Large Scale Flue Gas CO 2
Recovering / CO 2 Cost andTo t a l S y s t e m f o r C O 2
Enhanced Oil Recovery

Absorber
Regenerator
Flue gas cooler

SHOJIRO IWASAKI* 1
TAKASHI KAMIJO* 1
TORU TAKASHINA* 2
HIROSHI TANAKA* 2

Enhanced oil recovery (EOR) in which CO2 is injected into reservoirs in order to increase crude oil production has
been commercialized mainly in the US. By utilizing flue gas CO2 recovery technologies, CO2 recovered from the fluegas of power generation plants can be applied to EOR. When a flue gas CO2 recovery plant is used as a source of CO2
for CO 2 EOR, the plant comprises a large part of the total investment, and CO 2 recovery costs greatly affect oil
recovery cost. The comprehensive economic studies are made for CO2 recovery plant in application of EOR projects
based on various parameters which include capacity of CO2 recovery plant, utility cost, pipeline cost and any otheroperational requirements. This paper focuses on some of these economic study results to identify which parameters
impact on CO2 recovery cost. Consideration is also given to the selection of flue gas sources and plant locations withthe aim of further minimizing recovery costs.
The first commercial plant for recovering CO2 fromflue gas in the world was constructed about 20 years ago
based on technology developed by Dow Chemical Company. At that time, there was already an idea to apply aflue gas CO 2 recovery plant to EOR. In fact, a 1000 t/d(19 MMSCFD(NOTE2)) flue gas CO2 recovery plant was constructed in 1983 in Lubbock, Texas for the purpose of
EOR. However, the plant was dismantled in 1985 foreconomic reasons.
The technology developed by Dow Chemical Company
used monoethanolamine solvent, which had long beenused for the absorption of acid gas. This method consumes much energy and leads to the violent deteriorationof the solvent. In addition, it still has many technicalproblems such that it requires a metal-based corrosion
inhibitor to protect against and prevent corrosion. Since
then, Fluor Daniel Inc. acquired its license from Dow
Chemical Company for the chemical absorption process.
However, only limited technical improvement could be
realized in the process.

1. Introduction
CO2 EOR(NOTE 1) is well known as an enhanced recovery method used in reservoirs that can theoretically leadto an increase ultimate oil recovery. The method wascommercialized in the U.S. during the 1970s, and hassince contributed to increasing oil production by approximately 200 000 barrels per day. The CO 2 EOR is alsoestablished in Canada, Turkey, and Hungary.
Almost all of the CO2 used for EOR in the U.S. is generally supplied from gas fields through the CO2 transport
pipelines. Even in those areas where there is no largescale CO 2 source, CO 2 can be recovered from flue gas
discharged from the stacks of various plants by utilizing
flue gas CO2 recovery plants. CO2 EOR can then be carried out by supplying the CO 2 thus recovered toneighboring reservoirs. The application of CO2 recovery
from flue gas for EOR also has an added beneficial environmental effect of reducing the discharge of CO 2 as aresult of the CO2 sequestration in the reservoir.

NOTE 2:MMSCFD = 106 standard cubic feet per day
MMSCF CO2 = 106 standard cubic feet of CO2
feet of CO 2 = 52.6 metric ton of CO2

NOTE 1:
Although a secondary crude oil production suchas water flooding is used, typically 60 to 70% of
oil cannot be recovered from reservoirs with thismethod. EOR belongs to a tertiary crude oil production capable of further recovering oil. In the
CO 2 EOR, a miscibility condition (state in which
CO 2 is freely mixed in oil under supercriticalpressure) is formed in a reservoir to remarkably
increase an crude oil production.

