page 4: Chemistry Lab Report

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

Page 5: Chemistry Lab Report

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

Page 6: Chemistry Lab Report

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

Page 7: Chemistry Lab Report

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

Page 8: Chemistry Lab Report

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

Page 9: Chemistry Lab Report

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(℃)

Page 10: Chemistry Lab Report

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.

Page 11: Chemistry Lab Report

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)

Page 12: Chemistry Lab Report

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(℃)

Page 13: Chemistry Lab Report

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(℃)

Page 14: Chemistry Lab Report

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(℃)

Page 15: Chemistry Lab Report

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

Page 16: Chemistry Lab Report

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(℃)

Page 17: Chemistry Lab Report

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(℃)

Page 18: Chemistry Lab Report

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(℃)

Page 19: Chemistry Lab Report

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

Page 20: Chemistry Lab Report

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.