Order Code RL34218
Underground Carbon Dioxide Storage:
Frequently Asked Questions
October 24, 2007
Peter Folger
Specialist in Energy and Natural Resources Policy
Research, Science, and Industry

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Underground Carbon Dioxide Storage:
Frequently Asked Questions
Summary
This report answers frequently asked questions about the geologic storage of
carbon dioxide (CO ). The questions are broadly representative of typical inquiries
2
regarding the process and mechanics of storing CO underground, how much might
2
be stored, and what might happen to CO once it is injected underground. Geologic
2
storage is one step in a process termed carbon capture and storage, or CCS.
Following capture and transportation, CO would be injected into geologic
2
formations that have suitable volume, or pore space, to retain large quantities of the
captured gas. Currently, the most promising reservoirs for storing CO are oil and
2
gas fields, deep saline reservoirs, and unmineable coal seams. Preventing CO from
2
escaping would require careful reservoir characterization. Knowledge gained from
over 30 years of injecting CO underground to enhance oil recovery would be applied
2
to storing CO for CCS purposes. Given the complexity of most geologic reservoirs,
2
and the potentially huge volumes of CO that may be injected, risk of some CO
2
2
leakage over time may never completely be eliminated. A variety of techniques are
available for monitoring leaks from a reservoir; however, the long-term (hundreds
to thousands of years) fate of CO stored underground is not thoroughly understood.
2

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Contents
Carbon Capture and Storage — Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
What is Carbon Capture and Storage (CCS)? . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Why is CCS of Interest in the Debate Over Global Warming? . . . . . . . . . . . . . . 1
Storing CO Underground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2
What is a Geologic Formation and How Would it Store CO ? . . . . . . . . . . . . . . 2
2
Where Would Large Amounts of CO Likely be Stored? . . . . . . . . . . . . . . . . . . 3
2
How Much CO Can Be Stored Underground? . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2
Can the Storage Capacity Estimates for CO be Confirmed? . . . . . . . . . . . . . . . 4
2
How is CO Injected Underground and How Deep Will it be Stored? . . . . . . . . 5
2
Is CO Currently Stored Underground? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2
What Could Go Wrong With Storing CO Underground? . . . . . . . . . . . . . . . . . . . . . 6
2
Can CO Leak From Geologic Formations? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2
Can CO Harm People? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2
What is at Risk if CO Leaks? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2
How Would Leaks be Detected? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
How Long Will CO Stay Underground? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2
What is the Status of Demonstration Projects for Underground CO Storage? . . 9
2
List of Tables
Table 1. Geological Storage Capacity for the United States and Parts of Canada . . . 4

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Underground Carbon Dioxide Storage:
Frequently Asked Questions
Many people are unfamiliar with the concept of storing carbon — most likely in the
form of carbon dioxide (CO ) — underground in geologic reservoirs. This report answers
2
questions broadly representative of typical queries about why, where, and how CO may
2
be stored underground, as well as how much CO might be stored. In addition, this report
2
answers several questions about what might happen if CO escapes from underground
2
storage. The term carbon sequestration includes carbon capture and storage (CCS), but
it is also used to refer to the biological uptake of carbon from the atmosphere through
photosynthesis. This report does not discuss biological sequestration. Storing CO in the
2
oceans is another possible option for carbon storage, although currently not deemed as
promising as underground storage.1
Carbon Capture and Storage — Background
What is Carbon Capture and Storage (CCS)?
Carbon capture and storage (CCS) is capturing carbon — usually carbon dioxide
(CO ) — at its source and storing it instead of releasing it to the atmosphere. The first
2
step in CCS is to capture CO at the source and produce a concentrated stream for
2
transport and storage. Currently, three main approaches are available to capture CO2
from large-scale industrial facilities, such as cement plants, or fossil fuel power plants:
(1) post-combustion capture, (2) pre-combustion capture, and (3) oxy-fuel combustion
capture. Transportation of captured CO is the second step in CCS. Pipelines are
2
currently the most common method for transporting CO in the United States, and would
2
likely be used for CCS unless the CO could be stored directly beneath the emission
2
source. Injecting CO underground into a geologic formation is the likely third step in the
2
process, where the carbon would remain out of contact with the atmosphere.
Why is CCS of Interest in the Debate Over Global Warming?
CCS is attracting interest as a measure for mitigating global climate change because
large amounts of CO emitted from fossil fuel use could potentially be captured and stored
2
underground. Most scientists have concluded that greenhouse gases (GHG) emitted by
humans are influencing the global climate. Although natural events such as volcanic
eruptions or variability in the sun’s energy output also contribute to climate variability,
scientists cannot explain the climate changes in the past few decades without including
1 This report only discusses underground storage of carbon. For more information , see
CRS Report RL33801, Direct Carbon Sequestration: Capturing and Storing CO , by Peter
2
Folger; and CRS Report RL33971, Carbon Dioxide (CO ) Pipelines for Carbon
2
Sequestration: Emerging Policy Issues, by Paul W. Parfomak and Peter Folger.

