effects of pressure and temperature on well cement - ijens

International Journal of Engineering & Technology IJET-IJENS Vol:10 No:04 47

107704-2929 IJET-IJENS © August 2010 IJENS

I J E N S

Effects of Pressure and Temperature on

Well Cement Degradation by Supercritical CO2

Arina binti Sauki and Sonny Irawan, Geoscience and Petroleum Engineering Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh,

Perak, Malaysia

Abstract – The overall objective of this study was to

investigate the physical and chemical effects of supercritical CO2

attack on well cement at different temperature and pressure condition. The dissimilarity of attack was compared in two-

exposure conditions i.e. CO2-saturated brine and wet

supercritical CO2. Type of cement used for this invent was neat

cement, Class G and was prepared according to API

recommended practice 10B-2 by using Constant Speed Mixer. Curing of cement slurry and CO2 exposure test were done by

using Curing Chamber and Cement Autoclave. Measurement

and evolution of cement alteration against CO2 attack was

determined under various temperatures and pressure condition

at different exposure duration. Results from BackScattered Electron of Scanning Electron Microscopy (BSE-SEM), Energy-

dispersive X-Ray Spectroscopy (EDX), X-Ray Diffraction (XRD)

and compressive strength tester was analysed and studied. At

high temperature, 1200C, cement will lose its strength faster than

lower temperature, 400C. Same goes to pressure, the strength will lose faster in higher pressure, 140 bar as compared to lower

pressure, 105 bar. Faster reduction in strength was found in

CO2-saturated brine exposure compared to wet supercritical

CO2.

Index Term – Supercritical CO2, brine, alteration, compressive

strength, curing.

I. INTRODUCTION

OILWELL cement is used as a seal to secure and support

casing inside the well and prevent fluid communication

between the various underground fluid-containing layers or

the production of unwanted fluids into the well. It has been

used as the primary sealant in oil and gas wells throughout the

world and is manufactured to meet specific chemical and

physical standards set up by the API. There are eight class

listed in API Specification for Oilwell cement i.e. Class A to

H. The depth of well determines the difference types of

oilwell class used. For this invent, Class G cement was used

where it is intended to be used as a basic cement from surface

to a depth of 8000ft (2439m) as manufactured. Presently,

Class G oilwell cement is being used in oil and gas industry

for all types of cementation jobs.

Supercritical CO2 has a unique property that can improve

oil and gas production in the reservoirs. These would be a

great value for Enhanced Oil Recovery (EOR), Enhanced Gas

Recovery (EGR) and Enhanced Coal Bed Methane Recovery

(ECBM) project to boost the oil and gas production in their

fields. The focus of CO2 injection is normally found in the

areas that have a history of oil, natural gas and coalbed

methane production. It was first exploited in the mature fields

of the Permian Basin, West Texas, during the early 1970s for

EOR. In Natuna Gas Field (Greater Sarawak Basin in South

China Sea), high concentration of CO2 was found at the

production field. One of the solutions that could possibly do is

the reinjection of the CO2 gas into deep ground for storage or

for the use of EOR, EGR and ECBM project. However, the

major concern here is that the Portland cement is not stable in

CO2 rich environment. The main concern of CO2 exposure

should be taken to some existing oil and gas wells, which may

lead to an additional risk of properly sealing and may cause

potential CO2 leak paths [2]. The possible leakage pathway

would be from the reservoir to the shallower formation then

through that formation to the well cement.

Saline formations commonly have low flow velocities.

Some CO2 will remain as a separate free phase (hydrodynamic

trapping), that occurs because of the CO2 is less viscous than

brine, even at depths of more than 800m where CO2 is a

supercritical fluid [10] and will migrates upwards through

permeable pathways in the rock formation. CO2 behaves as a

supercritical fluid above its critical temperature of 31.6 °C and

critical pressure of 73.8 bar, expanding to fill its container like

a gas but with a density like that of a liquid. Nevertheless,

some CO2 will dissolve in the brine (solubility trapping) [10].

The dissolves CO2 will migrate along with the formation

water and leads to cement-carbonated brine contact. This

study evaluates cement degradation under two scenarios i.e. in

contact to wet supercritical CO2 (hydrodynamic trapping) and

in contact to CO2-saturated brine (solubility trapping).

When cement slurry is placed in the well, it is exposed to

elevated temperatures and pressures . The temperature and

pressure in oil & gas wells increases with depth. Typically, the

well temperature increases of about 3°C for each 100m depth.

