Gas Hydrate in Nature

Gas hydrate is a naturally occurring, ice-like substance that forms when water and gas combine 

under high pressure and at moderate temperatures. Methane is the most common gas present in 

gas hydrate, although other gases may also be included in hydrate structures, particularly in areas 

close to conventional oil and gas reservoirs. Gas hydrate is widespread in ocean-bottom sediments 

at water depths greater than 300–500 meters (m; 984–1,640 feet [ft]) and is also present in areas with 

permanently frozen ground (permafrost). Several countries are evaluating gas hydrate as a possible 

energy resource in deepwater or permafrost settings. Gas hydrate is also under investigation to 

determine how environmental change may affect these deposits.

Ice-like crystals of methane hydrate made in the laboratory sustain a flame as the gas is released from the degrading hydrate.

Gas hydrate consists of water molecules that form cages 

enclosing gas molecules. Most naturally occurring gas hydrate 

contains methane, which is the natural gas that is piped into 

many homes. In addition to methane, gases like ethane, carbon 

dioxide, and hydrogen sulfide are sometimes incorporated into 

gas hydrate. Gas hydrate represents a highly concentrated form 

of methane. For the most common crystal structure (fig. 1A), 

1 cubic inch (in3) of gas hydrate will leave behind as much as 

0.8 in3 of water and 180 in3 of methane when the hydrate breaks 

down at room pressure and temperature. 

Studies of gas hydrate originally focused on ensuring the 

flow of oil and gas in pipelines, which often clogged with gas 

hydrate. Since the 1980s, there has been strong international 

interest in naturally occurring gas hydrate (fig. 1B), which is 

widespread on Earth and holds an estimated 1,800–12,400 gigatons of carbon, corresponding to 3–24.8 × 1015 cubic meters 

(106,000–876,000 trillion cubic feet or TCF) of methane 

(Boswell and Collett, 2011). For comparison, the United 

States used an estimated 27.49 TCF of natural gas in 2016 

(U.S. Energy Information Administration, 2017).

Marine Gas Hydrate

In nature, the sediments of deep marine continental margins 

host nearly 99 percent of the world’s gas hydrate, typically at 

water depths of 500 m (approximately 1,640 ft) and greater. The 

sediments on continental margins often contain substantial concentrations of organic carbon, which is used by microbes to produce methane. This methane, as well as older microbial methane 

or even methane that migrates upward from deep conventional 

gas reservoirs, can combine with sediment pore waters to form 

gas hydrate beneath the sea floor. Gas hydrate also sometimes 

forms directly on the sea floor where fluids leak into the ocean 

at seep sites, but such deposits are not considered an important 

component of the global gas hydrate inventory.

In continental margin sediments, the natural pressure 

and temperature conditions mean that the gas hydrate zone 

thins out upslope and thickens downslope, reaching hundreds 

of meters (100 m equals 328 ft) of thickness as water depths 

increase (fig. 2). In many locations, field studies show that only 

A

B

Figure 1. A, A scanning 

electron microscope 

image of methane 

hydrate crystals formed in 

sediments from the Indian 

Ocean. The 10 micrometer (μm) scale is approximately 4/10,000ths 

of an inch or a quarter of the width of a human hair. B, Chunks of 

white gas hydrate with gray sediment recovered from beneath the 

sea floor of the Gulf of Mexico. 

Thick onshore 

permafrost

Shallow 

Arctic Ocean 

continental shelf

Permafrost 

Gas hydrate 

stability zone

Landward limit of

gas hydrate stability

Gas hydrate stability zone

500 meters

Atmosphere: oxidation

consumes methane

Ocean: oxidation 

consumes methane

Oxidation in sediments 

consumes methane

Seep

Deepwater marine hydrate

1,640 feet

Figure 2. Schematic cross section showing gas hydrate within 

and beneath permafrost (left side) and in deepwater marine 

sediments (right side). The locations described in orange are the 

most susceptible to climate processes that can affect the stability 

of methane hydrate deposits. Oxidation can destroy methane in the 

sediments, in the water column, and in the atmosphere.