During the first part of the 1990s, MHI, working in
joint cooperation with the Kansai Electricity Co., Inc.,
began to develop a new flue gas CO2 recovery process forthe large-scale CO 2 recovering discharged from power
generation plants, and in 1998 delivered a first commercial plant with a maximum recovery rate of 210 t/d(4 MMSCFD) to Malaysia.
Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 41 No. 4 (Aug. 2004)*1 Plant and Transportation Systems Engineering & Construction Center*2 Hiroshima Research & Development Center, Technical Headquarters

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The technology developed by MHI has several excellent features, including lower energy consumption andeasy maintenance of the solvent. In addition, the process can also be used to recover a large amount of CO2 at
low cost for the purpose of EOR and is an effective countermeasure against global warming. MHI has also been
actively taking part in many projects in order to achieve
CO 2 EOR using the flue gas CO 2 recovery plant in the
Middle East and South East Asia in the near future.
Needless to say, in CO 2 EOR, the cost of CO 2 has amajor impact on the cost of oil production. When theflue gas CO2 recovery plant is constructed for EOR, feasibility of EOR depends upon whether or not a large
amount of CO2 can be recovered and supplied to the reservoir at low cost.
In this study, factors affecting CO2 recovery cost were
quantitatively examined assuming that CO2 is recoveredfrom the large capacity flue gas sources of boilers andgas turbines and that CO 2 EOR is performed using an
MHI flue gas CO2 recovery plant.

oil production equipment include the incorporation of theflue gas CO2 recovery plant, CO 2 compression/dehydration unit, CO2 pipelines, CO2 injection wells for injecting
CO2 into the reservoirs, and a facility for separating CO2
from associated gas.
To prevent wet carbonate corrosion, recovered CO 2from the flue gas is dehydrated until its dew point islowered to less than 0 oC. In order to transport and inject the CO 2 into underground reservoirs, the CO 2 gas
needs to be compressed up to a critical pressure of 74 kg/
cm2G or higher, and fed to the reservoirs through a CO2
pipeline.
Oil production is stimulated by the presence of CO 2.
Concurrent with oil production rate increases, CO2 is also
produced since it is present in the crude oil and “CO 2
breakthrough” occurs. The associated gas requires processing in order to recover the valuable CO 2 for recycle
usage for EOR as well as to eliminate CO2 from the residue hydrocarbon product such as gas product or natural
gas liquid.
The CO 2 recovered in the CO 2 separating plant ismixed with the CO 2 supplied from the flue gas CO 2 recovery plant and re-injected into the reservoirs. The CO2of the associated gas is in high partial pressure and,
therefore, can be separated easily with less energy thanthat required when recovering CO2 from the flue gas. In
short, operation costs can be reduced by effectively utilizing the CO2 separated from the associated gas.

2. Outline of overall CO2 EOR system
Figure 1 shows a schematic view of the overall CO 2
EOR system with the flue gas CO2 recovery plant. The
basic configuration of the equipment used to separate
oil from the associated gas and water does not differ fromthat used in normal oil production facilities. The points
where the equipment in this system differ from typical