Deeper than 20,000ft (6096m), the well temperature can easily

reach 175°C. Therefore, this experiment was performed in

different temperature and pressure condition to investigate the

effect of pressure and temperature on degradation of wellbore

cement by CO2.

Four major crystalline compounds in Portland cement are

tricalcium silicate (Ca3SiO5), dicalcium silicate (Ca2SiO4),

tricalcium aluminate (Ca3Al2O6), and tetracalcium

aluminoferrite (Ca4Al2Fe2O10). The most plentiful phases in

Portland cement are the silicates, comprising over 80 wt % of

the cement, mostly in the form of tricalcium silicate [4]. When

the compounds of Portland cement mixed with water, the main

hydration products formed are C-S-H and Ca(OH)2 [4].

Portland cement tends to degrade once exposed to CO2. In this

study, the mechanisms of interest were described as per

following to explain the CO2 attack to these main products in

the form of carbonic acid [2]:



I J E N S

CO2 dissociation:

CO2 + H2O → H2CO3 (1)

Cement Carbonation:

H2CO3 + Ca(OH)2 → CaCO3 (2)

C-S-H + H2CO3 → CaCO3+amorphous silica (3)

Calcium Carbonate dissolution:

CaCO3 + H2CO3 → Ca(HCO3)2 (4)

Ca(HCO3)2 + Ca(OH)2 → 2CaCO3 + H2O (5)

Initially, the CO2 dissolves in the water film through the

capillary pores of the cement resulting from internal

condensation or diffusion of environmental fluids , forming

carbonic acid in Equation (1). The acid then reacts with the

Ca(OH)2 in the cement as well as the C-S-H gels to form

CaCO3 in Equation (2) and (3). However, the CaCO3 can

continue to react with fresh carbonic acid in Equation (4)

which may leads to dissolution of CaCO3. In these reactions,

CaCO3 is converted to water soluble calcium bicarbonate that

will then coupled with the formation of water in Equation (5)

to produce CaCO3 and water. Consequently, the water can

tolerate for the additional dissociation of CO2 to form carbonic

acid. Thus, a continuation of the reaction process will occur.

As a result, the compressive strength of the set cement

decreases and the permeability increases, leading to the loss of

zonal isolation. As such, it is crucial to study how such cement

behaves at depth in the presence of CO2 rich fluids.

Many experimental studies have been published on

cement reactivity with CO2-rich fluid, which pressure and

temperature similar to CO2 storage facilities and oil and gas

production field that initially related to the alteration of well

cement in oil and gas production fields studied by Onan [5].

Recently, the invention was continued to well cement integrity

in the context of CO2 storage by Jose Condor [3], Emilia

Liteanu [8], V. Barlet et al [7], Barbara et al [4], W. Scherer

[11] and O. Brandvoll

et al [14]. In this invent, an

experimental study was done to evaluate the effects of

temperature and pressure variation against CO2 attack towards

this well cement. It was hardly to explain the exact value of

pressure and temperature in the reservoirs as the pressure and

temperature were varied dependence on the depth and

reservoir environments.

Barlet-Gouedard [1] has concluded that CO2 dissociation

stage starts earlier in CO2-saturated water than in wet

supercritical CO2. Under these severe conditions, Portland

cement is not resistant to CO2 and is not a good candidate for

cementing new wells for CO2 storage. In this research, the

dissimilarity of CO2 attacked in wet supercritical CO2 and

CO2–saturated brine condition was studied instead of CO2-

saturated water as Barlet et al [1] did at different pressure and

temperature conditions.

II. EXPERIMENTAL METHODOLOGY

A. Cement Slurry Samples Preparation

In order to prepare a cement slurry sample, the Class G

oilwell cement were mixed (35 seconds on Waring Blender at

high speed) with fresh water at a water-to-cement ratio of

0.44 by using Model 7000 Constant Speed Mixer according to

API Recommended Practice 10B-2 [9].

B. Curing Process

The cement samples were casted by slowly pouring the

degassed slurry down the cubical mould containing eight

cubic samples (2-inch-height x 2-inch-length) before

launching the curing chamber. The samples were cured for 8

hours, following the ISO/API standard procedures to simulate

the setting of the cement under reservoir condition. In order to

determine the effects of pressure and temperature of well

cement degradation, the pressure was kept constant when

temperature was varied and vice versa as shown in Table I.