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the effects of elevated GHG concentrations from fossil fuel use, land clearing, and
industrial and agricultural emissions.2 Of all the GHGs emitted by humans, CO is
2
considered most important, in part because large volumes of the gas are released to the
atmosphere each year. A large fraction of CO emitted by human activities remains in the
2
atmosphere; in fact, CO concentrations in the atmosphere have increased by one-third
2
since the Industrial Revolution, from about 280 parts per million (ppm) in 1850 to over
380 ppm today.3 In the United States, fossil fuel combustion accounts for 94% of all CO2
emissions. One-third of U.S. CO emissions come from fossil-fueled electricity
2
generating power plants. These plants may be the most likely initial candidates for CCS
because they are predominantly large, single-point sources of emissions. An assumption
inherent in CCS is that CO will be stored underground in sufficient quantity, and for
2
sufficient time to significantly ameliorate impacts of GHG-influenced climate change.
Storing CO Underground
2
What is a Geologic Formation and How Would it Store CO ?
2
CO would need to be stored underground in geologic formations4 with
2
characteristics that would trap large volumes of CO and not allow significant leakage
2
from the formation. Some of these characteristics include open spaces, known as
porosity; sufficient interconnectivity between the open spaces so that CO can flow
2
laterally or migrate within the formation, known as permeability; and a layer or boundary
that is impermeable to upward flow so that CO is trapped underground. Many types of
2
geologic formations have these features, such as sandstones and limestones, and some
geologic formations are tens to hundreds of feet thick and may extend laterally for miles.
Geologic formations that are potential CO reservoirs may be analogous to reservoirs that
2
trap oil and gas. Oil and gas can be found in sandstones, limestones, and other permeable
formations, trapped for millions of years until tapped by wells drilled from the surface to
extract the hydrocarbons. An overlying layer of low permeability, commonly referred to
as a caprock or geologic seal (such as shales or siltstones), prevents oil and gas, and
would prevent CO , from migrating out of the permeable formation.
2
Other types of geologic formations may possess characteristics that could trap CO2
underground. For example, coal beds are commonly porous and permeable and are
viewed as potential reservoirs for storing CO . In addition, methane gas — which forms
2
naturally from the coal — often remains bound to the organic molecules within the coal
seam. Experiments have shown that coal also can bind CO to its mineral surfaces, and
2
the organic molecules may actually prefer to trap CO instead of the naturally occurring
2
methane. Other types of geologic formations, known as black shales, also possess this
2 For more information on the science of climate change, see CRS Report RL33849, Climate
Change: Science and Policy Implications, by Jane A. Leggett.
3 For more information on why CO concentrations are increasing in the atmosphere, see
2
CRS Report RL34059, The Carbon Cycle: Implications for Climate Change and Congress,
by Peter Folger.
4 A geologic formation refers to a body of rock, igneous, metamorphic, or sedimentary that
can be identified by its geologic characteristics (e.g., types of minerals, age, chemical
composition) and can be mapped at the Earth’s surface or traceable in the subsurface.