Treated flue gas
Sources of flue gas,such as boilers andgas turbines

Sales natural gas

Test separator

Flue gas

CO2 recovery plant,

CO2

CO2 dehydration/
compression unit

Associated gas
CO2 separation plant

Manifold
Separator

CO2 supply lineGas
scrubberHeaterFree
waterknockout

Water
Oily water

Crude oil

Emulsion
Emulsion

Production well
Injection well

Gas knockout drum

Oil tank

Water
Water tankWater
injectionpump

Fig. 1 Concept of overall system for CO2 EOR

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 41 No. 4 (Aug. 2004)2

reservoir, these substances are limited to less than 4
vol.%. Since nitrogen also raises minimum miscible pressure, it is limited to a maximum of less than 5 vol.%.
Although hydrogen sulfide is somewhat beneficial to increase miscibility condition, it is limited to less than 100
ppmv only for safety reason.
Since the MHI's flue gas CO2 recovery plant utilizes achemical absorption process, the purity of the recovered
CO2 is as high as 99 vol.% or higher. The major impurities include nitrogen and oxygen and, therefore, nosignificant problems occur when they are applied to EOR.
3.2 Required amountThe amount of additionally recovered crude oil when
CO 2 is injected, that is, the effect of CO 2 EOR varies
according to the subject reservoir. In general, the amountof crude oil further produced by the CO2 supplied is reported to be 3 to 20 MMSCF/bbl. When the required
amount of CO 2 is 3 to 8 MMSCF/bbl, the effect of CO 2
EOR is said to be high.
3.3 Gas pressure
CO 2 is typically transported in a supercritical statethan critical pressure (74.3 kg/cm2G) to prevent the CO2from separating into gas-liquid two phase in the pipelines, which would result in an increased pressure loss
and hammering for pipelines. Thus, Usually, a CO 2 delivery pressure of 2 000 psig is used at the inlet of the
CO 2 pipeline.
Once the CO 2 has been transported to the reservoir,
it is further compressed for injection to suit the well headpressure into the reservoir. A special pump is typicallyused to compress the CO2 in the EOR site.

Various facilities are available for use in separating
CO 2 from associated gas (CO 2 recycle plant). Some ofthese facilities only consist of the compression unit whileothers use various systems such as the membrane
method, absorption method, or distillation method.
These methods each have their respective merits anddemerits, and an optimum method is selected at eachsite according to the concentration of CO2 in the associated gas and the product specifications of hydrocarbons.
Typically, CO2 EOR involves injecting CO2 and water
alternately. CO2 gives a highly carbonate corrosive environment if it contains moisture. Corrosion-resistantsteels or coated materials are used, or a corrosion inhibitor is used for the production equipment such as CO2
injection wells and oil gas separators because the equipment has portions that are easily prone to corrosion.
When CO 2 EOR is performed in a reservoir that iscurrently under normal production, investment costs forthe flue gas CO2 recovery plant and the CO 2 compression/dehydration unit comprise about half of the total
investment cost involved, though it differs much depending upon the conditions.
Accordingly, this study focuses on the recovery cost of
CO 2 produced using the flue gas CO2 recovery plant andCO2 compression/dehydration unit in the following.

3. Requirements for CO2 used in EOR
3.1 Purity of CO2 gas
CO 2 forms a miscibility condition in a reservoir, i.e.,a state in which CO 2 is freely mixed in oil under
supercritical pressure to remarkably lower the viscosityof the oil. This leads to significantly increasing the ultimate oil recovery. Impurities in CO 2 affects the phaseboundaries and raises the CO2 minimum miscible pressure (pressure achieving miscibility condition) of thereservoir, which becomes the cause of severe corrosionof the oil production equipment.
Accordingly, the CO2 specification must be controlled
so that any impurities mixed in the CO 2 are within allowable contents. The allowable contents of the
impurities are dependent on the reservoir formation andthe injection method. For example, in CO2 EOR that is
now performed mainly in the Western Texas in the US,
impurities such as methane (CH4), ethane (C2H6), nitrogen, and hydrogen sulfide are controlled so that the
purity of CO2 is 94 vol.% or higher. Since methane andethane contained in CO2 raises the miscible pressure of

4. Study conditions
4.1 Study cases
MHI flue gas CO 2 recovering process was chosen as
appropriate CO 2 capture technology for performing CO2
EOR. Consideration was given to the four cases outlined in Table 1 as examples of recovering CO2 from theboilers and gas turbines of power generating plants andindustrial plants.
Natural gas is used as fuel in each of the cases of theboilers and gas turbines noted above. In addition, theflue gas do not contain any SOx, as it must undergo desulfurization treatment on the upstream side of the fluegas CO2 recovery plant. In all cases, a dedicated auxiliary boiler is installed to supply the steam required tooperate the CO2 recovery plant and CO2 compressor.

