Order Code RS22990
November 26, 2008
Gas Hydrates: Resource and Hazard
Peter Folger
Specialist in Energy and Natural Resources Policy
Resources, Science, and Industry Division
Summary
Solid gas hydrates are a potentially huge resource of natural gas for the United
States. The U.S. Geological Survey estimated that there are about 85 trillion cubic feet
(TCF) of technically recoverable gas hydrates in northern Alaska. The Minerals
Management Service estimated a mean value of 21,000 TCF of in-place gas hydrates
in the Gulf of Mexico. By comparison, total U.S. natural gas consumption is about 23
TCF annually. The in-place estimate disregards technical or economical recoverability,
and likely overestimates the amount of commercially viable gas hydrates. Even if a
fraction of the U.S. gas hydrates can be economically produced, however, it could add
substantially to the 1,300 TCF of technically recoverable U.S. conventional natural gas
reserves. To date, however, gas hydrates have no confirmed commercial production.
Gas hydrates are both a potential resource and a risk, representing a significant hazard
to conventional oil and gas drilling and production operations. If the solid gas hydrates
dissociate suddenly and release expanded gas during offshore drilling, they could disrupt
the marine sediments and compromise pipelines and production equipment on the
seafloor. The tendency of gas hydrates to dissociate and release methane, which can be
a hazard, is the same characteristic that research and development efforts strive to
enhance so that methane can be produced and recovered in commercial quantities.
Developing gas hydrates into a commercially viable source of energy is a goal of the
U.S. Department of Energy (DOE) methane hydrate program, initially authorized by the
Methane Hydrate Research and Development Act of 2000 (P.L. 106-193). The Energy
Policy Act of 2005 (P.L. 109-58, Subtitle F, § 968) extended the authorization through
FY2010 and authorized total appropriations of $155 million over a five-year period.
Gas hydrates occur naturally onshore in permafrost, and at or below the seafloor in
sediments where water and gas combine at low temperatures and high pressures to form
an ice-like solid substance.1 Methane, or natural gas, is typically the dominant gas in the
hydrate structure. In a gas hydrate, frozen water molecules form a cage-like structure
around high concentrations of natural gas. The gas hydrate structure is very compact.
1 The terms methane hydrate and gas hydrate are often used interchangeably, and refer to the
methane-water crystalline structure called a clathrate.

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When heated and depressurized to temperatures and pressures typically found on the
Earth’s surface (one atmosphere of pressure and 70o Fahrenheit), its volume expands by
150 to 170 times. Thus, one cubic foot of solid gas hydrate found underground in
permafrost or beneath the seafloor would produce between 150 to 170 cubic feet of
natural gas when brought to the surface.
Gas hydrates are a potentially huge global energy resource. The United States and
other countries with territory in the Arctic or with offshore gas hydrates along their
continental margins are interested in developing the resource. Countries currently
pursuing national research and development programs include Japan, India, Korea, and
China, among others. Although burning natural gas produces carbon dioxide (CO ), a
2
greenhouse gas, the amount of CO liberated per unit of energy produced is less than 60%
2
of the CO produced from burning coal.2 In addition, the United States imports 20% of
2
its natural gas consumed each year.3 Increasing the U.S. supply of natural gas from gas
hydrates would decrease the nation’s reliance on imported gas and reduce U.S. emissions
of CO if domestically produced gas hydrates substitute for coal as an energy source.
2
Gas Hydrate Resources
There are several challenges to commercially exploiting gas hydrates. How much
and where gas hydrate occurs in commercially viable concentrations are not well known,
and how the resource can be extracted safely and economically is a current research focus.
Estimates of global gas hydrate resources, which range from at least 100,000 TCF to
possibly much more, may greatly overestimate how much gas can be extracted
economically. Reports of vast gas hydrate resources can be misleading unless those
estimates are qualified by the use of such terms such as in-place resources, technically
recoverable
resources, and proved reserves:
! The term in-place is used to describe an estimate of gas hydrate resources
without regard for technical or economical recoverability. Generally
these are the largest estimates.
