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II Current Situation Regarding Methane Hydrate R&D
II.1 Some key points about the characteristics of methane hydrate
Methane hydrate (known as MH) is a composition of methane and water that is formed under certain
temperature and pressure conditions. The vast abundance of this material is thought to exist in the earth’s
crust and is considered to contribute to the global carbon cycle, to climate change, and also to large-scale
submarine landslides. In the petroleum industry, naturally occurring MH has been known to be a causative
effect of geo-hazards that threaten deep-water marine drilling operations. On the other hand, this substanceis expected to become an alternative hydrocarbon resource that has the capacity to replace conventional
natural gas.
Under ambient conditions (with pressure at 100kPa), MH can begin to form when the temperature falls to−80°C or less. Alternatively, when the pressure approaches 2.6 MPa, MH can begin to form when thetemperature reaches 0°C. In either case, methane should supersaturate the water. The latent heat of MHdissociation is 436kJ/kg. This is a value that is 1.3 times larger than that of ice. It is also larger than theenergy required to heat the same mass of water to a temperature just below boiling point. The implicationsof this are, firstly, that dissociation of MH is endothermic, and, secondly, that a large amount of energy isrequired to exist in order to dissociate MH into its constituent parts of liquid water and vapor methane.
The phase diagram of the methane-water system is shown in Fig.1. The phase equilibrium curve of MH andvapor phase methane vary with solute concentration in the water. When the phase equilibrium curve moves
mainly in the destabilizing direction, the solute is known as a gas hydrate inhibitor (thermodynamicinhibitor). A material with high solubility and low molecular mass is known as an effective gas hydrateinhibitor. A material that delays association of gas hydrate is known as a kinetic inhibitor. A material that isresponsible for the opposite effect (i.e. that accelerates this association) is known as a gas hydrate promotor.
Alcohols (ethanol, glycol, etc.) and salts (Sodium Chloride etc.) are used as inhibitors.

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CH4 concentration (mol/kg)

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Methane hydrate
Water+CH4 gas

Water + resolved CH4
Pressure (MPa)

Taterpeme(ur)
°C



1615

Fresh water
1% NaCl
2% NaCl
3% NaCl
3.5% NaCl

14131211Methane hydratePressure (MPa)

109876543
2

Water+CH4 gas

10012345678910 11 12 13 14 15 16

Temperature (°C)

Fig.1
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Phase diagrams of methane and water system.
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On earth, MH is stable in shallow underground deep water regions (i.e. in water depths greater than 400 mand at several hundreds of meters below the sea floor) or beneath permafrost in Arctic areas or else in highaltitude mountain regions. Naturally occurring MH is found in several forms, such as the filling in porespaces in sandy sediments, as a bulk crystal taking the shape of veins or lenses in clayey sediments, or thefilling of fractures or faults (Fig.2). In order to gain insights into association and dissociation of MH for thepurposes of resource development or in the context of specific environmental and climate conditions,knowledge of the physical properties of the sediment, in particular hydraulic (permeability), thermal (heatcapacity and thermal conductivity), and mechanical (strength and elasticities) are as important as anunderstanding of the properties of MH itself.
Because a sediment containing MH has properties that differ from those containing no MH material, thepresence of MH can be detected by use of those geophysical exploration techniques that utilize both elastic
waves and electromagnetic methods. The most well-known indicator of MH is the Bottom Simulated
Reflector (BSR) by which MH can be detected using seismic exploration. In this case, the lateral extent of
MH can be estimated by this reflection.

Fig.2

Type of occurrence of MH with temperature distribution in sea and ground.

Many attempts have been made to correctly estimate the quantity of MH residing in the earth’s crust.
However, since the estimated value varies with both the process of evaluation and the data used, at thisstage it has not been possible to estimate the degree of precision required. On the other hand, uncertainty
with respect to this evaluation has been shrinking due to the continued accretion of data built up by global
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exploration.
In the early stages of this study, it was estimated that 103〜106 Gt of carbon mass (in 1015〜1018 m3 inmethane gas volume under ambient conditions) was laid down by pressure and temperature conditions [2].
However, the most recent estimations are in the range of 100〜105 Gt in carbon mass (1014〜1017 m3 inmethane gas volume under ambient conditions) [3]. Those estimations only portray the amount of gas inplace, and since they do not portray its recovery rate, they cannot be considered to be a true measure of thevolume of methane that would be available for use as a resource. Incidentally, the total recoverable volumeof natural gas is estimated as being 1014 m3, additionally, world-wide gas consumption annually isestimated to be 4×1012 m3. [US Energy information administration, 2010.]
With regard to the status of this resource on Japanese territory, an estimate of recoverable methane gas wasmade in 1996. It was based on the BSR area known at the time, and was based on certain assumptions
about the vertical distribution of methane (2 m of MH-bearing sediment with 25 % of MH volume fraction
and same gas volume of free gas below BSR) and a hypothetical recovery rate (10 % for MH and 75 % forfree gas). The value derived for the volume of methane gas under ambient conditions was 2.27×1012 m3.
This figure was interpreted in some quarters as being “two-orders of magnitude larger than the annual
domestic gas consumption of Japan (5.4×1010 m3)”; thereby demonstrating that 100 years of domestic gas
consumption could be supplied by MH. However, the value contained a large deal of uncertainty due to thefact that knowledge concerning the occurrence of MH as well as production techniques were at the timerather limited. To put this into perspective, domestic gas consumption in the year 2016 is approximately
1.11×1011 m3. This is almost double that of 1996 and so the “100 years” reference above is highly
exaggerated even if the estimation itself is correct.
During the Phase 1 study using seismic survey data and drilling results, MH21 has made a probabilistic
estimation of the volume of gas in the eastern Nankai Trough. The median value of this estimate was
1.1×1012 m3. Half of this volume exists in an MH-concentrated zone. This zone contains a high saturationof MH that occurs in substantial intervals in sandy sediment.