Table 1 Study basis
Study cases

CO2 concentration (vol%)CO2 recovering capacity (t/d) (MMSCFD)

Boiler case 1
Boiler case 2
Gas turbine case 1
Gas turbine case 2

8.5
8.5
3.0
3.0

5 260 (100)
3 160 (60)
4 730 (90)2 630 (50)

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 41 No. 4 (Aug. 2004)3

SteamLow pressure
steam
BoilerCO2
recoveryplant

2 000 psig

CO2 dehydration/
compression unit

CO2 pipeline

Condensed
water

Auxiliary
boiler: Calculated range of capital cost
Fig. 2 Boiler case
Steam
Low pressure
steam

Gas
turbineWaste
heatboilerCO2
recoveryplant

CO2 dehydration/
compression unit

2 000 psig

CO2 pipeline

Condensed
water

Auxiliary
boiler: Calculated range of capital cost
Fig. 3 Gas turbine case

Figures 2 and 3 show the system configurations of
the flue gas CO 2 recovery plant and the CO 2 compression/dehydration unit. The CO2 recovered from the fluegas of the boilers and gas turbines is compressed anddehydrated, and fed into the CO 2 pipeline. The conditions under which the CO 2 is supplied are estimated tobe 2 000 psig in pressure and 45 oC in temperature. The
CO2 compressor is of single train at the four-stage.
4.2 Basis for calculating capital cost
The capital cost (CAPEX) consists of the total of theinitial investment cost to construct the flue gas CO2 recovery plant, the CO 2 compression/dehydration unit, andauxiliary boiler for flue gas CO2 recovery plant. The plant
cost was calculated based on the results of delivering commercial plants by MHI in the Middle East countries. The
depreciation of the capital costs were assumed to be 10%
based on the fixed amount method.

4.3 Basis for operation cost
To obtain the operation cost (OPEX), expenses associated with the operation of the flue gas CO 2 recovery
plant, that is, expenses for utilities, operators, maintenance, consumable items, and spare parts, as well as
general plant and administrative expenses were totaled.
The unit price of the utilities was varied in the area
described below. The values of the unit prices of fuelgases in areas in the Middle East where the fuel gas
cost is inexpensive were taken as typical examples.
The ratio of the expenses for operators, maintenance,
consumable items, and spare parts, as well as generalplant and administrative expenses to operating costs was
small. These expenses were considered to be constant,
as shown in Table 2
2.

5. Relation between CO2 recovery cost and cost-effective factors
5.1 CO2 recovery cost (base case)
When the utility cost is used as a base, namely, when
the fuel gas cost is US$1.0/MMBtu, cooling water cost is
US 1.5 cents/t, and power cost is US 3.0 cents/kWh, theresults of trial calculations of CO2 recovery and compression costs (hereafter referred to as CO2 recovery costs)
3 When attention is paid to theare as shown in Table 3.
sum total of the capital cost and operation cost, plantboiler case 1, which has the largest CO 2 recovery volume and highest CO2 concentration in the flue gas, has
the lowest CO2 cost.

Table 2 Basis for operating cost
Cost of Utilities
Fuel gas (US $/MMBtu)

0.5

1.0 (Base)

1.5

Cooling water (US /t)

1.0

1.5 (Base)

2.0

Electricity (US /kWh)2.0

3.0 (Base)

4.0

Operators(US $/Y)
Maintenance (US $/Y)

0.25

*

NOTE: Operator includes analyzer and engineer.
Maintenance includes consumable items and spare parts.
Maintenance costs are set at 1% (annually) of the capital cost.

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 41 No. 4 (Aug. 2004)

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Table 3 Study results
CO2 content
in flue gas(vol %)Case

