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CO2 Between Disposal and Utilization

Mahmoud Ahmed Seif, Omar Mohamed El Khatib, Islam Yakan Mourad, Mostafa Ahmed Abdelmohsen,

Mohamed Sayed El Tayb, Mohamed Sayed Abdelmonem, Mohamed Gamal Helmy, and Samar Saeed

This l iterature review was prepared for presentation at Petroleum Department, Cairo University, Faculty of

Engineering held in March 18, 2012.

Introduction

There is a broad consensus that climate change is occurring, and that it is linked to a buildup of

greenhouse gases (GHGs) in the atmosphere enhancing the natural “greenhouse effect”.

A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal

infrared range. This process is the fundamental cause of the greenhouse effect. The primary

greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous

oxide, and ozone.

Carbon dioxide CO2 is the most significant of these GHGs and its main source is the combustion

of fossil fuels. CO2 and other global warming pollutants are collecting in the atmosphere like a

thickening blanket, trapping the sun's heat and causing the planet to warm up.

Global Warming

Global warming is the unusually rapid increase in Earth’s average surface temperature over the

past century primarily due to the greenhouse gases GHG released by people burning fossil fuels.

According to NASA’s Goddard Institute for Space Studies (GISS), the average global

temperature on Earth has increased by about 0.8°Celsius (1.4°Fahrenheit) since 1880. Two-thirds

of the warming has occurred since 1975, at a rate of roughly 0.15-0.20°C per decade.

Effects of Global Warming

A one-degree global change is significant because it takes a vast amount of heat to warm all the

oceans, atmosphere, and land by that much. In the past, a one- to two-degree drop was all it took

to plunge the Earth into the Little Ice Age. A five-degree drop was enough to bury a large part of

North America under a towering mass of ice 20,000 years ago.

According to International Panel on Climate Change (IPCC), 2007:

Sea level rise became faster over the last century, and expected to rise between 7 and 23 inches.

Hurricanes and other storms are likely to become stronger.

Decline of the Adélie penguins on Antarctica, where their numbers have fallen from 32,000

breeding pairs to 11,000 in 30 years.

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Ecosystems will change—some species will move farther north or become more successful; others

won’t be able to move and could become extinct.

Global CO2 Emissions by Sector

The most two sectors which have the highest percentage of CO2 emissions are:

Industry

Especially Heavy industries (iron, steel, and cement) are responsible for 17% of global

anthropogenic CO2 emissions.

Power Generation

Power plants are responible for more than 30% of global anthropogenic CO2 emissions, with

coal-fuelled units being the most carbon-intensive.

The percentage of each sector is shown in the Figure 1.

What Is the Solution?

Using the renewable energy sources, such as wind and solar power, is one of the proposed

solutions as it gives lower CO2 emissions than fossil fuels, in reality their contribution to global

energy production over the short to medium term will remain relatively small.

There are currently only two options for meeting base-load energy demand in a reliable and a

low carbon way in the timeframe in question. One solution is nuclear power which is reliable and

has low emissions, but is slow to deploy at scale. Another is to counter the CO2 arising from fossil

fuel power stations by employing CCS (carbon dioxide capturing and storage).

CCS is one of several high impact CO2 mitigation methods that could be applied to help stabilize

allowable percentage of CO2 in the atmosphere.

What Is the CCS?

It is the process of storing carbon underground to curb the accumulation of CO2 in the

atmosphere. It involves two stages, capturing and then storage.

Figure 1. Global CO2 emissions by sector

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In this section, CO2 is captured as a first step before storing it underground (CCS) or to be used

in the industry as indicated later in this report (CO2 Utilization).

Capturing Technology

The objective of capturing CO2 is to produce a concentrated stream of CO2 which can be

transported and sequestrated underground or underwater, or can be reused in several

industrial uses so, getting benefit of reducing high CO2 emissions in these last years. There are

four processes for capturing CO2:

1. Gas Sweetening In this process, CO2 is separated from raw natural gas at a gas processing plant as shown in Figure 2.

2. Post-combustion

CO2 is separated from flue gas after combustion, and can be retrofitted to existing power and heavy industrial plants with relatively high costs and energy penalty as shown in Figure 3.

Figure 2. CO2/CH4 separation

Figure 3. Post-combustion capture

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3. Oxyfuel-combustion Fuel is combusted in pure oxygen instead of air, producing a concentrated CO2 stream

in the flue gas, which is almost ready to be transported. This is shown in Figure 4.