U.S. Department of the Interior

U.S. Geological Survey Printed on recycled paper

Fact Sheet 2017–3080 

January 2018
a small fraction (less than 5 percent) of the sediments host gas 

hydrate, which is sometimes concentrated in specific layers or in 

fractures.

Deepwater marine gas hydrate occurs on all continental margins of the United States (fig. 3). The U.S. Bureau of 

Ocean Energy Management (BOEM) estimates that an average 

of 21,444 TCF of methane is present in gas hydrate in sediments of the northern Gulf of Mexico. For the U.S. Atlantic 

Ocean margin, the estimate is 21,702 TCF, and for the Pacific 

margin (excluding Alaska) the assessment yields an average of 

8,192 TCF (Bureau of Ocean Energy Management, 2012). 

For more than two decades, deepwater gas hydrate has 

been the focus of ocean drilling expeditions led by scientific 

consortia, governments, and private companies. Among the best 

studied locations are the northern Gulf of Mexico and areas 

offshore of Oregon; Vancouver, Canada; India; Japan; South 

Korea; and China.

120° 60° 0° 60° 120° 180° 

90°

60°

30°

0°

30°

60°

JAPAN

Indian Ocean

ALASKA

Arctic Ocean

Gulf of Mexico

TIBET

Pacific Ocean

Atlantic Ocean

Arctic Ocean

ANTARCTICA

Lake Baikal

Recovered hydrate

Inferred hydrate

Drilling expeditions

EXPLANATION

Figure 3. Map showing locations where gas hydrate has been 

recovered, where gas hydrate is inferred to be present on the basis 

of seismic data, and where gas hydrate drilling expeditions have 

been completed in permafrost or deep marine environments, also 

leading to recovery of gas hydrate.

Permafrost-Associated Gas Hydrate

Globally, only a small fraction of natural gas hydrate is 

present in areas with thick permafrost, which refers to sediments 

that remain permanently frozen because of profound cooling 

of the ground during glacial events occurring over the past few 

hundreds of thousands of years. In the United States, most of 

the remaining continuous permafrost is onshore on the Alaskan 

North Slope. Some permafrost that originally formed onshore 

during the last ice age has been flooded by sea level rise during 

the past 15,000 years and now persists offshore beneath the shallow waters of the Arctic Ocean continental shelf (fig. 2). 

In permafrost settings, temperature and pressure conditions 

appropriate for pure methane hydrate to be stable occur in the 

lowermost part of the frozen sediments and in the uppermost part 

of the underlying, unfrozen sediments. Permafrost-associated gas 

hydrate probably formed when gas and water froze in place during ice-age cooling events. Prior to the cooling events, most, but 

not all, of the gas contained in permafrost-associated gas hydrate 

deposits may have migrated upward from deep conventional gas 

reservoirs. Permafrost-associated gas hydrate has been extensively studied in northern Alaska and in the Mackenzie Delta of 

the Canadian Arctic (Collett and others, 2009).

Prospecting for Gas Hydrate

Although gas hydrate is widespread, finding the deposits can be challenging. In marine settings, researchers sometimes identify gas hydrate by mapping a seismic reflector that 

marks the base of the gas hydrate stability zone in the sediments (fig. 4). Where this reflector is found, gas hydrate is 

present in the overlying sediments; however, gas hydrate is also 

sometimes present in places that lack this reflector.

Electromagnetic surveys are sometimes combined with 

seismic imaging in prospecting for gas hydrate. Like ice, gas 

hydrate acts as an electrical resistor, making it harder for electrical current to flow through sediments. Electromagnetic surveys 

are therefore highly effective at finding gas 

hydrate in some marine settings.

Electromagnetic and seismic surveys 

are typically conducted at the regional scale. 