CO2 recovering On-stream
capacityfactor(MMSCFD)
(%)
100

90

0.472

0.444

0.916

Boiler case 2

8.5

60

90

0.533

0.515

1.048

Gas turbine case 1

3.0

90

90

0.609

0.830

1.439

Gas turbine case 2

3.0

50

90

0.609

0.838

1.446

ries of up to a maximum of 100 MMSCFD using current technology.
Basically, the flue gas CO 2 recovery plant is a facility that enjoys the merits of scale construction.
In the boiler case in which the plant can be constructed in one series capable of recovering CO 2
ranging from 50 to 100 MMSCFD, the plant can enjoy the merits of scale. The CO 2 recovery cost issignificantly reduced due to the increased CO 2 recovering capacity.
Thus, from the above it can be seen that boiler fluegas can be selected as the most advantageous sourceof exhaust gas due to its higher concentration of CO2
compared with the other sources.
(2) Relation between flue gas cost and CO 2 recovery
cost
The relation between the cost of recovering CO 2
and the fuel gas cost is shown in Fig. 5
5. The CO 2
recovery cost decreases as the fuel gas cost becomesless. When CO2 is recovered from boiler flue gas witha high concentration of CO 2, the CO 2 recovery cost
falls within a range of US$0.8 to 1.0/MSCF.
A flue gas CO 2 recovery plant requires a large
amount of low pressure steam to regenerate the solution and, hence, it could be confirmed that the CO 2
recovery cost is affected largely by the fuel gas which
produces the steam. Thus, when constructing the fluegas CO 2 recovery plant, it is important to select anarea where the fuel gas cost is low.

Cost of CO2 recovery (US$/MSCF)

Cost of CO2 recovery (US$ /MSCF)(US $/MSCF)

Total cost

8.5

2.0

Gas turbine
1.5

BoilerFuel gas: 1.0 $/MMBtu
Cooling water: 1.5 /t
Electricity: 3.0 /kWh0.50Operation cost
(OPEX)(US $/MSCF)

Boiler case 1

5.2 Relation between CO 2 recovery cost and costeffective factors(1) CO 2 recovering capacity
The relation between the CO 2 recovery cost andthe CO2 recovering capacity from the flue gas CO2 recovery plant is shown in Fig. 44.
Compared with the gas turbine case, the boiler casehas a lower CO 2 recovery cost. This is because theCO 2 concentration of boiler flue gas is higher thanthat of gas turbine exhaust gas, consequently, theutilities required to recover CO 2 are less, and since
the size of the equipment which handles the exhaustgas is smaller, the capital cost accordingly results insmaller.
In both the gas turbine and boiler cases, the CO 2
recovery cost decreases as the CO2 recovering capacity increases. It remarkably decreases in the case of
the boiler.
In addition, the equipment cost becomes higher
since the concentration of CO 2 in gas turbine exhaust gas is low and the large amount of exhaustgas must be treated. The maximum CO 2 recovering capacity from the flue gas CO 2 recovery plantin the gas turbine case that can be constructed in
one series using current technology is up to 50
MMSCFD.
On the other hand, with the boiler flue gas which
is higher in CO 2 concentration than the gas turbine
exhaust gas, the plant can be constructed in one se-

1.0

Capital cost
(CAPEX)(US $/MSCF)

20

40

60

80

100

120

140

Amount of CO2 recovery (MMSCFD)

2.0
Gas turbine
1.5
Boiler1.0
Cooling water: 1.5 /t
Electricity: 3.0 /kWh
0.5
0.0

0.5

1.0

1.5

2.0

Fuel gas cost ( /t)Fig. 4 Relation between CO2 recovery cost and CO2 recovery
capacity in the flue gas CO2 recovery plantFig. 5 Relation between CO2 recovery cost and fuel gas cost

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 41 No. 4 (Aug. 2004)

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Cost of CO2 recovery (US$/MSCF)