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CRS-3
binding ability, and may be potential reservoirs for CO storage. Shales typically have
2
low permeability, however, which may make it difficult to inject large volumes of CO2
at rates comparable to other types of geologic formations.
Another type of geologic formation that may be a candidate for CO storage is known
2
as flood basalt,5 such as that found on the Columbia River Plateau. Large and thick
formations of flood basalts occur globally, and may have favorable characteristics for CO2
storage, such as high porosity and permeability. Of further interest is the capacity for the
minerals in these flood basalts to chemically react with CO , which could result in a large-
2
scale conversion of the gas into stable, solid minerals that would remain underground for
thousands of years.
Where Would Large Amounts of CO Likely be Stored?
2
It is generally agreed that the most promising underground locations for storing CO2
underground fall into three categories: (1) oil and gas reservoirs; (2) deep saline
reservoirs6; and (3) unmineable coal seams. Oil and gas reservoirs and deep saline
reservoirs are comprised of porous and permeable geologic formations, as discussed
above, whose pore space is filled either with hydrocarbons, saline water (brine), or some
combination of both. Coal that are not economically mineable because the beds are not
thick enough, the beds are too deep, or the structural integrity of the coal bed7 is
inadequate for mining may have the properties discussed above, making them amenable
to CO storage.
2
According to a DOE report,8 at least one of each of these three types of potential CO2
reservoirs occur across most of the United States in relative proximity to many large point
sources of CO , such as fossil fuel power plants or cement plants. Deep saline formations
2
are the most widespread, and have the most potential storage capacity compared to oil and
gas reservoirs or unmineable coal seams. Oil and gas fields or unmineable coal seams,
however, could produce incremental amounts of crude oil or methane with CO injection,
2
which could offset some of the costs of storing CO . These techniques are referred to as
2
enhanced oil recovery (EOR) and enhanced coal bed methane recovery (ECBM). Some
parts of the country, such as New England and portions of the mid-Atlantic seaboard, are
5 Flood basalts are vast expanses of solidified lava, commonly containing olivine, that
erupted over large regions in several locations around the globe. In addition to the Columbia
River Plateau flood basalts, other well-known flood basalts include the Deccan Traps in
India and the Siberian Traps in Russia.
6 Sometimes the term saline aquifer is used in this context, which is probably a misnomer,
because the saline formations being discussed for CO storage are typically too saline for
2
drinking or agricultural use. Shallow aquifers that are brackish might be used as drinking
water or agricultural resources with some treatment, such as desalinization, but such aquifers
probably would not be considered as prime targets for storing CO .
2
7 Coal bed and coal seam are interchangeable terms.
8 U.S. Dept. of Energy, National Energy Technology Laboratory, Carbon Sequestration
Atlas of the United States and Canada (March, 2007), 86 pages. Hereafter referred to as the
Carbon Sequestration Atlas.
See [http://www.netl.doe.gov/publications/carbon_seq/atlas/index.html].