Figure 4. O2/N2 air separation unit

4. Pre-combustion

A hydrocarbon fuel source – coal, gas, biomass – is gasified into ‘‘shifted syngas”

(mixture of CO2 and H2), from which the CO2 is separated. In power generation, the pre-

combustion process is more energy efficient than post-combustion but requires new and

expensive plant design. (Figure 5)

Figure 5. Pre-combustion CO2 capture

Comparison Between Capture Technologies

The main difference between these different processes is shown in Table 1.

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Transportation

After capturing CO2, it must compressed to a pressure above 8 MPa in order to avoid two-phase

flow regimes and increase the density of the CO2, thereby making it easier and less costly to

transport. It could be transported in pipelines, ships, or rail tankers.

CO2 must transported in pipelines as a dry gas to prevent the corrosion of the pipelines; moisture

must be removed to avoid corrosion or construction of high cost anti-corrosive pipeline.

Road and rail tankers also are technically feasible options. These systems transport CO2 at a

temperature of -200C and at 2 MPa pressure. However, they are uneconomical compared to

pipelines and ships, except on a very small scale, and are unlikely to be relevant to large-scale

CCS.

Transportation cost depends strongly on; the travelled distance, transported quantity, type of

transportation, and barriers that face the transportation.

What to Do with the Captured CO2?

Hence CO2 is captured; there are two possible ways to deal with it. The first one is sequestration

and the second one is utilization. Sequestration is storing large volumes of CO2 underground for

long periods of time, while utilization is introducing CO2 for several uses in the industry. Both of

them are very important. Some are applied on commercial scale and others are not applicable

Table 1 – Comparison between capture technologies

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till now. The applicability problems may arise from being not commercial or due to some other

technical problems. We covered some topics under those two main titles to clarify their concepts

and disadvantages.

CO2 Sequestration

The captured CO2 is injected down the earth into one of the options indicated in Figure 6.

Figure 6. Geological storage options

Storing CO2 in depleted oil and gas reservoirs is preferable due to the wealth of knowledge

and experience the petroleum industry has in these reservoirs. Saline formations can store

around 10000 Giga ton of CO2, while depleted oil and gas reservoirs have the potential to

store around 900 Giga ton. Geoscientists claim that the structures of HC reservoirs can store

large quantities of CO2 for thousands – if not millions- of years.

› Mechanism of Sequestration

Before injection, CO2 is compressed at surface and then injected through a well into the

appropriate zone of the formation, lying at 800 – 3000 meters below the surface. CO2 Volume decreases as the depth of the well increases. For example, if the injected

volume was 1000 m3, the volume at 800 m will be around 2.7m3.

At 800 meter or at greater depths, CO2 exists as a supercritical fluid which has a density

of a liquid and a viscosity of a gas.

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After entering the formation, CO2 migrates upward due to its buoyancy relative to oil and

water. This migration continues until it’s trapped at the cap rock.

Afterwards, CO2 is trapped efficiently due to the following trapping mechanisms:

1. Residual Trapping

When free-phase CO2 migrates, it forms a plume. At the tail of this plume, the

concentration of the CO2 falls below a certain level. It becomes trapped by capillary

pressure from the water in the pore spaces between the rock and stops flowing. Over

time, this residually trapped CO2 can dissolve into the formation water. This is shown in

Figure 7.

Figure 7. CO2 residual trapping

2. Solubility Trapping The solubility of CO2 in water increases with increasing pressure and decreases with

increasing temperature and increasing water salinity. As some CO2 dissolves in water, the

water becomes denser, and begins to sink downwards.

3. Mineral Trapping When CO2 dissolves in water it creates carbonic acid which can then react with the basic

components of the reservoir rock matrix, precipitating out as various carbonate minerals.

The longer CO2 stays in the reservoir, the more securely trapped it becomes.

CO2 Utilization

The previous section clarified the first possible way to deal with the captured CO2; that

considered it a waste; therefore, it must be stored underground. This section will discuss the

second way that is CO2 reuse or CO2 utilization.

A. CO2 Uses in Petroleum Industry

1. CO2 –EOR The use of CO2 to increase the recovery of oil has received considerable attention since

1950. Laboratory research has been conducted and field applications have been initiated

and performed indicating a great interest in CO2 flooding.