TABLE I

TEMPERATURE AND PRESSURE VARIATION USED

Constant Pressure (140 bar)

Constant Temperature (400C)

Temperature

(0C)

40 Pressure

(bar)

105

120 140

After 8 hours curing period, the samples were demolded

and washed to remove the grease from their surface. The

cubes were then examined and only the most perfect cubes

were accepted for the testing to avoid any interference on the

results due to surface imperfections on the cubes. Then, the

cubes were weighed before submerged them in the water.

Prior to CO2 exposure, the cubic samples were cored to obtain

1.5-inch-diameter cylindrical samples with 2-in length for CO2

exposure.

C. CO2 Exposure Test

Cement Autoclave was used to expose cement core samples

(1.5in-D x 2in-L) after curing with supercritical CO2 under

two situations: wet supercritical CO2 and CO2-saturated brine.

The CO2 experiments were performed under static condition.

This condition was considered as a realistic simulation of the

CO2-exposure conditions at the formation/ cement sheath

interface.

The hardened cement samples were exposed to brine

(0.01M NaCl) solution saturated with supercritical CO2 under

identical condition with curing as shown in Table I. The

volume content of the CO2 fluids in the vessel was about 40%

brine and 60% CO2 at atmospheric pressure and room

temperature. This experiment was performed at different

durations: 24 hours, 72 hours and 120 hours.

To remove each sample, the pressure was released slowly

over a period of four hours to prevent sample damage. The

samples were then photographed and weighted. pH of residual

brine was also measured by using pH meter after each

duration of experiment. Finally, mechanical strength, chemical

and microscopic composition were systematically analyzed.



I J E N S

D. Alteration Measurements

Measurement was taken before and after CO2 exposure

to compare the alteration results of the followings:

i. The mineralogical composition of the samples were

identified by using XRD and EDX.

ii. The specific phases within the cement and the

microstructural development and alteration front of the

samples are verified by BSE-SEM.

iii. Compressive strength of cement core sample was

obtained by using OFITE Automated Compressive

Strength Tester.

iv. Other indirect measurements such as pH of the sample

brine, mass of the cement samples and the dimension of

the cement samples are measured by using pH meter,

Balance and Vernier Caliper.

III. RESULT AND DISCUSSION

A. Effects of Different Temperature Conditions on Cement

Degradation By Supercritical CO2

Based on the observation from BSE-SEM image before

CO2 attack showed that samples cured at 1200C had smaller

and more uniform distributed unhydrated cement grains

throughout the solid matrix of the cement compared to sample

cured at 400C as shown in APPENDIX [I]-A. This was shown

that higher degree of hydration of cement grain could be seen

at rising temperature. The hydration showed that the reaction

between water and cement grains to produce Ca(OH)2 and C-

S-H was greater at 1200C which may leads to the formation of

smaller unhydrated grains compared to the low temperature,

400C. This may provide large impact on the CO2 to attack in

term of carbonation process between C-S-H and Ca(OH)2 as

per Equation (2) and (3) to occur.

Result from cement sample after CO2 exposure in brine

solution showed the depth of penetration always increased by

time. A slight increase in depth of penetration was clearly

observed at the rim of sample by using BSE-SEM image as

early as 24hours of CO2 attack as shown in APPENDIX [III].

Sample exposed at 1200C showed greater depth of penetration

after 120-hours of attack up to 0.78 mm whereas sample

exposed at 400C had smaller depth of penetration that was up

to 0.55mm deep after 120hours of CO2 attack. Based on

theory [16], the outer-product C-S-H gel become denser and

does not fill the capillary pore space as effectively at elevated

temperature and thus the microstructure is more

heterogeneous. This pore space may provide easier CO2 to

attack in the form of carbonic acid. The CO32-

ion from acid

carbonic will attack the leached Ca2+

ion from C-S-H and

Ca(OH)2 to produce CaCO3 and amorphous silica. Extensive

reduction of Ca can be shown in APPENDIX[V] which about

30-40weight% at high temperature, 1200C sample rather than

about 5-weight% reduction at low temperature, 400C sample.

Compressive strength on sample exposed at 1200C

showed strong reduction that was about 80% rather than about

70% in sample exposed at 400C after 120-hours of CO2 attack.