References[1] Kvebvolden, K.A. (1088): Methane hydrates and global climate, Global Biogeomechemical Cycles,
2(3), 221-229. https://doi.org/10.1029/GB002i003p00221[2] Boswell, R. and Collett, T.S. (2011): Current perspectives on gas hydrate resource, Energy
Environmental Sci.4, doi: 10.1039/C1030EE00293H, pp.10.
[3] M. Satoh, T. Maekawa and Y. Okuda (1996): Estimation of amount of methane and resource of natural
gas hydrates in the world and around Japan, J. Geol. Soc. Japan, Vol. 102, No.11, 959-971.
[4] Research Consortium for Methane Hydrate Resources in Japan (2009): Japan’s Methane Hydrate R&D
Program Phase 1 Comprehensive Report of Research Results, pp. 15,
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http://www.mh21japan.gr.jp/english/wp/wp-content/uploads/ca434ff85adf34a4022f54b2503d86e92.pdf[5] T. Fujii, T. Saeki, T. Kobayashi, T. Inamori, M. Hayashi, O. Takano, T. Takayama, T. Kawasaki, S.
Nagakubo, M. Nakamizu and K. Yokoi (2008): Resource Assessment of Methane Hydrate in the Eastern
Nankai Trough, Japan, OTC19310, 2008 Offshore Technology Conference held in Houston, Texas,U.S.A., 5–8 May 2008.

II.2 Overview of MH21 R & D in Phase 2 and 3, and Recent Overseas R & D Trends
II.2.1 Overview of MH21 R & D in Phase 2 and 3lAfter the distribution chart was announced in 2000, we reviewed seismic survey data acquired fromresearch into areas surrounding Japan. We then published a new BSR distribution chart in 2009.

l

AIST and The University of Tokyo conducted a scientific survey to search for MH in the EasternJapan Sea. (June 2010)l

JOGMEC partnered with ConocoPhillips to carry out a technology test on the North Slope of Alaska.
This test was the first ever field trial of a methane hydrate production methodology whereby CO2 wasexchanged in-situ with methane molecules within a methane hydrate structure. (January - April, 2012)lThe First Offshore Production Test in the World. (Feb 2012 - Aug 2013)
We conducted the world’s first offshore production test of methane hydrate using the depressurization
method off the coasts of the Atsumi and Shima Peninsula in Japan, and produced approximately
120,000 m3 (approximately 20,000 m3/day) of gas during a six-day testing period (January - March2013). The test was closed due to bad weather forecasts and sand production issues. We subsequently
worked on plug and abandonment of boreholes (August 2013).

l

JOGMEC signed a MOU (Memorandum of Understanding) with NETL (National Energy TechnologyLaboratory), an affiliate of DOE (U.S. Department of Energy), concerning collaboration aimed atrealizing a methane hydrate onshore production test. (Nov 2014)l

The Second Offshore Production Test (May 2016 - June 2018)
We conducted the Second Offshore Production Test using the depressurization method in the same
area that the first test was carried out. We produced approximately 40,000 m3 of gas for 12 days onAT1-P3, and approximately 220,000 m3 of gas for 24 days on AT1-P2 continuously (April - July2017). Although sand production problems occurred on AT1-P3, there were no sand-related problemson AT1-P2 and the test was completed. We worked on plug and abandonment of all boreholes (March- June 2018).

l

JOGMEC cooperated with DOE/NETL and drilled a stratigraphic test well in the Prudhoe Bay Unit inAlaska. (December 2018)l
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Recent Overseas R & D Trends