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› Factors That Make CO2 an EOR Agent

Mixing with trapped oil

Swelling of crude oil

Reducing crude oil viscosity

Reducing oil density

As a result of CO2 dissolved in the crude, the oil’s volume will increase from 10 to 20

percent or more, then its viscosity will decrease and its mobility will increase therefore it

will displace toward the producing well.

› CO2 Flooding in Egypt

Depending on a screen study held on some reservoirs in the Western, Eastern desert and

Gulf of Suez, it is found that CO2 injection is one of the most appropriate EOR method can

be applied in Egypt as shown in table 2, but there are some serious limitations such as the

availability of CO2 sources in Egypt in addition to transportation problems.

Table 2 – Summary of Egypt oil field data and screening criteria results

2. Drilling Fluid

Drilling with CO2 is a promising technology, though it face fatal circumstances that needs

effective solutions. First, CO2 is compressed using a compressor at surface to convert it

into a liquid. Then, the liquid CO2 is pumped through the coiled tubing using a high-

pressure pump to a pressure level above its critical pressure (1074 psia). As it enters the

tubing, it heats up and becomes supercritical. It then powers the down-hole motor that

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turns the bit. As the supercritical CO2 exits the high-pressure jet nozzles attached to the

drill-bit, the large pressure drop is expected to flash it to a gas phase in the annulus,

maintaining a low bottom-hole pressure and low annular pressure gradient.

› Advantages of the CO2 System

1. High density of liquid-supercritical CO2 (SCCO2) in the tubing allows the down-hole

motor to generate necessary torque for satisfactory drilling in the example case study.

Also, the jetting action is expected to complement the bit performance and enhance

the drilling rates. In addition to lubricating and cooling the bit, it provides pre-cleaning

of the tool path and propagation of the cracks induced by the bit. Experiments

reported by Kolle show that SCCO2 cuts even hard shale much deeper and wider than

water jets at less than half the pressure.

2. Gaseous phase CO2 in the annulus leads to lower pressure values in the annulus which

is very important for an underbalanced drilling operation. The results also indicate that

efficient hole-cleaning is achieved in the system.

3. The critical temperature (88 deg. F) and critical pressure of CO2 (1074 psi) are favorable

from the point of view of energy requirements.

4. CO2 is a non-damaging fluid for the formation and does not adversely affect the

formation permeability. In fact, it is often used as a fracturing fluid because it improves

the fluid conductivity near the wellbore.

› Problems Associated with the CO2 System

1. Corrosion is a very significant problem with CO2 in the presence of water. If formation

water mixes with CO2 in the annulus, the corrosion rates can be significant. This is a

major concern and has been addressed later in the paper.

2. Cuttings carrying capacity could be questionable due to the low viscosity of CO2.

However, the results show that as long as turbulent flow conditions are maintained in

the annulus and the cuttings size is less than 0.05”, CTRs are favorable. For other

situations, there may be a need to increase the viscosity using CO2

thickeners/viscosifiers.

3. The Joule Thompson effect, though not significant for the case study, needs to be

considered for any possibility of a large temperature drop across the nozzles and the

choke.

4. The CO2 drilling system requires a specially designed high pressure motor with sealing

elements compatible with supercritical CO2, as it is known to cause swelling of the

elastomers. Drilling turbines may offer an attractive alternative to mud-motors.

5. The system requires high-pressure equipment, including a high pressure pump to

inject liquid CO2, high pressure coiled tubing and specially designed jetting bits that

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work on the principle of critical flow. The working pressure rating of coiled tubing is

constrained by its fatigue limits.

6. CO2 is a green-house gas and therefore there are environmental issues associated with

its discharge to the atmosphere. CO2 needs to be re-compressed, on returning to the

surface, and stored for further use as a drilling fluid or for enhanced recovery projects.

7. Corrosion affects the economics of the process and hence it is essential to include the

necessary steps in the plan before the initiation of the project. Detection and

monitoring of corrosion rates is essential. The greater the data one collects on the

well, the better are the chances of accurately predicting and reducing the risks of

corrosion. Test coupons, caliper survey, sonic-thickness logs and probes are some of

the options that do not require pulling the tubing for inspection.

B. CO2 Uses in Other Industries

1. Gasoline

Gasoline is a hydrocarbon consisting of carbon and hydrogen in various proportions.

Gasoline or petrol is a petroleum derived liquid used in internal combustion engine as fuel

obtained by the fractional distillation of petroleum.