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CRS-4
not close to identified CO reservoirs; captured CO from those regions may have be
2
2
transported over long distances to reach a suitable storage site.
How Much CO Can Be Stored Underground?
2
Table 1 shows estimates for CO storage capacity in the United States and parts of
2
Canada for the three reservoir types discussed above, according to the DOE Carbon
Sequestration Atlas.
Table 1. Geological Storage Capacity for the United States and
Parts of Canada
Lower estimate
Upper estimate of
of storage
storage capacity
Reservoir type
capacity (GtCO )
(GtCO )
2
2
Oil and gas fieldsa
82.4
—
Deep saline
919.0
3,378.0
formations
Unmineable coal
156.1
183.5
seams
aAccording to DOE, oil and gas fields are sufficiently well-understood so that no range of values
for storage capacity is given.
Note: GtCO equals a billion metric tons of CO . A metric ton is approximately 2,200 pounds.
2
2
Even the lower estimates of storage capacity, when added together, indicate that the
United States has enough capacity to store its total CO emissions from fossil fuels for
2
over 200 years (at the current rate of emissions).9 Excluding CO emissions from fossil
2
fuels used for transportation, which would likely not be captured and stored underground,
these estimates suggest the United States could store over 300 years of CO emitted from
2
sources like power plants, factories, and cement manufacturers. Whether CO can be
2
economically captured, transported, and stored underground remains an open question.
Can the Storage Capacity Estimates for CO be Confirmed?
2
The storage estimates are primarily drawn from existing information on the geology
of the formations and various assumptions about the geologic storage mechanisms. Key
considerations in the estimates include (1) how much total storage space is available for
each type of reservoir, and (2) what is the efficiency of storing CO in the available
2
storage space (i.e., what fraction of the total pore space could actually be occupied by
CO ). How the estimates for the reservoirs will compare to their actual storage capacities
2
will depend, in part, on a series of planned experiments: large-volume injection tests
whereby CO is injected into a formation and its behavior monitored (discussed below).
2
9 In 2005, the United States emitted approximately 5.6 GtCO from the combustion of fossil
2
fuels. See [http://epa.gov/climatechange/emissions/usinventoryreport.html].

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CRS-5
The experiments should produce results that will enable researchers to test their
assumptions about the storage properties of the geologic formations.10
How is CO Injected Underground and How Deep Will it be
2
Stored?
In a CCS operation, after CO is captured from its source, it would be compressed,
2
transported, and injected via wells drilled from the ground surface down to the storage
reservoir and dispersed into the geologic formation. Compressing CO is important
2
because it becomes denser and occupies less space with increasing pressure. The denser
it becomes, the more CO can be stored within the pore space of a geologic reservoir.
2
Also, with enough pressure and at a high enough temperature, CO becomes supercritical,
2
and is dense like a liquid, but flows like a gas. The ability of CO to disperse efficiently
2
through the interconnected pore spaces of a geologic reservoir increases significantly if
it is under enough pressure to be a supercritical fluid.
The density of CO increases still further if injected deeper. The denser it becomes,
2
the more likely the CO may stay underground. Conversely, if CO is injected at shallow
2
2
depths, it may be more likely to escape the reservoir. Above a depth of 2,500 feet, the
chances increase that CO would tend to rise towards the surface as a buoyant gas. Thus,
2
it is likely that oil and gas reservoirs and saline formations located deeper than 2,500 feet
would be preferred over shallower geologic formations. It is also recognized that
injecting CO deeper increases the distance between the storage reservoir and fresh water
2
aquifers — used for drinking water or agricultural purposes — that are usually located at
shallower depths.
Is CO Currently Stored Underground?
2
The petroleum industry in the United States injects approximately 32 million metric
tons of CO underground each year to help recover oil and gas resources (enhanced oil
2
recovery, or EOR).11 Injected CO expands and helps drive oil that is not recovered by
2
primary or secondary recovery towards a production well.12 Also, the CO can dissolve
2
in the oil, making it less viscous and able to flow more easily in the geologic formation.
Some of the CO is trapped in the reservoir during EOR; however, a large fraction of the
2
injected gas may return to the surface with the recovered oil, where it is usually recovered
and reinjected. Only small amounts of CO produced by human activities are injected
2
underground in EOR operations. Approximately 90% of the CO injected for EOR in the
2
United States comes from naturally occurring underground deposits; only about 3 million
10 See the DOE National Energy Technology Laboratory FAQ Information Portal at
[http://www.netl.doe.gov/technologies/carbon_seq/FAQs/project-status.html#Geologic_
Field].
11 See [http://www.fossil.energy.gov/programs/sequestration/geologic/index.html].
12 Primary recovery relies on the natural pressure of the reservoir to drive the oil or gas to
the production well; secondary recovery uses water or gas to produce more petroleum. EOR
is known as a tertiary recovery technique.
See [http://www.fossil.energy.gov/programs/oilgas/eor/index.html].

