Methane Gas Hydrates

Gas hydrate can occur as nodules, laminae, or veins within sediment.

Methane hydrates are important for these reasons:

• They may contain a major energy resource;
• They may be a significant hazard because they alter sea floor sediment stability, influencing collapse and landslides; and
• The hydrate reservoir may have a strong influence on the environment and climate because methane is a significant greenhouse gas.

Inset image: Gas hydrates are crystalline solids consisting of gas molecules, usually methane, each surrounded by a cage of water molecules.
Main image: Gas hydrate looks and acts like ice, but it contains vast amounts of methane. If you put a match to it, it burns with a soft orange flame. The volume of energy stores in methane hydrate exceeds that of the world's coal, oil, and conventional natural gas combined.

In May 2000, Congress and the President of the United States enacted Public Law 106-193, the Methane Hydrate Research and Development Act of 2000, which instituted a National Gas Hydrate research program. The work is being coordinated by the Interagency Coordination Committee (ICC), consisting of representatives from the six government agencies and in consultation with advisory panels from industry and academia:

• Department of Energy, through Office of Fossil Energy and represented by the Strategic Center for Natural Gas;
• Department of Commerce, represented by NOAA;
• Department of Defense, represented by Naval Research Laboratory;
• Department of the Interior, represented by MMS and USGS;
• National Science Foundation.

The USGS gas hydrate research concentrates in four major areas:

• Natural hazards
• Resources
• The Environment
• Information and Data Management

Most of the USGS work on methane hydrates is done in cooperation with other agencies, including the MMS. The overall goal is to understand geologic processes that control methane hydrate in the natural environment.

The principal scientific objectives of the USGS Gas Hydrates project are:

• To utilize geophysical data to learn about natural hydrate relationships, distribution, and controls through field experiments, computer processing, and theoretical analysis.
• To make measurements that compare and contrast synthetic and natural gas hydrates in order to improve the interpretation of geophysical data.
• To understand the effect of hydrate on the physical properties of sediments through laboratory and drill hole experiments.
• To be able to predict the effect of gas hydrate on sediment mass movement.
• To understand and assess the resource potential of selected gas hydrate reservoirs.
• To understand the global distribution, volume, and geochemistry of gas hydrate.
• To evaluate the effect of geologic setting, geologic processes and host sediment properties on gas hydrate concentration and distribution through integrated field and laboratory studies.

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Methane hydrates exist in large quantities in marine sediments in a layer several hundred meters thick directly below the sea floor and is association with permafrost in the Arctic. Methane hydrates form naturally under conditions of high pressures and relatively low temperatures. Under these conditions, methane molecules are compressed into very tightly packed ice-crystal cages. Methane hydrates occur naturally in Arctic permafrost regions at depths greater than 200m (656 ft). They also form at ocean depths of 500m (1,600 ft) or more where temperature hover near freezing and the weight of the overlying water produces high pressures. The pressures and relatively low temperatures allow high concentrations of methane to accumulate in the ice.

Locations of known and inferred gas hydrate occurrences in oceanic sediments of outer continental margins and permafrost regions.
Only a limited number of gas hydrate deposits have been examined in any detail.

The USGS scientists are investigating the occurrences of, and geological processes that control, methane hydrate in the natural environment. The studies include: 1) identifying and quantifying gas hydrate using remote sensing techniques; 2) determining its concentration into possibly extractable accumulations; 3) studying how hydrates change the strength of sediments and generate overpressures in the seabed; 4) understanding processes of seafloor mobilization; and 5) determining how methane gas is sequestered in the sediments and how it gets transferred into oceans and the atmosphere.

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The Gulf of Mexico (GOM)

The USGS is partnering with MMS in the Gulf of Mexico (GOM). The northern Gulf of Mexico is unique in the world for containing numerous active hydrocarbon seeps and more than 50 locations where intact biogenic hydrates (i.e., hydrates formed by microbial activity in the upper several hundred meters of deep-sea sediment) and thermogenic hydrates (i.e., hydrates formed by thermal breakdown of organic material at greater depths) are found.

These gas hydrates pose a potential threat to the safety of drilling platforms by triggering mass failure and landslides; thus interest in these hydrates has increased as commercial drilling moves into deeper waters.

The USGS work with MMS has occurred in various instances regarding gas hydrates. To better understand natural gas hydrate distribution across the continental slope of the northern Gulf of Mexico, a giant piston-coring cruise was recently conducted abroad the 120-m long French research vessel Marion Dufresne. Scientists from the United States (USGS and MMS), France, Germany, the Netherlands, Canada, Japan, Greece, Russia, and Mexico participated in the cruise.

Gas hydrates are relatively abundant in sea-floor mounds on the GOM. Here methane is actively dissociating from a hydrate mound.

In July 2002, approximately twenty, 35-40 meter cores were collected aboard the Marion Dufrense to determine whether gas hydrates exist away from obvious seafloor mounds in adjacent sedimentary basins, and if so, whether significant deposits exist deep within these basins.

The sites for the giant piston coring operations in the GOM were selected based on focused geophysical surveys, and information and data provided by oil companies and the MMS.

The USGS worked with MMS and used their proprietary 3-D seismic coverage of the Gulf of Mexico to locate priority core sites. The USGS utilized elastic wave-speed measurements to assist in the evaluation of seismic data acquired in the seismic site surveys for the piston coring locations. Also, MMS data were used identify lease block owners, characterize the pre-cruise sites, and develop a comprehensive framework understanding of the region.