At a local scale, boreholes drilled in the sea 

floor or permafrost provide direct access 

to the sediments. Special instruments are 

deployed in boreholes to infer the composition of the sediment layers, the amount of 

gas and gas hydrate, fracture patterns, and 

other characteristics.

Gas Hydrate and Energy Resources

Gas hydrate traps large amounts of 

methane in compact deposits at shallower 

and more accessible depths than most 

conventional gas reservoirs. For this reason, there has long been 

interest in gas hydrate as a potential energy resource. Hydratebearing sands are a particular target for energy studies because 

of the high concentrations of gas hydrate sometimes found in 

these sediments (fig. 5). Existing technology is well-suited to 

4.0

5.0

Sea floor

Bottom simulating reflector (BSR) Sediment layers

Bottom simulating reflector (BSR)

Two-way travel time(s)

Water column

500 METERS

1,640 FEET

10 KILOMETERS

6.2 STATUTE MILES

Figure 4. A seismic image acquired by the U.S. Geological Survey 

on the U.S. Atlantic margin about 300 kilometers (186 statute miles) 

offshore Delaware in 2014 shows the upper layers of sediment in the 

sea floor and a strong bottom simulating reflector (BSR) that crosses 

sediment layering. Sediments shallower than the BSR may host gas 

hydrate, while sediments deeper than the BSR may have gas bubbles 

in the pore space. Water depth on the left side of the image is 2,850 

meters (9,350 feet). Image courtesy of D. Hutchinson (USGS).
Arctic sands

Marine sands

Marine fracture fill

Vent site related

 massive hydrate

Marine fine-grained

Increasing in-place gas

Decreasing reservoir quality

Figure 5. Gas hydrate resource pyramid showing the relative 

proportion of methane trapped in these deposits in each setting. 

Although gas hydrate in fine-grained marine sediments contains the 

most methane, these deposits are unlikely to be exploitable as an 

energy resource. Modified from Boswell and Collett (2011).

extracting methane from hydrate in sandy sediments (Boswell 

and Collett, 2011).

As of 2017, gas hydrate is not exploited commercially as a 

source of natural gas. Because the resource is not yet proven as 

commercially viable, there are no known reserves of methane in 

gas hydrate. Short-term research tests of gas production from gas 

hydrate have been conducted in permafrost areas in Canada and 

the United States and in the deepwater marine environment offshore of Japan and China. Longer duration (months to more than 

a year) research production tests are planned for the future, and 

some countries hope to achieve commercial-scale production of 

gas from hydrate within the next several decades.

The most common technique for producing gas from gas 

hydrate lowers the pressure (depressurization) within the sediments, thereby triggering breakdown (dissociation) of the gas 

hydrate into gas and water (Collett and others, 2009). Such 

depressurization can be completed with existing technology. 

Because of the thermodynamic characteristics of gas hydrate, 

there is no danger that dissociation will continue unabated once 

it starts. In fact, hydrate-bearing sediments sometimes have to 

be heated to drive continued release of gas after depressurization 

starts. An additional challenge for production is managing large 

amounts of water released when gas hydrate breaks down.

Gas Hydrate and the Environment

Gas hydrate is stable only within specific ranges of temperature and pressure. As average atmospheric and ocean temperatures increase, gas hydrate in permafrost and deep marine 

settings may break down and release the trapped methane. Much 

of the liberated methane is likely to remain in the sediments. 

Methane that escapes from the sea floor into the ocean (fig. 6) 

is typically converted to carbon dioxide by micro-organisms, a 

process that increases the acidity of ocean waters. 

About 5 teragrams (Tg; 1.1 × 1010 pounds) of atmospheric 

methane emissions per year is attributed to the breakdown of 

gas hydrate. This amount of methane is about 1 percent of the 

annual methane emissions of 555 Tg per year from all natural 

and anthropogenic sources. Methane is a potent greenhouse 

gas, and a critical research direction is determining whether 

Figure 6. A photograph taken by Oceaneering Inc. using the 

Global Explorer remotely operated vehicle shows methane bubble 

streams emanating from the sea floor within a field of mussels 

at approximately (~) 950 meters (~3,116 feet) water depth ~110 

kilometers (~68 miles) off the shore of Virginia during a U.S. 