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CRS-6
metric tons of CO comes from man-made sources like fertilizer or gas-processing
2
plants.13
The United States leads the world in EOR activities and the petroleum industry has
over 30 years of EOR experience. Engineering techniques and knowledge acquired since
the early 1970s may be directly applicable to CCS. In fact, the amount of CO produced
2
from a typical 500 megawatt coal-fired power plant — about 10,000 metric tons per day
— is comparable to the daily injection rates for some EOR operations.14 However,
because the purpose of EOR is to extract oil and gas not normally recoverable, the net
sequestration of CO in EOR operations may be negligible, because the extracted oil and
2
gas is burned for energy which releases CO to the atmosphere. Moreover, even if all of
2
the CO used in U.S. EOR operations today remained trapped underground, it would
2
represent a small fraction of the current U.S. emissions: fossil fuel power plants alone
emit to the atmosphere more than 70 times the EOR amount of CO each year.
2
The only major commercial project dedicated to CO storage in a geologic reservoir
2
today is the Sleipner Project, located approximately 150 miles off the coast of Norway in
the North Sea. Over 2,700 metric tons of CO per day — separated from natural gas at
2
the Sleipner West Gas Field — is injected 2,600 feet below the seabed. Over the lifetime
of the project, over 20 million metric tons of CO are expected to be injected into the
2
saline formation, which is sealed at the top by an extensive and thick shale layer.15
Monitoring surveys of the injected CO indicate that the gas has spread out over nearly
2
two square miles underground without leaking upwards. Long-term simulations also
suggest that over hundreds to thousands of years the CO will eventually dissolve in the
2
saline water, becoming heavier and less likely to migrate away from the reservoir.
What Could Go Wrong With Storing CO2
Underground?
Can CO Leak From Geologic Formations?
2
It is expected that the reservoir characterization process would rule out geologic
formations that are too shallow, do not have adequate caprocks or other geologic seals,
are intersected by permeable faults or fractures that might be pathways for escaping CO ,
2
or are in tectonically active areas. Abandoned oil and gas fields are often considered first
targets for CO storage to take advantage of the natural configuration of permeable
2
reservoir and overlying caprocks. Oil and gas reservoirs trapped hydrocarbons for
millions of years before wells drilled into the reservoir produced the petroleum. Large-
scale injection tests planned for the next several years should also provide information
that would be used to guide site selection for full-scale CCS operations in the future,
especially for deep saline reservoirs and unmineable coal seams which do not have the
13 Intergovernmental Panel on Climate Change (IPCC) Special Report: Carbon Dioxide
Capture and Storage, 2005, p. 204. Hereafter referred to as IPCC Special Report.
14 IPCC Special Report, p. 233.
15 IPCC Special Report, Box 5.1.