Based on cement chemistry theory [16], cements lose much of

their strength at greater temperature. These effects could be

related to the increased rate of silicate polymerization at

elevated temperatures, more than 1100C, which densifies and

stiffens the C-S-H as it forms [16]. This loss of strength which

is accompanied by an increase in permeability, caused by the

formation of an alpha hydrate form of calcium silicate which

has no cementitious value [17]. The production of amorphous

silica from reaction between C-S-H and acid carbonic may

decrease the compressive strength of this cement due to the

lack and highly porous of its structure and may provide easier

acid to attack. Apart from that, the reduction in strength was

believed because of the loss of silica which hardened the

cement paste. Result from EDX analysis from APPENDIX

[VI] showed the reduction in s ilica in the range of 5-10

weight% at 1200C after 120-hours of CO2 attack as a result of

loss in compressive strength of cement. The diverse degree of

compressive strength evolution was also due to the production

of calcium carbonate from carbonation process that was

believed can increase the compressive strength of cement

sample.

Mass alteration of the sample did not show any significant

different. The mass loss in sample exposed at 1200C was

greater about 0.5% than sample exposed at 400C after 24-

hours of CO2 attack due to the higher degree of hydration

occurred at higher temperature. The less water filled the

capillary pore of the cement may reduce the mass of cement

sample. However, the mass kept increasing after 72-hours of

CO2 attack resulting from higher carbonation rate of cement

by CO2. The formation of CaCO3 was believed increase the

mass of sample and strong degradation at the rim of sample

may cause the reduction of mass in cement sample after 120-

hours of CO2 attack.

Hydrated cement is a highly alkaline material that is

chemically stable only when pH more than 10 [11]. Hence,

the introduction of CO2 in brine will make the downhole

conditions extremely aggressive against the existing well

cement. Sample of brine was taken out from vessel after each

moment of CO2 attack duration and was tested in pH. The

result was shown in APPENDIX [VIII]. It was observed that

CO2 attack-related decrease the pH of brine for sample

exposed at high temperature, 1200C from 8 to 7.5 after 24-

hours. However, the reduction in pH at lower temperature,

400C was faster that was about 6.5 after 24-hours. This delay

in deduction was believed due to temperature variant. The

capacity and solubility of CO2 dissolves in brine decrease with

rising temperature [11]. Apart from that, the aggressive

removal of alkaline OH- from pore water filled at high

temperature will react with CO32-

from acid carbonic to form

Ca(OH)2 made this process a little bit delay in pH deduction

until the equilibrium phase was achieved and decrease the pH

around 6.78 after 120-hours of attack. It was believed from

previous researcher that Ca(OH)2 constitutes the alkaline

reserve to provide acid resistance [11]. It was a key

component in hardened cement that buffers the pH of the

porewater [11].



I J E N S

B. Effects of Different Pressure Conditions on Cement

Degradation By Supercrtical CO2

In term of pressure, slight increase in depth of penetration

can be observed in sample exposed at 105 bar that was up to

0.65mm deep compared to 140 bar that was merely about

0.55mm after 120hours of CO2 attack in brine solution as

shown in APPENDIX [III]. It was happened due to higher

carbonation process occurred at lower temperature. This can

be shown from the depletion of calcium at low pressure, 105

bar as shown in APPENDIX [V] that was about 30-weight%

as compared to high pressure at about 2-weight% in reduction.

The outcome from compressive strength tester on sample

exposed to CO2 attack in brine solution at 105 bar showed an

increment in strength which was about 50% after 24-hours of

exposure. However, after 120-hours, the compressive strength

shows a slight decrease about 10%. In contrast with sample

exposed at 140 bar, the compressive strength showed a

reduction as early as 24-hours of CO2 attack which was almost

20% and kept decreasing up to 85% after 120-hours of CO2

attack. The increment of compressive strength for sample

expose at 105bar was believed due to the higher rate of

carbonation occurred and produced more CaCO3. The

formation of CaCO3 had been reported to decrease

permeability and increase the compressive strength of the

cement since the solid CaCO3 filled the capillary pore of

cement grains [4]. This can be proved from strong depletion of

Ca that was about 50-weight% at 105 bar as compared to

sample exposed at 140 bar which was merely about 6-

weight% of reduction.

Reduction in mass can be seen in sample exposed at

140bar in the range of 1-2% after 120-hours of CO2 attack in

brine solution as shown in APPENDIX [VII]. However, mass

was gained in sample exposed at 105 bar up to 1.8% at 72-

hours exposure prior to slightly depletion at 0.5% after 120-

hours exposure. The increased of mass resulting from higher

carbonation rate of cement by CO2. The formation of CaCO3

was believed increase the mass of sample and strong

degradation at the rim of sample may cause the reduction of

mass in cement sample.