Geological Survey cruise in 2017. Green laser dots are separated by 

10 centimeters (3.94 inches). 

methane hydrate breakdown is truly contributing methane to the 

atmosphere now or is likely to do so in the next century or more 

(Ruppel and Kessler, 2017). 

Since at least the last part of the 20th century, methane 

hydrate has likely been breaking down in two environmental 

settings: (1) within the sediments of upper continental slopes at 

water depths of 300–800 m (1,000–2,600 ft) and (2) in locations 

around the Arctic Ocean where permafrost that was previously onshore has been flooded by sea level rise during the past 

15,000 years. Globally, most gas hydrate deposits are so deeply 

buried that the gas hydrate is likely to be stable for centuries or 

more under most model scenarios for future warming (Ruppel 

and Kessler, 2017).

Gas Hydrate and Sea-Floor Failure

Gas hydrate often is present beneath large-scale submarine 

slide scars, but there is no evidence that gas hydrate causes seafloor failures. When gas hydrate breaks down, it releases methane gas and water into the surrounding sediments, increasing the 

internal pressure in the sediments. These conditions can prime 

slopes for failure if triggered by an earthquake or the addition of 

too much sediment on the sea floor.

When gas hydrate is present at high concentrations in sediments, it binds the sediment grains, which creates a mechanically strong layer. Gas-charged sediments, which are often found 

beneath sediments that host gas hydrate, are relatively weak. The 

layering of sediments with different mechanical strengths might 

also exacerbate sea-floor failure under certain conditions.

Future Studies

Several countries are pursuing potential commercialization 

of gas production from methane hydrate to expand their domestic energy resources. The U.S. Geological Survey participates 

in national and international expeditions (fig. 7) that advance 

understanding of natural gas hydrate deposits for energy studies 

and also assesses the amount of methane trapped in the deposits. The next generation of tests to produce methane from gas 
hydrate is likely to including monitoring to track potential gas 

escape, ground subsidence, and the amount of coproduced water.

In many places, gas hydrate deposits are still unexplored. 

Existing geophysical techniques can identify the deposits, and 

research will continue to develop new technology to better 

determine the amount of gas hydrate in sediments. Further deep 

drilling, characterization of the sediments through the use of 

borehole instrumentation, and studies on recovered hydratebearing sediments can also advance knowledge. 

For environmental studies of gas hydrate, a key challenge 

remains fingerprinting gas released from methane hydrate degradation so that it can be tracked through the ocean and atmosphere. In addition, scientists are striving to accurately assess the 

amount and locations of gas hydrate deposits that are susceptible 

to environmental change over decades, centuries, and millennia.

1990 2000 2010 2020 2030 2040

ODP Leg 164: 

Blake Ridge

(South Carolina)

ODP Leg 204: 

Hydrate Ridge

(Oregon)

IODP Exp. 311: 

Vancouver Margin

Cabled gas hydrate observatories

Japan

USA (Gulf of Mexico/DOE)

 

Korea (UBGH)

India (NGHP)

China (GMGS)

Gumusut-Kakap (Malaysia)

Deepwater Marine Permafrost

Canada 

(Mallik)

USA (Alaska 

North Slope)

China (Tibetan 

Plateau)

DOE/British Petroleum

Mt. Elbert

Academic

Ocean Drilling

First commercial scale production from

hydrates, possibly in countries lacking 

significant domestic gas reserves?

 

Asia?

COMPLETED FUTURE

DOE/ConocoPhillips

CO2

 hydrate test Hot

Ice

Japan Sea 

NEPTUNE (Canada)

US Ocean Observing Initiative 

(Hydrate Ridge)

Long-term 

production test

Update 12.17

?

