Methane Hydrates
Structure of methane hydrate
Methane Hydrates What are they and what is their future?
Clathrates-derived from latin term for “enclosed in bars”
Methane Hydrate Research and Development Act of 2000
FIGURE 2.2 (a) Gas hydrate recovered from beneath the seafloor offshore Oregon. (b) Burning methane released from gas hydrate as it dissociates.
DOE has been researching Gas Hydrates since 1982 To promote the research, identification, assessment, exploration, and development of methane hydrate resources, and for other purposes. SEC. 5. AUTHORIZATION OF APPROPRIATIONS.
SOURCES: (a) Ocean Drilling Project at Texas A&M University, and photographer John Beck; (b) Dr. Stephen Masutani, University of Hawaii, Hawaii Natural Energy Institute, Ocean Resources Applications Laboratory. Copyright © 2003 Ocean Resources Applications Laboratory. Photographer Liujuan Tang.
There are authorized to be appropriated to the Secretary of Energy Energy to carry out this Act— Act— (1) $5,000,000 for fiscal year 2001; (2) $7,500,000 for fiscal year 2002; (3) $11,000,000 for fiscal year 2003; (4) $12,000,000 for fiscal year 2004; and (5) $12,000,000 for fiscal year 2005. Amounts authorized under this section shall remain available until until expended.
Why study methane hydrates?
As a clean fuel source, natural gas may have the potential to fulfill a disproportionately large fraction of the amount of fossil fuels that the U.S. uses. (Energy Information Administration, 2002). Although the total amount of methane trapped in gas hydrate and the geological processes that lead to concentrated gas hydrate deposits are poorly understood, existing knowledge suggests that gas hydrate represents a potential fossil fuel resource for the future. (e.g., Kvenvolden, Kvenvolden, 1993a; Kvenvolden and Lorenson, Lorenson, 2001; Milkov and Sassen, Sassen, 2002)
A shortfall in natural gas supply from conventional and unconventional sources is expected to occur in about 2020 (Energy Information Administration, 2002).
1
How much methane do hydrates contain?
U.S. Natural Gas Consuption
FIGURE Consumption of natural gas in the United States has been increasing rapidly for the past several decades. SOURCE: Figure courtesy of Ted McCallister, McCallister, Energy Information Administration, U.S. Department of Energy; modified from Energy Information Administration Administration (2002).
Explanation of the stability
Gas hydrates require cold temperatures at moderate pressures or warm temperature but at higher pressure. They are stable at water depths below ~500m, where the temperature and pressure of the ocean moves into the gas hydrate stability field. The sediment host may be 100m thick in shallow water and up to 1000m thick in deep water
How deep do gas hydrates form?
On Earth, gas hydrates can exist within rocks and sediments in a zone where they are thermodynamically stable. This is the Hydrate Stability Zone (HSZ) that extends downwards from the cold seafloor in water depths greater than about 500 m in nonnonpolar, open ocean conditions, and in permafrost regions from some depth within the waterwater-ice permafrost zone (~200 m) to a depth that is determined locally by the rising temperature.
Gas hydrates are known to occur at least to depths of 4400m within the ocean, and theoretically could occur at even greater depths, but usually there is not enough organic matter to generate the methane. The gas hydrate is generally confined to the upper sediment layers, as at depth the geothermal heat from below tends to melts the gas hydrate.
Gas hydrate formation
Sources of Methane Hydrates
SOURCES: Data from Kvenvolden (1999) and Milkov and Sassen (2002), with additions by Alexei V. Milkov. Milkov. Figure courtesy of Alexei V. Milkov, Milkov, BP America, Exploration and Production Technology Group
2
Basins with potential for permafrostpermafrostbearing gas hydrate
Global warming and/or sea level changes possibly associated with Methane hydrates.
Methane is a powerful greenhouse gas. Rising sea levels due to global warming could flood the arctic and melt permafrost layers releasing methane into atmosphere. Climate cooling could lower sea level, decrease pressure on the sea floor, and release methane into the atmosphere.
Take away messages
Methane Hydrates could be a future source of energy or a stepping stone toward other non fossil fuels. Methane Hydrates could have the ability to severely effect global warming and/or sea levels throughout the world
3
Methane Hydrates What are they and what is their future?