CH4+CO2 (C5-10 Hn) +H2O

To produce gasoline from CO2, the above reaction has to be reversed. The CO2 has to be

split to obtain carbon which on reacting with hydrogen (obtained from water) produces

a hydrocarbon mixture methanol, which on further refining produces gasoline or jet fuel.

The above reaction need excess amount of energy which makes the process inefficient

and economically unfeasible.

The enzymes and catalysts that are used in the splitting reaction of CO2 are expensive

and hence add up to the cost making it economically unfeasible. A company has been

successful in inventing a polymer shell that protects these expensive enzymes and

catalysts that can be recycled many times. The same technology can be used to extract

hydrogen from water, avoiding the need for energy-intensive hydrolysis.

Gasoline, it turns out, is an almost ideal fuel (except that it produces 19.4 pounds of

carbon dioxide per gallon). It is easily transported, and it generates more energy per

volume than most alternatives. If it can be made out of carbon dioxide in the air, the Los

Alamos concept may mean there is little reason to switch, after all. The concept can also

be adapted for jet fuel; for jetliners, neither hydrogen nor batteries seem plausible

alternatives.

2. Methanol After adjusting the CO/H2 ratio close to 1:2, the syngas is converted to methanol in the

Presence of copper/zinc oxide based as a catalyst.

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CO2 +H2 CH3OH

› Uses of Methanol

Methanol has long been used in consumer products as windshield washer fluids,

deicing fluids, antifreezes, and fuels for camping and outdoor activities .

Methanol has excellent combustion characteristics making it a suitable and

proven fuel for internal combustion engine (ICE) driven vehicles.

Methanol can be used as an excellent and non–expensive fuel in the engines.

Although its demand increases recently, but one of the most parameters that affect its

cost is the transportation

3. Methane Hydrogen is a suitable substance for reaction with carbon dioxide. According to the

Sabatier's reaction, one mole of methane can be obtained by the reaction of one mole of

carbon dioxide and four moles of hydrogen.

CO2 + 4 H2 CH4 + 2 H2O

› Global CO2 Recycling

Electricity is generated from solar cells on deserts, at desert coasts the electricity is used

for hydrogen production by sea water electrolysis which consists of anodes and cathodes,

CO2 react with hydrogen to produce methane, then methane can be stored or used as

fuel. CO2 recycling will be one of the most useful methods to prevent global warming and

supply abundantly renewable energy. Solar cells is available on deserts in Egypt is more than three times higher than that is

Japan; where this technology is applied; due to long sunlight time.

Conclusions

As noticed in this literature review, it became evident that dealing with CO2 is having an

increasing importance. Either to dispose CO2 or to utilize it is imposing itself on the future

generations living on the Earth. This report has displayed a general overview about how to

dispose CO2 by sequestering it beneath the earth’s crust. In addition, several uses that are still

under research have been clarified including several uses of CO2 in EOR, Drilling fluids, and

methanol, gasoline and methane industries. The purpose of that is to make the best of CO2

instead of making it a waste. However, these uses are still not economical but they are technically

viable. One day, they will reach the commercial limit. That’s why one must keep these uses in

mind and under continuous research to leave a legacy in the life of the Earth.

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Abbreviations

GHG Green House Gases

GISS Goddard Institute for Space Studies

IPCC International Panel on Climate Change

CCS Carbon dioxide Capture and Storage

SPC Supercritical Pulverized Coal

NGCC Natural Gas Combined-Cycle

CO2 – EOR Enhanced Oil Recovery using carbon dioxide (“CO2 flooding”)

ICE Internal Combustion Engine

SCCO2 Supercritical CO2

List of Figures

Figure 1 Global CO2 emissions by sector Page # 2

Figure 2 CO2/CH4 separation Page # 3

Figure 3 Post-combustion capture Page # 3

Figure 4 O2/N2 air separation unit Page # 4

Figure 5 Pre-combustion CO2 capture Page # 4

Figure 6 Geological Storage Options Page # 6

Figure 7 CO2 residual trapping Page # 7

List of Tables

Table 1 Comparison between capture technologies Page # 5

Table 2 Summary of Egypt oil field data and screening

criteria results Page # 8

Units of Measurement

Km Kilometer

MPa Mega Pascal

GJ/tCO2 Giga Joule per ton of CO2 0C Degree Celsius

References

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