Virtually similar trend of pH evolution was observed in

both samples exposed at 105 bar and 140 bar. However,

sample exposed at 140 bar was having slightly lower pH after

120-hours of CO2 exposure in brine solution that was 6.06 as

compared to sample exposed at 105 bar that was 6.17 as

shown in APPENDIX [VIII]. It was believed that the

solubility of CO2 in brine will increase at rising pressure [11].

Hence, it reduced the pH greater at higher pressure.

C. Effects of Cement Degradation by Supercritical CO2 in

wet supercritical CO2 and CO2-saturated brine

Examination with BSE-SEM and EDX analysis, revealed

that the exposure of cement by CO2 under wet supercritical

CO2 and CO2-saturated brine altered the cement in four zones

as shown in Figure 1. Zone 1 was the innermost unaltered

cement surrounded by three altered zone. Zone 2 was a 50 to

100μm-large zone exhibited a slight increase in porosity and

decrease in Ca(OH)2 while Zone 3 was a ring of decreased

porosity and increased calcium content that is about 100 to

200μm-large zone. The BSE-SEM image of Figure 1 indicates

that zone 3 was less porous than any other regions including

the unaltered cement (zone 1). Calcium carbonate (CaCO3)

precipitates in the cement matrix characterize this front. From

XRD analysis, only CaCO3 in the form of calcite and

Aragonite were visible in all carbonated samples. No vaterite

contain was found. The outermost evidence of attack was zone

4 (200 to 400μm-large zone), which exhibited a significant

increase in porosity and highly depleted in calcium as a result

of strong degradation of the cement in this zone. From the

overall analysis, all samples tested were having the same

distinct altered zone as Figure 1 except for being poles apart in

depth of penetration. It was observed that the sample exposed

in wet supercritical CO2 had wider zone 3 than sample

exposed to CO2-saturated brine as shown in APPENDIX [II]-

C. It shows that higher carbonation occurred in wet

supercritical CO2 which produced more CaCO3.

Fig. 1. BSE-SEM image of cement degradation after a 120-hr-CO2 attack in

brine solution at 140 bar and 40 deg C.

Roughly the degradation effect can be detected by

viewing at the rim of the cement samples. The outer surface of

the cement exposed to CO2-saturated brine was orange in

color and smooth texture while wet Supercritical CO2 was

light grey and rough texture as shown in Figure 2. The change

of colour for sample submerged in brine from grey to orange

was explained due to change in oxidation state of the iron

contain in neat cement. The increase in ring thickness was

observed at each moment as shown in Figure 3.

Fig. 2. Different colour of ring between cement exposed to wet supercritical

CO2 and CO2-Saturated Brine.



I J E N S

Fig. 3. Alteration at the rim of cement thin section under different exposure

durations for cement samples exposed to wet supercritical CO2 and CO2-

Saturated Brine at 40 deg C and 105 bar.

Depth of penetration for sample exposed to wet

supercritical CO2 was greater compared to sample exposed in

CO2-saturated brine at each moment of exposure duration as

shown in APPENDIX [III]. This was believed due to the

solubility of CO2 in water, which filled the capillary pores of

sample in wet supercritical CO2 was greater than the solubility

of CO2 in brine solution. High solubility may provide higher

carbonation rate of attack. Thus, enlarge deeper depth of

penetration.

In average, the mass of sample exposed in wet

supercritical CO2 increase 2% to 7% more than CO2-saturated

brine due to the higher carbonation occurred in wet

supercritical CO2 rather than those in CO2-saturated brine.

However, in contrast with depth, the compressive

strength decrease more in CO2-saturated brine rather than wet

supercritical CO2 in the range of 20% to 50% after 120-hours

of CO2 exposure as shown in APPENDIX [IV]. Higher

carbonation in wet supercritical CO2, may produce more

CaCO3 which can increased the compressive strength of

cement.

