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 have been estimated almost twice the amount of carbon found in all known fossil fuels on Earth; hence, hydrates may represent an important unconventional energy resource.

Global Exploration Activity

Since 1995, gas hydrate energy assessment programs have been initiated in many countries. The most active hydrate drilling programs have been carried out by Japan, United States, Canada, India, South Korea, and China. These programs have advanced gas hydrate production technology to the extent that commercial development is being targeted by the leading development efforts in Japan and China. In 2017, both Japan and China conducted new gas hydrate production tests, with the test in the South China Sea achieving production rates as high as 1.2 million cubic feet of gas per day by simple depressurization.

Other nations with gas hydrate resource evaluation programs include New Zealand, Turkey, Chile, Ireland, Australia, Brazil, Uruguay, Ireland, Germany and Norway.

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 assessment of potential gas hydrate resources in 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. Assessment for the Atlantic margin was completed in 2013 by the U.S. Bureau of Ocean Energy Management, with a mean estimate of 15, 850 Tcf in sandstone reservoirs. 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 numerous 3D seismic data volumes, the USGS estimated undiscovered, technically recoverable gas resources of 85.4 Tcf within gas hydrate.

A global assessment was published by the International Institute for Applied Systems Analysis (IIASA) in 2012, with a median estimate of over 43,000 Tcf in sandstone reservoirs, and this may be considered to be a conservative estimate.

Critical Technology Needs

Current commercialization efforts are constrained by low natural gas prices and the high cost of deepwater operations. In addition, a long-term, industry-scale production test is needed to verify computer models showing high production rates that would continue for many years. Technical areas currently being addressed include sand production and long-term operational issues. New hydrate-specific drilling and production technology is being developed that should address issues of capital and operational expenses.

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.

EMD Publications and Technical Sessions

AAPG Memoir 89 "Natural Gas Hydrates - Energy Resource Potential and Associated Geologic Hazards" provides an overview of the opportunities and issues related to gas hydrate. Poster and oral sessions on gas hydrates are included in selected AAPG conventions. Updates on gas hydrate developments worldwide are included in the Gas Hydrate Committee reports that are usually posted twice each year.

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.