! Undiscovered technically recoverable resources are producible using
current technology, but this does not take into account economic
viability.
! Proved reserves are estimated quantities that can be recovered under
existing economic and operating conditions.
For example, the U.S. Department of Energy’s Energy Information Agency (EIA)
estimates that total undiscovered technically recoverable conventional natural gas
resources in the United States are approximately 1,300 TCF, but proved reserves are only
200 TCF.4 This is an important distinction because there are no proved reserves for gas
2 U.S. Department of Energy, Energy Information Agency (EIA), at [http://www.eia.doe.gov/
cneaf/coal/quarterly/co2_article/co2.html].
3 In 2007, the United States consumed approximately 23 TCF of natural gas, of which 4.6 TCF
were imported. See EIA at [http://tonto.eia.doe.gov/dnav/ng/ng_sum_lsum_dcu_nus_a.htm].
4 These estimates are as of 2006. Global proved reserves of conventional natural gas are over
(continued...)


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hydrates at this time. Gas hydrates have no confirmed past or current commercial
production.
Until recently, the Department of the Interior’s U.S. Geological Survey (USGS) and
Minerals Management Service (MMS) have reported only in-place estimates of U.S. gas
hydrate resources. However, a November 12, 2008, USGS estimate of undiscovered
technically recoverable gas hydrates in northern Alaska probably represents the most
robust effort to identify gas hydrates that may be commercially viable sources of energy.5
Despite a lack of a production history, the USGS report cites a growing body of evidence
indicating that some gas hydrate resources, such as those in northern Alaska, might be
produced with existing technology despite only limited field testing.
Gas Hydrates on the North Slope, Alaska. The USGS assessment indicates
that the North Slope of Alaska may host about 85 TCF of undiscovered technically
recoverable gas hydrate resources. According to the report, technically recoverable gas
hydrate resources could range from a low of 25 TCF to as much as 158 TCF on the North
Slope. Total U.S. consumption of natural gas in 2007 was slightly more than 23 TCF.

Figure 1. Gas Hydrate Assessment Area,
North Slope, Alaska
Source: USGS Fact Sheet 2008-3073, Assessment of Gas Hydrate Resources on the North Slope, Alaska,
2008, at [http://pubs.usgs.gov/fs/2008/3073/].
Note: TPS refers to total petroleum system, which refers to geologic elements that control petroleum
generation, migration, and entrapment.
Of the mean estimate of 85 TCF of technically recoverable gas hydrates on the North
Slope, 56% is located on federally managed lands, 39% on lands and offshore waters
managed by the State of Alaska, and the remainder on Native lands.6 The total area
comprised by the USGS assessment is 55,894 square miles, and extends from the National
4 (...continued)
6,185 TCF. See EIA at [http://www.eia.doe.gov/emeu/aer/pdf/pages/sec4_3.pdf] and [http://
www.eia.doe.gov/emeu/international/reserves.html].
5 USGS Fact Sheet 2008-3073, Assessment of Gas Hydrate Resources on the North Slope,
Alaska, 2008, at [http://pubs.usgs.gov/fs/2008/3073/].
6 USGS presentation, Timothy S. Collett, October 2008, at [http://energy.usgs.gov/flash/
AlaskaGHAssessment_slideshow.swf].

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Petroleum Reserve in the west to the Arctic National Wildlife Refuge (ANWR) in the east
(Figure 1). The area extends north from the Brooks Range to the state-federal offshore
boundary three miles north of the Alaska coastline. Gas hydrates might also be found
outside the assessment area; the USGS reports that the gas hydrate stability zone — where
favorable conditions of temperature and pressure coexist for gas hydrate formation —
extends beyond the study boundaries into federal waters beyond the three-mile boundary
(Figure 1).