IV. CONCLUSION

Based on experiment made, temperature and pressure do

play an important role for the chemical and physical alteration

of cement by CO2 attack. It was observed that cement tends to

degrade and loss its strength once expose to supercritical CO2

environment. The loss in compressive strength was greater at

increase temperature due to the formation of alpha-calcium

silicate. For pressure, the loss of compressive strength was

greater at increased pressure. Formation of CaCO3 was

observed can increase the compressive strength of cement

sample. Greater carbonation in wet supercritical CO2, slow

down the reduction in strength as compared to CO2-saturated

brine. This carbonation can give a temporary strength but

cannot be guaranteed for the long term exposure. Same goes

to the depth of penetration, although it can be seen in a very

little value for this short term of CO2 exposure, it will possibly

destroying zonal isolation in a long period since the depth of

penetration kept increasing by time. As such, it is important to

study these cement behaviors on supercritical CO2 attack in

order to find a great solution for CO2 resistance cement

additive that has been major concerns of many researchers

nowadays.

APPENDIX [I] A. Before CO2 Attack at Constant Pressure and Different

Temperature Conditions

Fig. 4. Sample cured at 40

0C

Fig. 5. Sample cured at 120

0C

B. Before CO2 Attack at Constant Temperature and Different Pressure Conditions

Fig. 6. Sample cured at 105 bar



I J E N S

Fig. 7. Sample cured at 140 bar

APPENDIX [II] A. Degradation at the rim of oil well cement after 120 hours of

Supercritical CO2 exposure in brine solution at constant

pressure and different temperature:

Fig. 8 Sample exposed at 40

0C

Fig. 9. Sample exposed at 120

0C

B. Degradation at the rim of oil well cement after 120 hours of

Supercritical CO2 exposure in brine solution at constant

temperature and different pressure:

Fig. 10. Sample exposed at 105 bar

Fig. 11. Sample exposed at 140 bar

C. Degradation at the rim of oil well cement after 120 hours of

CO2-saturated brine and wet supercritical CO2 exposure at

pressure of 140 bar and 400C:

Fig. 12. Sample exposed in CO2-saturated brine



I J E N S

Fig. 13. Sample exposed in wet supercritical CO2

APPENDIX [III]

Fig. 14. Depth of penetration evolution against exposure duration at constant

temperature, 400C and constant pressure, 140 bar

APPENDIX [IV]

Fig. 15. Compressive strength evolution against exposure duration at constant


APPENDIX [V]

Fig. 16. Calcium content evolution after 120-hour of CO2 attack at constant


APPENDIX [VI]

Fig. 17. Silica content evolution after 120-hour of CO2 attack at constant


CONSTANT

TEMPERATURE

CONSTANT

PRESSURE

CONSTANT

TEMPERATURE

CONSTANT

PRESSURE

CONSTANT

TEMPERATURE

CONSTANT

PRESSURE

CONSTANT

TEMPERATURE

CONSTANT

PRESSURE



I J E N S

APPENDIX [VII]

Fig. 18 Mass evolution against exposure duration at constant temperature,

400C and constant pressure, 140 bar

APPENDIX [VIII]

Fig. 19. pH evolution against exposure duration at constant temperature, 40

0C

and constant pressure, 140 bar

NOMENCLATURE α = constant related to the rate of diffusion of ionic species API = American Petroleum Institute BSE-SEM = BackScattered Electron Scanning Electron Microscopy

Ca2SiO4 = Dicalcium Silicate Ca3SiO5 = Tricalcium Silicate Ca3Al2O6 = Tricalcium Aluminate

Ca4Al2Fe2O10 = Tetracalcium Aluminoferrite CaCO3 = Calcium Carbonate

Ca(OH)2 = Calcium Hydroxide Ca(HCO3)2 = Calcium Bicarbonate CO2 = Carbon Dioxide C-S-H = Calcium Silicate Hydrate gels

EDX = Energy-dispersive X-Ray Spectroscopy ECBM = Enhanced Coal Bed Methane Recovery EGR = Enhanced Gas Recovery EOR = Enhanced Oil Recovery

H2CO3 = Carbonic Acid H2O = Water L = Depth of Carbonation (mm) SEM = Scanning Electron Microscopy

t = T ime of Exposure (hr) XRD = X-Ray Diffraction

ACKNOWLEDGMENT

The authors thank to Lafarge Malaysia for the contribution of

Class G cement for this research.

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CONSTANT

TEMPERATURE

CONSTANT

PRESSURE

CONSTANT

TEMPERATURE

CONSTANT

PRESSURE



I J E N S

[13] Gaetan Rimmelea.*, Veronique Barlet-Gouedard

a, Olivier Porcherie

a,

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