?

IODP Exp. 372: 

New Zealand Margin

IODP 386: Gulf of Mexico

(with DOE support)

Coring and (or)

borehole logging 

EXPLANATION

IODP 386

Nankai 

Production testing

Solid (completed)

 Open (planned)

Figure 7. Timeline showing past and future drilling and deep-sea 

coring and borehole logging expeditions as of late 2017. The goal 

of the permafrost and deepwater marine programs is to evaluate 

the potential of gas hydrate as a resource, whereas the goal of the 

academic ocean drilling programs is to focus on critical research 

questions related to natural gas hydrate deposits. DOE refers to 

the U.S. Department of Energy. The academic programs are the 

Ocean Drilling Program (ODP; 1983–2003), the Integrated ODP (IODP; 

2003–2013), and the International Ocean Discovery Program (IODP), 

which started in 2013. The international marine drilling programs are 

the Ulleung Basin Gas Hydrates project (UBGH; Korea), the National 

Gas Hydrates Project (NGHP; India), and the Guangzhou Marine 

Geological Survey (GMGS; China).

References Cited

Boswell, R., and Collett, T.S., 2011, Current perspectives on 

gas hydrate resources: Energy & Environmental Science, v. 

4, p. 1206–1215. [Also available at https://doi.org/10.1039/

C0EE00203H].

Bureau of Ocean Energy Management, 2012, Assessment of 

in-place gas hydrate resources of the lower 48 United States 

outer continental shelf: Bureau of Ocean Energy Management Fact Sheet RED–2012–01, 4 p. [Also available at 

https://www.boem.gov/uploadedFiles/BOEM/Oil_and_Gas_

Energy_Program/Resource_Evaluation/Gas_Hydrates/BOEMFactSheetRED_2012-01.pdf].

Collett, T.S., Johnson, A.H., Knapp, C.C., and Boswell, R., 2009, 

Natural gas hydrates—A review, in Natural gas hydrates—

Energy resource potential and associated geologic hazards, ed. 

Collett, T.S., Johnson, A.H., Knapp, C.C., and Boswell, R.: 

American Association of Petroleum Geologists Memoir 89, 

p. 146–219. 

Ruppel, C.D., and Kessler, J.D., 2017, The interaction of 

climate change and methane hydrates: Reviews of Geophysics, v. 55, no. 1, p. 126–168. [Also available at 

https://doi.org/10.1002/2016RG000534].

U.S. Energy Information Administration, 2017, Natural gas 

annual supply and disposition by State: U.S. Energy Information Administration data, accessed December 11, 2017, at 

https://www.eia.gov/dnav/ng/ng_sum_snd_a_EPG0_VC0_

Mmcf_a.htm.

By Carolyn Ruppel

The USGS Gas Hydrates Project is supported by the USGS 

Coastal and Marine Geology Program and the USGS Energy 

Resources Program.

Further Information:

Coastal and Marine Geology Program Coordinator

Energy Resources Program Coordinator

U.S. Geological Survey

12201 Sunrise Valley Drive

Reston, VA 20192 USA

Email: webmaster-marine@usgs.gov;

 gd-energyprogram@usgs.gov

• Overview of the U.S. Geological Survey’s Gas Hydrates 

Project:

https://woodshole.er.usgs.gov/project-pages/

hydrates/index.html

• U.S. Geological Survey’s Energy Resources Program gas 

hydrates site:

https://energy.usgs.gov/OilGas/UnconventionalOilGas/

GasHydrates.aspx

• The U.S. Geological Survey’s Gas Hydrates Project fact 

sheet:

https://doi.org/10.3133/fs20173079

Any use of trade, firm, or product names is for descriptive purposes only and does not 

imply endorsement by the U.S. Government.

ISSN 2327-6916 (print)

ISSN 2327-6932 (online)

https://doi.org/10.3133/fs20173080