Gas Hydrates in the Gulf of Mexico. On February 1, 2008, the MMS released
an assessment of gas hydrate resources for the Gulf of Mexico.7 The report gives a
statistical probability of the volume of undiscovered in-place gas hydrate resources, with
a mean estimate of over 21,000 TCF. The MMS report estimates how much gas hydrate
may occur in sandstone and shale reservoirs, using a combination of data and modeling,
but does not indicate how much is recoverable with current technology. The report notes
that porous and permeable sandstone reservoirs have the greatest potential for actually
producing gas from hydrates, and gives a mean estimate of over 6,700 TCF of sandstone-
hosted gas hydrates, about 30% of the total mean estimate for the Gulf of Mexico.8 Even
for sandstone reservoirs, however, the in-place estimates for gas hydrates in the Gulf of
Mexico likely far exceed what may be commercially recoverable with current technology.
The MMS is planning similar in-place gas hydrate assessments for other portions of the
U.S. Outer Continental Shelf (OCS), including Alaska.
Gas Hydrates Along Continental Margins. Globally, the amount of gas
hydrate to be found offshore along continental margins probably exceeds the amount
found onshore in permafrost regions by two orders of magnitude, according to one
estimate.9 With the exception of the assessments discussed above, none of the global gas
hydrate estimates is well defined, and all are speculative to some extent.10 One way to
depict the potential size and producibility of global gas hydrate resources is by using a
resource pyramid (Figure 2).11 The apex of the pyramid shows the smallest but most
promising gas hydrate reservoir — arctic and marine sandstones — which may host tens
to hundreds of TCF. The bottom of the pyramid shows the largest but most technically
challenging reservoir — marine shales.
7 U.S. Department of the Interior, Minerals Management Service, Resource Evaluation Division,
“Preliminary evaluation of in-place gas hydrate resources: Gulf of Mexico outer continental
shelf,” OCS Report MMS 2008-004 (Feb. 1, 2008), at [http://www.mms.gov/revaldiv/
GasHydrateFiles/MMS2008-004.pdf].
8 Ibid., table 16.
9 George J. Moridis et al., “Toward production from gas hydrates: current status, assessment of
resources, and simulation-based evaluation of technology and potential,” 2008 SPE
Unconventional Reservoirs Conference, Keystone, CO, February 10, 2008, p. 3, at
[http://www.netl.doe.gov/technologies/oil-gas/publications/Hydrates/reports/G308_SPE11416
3_Feb08.pdf].
10 Ibid.
11 Roy Boswell and Timothy S. Collett, “The Gas Hydrate Resource Pyramid,” Fire in the Ice,
Methane Hydrate R&D Program Newsletter, Fall 2006, pp. 5-7, at [http://www.netl.doe.gov/
technologies/oil-gas/FutureSupply/MethaneHydrates/newsletter/newsletter.htm].


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Sandstones are considered superior reservoirs because they have much higher
permeability — they allow more gas to flow — than shales, which can be nearly
impermeable. The marine shale gas hydrate reservoir may host hundreds of thousands of
TCF, but most or all of that resource may never be economically recoverable. It is likely
that continued research and development efforts in the United States and other countries
will focus on producing gas hydrates from arctic and marine sandstone reservoirs.
Figure 2. Gas Hydrate Reservoir Pyramid
Source: Roy Boswell and Timothy S. Collett, “The Gas Hydrate Resource Pyramid,” Fire in the Ice,
Methane Hydrate R&D Program Newsletter, Fall 2006.
Gas Hydrate Hazards
Gas hydrates are a significant hazard for drilling and production operations.12 Gas
hydrate production is hazardous in itself, as well as for conventional oil and gas activities
that place wells and pipelines into permafrost or marine sediments. For activities in
permafrost, two general categories of problems have been identified: (1) uncontrolled gas
releases during drilling; and (2) damage to well casing during and after installation of a
well. Similar problems could occur during offshore drilling into gas hydrate-bearing
marine sediments. Offshore drilling operations that disturb gas hydrate-bearing sediments
could fracture or disrupt the bottom sediments and compromise the wellbore, pipelines,
rig supports, and other equipment involved in oil and gas production from the seafloor.13
Problems may differ somewhat between onshore and offshore operations, but they
stem from the same characteristic of gas hydrates: decreases in pressure and/or increases
in temperature can cause the gas hydrate to dissociate and rapidly release large amounts
of gas into the well bore during a drilling operation.