2.0(3) Relation between cooling water cost and CO 2 recovery cost
The relation between the CO2 recovery cost and theGas turbine
1.5
6. Though thecost of cooling water is shown in Fig. 6
degree of reduction in the CO 2 recovery cost is nothigher than that for the fuel gas cost, it reduces as a
Boiler1.0
result of a lowering of the cost of cooling water. A relatively large amounts of cooling water is used to cool
Fuel gas: 1.0 $/MMBtu
the flue gas and the top section of the amine solution
Electricity: 3.0 /kWhregenerator. It could be confirmed that the cost of cool0.5
1.0
1.5
2.0
2.5
ing water affects CO2 recovery cost next after the fuel
Cost of cooling water ( /t)gas cost.
Fig. 6 Relation between CO2 recovery cost and cooling water cost(4) Effects of pipeline on CO2 recovery cost
MHI data for various areas in the Middle East
6. Conclusion
showed that the cost for CO2 pipelines ranged between
When a large amount of CO 2 is recovered from a flue
US 6 to 10 cents/MSCF/100 km.
gas source with a high concentration of CO 2 in an area
Assuming that CO2 is transported from the flue gas
where inexpensive utilities are available, the cost of such
CO 2 recovery plant to the reservoir through 100 km
CO 2 recovery is extremely competitive as a medium forCO2 pipeline, when the CO2 recovery cost is US$ 1.0/
use in EOR. In particular, the effect of the fuel gas cost
MSCF, the ratio of the CO2 pipeline cost to the cost ofon the CO 2 recovery cost is remarkably large, and theCO 2 at the destination in the field is approximately
2 recovery cost in a place with the low gas cost beCO
6to 9%. The effect of the CO2 pipeline cost on the CO2
comes very small. In addition, when the distance between
recovery cost can thus be said not to be so large.
the flue gas CO 2 recovery plant and the reservoir is ap(5) Observations
proximately 100 km, the effect of the cost of the pipelines
The economic study result shows that the calculated
used to transport CO 2 on the cost of recovering CO 2 iscost of CO 2 in the reservoir is US$ 1.0/MSCF or lessrelatively small. Accordingly, when the flue gas CO2 rewhen an excellent source of flue gas with a high CO2
covery plant is located in an area that is within several
concentration such as boiler flue gas is present at ahundred kilometers from the reservoir where inexpensive
location that is within 100 km from the reservoir, andfuel gas and a large source of flue gas with a high CO 2natural gas and cooling water are available at low cost.
concentration are available, CO 2 EOR becomes feasible
This cost value is equivalent to that of natural gas
with a high level of economic efficiency.
which competes with CO2 as a medium for EOR.
When CO 2 is recovered on a large scale from fuel gas
At present, natural gas is injected as a medium forat a rate of approximately US$1/MMBtu with the flue gas
a secondary crude oil production in many cases. HowCO 2 concentration of 8.5% by volume, which is a typicalever, sufficient consideration could also be given to thevalue for most gas-fired boilers, the CO 2 recovery costuse of CO 2 recovered flue gas, which is equivalent tofalls within a range of US$0.8 to 1.2/MSCF (US$ 15 to 23/
natural gas in terms of cost, as a replacement for natuton). This is equivalent to the average price level for CO2
ral gas.
emission trading rights in Europe that can be expected in
A number of benefits can be realized through thethe future. When an EOR project using flue gas recovuse of flue gas recovered CO 2 for EOR including theered CO2 is adapted to CDM and JI, the cost of recoveringfact that CO2 injected into the ground becomes sequesCO 2 is offset by the cost of the emission trading rights
trated in the reservoir and thus can contribute to theand, hence, the EOR project becomes more advantageous
prevention of global warming. When the EOR project
over methods in terms of potential profit margin.
using flue gas-recovered CO2 is applied to a clean deReferences
velopment mechanism (CDM) and joint implement (JI)
(1) New technology of CO2 fixation and sequestration, CMC, ltdof the Kyoto mechanism to prevent global warming,(2000)
the reduced amount of CO 2 can be internationally(2) Special Report Enhanced Oil Recovery, Oil & Gas Journal
traded as a credit of a reduced amount of greenhouse
April 15 (2002)
gas emission.
For CO2, US$1/MSCF is equivalent to US$19/ton.
Accordingly, when the trading price of the emission
right for CO 2 is equal to or greater than US$20/ton,the cost of flue gas CO 2 can be completely offset bythat price, and a CO 2 EOR project results in a large
Shojiro Iwasaki
Takashi Kamijo
Toru Takashina
Hiroshi Tanaka
profit.

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 41 No. 4 (Aug. 2004)

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