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Energy Minerals Division

A Division of the American Association of Petroleum Geologists

Gas Hydrates

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Introduction

Gas hydrates are crystalline solids that consist of gas molecules, usually methane, surrounded by water molecules. The gas molecules are densely packed in a crystalline structure so that hydrate deposits can store vast quantities of methane. Estimates of the amount of carbon bound in gas hydrates are almost twice the amount of carbon found in all known fossil fuels on Earth; hence, hydrates represent a dominant unconventional energy resource. Though these hydrates are abundant worldwide, particularly in Arctic regions and in marine sediments, there is much to learn about how they form, evolve, interact with surrounding sediments, and affect environmental conditions when extracted.

Progress toward commercialization of gas hydrates in North America and Asia is continuing in 2009, with some notable advancement in both resource assessment and technology.

U.S. Exploration Activity

With many challenges and unknowns remaining long-term, economically-viable production of natural gas from hydrates is as yet unproven. Gas hydrate R&D is the type of high cost, high-risk, high-potential endeavor that calls for government economic support. Progress in the U.S. has been limited by the relatively low budget levels of the Department of Energy (DOE) methane hydrate program, the primary source of funding for U.S. hydrate efforts.

A long-term, industry-scale production test is planned for the North Slope in the summer of 2010 as a follow-up to BP’s successful “Mt. Elbert” stratigraphic test in 2007. The location has not yet been announced. In addition, ConocoPhillips is planning a CO2 injection test in the summer of 2010 to evaluate the potential of CO2 substitution in a methane hydrate-bearing sand to both sequester CO2 and yield methane production. In the Gulf of Mexico, the Joint Industry Program (JIP) led by Chevron initiated field operation on April 16 utilizing the semi-submersible “Helix Q4000”. The three-week expedition conducted logging-while-drilling (LWD) operations at multiple sites to test a variety of geologic/geophysical models for the occurrence of gas hydrate in sand reservoirs in the deepwater Gulf of Mexico. The results from the JIP drilling program will be used to calibrate the exploration model for marine hydrate.

International Exploration Activity

While many countries have expressed interest in the resource potential of gas hydrate, few have been willing to commit the financial resources needed to begin valid assessments that could lead to commercial development. Outside of the U.S., significant programs are currently being carried out in Japan, India, Canada, South Korea, and the Peoples Republic of China.

Resource Estimates

Resource estimates for the Gulf of Mexico and North Slope of Alaska were published in 2008 by federal agencies. The Minerals Management service conducted an evaluation of the petroleum system for the Gulf of Mexico and estimated a total gas hydrate volume of between 11,112 and 34,423 TCF, and a mean estimate of 6,717 TCF in place in sandstone reservoirs. Assessments for the Atlantic and Pacific margins are on-going, and the resource potential of those locations may actually be larger than the Gulf of Mexico estimate. The USGS, in cooperation with the BLM, released an assessment of the undiscovered, technically recoverable gas hydrate resources on the North Slope of Alaska. Using an assessment methodology based on detailed analysis of geological data, the USGS estimated undiscovered, technically recoverable gas resources of 85.4 TCF within gas hydrate.

Critical Technology Needs

Current commercialization efforts are constrained by technology needs in three areas: the lack of thorough and diverse exploration protocol for identifying deposits where hydrate is concentrated and has resource potential, the lack of proven technology for commercial-scale production, and the lack of an environmental impact assessment protocol. All three of these areas are being addressed by the current gas hydrate programs, particularly the U.S. and Japanese programs.

The most important “next step” will be the industry-scale production test planned for Alaska. If commercially viable flow rates are achieved, the reservoir could be quickly developed to supply gas for local use. This result would likely lead to a much greater interest and investment by industry. Current budget constraints could delay the test, however.

Environmental and Geohazard Issues

Potential hazards associated with production of natural gas from hydrate include ground subsidence, methane release, slope instability, and water and sand production. Initial studies have indicated that these issues can be mitigated; however, modeling and field validation of mitigation strategies are needed.

An additional area of interest is the opportunity for sequestering carbon dioxide as a subsurface hydrate. ConocoPhillips is investigating the possibility of using the chemical exchange of carbon dioxide for methane in hydrate-bearing reservoirs. In addition to producing natural gas without dissociating the hydrate, this technology would result in stable, long-term sequestration of carbon dioxide.

EMD Technical Sessions and Publications

A Gas Hydrate poster session was presented at the 2009 AAPG annual meeting in Denver. The publication from the 2004 Hedberg Research Conference is in press and will be available in 2010 as AAPG Memoir 89, with the title “Natural Gas Hydrates -- Energy Resource Potential and Associated Geologic Hazards”. The memoir includes an extensive summary of gas hydrate occurrence, and technology.

For a complete version of the above, see the Committee’s Annual Report (May 2013) on the EMD Members Only page (log-in required).

If you would like to learn more about gas hydrates or to receive information on gas hydrates, or on activities of the EMD Gas Hydrates Committee, join the EMD http://emd.aapg.org/emdApplication.pdf . If you are already an EMD Member, see “Members Only Pagehttp://emd.aapg.org/members_only/gashydrates/index.cfm for updates on gas hydrates, for links to technical information on gas hydrates, and for related environmental information that may impact gas hydrates.

For further information on this committee’s activities, go to the Members’ Only Web page or contact:

Arthur H. Johnson, Chair
Phone: (504) 464-6208
Email

AAPG Explorer

May 2010: Safe, clean, sustained production is goal - Hydrates Face Key Test on North Slope
EMD Column by Art Johnson
May 2004: Fire and Ice for the Future EMD: Hydrates, Coal Gas Hold Promise
EMD Column by Charles G. “Chip” Groat
November 2003: MacKenzie Delta Production Tests Positive, Gas Hydrate Research Advances
EMD Column by Art Johnson and Tim Collett