Oil and gas wells drilled through permafrost or offshore to reach conventional oil
and gas deposits may encounter gas hydrates, which companies generally try to avoid
because of a lack of detailed understanding of the mechanical and thermal properties of
12 Timothy S. Collett and Scott R. Dallimore, “Detailed analysis of gas hydrate induced drilling
and production hazards,” Proceedings of the Fourth International Conference on Gas Hydrates,
Yokohama, Japan, April 19-23, 2002.
13 George J. Moridis and Michael B. Kowalsky, “Geomechanical implications of thermal stresses
on hydrate-bearing sediments,” Fire in the Ice, Methane Hydrate R&D Program Newsletter,
Winter 2006.

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gas hydrate-bearing sediments.14 However, to mitigate the potential hazard in these
instances, the wells are cased — typically using a steel pipe that lines the wall of the
borehole — to separate and protect the well from the gas hydrates in the shallower zones
as drilling continues deeper. Unless precautions are taken, continued drilling may heat
up the sediments surrounding the wellbore, causing gas from the dissociated hydrates to
leak and bubble up around the casing. Once oil production begins, hot fluids flowing
through the well could also warm hydrate-bearing sediments and cause dissociation. The
released gas may pool and build up pressure against the well casing, possibly causing
damage.15 Some observers suggest that exploiting the gas hydrate resources by
intentionally heating or by depressurization poses the same risks — requiring mitigation
— as drilling through gas hydrates to reach deeper conventional oil and gas deposits.16
Gas Hydrate Research and Development
A goal of the DOE methane hydrate research and development (R&D) program is
to develop knowledge and technology to allow commercial production of methane from
gas hydrates by 2015.17 Since the Methane Hydrate Research and Development Act of
2000 (P.L. 106-193) was enacted, DOE has spent $87.3 million, or approximately 78%
of the $112.5 million authorized by law. The Energy Policy Act of 2005 (P.L. 109-58)
extended the program’s authorization through FY2010. The program is planning an
Alaska production test and Gulf of Mexico offshore expedition, both starting in 2009. In
Alaska, a production test starting in 2009 is expected to provide critical information about
methane flow rates and sediment stability during gas hydrate dissociation. Results from
the two-year test may be crucial to companies interested in producing gas hydrates
commercially. The Gulf of Mexico program is aimed at validating techniques for locating
and assessing commercially viable gas hydrate deposits. Both projects have international
and industry partners.
Researchers identify a need to better understand how geology in the permafrost
regions and on continental margins controls the occurrence and formation of methane
hydrates.18 They underscore the need to understand fundamental aspects — porosity,
permeability, reservoir temperatures — of the geologic framework that hosts the gas
hydrate resource to improve assessment and exploration, to mitigate the hazard, and to
enhance gas recovery.
Together with advances in R&D, economic viability will depend on the relative cost
of conventional fuels, as well as other factors such as pipelines and other infrastructure
needed to deliver gas hydrate methane to market. Additionally, price volatility will likely
affect the level of private sector investment in commercial production of gas hydrates.
14 Moridis and Kowalski (2006).
15 Collett and Dallimore (2002).
16 Personal communication, Ray Boswell, Manager, Methane Hydrate R&D Programs, DOE
National Energy Technology Laboratory, Morgantown, WV, Nov. 5, 2008.
17 DOE methane hydrate R&D program, at [http://www.netl.doe.gov/technologies/oil-gas/
FutureSupply/MethaneHydrates/rd-program/rd-program.htm].
18 Collett and Dallimore (2002); Moridis and Kowalski (2006).