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CRS-7
same level of engineering experience as oil and gas fields.16 All of these considerations,
however, do not rule out the chance that CO could leak from geologic formations. How
2
much could leak, over what duration, and what the effects might be are key questions.
Can CO Harm People?
2
A likely public concern would be the potential for large volumes of CO to leak to
2
the ground surface and accumulate in low-lying, inhabited areas. CO is not toxic,
2
flammable, or explosive (like methane or propane gas, for example), but if allowed to
accumulate in enclosed spaces at high concentrations (e.g., 40,000 ppm or more), CO2
could displace oxygen and cause unconsciousness or asphyxiation.17 If CO leaks into the
2
soil and root zone at high enough concentrations, it may also harm vegetation. The
chances of such high concentrations forming during CO injection for CCS are likely
2
remote, assuming the reservoir is well characterized, and “fast pathways” such as
unidentified and abandoned wells, or unidentified permeable fractures and faults do not
intersect the injection site and connect to occupied, low-lying, unventilated structures.
The chances are probably higher for small amounts of leakage during injection, or leakage
over time, given the complexity of most geologic formations, although it is also likely that
some reservoirs may never leak CO .
2
What is at Risk if CO Leaks?
2
In addition to the remote chance for affecting human health directly, discussed
above, another likely possible risk is the chance of CO leakage into an aquifer used for
2
drinking water or as a supply for agriculture. If that occurs, contaminants that may be
contained in the injected CO could pollute the drinking water supply. It is unlikely CO
2
2
would be injected close to a critical aquifer; it would likely be injected deep enough so
that the possibilities of upward leakage are fairly remote. The same precautions would
apply: adequate caprock, deep reservoir, lack of “fast pathways” to the aquifer, as well as
engineering expertise to inject the CO without “overpressuring” the reservoir, which
2
could create fractures or increase the chances of leakage around wells. Over the lifetime
of an injection project, the chances of the injected CO encountering unidentified faults
2
or fractures in the reservoir may increase, as the CO disperses laterally from the injection
2
point and fills pore spaces throughout the geologic formation. However, the pressure of
the injected CO also decreases laterally from the injection point, so that the likelihood
2
of large releases over a short timespan also decreases with distance from where the CO2
is injected.
Injecting CO into saline formations lowers the pH (increases the acidity) of the
2
formation water. More acidic waters may dissolve minerals in the formation such as
calcium carbonate and release metals, such as iron and manganese, or other elements
contained within those minerals. The increased acidity could also increase the
permeability of the formation, allowing the injected CO to migrate more readily. Initial
2
16 See [http://www.netl.doe.gov/index.html].
17 40,000 ppm is the value listed as immediately dangerous to life and health (IDLH) by the
National Institute for Occupational Safety and Health. See
[http://www.cdc.gov/niosh/idlh/intridl4.html].

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CRS-8
results from injection experiments18 that observed this process seem to indicate that the
reservoir integrity remained intact and CO did not leak. Additional injection experiments
2
may help understand whether increased acidity following CO injection is a significant
2
issue.
How Would Leaks be Detected?
Geophysical techniques, such as seismic imaging, have been used at the Sleipner
sequestration project, discussed above, to map the shape of the CO plume at depth and
2
plot its migration over time as CO is injected. These techniques could be useful for
2
detecting leakage from the reservoir, especially if the CO concentrations were high
2
enough to distinguish them from the saline formation water. To help detect leaks around
wells, or into nearby structures or dwellings, tracer compounds — which are detectable
at very low concentrations — could be added to the injected CO and then monitored.19
2
If shallow aquifers are a concern, monitoring wells can be installed above the CO storage
2
reservoir, and below the drinking water aquifer, to measure changes in pressure and
chemistry that may indicate CO is escaping the reservoir. Also, changes to vegetation
2
at the ground surface could be monitored over time, which may indicate CO leakage into
2
the soil from below.
How Long Will CO Stay Underground?
2
When CO is injected into an oil and gas reservoir or a deep saline formation, it is
2
expected to occupy some portion of the pore space, and displace the saline water, oil, gas,
or some combination of the natural formation fluids. Initially, the injected CO would
2
occupy the pore space as a liquid or supercritical fluid, as discussed above, and remain
in the geologic formation unless one or more of the possible leakage scenarios outlined
above occurs. This is commonly referred to as volumetric storage.
Over hundreds or thousands of years, however, the injected CO would start to
2
dissolve into the formation fluids, further decreasing its chances of leaking out of the
reservoir. This is known as solution storage. Solution storage would effectively trap the
CO underground for a long time, but the rate at which CO dissolves into the saline water
2
2
decreases as the salinity increases; CO would dissolve only very slowly in deep, highly
2
saline formations.
CO injected into coal seams could be tightly bound, or adsorbed, onto the coal
2
surfaces, and would likely stay bound to the coal for a long time unless further disturbed.
Studies indicate that CO could displace methane (and the methane recovered at the
2
surface) which occurs naturally in many coal seams. Other studies indicate that injecting
CO into coal seams may cause the coal to swell, however, which could reduce the
2
18 Y. K. Kharaka, et al., “Gas-water interactions in the Frio Formation following CO2
injection: implications for the storage of greenhouse gases in sedimentary basins,” Geology,
v. 34, no. 7 (July, 2006), pp. 577-580.
19 Similarly, chemicals added to propane or natural gas are “tracers” detectable by smell that
could indicate leaks.