GHASTLI was designed to measure properties
of natural and laboratory-formed gas hydrates and
determine hydrate-bearing sediment properties.

Gulf of Mexico:
A box core being subsampled aboard the Marion Dufresne.
Sediment in the foreground is being placed into a pore water
squeezer vessel. This core, which was located on a large diapir,
was saturated with liquid hydrocarbons.

Gas hydrate samples and cores recovered in the coring operations will be analyzed by the GHASTLI (Gas Hydrate and Sediment Test Laboratory Instrument) system, located at USGS laboratories in Woods Hole, MA. The scientists will look at evidence of gas hydrate in the shallow sub-bottom and document the magnitude of methane flux through the sediments at distances away from known hydrate mounds and active venting.

The GHASTLI facility at Woods Hole stimulates deep-sea conditions. There are substantial direct observational evidence that major seafloor collapses, submarine slides, and drilling hazards are linked to the presence of hydrate. The loss of seafloor equipment in industry drilling operations suggests that hydrate breakdown may have been a contributing cause. Hydrate processes influence seafloor stability by causing substantial changes in the physical properties of shallow sediments. The USGS is testing properties of gas hydrate-bearing sediments at the GHASTLI system facility. The GHASTLI provides that capability of forming gas hydrate in sediments at simulated deep-sea conditions and accepting gas hydrate-bearing cores drilled at sea or in the Arctic. Acoustic velocity measurements made in the GHASTLI facility of gas hydrate-bearing sediments are critical to the interpretation of seismic data.

Information gathered from this cruise will be evaluated by the Joint Industry Program (JIP) to help guide plans for drilling deeper into the gas hydrate section sometime in 2003 or 2004.

The JIP is funded jointly by DOE and member companies to develop a drilling program for gas hydrates in the Gulf of Mexico. MMS is currently a member of the JIP. USGS is a research advisor to the JIP. As a science advisor, numerous USGS scientists are working with the JIP in workshops and informal meetings to develop a robust drilling plan for 2003.

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U.S. Exclusive Economic Zone and Alaska

The areas shown in blue are potential areas of an extended continental
shelf beyond the 200 nautical mile limit (red) Exclusive Economic Zone.

The USGS 1995 National Assessment of United States Oil and Gas Resources included for the first time an assessment of the in-place natural gas hydrate resources of the U.S. onshore and offshore regions. Eleven gas hydrate plays were identified within four offshore and one onshore gas hydrate provinces. The offshore gas hydrate region included all of the U.S. Exclusive Economic Zone (EEZ) (shown in red in above figure) adjacent to the lower 48 States and onshore northern Alaska. The 1995 assessment was conducted in part as a request from MMS. This assessment was the basis of the gas hydrate resource numbers used by DOE and others for the development of the National Gas Hydrate research program in 2000. The USGS has learned a great deal about hydrates since the 1995 assessment and are going to use this new knowledge to conduct a new onshore northern Alaska gas hydrate assessment. This new assessment will be limited to onshore Alaska only and USGS will focus on gas hydrate recovery aspects (not an in-place assessment). This assessment will deal with gas hydrate accumulations on both State of Alaska and Federal managed lands in northern Alaska; and will be conducted as a cooperative study with BLM and the State of Alaska Department of Natural Resources.

As far as a new marine hydrate assessment, the USGS Energy Program plans to continue our contribution to a new marine gas hydrate assessment led by MMS. The USGS Energy Program representatives met with MMS program managers in late April 1993 to review ongoing and proposed gas hydrate assessment activities in the two agencies. In July 1993, there is a gas hydrate assessment project-scoping meeting hosted by MMS, which will begin the process of developing the methodologies to be used in this new assessment effort. Several USGS research scientists will participate in the July planning meeting. We will work in support of MMS, providing technical knowledge regarding marine gas hydrates and assessment methodologies.

The idea of an MMS-USGS Coordinating Committee would be very useful from several different standpoints and benefit our gas hydrate research and assessment activities. Our ongoing gas hydrate assessment activities in Alaska will greatly benefit by the synergy of working with MMS on the marine gas hydrate assessment, mainly through the development of compatible geologic databases and assessment methodologies.

How Much Gas Hydrate Exists?

USGS scientists believe that we will most likely not see significant worldwide gas production from hydrates for the next 30-50 years. Gas recovery from hydrates is hindered because they occur as a solid in nature and are commonly widely dispersed in hostile Arctic and deep marine environments. Current technical issues and costs prohibit the recovery of these hydrates in an economical manner. However, in certain parts of the world with unique economic or political motivations, gas hydrates may become a sustainable source of natural gas sooner-possibly within the next 5 to 10 years.

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Mississippi Mineral Resources Institute (MMRI)

Within MMRI is the Center for Marine Resources and Environmental Technology (CMRET), which functions under the guidance and administration of MMS to provide DOI access to applied academic expertise in marine mineral resource technology. The Center was established to identify, design, and test equipment and techniques to study gas hydrates and marine minerals in the GOM. In the past USGS has collaborated in joint research projects with MMRI in the Gulf of Mexico (1998 cruise aboard the MMRI vessel R/V Tommy Munro). More recently, USGS has been participating in planning meetings of CMRET for hydrates research.