Clathrates-derived from latin term for “enclosed in bars”
Methane Hydrate Research and Development Act of 2000
FIGURE 2.2 (a) Gas hydrate recovered from beneath the seafloor offshore Oregon. (b) Burning methane released from gas hydrate as it dissociates.
DOE has been researching Gas Hydrates since 1982 To promote the research, identification, assessment, exploration, and development of methane hydrate resources, and for other purposes. SEC. 5. AUTHORIZATION OF APPROPRIATIONS.
SOURCES: (a) Ocean Drilling Project at Texas A&M University, and photographer John Beck; (b) Dr. Stephen Masutani, University of Hawaii, Hawaii Natural Energy Institute, Ocean Resources Applications Laboratory. Copyright © 2003 Ocean Resources Applications Laboratory. Photographer Liujuan Tang.
There are authorized to be appropriated to the Secretary of Energy Energy to carry out this Act— Act— (1) $5,000,000 for fiscal year 2001; (2) $7,500,000 for fiscal year 2002; (3) $11,000,000 for fiscal year 2003; (4) $12,000,000 for fiscal year 2004; and (5) $12,000,000 for fiscal year 2005. Amounts authorized under this section shall remain available until until expended.
Why study methane hydrates?
As a clean fuel source, natural gas may have the potential to fulfill a disproportionately large fraction of the amount of fossil fuels that the U.S. uses. (Energy Information Administration, 2002). Although the total amount of methane trapped in gas hydrate and the geological processes that lead to concentrated gas hydrate deposits are poorly understood, existing knowledge suggests that gas hydrate represents a potential fossil fuel resource for the future. (e.g., Kvenvolden, Kvenvolden, 1993a; Kvenvolden and Lorenson, Lorenson, 2001; Milkov and Sassen, Sassen, 2002)
A shortfall in natural gas supply from conventional and unconventional sources is expected to occur in about 2020 (Energy Information Administration, 2002).
1
How much methane do hydrates contain?
U.S. Natural Gas Consuption
FIGURE Consumption of natural gas in the United States has been increasing rapidly for the past several decades. SOURCE: Figure courtesy of Ted McCallister, McCallister, Energy Information Administration, U.S. Department of Energy; modified from Energy Information Administration Administration (2002).
Explanation of the stability
Gas hydrates require cold temperatures at moderate pressures or warm temperature but at higher pressure. They are stable at water depths below ~500m, where the temperature and pressure of the ocean moves into the gas hydrate stability field. The sediment host may be 100m thick in shallow water and up to 1000m thick in deep water
How deep do gas hydrates form?
On Earth, gas hydrates can exist within rocks and sediments in a zone where they are thermodynamically stable. This is the Hydrate Stability Zone (HSZ) that extends downwards from the cold seafloor in water depths greater than about 500 m in nonnonpolar, open ocean conditions, and in permafrost regions from some depth within the waterwater-ice permafrost zone (~200 m) to a depth that is determined locally by the rising temperature.
Gas hydrates are known to occur at least to depths of 4400m within the ocean, and theoretically could occur at even greater depths, but usually there is not enough organic matter to generate the methane. The gas hydrate is generally confined to the upper sediment layers, as at depth the geothermal heat from below tends to melts the gas hydrate.
Gas hydrate formation
Sources of Methane Hydrates
SOURCES: Data from Kvenvolden (1999) and Milkov and Sassen (2002), with additions by Alexei V. Milkov. Milkov. Figure courtesy of Alexei V. Milkov, Milkov, BP America, Exploration and Production Technology Group
2
Basins with potential for permafrostpermafrostbearing gas hydrate
Global warming and/or sea level changes possibly associated with Methane hydrates.
Methane is a powerful greenhouse gas. Rising sea levels due to global warming could flood the arctic and melt permafrost layers releasing methane into atmosphere. Climate cooling could lower sea level, decrease pressure on the sea floor, and release methane into the atmosphere.
Take away messages
Methane Hydrates could be a future source of energy or a stepping stone toward other non fossil fuels. Methane Hydrates could have the ability to severely effect global warming and/or sea levels throughout the world
3