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CRS-9
permeability of the coal seam and limit its effectiveness for sequestering large amounts
of CO .20
2
Injecting CO into deep flood basalts, such as those found in the Columbia River
2
Plateau occupying portions of Washington, Oregon, and Idaho, may cause the minerals
in the basalt to react with the CO and form solid minerals (known as mineral storage).
2
The minerals would likely stay underground in the flood basalts for thousands to millions
of years, essentially trapping the injected CO for geologic time. Flood basalts are
2
attracting attention for CO storage in part because of their potential for mineral storage,
2
and because basalts commonly possess good porosity and permeability. However, unlike
oil and gas reservoirs and deep saline formations which form in sedimentary basins and
are often overlain by impermeable cap rocks, flood basalts are comprised of multiple
layers of erupted lava flows. Lava flows may not provide the same degree of geologic
seal as sedimentary rocks, like shales. Of possible concern is whether the injected CO2
will have sufficient time to react with the basalts and form stable minerals before the CO2
migrates to the surface.
What is the Status of Demonstration Projects for Underground
CO Storage?
2
Beginning in 2003, DOE created seven regional carbon sequestration partnerships
to identify opportunities for carbon sequestration field tests in the United States and
Canada.21 The regional partnerships program is being implemented in a three-phase
overlapping approach: (1) characterization phase (from FY2003 to FY2005); (2)
validation phase (from FY2005 to FY2009); and (3) deployment phase (from FY2008 to
FY2017).22 According to Carbon Sequestration Atlas, the first phase of the partnership
program identified the potential for sequestering over 1,000 GtCO across the United
2
States and parts of Canada.
20 Cui, X., R. M. Bustin, and L. Chikatamarla, “Adsorption-induced coal swelling and stress:
Implications for methane production and acid gas sequestration into coal seams,” Journal
of Geophysical Research, vol. 112, B10202 (2007).
21 The seven partnerships are Midwest Regional Carbon Sequestration Partnership; Midwest
(Illinois Basin) Geologic Sequestration Consortium; Southeast Regional Carbon
Sequestration Partnership; Southwest Regional Carbon Sequestration Partnership; West
Coast Regional Carbon Sequestration Partnership; Big Sky Regional Carbon Sequestration
Partnership; and Plains CO Reduction Partnership; see [http://www.fossil.energy.gov/
2
programs/sequestration/partnerships/index.html].
22 DOE Carbon Sequestration Technology Roadmap and Program Plan 2007, p. 36.

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CRS-10
The third phase, deployment, is intended to demonstrate large-volume, prolonged
injection and CO storage in a wide variety of geologic formations. According to DOE,
2
this phase is supposed to address the practical aspects of large-scale operations,
presumably producing the results necessary for commercial CCS activities to move
forward. On October 9, 2007, DOE announced that it awarded the first three large-scale
carbon sequestration projects in the United States.23 According to DOE, each of the three
projects plans to inject a million tons of CO or more into deep saline reservoirs.
2
23 See
[http://www.netl.doe.gov/publications/press/2007/07072-DOE_Awards_Sequestration_P
rojects.html].

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