Some countries conduct geological exploration and development of production technology.
After MH21’s offshore production test, China conducted production tests onshore and offshore. India alsobegan studies aimed at realizing offshore production tests. On the other hand, Korea postponed offshore
production test plans. America worked with Japan to conduct a CO2/CH4 exchange method and adepressurization method onshore in Alaska in 2012.
(1) China
China conducted a small scale onshore production test in a permafrost-affected area in Qilianshan,Qinghai in 2009. Following that, China conducted a production test in the Shenhu area from May to July
2017. They implemented the hydraulic fracturing technique to improve the permeability of silty
formations with pore filling-type methane hydrate reserves. In addition, they implemented thedepressurization method. It was announced that the test lasted for 60 days and that the total gas volume
was over 300,000 m3.
China approved the listing of methane hydrate as the country's 173rd mineral variety on November 2017.
In December the same year, media reported that China would establish a national laboratory for methane
hydrates, to be run by China National Offshore Oil Corp. [1]Media reports also stated that a researchcenter base for exploring methane hydrate will be completed in 2021 in Guangzhou, Guangdong.[2] It isreported that China would drill other wells within two years with an aim of beginning commercialization
around 2030[3].
(2) Korea
Korea drilled a survey well in Tsushima Basin in 2010 and obtained a core of filling-type methane
hydrate (UBGH-2). Although there were plans to carry out an offshore test, it appear testing has been
postponed.
(3) Taiwan
A team of Taiwanese and French researchers extracted frozen methane hydrates from the seafloor inJune 2018. It was reported that a Taiwanese-German research team was to embark on a 34-day methane
hydrates exploration mission in October 2018.[4](4) India
Japan cooperated in drilling 42 wells in the area considered to contain pore filling methane hydrate in
the Bay of Bengal in 2015 (NGHP-02).
There was a report in May 2018 that the government had given the nod to the launch of the third stageof the program (NGHP-03), which includes conducting of a pilot test.
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ONGC (Oil and Natural Gas Corporation) set up a dedicated gas hydrate research center at Panvel(Navi Mumbai).[5]JOGMEC is a member of the Advisory Committee and provides advice. Also, the MOU on DGH andJOGMEC's MH research, which has been linked since 2007, is still ongoing.
(5) U.S.A.
In 2012, NETL jointly conducted a CO2/CH4 exchange experiment with ConocoPhillips and Japan(JOGMEC).
GOM2 Expedition-1 Successfully Samples Gas Hydrate Reservoirs in the Deepwater Gulf ofMexico.[6]Exploration including pressure coring is planned during the final stage of the project.

NETL and JOGMEC signed a MOU in November 2014, concerning collaboration aimed atrealizing a methane hydrate onshore production test and together drilled a stratigraphic test well inPrudhoe Bay Unit in Alaska in December 2018.
(6) Germany
Submarine Gas Hydrate Reservoirs (SUGAR) was launched in 2008 and completed in 2018. It wasannounced by local companies participating in the project that there are development examples ofenvironmental monitoring technology as well as development examples of reservoir simulator LARS
(LArge Reservoir Simulator).[7](7) New ZealandAs a member of the Advisory Board for the Gas Hydrate Resources (GHR), JOGMEC researcher
provides advice.
(8) EUThe kick-off meeting in Marine gas hydrate, an indigenous resource of natural gas for Europe(MIGRATE) was held in October 2015. JOGMEC ran a presentation about Japan’s gas hydrate programat the meeting. The organization regularly holds working group meetings and workshops.[8]References[1] Center for Research and Development Strategy, Japan Science and Technology Agency
http://crds.jst.go.jp/dw/20180201/2018020115159/(accessed 2018-11-9)[2] THE SANKEI NEWS. https://www.sankei.com/life/news/180704/lif1807040024-n1.html (accessed2018-11-9)[3] China Energy Net. https://www.china5e.com/news/news-1041873-1.html(accessed 2018-11-9）
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Comprehensive Report of Phase 2 & 3 Research Results[4] Taipei Times. http://www.taipeitimes.com/News/taiwan/archives/2018/10/14/2003702362（accessed2018.11/9）[5] business-standard.
https://www.business-standard.com/article/economy-policy/india-might-hold-world-ssecond-largest-gas-hydrate-reserves-118060501430_1.html(accessed 2018-11-22)[6] NETL website. FIRE IN THE ICE.
https://www.netl.doe.gov/sites/default/files/publication/MHNews_2017_Summer.pdf (accessed2018-11-9）[7] GEOMAR website.
https://www.geomar.de/index.php?id=4&no_cache=1&tx_ttnews%5btt_news%5d=5809&tx_ttnews%5bbackPid%5d=185&L=1 (accessed 2019-2-12)[8] MIGRATE website. https://www.migrate-cost.eu/meetings-workshops (accessed 2018-11-9)

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